Information

13.3: Medical Uses of Genetic Information - Biology

13.3: Medical Uses of Genetic Information - Biology


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Learning Objectives

Discuss medical uses of genetic information and the potential benefits and risks of this

Personalized Medicine

Watch this video and consider whether you would be interested in knowing details about your own personal disease risk or susceptibility.

A link to an interactive elements can be found at the bottom of this page.

Predicting Disease Risk at the Individual Level

Predicting the risk of disease involves screening currently healthy individuals by genome analysis at the individual level. Intervention with lifestyle changes and drugs can be recommended before disease onset. However, this approach is most applicable when the problem resides within a single gene defect. Such defects only account for approximately 5 percent of diseases in developed countries. Most of the common diseases, such as heart disease, are multi-factored or polygenic, which is a phenotypic characteristic that involves two or more genes, and also involve environmental factors such as diet. In April 2010, scientists at Stanford University published the genome analysis of a healthy individual (Stephen Quake, a scientist at Stanford University, who had his genome sequenced); the analysis predicted his propensity to acquire various diseases. A risk assessment was performed to analyze Quake’s percentage of risk for 55 different medical conditions. A rare genetic mutation was found, which showed him to be at risk for sudden heart attack. He was also predicted to have a 23 percent risk of developing prostate cancer and a 1.4 percent risk of developing Alzheimer’s. The scientists used databases and several publications to analyze the genomic data. Even though genomic sequencing is becoming more affordable and analytical tools are becoming more reliable, ethical issues surrounding genomic analysis at a population level remain to be addressed.

Debate remains over what to do with individual level data as well, such as the data from the genomic analysis of Quake’s DNA. As a result of the study it was recommended that Quake start a regiment of preventative statins; the long-term effects of this study or treatment remain unknown at this stage.

For example, in 2011, the United States Preventative Services Task Force recommended against using the PSA test to screen healthy men for prostate cancer. Their recommendation is based on evidence that screening does not reduce the risk of death from prostate cancer. Prostate cancer often develops very slowly and does not cause problems, while the cancer treatment can have severe side effects. The PCA3 (Figure 1) test is considered to be more accurate, but screening may still result in men who would not have been harmed by the cancer itself suffering side effects from treatment.

What do you think? Should all healthy men be screened for prostate cancer using the PCA3 or PSA test? Should people in general be screened to find out if they have a genetic risk for cancer or other diseases?

There are no right or wrong answers to these questions. While it is true that prostate cancer treatment itself can be harmful, many men would rather be aware that they have cancer so they can monitor the disease and begin treatment if it progresses. And while genetic screening may be useful, it is expensive and may cause needless worry. People with certain risk factors may never develop the disease, and preventative treatments may do more harm than good.


Basic research exploring human and nonhuman genomes is critical to help scientists understand the basic biology underlying disease, as well as to discover new possible therapeutic targets. Although excitement about the potential for gene therapy has grown tremendously since the discovery of CRISPR, the vast majority of work undertaken by scientists funded by NHGRI or other NIH Institutes takes place in the petri dish and in nonhuman organisms such as mice or zebrafish. Researchers rely on genome editing tools as a way to explore the connection between genotype (genes) and phenotype (traits). A typical study might be to model human disease in mice by deleting or editing certain genes that are thought to contribute to the disease. This approach can help researchers determine if specific changes made to the genome contribute to the disease. It can also lead to the creation of "disease models," or laboratory animals that mimic human diseases and can be studied to test new therapies.

In the clinic, there are proposals to use genome editing as a treatment for disease. Many diseases from cancer to asthma have genetic bases. Through the application of genome editing technologies, physicians might eventually be able to prescribe targeted gene therapy to make corrections to patient genomes and prevent, stop, or reverse disease.

Basic research exploring human and nonhuman genomes is critical to help scientists understand the basic biology underlying disease, as well as to discover new possible therapeutic targets. Although excitement about the potential for gene therapy has grown tremendously since the discovery of CRISPR, the vast majority of work undertaken by scientists funded by NHGRI or other NIH Institutes takes place in the petri dish and in nonhuman organisms such as mice or zebrafish. Researchers rely on genome editing tools as a way to explore the connection between genotype (genes) and phenotype (traits). A typical study might be to model human disease in mice by deleting or editing certain genes that are thought to contribute to the disease. This approach can help researchers determine if specific changes made to the genome contribute to the disease. It can also lead to the creation of "disease models," or laboratory animals that mimic human diseases and can be studied to test new therapies.

In the clinic, there are proposals to use genome editing as a treatment for disease. Many diseases from cancer to asthma have genetic bases. Through the application of genome editing technologies, physicians might eventually be able to prescribe targeted gene therapy to make corrections to patient genomes and prevent, stop, or reverse disease.


Transformation

Our editors will review what you’ve submitted and determine whether to revise the article.

Transformation, in biology, one of several processes by which genetic material in the form of “naked” deoxyribonucleic acid ( DNA) is transferred between microbial cells. Its discovery and elucidation constitutes one of the significant cornerstones of molecular genetics. The term also refers to the change in an animal cell invaded by a tumour-inducing virus.

The study of transformation dates to the late 1920s, when an English physician, F. Griffith, discovered that pneumococcal cells ( Streptococcus pneumoniae) could convert from a harmless form to a disease-causing type. He noticed that pneumococci may or may not have a capsular covering. Those cells with a capsule (forming smooth colonies) caused disease in mice those lacking a capsule (and forming rough-surfaced colonies) were harmless. A mixture of living, nonencapsulated cells and heat-killed, capsulated cells, when inoculated into mice, caused disease. Living, encapsulated cells (pathogenic) were created by a “transforming principle” liberated from the dead cells to the living cells. The transformation was heritable. In 1943 a group of investigators at the Rockefeller Institute, New York City, identified that “transforming principle” as DNA.


Under GINA, it is also illegal to harass a person because of his or her genetic information. Harassment can include, for example, making offensive or derogatory remarks about an applicant or employee's genetic information, or about the genetic information of a relative of the applicant or employee. Although the law doesn't prohibit simple teasing, offhand comments, or isolated incidents that are not very serious, harassment is illegal when it is so severe or pervasive that it creates a hostile or offensive work environment or when it results in an adverse employment decision (such as the victim being fired or demoted). The harasser can be the victim's supervisor, a supervisor in another area of the workplace, a co-worker, or someone who is not an employee, such as a client or customer.

Under GINA, it is illegal to fire, demote, harass, or otherwise "retaliate" against an applicant or employee for filing a charge of discrimination, participating in a discrimination proceeding (such as a discrimination investigation or lawsuit), or otherwise opposing discrimination.


The Rise Of Genetic Testing Companies And DNA Data Race

It is said that this is the best of times for direct to consumer (DTC) genetic testing companies, human disease genomics, and the launch of genomic data marketplaces . Due to advances in technology and the availability of cost-effective consumer genotyping kits, massive genomic data sets from human patients and controls are being created from across nations. As a result, it is not only the continued growth in the number of disease genes identified, but it will also advance a deepening of our understanding of the fundamental human genetic architecture and disease states. Moreover, we will also see the commercialization of genomic data.

Along with the identification of human disease genes and states, the ongoing integration of artificial intelligence-driven automation is rapidly advancing novel mechanisms for the analysis and synthesis of a wide variety of disease genomic data types from the fragmented genomic testing market. While, individually and collectively, this is paving the way to the future of personalized medicine, it is still essential to understand and evaluate:

    What are the implications of the growing genomic data and marketplaces?

The Genetic Testing and Research

As seen across nations, DNA test kits for genetic testing are getting popular. As obtaining an individual’s entire genome has become fast and cost-effective, the DNA databases of genetic information are growing by the terabyte. As a result, the rise of direct to consumer (DTC) genetic testing companies and an explosion of data emerging from individual DNA derived from personalized genetic testing brings us both promise and perils.

The central objective of human genetic research is to identify the sequence variations that play a causal role in the development of human disease. The understanding and use of this information is on its way to help generate personalized insights into the biology of human health and disease that can support timely intervention to the clinical translation of disease onset. Now, as artificial intelligence continues to be integrated into medical diagnostic technology, the value of the rapidly growing genetic testing data is increasing enormously. So, the question is:

  • How are we linking the genetic databases and DNA biobanks from across nations?
  • How are we organizing the genomic data?
  • How are we making it user-friendly?
  • How are we defining and determining the credibility and relevance of the growing genetic databases?

Understandably, there are a lot more questions than answers. However, to begin with, there is a need for a way to efficiently sift through the exploding genetic information for the cause of any particular human disease disorder or for clues to how human patients might respond to treatment. Acknowledging this emerging reality of the need to evaluate the emerging troves of genomic data, Risk Group initiated a much-needed discussion on Genomic Search Engine and Genome Interpretation with Dr. Mark Kiel, the Founder and Chief Scientific Officer of Genomenon based in the United States on Risk Roundup .

Disclosure: Risk Group LLC is my company

Dr. Mark Kiel, Founder and Chief Scientific Officer of Genomenon based in the United States participate in Risk Roundup to discuss Diagnostic Genomics: Genomic Search Engines and Genome Interpretation.

Decoding the Individual Genome

Undoubtedly, this is the best of times for human disease genomics. As obtaining and decoding an individual's entire genome has become easy, rapid, and affordable, the genome companies are trying to help bring the value of genetic testing data to personalized medicine, in part by developing a search engine for genomic material. So, what will be the impact of the growing database of genetic information, and where will the search engines take us?

Over the years, remarkable progress has been made in the identification and functional characterization of DNA sequence variants associated with many human diseases. Now, with the arrival of genome-scale mechanisms and approaches for the testing of variant association to the human condition, and their application to increasingly large sample sets, our ability to identify alleles underlying rare and common diseases alike with the help of artificial intelligence-driven automated identification tools has increased substantially. The question is whether we currently have the potential for identifying engineered pathogens that can be used in biowarfare?

The Dawn of Genomic Medicine and Marketplaces

Genomic medicine , an emerging structured approach to human disease diagnosis and management that significantly features genome sequence information, helps scientists, researchers, and medical professionals to determine what genetic code does. Now as researchers link the genetic code to specific human traits or behaviors, this advances the foundation of genomic medicine to a whole new spectrum of disease diagnostic services and personalized new drugs. Furthermore, as human genome data is integrated with the genome data of the microbes in and around the human body, it will likely give us valuable insights into human health and the onset of human diseases, and also help open new markets of personalized genomic medicine, genomic drugs, treatments as well as targeted consumer products and services. That brings us to an important question: how are companies using our genome and the intelligence they get from genetic testing data?

Now, as both private and public organizations begin to collect and create DNA biobanks, how will the formation of genomic biobanks play a role in the creation of genomic marketplaces? How will genomic data marketplaces shift the goals and objectives of genetic testing? It is essential to understand and evaluate:

  • Across nations, who is collecting and developing DNA biobanks? For what purpose and goals?
  • Who is regulating the DNA biobanks? Who is accountable for the DNA biobanks?
  • How secure are the DNA biobanks?
  • How safe is the DNA footprint of any consumer?
  • How much is our genome worth?
  • How can consumers erase their genetic footprint from the internet?

As the effort intensifies to make a functional DNA search engine, the dawn of genomic data marketplaces is a cause of great concern. As millions across nations willingly give their genetic code to for-profit businesses, the question is, do we even know what is at risk ?

The DNA Data race is becoming a rat race. There is no doubt that genetic testing brings opportunities to unlock the value in precision medicine. The hope is that personalized medicine which is targeted and effective will become cheaper. While a plethora of risk factors will likely determine the reality of personalized medicine, the truth of the emerging DNA data race necessitates an understanding of the security risks originating from genetic testing, genomic footprints, genomic databases, genomic medicine, DNA biobanks, and genomic marketplaces.


13.3: Medical Uses of Genetic Information - Biology

Biology courses are designated by BIOL.

is an introduction to the science of Biology, including a discussion of the unity, diversity and evolution of living organisms.

PR: BIOL 1001 is a prerequisite for BIOL 1002 Science 1807 and Science 1808

is a study of the structure, function and reproductive Biology of plants, with emphasis on the vascular plants, and on their relationship to environment and human activities.

PR: BIOL 1001, BIOL 1002, and Chemistry 1001 Science 1807 and Science 1808

Modern Biology and Human Society I

examines various aspects of the human body, and the implications of modern biological research for human beings. Topics include cancer diet and nutrition and associated diseases circulatory disease, immunity, human genetics, biorhythms, new diseases, genetic engineering and reproductive engineering.

UL: cannot be used towards the Minor, Major or Honours programs in Biology

Modern Biology and Human Society II

examines the origins and consequences of the environmental crisis of the 20th century. Topics include the population explosion, energy, material cycles, air and water and land pollution, global food supplies, the fisheries, wildlands, renewable and non-renewable resources, environmental ethics.

UL: cannot be used towards the Minor, Major or Honours programs in Biology

is a study of the invertebrates with emphasis on structure and function, adaptations and life histories. The laboratories will present a broad survey of the major invertebrate groups.

PR: BIOL 1001 and BIOL 1002 Science 1807 and Science 1808

is a study of the vertebrates, with emphasis on structure and function, adaptations and life histories.

PR: BIOL 1002 Science 1807 and Science 1808

is an introduction to Mendelian and molecular genetics. Phenotype and genotype, behaviour of alleles in genetic crosses, chromosome theory of inheritance, genetic linkage, molecular Biology of DNA, RNA and protein, molecular basis of mutation, recombinant DNA, applications of genetic biotechnology.

CO: Chemistry 2440 or Chemistry 2400

PR: Chemistry 2440 or Chemistry 2400, BIOL 1001 and 1002, Chemistry 1010, the former 1011 or 1050/1051 Science 1807 and Science 1808

is a conceptual course introducing the principles of ecology, including theoretical, functional and empirical approaches.

PR: BIOL 1002 Science 1807 and Science 1808

is a course on the fundamentals of microbiology with an emphasis on medical microbiology. The course will include topics such as: host responses to infections, human diseases caused by microorganisms, and the control and exploitation of microorganisms. Entrance is restricted to Nursing students in the Bachelor of Nursing (Collaborative) program.

UL: cannot be used as one of the required courses for the Minor, Major, or Honours in Biology, nor is it acceptable for any of the joint programs between Biology and other disciplines


Nursing and precision medicine

Precision medicine (tailoring medical treatment to each patient’s individual characteristics) has become an important component of nursing practice. Research supports precision medicine as an evolving strategy for disease treatment and prevention that includes attention to an individual’s variability in genes, environment, and lifestyle.

The National Institute of Nursing Research (NINR) supports research across diverse populations and settings to develop more personalized strategies to prevent and manage the adverse symptoms of illness. NINR-supported scientists are actively engaged in implementing clinical applications of genomics to accelerate discoveries that allow healthcare providers and researchers to accurately predict what disease treatment and prevention strategies will work in which groups of people. In contrast to a one-size-fits-all approach, precision medicine challenges nurses to think genetically across specialties and practice settings.


CRISPR used to genetically edit coral

In a proof-of-principle study, Stanford scientists and their colleagues used the CRISPR-Cas9 gene-editing system to modify genes in coral, suggesting that the tool could one day aid conservation efforts.

Acropora millepora coral at the Australian Institute of Marine Science.
Phillip Cleves

Coral reefs on the precipice of collapse may get a conservation boost from the gene-editing tool known as CRISPR, according to researchers at the Stanford University School of Medicine and their collaborators.

The scientists found, for what appears to be the first time, definitive evidence that the CRISPR-Cas9 gene-editing tool could be a potent resource for coral biologists. Phillip Cleves, PhD, a postdoctoral scholar at Stanford, is a geneticist whose efforts to delineate gene function in animals resides squarely within the marine invertebrate realm — namely, corals.

“Up until now, there hasn’t been a way to ask whether a gene whose expression correlates with coral survival actually plays a causative role,” Cleves said. “There’s been no method to modify genes in coral and then ask what the consequences are.”

The study was published online April 23 in the Proceedings of the National Academy of Sciences. Cleves is the lead author. John Pringle, PhD, professor of genetics at Stanford, and Mikhail Matz, PhD, associate professor of integrative biology at the University of Texas-Austin, share senior authorship.

The damage of coral bleaching

In the late 1990s, the ocean’s coral reefs experienced the first big wave of something called coral bleaching, a bleak event in which ocean conditions — most prominently increasing temperatures — kill off or “bleach” parts of the reef, turning once-vibrant colors bland and damaging the entire reef ecosystem.

Researchers collect bundles of egg and sperm released as the coral colony spawns.
Phillip Cleves

Cleves’ work, conducted in collaboration with researchers at UT-Austin and the Australian Institute of Marine Science, sprouted from a conversation at an international coral meeting that aimed to concretely understand the genes behind coral survival. Are there some genes that render corals more resilient to spikes in ocean temperatures? Or perhaps a gene that helps establish new coral colonies? Scientists had hypothesized answers to these questions, but to truly know, Cleves wanted to create a technique that could allow coral biologists to answer such questions more rigorously.

“We want to use CRISPR-Cas9 with the express interest to start understanding what genes are critical to coral biology,” Cleves said.

CRISPR is a fast, effective tool that can be used to target and modify DNA sequences. “Breaking” genes to reveal the effects on the organism is a concept that’s been the linchpin of decades of molecular biology. Now, CRISPR is helping speed up the process in many diverse animal models, but applying it to corals (don’t be fooled — corals are animals, not plants) has proven tricky due in part to their infrequent reproduction. And until Cleves and his collaborators conducted this research, the use of the gene-editing tool had never been reported in corals.

“We hope that future experiments using CRISPR-Cas9 will help us develop a better understanding of basic coral biology that we then can apply to predict — and perhaps ameliorate — what’s going to happen in the future due to a changing climate,” Cleves said.

Spawning by moonlight

Corals pose a bit of a problem when it comes to CRISPR because of their spawning cycles. Most corals, including the Acropora millepora that was the focus of the study, breed only once or twice a year, during October and November in the Great Barrier Reef, cued by the rise of a full moon. During this fleeting window, corals release their sex cells into the ocean. When the eggs and sperm meet, they form zygotes, or fertilized single cells. During the narrow time window before these cells begin to divide, a researcher can introduce CRISPR by injecting a mixture of reagents into these zygotes to induce precise mutations in the coral DNA.

Retrieving the zygotes is quite a logistical challenge, Cleves acknowledged. Fortunately, his collaborators in Australia have the timing down pat they can predict when the moon spawn will occur within a couple of days, allowing them to take coral samples from the reef to gather zygotes for experimentation.

Cleves traveled to Australia to begin experimenting with CRISPR, targeting three coral genes: red fluorescent protein, green fluorescent protein and fibroblast growth factor 1a, a gene that is thought to help regulate new coral colonization.

Using CRISPR, the scientists made a type of genetic tweak that knocked out the genes, rendering them incapable of functioning. In the case of the red and green fluorescent proteins, determining if CRISPR worked would be easy — like seeing lights switch off. Or so they hoped. However, it turns out that there are multiple copies of red and green fluorescent-protein genes. So knocking out one copy didn’t put a stop to the glow altogether.

“Although we are not sure we saw convincing loss of fluorescence, DNA sequencing showed us that we were able to molecularly target both the red and the green fluorescent protein genes,” Cleves said. This showed the researchers that, in one go, CRISPR could successfully alter multiple genes if the two were similar enough — a boon to genetic manipulation, as genes are often duplicated during evolution.

As for the third gene, fibroblast growth factor 1a, which only has one gene copy, post-CRISPR sequencing showed success: in some embryos, the gene was largely mutated, suggesting that CRISPR will work well to modify single-copy coral genes.

Cleves said the ultimate goal is not to engineer a genetically resilient super-coral that could populate the ocean — such a feat is currently implausible and would raise significant ethical questions. “Right now, what we really want to do is figure out the basic mechanisms of how coral works and use that to inform conservation efforts in the future,” he said. “Maybe there are natural gene variants in coral that bolster their ability to survive in warmer waters we’d want to know that.”

‘An all-hands-on-deck moment’

Although the current work is a proof-of-principle study, now Cleves and others are beginning to tinker with genes that are more ecologically pertinent. And he hopes that others do the same.

“I want this paper to provide an early blueprint of the types of genetic manipulations that scientists can start doing with corals,” Cleves said. In the next few years, he hopes to see other groups knocking out coral genes potentially involved in bleaching, skeletal growth or the critical symbiosis with the algae that provide most of the corals’ energy.

Today, as much as 27 percent of the global reef ecosystem has been lost to a combination of climate change and human activities — and Cleves is feeling the urgency.

“This is an all-hands-on-deck moment,” he said. “If we can start classifying what genes are important, then we can get an idea of what we can do to help conservation, or even just to predict what's going to happen in the future. And I think that makes this a really exciting time to be a basic biologist looking at the genetics of coral.”

The research was funded by the Simons Foundation, the National Science Foundation and the Australian Institute of Marine Science.


13.3: Medical Uses of Genetic Information - Biology

The role of public health is to ensure that the basic conditions required for people to be healthy are present. Until recently, public health focused mostly on environmental causes and risk factors for disease, such as infections, cigarette smoking, diet, etc. Since the sequencing of the human genome has been completed, high hopes rest on the potential to prevent the impact of genetic risk factors or susceptibilities to disease. Advances in genetic knowledge and technology could be used to try to prevent disease and improve population health.

The perceived role of genetics in public health is changing, as is the definition of what is a genetic disease. The role of genetics in public health is broadened if we consider all the diseases for which genetics might play a role, either by the presence of a genetic susceptibility for the development of this disease or for response to treatment, or by the presence of protective genetic factors, such as in resistance to infection.

One day, it might be possible to determine for each individual which genetic susceptibilities and protective factors each individual possesses, and act accordingly to prevent the occurrence of disease. In the meantime, the role of genetics in public health is mostly limited to monogenic diseases.

II - Populations targeted by public health genetics interventions

Public health considers the overall health of the population as a group, and not the health of each individual. Since resources for public health interventions are limited, priorities need to be established to determine which interventions will be most beneficial to the population as a whole. These priorities will be based on the characteristics of the disease, such as its prevalence, its severity, and treatment availability, as well as the amount of resources needed for the intervention.

Monogenic diseases are rare. Is it justifiable to implement population-based interventions to identify a few rare cases of a particular genetic disease? There is no single right answer to this question. It depends on the burden these rare cases represent for society, on our ability to act to attenuate this burden, and on the value we place on obtaining an early diagnosis, compared to the complexity of detecting these cases and the amount of resources needed to detect them. For example, newborn screening for phenylketonuria is considered beneficial because it makes it possible for the children identified through screening, who would otherwise have developed severe mental retardation, to develop normally by following a special diet. In the majority of developed countries, all newborns are screened for phenylketonuria to detect a handful of cases, because the impact of treatment on these children’s potential ability to contribute to society is so great. On the other hand, similar newborn screening for Huntington disease is not being considered, because it is a late-onset disease for which there is no treatment and no clear benefit to an early diagnosis. Screening would not change the impact of the disease on the affected individuals or its burden on society.

To improve the yield of a screening program for a genetic disease, one option is to target a population at higher risk of disease, often the families of affected cases. This approach limits the amount of resources needed for screening and increases the yield of screening. It unfortunately is limited by the fact that many new cases of genetic disease occur in individuals with no family history who would not be identified by family-based screening. In some cases, ethnic groups can be the target population of screening programs, when prevalence of the disease in questions is particularly high in that ethnic group. For example, Ashkenaze Jewish populations are screened for Tay-Sachs disease. In programs targeted at specific communities, it is important to ensure that the community is in favor of screening and that it does not become a source of stigmatization for the community.

III - Ethical, legal, and social implications of public health genetic interventions

III - 1. Use of genetic information: confidentiality and discrimination

The issue of confidentiality of genetic information is frequently raised. Genetic information is different from other types of personal information found in a medical chart. First, genetic information does not change over time: the presence of a mutation or a polymorphism in an individual is immutable. Second, genetic information about one individual has implications not only for the individual in question, but also for his/her family members, since the genetic abnormalities are heritable in most cases. In some cases, genetic information is used to confirm a clinical diagnosis, but it is increasingly used to confer a level of risk or susceptibility for the development a specific condition. In that context, it is not surprising that some are worried that information about a specific genetic susceptibility might be used by insurers or employers as a source of discrimination.

III - 2. DNA banks

Genetic research often requires the collection of DNA samples. Many DNA banks were formed from DNA samples collected for specific research projects or from blood samples collected for newborn screening. Once they have served their intended use, what should now be done with these samples? Who do they belong to? Can the researcher use them for other purposes without the consent of those who gave these samples? Can he only do it if he anonymizes the samples first? Or does the researcher need to contact each individual to renew his/her consent? To respect the autonomy of individuals who participated in previous research projects, it would be necessary to contact them again to obtain renewed consent before using their samples for other research projects. On the other hand, these samples are easily accessible and could be used to further scientific knowledge for the benefit of society without major negative impact on the individual who provided the sample, especially if the samples are anonymized. In some cases, the nature of the prospective research will also influence the decision to use or not use samples from a DNA bank. Researchers and ethicists all over the world are faced with these issues. Institutional review boards are assessing each research project based on its specific context, because no consensus has been reached for now on procedures for the use of DNA banks in research.

III - 3. Prenatal diagnosis, assisted reproduction and embryo selection

Assisted reproduction has made it necessary to redefine fundamental concepts, such as paternity and maternity. We now use the terms biological mother, gestational mother (or surrogate mother), and social mother. We also differentiate between biological father and social father. Before DNA tests, paternity was always assumed, but it is now possible to determine with strong certainty whether an individual is or isn’t a given child’s biological father. In the past, maternity was simply attributed to the woman who had given birth to the child. But these days, it is possible for a woman to have an embryo conceived with her own eggs carried to term by another woman. The first woman is then the biological mother, and the second the gestational mother. The social mother will be the one acting as a parent to the child in question.

Assisted reproduction is not reserved for infertile couples anymore, but is also used by couple who want to ensure that their child will be born without a specific hereditary disease, or even to make sure that their child will be a matched donor for an older sibling in need of a bone marrow transplant. Genetic tests performed on embryos make it possible to select only embryos that fit certain criteria. For now, this technology is mostly used to avoid the birth of children with severe hereditary childhood diseases, but it is feared that it opens the door to embryo selection based on other criteria, such as physical appearance or intellectual ability.

When a pregnant woman is offered the possibility of undergoing prenatal diagnosis for genetic diseases through amniocentesis or chorionic villous sampling, it implies that selective abortion is an option they will consider if the fetus is indeed affected with a genetic disease. For some, this option is unacceptable for ethical, moral, and/or religious reasons. It raises the question of the legal status of the embryo, the definition of human life and of a human being.

IV - Examples of the role of public health in genetics

There are already many examples of the role of public health in genetics. Better known examples deal with reproductive technologies (prenatal screening, carrier screening) and newborn screening. More recent examples in the adult setting concern genetic susceptibility screening and pharmacogenetics.

IV - 1. Folic acid and neural tube defects

Neural tube defects (NTD) account for an important part of birth defect-related infantile mortality and morbidity. Their incidence tends to be decreasing over time (secular trend). During the 1980s, studies have shown a decrease in the recurrence of NTD in subsequent pregnancies with the use of folic acid for women having already had a child with a NTD. Since then, studies done in women with no family history of NTD have also shown lower incidence rates of children born with NTD in women who took folic acid supplements. Even though the way in which folic acid acts to prevent NTD has not been elucidated, these observed findings have led to the hypothesis that folic acid supplementation would be beneficial to all women planning a pregnancy, to prevent the birth of a child with a NTD.

Because the neural tube closes during the fourth week of gestation, it is recommended to start folic acid supplementation before conception. The minimal dose needed to obtain an effect has not been established, but the usually recommended daily dose is 400 micrograms in women with no specific risk factor, and should be started at least 3 months before conception. However, supplementation often does not occur, either because women are not aware of the benefits of folic acid supplementation or because pregnancy was not planned.

To address this problem, some countries have decided to add folic acid to the food supply, most often in flour. This type of public health intervention has occurred in the past to prevent other diseases: iodized salt to prevent goiter, and vitamin D in milk to prevent rickets.

Folic acid fortification of flour has not been done without controversy. Some fear that folic acid fortification will mask vitamin B12 deficiency and delay its diagnosis. Others worry about long-term effects of a folic acid-fortified diet or about potential interactions between folic acid and prescribed drugs. No study has shown that this fortification strategy would be sufficient to reduce the incidence of NTD in the population. In spite of all that, many professional organizations have declared themselves in favor of fortification. Folic acid fortification has been established at the end of the 1990s in many developed countries, most often in flour. Studies done since fortification seem to show a significant reduction in the incidence of NTD in the population, even when accounting for the secular trend.

IV - 2. Newborn screening

for phenylketonuria (PKU) is the first example of population-based genetic screening. It was put in place in the U.S.A. in the early 1960s, thanks to the development by Dr Robert Guthrie of a technique allowing the measurement of blood phenylalanine levels using blood samples collected on filter paper. Samples collected in this way are easy to store and ship, and can be preserved for extended periods of time. The technique itself is cheap and easy to perform. These characteristics have made it possible to develop large-scale screening programs. Newborn screening for PKU is now performed by the state in most developed countries.

In the wake of newborn screening tests, a screening “system” was developed. Today, a newborn screening system includes sample collection and shipment to screening facilities, performance of the screening test in the laboratory, diffusion of test results to parents and referring physicians, and, for newborns with abnormal results, rapid access to specialized evaluation and appropriate care. In parallel, severe quality control criteria have been established and voluntary laboratory quality control programs are managed by government agencies, such as the Center for Disease Control in the U.S.A.

Since the 1960s, other diseases have been added to newborn screening panels. The list varies by region, but it almost always includes congenital hypothyroidism, and often includes galactosemia, tyrosinemia, sickle cell anemia, and/or congenital adrenal hyperplasia. For all these diseases, a dietary-based or drug-based treatment is available to prevent the effects of the disease or attempt to control their progression, and it seems preferable to start these treatments as early as possible.

In the last few years, a new technology, tandem mass spectrometry (MS/MS), makes it possible to detect over 30 metabolic diseases during the newborn period, such as aminoacidemias, organic acidurias, and urea cycle defects, to name a few. The use of this technology for newborn screening is controversial for several reasons. Among the diseases that can be detected with MS/MS, some have a poorly defined natural history. In those cases, it is difficult to predict what will happen to the affected newborn and the impact that early diagnosis and treatment could have. It is not clear whether dietary treatment will be as effective in all cases. However, newborn screening using MS/MS would make it possible to learn more about these diseases, which might otherwise go undetected (even if symptomatic). In the U.S.A., advocacy groups formed by parents of children with diseases detectable with MS/MS are lobbying for the addition of this technology to state-run newborn screening programs. Those opposed to using MS/MS for newborn screening argue that there is no evidence that early diagnosis and treatment of these diseases will improve their natural course, which goes against the criteria largely used to decide whether or not to add new diseases to newborn screening programs. They stress that the availability of the technology and its capacity to detect disease does not mean that the information it provides is valuable for newborns.

Newborn screening for cystic fibrosis is also currently debated. Newborn screening programs for cystic fibrosis already exist in many regions of the world: in Wisconsin and Colorado (USA), in Brittany (France), and some regions of the United Kingdom and Australia. Some studies have shown that children identified through newborn screening achieve better nutritional status and/or better respiratory function than those diagnosed through symptoms, but these differences are mild and tend to disappear over time. The main newborn screening criteria, as defined by the World Health Organization, state that an effective treatment must be available and that the early application of that treatment must improve the health outcome of the child. Even though long term impact of early diagnosis of cystic fibrosis on the evolution of disease has not been irrevocably established, some argue that early diagnosis is of benefit to parents because it avoids unnecessary anxiety related to delayed diagnosis in a symptomatic child, and enables them to make informed reproductive decisions for future pregnancies. The benefit is not for the child itself, but for parents, and it is not related to the early onset of effective treatment. According to this argument, it would be justifiable to screen for genetic conditions with no known effective treatment but whose early diagnosis would be of value to the parents. In the case of cystic fibrosis, early diagnosis can possibly be of value to the child, but this would not be the case for other diseases for which newborn screening has been advocated, such as Duchenne muscular dystrophy and Fragile X syndrome.

IV - 3. Carrier screening in the context of reproductive decisions

The first carrier-screening program for recessive diseases was developed in the Ashkenazi Jewish communities in New York and Washington, D.C., in the U.S.A. With the support of the community and religious officials, a carrier-screening program for Tay-Sachs disease was established in the early 1970s, shortly after the discovery of the enzyme whose deficiency is the cause of the disease. Tay-Sachs disease then had a relatively high prevalence in the Ashkenazi Jewish community. This disease causes progressive neurodegeneration starting in the first year of life and inevitably leading to the child’s death, usually by four years of age. Both the community members and the health professionals involved agreed that this disease is so severe that it would be preferable to take measures to avoid the birth of affected children. The screening strategy has been adapted to the needs and realities of the different communities: in orthodox communities where selective abortion was not acceptable, premarital screening is performed and results are taken into account in the rabbi’s decision to bless the marriage or not, which has been deemed acceptable by the community. Carrier screening programs for Tay-Sachs disease now exist in Ashkenazi Jewish communities around the world. Thanks to these programs, the incidence of the disease has decreased by over 90% in these communities. In the wake of this success, other diseases with relatively high prevalence in Ashkenazi Jewish communities have been added to carrier screening panels, such as Canavan disease and Gaucher disease, to name a few.

In response to the success of Tay-Sachs carrier screening in Ashkenazi Jewish communities, similar programs have been developed in other communities where an autosomal recessive disease was highly prevalent in children, such as carrier screening for beta-thalassemia in Cyprus and Sardinia. These programs have also led to drastic reductions in disease prevalence in these communities. Carrier screening programs for sickle cell anemia in African Americans in the U.S.A. in the 1970s have not had the same success, partly because the distinction between being a healthy carrier and having the disease was not made clear. This had led to discrimination against carriers.

Recently, the American College of Obstetrics and Gynecology has recommended that all pregnant women be offered carrier screening for cystic fibrosis. This recommendation has been questioned by some, because screening is routinely offered when pregnancy is already ongoing and because cystic fibrosis is not considered as severe as Tay-Sachs disease.

IV - 4. Prenatal screening for aneuploidy and neural tube defects

For a detailed discussion of what is available in prenatal diagnosis, see “Prenatal Diagnosis” section.

In terms of population health, it is of note that prenatal screening for chromosomal abnormalities and neural tube defects is offered to pregnant women in many countries. These screening programs may be targeted at women with specific risk factors (i.e. according to maternal age), or to all pregnant women. In most cases, newborns with chromosomal abnormalities or neural tube defect are born of mothers with no specific risk factors. A screening test done during pregnancy can identify those women at higher risk of carrying a fetus with one of these conditions. This blood test, which measures a combination of serum and/or ultrasound markers, is not a diagnostic test: like all screening tests, it tends to be highly sensitive, but not necessarily very specific. The role of a screening test is to detect all cases of the targeted condition, at the expense of a certain amount of false positive results. For prenatal screening, the test result is usually given as the probability that the fetus is affected, and the result is considered “positive” when this probability is higher than a specific threshold, usually between 1/400 and 1/200. Since this threshold is relatively low, there is inevitably a high proportion of false positive results, i.e. pregnancies with test results above the threshold and considered at high risk of having an affected fetus, but whose fetus is actually not affected. In a screening context, we tolerate a certain amount of false positive results that will have to undergo definitive diagnostic testing through amniocentesis and incur the associated risk of miscarriage. It is the price to pay to reduce as much as possible the rate of false negative results, i.e. a result placing the risk below the threshold when the fetus is actually affected. These screening programs have been developed to give women the possibility of terminating the pregnancy if the fetus is found to be affected. In general, this option is considered acceptable because most people consider these conditions to be severe enough and prevalent enough to justify a population-based screening program. Those who consider termination to be unacceptable can select out of the screening process.

IV - 5. Screening for genetic susceptibilities in adults

Since the sequencing of the human genome, advances in genetic knowledge has led us to consider the potential use of genetic information to assess individual susceptibilty to disease. Although this is not widely possible yet, there are some examples of the use of genetic tests for that purpose. These examples raise questions about the real clinical utility of that type of information at the individual level.

Hereditary hemochromatosis is an autosomal recessive disease. Individuals who suffer from this disease can develop cirrhosis of the liver, diabetes, and cardiomyopathy. Symptoms are caused by a defect in iron metabolism, which leads to iron deposition in tissues. Two main mutations in the hemochromatosis gene have been identified, C282Y and H63D. Most cases are C282Y homozygotes. Regular phlebotomies reduce iron deposition and can help prevent or reduce symptoms. For that reason, hemochromatosis is considered an ideal target for population-based screening. The use of a genetic test as a screening test for hereditary hemochromatosis is justified if we assume that penetrance of the disease is high, i.e. that most C282Y homozygotes will develop symptoms of hemochromatosis in their lifetime if untreated, and that they would benefit from early diagnosis and preventive treatment. Unfortunately, penetrance seems lower than previously thought: it seems that only a minority of C282Y homozygotes actually develop symptoms of hemochromatosis in their lifetime. The value of population-based genetic screening for hemochromatosis is being questioned. It is currently recommended to use transferrin saturation level as a screening test for hemochromatosis. This is a biochemical index of iron overload, and is closer to the phenotype of hemochromatosis than the genetic test.

Factor V Leiden (FVL) is a variant of factor V, a coagulation factor. This variant is associated with an increased risk of thrombosis. Even though the presence of FVL in an individual with a history of thrombosis can help explain the cause of the thrombosis, it does not usually change immediate treatment or long-term management of that individual, who will be treated as any other individual with a personal history of thrombosis. On the other hand, not all individuals who have FVL will develop thrombosis. It is difficult to justify population-based screening for FVL, and especially to submit them to long-term prophylactic anticoagulation treatment, which is associated with significant risks of bleeding. Other factors also influence the risk of thrombosis in these individuals, such as smoking and hormonal therapy, and make it difficult to predict risk of thrombosis on an individual basis.

As our knowledge of gene-environment interactions increases, it might be possible to improve our assessment of individual disease susceptibility by using predictive models based on combinations of genetic and environmental risk factors. For now, the impact of genetic susceptibility is difficult to assess, especially on an individual basis.

IV - 6. Pharmacogenetics and ecogenetics

Pharmacogenetics is a field of genetics focusing on the role of genetics in individual variability of drug response and side effect occurrence. If we can predict the pharmacologic response of a given individual to a specific drug based on the presence or absence of a given genetic polymorphism, we could adjust dosage accordingly. Most genetic polymorphism studied until now have been in genes involved in the metabolism or elimination of drugs. It is thought that these polymorphisms might accelerate or slow drug metabolism or drug elimination.

Ecogenetics is similar to pharmacogenetics, but focuses on the role of genetics in explaining the individual variability of response to environmental factors (carcinogens, pesticides, food products, industria pollutants, etc.), instead of response to drugs. This information could be used in the workplace to identify individual workers at risk of developing complications related to occupational exposure to specifc agents. There is the danger that this might be used to discriminate against those with genetic susceptibility to develop complications, who might be refused employment. On the other hand, workers at low-risk of complications might be exposed to higher levels of the agent in question if it gives them a false sense of security and protective measures are lessened, which would paradoxically put them at higher risk of actually developing complications.

IV - 7. Personalized Health Care and Genetic Information

Some hope that a better understanding of genetic variability will help adapt treatments on the basis of an individual’s genetic characteristics and the risks and benefits of the many treatment options available for that individual. This will depend on how fast knowledge will grow in pharmacogenetics and ecogenetics. In some cases, the treatment will be the same, but the dose, duration or timing of treatment will be different according to the individual’s genotype. In other cases, treatment itself will be tailored for specific individual genotypes, targeting specific genetic differences. Over time, a better understanding of genetic susceptibilities might help target preventive measures to individuals who can potentially benefit from them the most. But, in the context of increasing health care costs, the use of resources to personalize health care based on genetic characteristics will have to be balanced against its benefits.

Conclusion

The impact of genetics in public health is still limited, but is expected to grow in the near future, as genetic knowledge rapidly increases. Current examples of the use of genetics in public health can serve as lessons for the future.


How is genomics used in medicine?

  • Diagnosis — for example, where the cause of a range of symptoms cannot be pinpointed by any other means.
  • Prenatal tests that take place during pregnancy — either to screen (just in case something is wrong with the baby) or where there is already a family history. It helps the parents to make informed choices and plans for the future.
  • Where there is a family history of serious genetic disorders, it can tell prospective parents whether or not they are a carrier and if they can pass it on to their children. It can also tell someone if they are likely to develop the inherited condition later in life, even if they don't yet have any symptoms.
  • To assess risk — someone's genetic makeup can show their susceptibility to suffer certain illnesses, like heart disease, stroke, and cancer. Perhaps they're likely to have high cholesterol levels or to suffer problems with their veins. Possessing this knowledge means they can manage the risk through medicines, medical intervention, or making positive lifestyle changes.

The ways in which genomic medicine is making a difference

This greater understanding of the links between biology and disease brings benefits on several levels.

  • Personal — each patient has medicines, treatment, and a health care plan tailored to them and their individual needs and risks. As an example, take the treatment of colorectal cancers. Some people with a particular gene mutation have better survival rates when treated with a non-steroidal anti-inflammatory, such as aspirin, than those without this mutation. 1
  • Doctors — access to genomic information helps with diagnosis, managing treatments, and spotting symptoms across a wider cohort of patients. There have been a few cases where cerebral palsy diagnosis has been re-evaluated in the light of genetic testing, revealing a new diagnosis and, as a result, a new, effective treatment plan. 2
  • National level — developing strategies to care for rising trends and particular communities and programmes like newborn screening in the U.S., which examines for between 29 and 50 severe but treatable conditions. 3
  • On a world-wide scale — projects like the Online Mendelian Inheritance in Man 4 , an open-access database of all known human genetic conditions. This kind of approach means that the parents of children with rare syndromes are more likely to get the answers and the support they need.

What can I expect and what is genetic counselling?

There are a number of types of service provider. In the U.K., for example, the National Health Service employs 90 consultant clinical geneticists at 25 centres. They're supported by hundreds of specifically trained staff. 5 Referral is usually through a general practitioner (GP or family doctor) and is available to those who are worried about a serious genetic family condition or a family tendency towards developing cancer, or to parents of a child with learning difficulties and other developmental problems looking for an expert assessment.

In places where a public service isn't available, or for those who choose to seek private health care treatment, check to make sure that the clinic you're using has the necessary registration (for example, in the UK this is through the Care Quality Commission, also known as the CQC 6 ) and the lab is also correctly accredited.

Whatever the setting, the appointment might take some time and you may need to bring other members of your family with you. Your family and medical history will be mapped and explored, and it's likely you'll have a medical examination too. Finding out that there may be a life-changing or life-limiting condition in your future is a serious and, for some, traumatic experience. Alongside counselling, you may be offered tests (including blood tests)—with the option of having these done on the day or, if you need time to think about the possible implications, to come back at a later date.

Results can take weeks or even months to return (depending on the rarity of the genetic abnormality and how easy it is to find) but pre-natal test results will be returned much sooner.

Aftercare then depends on the results and the nature of what you're being tested for. Some people will be referred back to their family doctor along with full details, or they may go on to receive treatment at a specialist unit. Those who are aren't showing symptoms will be given support and advice about lifestyle changes, in order to minimise their risk, and advice about managing their potential condition in the future.

There are also a number of private companies who offer genetic testing by mail. It involves having a cheek swab or a blood sample taken at a local clinic. It's then sent off to the laboratory. The kinds of things tested for include genetic risk for diabetes and heart conditions, as well as ancestry information. Some companies deliver more of a service than others, with counsellors or other health professionals on hand to help. Convenient (but not necessarily cheap), it must be remembered that this is genetic testing without the usual level of holistic support found in established clinics.

The future

The broad area known as genomic medicine is evolving — the study of genetic mutation pathways and their variations is particularly exciting. But what does this mean for people on a practical level? As discussed earlier, there are some hereditary diseases that are difficult to diagnose simply because of the wide range of genes involved.

Scientists are working towards finding a chemical or genetic bottleneck for conditions like these. The ability to switch off a vital reaction along the pathway from genetic trigger to hay fever, dust allergy, or asthma, for example, would aid diagnosis and treatment, and possibly whether or not these traits need cause misery for the next generation. 7

Epigenetics

The emerging field of epigenetics takes this idea one step further. It's based on the concept that each gene has its own chemical tag that tells the gene how to act. It is possible to turn the gene off (make it dormant) or turn it on (make it active) according to its chemical tag. In this way, the genetic code remains the same but the way in which it is expressed changes. 8

This is a very exciting development. If things such as what we eat and drink and how much we sleep affect the way our genetic code manifests itself, what are the implications for disease and ageing? The times when genes are switched from a healthy, normal state into one that causes disease and the end of life?

These chemical modifications can also be passed on to the next generation, creating a more variable level to genetic inheritance. In other words, your lifestyle choices can affect your child’s health in a negative or positive way on a basic, biological level.

Time to think

Advances in genomic medicine mean that more diseases, both rare and more common, can be diagnosed and treated than ever before. But there are a few things to consider:

  • Is our destiny in our genes? Depending on the genetic flaw, disease isn't always the outcome, and symptoms may delay or not manifest themselves at all. What checks are in place to guard against unfair discrimination and prejudice?
  • With pre-implantation testing available to tell everything from the sex of an embryo through to specific genetic mutations, who makes the decision about which children get a chance at life?
  • To what extent can doctors rely on genetic medicine for diagnosis and therapy? Could it lead to over-confidence, misdiagnosis or missed symptoms?
  • How do governments and other policy-making authorities use information gathered by international genomic projects?

By understanding that which is already written down in our genetic code, we can predict and manage what happens in the future. New advances in genomic medicine create an environment where we can make sound health care plans, seek advice, and get treatment in the vital early stages of disease.

On a personal level, this doesn't stop at us — the principles behind epigenetics suggest that our everyday habits – what we eat and whether we smoke – can have a positive or negative effect on our grandchildren's biology, meaning that our genetic legacy is also well worth taking care of. At Aetna International, we may cover gene testing on a case by case basis, for example if an oncologist needs to determine the most suitable treatment for a member with cancer.

For more information on international health insurance and accessing the best health care for you and your family, contact one of Aetna International's expert sales consultants today.

If you’re an employer or broker looking for international Private Medical insurance for clients or staff, you can call us to discuss your needs. Get the right telephone number for your area, here.


Watch the video: Κέντρο Ερευνών Μοριακής Ιατρικής (May 2022).