The secret to health is in our genes
Twenty years after Watson, Crick and Franklin discovered the structure of DNA in 1953, Gilbert and Sanger introduced the methods of sequencing it. Now we are on the brink of precision medicines, based on our unique DNA profiles, becoming the basis of perhaps most medical treatments.
Precision medicine, as a concept, is not new, but its emergence as a real holistic approach to treating patients will be a powerful tool to solve a variety of health problems, from those as common as high cholesterol to those as severe as cancer.
Not only can it provide us treatment relevant information, it can also inform patients on a variety of health-related topics, from disease risk to medication response to sleep behaviours and even personality traits.
Precision medicine is an evolving approach to healthcare that tailors medical decisions to the specific genetic composition of the individual. It relies heavily on our understanding of our genetic information, its patterns and unique factors that can influence our health.
The key technology driving the development of precision medicine is personal genotyping, which provides large volumes of highly detailed genetic information that can be analysed, probed and understood.
Genotyping, achieved by DNA sequencing, was once a laborious and highly expensive scientific process. The technique has come on by leaps and bounds since the 1970s, from requiring complex laboratory equipment and set-ups to a simple processing chip and sequencing machine.
Personal genotyping is done by sequencing an individual's DNA from saliva, sputum or blood. This allows us to study individual genes or the genome itself, which is the sum of all genetic information obtained.
The technique produces a large volume of data, which provides a detailed map of an individual's genetic makeup. All of us, though we may have many similar features, will generate a genetic map that is highly individualised and unique.
Precision medicine relies on these maps to tailor healthcare decisions based on predispositions and susceptibilities.
The idea of individual genes influencing our responses to treatments or risk factors isn’t new, but having an in-depth view into how exactly these can occur, considering the genetic variation in individuals, is breath-taking.
A classic example of this is the acetylator status of an individual. In other words, how a specific enzyme in the body influences how we process different substances such as medication. Up to 50% of people in the UK may process specific medications differently because of their genetics.
Using genetic information this way, pharmacogenomics (PGx) makes it possible to determine optimal patient treatment that is tailored to each unique genetic profile. However, at present, this information is investigational and should never form the sole basis of treatment.
That’s because pharmacogenomics is only one of several factors, such as age, sex, ethnicity and medical history, that determines a patient's response to medication.
Fascinatingly, PGx is just the tip of the iceberg. DNA testing can identify a huge number of other conditions. These include potential allergies and addictions, and a wide array of ailments and illnesses, from sleep disorder to cardiac problems, diabetes to bone health. It seems the secret of our health is in our genes.
For example, if an individual has a genetic predisposition to a certain type of cancer, personal genotyping can enable healthcare providers to develop a more targeted screening programme that identifies the disease at an early stage, when it is more treatable.
Similarly, personal genotyping can help identify individuals who may be at increased risk of heart disease, enabling healthcare providers to develop more effective prevention and treatment strategies.
Personal genotyping can also enable researchers to identify new genetic targets for drug development. For example, if a particular genetic mutation is found to be associated with a certain type of cancer, researchers can develop drugs that specifically target that mutation, potentially leading to more effective treatments with fewer side effects.
This aspect of precision medicine remains highly experimental at present but is likely to come into clinical practice in the future.
A developing aspect of genotyping allows us to understand our personality and behavioural traits from intrinsic genetic patterns. This is a highly interesting area of evolving research but its use in-practice remains trivial.
Data analysis has attempted to map genetic patterns to personality traits such as openness, extraversion, conscientiousness, agreeableness and even neuroticism, providing a curious view into our own psyches.
However, it is important to note that personality and behaviour are not solely influenced by genetics. They are also strongly determined by life experiences, upbringing, intrinsic neurological and cognitive traits and environmental factors.
Despite the many benefits offered by personal genotyping, there are also some concerns about its use in healthcare. One of the main concerns is the risk that individuals could receive information about their genetic makeup that they may not fully understand or be able to act upon.
For example, if a genetic predisposition to a certain disease is identified, early information, though immensely valuable, may not help in situations where there is no effective way to modify this risk, for example where there are no preventative measures or treatments.
Some genetic patterns, such as harmful mutations in the BRCA1 or BRCA2 'BReast CAncer' genes, are well known to lead to breast and ovarian cancer. In these cases, individuals may be able to significantly alter their risk of contracting the disease based on appropriate medical review and decisions.
That said, this may not be the case for other conditions. For example, Huntington’s Disease, a heritable mutation, is non-modifiable and life-limiting. It is vital for individuals to discuss the benefit and risk of genotyping with a doctor to have a balanced perspective before having the test.
Despite these concerns, the increasing use of genotyping tests will likely continue over coming years. As technology becomes more affordable and accessible, it is extremely likely that genotyping will go hand in hand with conventional medicine and precision medicine.
Though its exact and full implications are unclear to us at present, genotyping ultimately aims to improve the overall health and wellbeing of individuals and populations alike.
Dr Avinash Hari Narayanan MBChB is London Medical Laboratory's Clinical Lead.
