What is clinical exome sequencing? You may have heard of whole genome sequencing, which has revolutionized the field of genetic research. However, clinical exome sequencing (CE) has some important advantages over whole genome sequencing. The main advantage of clinical testing is that it can identify and eliminate all or part of a DNA sequence, irrespective of its location on the chromosomes. The technology is very useful for analyzing DNA samples from living patients, enabling researchers to establish the relationship between disease genes and symptoms in individuals. For this reason, many medical conditions, such as cancers, are routinely tested using exome sequencing.
How does clinical exome sequencing work? The technology basically involves DNA extraction from cellular samples and then sequencing the DNA along with complementary DNA, resulting in a short piece of DNA, which can be identified using an experimental template provided by the researcher. The template can be matched using molecular information at a specific site. If the matching is found, the researcher reports the results using a handheld DNA probe, which enables the subsequent analysis of the long inserted DNA sequence.
The other benefit of clinical exome sequencing is the ability to determine whether or not particular traits or characteristics can be passed on to offspring. It has long been thought that diseases like cancer and diabetes could be passed down through genetics. Through exome sequencing, a doctor can look at a patient’s genome and see if she does, in fact, have a mutation in her genes that could cause those diseases. It has also been established that certain diseases like Alzheimer’s disease are caused by a mutation in the brain’s cells.
Another important benefit of clinical exome sequencing is the ability to determine the relationship between a person’s DNA and their disease. After sequences from an exonuclease cell are compared with those from a control sample, the researcher can tell how much of the disease lies within the cells of the individual, versus the genes they inherited from their parents. Using this knowledge, the next-generation sequencing of human genes can be used to find out what DNA variations account for why a person possesses a particular symptom, while another person does not.
In the case of Alzheimer’s disease, for instance, research has found that patients carry a mafb gene on their X chromosome. However, when this mafb gene malfunctions, it produces a protein that prevents the nerve cells from making the neurotransmitter acetylcholine. When a person’s body needs acetylcholine to communicate with the brain, it releases acetyl cholinesterase, which causes the neurons to deteriorate over time. Eventually, the neurons will die and the brain will eventually go into a permanent coma. Because of this, researchers have been able to use clinical exome sequencing to determine if a patient has a mutation in their genes that may be responsible for this disorder. This is significant because it means that the medication, if any, that a person needs will have to include a gene therapy component, since the drug needs to get to the brain to function normally in order for it to work.
