Somatic genetic variants: A genomic revolution hiding inside our cells

Source: The post is based on the article “Somatic genetic variants: A genomic revolution hiding inside our cells”  published in The Hindu on 28th August 2023

What is the News?

Scientists have been aware of Somatic Genetic Variations for quite some time but there has been a recent surge in the volume of data related to these variations.

What are Somatic Cells?

Somatic cells are the cells in the body other than sperm and egg cells (which are called germ cells). 

In humans, somatic cells are diploid, meaning they contain two sets of chromosomes, one inherited from each parent. 

DNA mutations in somatic cells can affect an individual, but they cannot be passed on to their offspring.

What is Somatic Genetic Mutations?

Humans have 23 pairs of chromosomes, one from each parent, which carry our genetic information or blueprint.

After fertilization, a single cell with 23 chromosomes begins dividing, ultimately creating nearly a trillion cells in the human body.

During cell division, DNA is accurately copied thanks to error-correcting proteins, but there’s still a very low error rate (0.64-0.78 mutations per billion base pairs per division).

An error that occurs in the DNA after birth but during development is called a Somatic Genetic Mutation. 

This occurrence of mutation is driven by the repeated ‘copy-pasting’ of the genome – which means there will be more somatic genetic mutations the older an individual is and the higher the turnover of the tissue.Turnover is the replacement of old cells with new ones.

Sometimes, a somatic genetic mutation can render a cell fitter than others, which lead to the formation of tumours.These mutations are called driver mutations.

What is the importance of Somatic genetic variants?

Cancer signatures: Somatic genetic variants play an important role in the development of cancers.We now know that somatic changes can cause a cancer to develop and that cancers can accelerate the development of somatic changes.So they can help with early detection, diagnosis, and prognosis.

Development of Genetic Diseases: Many genetic conditions arise from somatic genetic variants. Obviously, these conditions are not inherited from either parent but are due to new genetic variations that have arisen during development. So the severity and distribution of the disease depends on how early or late during development the corresponding mutation occurred.

Beneficial in some cases: In some instances, somatic changes can be beneficial in a genetic disease – by changing a deleterious change to a normal one, a phenomenon known as revertant mosaicism. 

– For example, around 10% of cases of Wiskott-Aldrich syndrome, a rare genetic immuno- deficiency, have been found to have revertant mosaicism, as a result alleviating the severity of the disease in many individuals.

What is Somatic Mosaicism across Human Tissues(SMaHT) Network?

Launched by: U.S. National Institutes of Health 

Aim: To discover somatic variants, develop tools for study, and improve analysis for biological and clinical insights.

Investment: The U.S. government has invested $140 million to study somatic variants in post-mortem samples.