‘Human identity through genome’ – The Hindu

Hyderabad


Kumarasamy Thangaraj is synonymous with Indian population studies, origin and genetics analysis. CSIR-Centre for Cellular & Molecular Biology (CCMB)’s chief scientist has just taken over as the director of Centre for DNA Fingerprinting and Diagnostics (CDFD) funded by the Department of Biotechnology (DBT). In this interview, the 57-year-old, hailing from Tamil Nadu, dwells on his plans and pioneering genetic studies. Excerpts:

Congratulations! This institute is something close to your heart, isn’t it?

Thank You! Yes, it is close to my field and I have been familiar with this institute from its inception as it originated from CCMB. Along with CDFD founder Dr. Lalji Singh, I made some contributions in its infant stage, including the logo! After it moved out of CCMB I was not keeping a regular touch but am very much familiar with the work here. I am confident of adding value to this field.

How far have we come on genetic diagnostics and counselling over the years?

About 70% of the cases coming here are being successfully diagnosed and solved through biochemical, chromosomal and DNA based diagnostics. May be, we can come closer to 100% success after we sequence the whole human genome. We should be in a position to resolve any diagnostic/human identification case, it is the level I visualise for CDFD.

What happened to the genome project?

We could not participate with the international team earlier, but now we have the capability, infrastructure and funds. DBT has recently provided funding for sequencing of 10,000 Indian genomes covering different castes and tribes. Twenty scientific organisations are involved in this project, including CCMB and CDFD. We are doing the groundwork for sample collection. It will catalogue genomic variations of different ethnic populations in three years. These would be reference sequences and will be made accessible for all the researchers in India.

Has DNA diagnostics helped people take informed decisions through screening and counselling?

It is now accessible as it has become affordable. Once we sequence a large number of genomes, we can identify the genetic cause for more number of diseases – common or rare.

Based on our previous study, we predicted that at least 1/3 of Indian populations are susceptible for population-specific recessive disease, due to the practice of endogamy (marriage within caste and community). In this case, both parents would carry heterozygous mutation (one normal and another chromosome with mutation) and will have 25% of chance of transmitting the abnormal chromosome by both parents to the next generation, hence homozygous mutation and disease.

Genetic analysis will help us identify the recessive mutation causing the disease. Mutations responsible for causing recessive disease can be screened at population level with very low expenditure and appropriate counselling can be provided.

How do we deal once we identify the recessive mutation?

Gene therapy has not picked up and there are ethical/regulatory issues with other modern technologies on ‘corrections’ of mutations. The best way is to ‘avoid’ through genetic testing, appropriate counselling and pre-natal diagnosis.

Pre-marital counselling is another method and was taken up successfully by the Jews. They managed to eliminate two diseases over a period of time. We too can do the same keeping an eye on the foetus as there is 1/4th of the chance of the child having the disease or avoiding the marriage itself. If practised for a few generations, mutations can be eliminated from the population.

Has the last word been said about the origin of Indians?

Our earlier study had shown that the Andamanese are the first migrants out-of-Africa through the southern coast about 65,000 years ago and continue to be the purest. During this migration, some people settled in the southern part of India, whom we call Ancestral South Indians (ASI). Second wave of migration brought people to north, whom we call as Ancestral North Indians (ANI). These two groups (ASI & ANI) have ‘admixed’ between 2,000 and 4,000 years before present, irrespective of caste or community. We can easily correlate the range of skin colour we have in India, unlike say Europeans or Africans where a particular skin colour is prominent in the majority. Great Andamanese are mixed with other populations having lighter skin colour with curly hair.

What is the CDFD role in COVID-19 control? Do you think scientific research will receive a fillip now?

We have tested more than 1.54 lakh samples so far and also involved in genome sequencing of the virus. I must thank our scientists, PhD students and other staff for their efforts. Basic science does not give immediate results and requires time. But, the satisfaction of doing benefit to society through science cannot be matched. Although the number of students who come to biological research is reducing, I am sure the pandemic and issues like health and environment will make the young students to think and take biological research as their career path. Interest in science should be inculcated from the school level.

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