Posted: Sun Jun 18 2006, 00:00 hrs
Eight years ago, an obscure village, nestling among hills and surrounded by paddy fields near Madurai was cause for much excitement for a project team from the US. It was on a mission to trace human roots to a single origin. An unremarkable farmer’s son and the placid Jyotimanickam village shot into the limelight when renowned population geneticist, Spencer Wells, landed on its dusty square.
Wells had hoped to prove that a few descendants of the first humans from Africa, trekking through India to reach Australia, had settled in south India. It took him several days to collect about 700 samples from in and around Madurai and put them through the DNA sequencer. But his search paid off. Virumandi Andi Thevar, an 18-year-old student, now a librarian, whose family had settled in the village for generations, was discovered to have the rare ‘NRYM130’ genetic mutation or ‘marker’ found in the first exodus out of Africa. The same marker was also found in some aborigines in Australia.
This discovery shot Spencer Wells to fame and he convinced the National Geographic Society, IBM and The Ted Waitt Family Foundation to fund a massive global project called Genographic. The project was officially launched in April 2005. The project hopes to unravel the mysteries of what compelled a band of their descendants to leave their home continent and spread across Eurasia. Field scientists will fan out across six continents to gather close to 100,000 samples from interesting and ancient isolated populations of the world. India is a critical link in this project.
Experts in ten regional research centres in Australia, Brazil, China, France, Lebanon, Russia, South Africa, UK, US and India will collate and interpret their findings. In India, the project roped in immunologist, Prof Ramasamy Pitchappan, chairman, School of Biological Science and Head of the Department of Immunology, Madurai Kamaraj University (MKU), and a key contributor to the discovery of the first coastal migration through India 50,000 years ago. Pitchappan had helped Wells in his Madurai project in 1998.
The MKU professor, with a deep fascination for the population structure of India, had been working extensively on immunogenetic basis of tuberculosis and leprosy susceptibility. ‘‘My association with Spencer Wells goes a long way. We knew the answer for the first coastal migration would be found somewhere in south India. Since I am based at Madurai, we performed the sampling here,’’ he recalls.
An MOU will be signed shortly between National Geographic Channel and the Madurai Kamaraj University, says Pitchappan. The Madurai chapter of the project would cost $1 million. Ten laboratories around the world will study 100,000 people across the continents for NRY (Non Recombinant Y chromosome) and mitDNA (Mitochondrial DNA). The Indian chapter will study 10,000-20,000 population samples from the country.
Explains Pitchappan: ‘‘The human genome sequence contains about 30,000 genes and this represents only 5 per cent of our genome. Though most of our sequences are 99 per cent identical, it is the mutations, mostly called single nucleotide polymorphisms, which are responsible for changing a character. Such changes in a gene is responsible for our individual differences, in eye colour or disease risk. Once in an evolutionary blue moon, a random, harmless mutation that occurs in one of these functionless stretches, is passed down to all of that person’s descendants. Generations later, finding that same mutation, or marker, in two people’s DNA indicates that they share the same genes—and perhaps the same ancestor.’’
Such changes are often obscured by the genetic reshuffling that takes place each time a mother and father’s DNA combine to make a child. Luckily some chromosomal regions preserve the telltale variations. One, called the mtDNA is passed down intact from mother to child. Similarly, most of the NRY chromosome, which determines maleness, travels intact from father to son. By comparing the mtDNA and Y chromosomes of people from various populations, geneticists can tell where and when those groups parted ways in the great migrations around the planet.
Pitchappan’s studies on several populations of Tamil Nadu described enormous variations in their genes ascribed to migration and selection. ‘‘I am interested in HLA (human leucocyte antigens, similar to red blood group on white cells) diversity in Indian population, with its various linguistic groups, tribes and caste, each unique in its own way in terms of language, culture, marriage pattern, value system and food habits. These populations are isolated in their gene pool. Though separated by space and culture, each community retains the gene pool,’’ points out Pitchappan.
The first samples will be collected from the Gond community in Orissa. “They speak the central Dravidian language. There are similarities between them and people from Tamil Nadu. They too celebrate Pongal that we observe here. It will be interesting to find out what the relationship is between two groups of people so far apart,’’ says Pitchappan.
The team will also take up village clusters in Tamil Nadu, which have names similar to those in Madhya Pradesh. ‘‘When people travel, they carry their memories. It will be interesting to study whether there are any cultural similarities and if they are accidental or incidental,’’ he says.
Eventually, India too hopes to have public participation like in the US where individuals can participate in the research effort by purchasing Genographic Project kits for $100 through the National Geographic website. DNA material is collected through cheek swab samples. To ensure participant privacy, the personal results would be included anonymously in the genetic database. Interactive element would give participants an opportunity to follow the progress of their own migratory history and the global research process through their website, providing regular updates on project findings. Presently there is no public participation in India and China, where export of genetic materials requires government approval.
http://www.indianexpress.com/news/journey-of-a-man/6685/0
No comments:
Post a Comment