The Hindu : Opinion / News Analysis : A gene that travelled from India with the Portugese

Online edition of India's National Newspaper
Monday, Apr 25, 2005

Opinion

Opinion - News Analysis

A gene that travelled from India with the Portugese

N. Gopal Raj

The genetic propensity for a rare nerve degenerative disorder probably originated in South Asia.

IN THE 15th Century, Vasco da Gama arrived in what is today Kozhikode in northern Kerala and soon the Portugese established a considerable presence all along the west coast of India. But the Portugese may have got more than just the spices they came for. Research by Indian scientists that has just been published suggests that the genetic propensity for a rare nerve degenerative disorder probably originated in South Asia and travelled across the globe through the trade routes that linked Portugal's global empire.

People with spinocerebellar ataxia suffer from tremors, clumsiness of movement and a staring look.

Type 3 spinocerebellar ataxia is known as `Machado-Joseph disease' (MJD). Worldwide, nearly three-quarters of those with MJD carry a genetic marker called the `ACA haplotype'. The origins of this haplotype was traced to the Azores, the islands in the Atlantic Ocean that the Portugese used as a stopping point for ships travelling to and from their far-flung empire, and to Portugal itself.

"When we started our research, we asked the question whether the ACA haplotype and MJD could have come to India through the Portugese presence here," says Mitali Mukerjee of the Institute for Genomics and Integrative Biology (IGIB) at Delhi.

To find the answer, Uma Mittal, a doctoral student at IGIB, analysed genetic variations in people suffering from MJD. While the ACA haplotype was very rare among the general population of the Azores and Portugal, this haplotype is widespread among the Indian population. Despite this, fewer than three per cent of ataxia sufferers in India have MJD, compared to 29 per cent in Korea, 43 per cent in Japan and 84 per cent among the Portugese.

The study showed that in India there was a much lower proportion than in Japan of those with gene variants that could lead to mutant forms causing MJD in later generations. This "might explain the lower prevalence of MJD in India," observed scientists of IGIB, the All India Institute of Medical Sciences in Delhi, and the National Institute of Mental Health and Neurosciences (NIMHANS) in Bangalore in their joint paper that was published in the medical journal, Archives of Neurology. The prevalence of all ataxia disorders is believed to be less than three for every 100,000 people in India.

"We propose that a substantial genetic propensity to develop this disease was introduced into the Azores islands and Portugal by admixture with the Indian population," says Sanjeev Jain of NIMHANS, one of the authors of the paper. Such mixing could have happened because the Portugese did not discriminate against those of mixed parentage, who enjoyed significant mobility within Portugese society. In addition, the Portugese were impressed by the seamanship of people of the Konkan coast and employed them as sailors.

Many Indians also served as soldiers for Portugal. Through the Azores, the causative gene, carrying traces of its origin in the Indian sub-continent, spread to every continent.

Printer friendly page
Send this article to Friends by E-Mail

Opinion