Little fish sheds light on the shades of humanity

WASHINGTON - A little striped fish has helped scientists begin to solve one of the biggest mysteries in biology - which genes control differences in human skin, eye and hair colour.

The international team of scientists reported they had found a gene that makes African zebrafish of a lighter-than-normal colour - and say the same gene helps explain the light-coloured hair, skin and eyes of many Europeans. They say just a tiny change in a single amino acid plays a major role in causing the distinctive light European colouring.

The gene was called SLC24A5, Keith Cheng of Pennsylvania State University and colleagues said.

"Our results suggest that SLC24A5 explains between 25 and 38 per cent of the European-African difference in skin melanin index," they wrote in the latest issue of the journal Science.

Cheng's team found a gene that appeared to make some zebrafish "golden" - with lighter-than-usual stripes.

Under a microscope, the skin of these fish have smaller, fewer structures called melanophores. In European people, pigment granules called melanosomes are fewer, smaller, and lighter than those of West Africans.

The melanosomes of East Asians fall in between. This suggested gene variations may be responsible and may be similar in vertebrates.

Nearly all Africans and East Asians have an amino acid called alanine in that gene, while 98 per cent of Europeans tested had an amino acid called threonine there.

The researchers injected the base human version into "golden" zebrafish embryos and found it made them develop into normal dark-striped fish. This clinched the idea that the human gene was the equivalent of the fish gene.

- REUTERS