Skin colour controlled by key gene

It seems that the genes of Zebrafish have much in common with humans' and scientists believe that studying the fish may help solve the mystery of human skin colour.

A team of researchers at Penn State University have found that one tiny change in a key gene plays a major role in determining skin pigmentation.

They believe their finding could help explain why people of European descent have lighter skin than those from Africa and they hope the research may lead to new ways to treat skin cancer.

The scientists found that working out the details of pigmentation with help from model systems such as the zebrafish is a great paradigm for aiding the understanding of other complex diseases.

Zebrafish are ideal for research because they share many similar genes with humans.

They also have similar pigment cells, which, like humans, contain granules called melanosomes.

The research has the potential to lead to the development of new ways to modify skin colour without damaging it by tanning or using harsh chemical lighteners.

Scientists say that the genetic determination of human skin colour is one of biology's enduring mysteries.

Alterations in some of these genes are associated with disorders such as albinism, which causes very light skin, but also vision problems, while most of the genes responsible for normal differences in skin pigmentation have remained unknown.

The gene identified by the Penn State team, called SLC24A5, had not previously been suspected to be involved in pigmentation.

The researchers found a variant of the zebrafish, called golden, had fewer, smaller and less heavily pigmented melanosomes than normal fish.

They found the lighter pigmentation was caused by a mutation in the SLC24A5 gene which cuts production of a key protein.

Adding protein from the normal zebrafish resulted in fish with a darker colouring.

The researchers then analysed data from the human genome, and found a similar pattern.

It appears that most human populations carry the same version of the SLC24A5 gene, but people with a European ancestry carry a variant with just one mutation.

This mutation appears, like the zebrafish, to result in fewer, smaller and lighter melanosomes and therefore lighter skin.

On further analysis it was seen that among people with mixed European and West African ancestry, those carrying the European form of the gene tended to have lighter skin.

The findings suggest that this single gene controls up to 38% of the colour range in this mixed population.

According to researcher Dr Mark Shriver the importance of the work extends beyond pigmentation as so little is known about the genetic and evolutionary architecture of human traits.

Shriver says one can not be expected to use human genetics to understand complex diseases effectively without first working out how fundamental characteristics, such as eye, hair, and skin colour, are determined.

Many experts say that much more research is needed to work out why Europeans have evolved a different version of SLC24A5 and what function this serves, and it is too early to speculate about the implications for skin cancer.

The finding is published in the current edition of Science.

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