In early 2008 scientists identified the gene SLC45A2 as one of the key genes involved in pigmentation, notably in dark hair pigmentation among the polish population. SLC45A2 stands for solute carrier family 45, member 2 and is found on the short arm of chromosome 5. The gene ultimately encodes membrane-associated transporter protein (MATP) which regulates traffic of melanosomal proteins into melanosomes. These are organelles within pigmentation cells (melanocytes) where melanin is produced. Melanin functions as a protective agent. It is dark in colour and accumulates in cells in reaction to sunlight, absorbing light and protecting the nuclear genome from mutations caused by the ionizing radiation from UV rays. Thus, making MATP and the genetics of SLC45A2 an important part of the skin pigmentation pathway. A polymorphism in gene SLC45A2 results in one of two proteins either MATP-E272K or MATP-L374F. The author took a sample of 392 individuals in Poland of varying hair, skin and eye colour. The rarer allele L374 was found in only 2.3% of the population but all individuals in the sample that had the allele had dark hair. The authors of this article calculated the the odds that an individual with this allele and found they had an increased likelihood of having dark hair of 7 times. Similar results have been confirmed in studies in Germany where 96.7% of the sample had the lighter F374 protein and 100% of the sample in Japan had the darker 374L protein.
The mechanism behind the gene however is a little confusing in that the L374 protein (dark hair) has a lower transcription level compared to 374F protein (light hair). This would mean that less L374 proteins are being transcribed which ultimately means less melanin is being transported into the cells producing a lighter pigmentation but the opposite is occurring. The process of pigmentation is however a very complex biochemical process involving many genes. The knowledge gained can however help direct future endeavours for development in this area of biochemistry where this gene may act as a marker for black hair.
References:
1. Wojciech Branicki, Urszula Brudnik, Jolanta Draus-Barini, Tomasz Kupiec, Anna Wojas-Pelc (2008). Association of the SLC45A2 gene with physiological human hair colour variation Journal of Human Genetics DOI: 10.1007/s10038-008-0338-3
2. Kamrani, Kambiz (2008). SLC45A2/MATP & The Genetics Of Human Hair Colour. Retrieved March 21, 2009, from http://anthropology.net/2008/10/09/slc45a2matp-the-genetics-of-human-hair-color.
3. Razib (2008). Genetic variation; context is key. Retrieved March 21, 2009, from http://scienceblogs.com/gnxp/2008/10/genetic_variation_context.php.
