Year: 2014
Type: editorial
Abstract: Those of us who regularly watch nature movies are always struck by the tremendous diversity of pigmentation variations in living organisms. Both between and within species, we find not only a rich color palette but also a large collection of different patterns of pigmentation. Some species even change their pigmentation dynamically to signal, for instance, sexual attraction or moods, with chameleons being a prime example for the latter. And while we are at it, we cannot but marvel at the unusual chameleon that lives in the Namib desert in Southwest Africa (Chameleo namaquensis), whose feet have adapted to walk on hot desert sand and whose dark night pigmentation switches to a bright grey when the sun rises—on the sun-exposed side only—so that individuals are, at times, completely grey on one side and completely dark on the other! All this, of course, is the product of adaptive evolution, but what are the genes and mechanisms underlying this plethora of colors and patterns? In this issue of Pigment Cell & Melanoma Research, two papers deal with the oculocutaneous albinism gene OCA2 and one with a pigment patterning gene. Beirl et al. describe mutant zebrafish with defective pigmentation, the cause of which is coding region mutations in OCA2 that lead to non-functional versions of the corresponding 12-membrane-spanning protein that is involved in melanogenesis. Mutations in this gene have been found in many species, even other fish species (it is for instance also among the genes associated with troglomorphic pigment loss in cave fish), but it is the zebrafish that may provide an easy way for screening drugs that might correct human OCA2 mutations which are the primary cause of albinism in Africa. Visser et al. provide an in depth review of the molecular regulation of OCA2 through long range DNA interactions and describe how distant SNPs in non-coding regulatory regions can have profound effects on gene expression levels associated with normal variations in pigmentation in eye, hair and skin. Inoue et al. describe another zebrafish pigment mutant, dali (named after the famous Spanish surrealist painter), in which the normal pattern of stripes of melanophores and interstripes of xanthophores is disturbed and melanophores and xanthophores are intermingled. Extensive analysis by Shigeru Kondo's group has made the normal striping pattern the best documented example of a pigment patterning mechanism conforming to a Turing model of local activation and long range inhibition, but the molecular basis of this process still remains to be understood. The Inoue et al. study identifies the dali alleles as resulting from mutations in a tetraspanin gene, which encodes a scaffold protein, but how tetraspanins contribute to the normal repulsion between melanophores and xanthophores remains to be elucidated. As usual, this issue of PCMR also deals with many other aspects of the cells so dear to our hearts, including their abnormal loss in vitiligo and their malignant transformation in melanoma. And so we encourage the reader to flip through the pages and enjoy the enormous progress made in our field that helps explain both nature's beauty and nature's bane, and that will lead to rational therapies to alleviate human and animal suffering.
Source: Pigment Cell & Melanoma Research
DOI: 10.1111/pcmr.12224
Language: English
Subfield: Cell Biology
Domain: Life Sciences
Open Access status: bronze
OpenAlex ID: W2017505715