Melanins

Melanins are the most common and ancient animal pigments, responsible for many phenotypes comprising black, grey, brown, reddish and orange colorations. These pigments result from the oxidation and polymerization of the amino acid tyrosine or phenolic compounds, the latter mainly in microorganisms. Given the conditions generated during the synthesis of different chemical forms of melanins, which in higher vertebrates occurs in cells called melanocytes, different pigmentation patterns provide animals with diverse adaptive benefits but also impose strong physiological constraints. We thus try to put the knowledge on the biochemical basis of melanin synthesis into an evolutionary context. We are particularly interested in the function and evolution of pheomelanin, the sulphurated form of melanin, and have been first in proposing an adaptative scenario that may explain the evolution of this pigment. A large part of our research activity is dedicated to empirically test this scenario.

Our research on melanin-based pigmentation is conducted from several fronts. Currently, however, we focus our activity on epigenetics. We thus investigate if genes controlling melanin synthesis are permeable to environmental influences and thus promote adaptive responses through phenotypic plasticity, or if, by contrast, the genetic control of melanin synthesis represents a strong constraint that limits animal performance under certain environmental conditions. Environmental conditions potentially affecting the expression of genes involved in melanin synthesis are those promoting oxidative stress, thus we aim at identifying environmental sources of oxidative stress. To test our hypotheses, we primarily use a wild population of European nuthatches Sitta europaea breeding in nest boxes, but also several other species of birds.

There is increasing evidence that pheomelanin synthesis plays an important role in determining risk of melanoma in humans, which is probably related to our view of pheomelanogenesis as a process that consumes a key intracellular antioxidant. We are therefore working to apply our epigenetic approach to get a better understanding of melanoma risk in humans, in collaboration with Dr. José Bernabeu-Wittel from Virgen del Rocío University Hospital, Seville. We are also working in collaboration with Dr. Pablo Loza-Alvarez and Dr. Mónica Marro, from The Institute of Photonic Sciences (ICFO) in Barcelona, to develop novel tools for determining melanoma risk.

Red-legged partridges showing pigmentation produced by different melanin forms

 

 

 

 

 

 

Eurasian nuthatch showing pheomelanin-based pigmentation in flank and undertail feathers

The melanogenesis pathway