Genomics of mammalian pigmentation patterning

Camouflage, species recognition, and morphologic diversity are all effects of mammalian fur patterns. These patterns arise from the dynamic regulation of pigment-type switching, a phenomenon in which melanocytes choose between synthesizing eumelanin (black or brown pigment) or pheomelanin (red or yellow pigment), depending on the phase of the hair growth cycle and position on the body.

Candidate gene approaches to study coat color variation in other animals have shown that the genetic basis of adaptive pigmentary variation, which had thus far been studied in laboratory mice, is largely conserved in natural populations. Nonetheless, comparative zoologic studies suggest that some components of mammalian pigment-type switching have not been identified. Some examples of these include Sex-linked yellow in Syrian hamsters and Sex-linked Orange in domestic cats that cause black-yellow variegation in heterozygous females and constitutive yellow pigment production in hemizygous males and homozygous females. None of these phenomena have been described in the laboratory mouse, and understanding the molecular genetic basis of these pigment patterns will provide valuable insight into the biology and evolution of pigment variation in nature.

Studying how these pigment patterns arise will require investigation of pathways that regulate pigment-type switching in non-laboratory animals, which is now possible due to the availability of multiple mammalian genome sequences and the development of ultra high-throughput sequencing. We are currently adopting a genomics approach to sequence and compare the skin transcriptome of alternating pigment-type regions dissected from animals that have striking pigment patterns.