Seasonal regulation of melanogenesis in ptarmigan

Abstract

Ptarmigan are one of the few animals, and only bird species, to undergo seasonal colour change. Every year they moult between a white winter morph and brown summer and autumn morphs and back again. Skin samples were collected from Lagopus muta and Lagopus lagopus during the autumn moult between brown and white morphs to compare areas with brown feathers and areas that had grown white feathers. The relative gene expression for selected key genes of melanogenesis was then calculated through qPCR. The genes tested were POMC, PC1, PC2, ASIP, MC1R, TYR, TYRP1 & DCT. Most did not show any significant difference between the two sample groups in either species, except TYRP1 which had significantly lower expression in the white samples for Lagopus muta. The promoter regions of the above genes and CORIN, CREB1, MITF, OCA2, SLC7A11, SLC45A2 & TBX19 were compared using EMBOSS polydot and CiiiDER workflow. These comparisons looked at the Transcription Factor Binding Sites (TFBS) in seven galliform species: the three Lagopus species (L. muta, L. lagopus and L. leucura) and L. l. scoticus as well as Gallus gallus, Coturnix japonica & Centrocercus urophasianus. There were several differences between the promoter regions, the most common was a missing TFBS for Pax2 in several genes in L. l. scoticus. None of the TFBS differences have been directly linked to melanogenesis of follicle cycling in other research. The results of these studies do not suggest seasonal differences in the expression of the first eight genes but the differences in the promoter regions do suggest that the several of the genes could have different regulation methods. This comparison of promoter regions creates a starting point for future promoter analysis and further research on seasonal regulation of melanogenesis in ptarmigan.