The role of isoforms in the evolution of cryptic coloration in Peromyscus mice

A central goal of evolutionary biology is to understand the molecular mechanisms underlying phenotypic adaptation. While the contribution of protein-coding and cis-regulatory mutations to adaptive traits has been well documented, additional sources of variation – such as the production of alternative RNA transcripts from a single gene, or isoforms – have been understudied. Here, we focus on the pigmentation gene Agouti, known to express multiple alternative transcripts, to investigate the role of isoform usage in the evolution of cryptic colour phenotypes in deer mice (genus Peromyscus). We first characterize the Agouti isoforms expressed in the Peromyscus skin and find two novel isoforms not previously identified in Mus. Next, we show that a locally adapted light-coloured population of P. maniculatus living on the Nebraska Sand Hills shows an upregulation of a single Agouti isoform, termed 1C, compared with their ancestral dark-coloured conspecifics. Using in vitro assays, we show that...