Differential Regulation of Androgen Receptor and DNA Methylation in Songbirds

Abstract

Animal behavior is a highly diverse phenotype constrained in species- or strain-specific manner. However, little is known regarding the molecular basis of evolution of animal behavior and its epigenetic contribution. Therefore, oscine songbirds possess a specialized neural system, called the song system for learning and producing species-specific vocal patterns. Approximately 3000 species of songbirds generate species-specific song patterns that have been learned from conspecific tutors. Song phenotypes are affected through domestication in some species, such as canary and the Bengalese finch. The Bengalese finch, a domesticated strain, produces a distinct song pattern with more complex syntax from the white-rumped munia, a wild-type strain. On the molecular level, the androgen receptor (AR) is differentially expressed in the basal ganglia vocal nucleus between these two strains and even within the domesticated population. Consistent with the difference of AR expression, an epigenetic modification, the state of DNA methylation differs in the region upstream of the AR gene in these populations. This differential AR expression level is correlated with a song phenotype: the mean coefficient variance of syllable-interval duration. The regulation of distribution of syllable-interval duration is recognized as one of the key phenotypic differences in the evolution of complex vocal syntax. The evidence provides insights into the molecular basis of behavioral evolution via the regulation of hormone-related genes and demonstrates a potential contribution of epigenetic modifications for behavioral phenotype regulation.