SRA

Cell types with specialized functions fundamentally regulate animal behavior; and yet, the genetic mechanisms underlying the emergence of novel cell types and their consequences for behavior are not well understood. Here we show that the monogamous oldfield mouse (Peromyscus polionotus) has recently evolved a novel cell type in the adrenal gland that expresses the enzyme Akr1c18, which converts progesterone into 20a-hydroxyprogesterone (20a-OHP). We then demonstrate that 20a-OHP is more abundant in oldfield mice, where it induces monogamous-typical parental behaviors, than in the closely-related promiscuous deer mouse (P. maniculatus). Using quantitative trait locus mapping in a cross between these species, we ultimately discover interspecific genetic variation that drives expression of the nuclear protein Gadd45a and of the glycoprotein tenascin N, contributing to the emergence and function of this cell type in oldfield mice. Our results provide an example by which the recent evolution of a new cell type in a gland outside the brain contributes to the evolution of social behavior.