Comprehensive Analysis of Rodent-Specific Probasin Gene Reveals Its Evolutionary Origin in Pseudoautosomal Region and Provides Novel Insights into Rodent Phylogeny

Abstract

Probasin protein was originally identified as a basic protein present in rat prostate epithelium. So far, its physiological role, its origin, and its presence in other species including humans remain largely elusive. With the ever-growing number of genome assemblies, thus far, probasin genes (Pbsn/PBSN) have only been predicted in a subset of rodent genomes. In this study, we addressed the phylogeny of probasin genes and found them to be exclusively present in members of the superfamily Muroidea. It first emerged in the so-called pseudoautosomal region, a subtelomeric gene cluster of both mammalian sex chromosomes. During evolution of the Muroidea lineages, probasin recombined to the X-specific region of the X-chromosome in mice and hamster species. This event likely saved the gene from events that other pseudoautosomal genes suffered, namely displaying an increase in G and C nucleotide composition or accumulation of repetitive elements. We observed changes to its coding region, e.g., sequence insertions in exon 6, which challenge the current understanding of rodent phylogeny, in particular regarding the evolutionary history of tribe formation within the subfamily Murinae. Analyzing the evolution of probasin genes in Muroidea allows fostering understanding of phylogenetic relationships in one of the largest groups of mammalian species.