Genomic signatures of selection in the mound-building mouse Mus spicilegus

The steppe mouse, Mus spicilegus, exhibits unique characteristics such as constructing intricate mounds using vegetation and dirt, as well as a season-dependent developmental pace. The genetic and evolutionary factors behind these defining traits remain unclear. To investigate, researchers employed a molecular-evolution approach, examining protein-coding exons and brain-associated regulatory regions within the M. spicilegus genome.

The analysis uncovered a significant abundance of evidence for accelerated evolution in the M. spicilegus genome compared to its closely related species. Further transcriptional studies uncovered distinctive expression patterns in the M. spicilegus brain, which could be linked to variations in regulatory sequences. Genes identified through these molecular-evolution tests typically function in the cerebral cortices and hypothalamus, with roles in neuronal development, neural plasticity, or endocrine signaling.

Several of these genes have orthologs in other species, linked to neoteny, rapid maturation, unique building behaviors, or autism. The findings suggest that M. spicilegus has experienced notable divergence in brain-active genes, surpassing the changes observed in its relatives. The study proposes a model wherein these genes govern the seasonally influenced process of prolonged maturation and mound construction in M. spicilegus.

This research offers an evolutionary interpretation and a comprehensive list of potential factors contributing to behavioral and developmental shifts in this fascinating mouse species.