Uncovering Mechanosensory Adaptations in the Sugar Glider Patagium

Abstract

Powered flight in vertebrates, such as that displayed by bats and birds, is supported by a specialized somatosensory system that is integrated with mechanosensory feathers or hairs on the wings. This system senses airflow, thereby allowing animals to efficiently control their movements during flight. Unpowered flight, or gliding, has been hypothesized as an intermediary form in the evolution of powered flight. However, whether gliding in mammals is similarly supported by mechanosensory specialization remains unknown. Recently, we discovered hair rows on the gliding membrane (patagium) of the marsupial sugar glider (Petaurus breviceps) that are reminiscent of organized somatosensory hairs in bats. Here, we investigate whether the sugar glider patagium bears signatures of mechanosensory specialization. We answer this question by first performing a differential expression analysis of sugar glider patagium skin compared to shoulder skin. Using RNA-seq and gene ontology, we identified several key upregulated patagium genes involved in the function and development of the mechanosensory hair-associated Merkel cell / LTMR complex, including Piezo2, Ntrk2, and Ntrk3. Next, we used a weighted gene correlation analysis (WGCNA) to begin to uncover a putative gene regulatory network controlling the expression of mechanosensory genes during patagium development. Together, these results reveal that the patagium bears signatures of mechanosensory specialization through redeployment of the same ancestral developmental programs used to produce analogous mechanosensory structures.