Investigating the Role of Nav1.5 in Somatosensory Mechanosensation

Abstract

Low-threshold mechanoreceptors (LTMR) are a diverse subpopulation of primary afferent neurons responsible for sensing the variety of mechanical stimuli experienced on a day-to-day basis. However, molecular details of touch sensation in LTMRs remain elusive. To investigate the neurons and molecules underlying touch sensation, we study the mechanosensation in a novel model system - trigeminal neurons of tactile foraging ducks (Anas peking). Ducks rely on the abundance of mechanoreceptors in the glabrous skin of their bill in order to identify food in the absence of olfactory or visual cues. To understand the molecular basis of mechanosensation in trigeminal LTMRs, we compared the transcriptome of duck trigeminal (TG) and dorsal root ganglia (DRG) (Schneider et al., PNAS 2014). The analysis revealed elevated expression of the mechanosensitive voltage-gated sodium channel Nav1.5 (SCN5a) in duck TG compared to DRG. Nav1.5 is known for its contribution to the cardiac action potential, but its role in the sense of touch is unexplored. Considering the high level of Nav1.5 expression in duck TG by RNA-seq and the mechanosensitivity of Nav1.5, we hypothesize a role of Nav1.5 in transduction or transmission of touch. Our work demonstrates a wide distribution of the SCN5a transcript in duck TG neurons, providing further rationale for a role of Nav1.5 in touch sensation. Here, we performed biophysical characterization of duck Nav1.5 in vitro and in trigeminal neurons. Our data reveals key functional differences between the human and duck orthologs of Nav1.5 and suggest a novel role for this channel in the sense of touch.