Expression of class III Semaphorins and their receptors in the developing chicken (Gallus gallus) inner ear

Abstract

Class III Semaphorin (Sema) secreted ligands are known to repel neurites expressing Neuropilin (Nrp) and/or Plexin (Plxn) receptors. There is, however, a growing body of literature supporting that Sema signaling also has alternative roles in development such as synaptogenesis, boundary formation, and vasculogenesis. To evaluate these options during inner ear development, we used in situ hybridization or immunohistochemistry to map the expression of Sema3D, Sema3F, Nrp1, Nrp2, and PlxnA1 in the chicken (Gallus gallus) inner ear from embryonic day (E)5–E10. The resulting expression patterns in either the otic epithelium or its surrounding mesenchyme suggest that Sema signaling could be involved in each of the varied functions reported for other tissues. Sema3D expression flanking the sensory tissue in vestibular organs suggests that it may repel Nrp2‐ and PlxnA1‐expressing neurites of the vestibular ganglion away from nonsensory epithelia, thus channeling them into the sensory domains at E5–E8. Expression of Sema signaling genes in the sensory hair cells of both the auditory and vestibular organs on E8–E10 may implicate Sema signaling in synaptogenesis. In the nonsensory regions of the cochlea, Sema3D in the future tegmentum vasculosum opposes Nrp1 and PlxnA1 in the future cuboidal cells; the abutment of ligand and receptors in adjacent domains may enforce or maintain the boundary between them. In the mesenchyme, Nrp1 colocalized with capillary‐rich tissue. Sema3D immediately flanks this Nrp1‐expressing tissue, suggesting a role in endothelial cell migration towards the inner ear. In summary, Sema signaling may play multiple roles in the developing inner ear.

Current concepts in cochlear ribbon synapse formation

“…These changes in gene expression, coupled with an overall increase in innervation density, are consistent with Sema3D serving as a repulsive guidance cue in the chicken cochlea. However, the expression pattern of the Sema3D transcripts (relatively uniform across the radial axis of the basilar papilla) marks a difference from the mouse Sema3F pattern (Munnamalai et al, ; Scott, Yue, Biesemeier, Lee, & Fekete, ).…”

Genome‐wide association study of fleece traits in Inner Mongolia Cashmere goats

“…SOX5 is the developmental transcription factor, which is expressed in growing hair follicles in skin as well as in sebaceous and eccrine sweat glands (Kuhn et al 1999). Semaphorin 3D (SEMA3D) is associated with Axon guidance, which depends upon mechanosensory transduction by hair cells to percept sensory information (Scott et al 2019). FGF12 (fibroblast growth factor 12) is a member of the fibroblast growth factor family that regulates MAPK, PI3K-Akt, and Ras signaling pathways involved in the sheep hair follicle development (Lv et al 2020).…”