Developing vestibular neurons display altered commissural projections with depletion of chondroitin sulfates of the hindbrain matrix

Abstract

Chondroitin sulfate (CS) proteoglycans are involved in matrix interactions that restrict neuronal populations and their processes. To assess vestibular commissural projections in environments depleted of CS moieties, chondroitinase ABC was delivered into the 4th ventricles of rat embryos (E11.5–E13.5) in culture and DiI tracing was performed from the vestibular nuclear complex near the VIIIth cranial nerve entry zone. Enzyme treatment in E11.5 resulted in robust outgrowths that extended more than half-way towards the midline. Enzyme treatments in E12.5 and E13.5 resulted in defasciculation and divergence of outgrowths from the course of the pioneers. These results provide in vivo evidence for contributions of CS to limit stray outgrowth and foster axonal fasciculation as vestibular neurons project across the midline towards the contralateral target.