Autophagy is required for apoptotic cell clearance and neural differentiation in early otic development

Abstract

Autophagy is a highly regulated program of self-degradation of the cytosolic constituents that has key roles during early development and in adult cell growth and homeostasis. To investigate the role of autophagy in otic neurogenesis, we studied the expression of autophagy genes in early stages of chicken inner ear development and the consequences of inhibiting the autophagic pathway in organotypic cultures of explanted chicken otic vesicles. Here we show the expression of autophagy-related genes Beclin-1, Atg5 and LC3B during early development of the chicken inner ear. The otic epithelium shows intense lysosomal activity and numerous autophagic vesicles, especially at the neuroblasts exit zone.The inhibition of the transcription of LC3B by using both genetic and pharmacological approaches causes an aberrant morphology of the otic vesicle with accumulation of apoptotic cells. Moreover, inhibition of autophagy provokes the misregulation of the cell cycle in the otic epithelium, impaired neurogenesis and poor axonal outgrowth. Finally, the addition of methyl pyruvate abrogated the consequences of autophagy inhibition. Therefore, our results indicate that autophagy provides the energy required for the clearing of neuroepithelial dying cells and suggest that it is required for the migration of otic neuronal precursors. Taken together, our results show for the first time that autophagy is an active and essential process during early inner ear development.