JmjD2B histone demethylase regulates otic placode invagination via epigenetic control of Dlx3.

BUZZI, A. L.; URIBE, R.; BRONNER, M.; STROBL MAZZULLA, P.H.

Seattle

Simposio; Society for Developmental Biology 73rd Annual meeting; 2014

The inner ear is one of the most sophisticated sensory organs in vertebrates, relaying both acoustic and motion/balance information to the brain. The inner early formation involves an intricately regulated series of events from otic placode induction, to invagination and overt differentiation. Here, we show that the epigenetic modifier JmjD2B, a histone demethylase, plays an important role in chick inner ear development. In situ hybridization (ISH) reveals expression of JmjD2B in the otic placode during its induction and later at the rim of the invaginating otic vesicle. Consistent with this, immunostaining reveals clear variations in the spatiotemporal expression of JmjD2B substrates, the epigenetic marks H3K9me3 and H3K36me3, in ectodermal, invaginating and post-invaginating otic cells. Unilateral electroporation of JmjD2B morpholino into stage 8 chick embryos reduced the expression of several ear markers, including Pax2, Dlx3, Soho1 and Sox10 by stage 13. Moreover, JmjD2B knock-down caused a clear defect in the placode cell invagination, accompanied by loss of apicobasal polarity, disorganization and multilayering of placode cells, and misexpression of cell adhesion molecules like E-cadherin. To identify potential direct targets of JmjD2B, we performed in vivo chromatin immunoprecipitation (ChIP) on dissected otic placodes and otocysts. The results show that JmjD2B interacts with regulatory regions of the Dlx3 locus, but not with Pax2 or Soho1. Taken together, the results reveal for the first time an epigenetic modification, via histone demethylation, that influences expression of key genes implicated in inner ear invagination in vertebrate embryos.