Regulation of chick Ebf1-3 gene expression in the pharyngeal arches, cranial sensory ganglia and placodes

Abstract

This study was conducted to identify the regulation of the expression of the cEbf1-3 (chick early B-cell factor 1-3) genes in the pharyngeal arches (PAs), cranial sensory ganglia and placodes. cEbf1 and cEbf3 were mainly expressed in the cranial neural crest cells (NCCs) occupying the PAs, but cEbf2 was expressed in the mesenchymal core. cEbf1-3 were prominently expressed in the olfactory placodes, but cEbf1 and cEbf3 were only expressed in the otic vesicle. cEbf1 was expressed in all cranial sensory ganglia, cEbf2 (only) in the dorsolateral ganglia and cEbf3 in the trigeminal and vestibular ganglia. The removal of the source (the cranial neural tube) of the cranial NCCs before their migration to the PAs led to downregulation of cEbf1 and cEbf3 and upregulation of cEbf2 expression. Gain- and loss-of-function experiments showed that sonic hedgehog did not regulate cEbf1-3 expression in the PAs or associated ganglia. Bone morphogenetic protein 2 (Bmp2) can, however, directly and indirectly regulate cEbf1 and cEbf3 expression in the PAs and the proximal (NCC-derived) portion, but not the distal (placodal-derived) portion of the cranial sensory ganglia. Conversely, cEbf2 expression was upregulated following injection of Noggin before the migration of NCCs, but did not change after the overexpression of either Noggin or Bmp2 in the arch after NCC migration. In conclusion, Bmp2 regulates cEbf1 and cEbf3 expression in PAs and cranial sensory ganglia both directly and indirectly, via the migration of cranial NCCs. However, cEbf2 expression in the mesenchymal core of PAs is controlled by other undetermined signals.