THE ROLE OF NEUROGENIN2 AND NEUROD1, AND THEIR DOWNSTREAM TARGETS, IN TRIGEMINAL GANGLION DEVELOPMENT

Abstract

The trigeminal ganglion contains the cell bodies of sensory neurons comprising cranial nerve V and functions to relay information related to pain, touch, and temperature from the face and head to the central nervous system. Like other cranial ganglia, the trigeminal ganglion is composed of neuronal derivatives of two critical embryonic cell types, neural crest cells and placode cells. Neurogenesis within the cranial ganglia is promoted by Neurogenin2, which is expressed in trigeminal placode cells and their neuronal derivatives, and transcriptionally activates neuronal differentiation genes like Neuronal Differentiation 1 (or NeuroD1). Other targets downstream of Neurogenin2 and NeuroD1 include Drebrin1 and Stathmin2, cell polarity and cytoskeletal regulators that mediate changes in neuron cell shape during neurogenesis. Little is known, however, about the role of Neurogenin2, NeuroD1, and their downstream signaling pathways during trigeminal gangliogenesis in the chick embryo. By depleting Neurogenin2 and NeuroD1 from chick trigeminal placode cells with morpholino antisense oligonucleotides, we examined how these proteins influence chick trigeminal ganglion development. Additionally, we identified the expression of Drebrin1 and Stathmin2 in trigeminal ganglion neurons. Taken together, our results highlight, for the first time, functional roles for Neurogenin2 and NeuroD1 during chick trigeminal gangliogenesis. These studies will not only improve our understanding of the molecular mechanisms underlying trigeminal ganglion development, but may also provide insight into human and animal diseases of the peripheral nervous system.