General Biology Seminar

We are beginning to understand the pathways employed by embryonic cells that differentiate as neurons, however, the mechanisms that determine how specific types of neurons form in specific locations remains obscure.  Identification of the mechanisms that determine the location of neural differentiation is part of the broader question of determining how neuronal diversity and nervous system architecture arise.  I employ urchin embryos as a model to explore the mechanisms that pattern embryonic neural development.  The larval nervous system has a small region, termed the apical organ that develops from a neuroepithelium and functions as a central nervous system.  Peripheral sensory neurons arise in the ectoderm and project axons to the apical organ.  We have developed antibodies to several key transcription factors and differentiation markers that establish a precise timeline for the specification and differentiation of neurons in the apical organ and specific peripheral neurons.  Several lines of evidence indicate that Delta/Notch signaling suppresses neural differentiation, yet the regulatory state of the neural progenitors upon which it is acting differs between central and peripheral neurons.  Thus, in spite of the relative simplicity of the urchin model, subtle differences in the signaling that impinges on neural progenitors is a key part of generating neuronal diversity.