TRANSCRIPTION FACTORS IN CONTROL OF BRAIN DEVELOPMENT

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We are currently studying DNA-binding factors that serve as transcriptional regulators in the developing and mature nervous system, specifically the POU-domain factor Brn-3.0 and related molecules. The expression pattern of Brn-3.0, described extensively in our previous work, indicates a role in the terminal differentiation and maintenance of specific neurons in the CNS and peripheral sensory system. We showed that the initial pattern of Brn-3.0 expression in the dorsal neural tube is negatively regulated by the ventral signal SHH. Unlike many transcription factors expressed transiently in development, Brn-3.0 characterizes specific neurons throughout life. This is due in part to recently identified autoregulatory elements in brn-3.0 genomic locus through which Brn-3.0 can strongly enhance its own transcription. Targeted disruption of Brn-3.0 in mice results in neonatal death and loss of neurons in the sensory ganglia and some CNS nuclei which express this factor. One model for this neuronal loss is a failure of Brn-3.0 (-/-) neurons to respond to neurotrophins necessary for survival. It is not known whether neonatal death is due to loss of the central or peripheral functions of Brn-3.0, or both. Our goals are to: 1) Further define the independent enhancer regions that target Brn-3.0 expression to the sensory PNS and specific CNS neurons. 2) Use mice expressing marker genes under control of the Brn-3.0 sensory enhancer to examine neuronal development in mice deficient in key regulators of neurodevelopment, including Brn-3.0 itself, and selected neurotrophins and their receptors. 3) Examine the molecular mechanisms of the regulation of PNS- and CNS-specific expression of Brn-3.0. 4) Target expression of an axonal marker, tau-bgal, to Brn-3.0 neurons by homologous recombination at the Brn-3.0 locus 5) Use targeting of Cre-recombinase to the peripheral nervous system, followed by loxP-mediated excision of Brn-3.0 coding sequences, to produce mice with PNS-specific defects in Brn-3.0 expression. This allows the roles of Brn-3.0 in the CNS and peripheral sensory system to be distinguished. We are using the NCMIR computational resources for statistical analysis of 3D confocal volumes of dual labeled fluorescent proteins in embryos. These studies will advance our understanding of neurological and behavioral illnesses that have a genetic or developmental component.