Glial cells comprise approximately 90% of the cellular constituency of the adult central nervous system (CNS) and support a vast array of physiological roles essential to CNS function. Yet, the molecular processes that control the initiation of gliogenesis from multipotent neural stem cells in vivo remain poorly understood. Thus, the overriding goal of this proposal is to elucidate the mechanisms that govern the initiation of gliogenesis from neural stem cells. We recently demonstrated that nuclear factor I (NFI) genes control the generation of glial cells in the embryonic spinal cord and are induced in neural stem cell populations coincident with the onset of gliogenesis in vivo. These properties make the NFI genes an ideal starting point from which to investigate the genetic regulatory programs that induce and maintain the early stages of gliogenesis. We, therefore, hypothesize that dissection of both the upstream and downstream events associated with NFI gene regulation will provide novel insights into the molecular control of gliogenesis.
Specific Aims 1 and 2 of this proposal are based on our discovery of two distinct regulators of NFI gene expression in the embryonic spinal cord. Using enhancer screening of the NFIA promoter we have identified a highly conserved enhancer element (e123) that recapitulates the spatial and temporal patterns of NFIA induction when introduced into the embryonic chick spinal cord. Thus, in Aim 1 we propose to exploit e123 as a tool to identify a core set of transcription factors that control NFIA induction. We have also found that bone morphogenic protein (BMP) signaling controls NFI gene expression in the embryonic spinal cord in a manner that is independent of the e123 enhancer studied in Aim 1. Therefore, in Aim 2 we plan to identify BMP-responsive elements in the NFIA promoter, define the specific role of BMP signaling in the regulation of NFI gene expression, and to establish that BMP signaling does indeed operate independently of the transcriptional control mechanisms that regulate e123 induction. Finally, Aim 3 is a logical extension of temporal profiling studies of gene expression in neural stem cells in which we identified a cohort of genes upregulated after NFI gene induction in the embryonic spinal cord. Preliminary studies indicate that four of these genes are sufficient to restore gliogenesis in the absence of NFIA, suggesting that they function downstream of NFI genes. We will use gain- and loss-of function approaches in vivo to discover whether and how these genes promote gliogenesis and function downstream of NFI genes during the initiation of gliogenesis. Upon completion of these studies, we expect to have a much more comprehensive map of molecular processes, both upstream and downstream of NFI genes that control the initiation of gliogenesis during CNS development. The resultant insights into the signals that specify commitment to the glial lineage should lift understanding of glial cell specification in the embryonic spinal cord from the speculative realm to a point where clinical applications can begin to be considered.
This project focuses on the molecular processes that control the generation of glial cells. Glial cells have been implicated in a vast array of cancers and degenerative diseases of the nervous system and understanding the developmental processes that control their generation is a key to developing new therapeutic approaches to these disorders. This proposal is centered around a gene family that controls the generation of glial cells and is also expressed in astrocytomas and contributes to their formation. Thus, the studies herein are directly applicable to the understanding and treatment of astrocytomas.
|Glasgow, Stacey M; Zhu, Wenyi; Stolt, C Claus et al. (2014) Mutual antagonism between Sox10 and NFIA regulates diversification of glial lineages and glioma subtypes. Nat Neurosci 17:1322-9|
|Lee, Jun Sung; Xiao, Jiping; Patel, Parita et al. (2014) A novel tumor-promoting role for nuclear factor IA in glioblastomas is mediated through negative regulation of p53, p21, and PAI1. Neuro Oncol 16:191-203|
|Gallo, Vittorio; Deneen, Benjamin (2014) Glial development: the crossroads of regeneration and repair in the CNS. Neuron 83:283-308|
|Chaboub, Lesley S; Deneen, Benjamin (2013) Astrocyte form and function in the developing central nervous system. Semin Pediatr Neurol 20:230-5|
|Molofsky, Anna V; Glasgow, Stacey M; Chaboub, Lesley S et al. (2013) Expression profiling of Aldh1l1-precursors in the developing spinal cord reveals glial lineage-specific genes and direct Sox9-Nfe2l1 interactions. Glia 61:1518-32|
|John Lin, Chia-Ching; Deneen, Benjamin (2013) Astrocytes: the missing link in neurologic disease? Semin Pediatr Neurol 20:236-41|
|Glasgow, Stacey M; Laug, Dylan; Brawley, Vita S et al. (2013) The miR-223/nuclear factor I-A axis regulates glial precursor proliferation and tumorigenesis in the CNS. J Neurosci 33:13560-8|
|Kang, Peng; Lee, Hyun Kyoung; Glasgow, Stacey M et al. (2012) Sox9 and NFIA coordinate a transcriptional regulatory cascade during the initiation of gliogenesis. Neuron 74:79-94|
|Lee, Hyun Kyoung; Deneen, Benjamin (2012) Daam2 is required for dorsal patterning via modulation of canonical Wnt signaling in the developing spinal cord. Dev Cell 22:183-96|