Ptf1a is required for GABAergic inhibitory neurons in the dorsal spinal cord, cerebellum, and retina. In the absence of Ptf1a, neural progenitor cells fail to generate inhibitory neurons and aberrantly assume an excitatory neuronal phenotype. Ptf1a is a class II bHLH factor that can heterodimerize with class I bHLH factors (E-proteins) to bind E-box DNA consensus sequences in vitro. However, the in vivo function of Ptf1a is in a unique transcription factor complex, called PTF1-J, that contains Ptf1a and an E-protein, plus a third factor Rbpj. This complex binds a bipartite DNA sequence containing the E-box plus a TC- box. Rbpj has a distinct function as the transcriptional effector of Notch signaling. Notch-Rbpj signaling inhibits neuronal differentiation, while Ptf1a-Rbpj functions in neuronal subtype specification. The proposal is to use in vivo chromatin immunoprecipitation combined with massive parallel sequencing platforms (ChIP-seq) to delineate the function of Ptf1a by genome wide identification of its transcription targets. ChIP-seq identified target genes of Ptf1a in vivo will be validated and characterized by combining results from expression profiling of Ptf1a cells in the dorsal neural tube, evaluating changes in expression in Ptf1a mutants, and by testing target regulatory regions in reporter assays in chick neural tube with and without exogenous Ptf1a. Identifying targets of Ptf1a will provide molecular insight into developmental processes controlling the balance of inhibitory and excitatory neurons.
Normal nervous system function requires the correct balance of inhibitory and excitatory neurons. Alterations in this balance are thought to underlie diverse neurological disorders from epilepsy to autism to hyperalgesia. Successful completion of these aims will substantially advance efforts to define transcriptional networks regulating the balance of inhibitory and excitatory neuronal specification. This is a unique opportunity to combine multiple technical advances to begin to tackle the challenging goal of defining the molecular rationale controlling the generation of neuronal diversity.
| Chang, Joshua C; Meredith, David M; Mayer, Paul R et al. (2013) Prdm13 mediates the balance of inhibitory and excitatory neurons in somatosensory circuits. Dev Cell 25:182-95 |
| Meredith, David M; Borromeo, Mark D; Deering, Tye G et al. (2013) Program specificity for Ptf1a in pancreas versus neural tube development correlates with distinct collaborating cofactors and chromatin accessibility. Mol Cell Biol 33:3166-79 |
