NSCL-1 and NSCL-2 synergistically determine the fate of GnRH-1 neurons and control necdin gene expression.

To study the role of the bHLH genes NSCL-1 and NSCL-2 in the development of GnRH-1 neurons, we have generated compound mutant mice. Mutant animals die at birth and show a virtually complete absence of GnRH-1 neurons in the posterior parts of the brain at E18.5 and an aberrant morphology of the remaining GnRH-1 neurons in the anterior parts of the brain indicating that NSCL-1 and NSCL-2 might concomitantly control differentiation/migration of GnRH-1 neurons in a cell autonomous manner. To gain further insights into this process, we screened for NSCL target genes using DNA array hybridization and detected necdin, which is deleted in the human Prader-Willi syndrome phenotypically resembling the NSCL-2 mutation. Using chromatin immunoprecipitation and site-directed mutagenesis of the necdin promoter, we demonstrate that NSCLs together with additional cofactors directly control transcription of the necdin gene. NSCL-dependent control of necdin expression might be instrumental for proper neuronal cell differentiation and enable GnRH-1 neurons to migrate.