Sequence-specific DNA-binding transcriptional regulator that plays a key role in neurogenesis and neuroendocrine cell differentiation during embryonic and/or fetal development. Binds to the consensus sequence 5'-[TG][TC][TC][TT][GA]GGG[CG]A-3' in target promoters. Acts as a transcriptional repressor of NEUROD1 and INS expression via its interaction with cyclin CCND1 in a cell cycle-independent manner. Negatively regulates skeletal muscle-specific gene expression in endocrine cells of the pituitary by inhibiting the Notch signaling pathway. Represses target gene transcription by recruiting chromatin-modifying factors, such as HDAC1, HDAC2, HDAC3, KDM1A and RCOR1 histone deacetylases. Binds to its own promoter, suggesting autoregulation as a self-control feedback mechanism. Competes with histone H3 for the same binding site on the histone demethylase complex formed by KDM1A and RCOR1, and thereby inhibits demethylation of histone H3 at 'Lys-4' (By similarity). Promotes the generation and expansion of neuronal basal progenitor cells in the developing neocortex. Involved in the differentiation of endocrine cells of the developing anterior pituitary gland, of the pancreas and intestine, and of sympatho-adrenal cells in the peripheral nervous system. Promotes cell cycle signaling arrest and inhibition of cellular proliferation. Interacts (via the N-terminal region) with CCND1 (via cyclin N-terminal domain); the interaction competes with the binding of CCND1 to CDK4 during cell cycle progression and increases its transcriptional repressor activity. Interacts with HDAC3; the interaction increases its transcriptional repressor activity (By similarity). Interacts (via the SNAG domain) with HDAC1. Interacts (via the SNAG domain) with HDAC2. Interacts (via the SNAG domain) with KDM1A. Interacts (via the SNAG domain) with RCOR1. Interacts with SORBS1. Expressed in adrenal gland. Expressed in the dentate gyrus of the hippocampus and the wall of the lateral ventricle. Expressed in pancreatic and intestinal endocrine cells. Expressed in differentiating endocrine cells of the anterior pituitary gland between 11.5 and 17.5 dpc. Expressed in all hormone-secreting cell types of the pituitary gland. Expressed in primary sympathetic ganglion chain, spinal cord and in neurons of the dorsal root ganglia at 9.5 dpc. Expressed in chromaffin cells of the adrenal medulla at 13.5 dpc (at protein level). Expressed in the developing central nervous system (CNS). Expressed in midbrain-hindbrain region at 9.5 dpc, in the spinal cord and telencephalon at 11 dpc. Expressed in the forebrain, midbrain, hind brain, spinal cord, cerebellum, olfactory bulb and retina between 11.5 and 14.5 dpc. Expressed in neural stem and progenitor cells of the developing neocortex in both the ventricular zone (VZ) and in the adjacent subventricular zone (SVZ), and in the external granule cell layer of the developing cerebellum between 11 and 16.5 dpc. Expressed in neural progenitor cells at the apical side of the VZ, collectively referred to as apical basal cells (APs; neuroepithelial cells, radial glial cells and short neural precursors) between 10.5 and 16.5 dpc. Expressed in neural progenitor cells in the basal region of the VZ between 10.5 and 16.5 dpc and at later stages in basal progenitor cells (BPs) of the SVZ. Expressed in the cerebellum and pineal gland at 18.5 dpc. Expressed in islet progenitor cells at 10.5 dpc. Expressed in endocrine pancreatic cells, enteric nervous system, duodenum, stomach, thymus, thyroid, adrenal glands at 15.5 dpc. The C-terminal region is necessary for NEUROD1 promoter DNA-binding and transcriptional repressor activity. Mice die during the second half of gestation; lethality is caused by heart failure due to insufficient catecholamine synthesis. Display pancreatic, intestinal and sympatho-adrenal endocrine cell development impairment. Exhibits fewer terminally dividing neuronogenic basal progenitor cells (BPs) in the neocortex. Belongs to the INSM1 family.