structure and expression of the mouse necdin gene identification of a postmitotic neuronrestrictive core promoter necdin is a 325 amino acid residue protein encoded by a cdna clone isolated from neurally differentiated embryonal carcinoma cells in situ hybridization histochemistry revealed that necdin mrnacontaining cells in vivo coincided with postmitotic neurons in the mouse brain from early periods of neurogenesis until adulthood to study the regulation of necdin gene expression we have isolated and characterized the necdin gene from a mouse genomic dna library the necdin gene contains no intron and its upstream region lacks canonical tata and caat boxes to assess promoter activity the 5flanking sequence 844 base pairs of the necdin gene was fused to the lacz reporter gene and transiently transfected into retinoic acidtreated p19 embryonal carcinoma cells most of the transfectants expressing high levels of lacz immunoreactivity were postmitotic neurons differentiated from p19 cells deletion analysis using luciferase reporter genes demonstrated that a neuronrestrictive core promoter is localized to positions 80 to 35 in which a gcrich domain and a putative binding site for transcription factors with pas per arnt and singleminded dimerization domain are comprised these results suggest that postmitotic neuronrestrictive expression of the necdin gene is mediated by the specific cisacting elements and that this promoter is applicable to postmitotic neurontargeted expression of various transgenic systems