In this report the identification, structure, and chromosomal localization of the human neurogranin gene (NRGN) are described. NRGN is the human homolog of the rat Ng/RC3 gene, which encodes a brain-specific protein expressed in telencephalic neurons. The human NRGN gene spans approximately 12 kb and contains four exons and three introns. All splice acceptor and donor sites conform to the canonical AG/GT rule. Human neurogranin sequence predicts a 78-amino-acid protein with 5 amino acids encoded by exon 1 and the remaining 73 amino acids encoded by exon 2. The third and fourth exons contain untranslated sequences. The overall degree of homology between the human and the rat coding sequences is 90% for the nucleic acid sequence, with 96% identity and 97.5% similarity at the protein level. The NRGN gene is expressed exclusively in brain as a single 1.3-kb mature mRNA. The promoter lacks both TATA and CAAT boxes, but shows a consensus sequence for an initiator element located 234 bases upstream from the AUG initiation codon. The 5'-flanking region contains multiple putative binding sites for transcription factors such as Sp1, GCF, AP2, and PEA3. Analysis of a panel of radiation hybrids has led to localization of the NRGN gene in YAC 763A2 (CEPH), previously mapped at 11q24. This locus is contained in a region of conserved synteny with mouse chromosome 9.