Identification of Cortexin: A Novel, Neuron‐Specific, 82‐Residue Membrane Protein Enriched in Rodent Cerebral Cortex

: Nucleotide sequence analysis of a cDNA clone of a rat cortex‐enriched mRNA identifies a novel integral membrane protein of 82 amino acids. The encoded protein is named cortexin to reflect its enriched expression in cortex. The amino acid sequence of rat cortexin and its mouse homologue are nearly identical (98% similarity), and both contain a conserved single membrane‐spanning region in the middle of each sequence. Northern blot analysis shows that cortexin mRNA is brain‐specific, cortexenriched, and present at significant levels in fetal brain, with peak expression in postnatal rodent brain. In situ hybridization studies detect cortexin mRNA primarily in neurons of rodent cerebral cortex, but not in cells of the hindbrain or white matter regions. The function of cortexin may be particularly important to neurons of both the developing and adult cerebral cortex.