Genomic organization and regulatory elements of the rat latexin gene, which is expressed in a cell type-specific manner in both central and peripheral nervous systems

Latexin, a carboxypeptidase A inhibitor, is expressed in a cell type-specif ic manner in both central and peripheral nervous systems in the rat. In the neocortex, a specific subpopulation of neurons in layers V and VI expresse s latexin. In the primary sensory ganglia, the expression is restricted to smaller diameter neurons. As a first step to clarify regulatory mechanisms underlying cell type-specific expression of latexin, we have determined the organization of the rat latexin gene and analyzed its regulatory elements. The latexin gene spans approximately 5.8 kb, and consists of six exons and five introns. Three transcription initiation sites were mapped. The upstre am region lacks typical TATA or CAAT boxes but has several CC-rich sites. T o assess promoter activity, the luciferase reporter gene fused to the 5'-fl anking region (6.4 kb) of the latexin gene was transiently transfected into several cell lines. Luciferase activity was 2-8 times higher in latexin-ex pressing cells (PC12) than non-expressing cells (NS20 and L6). Deletion ana lysis with PC12 cells revealed that a core promoter is located between nucl eotide positions -261 and -201 relative to the A of the initiation codon. N erve growth factor (NGF)-responsive element(s) is located between positions -518 and -262, in which AP-1, AP-2 and NF-kappa B binding sites are found. Furthermore, we demonstrate that a 1.3 kb genomic fragment containing the first intron has transcriptional enhancing activity in PC12 cells. These re sults suggest that up and downstream regulatory elements are involved in th e control of cell type-specific expression of latexin. (C) 1999 Elsevier Sc ience B.V. All rights reserved.