An enhancer element for expression of the Ncx (Enx, Hox11L1) gene in neural crest-derived cells

The murine Ncx (Enx, Hox11L1) gene is specifically expressed in a neuronal subset of neural crest-derived tissues. In attempts to elucidate the regulatory DNA element of the tissue-specific expression, we sequenced the 5'-flanking region of the Ncx gene. The transcriptional initiation site was determined at 297 nucleotides (-297) upstream from the ATG start codon (+1). A retinoic acid response element was located on the region between -1163 and -1150. Transient transfection assays with the 5'-flanking sequences fused to the luciferase gene showed that the region between -1387 and -1368 was crucial for the tissue-specific enhancer activity. Furthermore, nuclear proteins extracted from neural crest-derived cells such as murine and human neuroblastoma cells bind to the DNA region between -1387 and -1368. This DNA element was also conserved in the 5'-flanking region of the human NCX gene. Our observations strongly suggest that the DNA element (between -1387 and -1368) contributes to tissue-specific expression of the Ncx gene in murine and human species.