Murine Hoxd4 expression in the CNS requires multiple elements including a retinoic acid response element

We have identified a retinoic acid response element (RARE) within a neural enhancer located 3' to the Hoxd4 gene. This RARE is required for the initia tion and maintenance of Hoxd4 transgene expression in neurectoderm, and for full anteriorized expression upon retinoic acid (RA) treatment. Mutations within the sequence TTTTCTG, located 2 bp downstream of the RARE, posterior ized transgene activity. However, the onset of transgene expression and its response to RA were indistinguishable from wild type. While the TTTTCTG mo tif resembles a CDX binding site, human CDX1 protein did not interact with this element in vitro. Three additional regions were also shown to control transgene expression in neurectoderm, establishing that multiple elements c onstitute the Hoxd4 neural enhancer. (C) 2000 Elsevier Science ireland Ltd. All rights reserved.