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This study reports the results of a comparative sequencing study in higher primates, focusing on the intergenic region located between HOXB6 and HOXB7. We have examined an 832 bp. region, encompassing a putative Lateral Plate Mesoderm (LPM) enhancer element in a variety of anthropoid apes. The interspecific comparisons reveal extensive substitutions occurring within this region, with a marked bias in favor of CT transitions within the enhancer element. The pattern of these substitutions suggests that the LPM enhancer region is subject to specific sequence and compositional constraints that are only revealed through comparative sequencing. These constraints produce an enhancer signature, the CpG microisland, which may be useful in identifying additional regulatory elements located within the HOX complexes. J. Exp. Zool. (Mol. Dev. Evol.) 285:170–176, 1999. © 1999 Wiley-Liss, Inc.

Homeobox genes are expressed in stage-, region-, and tissue-specific patterns during embryonic development of the mouse. In order to study cis-acting regulatory elements of murine homeobox genes, transgenic mouse embryos were generated which contained the LacZ reporter gene under the control of different fragments from the murine Hoxb6 gene. A 2 kb limb/LPM (lateral plate mesoderm) enhancer region was identified which reproduced several aspects of the endogenous Hoxb6 gene expression pattern in the mesenchyme of the developing limb buds and the ventro-lateral body region. Both tissues represent derivatives of the lateral plate mesoderm. In order to describe proteins interacting with specific DNA sequences in the limb/LPM enhancer, electro mobility shift assays were performed using nuclear extracts prepared from embryonic tissues. Several specific DNA-protein complexes could be detected, suggesting that these DNA-protein interactions are important for the regulation of Hoxb6 gene expression.