Analysis of LacZ reporter genes in transgenic embryos suggests the presence of several cis‐acting regulatory elements in the murine Hoxb‐6 gene

Abstract

Homeobox genes are expressed in stage‐, region‐, and tissue‐specific patterns during embryonic development of the mouse. In order to understand the underlying regulatory mechanisms the murine homeobox gene Hoxb‐6 was analyzed for the presence of cis‐acting regulatory elements. Transgenic mouse embryos and lines were generated which contained the LacZ reporter gene under the control of different fragments from the Hoxb‐6 gene. In total, 13.2 kb of genomic DNA covering the entire Hoxb‐6 region were analyzed. Our results suggested the presence of three regulatory regions in the Hoxb‐6 gene: a limb/LPM element which directed gene expression into restricted regions of the developing limb buds and the ventro‐lateral and visceral mesenchyme, a regulatory element required for gene expression into ventral regions of the developing spinal cord, and a third element necessary for directing gene expression into developing mesonephric tubules and mesonephric ducts. We demonstrated that the limb/LPM element functions as an enhancer in a promoter‐ and orientiation‐independent manner. The comparison of the expression patterns of the reporter gene constructs and the endogenous Hoxb‐6 gene revealed that the regulatory regions were able to reproduce part of the Hoxb‐6 pattern. However, not all control elements necessary to completely mimic the endogenous Hoxb‐6 expression pattern could be detected, although the entire Hoxb‐6 genomic region has been analyzed. These observations suggest that for some aspects of Hoxb‐6 gene regulation the integrity of large genomic regions of the Hoxb cluster is required. © 1993 wiley‐Liss, Inc. Copyright © 1993 Wiley‐Liss, Inc.