Dlx5/6‐enhancer directed expression of Cre recombinase in the pharyngeal arches and brain

Abstract

SummaryDlx5 and Dlx6, two members of the Distalless gene family, are required for development of numerous tissues during embryogenesis, including facial and limb development. This gene pair is expressed in tandem, transcribed toward each other and separated by a short intergenic region containing multiple putative enhancers. Targeted inactivation of Dlx5 and Dlx6 in mice results in multiple developmental defects in craniofacial and limb structures, suggesting that these genes are crucial for aspects of both neural crest and nonneural crest development. To further investigate potential developmental roles of Dlx5 and Dlx6, we used one of the Dlx5/6 intergenic enhancers to drive Cre recombinase expression in transgenic mice. Crossing Dlx5/6-Cre transgenic mice with mice from the R26R strain results in β-galactosidase staining in the apical ectodermal ridge, brain, and neural crest-derived mesenchyme of the pharyngeal arches, with staining in term embryos observed in the facial skeleton and specific brain structures. However, in contrast to endogenous expression patterns of Dlx5 and Dlx6, Cre expression within the pharyngeal arches occurs during a very narrow window in early development. Our studies suggest that Dlx5/6-Cre mice may prove useful both in further understanding the function and regulation of Distalless genes during development and in studies of gene function in conditional knockout mice.

Deletion of the endothelin-A receptor gene within the developing mandible

“…Briefly, these mice carry two loxP sites that flank the last three exons of the Ednra gene (hence the term "flox"). We have also previously described the generation and characterization of Dlx5/6-Cre transgenic mice (Ruest et al 2003). Cre expression in these mice is restricted to the mandibular first arch, with expression first detected at embryonic day (E) 9.5 before being down regulated by E10.5.…”

“…Ednra flox/flox (Kedzierski et al 2003) and Dlx5/6-Cre (Ruest et al 2003) mice were generated as previously described. Ednra flox/flox ; Dlx5/6-Cre embryos were generated by crossing Ednra flox/+ ; Dlx5/6-Cre female mice with Ednra flox/flox male mice.…”

“…Genotyping was performed by PCR using genomic DNA prepared from tail biopsies or amniotic sacs. Dlx5/6-Cre mouse genotyping was performed as previously described (Ruest et al 2003). The genotyping of the Ednra conditional allele was performed with the following primers: 5′-ACACAACCATGGTGTCGA-3′ and 5′-CGGTTCTTATCCATCTCATC-3′.…”

Downregulation of Dlx5 and Dlx6 expression by Hand2 is essential for initiation of tongue morphogenesis

“…This enhancer, referred to as I56i, directs transgene expression to the Dlx5/Dlx6 expression domain within the mandibular arch (Ruest et al, 2003b;Zerucha et al, 2000a). Co-transfection of the I56i-luciferase vector and Dlx5, a known inducer of the I56i enhancer, resulted in an almost fivefold increase in luciferase activity (Fig.…”

Dlx3 is expressed in the ventral forebrain of chicken embryos: implications for the evolution of the Dlx gene family

“…Intergenic regions for the genomically compact pufferfish Takifugu rubripes and Spheroides nephalus are smaller at 3-5 kb (Ghanem et al, 2003), with Danio rerio having intermediate sizes of 3.5 -7.3 kb (Ellies et al, 1997). Despite the significant variation in their size, several highly conserved non-coding sequence elements have been identified in the intergenic regions of Dlx bigene clusters and have been shown to behave as tissue-specific enhancers , Sumiyama et al, 2002, Ghanem et al, 2003, Ruest et al, 2003, Park et al, 2004. Intergenic enhancer sharing therefore accounts for much of the overlap in expression of members of a Dlx bigene cluster.…”