Figure 3

A 9 kb GRS1 transgene encompassing HMCO1 drives ßglob-LacZ expression into the posterior limb bud mesenchyme. (A) A transgene encoding the three HMCO core regions downstream of the ßglob-LacZ minimal promoter and reporter results in aberrant ß-galactosidase activity in the anterior-distal limb bud mesenchyme. An asterisk marks the posterior border of the forelimb bud. A black arrow marks the anterior border of LacZ expression in the trunk. A white arrowhead points to the hindlimb bud. (B) The GRS1-ßglob-LacZ transgene is expressed in the posterior limb bud mesenchyme of transgenic founder embryos. The 9 kb GRS1 region was inserted downstream of the ßglob-LacZ reporter to keep the same arrangement as in the endogenous Grem1 locus (Figure 2A).