This transgenic construct consisted of 200 bp of human TFAP2A (TCFAP2A) promoter sequence (encoding a specific enhancer element) followed by NLS-cre, an SV40 polyA signal, and a 1.8 kb TFAP2A genomic fragment extending from within exon 5 through a portion of exon 6. The human intron 5 sequence includes the frontonasal prominence- and limb-specific enhancer. Expression of cre recombinase was detected in the embryonic face and limb mesenchyme. New research has determined that the transgene inserted into intron 9 of the Hhat locus. This insertion creates a non-functional allele.