Rr133^tm1Eno

A 754 bp region, containing the 208 bp branchial arch enhancer upstream of the Hand2 gene, was replaced with a loxP site flanked neomycin resistance gene cassette, which was removed through subsequent cre-mediated recombination. Whole mount in situ hybridization of homozygous mutant embryos showed a lack of endogenous transcript in the ventrolateral portions of the first and second branchial arches. (J:81764)