FIG. 1.

Targeted disruption of mouse Six4. (A) Structures of the wild-type allele, targeting vector, and targeted allele. Boxes represent exons. Gray shading indicates coding regions, and black shading indicates the Six homologous region and homeobox. The hatched region marks the region encoding the transactivation domain. The targeting vector consisted of the 5′ homology region, lacZ, neo, 3′ homology region, and at the 3′ end the diphtheria toxin A gene (dt) for negative selection. Arrows beneath the target allele represent PCR primers (9705 and 9706) for screening. Restriction fragments detected by Southern blot analysis are shown by horizontal arrows with their sizes in kilobases. B, BamHI; S, SacI. (B) Southern blot analysis of mouse tail DNA isolated from the founder mice from a mating of heterozygous parents. DNAs were digested with BamHI or SacI and hybridized with the probes indicated in panel A. +/+, wild-type mouse; +/−, heterozygous mutant mouse; −/−, homozygous mutant mouse.