Targeted disruption of murine Rcor1 results in embryonic lethality. (A) Gene targeting strategy for the Rcor1 locus: schematic representation of the wild-type (WT) Rcor1⁺ allele, targeting vector, Rcor1^flox allele (Floxed), and mutant Rcor1^– allele (KO). Rcor1^flox/+ mice were crossed with Meox2-Cre and subsequently outcrossed to obtain Rcor1^+/− mice. Arrows indicate positions of the A3, A2, and B2 genotyping primers. (B) Top panel: PCR analysis with primers A3 and B2 to resolve WT and mutant Rcor1 alleles (KO) in E13.5 embryos. Bottom panel: PCR analysis with primers A2 and B2 to resolve WT and floxed (F) Rcor1 allele in E13.5 embryos. (C) Genotypes resulting from Rcor1 heterozygote matings. (D) Western blot analysis showing the expression levels of Rcor1, -2, and -3 proteins in different tissues of E13.5 WT and KO embryos. FRT, flippase recognition target sites; GAPDH, loading control; pA, polyadenylation site; PGK-Neo, neomycin resistance cassette; SD, splice donor.