Gene targeting of Zfp148 locus. (A) Schematic diagram of the Zfp148 locus and gene targeting strategy, showing the Zfp148 allele with short Flippase recognition target (frt, F) and Cre recombinase recognition target (LoxP, L). (B) Diagram of the Zfp148 protein in WT and null allele showing >80% deletion, including all 4 zinc finger domains. (C) PCR-based genotyping of WT, Zfp148^fl/+, Zfp148^fl/fl, and Zfp148^−/− from tail DNA. (D-E) Western blot analysis of protein extracts from e14.5 WT, Zfp148^+/−, and Zfp148^−/− whole embryos on mixed genetic background strains using 2 independent anti-Zfp148 antibodies from Woo et al⁹  in panel D and Taniuchi et al⁵²  in panel E. The epitope used to generate the antibodies is indicated on the schematic diagrams. (F) Photographs of representative Zfp148 conventional KO e18.5 embryos (top) and p14.5 (bottom) neonates on mixed C57BL/6, CD-1, and 129/Sv genetic background showing the runted postnatal phenotype. Scale bars, 1 cm. (G) Survival curves of Zfp148 WT (n = 14), Zfp148^+/− (n = 21), and Zfp148^−/− (n = 11) mice over the first 6 weeks of life. A significant difference in survival curve is observed between WT and Zfp148^−/− (Mantel-Cox Log-rank P = .0319), whereas the WT and Zfp148^+/− are not significant (Log-rank P = ns). (H) Growth curves of male WT (n = 5), Zfp148^+/− (n = 7), and Zfp148^−/− (n = 3) (left) panel, and female WT (n = 8), Zfp148^+/− (n = 11), and Zfp148^−/− (n = 6) mice (right) over the first 6 weeks of life. Growth of both female and male Zfp148^−/− mice is significantly delayed compared with WT (2-tailed paired Student t test, P < .05). PEST, peptide domain rich in proline, glutamic acid, serine, and threonine.