Fig. 3. The chato mutation disrupts Zfp568. (A) Domain structure of mouse Zfp568, containing two KRAB-A (green)/KRAB-B (yellow) domains and eleven zinc fingers (purple). The red asterisk marks the position of the chato point mutation. The red arrow points to the truncation caused by the RRU161 gene-trap. (B) Sequence comparison of the first KRAB-A domain of Zfp568/Chato with the KRAB-A consensus. Conserved residues are highlighted in green. Gray bars underline residues required for transcriptional repression (Margolin et al., 1994). Red letters indicate the Leu to Pro change caused by the chato point mutation. (C-F) Complementation test between chato and RRU161 gene-trap alleles. Wild-type (F) and mutant embryos of the allele combinations indicated (C-E) were assayed by in situ hybridization with T and Meox1 probes. The overall embryonic morphology, as well as defects in somites and midline, are indistinguishable between the different Zfp568 allele combinations. Notochord expression of T was irregular, showing a variable width and interruptions (arrows in D,E). (G-L) In situ hybridization with a Zfp568 probe on wild-type embryos at E7.5 (G,H) and E8.5 (J,L). RRU161 mutant embryos, which generate truncated Zfp568 transcripts, were used as negative controls (I,K). Zfp568 is expressed in all embryonic and extraembryonic tissues, as confirmed in transverse sections (H,K,L). Zfp568 was expressed at higher levels in the extraembryonic ectoderm (arrowheads). NT, neural tube; me, mesoderm; ect, ectoderm; end, endoderm; se, surface epithelia.