FIG. 1.

Production of Nhlh1-null mice. (A) The Nhlh1 wild-type allele, the targeting vector, the region of Nhlh1 for targeted gene disruption (dashed lines), and the expected Nhlh1 mutant allele from appropriate homologous recombination events between the two are shown. H, HindIII; S, SacI; B, BamHI; E, EcoRI; solid boxes including open box (bHLH), Nhlh1 coding sequence; diagonally striped box, neo; vertically striped box, tk. (B) Southern blot analysis of tail DNA (5 μg of DNA per lane). The 7.5-kb germ line and 5.0-kb recombinant BamHI restriction fragments were detected by using the internal probe shown in panel A. (C) Northern blot analysis of newborn mouse head RNA (10 μg of total RNA per lane). The Nhlh1 full-length cDNA probe was used.