Fig. 2
Influence of Hand2 on cardiomyocyte production is dependent on dimerization and not on direct DNA binding. (A-E) In situ hybridization depicts cmlc2 expression at 21 somites in (A) wild-type embryos, (B) hans6 mutant embryos, (C) hans6 mutant embryos injected with hand2 mRNA, (D) hans6 mutant embryos injected with hand2 EDE mRNA and (E) hans6 mutant embryos injected with hand2 P mRNA; dorsal views, anterior upwards. The hans6 mutation is a null allele of hand2 resulting from a deletion that removes the entire hand2 gene (Yelon et al., 2000). At this stage, wild-type cardiomyocytes have formed a ring (A), whereas few cardiomyocytes have formed in the hans6 mutants (B). Cardiomyocyte formation is substantially rescued with the injection of hand2 (C) or hand2 EDE (D) mRNA, but not of hand2 P mRNA (E). (F) Average area of cmlc2 expression, as in Fig. 1E. Asterisks indicate significant differences between the phenotype of hans6 mutant embryos and the phenotypes of hans6 mutant embryos overexpressing versions of hand2. Overexpression of hand2 or hand2 EDE partially rescues the area of cmlc2 expression in hans6 mutants (n=14; *P<0.001), whereas hand2 P does not (n=14; P=0.085).