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) han^s6 mutant embryos, (C) han^s6 mutant embryos injected with hand2 mRNA, (D) han^s6 mutant embryos injected with hand2 EDE mRNA and (E) han^s6 mutant embryos injected with hand2 P mRNA; dorsal views, anterior upwards. The han^s6 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 han^s6 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 han^s6 mutant embryos and the phenotypes of han^s6 mutant embryos overexpressing versions of hand2. Overexpression of hand2 or hand2 EDE partially rescues the area of cmlc2 expression in han^s6 mutants (n=14; *P<0.001), whereas hand2 P does not (n=14; P=0.085).