Fig. s4

Specification of cardiac progenitor cells is sensitive to Rtf1 dosage. (A–E) Dorsal views of cmlc2 expression in 24 hpf wild type and morphant embryos. Wild type embryos have an elongated primitive heart tube at 24 hpf (A), whereas embryos injected with 0.1 ng, 0.25 ng, and 1.5 ng of rtf1MO have no detectable cardiac tissue (B–D). Embryos coinjected with ctr9MO, cdc73MO, and paf1MO (3KD) have a small clump of cardiomyocytes situated at the midline (E). (F–J) Dorsal views of nkx2.5 expression in 16S stage wild type and morphant embryos. In wild type embryos, cardiac progenitors have been specified in the ALPM (F). Injection of rtf1MO produces a dosage-dependent effect on nkx2.5 expression. Embryos injected with 0.1 ng rtf1MO (G) have a reduction in nkx2.5 expression compared to wild type. Expression of nkx2.5 is further reduced in embryos injected with 0.25 ng rtf1MO (H), and absent in embryos injected with 1.5 ng rtf1MO (I). Simultaneous knockdown of ctr9, cdc73, and paf1 does not result in a phenotype as severe as that seen in rtf1 morphants. (K–O) Dorsal views of cmlc2 expression in 16S stage wild type and morphant embryos. Mature cardiomyocytes that express cmlc2 are beginning to be specified as early as the 16S stage in wild type embryos (K), but are not present in 0.1 ng, 0.25 ng, and 1.5 ng, rtf1MO and 3KD morphant embryos at this stage (L–O).