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Fig. 1
Specification of gata4+ and nkx2.5+ SHF myocardial progenitors in the zebrafish ALPM. (A,B) Driver and reporter transgenes employed for inducible Cre/loxP-mediated myocardial lineage tracing of gata4+ and nkx2.5+ ALPM cells. (C) Experimental strategy. Double transgenic embryos were exposed continuously (’Cont.’) to 10 µM 4-OHT or solvent alone (ethanol) between 8 and 72 hpf. Alternatively, embryos were exposed transiently (’Pulsed’) to 4-OHT or ethanol between 8 hpf (75% epiboly) and the 14- to 16-somite stages prior to extensive rinsing with embryo medium (E3). All embryos were analyzed and imaged at 72 hpf for cardiac ZsYellow reporter fluorescence. (D,G) Hearts in Tg(gata4:ERCreER); Tg(cmlc2:CSY) embryos treated continuously (D) or transiently (G) with ethanol. (E,H) Hearts in Tg(gata4:ERCreER); Tg(cmlc2:CSY) embryos treated continuously (E) or transiently (H) with 4-OHT. (F,I) Hearts in Tg(nkx2.5:ERCreER); Tg(cmlc2:CSY) embryos treated continuously (F) or transiently (I) with 4-OHT. Hpf, hours post-fertilization; ss, somite stage; V, ventricle; OFT, outflow tract; EtOH, ethanol; 4-OHT, 4-hydroxytamoxifen.