Fig. 4

Isl2b controls the expression of key regulators of cardiogenesis.

(a,b) Relative mRNA expression of the Isl1 direct targets, Mef2c, Hand2 and Tbx20 in control and Isl1 knockdown mouse ES cells-derived embryoid bodies after 5 days of differentiation, a stage enriched in cardiac progenitors (a) and in dissected SHF of E9.25 Isl1 knockout mouse embryos (b). (c) In situ hybridization for isl1, isl2a and isl2b expression in zebrafish embryos at the 10 somite stage. (d) Transverse sections after in situ hybridization for isl1, isl2a and isl2b (c) counterstained with Sytox Green and imaged with a confocal microscope. Arrows point to isl1 and isl2b expressing cells in the cardiogenic region of the ALPM and in the TG (trigeminal placodes). Isl2a expression is observed in the periderm (arrowhead). Scale bars, 100 μm. (e) In situ hybridization for hand2, mef2ca, mef2cb, tbx20, nkx2.5 and tbx5a expression in control, isl2a−/− and isl2b−/− zebrafish embryos at the 10 somite stage. Data information: In (a,b), data are presented as mean ± SEM. *p ≤ 0.05, **p ≤ 0.01 (Student’s t-test).