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FIGURE 4. IGFBP-4 is required for the maturation of the heart in Xenopus embryos. a, In situ hybridization analysis of Nkx2.5 (an early cardiac marker), cTnI (a mature cardiac marker), Hex (a liver marker), and XIGFBP-4 (XBP4) mRNA expression at stages 34, 38 and 42. b, Knockdown of XIGFBP-4 by two different morpholinos (MO1 and MO2) resulted in severe cardiac defects as assessed by cTnIin situ hybridization at stage 42 (left). These cardiac defects were rescued by simultaneous injection of MO-resistant wild-type XIGFBP-4, mutant XIGFBP-4-H74P (BP4(H74P) and LRP6N (n = 30 for each group). c, Temporal profile of cardiac defects induced by XIGFBP-4 knockdown. Morphology of the heart as assessed by cTnI in situ hybridization was almost normal at stage 34 but was severely perturbed at stages 38 and 42. The right column shows sections of control and MO-injected embryos. The arrow indicates the heart in control embryos. No heart-like structure was observed in MO-injected embryos. |
