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Expression patterns of transcriptional regulators and cardiomyocyte numbers and are disturbed in the ALPM at mid-somitogenesis stages.(A) Wholemount preparations of control and MZjnk1a/MZjnk1b embryos expressing myl7:gfp transgene. Differentiated cardiomyocytes identified using anti-gfp antibody to detect myl7;gfp expression and DAPI to identify nuclei. Reduction in number of cardiomyocyte nuclei at 12ss (B) and 16ss (C) in MZjnk1a/MZjnk1b in comparison to control embryos. (D) Tracks of cardiomyocytes migrating to form the heart cone in control and MZjnk1a/MZjnk1b embryos. (E) speed, (F) velocity and (G) wander index. (H) Ventricular cardiomyocytes migrating through the anterior lateral plate mesoderm (ALPM) to form the heart are visualised by WISH for myh7. The distribution of cells is identical to the wildtype pattern in MZjnk1a null mutants between 14ss and 22ss stages. However at 27hpf the ventricular component of the extended primary heart tube is shorter in MZjnk1a null mutants than controls. (I) WISH showing expression patterns of nkx2.5, gata4 and hand2 transcription factors in MZjnk1a/MZjnk1b and control embryos at the 10ss. There are no differences between expression patterns of nkx2.5 or gata4 between MZjnk1a/MZjnk1b and control embryos. However, although the anterior exent of hand2 expression is unchanged, there is a reduction in the posterior expression of hand2 (arrowheads). (J) Area of nkx2.5, gata4 and hand2 gene expression at the 10ss. Only the area of the hand2 expression is significantly different between MZjnk1a/MZjnk1b and control embryos. *** = p<0.001. *** = p<0.001, ns = not significant.
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