Fig. 5. Impaired OFT cushion growth in Bmpr2^E2/E2 mutants. (A-D) Sagittal sections at E11.5 show that the conotruncal ridges (arrow) form in the mutant (B), but not to the extent that they do in the wild type (A). (C,D) Higher magnifications of the boxed areas in A,B, respectively. (E-G) Immunostaining for PCNA in OFT cushions of E11.5 wild type (E) and a mutant (F,G) littermate. The arrowheads indicate the myocardium. (H) Tbx1 expression at E10.5 in a Bmpr2^E2/E2 mutant is found in the posterior part of the otic vesicle (ov), head mesenchyme (hm) and the mesenchyme surrounding the paired dorsal aortae (pm), as well as the dorsal wall of the aortic sac, with higher intensity in the posterior-most region (arrowheads) as described in wild type (Garg et al., 2001; Merscher et al., 2001; Vitelli et al., 2002). Anterior is towards the left and ventral towards the top. paI, pharyngeal arch I; Ve, ventricle; lb, left anterior limb bud. (I,J) Pax3 expression in neural crest cells (arrowhead) migrating in the neck region at E10.5 was normal in mutants (I, wild type; J, mutant). Pharyngeal arches are numbered in Roman numerals. Ve, ventricle. (K,L) Smooth muscle actin-positive neural crest cells (arrows) reach the outflow tract endocardial ridges in both the wild type (K) and mutant (L) E11.5 embryos. (M,N) At E13.5, in wild type embryos, Ctgf expression was detected in the pulmonary trunk and aorta, predominantly in the cell layers closer to the lumen, as well as in a punctate pattern in the ventricles (M). Myocardial expression is predominantly in the trabecular zone of the ventricles. Expression was not modified in mutants (N). (O,P) The expression of periostin, a BMP-regulated gene, was downregulated in the endocardial ridges of E11.5 mutants (P) compared with wild-type littermates (O). To help visualize the tissues in absence of background expression, P is an overlay of two different light exposures of the same section.

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