Fig. 2

Cadm4 Activity Limits OFT Size

(A–D) Reduced cadm4 function results in an enlarged OFT.

(A and B) Lateral views of embryos at 48 hpf. Injection of an anti-cadm4 MO (B) does not disrupt general embryonic morphology.

(C and D) Hearts at 48 hpf, as in Figure 1A. Compared with the normal length of the OFT (bracket, C) in control sibling embryos, the OFT in cadm4 morphants is abnormally elongated (bracket, D).

(E–H) Elevated levels of cadm4 function result in reduced OFT size.

(E and F) Lateral views of embryos at 26 hpf. Injection of cadm4 mRNA (F) causes slight shortening of the body axis.

(G and H) Hearts at 48 hpf, as in (C). Rather than exhibiting normal OFT size (bracket, G), embryos injected with cadm4 mRNA exhibit very little OFT tissue (bracket, H).

(I) Number of ventricular, atrial, and OFT CMs in control and cadm4 morphant hearts at 48 hpf; the graph displays mean and SD for each data set. Although the numbers of ventricular and atrial CMs are unaffected in cadm4 morphants, the OFT in cadm4 morphants has more CMs than the OFT in control siblings (p < 0.0005; n = 5).

(J–R) Single confocal slices through Tg(myl7:EGFP);Tg(myl7:DsRedt4) hearts at 48 hpf, arterial pole up. These transgenes can distinguish early-differentiating CMs (EGFP and DsRed) from late-differentiating CMs (EGFP only, dotted outlines). Compared with controls (J–L), cadm4 morphants have an excess of late-differentiating CMs (M–O), and embryos injected with cadm4 mRNA have a deficit of late-differentiating CMs (P–R).

Scale bars, 300 μm in (A) and (E), 50 μm in (D), (H), and (P). See also Figure S2 and Movies S1 and S2.