Fig. 5: Developmental and electrophysiological phenotypes in F0 crispants and F2 mutants.

A Workflow including zygotic microinjections using an HdrR (myl7::eGFP; myl7::H2A-mCherry) reporter line and phenotyping of cardiac-affected crispants 4 days post-fertilization (dpf). B Representative cardiac phenotypes of knockout embryos for all six candidate genes targeted with CRISPR-Cas9 and base editor compared to a control embryo at 4 dpf; bright-field overview of the injected specimen (top; scale bar, 500 µm), close-up image of the heart (bottom; scale bar, 125 µm); cf. movie S2. C Immunostaining of regulatory myosin light chain (myl7) in crispants of btbd1 (n = 5 embryos), blzf1 (n = 6 embryos), and adprhl1 (n = 7 embryos) at 4 days post-fertilization (4dpf) in Cab. In btbd1 and adprhl1 mosaic knockout, the myosin signal is reduced and sarcomeric structure disturbed (filled arrowhead) compared to blzf1, which shows no differences in contrast to control (n = 2 embryos) (unfilled arrowhead); (scale bar, 10 µm). D Heart rhythm analysis in F0 crispants and F2 mutants as depicted by kymographs derived from atrium (A) to ventricle (V) spanning line selection in 10 s time-lapse movies (scale bar, 500 µm). In contrast to the regular rhythm in the control embryo (left), the representative rrad, blzf1, and adprhl1 F0 crispant and F2 mutants (right) display different degrees of atrioventricular block; cf. movie S4. Schemes are adapted from a previous publication²⁰ under a CC BY 4.0 Creative Commons licence.