Fig. 1

Generation and validation of nrg1^nc26 allele. (A) Gene structure of zebrafish nrg1 (exons drawn to scale). Alternative splicing produces three primary isoforms, nrg1‐I, nrg1‐IIa‐c and nrg1‐III. (B, C) CRISPR/Cas9 targeting at Exon 6 produced the nrg1^nc26 allele with a four amino acid deletion. (D) Detection of nrg1 mRNA transcripts spanning Exons 6–10 by qPCR; statistical significance determined by t‐test, *P < 0.05. (E) Representative nrg1^wt and nrg1^nc26/nc26 clutchmates stained with Mitotracker Red to detect neuromasts in the developing lateral line at 4–5 dpf. Red arrows designate neuromasts. (E’) Relative frequency of the number of neuromasts counted in embryos from heterozygous incrosses of nrg1^wt/nc26 fish, N > 24 larvae. (F‐G’) Representative confocal optical mid‐chamber slice of the ventricle at 3–4 dpf in larvae carrying Tg(myl7:rasGFP) cardiomyocyte reporters and treated with DMSO or 3.75 μM ErbB2 inhibitor PD168393. Boxes include high‐resolution image of the outer curvature. Red arrows point to developing trabeculae.