a Experimental design. Siblings carrying the ptx3aRNTR allele and/or the tcf21:nucEGFP reporter were treated with 5 mM Mtz or vehicle (Ctrl) from 3 dpa to 5 dpa. b Whole mount images of hearts collected at 7 dpa. Dash lines denote the injury sites. Large blood clot and extra tissue were observed in hearts of Mtz treated NTR+ animals (13 of 14) but not in those from the vehicle-treated NTR+ fish (12 of 18) or Mtz treated NTR- fish (11 of 16). Scale bar, 200 μm. c Section images of injured ventricles from 3 treatment groups at 7 dpa. The epicardial cells are labeled with tcf21:nucEGFP (green). Nuclei were stained with DAPI (magenta). White dashed lines indicate the injury sites. Scale bar, 100 μm. d Quantification of EGFP+ cells in the wound region from experiments in c. From left to right, n = 8, 8, and 7, respectively. NS not significant. Two-tailed Student’s t test. e Section images of injured ventricles from 3 treatment groups at 7 dpa. Ventricular CM proliferation was assessed by anti-PCNA (green) and Mef2 (magenta) staining. Nuclei were stained with DAPI (blue). The framed regions are enlarged to show proliferating CMs (some denoted with arrowheads). f Quantified PCNA+ CM indices in injury sites in experiments from e. From left to right, n = 16, 16, and 14, respectively. NS, not significant. Two-tailed Student’s t test. g Section images of ventricles at 30 dpa stained with Acid Fuchsin-Orange G to characterize non-muscle components in the injuries (blue for collagen, red for fibrin). h Semiquantitative assessment of cardiac injuries based on muscle and scar morphology (robust, partial, or blocked regeneration). Data were analyzed using Fisher’s exact test. n = 13 for each treatment group. NS not significant. Box plots show the median (center line), upper and lower quartiles (box limits), minimum and maximum values (whiskers), and individual values (points). Source data are provided as a Source data file.

Knockout of chd7 caused developmental behavioral defects. (a,b) The line illustrates the 6 dpf zebrafish larvae’s swimming trajectory differences from the WT and chd7−/− groups evaluated over 1 h. ** p = 0.0021, unpaired Student’s two-tailed t-test. (c) Real-time Q-PCR results of motor neuron marker genes isl1 (*** p = 0.0007) and isl2a (*** p = 0.001). Data were shown as mean ± sem. unpaired Student’s two-tailed t-test. (d) Representative morphological image of embryos and analysis of malformation rate from the WT and chd7−/− groups at 3 dpf. Scale bar: 100 μm.

Mutation of ccdc57 results in planar polarity defects in ependymal cells.(A) Still images showing the beating direction of motile cilia to drive fluid flow (pink arrow) in adult wild type and mutants. The representative kymographs of cilia movement were shown at the bottom. (B) Scanning electron microscopy showing the multicilia of the ependymal cells in wild type and ccdc57 mutant. (C) Confocal images showing cilia of the ependymal cells in wild type and ccdc57 mutant as indicated. Cilia were labeled with anti-mono-glycylated tubulin in green and the tight junction were stained with Claudin-5 antibody in red. Nuclei were counterstained with DAPI. (D) Confocal images showing the basal body distribution in the ependymal cells of wild type and ccdc57 mutant as indicated. The basal bodies were labeled with anti-γ tubulin in green and cytoskeleton was stained with phalloidin in purple. Tight junctions were stained with Claudin-5 antibody in red. Nuclei were counterstained with DAPI. Arrows indicate the displacement of basal bodies from the center of the cells. The schematic diagram of the displacement of basal bodies were shown at the bottom. (E) Angular distribution of the basal bodies in ependymal cells from wild type and ccdc57 mutant. (F) Statistical analysis showing relative displacement distance of basal bodies from center of the cell. (G) Statistical analysis showing the number of basal bodies in each ependymal cell of wild type and ccdc57 mutant. BB, basal body. (H) Model illustrating the distribution of multicilia on ependymal cells of wild type and ccdc57 mutant. All the data analyzed in this figure are generated from 3- to 4-months-old adult zebrafish. Scale bars: 5 μm in panels B and D; 7.5 μm in panel C. The data underlying the graphs shown in the figure can be found in S1 Data.

Chd7 knockout mutant affected the myelin potential of OL. (a) The most posterior myelin sheath in the spinal cord at 80 hpf during myelination of the Mauthner axon between chd7+/+ and chd7−/− groups. Asterisks represent the terminals of myelin-coated axons. Scale bars:100 μm. (b) The most posterior myelin sheath at 70 hpf was somite 9 in the wild-type and somite 2 in mutant groups; at 75 hpf was somite 17 in the wild-type and somite 9 in mutant groups; and at 80 hpf was somite 25 in the wild-type and somite 15 in mutant groups. (c) Typical confocal imaging of individual oligodendrocytes labeled with plasmid mbp-EGFP-CAAX in the wild-type and mutant groups. Scale bar: 50 μm. (d) Number of individual oligodendrocyte-wrapped myelin segments in the wild-type and mutant groups. Wild type: 12 cells derived from 10 juveniles; mutant group: 16 cells derived from 9 juveniles. (e) Real-time Q-PCR results of gene olig2 and mbp. (f) Protein MBP was decreased in knockout group as shown by Western blot quantification. Data were shown as mean ± sem. **** p < 0.0001, unpaired Student’s two-tailed t-test.