Fig. 4

Up regulation of RA may result in increased heart rhythm in cxcr4a mutants (A, B) Tg(cmlc2: GFP) transgenic embryos are treated with DMSO (as control) or low dose of RA (10−9 M) from 4hpf to 24hpf, no distinct heart size is showed from 48hpf to 4dpf (A), but some of embryos display mild pericardial effusion and erythrocyte remaining (B). (C) Statistical analysis for the embryos displaying erythrocyte remaining in 3 dpf after treating with low dose of RA. (D) In situ hybridization of nkx2.5 at 10SS in embryos treated with low dose of RA, showing the expression of nkx2.5 is mild down-regulated (E) Embryos treated with low dose of RA display mild rapid heart rate. (F) Expression of myl7 shows that RA treatment restricts progenitor cells during gastrula. (G) Statistical map for the area of myl7 expression. (H) Heart rate in embryos treated with low dose of RA according to different time windows (sphere to bud, bud to 24hpf, or sphere to 24hpf). It indicates that, from sphere to 24hpf, all the stages are required when RA regulating heart rhythm in zebrafish. (I) BMS treatment partially rescues hear rate in cxcr4a−/− embryos. In C, Error bars indicate standard deviation of the mean. *P＜0.05. In E, H and I, Line chart graphs represent average heart rate. Error bars indicate standard deviation of the mean. Unit: beats per minute. Bar, 50 μm.