Copper ions impair zebrafish skeletal myofibrillogenesis via epigenetic regulation

Abstract

Unbalanced copper (Cu2+) homeostasis is associated with the developmental defects of vertebrate myogenesis, but the underlying molecular mechanisms remain elusive. In this study, it was found that Cu2+ stressed zebrafish embryos and larvae showed reduced locomotor speed as well as loose and decreased myofibrils in skeletal muscle, coupled with the downregulated expression of muscle fiber markers mylpfa and smyhc1l and the irregular arrangement of myofibril and sarcomere. Meanwhile, the Cu2+ stressed zebrafish embryos and larvae also showed significant reduction in the expression of H3K4 methyltransferase smyd1b transcripts and H3K4me3 protein as well as in the binding enrichment of H3K4me3 on gene mylpfa promoter in skeletal muscle cells, suggesting that smyd1b—H3K4me3 axis mediates the Cu2+‐induced myofibrils specification defects. Additionally, whole genome DNA methylation sequencing unveiled that the gene smyd5 exhibited significant promoter hyper‐methylation and increased expression in Cu2+ stressed embryos, and the ectopic expression of smyd5 in zebrafish embryos also induced the myofibrils specification defects as those observed in Cu2+ stressed embryos. Moreover, Cu2+ was shown to suppress myofibrils specification and smyd1b promoter transcriptional activity directly independent of the integral function of copper transporter cox17 and atp7b. All these data may shed light on the linkage of unbalanced copper homeostasis with specific gene promoter methylation and epigenetic histone protein modification as well as the resultant signaling transduction and the myofibrillogenesis defects.

Zebrafishcox17modulates primitive erythropoiesis via regulation of mitochondrial metabolism to facilitate hypoxia tolerance

“…Embryos were observed and photographed under a stereoscopic microscope (Leica M205FA, Germany), and the signal area in each image was calculated by Image J software. Embryos with changes in the expression of the tested genes were identified and their percentage was calculated as we reported previously 46,47,49 …”

“…The pellet was re‐suspended in water and used as a template for qPCR. The tested genes and their primers used for ChIP‐qPCR are listed in Table S4, and qPCR and data analysis were performed as recently reported 46,47 …”

“…After sonication, the input control, TCF4, H3K27me3, and IgG (negative control) ChIP groups were treated as described previously. 46,47 Finally, the ChIP DNA was recovered by phenol/chloroform/isoamylal-cohol (25:24:1) extraction and precipitated by ethanol. The pellet was re-suspended in water and used as a template for qPCR.…”

“…Embryos with changes in the expression of the tested genes were identified and their percentage was calculated as we reported previously. 46,47,49…”

“…The tested genes and their primers used for ChIP-qPCR are listed in Table S4, and qPCR and data analysis were performed as recently reported. 46,47…”