Effects of stanniocalcin 1 on calcium uptake in zebrafish (Danio rerio) embryo

Stanniocalcin (STC) formerly called hypocalcin or teleocalcin, is a 50-kDa disulfide-linked homodimeric glycoprotein that was originally identified in fish and secreted from the corpuscles of Stannius (CS). One of the main functions of STC-1 is Ca²⁺ uptake inhibition; however, the mechanisms remain unknown. In the present study, we provide molecular evidence to elucidate how zebrafish STC-1 regulates Ca²⁺ uptake in zebrafish embryos. In a wide variety of tissues including the kidney, brain, gill, muscle, and skin, zstc-1 was expressed. Incubating zebrafish embryos in low-Ca²⁺ (0.02 mM) freshwater stimulated whole body Ca²⁺ influx and zebrafish epithelial Ca²⁺ channel (zECaC) mRNA expression, while downregulated zstc-1 expression. A morpholino microinjection approach was used to knockdown the zSTC-1 protein, and the results showed that the Ca²⁺ content, Ca ²⁺ influx, and zECaC mRNA expression all increased in morphants. These data suggest that zSTC-1 negatively regulates ECaC gene expression to reduce Ca²⁺ uptake in zebrafish embryos.