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 Ca(2+) uptake inhibition; however the mechanisms remain unknown. In the present study, we provide molecular evidence to elucidate how zebrafish STC-1 regulates Ca(2+) uptake in zebrafish embryos. zstc-1 was expressed in a wide variety of tissues including the kidney, brain, gill, muscle, and skin. Incubating zebrafish embryos in low-Ca(2+) (0.02 mM) freshwater stimulated whole-body Ca(2+) influx and zebrafish epithelial Ca(2+) channel (zECaC) mRNA expression while down-regulated zstc-1 expression. A morpholino microinjection approach was used to knockdown the zSTC-1 protein, and the results showed that the Ca(2+) content, Ca(2+) influx, and zECaC mRNA expression all increased in morphants. These data suggest that zSTC-1 negatively regulates epithelial Ca(2+) channel (ECaC) gene expression to reduce Ca(2+) uptake in zebrafish embryos. Key words: Stanniocalcin, zebrafish, Ca2+ influx, ECaC.