Calsequestrins in skeletal and cardiac muscle from adult Danio rerio.

All vertebrates have multiple genes encoding for different CASQ isoforms. Increasing interest has been focused on mammalian and human CASQ genes since mutations of both cardiac (CASQ2) and skeletal (CASQ1) isoforms cause different, and sometime severe, human pathologies Danio rerio (zebrafish) is a powerful model for studying function and mutations of human proteins. In this work expression, biochemical properties and cellular and sub-cellular localization of Danio rerio native CASQ isoforms are investigated. By quantitative PCR three mRNAs were detected in skeletal muscle and one mRNA in heart. Three zebrafish CASQs were identified by mass spectrometry and they share properties with mammalian skeletal and cardiac CASQs. Skeletal calsequestrins were found primarily, but not exclusively, at the sarcomere Z-line level where Terminal Cisternae of Sarcoplasmic reticulum are located.