Selenoprotein M is expressed during bone development

25 selenoproteins that contain selenium, incorporated as selenocysteine (Sec), have been identified to date. Selenoprotein M (SELM) is one of seven endoplasmic reticulum (ER)-resident, Sec-containing proteins that may be involved in posttranslational processing of proteins and maintenance of ER function. Since SELM was overrepresented in a cartilage- and bone-specific expressed sequence tag (EST) library, we further investigated the expression pattern of Selm and its possible biological function in the skeleton. RNA in situ hybridization of Selm in chicken and mice of different developmental stages revealed prominent expression in bones, specifically in osteoblast, and in tendons. This result suggests that SELM functions during bone development, where it is possibly involved in the processing of secreted proteins.