Predicted to enable protein folding chaperone; protein-folding chaperone binding activity; and unfolded protein binding activity. Acts upstream of or within several processes, including myofibril assembly; negative regulation of response to endoplasmic reticulum stress; and skeletal muscle organ development. Located in nuclear envelope. Is expressed in Purkinje cell; heart; lens; and solid lens vesicle. Human ortholog(s) of this gene implicated in autosomal dominant limb-girdle muscular dystrophy type 1. Orthologous to several human genes including DNAJB6 (DnaJ heat shock protein family (Hsp40) member B6); DNAJB7 (DnaJ heat shock protein family (Hsp40) member B7); and DNAJB8 (DnaJ heat shock protein family (Hsp40) member B8).