[5][6] This gene encodes a selenoprotein, which contains a selenocysteine (Sec) residue at its active site.

The selenocysteine is encoded by the UGA codon that normally signals translation termination.

The 3' UTR of selenoprotein genes have a common stem-loop structure, the sec insertion sequence (SECIS), that is necessary for the recognition of UGA as a Sec codon rather than as a stop signal.

Pathogenic Mutations in SEPN1 gene (SELENON) can cause the classical phenotype of multiminicore disease and congenital muscular dystrophy with spinal rigidity and restrictive respiratory syndrome known as SEPN1-related congenital muscular dystrophy or rigid spine syndrome.

Two alternatively spliced transcript variants encoding distinct isoforms have been found for this gene.