This gene encodes a large membrane-bound glycoprotein which is a member of the mucin family. Mucins are O-glycosylated proteins that play an essential role in forming protective mucous barriers on epithelial surfaces. These proteins also play a role in intracellular signaling. The encoded protein contains an N-terminal signal sequence, an extracellular mucin domain, a stem domain, a transmembrane domain, and a C-terminal cytoplasmic tail domain. The mucin domain contains O-glycosylation sites and is polymorphic with isoforms containing a variable number of nonidentical proline-, threonine-, and serine-rich tandem repeats of 15 amino acids each. The aberrent expression of this gene is associated with lung adenocarcinoma. [provided by RefSeq, May 2017]
Forensic Context
A study in humans demonstrated that the MUC21 mRNA, used for vaginal secretion identification, exhibited cross-reactivity with saliva and menstrual blood and contained a microhaplotype where severe heterozygous imbalance was observed in complex mixtures [Yu et al. DOI:10.1016/j.fsigen.2025.103416].