Muscleblind Like Protein 3 (MBNL3)

Myotonic dystrophy (DM1) is a complex neuromuscular disorder associated with DNA expansion mutations in 2 different genes. In DM1 a CTG repeat in the 3-prime-untranslated region of DMPK is expanded, whereas in DM2 an intronic CCTG expansion occurs in the gene ZNF9. Transcripts containing expanded repeats form foci in the nuclei of DM1 and DM2 cells. Proteins related to Drosophila muscleblind (MBNL) colocalized with repeat foci in DM1 and DM2 cells.

MBNL and MBLL were expressed in many adult tissues, whereas MBXL was expressed predominantly in the placenta. Green fluorescent protein-tagged versions of MBNL, MBLL, and MBXL colocalized with nuclear foci in DM1 and DM2 cells, suggesting that all 3 proteins may play a role in DM pathophysiology.