MTMR12 (myotubularin related protein 12) is a catalytically inactive lipid phosphatase that functions as a critical adapter protein for the myotubularin (MTM1) phosphatase complex. MTMR12 lacks the conserved HCX(5)R catalytic motif characteristic of active phosphatases 1 but forms functional heteroligomers with MTM1 through direct protein-protein interactions 2. This interaction stabilizes MTM1 protein levels and regulates its intracellular localization from the plasma membrane to the cytosol 3, which is essential for skeletal muscle maintenance and normal myotubule organization 2. Loss of MTMR12 results in reduced MTM1 stability and pathological muscle changes including central nucleation, myofiber hypotrophy, and disorganized triads similar to X-linked myotubular myopathy 2. Clinically, MTMR12 variants have been identified as genetic modifiers influencing disease susceptibility in α1-antitrypsin deficiency through autophagy regulation 4 and in a genome-wide association study as a locus associated with estimated glomerular filtration slope decline and chr5 kidney disease risk in East Asian populations 5. These findings suggest MTMR12 participates in proteostasis pathways beyond skeletal muscle, with potential therapeutic implications for stabilizing the MTM1-MTMR12 complex in myopathies.