MCOLN2 and deafness: Compared to TRPML1 and TRPML2, TRPML3 is more restrictively expressed, mainly in hearing system and melanocytes.42 Similar to TRPML2, TRPML3 is expressed in the endosomes and lysosomes and regulates endocytosis, membrane trafficking, and autophagy.67 Moreover, TRPML3 may be expressed in the plasma membrane as well.67 Mouse gain-of-function mutants of TRPML3 (varitint-waddler mutations) are associated with deafness, circling behaviors, and coat color dilution.113,122