Natural history of a mouse model of X-linked myotubular myopathy

Abstract

X-linked myotubular myopathy is a severe monogenetic disorder of the skeletal muscle caused by loss of expression/function mutations in the MTM1 (myotubularin) gene. There is a growing understanding of the pathologic and molecular abnormalities associated with loss of MTM1, and emerging therapeutic strategies that are in the process of translation to patients. Much of these data have been uncovered through experimentation in pre-clinical animal models of the disease. The most widely used model is an Mtm1 gene knockout mouse line; this line faithfully recapitulates the salient genetic and pathologic features of the disease. Despite the advances in aspects of XLMTM, there remain many unknowns related to disease pathomechanisms and to understanding of MTM1s function in normal muscle development, and a continued need for therapy identification and development. To address these barriers, and to lay the groundwork for future study, we performed a natural history study of the Mtm1 knockout mouse model of XLMTM. We show that certain molecular and pathologic changes precede overt phenotypic changes, while others, including abnormalities in triad structure, occur more coincident with muscle weakness in the mouse. In total, we provide a comprehensive longitudinal assessment of molecular and structural features of the murine XLMTM disease process.