Alteration of T-Tubular Architecture and Capacitance Changes in Huntington's Disease
Huntington's disease (HD) is an inherited disorder with debilitating motor, cognitive, and psychiatric dysfunction. Motor symptoms, including chorea, rigidity, dystonia, and weakness, have principally been attributed to central neurodegeneration, but recent work suggests that primary skeletal muscle defects may also contribute to the motor symptoms. Electrophysiology studies in our lab have revealed a marked decrease in specific capacitance in HD muscle fibers from R6/2 transgenic mice compared with controls. This reduced capacitance is greater than expected when accounting for the smaller size of HD fibers. Because the transverse tubular system (TTS) in skeletal muscle makes up a significant proportion of total cell membrane, we hypothesized that structural changes in the TTS were responsible for reduced capacitance in the disease state. A loss or disruption of membrane in the TTS could directly contribute to weakness in HD. Decreased t-tubule diameters in HD fibers without changes in overall cellular TTS density were confirmed using quantitative electron and confocal microscopy. Here, we present results of calculations based on a cylindrical model of skeletal muscle incorporating these changes in muscle fiber and TTS architecture that account for reduced specific capacitance in HD. These results may help our understanding of muscle function in HD and provide a foundation for modeling electrical activity in disease and normal skeletal muscle.
Metzger, S. K.,
Rich, M. M.,
& Voss, A. A.
(2019). Alteration of T-Tubular Architecture and Capacitance Changes in Huntington's Disease. Biophysical Journal, 116 (3), 406A.