VP.83 Ion channels and myogenesis in Duchenne muscular dystrophy: Electrophysiological profile of wild-type and dystrophic myoblasts and myocytes

Abstract

In skeletal muscle, several ion channels interact with the dystrophin complex, which is disrupted in Duchenne muscular dystrophy (DMD). However, little is known about their involvement in myogenesis in DMD. Here, we performed a pilot study to characterize the electrophysiological asset of myoblasts and myocytes at day 2/4/6/11 by using two immortalized mouse satellite-derived cell lines: the wild-type 2B4 and the dystrophic SF1. We evaluated both inward and outward currents at different time points of differentiation by whole-cell patch clamp. 2B4 cells showed an increment of inward currents as the differentiation program progresses. In SF1 myocytes, inward currents increased up to the 6th day of differentiation, like in 2B4 cells. However, day-11 SF1 myocytes showed 50% lower inward currents compared to day-11 2B4 myocytes (5.2 nA vs 2.8 nA at -20 mV). High concentration of tetrodotoxin blocked these inward currents in both day-6 and day-11 2B4/SF1. Outward currents were clearly detectable in day-11 2B4 cells but very small in day-2/4/6 2B4 cells. Conversely, SF1 outward currents reached the highest value at day-6, being 3-fold higher than 6-day 2B4 cells (733 pA vs 283 pA at +60 mV). However, day-11 SF1 myocytes showed 44% lower outward currents, compared to day-11 2B4 cells (722 pA vs 1283 pA). BaCl₂ decreased outward currents in day-6 2B4/SF1 cells and in day-11 2B4 myocytes. In addition, we assessed resting membrane potentials which became more negative as the days of differentiation increased in both cell-lines. However, day-11 SF1 cells had a more depolarised membrane potential, compared to day-11 2B4 myocytes. This preliminary data suggests that during myogenesis, intrinsic impairments in ion channel development are disclosed by dystrophic conditions, likely in relation to the primary defect. Furthermore, electrophysiological characterization of human wild-type and dystrophic myoblasts/myocytes is on-going.