CLCN1 and myotonic dystrophy type 1: Therefore, it is reasonable to expect that observations from bi-channelopathy mice may apply most directly to DM1 muscles that exhibit a near-complete loss of ClC-1 and levels of CaV1.1 e29 skipping approaching or exceeding heterozygous CaV1.1Δe29 mice, and this clearly does occur in distal limb muscles that are preferentially affected, such as tibialis anterior (10).