Ion channels as biomarkers of altered myogenesis in myofiber precursors of Duchenne muscular dystrophy.

Myogenesis is essential for skeletal muscle formation, growth, and regeneration and can be altered in Duchenne muscular dystrophy (DMD), an X-linked disorder due to the absence of the cytoskeletal protein dystrophin. Ion channels play a pivotal role in muscle differentiation and interact with the dystrophin complex. To investigate ion channel involvement in myogenesis in dystrophic settings, we performed electrophysiological characterization of two immortalized mouse cell lines, wild-type (WT) H2K-2B4 and the dystrophic (DYS) H2K-SF1, and measured gene expression of differentiation markers and ion channels. Inward and outward currents/density increased as differentiation progressed in both WT and DYS cells. However, day-11 DYS cells showed higher (27%) inward current density with an increased expression ratio of Scn5a/Scn4a and decreased (48%) barium-sensitive outward current compared to WT. Furthermore, day-11 DYS cells showed more positive resting membrane potential (+10 mV) and lower membrane capacitance (50%) compared to WT. DYS cells also had reduced Myog and Myf5 expression at days 6 and 11. Overall, ion channel profile and myogenesis appeared altered in DYS cells. These results are a first step in validating ion channels as potential drug targets to ameliorate muscle degeneration in DMD settings and as differentiation biomarkers in innovative platforms.

LKB1 signaling is altered in skeletal muscle of a Duchenne muscular dystrophy mouse model.

The potential role of liver kinase B1 (LKB1) in the altered activation of the master metabolic and epigenetic regulator adenosine monophosphate-activated protein kinase (AMPK) in Duchenne muscular dystrophy has not been investigated so far. Hence, we analyzed both gene and protein levels of LKB1 and its related targets in gastrocnemius muscles of adult C57BL/10 mdx mice and D2 mdx mice, a model with a more severe dystrophic phenotype, as well as the sensitivity of the LKB1-AMPK pathway to AMPK activators, such as chronic exercise. Our data show, for the first time, a reduction in the levels of LKB1 and accessory proteins, MO25 and STRADα, in both mdx strains versus the respective wild type, which was further impaired by exercise, in parallel with a lack of further phosphorylation of AMPK. The AMPK-like kinase salt-inducible kinase (SIK) and class II histone deacetylases, along with expression of the HDAC target gene Mef2c, were also altered, supporting an impairment of LKB1-SIK-class II histone deacetylase signaling. Our results demonstrate that LKB1 may be involved in dystrophic progression, paving the way for future preclinical studies.