Defective excitation-contraction coupling is partially responsible for impaired contractility in hindlimb muscles of Stac3 knockout mice

Abstract

The Stac3 gene is exclusively expressed in skeletal muscle, and Stac3 knockout is perinatal lethal in mice. Previous data from Stac3-deleted diaphragms indicated that Stac3-deleted skeletal muscle could not contract because of defective excitation-contraction (EC) coupling. In this study, we determined the contractility of Stac3-deleted hindlimb muscle. In response to frequent electrostimulation, Stac3-deleted hindlimb muscle contracted but the maximal tension generated was only 20% of that in control (wild type or heterozygous) muscle (P < 0.05). In response to high [K+], caffeine, and 4-chloro-m-cresol (4-CMC), the maximal tensions generated in Stac3-deleted muscle were 29% (P < 0.05), 58% (P = 0.08), and 55% (P < 0.05) of those in control muscle, respectively. In response to 4-CMC or caffeine, over 90% of myotubes formed from control myoblasts contracted, but only 60% of myotubes formed from Stac3-deleted myoblasts contracted (P = 0.05). However, in response to 4-CMC or caffeine, similar increases in intracellular calcium concentration were observed in Stac3-deleted and control myotubes. Gene expression and histological analyses revealed that Stac3-deleted hindlimb muscle contained more slow type-like fibers than control muscle. These data together confirm a critical role of STAC3 in EC coupling but also suggest that STAC3 may have additional functions in skeletal muscle, at least in the hindlimb muscle.

STAC3variants cause a congenital myopathy with distinctive dysmorphic features and malignant hyperthermia susceptibility

“…The functional data strongly support the notion that the STAC3 variants lead to impaired ECC. Indeed, application of KCl caused a small release of sarcoplasmic reticulum Ca 2+ , a result consistent with previous observations in animal models (Cong, Doering, Grange, & Jiang, ; Linsley, Hsu, Groom, et al., ; Nelson et al., ; Polster et al., ). Our results, however, are not fully supportive of previously published data on Ca 2+ release mediated by direct RyR1 activators.…”

Clinicopathologic Conference: A Newborn With Hypotonia, Cleft Palate, Micrognathia, and Bilateral Club Feet

“…It is an important component in excitation-contraction coupling because of direct involvement in conformational coupling between slow activating calcium channels and the type 1 ryanodine receptor 13 . STAC3 knockout mice die at birth, and mice with STAC3 knocked out at age 4 weeks have reduced muscle mass and muscle strength 14 . Although the specific mechanism resulting in the histopathologic finding is not clear, CFTD has been previously described in muscle biopsies from NAM patients.…”

RNA-Sequencing Reveals Upregulation and a Beneficial Role of Autophagy in Myoblast Differentiation and Fusion

“…Quantitative PCR of 20 ng cDNA was performed in duplicate using Fast SYBR Green Master Mix on a 7500 Fast Real-Time PCR system (Applied Biosystems). The PCR primers used in this study were designed in a previous study [ 41 ]. Relative gene expression levels were calculated using the ∆∆Ct method [ 42 ], using the HMBS gene as a reference gene, which, based on its Ct value (data not shown), was stably expressed in C2C12 cells during differentiation.…”