ANKRD1 expression is aberrantly upregulated in the mdm mouse model of muscular dystrophy and induced by stretch through NFκB

Abstract

The muscular dystrophy with myositis (mdm) mouse model results in a severe muscular dystrophy due to an 83-amino-acid deletion in the N2A region of titin, an expanded sarcomeric protein that functions as a molecular spring which senses and modulates the response to mechanical forces in cardiac and skeletal muscles. ANKRD1 is one of the muscle ankyrin repeat domain proteins (MARPs) a family of titin-associated, stress-response molecules and putative transducers of stretch-induced signaling in skeletal muscle. The aberrant over-activation of Nuclear factor Kappa B (NF-κB) and the Ankyrin-repeat domain containing protein 1 (ANKRD1) occurs in several models of progressive muscle disease including Duchenne muscular dystrophy. We hypothesized that mechanical regulation of ANKRD1 is mediated by NF-κB activation in skeletal muscles and that this mechanism is perturbed by small deletion of the stretch-sensing titin N2A region in the mdm mouse. We applied static mechanical stretch of the mdm mouse diaphragm and cyclic mechanical stretch of C₂C₁₂ myotubes to examine the interaction between NF−κΒ and ANKRD1 expression utilizing Western blot and qRTPCR. As seen in skeletal muscles of other severe muscular dystrophies, an aberrant increased basal expression of NF-κB and ANKRD1 were observed in the diaphragm muscles of the mdm mice. Our data show that in the mdm diaphragm, basal levels of NF-κB are increased, and pharmacological inhibition of NF-κB does not alter basal levels of ANKRD1. Alternatively, NF-κB inhibition did alter stretch-induced ANKRD1 upregulation. These data show that NF-κB activity is at least partially responsible for the stretch-induced expression of ANKRD1.