Proper localization and anchorage of nuclei within skeletal muscle is critical for cellular function. Alterations in nuclear anchoring proteins modify a number of cellular functions including mechanotransduction, nuclear localization, chromatin positioning/compaction and overall organ function. In skeletal muscle, nesprin 1 and desmin are thought to link the nucleus to the cytoskeletal network. Thus, we hypothesize that both of these factors play a key role in skeletal muscle function. To examine this question, we utilized global ablation murine models of nesprin 1, desmin or both nesprin 1 and desmin. Herein, we have created the nesprindesmindouble- knockout(DKO)mouse, eliminatingamajor fractionof nuclear-cytoskeletal connectionsandenabling understanding of the importance of nuclear anchorage in skeletal muscle. Globally,DKOmice are marked by decreased lifespan, body weight and muscle strength. With regard to skeletal muscle, DKO myonuclear anchorage was dramatically decreased compared with wild-type, nesprin 12/2 and desmin2/2 mice. Additionally, nuclear-cytoskeletal strain transmission was decreased in DKO skeletal muscle. Finally, loss of nuclear anchorage inDKOmice coincided with a fibrotic response as indicated by increased collagen and extracellular matrix deposition and increased passive mechanical properties of muscle bundles. Overall, our data demonstrate that nesprin 1 and desmin serve redundant roles in nuclear anchorage and that the loss of nuclear anchorage in skeletal muscle results in a pathological response characterized by increased tissue fibrosis and mechanical stiffness.
ASJC Scopus subject areas
- Molecular Biology