Mechanotransduction via the LINC complex regulates DNA replication in myonuclei

Area of Science:

• Muscle biology
• Cell mechanics
• Molecular genetics

Background:

• Nuclear mechanotransduction influences chromatin organization, but its role in myofiber function is not fully understood.
• The linker of nucleoskeleton and cytoskeleton (LINC) complex is crucial for mechanical signal transmission.
• Controlled DNA endoreplication ensures uniform nuclear DNA content in myofibers.

Purpose of the Study:

• To investigate the impact of the LINC complex on DNA endoreplication in *Drosophila* larval muscles.
• To determine the role of mechanical signaling in regulating myonuclei DNA content.
• To identify downstream effectors of LINC-mediated mechanotransduction in muscle.

Main Methods:

• Genetic manipulation of LINC complex components (e.g., *klar* mutation) in *Drosophila* larval muscles.
• Knockdown of β-Integrin to perturb LINC-independent mechanical input.
• Genome-wide RNA-polymerase II occupancy analysis.
• Muscle-specific knockdown of barrier-to-autointegration factor (BAF).

Main Results:

• LINC complex disruption abolished synchronized DNA endoreplication, leading to variable DNA content in myonuclei.
• Perturbation of LINC-independent mechanical input also increased myonuclei DNA content.
• LINC complex mutations altered RNA-polymerase II binding, decreasing BAF and Troponin C occupancy.
• Muscle-specific BAF knockdown phenocopied LINC mutant effects on DNA content.

Conclusions:

• Mechanical stimuli transmitted through the LINC complex regulate synchronized cell-cycle progression of myonuclei.
• The barrier-to-autointegration factor (BAF) acts downstream of the LINC complex in this pathway.
• Nuclear mechanotransduction is essential for maintaining uniform DNA content in myofiber nuclei.