The ALT-LINC complex mediates cellular responses to matrix mechanics

Nuclear Envelope Membrane Protein 1 (NEMP1) is crucial for metazoan fertility; loss of Nemp1 causes primordial oocyte death, residing in the mechanically challenging ovarian cortex. Here, we show that softening the ovary rescues oocyte loss and restores fertility in NEMP1 knockout mice. In cell culture, NEMP1 depletion on stiff substrates leads to death, while cells remain viable on soft substrates. We further show that NEMP1 regulates YAP nuclear translocation, essential for mechanotransduction. Mechanistically, Nemp1-depleted cells on stiff substrates or subjected to stretching exhibit reduced nuclear YAP localization, and expressing nuclear YAP5SA restores cell viability. Loss of NEMP1 disrupts actin organization, inhibiting YAP nuclear translocation. Inducing actin polymerization rescues nuclear YAP, indicating an F-actin-dependent mechanism for NEMP1-mediated mechanotransduction. NEMP1 forms a novel complex with NESPRIN2's KASH domain, strengthening the actin cytoskeleton to withstand mechanical forces, independently of SUN proteins. Thus, NEMP1-Nesprin complex, named hereafter ALT-LINC, creates a mechanosensitive pathway parallel to the LINC complex and is crucial for YAP mechanotransduction, enabling cellular response to mechanical stress in vitro and in vivo.