Abstract Body: Objective: Mammalian cardiomyocytes (CMs) mature and develop compact sarcomeric structures, which act as a structural barrier and inhibit CM division. YAP-induced proliferating adult CMs undergo a dedifferentiation process to reverse maturation and reorganize the sarcomere, facilitating CM division. However, the regulation and coordination of this transition remain poorly understood.
Methods and Results: We examined cytoskeletal protein expression during CM maturation and observed that α-tubulin and microtubule-associated gene expression significantly decreased in adult CMs compared to neonatal CMs, along with a reduction in microtubule networks. Conversely, YAP overexpression increases α-tubulin expression and promotes the growth of the microtubule network during the process of CM dedifferentiation in adult mice. The densification of microtubule networks is essential for YAP-induced adult CM proliferation, dedifferentiation, and sarcomere breakdown, as treating CMs with the microtubule destabilizer colchicine significantly blocks these YAP-induced processes. Mechanistically, live imaging analysis of microtubule dynamics revealed that YAP overexpression in CMs leads to microtubule densification, characterized by increased polymerization and decreased depolymerization. Furthermore, the YAPS94A mutation, which disrupts the YAP and TEAD interaction, significantly reduces YAP-induced microtubule growth, indicating this YAP-induced microtubule growth depends on its transcriptional activity. Cut&Run and qRT-PCR analyses identified direct YAP target genes involved in microtubule organization, including Tpx2, Ckap5, and Dst. Overexpression of Tpx2 is sufficient to induce microtubule growth in adult CMs.
Conclusions: We identified a YAP-microtubule regulatory axis in which YAP reduces microtubule dynamics and promotes microtubule network growth in adult CMs, a process essential for adult CM dedifferentiation, sarcomere reorganization, and proliferation.