Redundant YAP and TAZ functions are essential for skeletal muscle regeneration

Muscle stem cells orchestrate skeletal muscle regeneration through complex fate decisions. The transcriptional co-activators Yes-associated protein 1 (YAP) and WW domain-containing transcription regulator 1 (TAZ) contribute to multiple stages of myogenesis, yet their individual contributions to regeneration remain unclear due to substantial functional overlap. We genetically titrated YAP and TAZ expression in MuSCs with double knockout and single allele mutants by crossing Pax7CreERT mice with TAZflox/flox;YAPflox/flox mice. Conditional deletion of both YAP and TAZ in muscle stem cells severely disrupted muscle regeneration with dramatically increased fibrosis and impaired myofiber formation following injury. In contrast, a single allele of either YAP or TAZ was sufficient to rescue injured muscle weight and myofiber cross-sectional area. Similarly, the reduced proliferation of double knockout muscle stem cells on isolated myofibers was restored by a single allele of either YAP or TAZ. In addition, disrupted actin cytoskeleton organization and reduced focal adhesion formation drove double knockout muscle stem cell migration defects, negatively impacting muscle stem cell congregation prior to fusion. Thus, YAP and TAZ function redundantly as critical transcriptional co-activators to regulate progenitor proliferation and migration during muscle regeneration. By challenging myogenesis with double knockout of both YAP and TAZ, we unmasked regenerative requirements previously undetected in single-gene loss models, highlighting genetic redundancy as a key principle buffering regenerative robustness.