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The neuromuscular junction (NMJ), which is a synapse for signal transmission from motor neurons to muscle cells, has emerged as an important region because of its association with several peripheral neuropathies. In particular, mutations in

The transcriptional regulator YAP, which plays important roles in the development, regeneration, and tumorigenesis, is activated when released from inhibition by the Hippo kinase cascade. The regulatory mechanism of YAP in Hippo-low contexts is poorly understood. Here, we performed a genome-wide RNA interference screen to identify genes whose loss of function in a Hippo-null background affects YAP activity. We discovered that the coatomer protein complex I (COPI) is required for YAP nuclear enrichment and that COPI dependency of YAP confers an intrinsic vulnerability to COPI disruption in YAP-driven cancer cells. We identified MAP2K3 as a YAP regulator involved in inhibitory YAP phosphorylation induced by COPI subunit depletion. The endoplasmic reticulum stress response pathway activated by COPI malfunction appears to connect COPI and MAP2K3. In addition, we provide evidence that YAP inhibition by COPI disruption may contribute to transcriptional up-regulation of PTGS2 and proinflammatory cytokines. Our study offers a resource for investigating Hippo-independent YAP regulation as a therapeutic target for cancers and suggests a link between YAP and COPI-associated inflammatory diseases.

In the peripheral nervous system (PNS), proper development of Schwann cells (SCs) contributing to axonal myelination is critical for neuronal function. Impairments of SCs or neuronal axons give rise to several myelin‐related disorders, including dysmyelinating and demyelinating diseases. Pathological mechanisms, however, have been understood at the elementary level and targeted therapeutics has remained undeveloped. Here, we identify Fibulin 5 (FBLN5), an extracellular matrix (ECM) protein, as a key paracrine factor of human Wharton's jelly‐derived mesenchymal stem cells (WJ‐MSCs) to control the development of SCs. We show that co‐culture with WJ‐MSCs or treatment of recombinant FBLN5 promotes the proliferation of SCs through ERK activation, whereas FBLN5‐depleted WJ‐MSCs do not. We further reveal that during myelination of SCs, FBLN5 binds to Integrin and modulates actin remodeling, such as the formation of lamellipodia and filopodia, through RAC1 activity. Finally, we show that FBLN5 effectively restores the myelination defects of SCs in the zebrafish model of Charcot‐Marie‐Tooth (CMT) type 1, a representative demyelinating disease. Overall, our data propose human WJ‐MSCs or FBLN5 protein as a potential treatment for myelin‐related diseases, including CMT., The common pathological symptom of dysmyelinating and demyelinating diseases is uncompact myelin ensheathments of the axons. Our findings suggest that FBLN5 binds to the Integrin receptors and promotes actin remodeling through RAC1 activation in the Schwann cells. Then, the Schwann cells are recovered by an activated actin remodeling mechanism and induce the compact myelination of the diseased axons.