Abstract Body : Neural crest cells (NCCs) can give rise to suture mesenchymal stem cells (SMSCs) that are required to keep the suture patency and allow for cranial bone growth, repair and regeneration. Studies in patients with syndromic craniosynostosis indicated FGF signaling as an important regulator of SMSCs stemness and differentiation. Here we identified a cross talk between FGF and Hippo signaling mediated by p-ERK1/2 and Yap/Taz interactions to regulate NC-derived SMSCs stemness and differentiation both in vitro and in vivo. We found that FGF activation could keep NCC stemness and inhibit their osteoblast differentiation, whereas these functions were abolished when Yap/Taz were double knockdown (dKD) or p-ERK1/2 were inhibited in NCCs. Similar to the FGF gain-of-function mice, defective NC-derived frontal suture was observed in NCC specific Salv knockout (KO) mice, which had increased nuclear localized Yap/Taz in NCC. In addition, inhibition of p-ERK1/2 caused defective cranial bone similar to mice with Yap/Taz deficiency in NCCs. Further comprehensive analysis of CUT&RUN-seq and RNA-seq datasets indicated that Yap and p-ERK1/2 largely shared potential target genes and were regulated by FGF signaling during NC-derived osteogenesis. Both in vitro and in vivo, p-ERK1/2 could directly interact with Yap to regulate downstream target genes, and p-ERK1/2 phosphorylate S128 of Yap to promote Yap translocate into nuclei. Together, our data provided the first evidence that FGF signaling can regulate NC-derived SMSCs through promoting p-ERK1/2 to interact with Yap/Taz. Our findings revealed novel insights into the molecular regulation underlying NC-derived SMSCs stemness maintenance and differentiation, which opens a new avenue for understanding the mechanism underlying cranial suture diseases.
