A signaling crosstalk regulation in neural crest-derived cranial suture - PROJECT SUMMARY Craniofacial deformity often involves cranial sutures. Adequate understanding of the molecular mechanism underlying cranial suture development is urgently demanded for exploring new diagnostic and therapeutic methods for cranial diseases, such as craniosynostosis and sutural agenesis. Neural crest cells (NCCs) are a multipotent stem cell population, and make great contributions to cranial suture development, especially frontal (metopic) suture, which is derived from NCCs. The long-term objective of this K99/R00 application is to develop Dr. Xiaolei Zhao's capability to conduct studies aimed at dissecting and mapping the molecular mechanism underlying cranial suture development, to explore novel and critical factors for the diagnosis and treatment of cranial suture diseases. In the K99 phase, the proposed studies support Dr. Zhao in four training goals which will allow her to learn more skills and transition to an independent investigator, who focuses on studying the complicated molecular mechanism of how cranial suture is orchestrated during craniofacial development. First, she will obtain training in iPSCs, which will allow her to explore and validate the molecular mechanism in human cells. Second, she will learn how to analyze the large datasets, such as single cell RNA-seq and CUT&RUN, using bioinformatics techniques to fully understand and analyze the sequencing results. Third, she will extend her knowledge in craniofacial field to comprehensively understand the craniofacial development and disease as well as the potential molecular regulation. Finally, Dr. Zhao will engage in career training for professional development, especially in the writing, mentoring and collaboration. Dr. Zhao's pilot data discovered a crosstalk between two fundamental pathways, FGF and Hippo-Yap pathway, in NCC-derived suture, which had not been reported up to date. Her data also revealed the potential functions of the crosstalk in stemness and differentiation of NC-derived suture cells. To further dissect the potential and novel molecular mechanism underlying cranial suture development, which could potentially contribute to the discovery of critical factors for the diagnosis and treatment of cranial suture diseases, Dr. Zhao proposed 3 research aims in this application as follows. In Aim 1, she evaluates the functions of FGF signaling in stemness and differentiation of NCC-derived suture cells, and investigates if the Hippo signaling downstream effectors, Yap and Taz, are required for the functions of FGF signaling. In Aim 2, she proposes to validate the molecular interaction between Yap/Taz and FGF signaling downstream effectors, p-ERK1/2, which was shown in her pilot data, er vivo and in vivo, and detect how p-ERK1/2 affect Yap and Taz activity. In Aim 3, she further dissects the population and function of suture mesenchymal stem cells (SMSCs) in NC-derived frontal suture at single cell level, and how SMSCs are coordinately regulated by FGF and Hippo-Yap pathways. Through comprehensive analysis, she expects to discover novel and critical factors for cranial suture development and diseases.
