PUS7介导成骨细胞S100A6假尿苷修饰调控破骨细胞分化维持骨骼稳态的机制研究

骨骼稳态失衡导致骨质疏松症，但其分子调控网络未完全阐明。假尿苷合酶7（PUS7）调控RNA转录后假尿苷修饰，其突变可致表现为身材矮小的综合征，然而，PUS7是否调控骨骼稳态未见报道。申报人前期发现，Pus7全敲小鼠骨量下降，体内破骨细胞活性增强，而成骨细胞活性未见差异；体外实验发现，Pus7敲除的骨髓巨噬细胞（BMM）破骨分化未见差异，而Pus7敲除的骨髓间充质细胞（BMSC）促进共培养野生BMM破骨分化。深入研究发现，Pus7敲除致S100a6翻译效率上调，且S100A6蛋白促进野生型BMM破骨分化。综上，申报人提出“PUS7介导成骨细胞S100A6假尿苷修饰调控破骨细胞分化维持骨骼稳态”的科研假设，拟应用转基因小鼠、细胞培养、核糖体印迹测序等方法，从体内和体外两方面揭示PUS7介导成骨细胞S100A6假尿苷修饰调控破骨细胞分化维持骨骼稳态的分子机制，有望为骨质疏松症提供新治疗靶点。

Disruption of bone homeostasis leads to osteoporosis, but the regulatory network of bone homeostasis has not been fully elucidated. Pseudouridine synthase 7 (PUS7) is responsible for pseudouridylation, which is an important post-transcriptional modification in RNA. Mutations in PUS7 have been recently reported to cause intellectual developmental disorder with abnormal behavior, microcephaly and short stature (IDDABS), however, the role of PUS7 in regulating bone homeostasis is still little known. We previously found that global knockout of Pus7 led to significantly reduced bone mass and enhanced osteoclast activity in vivo, without differences in osteoblast activity. Importantly, Pus7 null bone marrow stromal cells (BMSC) promoted the osteoclastogenesis of co-cultured bone marrow macrophages (BMM), but Pus7 null BMM showed no differences in osteoclastogenesis. Further findings showed that Pus7 knockout led to increased translational efficiency of S100a6, and S100A6 recombinant protein promoted the osteoclastogenesis of wild type BMM. In summary, we propose the hypothesis that PUS7 maintains bone homeostasis by regulating osteoblast-mediated osteoclastogenesis via S100A6 pseudouridylation. In this project, we plan to utilize transgenic mice, primary BMSC/BMM and ribosome sequencing, try to study the molecular mechanism underlying PUS7 maintained bone homeostasis by osteoblast-mediated osteoclastogenesis via S100A6 pseudouridylation, and aim to report a new therapy target for osteoporosis.