Role of GI OSTERIX in Gut and Bone Biology

项目总结:

PROJECT SUMMARY: It has been known for decades that the gut profoundly regulates bone mineral homeostasis by influencing the development and function of bone-forming osteoblasts and bone-degrading osteoclasts. At the cellular and molecular levels, how the gut affects the bone and whether skeletal and gastrointestinal (GI) epithelium development is functionally synchronized remains largely unknown. The work outlined in this proposal builds on our novel and exciting discovery that the zinc finger protein OSTERIX, which to this point has been considered a bone-specific master transcription factor, is robustly expressed in the intestinal crypts. OSTERIX expression has not yet been reported in extraskeletal tissues. We discovered OSTERIX in GI epithelium while examining the role of the phosphatase SHP2 in mouse skeletal development using Osterix-Cre-mediated deletion of PTPN11 foxed alleles. Subsequently, we confirmed that the OSTERIX promoter is active and OSTERIX protein is expressed in the GI crypt base stem cells (CBCs). Given OSTERIX’s central role in bone development, we hypothesize that OSTERIX in the GI crypt cells may participate in GI epithelial development and bone mineral homeostasis. Building on these novel findings we will take the R21 funding mechanism and determine how OSTERIX modulates the self-renewal and multiple lineage differentiation of the GI CBCs, and examine whether and how OSTERIX in the GI epithelium modulates osteoblast and osteoclast function and bone mineral homeostasis. In Specific Aim #1 we will test the hypothesis that OSX maintains CBC stemness and regulates multilineage differentiation using genetically modified mice in combination of approaches including marker colocalization, live cell-lineage tracing, organoid culture, histology, and immunohistochemical staining. In Specific Aim #2 we will test the hypothesis that GI OSX regulates OB and osteoclast function and bone mineral homeostasis by modulating the expression of GI epithelial growth factors and hormones. Approaches including new bone formation assays, RNAScope®, histomorphometry, immunostaining, and biochemical assays of bone metabolic markers will be applied in this study.