A mineralized endoskeleton supports the mammalian body. Bone also serves as a vital mineral repository and nurtures non-skeletal cell types, notably stem cells of the hematopoietic system. Skeletal anomalies are amongst the most common birth defects, problems in fracture repair are observed in non-union fractures and bone disorders are increasingly prevalent in an ageing population. Two key biosynthetic cell types generate the specific extracellular matrix of the mammalian skeleton: cartilage-secreting chondrocytes and bone secreting osteoblasts. These cells have diverse origins (neural crest, somitic and lateral plate mesoderm), and generate bone by distinct processes: directly from a mesenchymal stem cell (membranous bone) or via a cartilage template (endochondral bone). Mouse and human genetics have identified a number of critical signaling pathways, and three key transcription factors that are master regulators of chondrocyte (Sox9) and osteoblast (Runx2 and Osx) programs. Haploin sufficiency for Sox9 and Runx2 associates with human skeletal deficiencies. While the importance of these factors is well documented, their regulatory actions are not. To this end, we will determine the gene regulatory networks that underpin the regulatory actions of each of these critical skeletal determinants in chondrocyte and osteoblast development.
Specific Aim 1 : We will use gene-targeting in mouse embryo stem cells to create mice whose endogenous Sox9, Runx2 and Osx proteins are modified by appending a small peptide at their C-terminus. This epitope will enable subsequent analysis of the expression and activity of each factor through common approaches.
Specific Aim 2 : ChlP-seq analysis will be performed with each tagged protein to directly identify their DNA targets in primary chondrocytes or osteoblasts.
Specific Aim 3 : Data from microarray-based transcriptional profiling of normal chondrocytes and osteoblasts, or these same populations following knock-down of Sox9, Runx2 and Osx, will be intersected with ChlP-seq data to predict the targets of each regulatory factors actions. Selected regulatory models will be examined in transgenic mouse studies. These data will provide the first genome scale insight into the gene regulatory networks driving mammalian skeletogenesis.
Defective skeletal programs are a common birth defect, and an increasing problem in aging populations. Our skeleton is synthesized by two cells type, cartilage from chondrocytes and bone from osteoblasts, under the control of three master-regulatory genes. New mouse models will identify the regulatory programs governed by each factor providing the first genome scale insights into mammalian skeletal development.
|Chen, J W; Galloway, J L (2017) Using the zebrafish to understand tendon development and repair. Methods Cell Biol 138:299-320|
|Hojo, Hironori; McMahon, Andrew P; Ohba, Shinsuke (2016) An Emerging Regulatory Landscape for Skeletal Development. Trends Genet 32:774-787|
|Finch, Caleb E; McMahon, Andrew P (2016) Stem cells for all ages, yet hostage to aging. Stem Cell Investig 3:11|
|Hojo, Hironori; Ohba, Shinsuke; He, Xinjun et al. (2016) Sp7/Osterix Is Restricted to Bone-Forming Vertebrates where It Acts as a Dlx Co-factor in Osteoblast Specification. Dev Cell 37:238-53|
|He, Xinjun; Ohba, Shinsuke; Hojo, Hironori et al. (2016) AP-1 family members act with Sox9 to promote chondrocyte hypertrophy. Development 143:3012-23|
|Moore, Talia Y; Organ, Chris L; Edwards, Scott V et al. (2015) Multiple phylogenetically distinct events shaped the evolution of limb skeletal morphologies associated with bipedalism in the jerboas. Curr Biol 25:2785-2794|
|Ohba, Shinsuke; He, Xinjun; Hojo, Hironori et al. (2015) Distinct Transcriptional Programs Underlie Sox9 Regulation of the Mammalian Chondrocyte. Cell Rep 12:229-43|
|Kozhemyakina, Elena; Zhang, Minjie; Ionescu, Andreia et al. (2015) Identification of a Prg4-expressing articular cartilage progenitor cell population in mice. Arthritis Rheumatol 67:1261-73|
|Hirai, Takao; Kobayashi, Tatsuya; Nishimori, Shigeki et al. (2015) Bone Is a Major Target of PTH/PTHrP Receptor Signaling in Regulation of Fetal Blood Calcium Homeostasis. Endocrinology 156:2774-80|
|Ono, Noriaki; Kronenberg, Henry M (2015) Mesenchymal progenitor cells for the osteogenic lineage. Curr Mol Biol Rep 1:95-100|
Showing the most recent 10 out of 78 publications