RESUMO
Runx1 is expressed in skeletal elements, but its role in fracture repair has not been analyzed. We created mice with a hypomorphic Runx1 allele (Runx1(L148A) ) and generated Runx1(L148A/-) mice in which >50% of Runx1 activity was abrogated. Runx1(L148A/-) mice were viable but runted. Their growth plates had extended proliferating and hypertrophic zones, and the percentages of Sox9-, Runx2-, and Runx3-positive cells were decreased. Femoral fracture experiments revealed delayed cartilaginous callus formation, and the expression of chondrogenic markers was decreased. Conditional ablation of Runx1 in the mesenchymal progenitor cells of the limb with Prx1-Cre conferred no obvious limb phenotype; however, cartilaginous callus formation was delayed following fracture. Embryonic limb bud-derived mesenchymal cells showed delayed chondrogenesis when the Runx1 allele was deleted ex vivo with adenoviral-expressed Cre. Collectively, our data suggest that Runx1 is required for commitment and differentiation of chondroprogenitor cells into the chondrogenic lineage.
Assuntos
Osso e Ossos/metabolismo , Condrócitos/citologia , Subunidade alfa 2 de Fator de Ligação ao Core/fisiologia , Alelos , Animais , Cartilagem/citologia , Cartilagem/metabolismo , Relação Dose-Resposta a Droga , Éxons , Feminino , Consolidação da Fratura , Mesoderma/citologia , Camundongos , Camundongos Transgênicos , Mutação , Osteocalcina/biossíntese , Fenótipo , Regiões Promotoras Genéticas , Células-Tronco/citologiaAssuntos
Melanoma/patologia , Neoplasias da Medula Espinal/patologia , Subunidades alfa de Proteínas de Ligação ao GTP/genética , Subunidades alfa Gq-G11 de Proteínas de Ligação ao GTP , Humanos , Imageamento por Ressonância Magnética , Masculino , Melanoma/diagnóstico , Melanoma/genética , Melanoma/cirurgia , Pessoa de Meia-Idade , Mutação , Neoplasias da Medula Espinal/diagnóstico , Neoplasias da Medula Espinal/genética , Neoplasias da Medula Espinal/cirurgiaRESUMO
Monoallelic RUNX1 mutations cause familial platelet disorder with predisposition for acute myelogenous leukemia (FPD/AML). Sporadic mono- and biallelic mutations are found at high frequencies in AML M0, in radiation-associated and therapy-related myelodysplastic syndrome and AML, and in isolated cases of AML M2, M5a, M3 relapse, and chronic myelogenous leukemia in blast phase. Mutations in RUNX2 cause the inherited skeletal disorder cleidocranial dysplasia (CCD). Most hematopoietic missense mutations in Runx1 involve DNA-contacting residues in the Runt domain, whereas the majority of CCD mutations in Runx2 are predicted to impair CBFbeta binding or the Runt domain structure. We introduced different classes of missense mutations into Runx1 and characterized their effects on DNA and CBFbeta binding by the Runt domain, and on Runx1 function in vivo. Mutations involving DNA-contacting residues severely inactivate Runx1 function, whereas mutations that affect CBFbeta binding but not DNA binding result in hypomorphic alleles. We conclude that hypomorphic RUNX2 alleles can cause CCD, whereas hematopoietic disease requires more severely inactivating RUNX1 mutations.
Assuntos
Displasia Cleidocraniana/genética , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Subunidade alfa 2 de Fator de Ligação ao Core/genética , DNA/metabolismo , Doenças Hematológicas/genética , Modelos Moleculares , Mutação de Sentido Incorreto/genética , Estrutura Terciária de Proteína , Animais , Contagem de Células Sanguíneas , Western Blotting , Subunidade beta de Fator de Ligação ao Core/metabolismo , Primers do DNA , Citometria de Fluxo , Transferência Ressonante de Energia de Fluorescência , Espectroscopia de Ressonância Magnética , Camundongos , Espectrometria de Fluorescência , Técnicas do Sistema de Duplo-HíbridoRESUMO
The family of core-binding factors includes the DNA-binding subunits Runx1-3 and their common non-DNA-binding partner CBFbeta. We examined the collective role of core-binding factors in hematopoiesis with a hypomorphic Cbfb allelic series. Reducing CBFbeta levels by 3- or 6-fold caused abnormalities in bone development, megakaryocytes, granulocytes, and T cells. T-cell development was very sensitive to an incremental reduction of CBFbeta levels: mature thymocytes were decreased in number upon a 3-fold reduction in CBFbeta levels, and were virtually absent when CBFbeta levels were 6-fold lower. Partially penetrant consecutive differentiation blocks were found among early T-lineage progenitors within the CD4- CD8- double-negative 1 and downstream double-negative 2 thymocyte subsets. Our data define a critical CBFbeta threshold for normal T-cell development, and situate an essential role for core-binding factors during the earliest stages of T-cell development.