The transcription factors L-Sox5 and Sox6 are essential for cartilage formation.
L-Sox5 and Sox6 are highly identical Sry-related transcription factors coexpressed in cartilage. Whereas Sox5 and Sox6 single null mice are born with mild skeletal abnormalities, Sox5; Sox6 double null fetuses die with a severe, generalized chondrodysplasia. In these double mutants, chondroblasts poorly differentiate. They express the genes for all essential cartilage extracellular matrix components at low or undetectable levels and initiate proliferation after a long delay. All cartilages are thus extracellular matrix deficient and remain rudimentary. While chondroblasts in the center of cartilages ultimately activate prehypertrophic chondrocyte markers, epiphyseal chondroblasts ectopically activate hypertrophic chondrocyte markers. Thick intramembranous bone collars develop, but the formation of cartilage growth plates and endochondral bones is disrupted. L-Sox5 and Sox6 are thus redundant, potent enhancers of chondroblast functions, thereby essential for endochondral skeleton formation.
Smits
P
P
Department of Molecular Genetics, The University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
Li
P
P
Mandel
J
J
Zhang
Z
Z
Deng
J M
JM
Behringer
R R
RR
de Crombrugghe
B
B
Lefebvre
V
V
D000818:Animals; D001846:Bone Development; D001842:Bone and Bones / Q000002:abnormalities; D002356:Cartilage / Q000196:embryology* / Q000502:physiology*; D002454:Cell Differentiation; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology*; D005097:Exostoses, Multiple Hereditary / Q000235:genetics; D006609:High Mobility Group Proteins / Q000378:metabolism* / Q000502:physiology*; D017403:In Situ Hybridization; D051379:Mice; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D008957:Models, Genetic; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism* / Q000502:physiology*; D010641:Phenotype; D055755:SOXD Transcription Factors; D014157:Transcription Factors
D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D009687:Nuclear Proteins; D055755:SOXD Transcription Factors; C089186:Sox5 protein, mouse; C095939:Sox6 protein, mouse; D014157:Transcription Factors