Mutations in genes affecting primary cilia cause ciliopathies, a diverse group of disorders often affecting skeletal development. This includes Jeune syndrome or asphyxiating thoracic dystrophy (ATD), an autosomal recessive skeletal disorder. Unraveling the responsible molecular pathology helps illuminate mechanisms responsible for functional primary cilia. We identified two families with ATD caused by loss-of-function mutations in the gene encoding adrenergic receptor kinase 1 (ADRBK1 or GRK2). GRK2 cells from an affected individual homozygous for the p.R158* mutation resulted in loss of GRK2, and disrupted chondrocyte growth and differentiation in the cartilage growth plate. GRK2 null cells displayed normal cilia morphology, yet loss of GRK2 compromised cilia-based signaling of Hedgehog (Hh) pathway. Canonical Wnt signaling was also impaired, manifested as a failure to respond to Wnt ligand due to impaired phosphorylation of the Wnt co-receptor LRP6. We have identified GRK2 as an essential regulator of skeletogenesis and demonstrate how both Hh and Wnt signaling mechanistically contribute to skeletal ciliopathies.

• MeSH
• Ellisův-van Creveldův syndrom * MeSH
• kinasa 2 receptorů spřažených s G-proteiny genetika   MeSH
• lidé MeSH
• mutace MeSH
• proteiny hedgehog * genetika   MeSH
• signální dráha Wnt MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH

Aberrant fibroblast growth factor (FGF) signaling disturbs chondrocyte differentiation in skeletal dysplasia, but the mechanisms underlying this process remain unclear. Recently, FGF was found to activate canonical WNT/β-catenin pathway in chondrocytes via Erk MAP kinase-mediated phosphorylation of WNT co-receptor Lrp6. Here, we explore the cellular consequences of such a signaling interaction. WNT enhanced the FGF-mediated suppression of chondrocyte differentiation in mouse limb bud micromass and limb organ cultures, leading to inhibition of cartilage nodule formation in micromass cultures, and suppression of growth in cultured limbs. Simultaneous activation of the FGF and WNT/β-catenin pathways resulted in loss of chondrocyte extracellular matrix, expression of genes typical for mineralized tissues and alteration of cellular shape. WNT enhanced the FGF-mediated downregulation of chondrocyte proteoglycan and collagen extracellular matrix via inhibition of matrix synthesis and induction of proteinases involved in matrix degradation. Expression of genes regulating RhoA GTPase pathway was induced by FGF in cooperation with WNT, and inhibition of the RhoA signaling rescued the FGF/WNT-mediated changes in chondrocyte cellular shape. Our results suggest that aberrant FGF signaling cooperates with WNT/β-catenin in suppression of chondrocyte differentiation.

• MeSH
• beta-katenin genetika   metabolismus   MeSH
• biologické modely MeSH
• buněčná diferenciace účinky léků   genetika   MeSH
• chondrocyty účinky léků   metabolismus   MeSH
• chrupavka cytologie   účinky léků   metabolismus   MeSH
• fibroblastové růstové faktory farmakologie   MeSH
• fibroblastový růstový faktor 2 farmakologie   MeSH
• HEK293 buňky MeSH
• končetinové pupeny účinky léků   embryologie   metabolismus   MeSH
• konfokální mikroskopie MeSH
• krysa rodu rattus MeSH
• kultivované buňky MeSH
• LDL receptor related protein 6 genetika   metabolismus   MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• protein Wnt3A farmakologie   MeSH
• proteiny Wnt genetika   metabolismus   farmakologie   MeSH
• receptory fibroblastových růstových faktorů genetika   metabolismus   MeSH
• signální transdukce účinky léků   genetika   MeSH
• synergismus léků MeSH
• transkriptom účinky léků   genetika   MeSH
• western blotting MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Somatic mutations in receptor tyrosine kinase FGFR3 cause excessive cell proliferation, leading to cancer or skin overgrowth. Remarkably, the same mutations inhibit chondrocyte proliferation and differentiation in developing bones, resulting in skeletal dysplasias, such as hypochondroplasia, achondroplasia, SADDAN and thanatophoric dysplasia. A similar phenotype is observed in Noonan syndrome, Leopard syndrome, hereditary gingival fibromatosis, neurofibromatosis type 1, Costello syndrome, Legius syndrome and cardiofaciocutaneous syndrome. Collectively termed RASopathies, the latter syndromes are caused by germline mutations in components of the RAS/ERK MAP kinase signaling pathway. This article considers the evidence suggesting that FGFR3 activation in chondrocytes mimics the activation of major oncogenes signaling via the ERK pathway. Subsequent inhibition of chondrocyte proliferation in FGFR3-related skeletal dysplasias and RASopathies is proposed to result from activation of defense mechanisms that originally evolved to safeguard mammalian organisms against cancer.

• MeSH
• buněčná diferenciace genetika   MeSH
• chondrocyty cytologie   metabolismus   MeSH
• geny ras genetika   MeSH
• lidé MeSH
• nádory kostí genetika   patologie   MeSH
• proliferace buněk MeSH
• receptor fibroblastových růstových faktorů, typ 3 genetika   metabolismus   MeSH
• signální transdukce MeSH
• vývoj kostí genetika   MeSH
• vývojové onemocnění kostí genetika   patologie   MeSH
• zárodečné mutace MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH