Loss of Sprouty Produces a Ciliopathic Skeletal Phenotype in Mice Through Upregulation of Hedgehog Signaling

• Published in: Journal of bone and mineral research Vol. 36; no. 11; pp. 2258 - 2274
• Main Authors: Hruba, Eva, Kavkova, Michaela, Dalecka, Linda, Macholan, Miloš, Zikmund, Tomas, Varecha, Miroslav, Bosakova, Michaela, Kaiser, Jozef, Krejci, Pavel, Hovorakova, Maria, Buchtova, Marcela
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.11.2021; Wiley Subscription Services, Inc
• Subjects: ANALYSIS/QUANTITATION OF BONE; Animals; Axonemes; Bone growth; Bone mass; BONE MODELING AND REMODELING; BONE QCT/μCT; Cancellous bone; CELL/TISSUE SIGNALING; Chondrocytes; Chondroma; Cilia; Cilia - metabolism; Ciliopathies - genetics; Embryo fibroblasts; Embryos; Endochondral bone; GENETIC ANIMAL MODELS; Growth plate; HEDGEHOG; Hedgehog protein; Hedgehog Proteins - metabolism; Hereditary diseases; Intracellular signalling; LIMB PATTERNING; Membrane Proteins - genetics; Mice; Mice, Transgenic; MOLECULAR PATHWAYS – DEVELOPMENT; Mutants; Nerve Tissue Proteins - genetics; Osteogenesis; Phenotype; Phenotypes; Protein Serine-Threonine Kinases - genetics; Protein-tyrosine kinase receptors; Signal Transduction; Skeletogenesis; Structure-function relationships; Tibia; Transgenic mice; Up-Regulation; CELL/TISSUE SIGNALING; BONE MODELING AND REMODELING; GENETIC ANIMAL MODELS; LIMB PATTERNING; MOLECULAR PATHWAYS - DEVELOPMENT; ANALYSIS/QUANTITATION OF BONE; BONE QCT/μCT; HEDGEHOG
• DOI: 10.1002/jbmr.4427
• ISSN: 0884-0431

ABSTRACT The Sprouty family is a highly conserved group of intracellular modulators of receptor tyrosine kinase (RTK)‐signaling pathways, which have been recently linked to primary cilia. Disruptions in the structure and function of primary cilia cause inherited disorders called ciliopathies. We aimed to evaluate Sprouty2 and Sprouty4 gene‐dependent alterations of ciliary structure and to focus on the determination of its association with Hedgehog signaling defects in chondrocytes. Analysis of the transgenic mice phenotype with Sprouty2 and Sprouty4 deficiency revealed several defects, including improper endochondral bone formation and digit patterning, or craniofacial and dental abnormalities. Moreover, reduced bone thickness and trabecular bone mass, skull deformities, or chondroma‐like lesions were revealed. All these pathologies might be attributed to ciliopathies. Elongation of the ciliary axonemes in embryonic and postnatal growth plate chondrocytes was observed in Sprouty2−/− and Sprouty2+/−/Sprouty4−/− mutants compared with corresponding littermate controls. Also, cilia‐dependent Hedgehog signaling was upregulated in Sprouty2/4 mutant animals. Ptch1 and Ihh expression were upregulated in the autopodium and the proximal tibia of Sprouty2−/−/Sprouty4−/− mutants. Increased levels of the GLI3 repressor (GLI3R) form were detected in Sprouty2/4 mutant primary fibroblast embryonic cell cultures and tissues. These findings demonstrate that mouse lines deficient in Sprouty proteins manifest phenotypic features resembling ciliopathic phenotypes in multiple aspects and may serve as valuable models to study the association between overactivation of RTK and dysfunction of primary cilia during skeletogenesis. © 2021 American Society for Bone and Mineral Research (ASBMR).