title: Increased Col10a1 expression is not causative for the phenotype of Phex-deficient Hyp mice.
abstract: X-linked hypophosphatemic rickets (XLHR) is a severe disorder of phosphate homeostasis and skeletal mineralization caused by mutations of PHEX, encoding a bone-specific endopeptidase. Phex-deficient Hyp mice have been extensively studied to understand the molecular bases of XLHR, and here it was found that Fgf23, encoding a major phosphaturic hormone, was transcriptionally activated in bone-forming osteoblasts. We and others could additionally show that Col10a1 expression is increased in Hyp osteoblasts and bones, thereby raising the possibility that ectopic production of type X collagen could contribute to the impaired mineralization of the Hyp bone matrix. Here we show that an additional deficiency of the Col10a1 gene does not overtly affect the skeletal phenotype of Hyp mice. More specifically, Col10a1-deficient Hyp mice displayed severe disturbances of skeletal growth, bone mass acquisition and bone matrix mineralization, and they were essentially indistinguishable from Hyp littermates. This was confirmed by non-decalcified histology and bone-specific histomorphometry quantifying all relevant parameters of growth plate maturation, trabecular bone architecture and osteoid accumulation. Taken together, our results show that increased Col10a1 expression in Phex-deficient osteoblasts is not a major cause of the XLHR phenotype, which was an important issue to address based on the previous findings.
authors.affiliation: Department of Osteology and Biomechanics, University Medical Center Hamburg Eppendorf, Hamburg, Germany.
authors.forename: Timur
authors.initials: T
authors.lastname: Yorgan
authors.forename: Carsten
authors.initials: C
authors.lastname: Rendenbach
authors.forename: Anke
authors.initials: A
authors.lastname: Jeschke
authors.forename: Michael
authors.initials: M
authors.lastname: Amling
authors.forename: Kathryn S E
authors.initials: KS
authors.lastname: Cheah
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schinke
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000002:abnormalities* / Q000378:metabolism; D024121:Collagen Type X / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D053098:Familial Hypophosphatemic Rickets / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D000089703:Fibroblast Growth Factor-23; D015870:Gene Expression; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D018482:Muscle, Skeletal; D010006:Osteoblasts / Q000378:metabolism*; D010018:Osteomalacia / Q000378:metabolism / Q000473:pathology; D053402:PHEX Phosphate Regulating Neutral Endopeptidase / Q000235:genetics*
chemical_list: C570620:Col10a1 protein, mouse; D024121:Collagen Type X; C000717428:Fgf23 protein, mouse; D000089703:Fibroblast Growth Factor-23; D053402:PHEX Phosphate Regulating Neutral Endopeptidase; C506232:Phex protein, mouse
keywords: Osteomalacia; Phex; Type X collagen; X-linked hypophosphatemic rickets