title: Deficiency of CRTAP in non-lethal recessive osteogenesis imperfecta reduces collagen deposition into matrix.
abstract: Deficiency of any component of the ER-resident collagen prolyl 3-hydroxylation complex causes recessive osteogenesis imperfecta (OI). The complex modifies the α1(I)Pro986 residue and contains cartilage-associated protein (CRTAP), prolyl 3-hydroxylase 1 (P3H1) and cyclophilin B (CyPB). Fibroblasts normally secrete about 10% of CRTAP. Most CRTAP mutations cause a null allele and lethal type VII OI. We identified a 7-year-old Egyptian boy with non-lethal type VII OI and investigated the effects of his null CRTAP mutation on collagen biochemistry, the prolyl 3-hydroxylation complex, and collagen in extracellular matrix. The proband is homozygous for an insertion/deletion in CRTAP (c.118_133del16insTACCC). His dermal fibroblasts synthesize fully overmodified type I collagen, and 3-hydroxylate only 5% of α1(I)Pro986. CRTAP transcripts are 10% of control. CRTAP protein is absent from proband cells, with residual P3H1 and normal CyPB levels. Dermal collagen fibril diameters are significantly increased. By immunofluorescence of long-term cultures, we identified a severe deficiency (10-15% of control) of collagen deposited in extracellular matrix, with disorganization of the minimal fibrillar network. Quantitative pulse-chase experiments corroborate deficiency of matrix deposition, rather than increased matrix turnover. We conclude that defects of extracellular matrix, as well as intracellular defects in collagen modification, contribute to the pathology of type VII OI.
authors.affiliation: Department of Biochemistry A. Castellani, University of Pavia, Pavia, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Valli
authors.forename: A M
authors.initials: AM
authors.lastname: Barnes
authors.forename: A
authors.initials: A
authors.lastname: Gallanti
authors.forename: W A
authors.initials: WA
authors.lastname: Cabral
authors.forename: S
authors.initials: S
authors.lastname: Viglio
authors.forename: M A
authors.initials: MA
authors.lastname: Weis
authors.forename: E
authors.initials: E
authors.lastname: Makareeva
authors.forename: D
authors.initials: D
authors.lastname: Eyre
authors.forename: S
authors.initials: S
authors.lastname: Leikin
authors.forename: F
authors.initials: F
authors.lastname: Antoniazzi
authors.forename: J C
authors.initials: JC
authors.lastname: Marini
authors.forename: M
authors.initials: M
authors.lastname: Mottes
mesh_terms: D000483:Alleles; D002648:Child; D024042:Collagen Type I / Q000378:metabolism*; D000090602:Collagen Type I, alpha 1 Chain; D021983:Cyclophilins / Q000235:genetics / Q000378:metabolism; D004534:Egypt; D016326:Extracellular Matrix Proteins / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D017353:Gene Deletion; D005808:Genes, Recessive; D006720:Homozygote; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D018832:Molecular Chaperones; D009154:Mutation; D010013:Osteogenesis Imperfecta / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D064828:Prolyl Hydroxylases; D011499:Protein Processing, Post-Translational; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism
chemical_list: C108053:CRTAP protein, human; D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D016326:Extracellular Matrix Proteins; D008562:Membrane Glycoproteins; D018832:Molecular Chaperones; D011509:Proteoglycans; C081786:cyclophilin B; D064828:Prolyl Hydroxylases; C485657:P3H1 protein, human; D021983:Cyclophilins