PPIB mutations cause severe osteogenesis imperfecta.

Deficiency of cartilage-associated protein (CRTAP) or prolyl 3-hydroxylase 1(P3H1) has been reported in autosomal-recessive lethal or severe osteogenesis imperfecta (OI). CRTAP, P3H1, and cyclophilin B (CyPB) form an intracellular collagen-modifying complex that 3-hydroxylates proline at position 986 (P986) in the alpha1 chains of collagen type I. This 3-prolyl hydroxylation is decreased in patients with CRTAP and P3H1 deficiency. It was suspected that mutations in the PPIB gene encoding CyPB would also cause OI with decreased collagen 3-prolyl hydroxylation. To our knowledge we present the first two families with recessive OI caused by PPIB gene mutations. The clinical phenotype is compatible with OI Sillence type II-B/III as seen with COL1A1/2, CRTAP, and LEPRE1 mutations. The percentage of 3-hydroxylated P986 residues in patients with PPIB mutations is decreased in comparison to normal, but it is higher than in patients with CRTAP and LEPRE1 mutations. This result and the fact that CyPB is demonstrable independent of CRTAP and P3H1, along with reported decreased 3-prolyl hydroxylation due to deficiency of CRTAP lacking the catalytic hydroxylation domain and the known function of CyPB as a cis-trans isomerase, suggest that recessive OI is caused by a dysfunctional P3H1/CRTAP/CyPB complex rather than by the lack of 3-prolyl hydroxylation of a single proline residue in the alpha1 chains of collagen type I.

Spondyloepiphyseal dysplasia, Omani type: further definition of the phenotype.

Spondyloepiphyseal dysplasia (SED), Omani type (OMIM 608637) is a recessively inherited skeletal dysplasia previously described in two distantly related families from the Republic of Oman. The phenotype consists of short stature, severe kyphoscoliosis, arthritic joints (elbows, wrists, knees), secondary large joint dislocations, rhizomelia, fusion of carpal bones and mild brachydactyly. Affected individuals were homozygous for a missense mutation, R304Q in CHST3 that encodes the enzyme chondroitin 6-O-sulfotransferase-1 (C6ST-1). This enzyme mediates the sulfation of proteoglycans, particularly chondroitin sulfate (CS), in the extracellular matrix of cartilage. Here we describe the identification of a mutation (857T > C predicting the substitution L286P) in CHST3 in a Turkish family and extend the clinical phenotype of SED-Omani type to include congenital joint dislocation, club feet, ventricular septal defect, deafness, metacarpal shortening and accessory carpal ossification centers. Fibroblasts and urine obtained from affected patients demonstrated negligible levels of 6-O-sulfated GalNAc residue in CS. Furthermore, the 6-O-sulfotransferase activity of cloned C6ST-1 into which the L286P mutation had been introduced was dramatically reduced, confirming the pathogenicity of this substitution. These results indicate that the clinical consequences of a deficiency of 6-O-sulfation in CS can be varied and that a clinical spectrum may exist similar to that seen in other skeletal dysplasias characterized by disorders of proteoglycan sulfation.