Recessive osteogenesis imperfecta caused by LEPRE1 mutations: clinical documentation and identification of the splice form responsible for prolyl 3-hydroxylation. Issue 4 (16th December 2008)

• Record Type: Journal Article
• Authors: Willaert, A; Malfait, F; Symoens, S; Gevaert, K; Kayserili, H; Megarbane, A; Mortier, G; Leroy, J G; Coucke, P J; De Paepe, A
• Is Part Of: Journal of medical genetics. Volume 46:Issue 4(2009)
• Page Start: 233
• Page End: 241
• Publication Date: 2008-12-16
• Subjects: Medical genetics -- Periodicals; 616.042
• DOI: 10.1136/jmg.2008.062729
• Languages: English
• ISSNs: 1468-6244

Abstract

Abstract : Background: Recessive forms of osteogenesis imperfecta (OI) may be caused by mutations in LEPRE1, encoding prolyl 3-hydroxylase-1 (P3H1) or in CRTAP, encoding cartilage associated protein. These proteins constitute together with cyclophilin B (CyPB) the prolyl 3-hydroxylation complex that hydroxylates the Pro986 residue in both the type I and type II collagen α1-chains. Methods: We screened LEPRE1, CRTAP and PPIB (encoding CyPB) in a European/Middle Eastern cohort of 20 lethal/severe OI patients without a type I collagen mutation. Results: Four novel homozygous and compound heterozygous mutations were identified in LEPRE1 in four probands. Two probands survived the neonatal period, including one patient who is the eldest reported patient (17 7/12 years) so far with P3H1 deficiency. At birth, clinical and radiologic features were hardly distinguishable from those in patients with autosomal dominant (AD) severe/lethal OI. Follow-up data reveal that the longer lived patients develop a severe osteochondrodysplasia that overlaps with, but has some distinctive features from, AD OI. A new splice site mutation was identified in two of the four probands, affecting only one of three LEPRE1 mRNA splice forms, detected in this study. The affected splice form encodes a 736 amino acid (AA) protein with a "KDEL" endoplasmic reticulum retention signal. While western blotting and immunocytochemical analysis of fibroblast cultures revealed absence of this P3H1 protein, mass spectrometry and SDS-urea-PAGE data showed severe reduction of α1(I)Pro986 3-hydroxylation and overmodification of type I (pro)collagen chains in skin fibroblasts of the patients. Conclusion: These findings suggest that the 3-hydroxylation function of P3H1 is restricted to the 736AA splice form.