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BioMed Research International
Volume 2017, Article ID 5809787, 9 pages
https://doi.org/10.1155/2017/5809787
Research Article

Decreased Plasma COMP and Increased Plasma CTX-II Levels in a Chinese Pseudoachondroplasia Family with Novel COMP Mutation

Department of Medical Genetics, West China Hospital, Sichuan University, Chengdu, China

Correspondence should be addressed to Yongxin Ma; moc.liamg@nixgnoyam

Received 19 February 2017; Accepted 11 July 2017; Published 27 August 2017

Academic Editor: Limei Qiu

Copyright © 2017 Chongjuan Gu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Pseudoachondroplasia (PSACH) is an autosomal dominant osteochondrodysplasia caused by mutations in the gene encoding cartilage oligomeric matrix protein (COMP). Accurate clinical diagnosis of PSACH is sometimes difficult. Here, we identified a novel COMP mutation (c.1675G>A, p.Glu559Lys) in a Chinese PSACH family. We detected the plasma levels of COMP and type II collagen (CTX-II) in the four affected individuals. The results showed the levels of plasma COMP significantly decreased and plasma CTX-II significantly increased in the three PSACH patients with COMP mutation. However, both plasma levels of COMP and CTX-II were not to have found significant difference between the presymptomatic carrier and the age-matched subjects. In vitro analysis and immunofluorescence displayed wild type COMP homogenously expressed in cytoplasm, but mutant proteins were irregularly accumulated inside the HEK-293 cells. Western blot revealed that the quantity of the mutant COMP was more compared to wild type COMP in cells after transfection for 12 hours and 24 hours. Subsequently, 3D structural analysis showed three changes have taken place in secondary structure of the mutant COMP. In conclusion, the novel mutation of COMP may result in intracellular accumulation of the mutant protein. Decreased plasma COMP and increased plasma CTX-II may potentially serve as diagnostic markers of PSACH but may not be applicable in the presymptomatic carrier.