Identification a pathogenic gene in a pedigree with symphalangism
10.3760/cma.j.cn114453-20200315-00150
- VernacularTitle:一个先天性指间关节粘连家系致病基因鉴定
- Author:
Hengqing CUI
1
;
Bin SUN
;
Xia FANG
;
Shengbo ZHOU
;
Haoran YANG
;
Xinyi DAI
;
Gang HAN
;
Bin WANG
Author Information
1. 上海交通大学医学院附属第九人民医院整复外科 200011
- Keywords:
Symphalangism;
Mutation;
Pedigree;
Ankylosis
- From:
Chinese Journal of Plastic Surgery
2020;36(5):499-506
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To identify the pathogenic gene of a pedigree with symphalangism and to prove the pathogenicity of this locus in vitro.Methods:The clinical data of patients’families were collected at Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, peripheral blood was collected and genomic DNA was extracted and NOG, FGF9, GDF5 exon regions were amplified by PCR, and the exon gene mutations were detected by first-generation sequencing technique. The structure of noggin-GDF5 protein complex was simulated in silicon. COS-7 cells were transfected with 5 μg empty plasmid, wild type plasmid and V202G mutant plasmid in vitro. Each group of plasmids was transfected into 3 well cells. The experiment was repeated for 3 times, and the expression of noggin protein was detected by Western blotting. C2C12 cells were also transfected with the above plasmids in vitro for osteogenic differentiation. By applying alkaline phosphatase staining and quantitative assay. Relative expression level of osteoblast-related genes Col1α1, ALP and Runx2 were detected by qRT-PCR. Each group of plasmids was transfected into 3 well cells, and the experiment was repeated for 3 times. All statistical analysis were performed by Prism 6 software. The result were shown as mean±standard deviation, and the comparison between groups was done by unpaired t-test. Data were considered statistically significant when P value is less than 0.05. Results:Both the proband and his mother suffered from symphalangism. The result of Sanger sequencing showed that there was a heterozygous missense mutation of NOG gene (p.V202G) in all patients in this pedigree. No disease-related mutations were detected in FGF9 and GDF5. Computer three-dimensional mechanism simulation showed that the site was located at the α helix. The result of Western blotting showed that the expression of mutant protein was significantly lower than that of wild type. Osteogenic differentiation in vitro showed that the inhibitory effect of V202G mutant protein on osteogenic differentiation decreased. The quantitative result of alkaline phosphatase staining showed that the alkaline phosphatase activity in the vector group was (12.3±0.8) U/L, and the alkaline phosphatase activity in the wild type plasmid group was (2.6±0.3) U/L, which was significantly lower than that in the vector group ( t=11.550, P<0.001). The alkaline phosphatase activity in the mutant plasmid group was (10.8±0.3) U/L. There was no significant difference between the mutant group and the vector group ( t=1.830, P=0.141). The mRNA expression level of osteogenesis-related genes was consistent with the above result . Compared with vector group, the expression of osteogenesis-related genes in wild-type noggin group decreased significantly ALP、 Col1α1 and Runx2 ( t=5.987, 4.498, 4.170; P=0.004, 0.011, 0.014). There was no significant difference between mutant plasmid group and blank vector group in ALP、 Col1α1 and Runx2 ( t=0.433, 0.177, 1.159; P=0.688, 0.868, 0.311). Conclusions:NOG gene c. 605T < G p. V202G is a novel mutation in symphalangism, which is located in the α helix of noggin protein, leading to the decrease of the expression of noggin protein and the manifestation of ankylosis.
