Autosomal dominant osteopetrosis type Ⅱ: 2 cases report and literature review / 中华内分泌代谢杂志

Osteosclerosis is a rare hereditary bone metabolic disease, characterized by increased bone mass and density caused by bone resorption disorders, and any abnormal mutation involving osteoclast maturation or function will lead to the occurrence of osteopetrosis. Clinically, the prevalence of autosomal dominant osteopetrosis type Ⅱ(ADO-Ⅱ) is higher than that of other types of osteopetrosis, which involves multiple systems such as endocrine, bone, blood, nerve, ear-nose-throat, and oral cavity. Disease progression is insidious and easily overlooked, and there is no standard treatment. This article summarizes the clinical characteristics, examination data, diagnosis and treatment process of the two patients, analyzes multi-system symptoms, pathogenesis and treatment principles of the disease to improve the management of patients with ADO-Ⅱ.

Generation and phenotype of myeloid cell specific Clcn7-mutation osteopetrosis mouse model / 中华内分泌代谢杂志

Objective:To construct a myeloid cell specific Clcn7-G763R mutant mouse model and characterize its phenotype.Methods:A mouse conditional knocked in p. G763R mutation in Clcn7 gene was constructed and bred with LysM cre mice to obtain osteopetrosis mice with myeloid cell specific Clcn7-G763R mutation. The differences of bone mass in mice with different genotypes were analyzed using Micro CT and the changes of histology were observed with HE staining. Osteoclasts were cultured and the expression levels of osteoclasts differentiation and maturation-related genes were detected by real-time PCR. The functions of osteoclasts were examined through bone resorption assay.Results:The body weight of homozygous mutant mice at 4 weeks old was reduced compared with the wild type mice [(12.000±1.666)g vs(15.630±2.314)g, P=0.021], with shorter femur length [(1.160±0.096)cm vs (1.300±0.082)cm, P=0.037]. Micro CT showed that bone mineral density of homozygous mutant mice was remarkably increased at 4 weeks old [(0.753±0.002)g/cm 3vs(0.143±0.034)g/cm 3, P=0.003], while bone mineral density of heterozygous mutant mice increased significantly at 8 weeks old [(0.236±0.021)g/cm 3vs(0.180±0.020)g/cm 3, P=0.030]. HE staining revealed increased trabecula bone volume in the mutant mice, especially in homozygous mutant mice with narrow bone marrow cavity and wider hypertrophic zone of chondrocytes. There was no significant difference in the number of osteoclasts between wild type mice and heterozygous mice in vitro( P=0.358), while total area of osteoclasts increased in heterozygous mutant mice [(3.590×10 6±0.911×10 6)μm 2vs(1.352×10 6±0.260×10 6)μm 2, P=0.043]. Impaired function of resorption was unveiled by bone resorption assay. There were no significant differences in the expressions of osteoclast differentiation and maturity-related genes including NFATc1, c-fos, Ctsk, and Acp5 between the two groups. Conclusion:A myeloid cell specific Clcn7-G763R mutation mice with impaired osteoclasts and increased bone mass is successfully constructed.

Genetic Analysis of CLCN7 in an Old Female Patient with Type II Autosomal Dominant Osteopetrosis

BACKGROUND: Type II autosomal dominant osteopetrosis (ADO II) is a rare genetically heterogeneous disorder characterized by osteosclerosis and increased bone mass, predominantly involving spine, pelvis, and skull. It is closely related to functional defect of osteoclasts caused by chloride voltage-gated channel 7 (CLCN7) gene mutations. In this study, we aimed to identify the pathogenic mutation in a Korean patient with ADO II using whole exome sequencing. METHODS: We evaluated the clinical, biochemical, and radiographic analysis of a 68-year-old woman with ADO II. We also performed whole exome sequencing to identify pathogenic mutation of a rare genetic disorder of the skeleton. Moreover, a polymorphism phenotyping program, Polymorphism Phenotyping v2 (PolyPhen-2), was used to assess the effect of the identified mutation on protein function. RESULTS: Whole exome sequencing using peripheral leukocytes revealed a heterozygous c.296A>G missense mutation in the CLCN7 gene. The mutation was also confirmed using Sanger sequencing. The mutation c.296A>G was regarded to have a pathogenic effect by PolyPhen-2 software. CONCLUSION: We detect a heterozygous mutation in CLCN7 gene of a patient with ADO II, which is the first report in Korea. Our present findings suggest that symptoms and signs of ADO II patient having a c.296A>G mutation in CLCN7 may appear at a very late age. The present study would also enrich the database of CLCN7 mutations and improve our understanding of ADO II.

Novel mutations in Indian patients with autosomal recessive infantile malignant osteopetrosis.

Background & objectives: Although clinical reports have described infantile malignant autosomal recessive osteopetrosis (ARO) in Indian patients, no published data are available about the genetic causes of ARO in this population. We investigated the main genetic causes of ARO in eight Indian patients with early postnatal onset and the typical severe clinical course including visual impairment and anaemia. Methods: Mutation screening in the genes CLCN7 and TCIRG1 was done on genomic DNA from 8 affected individuals (diagnosed on the basis of clinical and haematological parameters and characteristic radiological changes of increased bone density) and their parents. In one family, after detection of both mutations in the proband, targeted mutation analysis was also done in chorionic villus samples for prenatal diagnosis. Results: Six patients had mutations in TCIRG1 and two patients harboured mutations in CLCN7 gene. Three of the five different TCIRG1 mutations identified and both CLCN7 mutations were novel mutations. Except for the already known mutation p.Ile720del, all TCIRG1 mutations disrupt conserved splice consensus sequences or lead to premature stop codons. In contrast, both CLCN7 mutations only lead to missense changes of conserved amino acids. In a foetus harbouring TCIRG1 mutations osteopetrosis was visible radiologically at 23 wk of gestation. Interpretation & conclusions: That the CLCN7 mutations provoke a phenotype as severe as the one caused by TCIRG1 loss of function suggests the affected residues to be crucial for the function of the ClC-7 chloride channel or chloride/proton-exchanger. Our data also show that ARO can manifest as early as in the second trimester of pregnancy.