title: Enhanced but hypofunctional osteoclastogenesis in an autosomal dominant osteopetrosis type II case carrying a c.1856C>T mutation inCLCN7.
abstract: Type II autosomal dominant osteopetrosis (ADO2), which is the most common form of osteopetrosis, is caused by heterozygous mutations in the chloride channel 7 (CLCN7) gene. The osteopetrosis of ADO2 has been attributed to hypofunctional osteoclasts. The mechanism underlying the abnormality in osteoclast function remains largely unknown. This study was designed to investigate gene mutations and osteoclast function in a case that was clinically diagnosed as ADO2. Genomic DNA was extracted from blood samples of this patient, and the 25 exons ofCLCN7were amplified. Peripheral blood from the ADO2 subject and a healthy age- and sex-matched control was used to evaluate osteoclastogenesis, osteoclast morphology, and bone resorption. Analysis of DNA from the patient showed a germline heterozygous missense mutation, c.1856C>T (p.P619L), in exon 20 ofCLCN7. A similar homozygous mutation at this site was previously reported in a patient with autosomal recessive osteopetrosis. When cultured, the peripheral blood mononuclear cells (PBMCs) from the ADO2 patient spontaneously differentiated into mature osteoclastsin vitro. The ADO2 patient's PBMCs formed enhanced, but heterogeneous, osteoclasts in both the presence and absence of macrophage-colony stimulating factor, and nuclear factor-ĸB ligand. Bone resorption was reduced in the ADO2 patient's osteoclasts, which exhibited aberrant morphology and abnormal distribution of integrin avβ3. Gene analysis found increasedc-fosexpression and reducedRhoAandintegrin beta 3expression in ADO2 cells. In conclusion, our data suggest that enhanced, heterogeneous osteoclast induction may be an intrinsic characteristic of ADO2.
authors.affiliation: Laboratory of Endocrinology and Metabolism, Department of Endocrinology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University , Chengdu, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Chen
authors.affiliation: Laboratory of Endocrinology and Metabolism, Department of Endocrinology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University , Chengdu, China.
authors.forename: Kun
authors.initials: K
authors.lastname: Zhang
authors.affiliation: The Polis Center, Indiana University-Purdue University Indianapolis , Indianapolis, IN, USA.
authors.forename: Janet
authors.initials: J
authors.lastname: Hock
authors.affiliation: Laboratory of Endocrinology and Metabolism, Department of Endocrinology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University , Chengdu, China.
authors.forename: Chunyu
authors.initials: C
authors.lastname: Wang
authors.affiliation: Laboratory of Endocrinology and Metabolism, Department of Endocrinology, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University , Chengdu, China.
authors.forename: Xijie
authors.initials: X
authors.lastname: Yu