Characterization of a Relatively Malignant Form of Osteopetrosis Caused by a Novel Mutation in the PLEKHM1 Gene.
Osteopetrosis (OMIM: 611497), literally "stone bone," is a group of inherited bone disorders characterized by increased skeletal mass due to defective osteoclast function. A patient who reported a history of frequent fractures, weakness and fatigue was admitted to our hospital in 2011. The patient presented with the typical features of osteopetrosis: fractures after minor trauma, early tooth loss, anemia, hepatosplenomegaly, and a generalized increase in bone mineral density (BMD). Aside from his father's complaint of excessive tooth loss, his mother, two sisters, son, and daughter were healthy. Blood samples of the family members were drawn for genetic analyses. The entire coding region and adjacent splice sites of the pleckstrin homology domain-containing family M (with RUN domain) member 1 (PLEKHM1) gene were sequenced. One mutation, a heterozygous deletion mutation in exon 11 (c.3051_3052delCA), was identified in the patient but not in his relatives. The mutation leads to a translation product with a highly impaired Rubicon homology domain. Co-immunoprecipitation and immunofluorescence analyses using HEK293 cells showed that overexpression of a PLEKHM1 CA-deletion mutant resulted in a dramatic decrease in the interaction between PLEKHM1 and the small GTPase Rab7 compared to wild-type PLEKHM1. The normal processes of endocytosis and autophagy were disturbed in cells expressing the mutant (transfected HEK293 and U937 cells), as indicated by epidermal growth factor receptor (EGFR) degradation and an altered LC3-I/II ratio, respectively, which may lead to a defect in osteoclast function. A four-year follow-up study of the patient showed that the PLEKHM1-dependent osteopetrosis was relatively malignant, with significant symptoms of pancytopenia and hepatosplenomegaly. © 2016 American Society for Bone and Mineral Research.
Scientific Center, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.|Institute of Endocrinology, Shandong Academy of Clinical Medicine, Jinan, Shandong, China.
Tao
T
Bo
Department of Pain Management, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Fang
F
Yan
Institute of Endocrinology, Shandong Academy of Clinical Medicine, Jinan, Shandong, China.|Department of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Jun
J
Guo
Pathology Department, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Xiaoyan
X
Lin
Institute of Endocrinology, Shandong Academy of Clinical Medicine, Jinan, Shandong, China.|Department of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Haiqing
H
Zhang
Institute of Endocrinology, Shandong Academy of Clinical Medicine, Jinan, Shandong, China.|Department of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Qingbo
Q
Guan
Institute of Endocrinology, Shandong Academy of Clinical Medicine, Jinan, Shandong, China.|Department of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Hai
H
Wang
Institute of Endocrinology, Shandong Academy of Clinical Medicine, Jinan, Shandong, China.|Department of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Li
L
Fang
Institute of Endocrinology, Shandong Academy of Clinical Medicine, Jinan, Shandong, China.|Department of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Ling
L
Gao
Institute of Endocrinology, Shandong Academy of Clinical Medicine, Jinan, Shandong, China.|Department of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Jiajun
J
Zhao
Institute of Endocrinology, Shandong Academy of Clinical Medicine, Jinan, Shandong, China.|Department of Endocrinology and Metabolism, Shandong Provincial Hospital affiliated to Shandong University, Jinan, Shandong, China.
Chao
C
Xu
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D001343:Autophagy; D000071183:Autophagy-Related Proteins; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004705:Endocytosis; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D010022:Osteopetrosis / Q000000981:diagnostic imaging / Q000235:genetics* / Q000473:pathology*; D011485:Protein Binding; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins
D048868:Adaptor Proteins, Signal Transducing; D000071183:Autophagy-Related Proteins; D008562:Membrane Glycoproteins; C476215:PLEKHM1 protein, human; D000090802:rab7 GTP-Binding Proteins; C000716463:rab7 GTP-binding proteins, human; D020691:rab GTP-Binding Proteins
OSTEOCLASTS; OSTEOPETROSIS; PARATHYROID-RELATED DISORDERS