title: A gain-of-function mutation in Tnni2 impeded bone development through increasing Hif3a expression in DA2B mice.
abstract: Distal arthrogryposis type 2B (DA2B) is an important genetic disorder in humans. However, the mechanisms governing this disease are not clearly understood. In this study, we generated knock-in mice carrying a DA2B mutation (K175del) in troponin I type 2 (skeletal, fast) (TNNI2), which encodes a fast-twitch skeletal muscle protein. Tnni2K175del mice (referred to as DA2B mice) showed typical DA2B phenotypes, including limb abnormality and small body size. However, the current knowledge concerning TNNI2 could not explain the small body phenotype of DA2B mice. We found that Tnni2 was expressed in the osteoblasts and chondrocytes of long bone growth plates. Expression profile analysis using radii and ulnae demonstrated that Hif3a expression was significantly increased in the Tnni2K175del mice. Chromatin immunoprecipitation assays indicated that both wild-type and mutant tnni2 protein can bind to the Hif3a promoter using mouse primary osteoblasts. Moreover, we showed that the mutant tnni2 protein had a higher capacity to transactivate Hif3a than the wild-type protein. The increased amount of hif3a resulted in impairment of angiogenesis, delay in endochondral ossification, and decrease in chondrocyte differentiation and osteoblast proliferation, suggesting that hif3a counteracted hif1a-induced Vegf expression in DA2B mice. Together, our data indicated that Tnni2K175del mutation led to abnormally increased hif3a and decreased vegf in bone, which explain, at least in part, the small body size of Tnni2K175del mice. Furthermore, our findings revealed a new function of tnni2 in the regulation of bone development, and the study of gain-of-function mutation in Tnni2 in transgenic mice opens a new avenue to understand the pathological mechanism of human DA2B disorder.
authors.affiliation: Key Laboratory of Geriatrics, Beijing Hospital and Beijing Institute of Geriatrics, Ministry of Health, Beijing, China; National Institute of Biological Sciences (NIBS), Beijing, China.
authors.forename: Xiaoquan
authors.initials: X
authors.lastname: Zhu
authors.affiliation: National Institute of Biological Sciences (NIBS), Beijing, China.
authors.forename: Fengchao
authors.initials: F
authors.lastname: Wang
authors.affiliation: Key Laboratory of Geriatrics, Beijing Hospital and Beijing Institute of Geriatrics, Ministry of Health, Beijing, China.
authors.forename: Yanyang
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: National Institute of Biological Sciences (NIBS), Beijing, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Yang
authors.affiliation: National Institute of Biological Sciences (NIBS), Beijing, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.affiliation: National Institute of Biological Sciences (NIBS), Beijing, China.
authors.forename: Hanzi
authors.initials: H
authors.lastname: Sun
authors.affiliation: National Institute of Biological Sciences (NIBS), Beijing, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.affiliation: National Institute of Biological Sciences (NIBS), Beijing, China.
authors.forename: Wenjun
authors.initials: W
authors.lastname: Li
authors.affiliation: Clinical Institute of China-Japan Friendship Hospital, Beijing, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Pan
authors.affiliation: Clinical Institute of China-Japan Friendship Hospital, Beijing, China.
authors.forename: Yanru
authors.initials: Y
authors.lastname: Guo
authors.affiliation: National Institute of Biological Sciences (NIBS), Beijing, China.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Kou
authors.affiliation: National Institute of Biological Sciences (NIBS), Beijing, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Radiology, Beijing Hospital, Ministry of Health, Beijing, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Department of Epidemiology, School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana, United States of America.
authors.forename: Jiang
authors.initials: J
authors.lastname: He
authors.affiliation: Center for Genetic Medicine and State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Zhang
authors.affiliation: The Key Laboratory of Reproductive Health, Liaoning, China.
authors.forename: Jianxin
authors.initials: J
authors.lastname: Li
authors.affiliation: The Key Laboratory of Reproductive Health, Liaoning, China.
authors.forename: Weitian
authors.initials: W
authors.lastname: Han
authors.affiliation: Key Laboratory of Geriatrics, Beijing Hospital and Beijing Institute of Geriatrics, Ministry of Health, Beijing, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Liu
authors.affiliation: National Institute of Biological Sciences (NIBS), Beijing, China; School of Life Sciences and Technology, Tongji University, Shanghai, China.
authors.forename: Shaorong
authors.initials: S
authors.lastname: Gao
authors.affiliation: Key Laboratory of Geriatrics, Beijing Hospital and Beijing Institute of Geriatrics, Ministry of Health, Beijing, China.
authors.forename: Ze
authors.initials: Z
authors.lastname: Yang
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D001176:Arthrogryposis / Q000235:genetics* / Q000503:physiopathology; D001846:Bone Development / Q000235:genetics*; D002118:Calcium / Q000378:metabolism; D005786:Gene Expression Regulation; D055879:Gene Knock-In Techniques; D006801:Humans; D051379:Mice; D009119:Muscle Contraction / Q000235:genetics; D009154:Mutation; D012097:Repressor Proteins; D012518:Sarcomeres / Q000473:pathology; D014157:Transcription Factors / Q000096:biosynthesis* / Q000235:genetics; D019210:Troponin I / Q000235:genetics*; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis
chemical_list: D051017:Apoptosis Regulatory Proteins; C444643:Hif3a protein, mouse; D012097:Repressor Proteins; C518658:TNNI2 protein, human; D014157:Transcription Factors; D019210:Troponin I; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D002118:Calcium