SMAD3 mutation in LDS3 causes bone fragility by impairing the TGF-β pathway and enhancing osteoclastogenesis

作     者：El-Gazzar, Ahmed Kang, Heeseog Fratzl-Zelman, Nadja Webb, Emma Barnes, Aileen M. Jovanovic, Milena Mehta, Sarju G. Datta, Vipan Saraff, Vrinda Dale, Ryan K. Rauch, Frank Marini, Joan C. Hoegler, Wolfgang 

作者机构：Johannes Kepler Univ Linz Dept Paediat & Adolescent Med Linz Austria Eunice Kennedy Shriver Natl Inst Child Hlth & Hum Sect Heritable Disorders Bone & Extracellular Mat NIH Bethesda MD USA Hanusch Hosp Ludwig Boltzmann Inst Osteol OEGK & AUVA Trauma Ctr Meidling Med Dept 1 Vienna Austria Vienna Bone & Growth Ctr Vienna Austria Norfolk & Norwich Univ Hosp NHS Fdn Trust Jenny Lind Childrens Hosp Dept Paediat Norwich Norfolk England Univ East Anglia Norwich Med Sch Norwich Norfolk England Addenbrookes Hosp East Anglian Reg Med Genet Serv Cambridge England Birmingham Womens & Childrens Hosp NHS Fdn Trust Dept Endocrinol & Diabet Birmingham W Midlands England Eunice Kennedy Shriver Natl Inst Child Hlth & Hum Bioinformat & Sci Programming Core Bethesda MD USA Shriners Hosp Children Canada Montreal PQ H4A 0A9 Canada McGill Univ Dept Human Genet Montreal PQ H3A 0C7 Canada Univ Birmingham Inst Metab & Syst Res Birmingham W Midlands England Univ Texas Southwestern Med Ctr Dallas Dept Surg Dallas TX USA 

出 版 物：《BONE REPORTS》 (Bone Rep.)

年 卷 期：2022年第17卷

页      面：101603页

学科分类：1002[医学-临床医学] 100210[医学-外科学(含：普外、骨外、泌尿外、胸心外、神外、整形、烧伤、野战外)] 10[医学] 

基　　金：Austrian Social Health Insurance Fund (OEGK) Austrian Social Health Compensation Board (AUVA) 

主　　题：Loeys-Dietz syndrome SMAD3 TGF-beta-signaling Osteoclastogenesis Fractures 

摘      要：Loss-of-function mutations in SMAD3 cause Loeys-Dietz syndrome type 3 (LDS3), a rare autosomal-dominant connective tissue disorder characterized by vascular pathology and skeletal abnormalities. Dysregulation of TGF-beta/SMAD signaling is associated with abnormal skeletal features and bone fragility. To date, histomorpho-metric and ultrastructural characteristics of bone with SMAD3 mutations have not been reported in humans and the exact mechanism by which SMAD3 mutations cause the LDS3 phenotype is poorly understood. Here, we investigated bone histomorphometry and matrix mineralization in human bone with a SMAD3 mutation and explored the associated cellular defect in the TGF-beta/SMAD pathway in vitro. The index patient had recurrent fractures, mild facial dysmorphism, arachnodactyly, pectus excavatum, chest asymmetry and kyphoscoliosis. Bone histomorphometry revealed markedly reduced cortical thickness (-68 %), trabecular thickness (-32 %), bone formation rate (-50 %) and delayed mineralization. Quantitative backscattered electron imaging demonstrated undermineralized bone matrix with increased heterogeneity in mineralization. The patient s SMAD3 mutation (c.200 T G;p.I67S), when expressed from plasmid vectors in HEK293 cells, showed reduced phosphorylation and transcription factor activity compared to normal control and SMAD3 (p.S264Y), a gain-of -function mutation, somatic mosaicism of which causes melorheostosis. Transfection study of the patients SMAD3 (p.I67S) mutation displayed lower luciferase reporter activity than normal SMAD3 and reduced expression of TGF-beta signaling target genes. Patient fibroblasts also demonstrated impaired SMAD3 protein stability. Osteo-clastogenic differentiation significantly increased and osteoclast-associated genes, including ACP5 (encoding TRAP), ATP6V0D2, and DCSTAMP, were up-regulated in CD14 (+) peripheral blood mononuclear cells (PBMCs) with the SMAD3 (p.I67S) mutation. Upregulation of osteoclastogenic genes was associ