Leung Adrian On-Wah, Yiu Tsz-Ching, Liu Lingxiao, Tam Hei-Yin, Gu Shen, Tu Jiajie, Pei Duanqing, Cheung Hoi-Hung
Key Laboratory for Regenerative Medicine, Ministry of Education, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, China.
Centre for Regenerative Medicine and Health, Hong Kong Institute of Science and Innovation, Chinese Academy of Sciences, Hong Kong SAR, China.
Cell Biosci. 2022 Dec 31;12(1):212. doi: 10.1186/s13578-022-00939-8.
Pathogenic mutations in WRN are a cause of premature aging disease Werner syndrome (WS). Besides accelerated aging phenotypes and cancer predisposition, patients with WS also display underdevelopment in the skeletal system, characterized by short stature, light body weight and unusually thin extremities. The reasons for these developmental defects are not completely understood and the underlying molecular mechanism remains to be elucidated.
In this study, WRN was found to modulate transcription of short stature homeobox gene SHOX. Loss of WRN resulted in insufficient expression of SHOX, the gene dose of which is critical for driving chondrocyte differentiation. WRN could bind the G-quadruplex (G4) structures in the SHOX promoter and stimulate transcription. Aberrant formation of G4 structures in WRN-deficient cells impeded normal transcription of SHOX, thus resulting in impaired chondrogenesis. Chondrogenesis could be rescued by overexpression of WRN helicase or SHOX, suggesting that SHOX is a downstream target of WRN. Gene editing of the G4 structures in the SHOX promoter could increase SHOX expression, therefore rescuing the impaired chondrogenesis in WRN-deficient cells.
Our data suggest that dysgenesis of the developing bone in WS might be caused by SHOX insufficiency. Aberrant formation of G4 structures in SHOX promoter suppresses SHOX expression and impairs chondrogenesis. Targeted mutagenesis in the G4 structures enhances SHOX expression and thus providing an opportunity to rescue the chondrogenic defect.
WRN基因的致病性突变是早衰疾病沃纳综合征（WS）的病因。除了加速衰老表型和癌症易感性外，WS患者的骨骼系统也发育不全，表现为身材矮小、体重轻和四肢异常纤细。这些发育缺陷的原因尚未完全了解，其潜在的分子机制仍有待阐明。
在本研究中，发现WRN可调节矮小同源框基因SHOX的转录。WRN的缺失导致SHOX表达不足，而SHOX的基因剂量对于驱动软骨细胞分化至关重要。WRN可结合SHOX启动子中的G-四链体（G4）结构并刺激转录。WRN缺陷细胞中G4结构的异常形成阻碍了SHOX的正常转录，从而导致软骨生成受损。过表达WRN解旋酶或SHOX可挽救软骨生成，这表明SHOX是WRN的下游靶点。对SHOX启动子中的G4结构进行基因编辑可增加SHOX表达，从而挽救WRN缺陷细胞中受损的软骨生成。
我们的数据表明，WS中发育骨骼的发育不全可能是由SHOX不足引起的。SHOX启动子中G4结构的异常形成抑制了SHOX表达并损害了软骨生成。对G4结构进行靶向诱变可增强SHOX表达，从而为挽救软骨生成缺陷提供了机会。
