Indian hedgehog mutations causing brachydactyly type A1 impair Hedgehog signal transduction at multiple levels  

作　　者：Gang Ma Jiang Yu Yue Xiao Danny Chan Bo Gao Jianxin Hu Yongxing He Shengzhen Guo Jian Zhou Lingling Zhang Linghan Gao Wenjuan Zhang Yan Kang Kathryn SE Cheah Guoyin Feng Xizhi Guo Yujiong Wang Cong-zhao Zhou Lin He 

机构地区：[1]Bio-X Center, Key Laboratory for the Genetics of Developmental and Neuropsychiatric Disorders (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200030, China [2]Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences (S1BS), Chinese Academy of Sciences, Shanghai 200031, China [3]Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei 230027, China [4]Department of Biochemistry, the University of Hong Kong, Pokfulam, Hong Kong, China [5]Centre for Reproduction, Development and Growth, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, China [6]Shanghai Institute of Mental Health, Shanghai 200030, China [7]Life Science School, Ningxia University Yinchuan 750021, China [8]Institutes of Biomedical Sciences, Fudan University, Shanghai 200032, China

出　　处：《Cell Research》2011年第9期1343-1357,共15页细胞研究（英文版）

基　　金：This work was supported by the National Natural Science Foundation of China （30800613）, the 973 Program （2010CB529600, 2007CB947300）, the 863 Program （2009AA022701）, the Shanghai Municipal Commission of Science and Technology Program （09DJ1400601）, the Natural Science Foundation of Shanghai, China （Grant No. 08ZR1411000）, the National Key Project for the Investigation of New Drugs （2008ZX09312-003）, the Shanghai Leading Academic Discipline Project （B205）, and the General Research Fund of Hong Kong （HKU760608M）. The coauthor, Xizhi Guo, was supported by the ＂Pujiang Talent＂ Project （08PJ1407200）.

摘　　要：Brachydactyly type A1 （BDAI）, the first recorded Mendelian autosomal dominant disorder in humans, is characterized by a shortening or absence of the middle phalanges. Heterozygous missense mutations in the Indian Hedgehog （IHH） gene have been identified as a cause of BDA1; however, the biochemical consequences of these mutations are unclear. In this paper, we analyzed three BDA1 mutations （E95K, D100E, and E131K） in the N-terminal fragment of Indian Hedgehog （IhhN）. Structural analysis showed that the E95K mutation changes a negatively charged area to a positively charged area in a calcium-binding groove, and that the D100E mutation changes the local tertiary structure. Furthermore, we showed that the E95K and D100E mutations led to a temperature-sensitive and calcium-dependent instability of IhhN, which might contribute to an enhanced intracellular degradation of the mutant proteins via the lysosome. Notably, all three mutations affected Hh binding to the receptor Patchedl （PTC1）, reducing its capacity to induce cellular differentiation. We propose that these are common features of the mutations that cause BDA1, affecting the Hh tertiary structure, intracellular fate, binding to the receptor/partners, and binding to extracellular components. The combination of these features alters signaling capacity and range, but the impact is likely to be variable and mutation-dependent. The potential variation in the signaling range is characterized by an enhanced interaction with heparan sulfate for IHH with the E95K mutation, but not the E131K mutation. Taken together, our results suggest that these IHH mutations affect Hh signaling at multiple levels, causing abnormal bone development and abnormal digit formation.

关 键 词：Indian hedgehog BDA1 diffusion HEPARIN crystal structure degradation 

分 类 号：Q754[生物学—分子生物学] Q257