COMPARATIVE GENETICS OF SKELETAL DEFECTS

描述（由申请人提供）：本研究的目的是了解先天性骨骼疾病导致明显发育和放射性骨改变的分子机制。PI特别关注两种进行性骨质增生疾病：货车Buchem病（VB）（MIM 239100）和硬化症（MIM 269500）。VB是一种严重的常染色体隐性遗传性骨病，以颅面畸形和全身性骨过度生长为特征。硬化症是一种与VB高度相似的骨骼发育不良，但具有更明显的放射学骨改变（颌骨;长骨;畸形）和手畸形（并指）。连锁分析将这两种疾病定位于同一基因座（17 q12-q21），发现硬化症患者在BMP拮抗剂基因Sclerostin（Sost）中携带几个编码突变。相反，VB患者没有表现出Sost编码突变，但是在Sost转录物下游35 kb处显示出52 kb的非编码缺失。在小鼠中使用人类转基因，PI已经证明了硬化症和VB是等位基因，并且52 kb的缺失去除了必需的Sost转录调控元件，改变了人类Sost表达模式。此外，在小鼠中，增加的Sost水平导致严重的肢体异常（融合和分裂的数字），而缺乏小鼠Sost导致骨质增生。这些初步观察表明，Sost在四肢发育过程中以及在整个成年期控制脊椎动物的骨稳态中起着关键作用。由于Sost从鱼类到人类高度保守，PI有兴趣阐明这种分子在不同脊椎动物骨骼发育过程中的作用。因此，这项资助的重点是破译Sost的几个基本性质，包括1）Sost特异性调控元件的鉴定和表征，2）确定Sost在肢体模式和成人骨稳态中的作用，以及3）调查Sost在不同脊椎动物谱系中的作用。

DESCRIPTION (provided by applicant): The goal of this research is to understand the molecular mechanisms by which congenital skeletal disorders lead to pronounced developmental and radiological bone alterations. In particular the PIs are interested in two progressive hyperosteosis disorders: Van Buchem disease (VB) (MIM 239100) and Sclerosteosis (MIM 269500). VB is a severe, autosomal-recessive bone disorder characterized by cranio-facial distortion and generalized bone overgrowth. Sclerosteosis is a skeletal dysplasia highly similar to VB but with more pronounced radiological bone alterations (jaw; long bones; gigantism) and the presence of hand abnormalities (syndactyly). Linkage analysis mapped both diseases to the same locus (17q12-q21), and Sclerosteosis patients were found to carry several coding mutations in the BMP-antagonist gene Sclerostin (Sost). In contrast, VB patients exhibit no Sost coding mutations, however displayed a 52kb noncoding deletion, 35kb downstream of the Sost transcript. Using human transgenes in mice, the PIs have demonstrated that sclerosteosis and VB are allelic, and that the 52kb deletion removes essential Sost transcriptional regulatory elements, altering the human Sost expression pattern. Also, in mice, increased levels of Sost result in severe limb abnormalities (fused and split digits), while the lack of mouse Sost leads to hyperosteosis. These initial observations suggest that Sost plays a critical role during limb development as well as throughout the adult-life controlling bone homeostasis in vertebrates. Since Sost is highly conserved from fishes to humans, the PIs are interested in elucidating the role of this molecule during skeletal development in different vertebrates. Accordingly, this grant focuses on deciphering several fundamental properties of Sost including 1) identification and characterization of Sost-specific regulatory elements, 2) determination of the role of Sost in limb patterning and adult bone homeostasis, and 3) investigation of the role of Sost across different vertebrate lineages.