Novel Wnt effectors in renal cystic disease

描述(申请人提供)：尽管在识别人类遗传病的潜在突变方面取得了显著进展，但基因的预测能力仍然很差，部分原因是每个患者的最终临床结果是致病突变和第二位点修饰等位基因之间上位相互作用以及随机和环境影响的净结果。Bardet-Biedl综合征(BBS)是研究上位性疾病的有用模型；几项研究表明，改变12个致病基因中的每一个基因以及其他转录本中的等位基因，可以调节疾病的外显性和表达能力。BBS也代表了一种典型的纤毛病变，这是一组临床上截然不同但表型重叠的疾病，包括多囊肾病(PKD)、肾单位病变(NPHP)、Joubert综合征(JS)和Meckel-Gruber综合征(MKS)。最近的数据表明，纤毛及其锚定结构，即基底体，是传递形态发生线索所必需的，这一过程的失败可能与一些观察到的临床表型有关，如肾囊性疾病。一些BBS蛋白功能的丧失被证明扰乱了非规范的Wnt信号，这反过来又与患者和脊椎动物模型中发现的一些囊性表型有关。着眼于Wnt信号对肾脏表型的贡献，我们推测，将会有一些蛋白质能够通过加剧、改善或挽救有缺陷的Wnt传递来调节一个BBS基因座功能突变丧失的生化效应。根据定义，编码这些分子的转录本代表了在人类中贡献外显性和表达能力改变等位基因的主要候选基因，这些基因的识别将：a)指数级地提高我们对人类遗传负荷的理解；b)促进这种疾病的临床治疗；以及c)可能与其他纤毛疾病的肾囊性疾病的发展相关。为了进一步探索这些可能性，我们建议1)利用shRNA、表达载体和发光报告的组合，研究新定义的纤毛蛋白质组中约500个成员在调节BBS突变肾细胞Wnt信号反应中的作用；2)通过筛选与疾病表型相关的候选基因并对我们的BBS队列中的修饰等位基因进行测序，来探索这些潜在的修饰蛋白在调控BBS患者肾脏表型方面的生理相关性。

DESCRIPTION (provided by applicant): Despite the remarkable advances in identifying mutations underlying human genetic disease, the predictive power of the genotype remains poor, in part because the ultimate clinical outcome in each patient is the net result of epistatic interactions between disease causing mutations and second site modifying alleles, as well as stochastic and environmental effects. Bardet-Biedl syndrome (BBS) represents a useful model to study epistasis; several studies have shown that modifying alleles in each of the twelve causative genes, as well as in other transcripts, modulate the penetrance and expressivity of the disorder. BBS also represents a model ciliopathy, an emerging group of clinically distinct but phenotypically overlapping disorders that include polycystic kidney disease (PKD), Nephronophthisis (NPHP), Joubert syndrome (JS) and Meckel-Gruber syndrome (MKS). Recent data have shown that the cilium, and its anchoring structure, the basal body, are required for the transmission morphogenetic cues and that failure of this process can be causally associated with some of the observed clinical phenotypes, such as renal cystic disease. Loss of function of several BBS proteins has been shown to disrupt non-canonical Wnt signaling, which in turn has been associated with some of the cystic phenotypes found in patients and vertebrate animal models. Focusing on the contribution of Wnt signaling to the renal phenotype, we reason that there will be proteins that have the ability to modulate the biochemical effect of loss of function mutations at one BBS locus by either exacerbating, ameliorating, or rescuing defective Wnt transmission. By definition, the transcripts that encode these molecules represent major candidates for contributing penetrance and expressivity modifying alleles in humans, the identification of which will: a) improve exponentially our understanding of genetic load in humans; b) facilitate the clinical management of the disorder; and c) be potentially relevant to the development of renal cystic disease in other ciliopathies. To explore these possibilities further, we propose to 1) investigate ~500 members of the newly defined ciliary proteome in modulating the Wnt signaling response in BBS mutant renal cells by utilizing a combination shRNAs, expression vectors, and luminescent reporters, and 2) explore the physiological relevance of these potential modifier proteins in modulating the renal phenotype of BBS patients by screening candidate genes for a haplotype signature that associates with disease phenotype and sequencing our BBS cohort for modifier alleles.