BRIDGING GENES AND HEART DISEASE IN DOWNS SYNDROME

唐氏综合征(DS)是先天性心脏病(CHD)的主要病因，其中大部分与心内膜垫(EC)的形态发生缺陷有关。尽管缓冲形态发生的胚胎学过程被描述得很好，但从基因到缺陷的信号通路在很大程度上是未知的。这项研究的最终目标是定义DS-CHD的致病基因(S)，确定其在缓冲形态发生中的作用，并提供修改其表达的模型。该小组以前的工作基于人和小鼠模型定义了DS-CHD区域，并生成了一个序列就绪的重叠群，其完成的序列为300kb，剩余的序列为1/1999，以及21号染色体上4Mb候选区中30个cDNA的转录图谱，以及可能的候选序列的测序和特征。对人和鼠DS-CAM克隆的分析表明，一类高度保守的新型细胞黏附分子(CAM)是Ig超家族的一类新的细胞黏附分子，具有10个IG2结构域和6个纤维连接蛋白结构域，并具有胞外和跨膜形式。在心内膜垫、神经元、神经脊等上皮细胞诱导部位、已知的生心转录因子(Mef2)的启动子部位表达，结合其与DS-CHD小区域的映射位置，使DS CaM成为可能的候选基因。并不是所有包括DS-CHD区域在内的部分三体16小鼠模型都会患上心脏病。为了阐明ds-CAM在DS-CHD中的作用，房室特异性表达(心肌、心内膜、神经脊)的作用，DS-CAM室特异性过度表达的小鼠模型(心肌、心内膜、神经脊)，DS-CAM室特异性过度表达和缺乏表达的小鼠模型以及21号染色体基因对位于MMU 10的胶原VIa1/a2的可能贡献。我们提出4个目标：I和II缩小区域并检查人类表达；III-V(与UCSD小鼠核心和项目1合作)使用小鼠模型来测试DS-CAM是DS-CHD基因的假设，而VI定义DS-CHD区域中的其余基因。通过确定DS-CAM及其调节和相互作用分子的作用，这项工作将为孤立性房室间隔缺损、室间隔缺损、房间隔缺损和PS以及其他形式的单基因冠心病提供候选病因。了解DS CAM将有助于深入了解正常EC形态发生及其发育不良的途径，这些途径导致了大多数先天性异常导致的死亡。

Down syndrome (DS) is a major cause of congenital heart disease (CHD), of which most is related to defective morphogenesis of the endocardial cushions ( EC). Although the embryologic processes underlying cushion morphogenesis are elegantly described, the signalling pathways that lead from genes to defects are largely unknown. The ultimate goal of the research described in this proposal is to define the gen(s) responsible for DS-CHD, to define its role in cushion morphogenesis and to provide models in which to modify its expression. Previous work by this group has defined a DS-CHD region based on human and mouse models and has generated a sequence ready contig, with 300 kb of finished sequence and the remainder by 1/1999, and transcriptional map of 30 cDNAs in the 4 Mb candidate region on chromosome 21, as well as sequencing and characterization of a likely candidate., DS-CAM. Analysis of the human and mouse DS CAM clones reveal a highly conserved novel class of cell adhesion molecules (CAM) of the Ig superfamily with ten Ig2 and six fibronectin domains and both extracellular and transmembrane forms. Expression in the endocardial cushions, neurons, neural crest and other sites of epithelial induction, promoter sites for known cardiogenic transcription factors (Mef2), combine with its map position with a small DS-CHD region, to make DS Cam a likely candidate. Not all mouse models of partial trisomy 16 including the DS-CHD region develop heart disease. To elucidate the role of DS-CAM in DS-CHD, the role of compartment specific expression (myocardium, endocardium, neural crest), mouse models of DS-CAM compartment specific over-expression (myocardium, endocardium, neural crest), mouse models of DS-CAM compartment specific over-expression and lack of expression will be generated as will models to address the possible contribution of the chromosome 21 gene for collagen VIa1/a2 located on MMU 10. We propose 4 aims; I and II narrow the region and examine human expression; III-V (in collaboration with the UCSD Mouse Core and Project 1) use mouse models to test the hypothesis that DS-CAM is the gene for DS-CHD, and VI defines the remainder of genes in the DS-CHD region. By defining the role of DS-CAM and its regulatory and interacting molecules, this work will provide the candidate causes for isolated AVSD, VSD, ASD and PS as well as other forms of monogenic CHD. Understanding DS CAM will provide insight into pathways on normal EC morphogenesis and their maldevelopment that cause the majority of deaths due to congenital anomalies.