Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California, USA.
PLoS Genet. 2011 Nov;7(11):e1002344. doi: 10.1371/journal.pgen.1002344. Epub 2011 Nov 3.
A significant current challenge in human genetics is the identification of interacting genetic loci mediating complex polygenic disorders. One of the best characterized polygenic diseases is Down syndrome (DS), which results from an extra copy of part or all of chromosome 21. A short interval near the distal tip of chromosome 21 contributes to congenital heart defects (CHD), and a variety of indirect genetic evidence suggests that multiple candidate genes in this region may contribute to this phenotype. We devised a tiered genetic approach to identify interacting CHD candidate genes. We first used the well vetted Drosophila heart as an assay to identify interacting CHD candidate genes by expressing them alone and in all possible pairwise combinations and testing for effects on rhythmicity or heart failure following stress. This comprehensive analysis identified DSCAM and COL6A2 as the most strongly interacting pair of genes. We then over-expressed these two genes alone or in combination in the mouse heart. While over-expression of either gene alone did not affect viability and had little or no effect on heart physiology or morphology, co-expression of the two genes resulted in ≈50% mortality and severe physiological and morphological defects, including atrial septal defects and cardiac hypertrophy. Cooperative interactions between DSCAM and COL6A2 were also observed in the H9C2 cardiac cell line and transcriptional analysis of this interaction points to genes involved in adhesion and cardiac hypertrophy. Our success in defining a cooperative interaction between DSCAM and COL6A2 suggests that the multi-tiered genetic approach we have taken involving human mapping data, comprehensive combinatorial screening in Drosophila, and validation in vivo in mice and in mammalian cells lines should be applicable to identifying specific loci mediating a broad variety of other polygenic disorders.
当前人类遗传学面临的一个重大挑战是确定介导复杂多基因疾病的相互作用遗传位点。其中一个特征最为明显的多基因疾病是唐氏综合征（DS），它是由于 21 号染色体的一部分或全部额外复制引起的。21 号染色体远端末端附近的一个短区间导致先天性心脏病（CHD），多种间接遗传证据表明，该区域的多个候选基因可能导致这种表型。我们设计了一个分层遗传方法来鉴定相互作用的 CHD 候选基因。我们首先使用经过充分验证的果蝇心脏作为测定方法，通过单独表达和所有可能的成对组合来鉴定相互作用的 CHD 候选基因，并测试它们对节律或应激后心力衰竭的影响。这种全面的分析确定了 DSCAM 和 COL6A2 是相互作用最强的一对基因。然后，我们单独或组合地在小鼠心脏中过表达这两个基因。虽然单独过表达这两个基因中的任何一个都不会影响生存能力，并且对心脏生理学或形态学几乎没有影响，但这两个基因的共表达导致约 50%的死亡率和严重的生理和形态缺陷，包括房间隔缺损和心脏肥大。DSCAM 和 COL6A2 之间的合作相互作用也在 H9C2 心脏细胞系中观察到，并且对这种相互作用的转录分析表明涉及粘附和心脏肥大的基因。我们成功地定义了 DSCAM 和 COL6A2 之间的合作相互作用，这表明我们采用的多层次遗传方法，涉及人类图谱数据、果蝇的全面组合筛选以及在小鼠和哺乳动物细胞系中的体内验证，应该适用于鉴定介导广泛多种其他多基因疾病的特定基因座。
