The Investigation of disease causing genes in C. elegans

对于已知致病基因的人类常染色体隐性遗传病，我们希望使用C。研究该基因的功能，并从遗传学上鉴定在同一途径中起作用的其他因子。要使这一战略发挥作用，必须满足若干标准。首先，必须有一个令人信服的和明确的C。秀丽隐杆线虫直向同源物第二，这个基因中必须存在已经存在的突变或缺失（或者，我们可以使用TALEN技术来产生突变等位基因）。第三，必须有一个可评分的表型。表型越明显越好。如果满足这些标准，可以进行遗传抑制和增强筛选，以确定与任何给定基因及其功能的生物过程起作用的相互作用因子。我们目前正在确定符合所有这些标准的候选基因。 对于显性突变引起的疾病，我们的策略会有所不同。 我们可以尝试表达C.秀丽隐杆线虫直向同源物如果有一个渗透表型，我们可以描述它的特点，并使用遗传抑制和增强筛选，以确定在同一途径中发挥作用的其他因素。 对于不存在突变的基因，RNAi效果非常好，也可以用于筛选抑制子和增强子，以识别与给定基因相互作用的其他因子。我们之前已经成功地进行了一次抑制RNAi表型的筛选。 这种策略的一个明显的例子来自于观察到C.秀丽线虫引起多溃疡（Muv）表型。 对这些多瓣植物动物进行抑制筛选，希望能鉴定出抑制这种戏剧性表型的基因外突变。在这些筛选中鉴定了ksr-1基因（Sundaram和Han，1995; Kornfeld等人，1995）以及果蝇筛选（Therrein et al.，1995）;其名称代表ras激酶抑制剂。ksr-1的功能缺失等位基因抑制了C.优雅 三种人类ras基因中的任何一种突变被认为存在于至少30%的癌症中。K-Ras的特定突变被认为存在于90%的胰腺癌中。基于对人类细胞系的大量研究，KSR 1的抑制或消耗对生长无害。 事实上，在携带胰腺肿瘤的小鼠中抑制KSR 1表明这可能是用于此类肿瘤的可行疗法（Xing等人，2003年）。 因此，人们可能会认为KSR基因也是人类携带Ras突变的良好治疗靶点。 正如上面的例子所证明的那样，模拟抑制突变效应的药物可能是有价值的新疗法，用于治疗已知隐性突变导致抑制的疾病。在缺乏有效的基因治疗或干细胞治疗的情况下，靶向特定蛋白质的药物可能对患有此类疾病的患者有益。

For human autosomal recessive diseases in which the responsible gene is known, we would like to use C. elegans to study the function of that gene and to genetically identify other factors that act in the same pathway. There are a number of criteria that would have to be met in order for this strategy to work. First, there would have to be a convincing and clear C. elegans ortholog. Second, there would have to be a mutation or deletion in this gene that already exists (alternatively, we could use the TALEN technology to generate mutant alleles). Third, there would have to be a scorable phenotype. The more penetrant the phenotype, the better. If these criteria are met, genetic suppressor and enhancer screens could be performed to identify interacting factors that function with any given gene and the biological process in which it functions. We are currently in the process of identifying candidate genes that satisfy all of these criteria. For diseases caused by dominant mutations, our strategy would be different. We could attempt to express a dominant variant of the C. elegans ortholog. If there is a penetrant phenotype, we can characterize it and use genetic suppressor and enhancer screens to identify other factors that act in the same pathway. For genes that mutations do not exist, RNAi works extremely well and can also be used to screen for suppressors and enhancers to identify other factors interacting with a given gene. We have previously had success with a screen in which we suppressed an RNAi phenotype. One clear example of this strategy comes from the observation that an oncogenic ras mutant in C. elegans causes a Multivulva (Muv) phenotype. These Multivulva animals were subjected to suppressor screens in hopes of identifying extragenic mutations that suppress this dramatic phenotype. The ksr-1 gene was identified in these screens (Sundaram and Han, 1995; Kornfeld et al., 1995) and also in a Drosophila screen (Therrein et al., 1995); its name stands for kinase suppressor of ras. Loss-of-function alleles of ksr-1 suppress the dominant Multivulva phenotype of ras mutants in C. elegans. Mutations in any of the three human ras genes are thought to be present in at least 30% of all cancers. Specific mutations in K-Ras are thought to be present in 90% of all pancreatic cancers. Based on numerous studies in human cell lines, the inhibition or depletion of KSR1 is not detrimental to growth. In fact, the inhibition of KSR1 in mice bearing pancreatic tumor suggests that this might be a viable therapy for such tumors (Xing et al., 2003). Thus one could argue that the KSR gene would be a good therapeutic target for Ras-bearing mutations in humans as well. As demonstrated in the above example, drugs that mimic the effects of suppressor mutations might be worthy new therapies of diseases in which recessive mutations are known to be responsible for suppression. In the absence of effective gene therapy or stem cell therapy, drugs that target specific proteins may be beneficial to patients with such diseases.