Functional characterization of genetic variants in NPC1L1 supports the sequencing extremes strategy to identify complex trait genes
Functional characterization of genetic variants in NPC1L1 supports the sequencing extremes strategy to identify complex trait genes
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DOI：
10.1093/hmg/ddn108
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发表时间：
2008-07-15
影响因子：
3.5
通讯作者：
Cohen, Jonathan C.
中科院分区：
文献类型：
--
作者：
Fahmi, Saleemah;Yang, Chendong;Cohen, Jonathan C.
在种群分布的两端对个体的基因进行重新测序是识别与复杂性状相关的序列变异的一种强大而有效的策略。一个极端的序列变异相对于另一个极端的过量，不是由于偶然或种群分层造成的，这构成了遗传关联的证据，并暗示存在功能上显著的序列变异。最近，我们报道了肠道胆固醇转运蛋白Niemann-Pick类型C1L1(NPC1L1)的非同义序列变异在胆固醇吸收低的个体中明显多于胆固醇吸收高的个体。为了确定在低胆固醇吸收个体中发现的序列变异是否会影响蛋白质功能，我们在培养细胞和家庭中进行了研究。突变蛋白在中国仓鼠卵巢-K1细胞中的表达表明，在低吸光度的细胞中发现的大多数(14/20)突变与非常低的NPC1L1蛋白水平有关。在两个扩大的家族中，使用稳定同位素测量的平均胆固醇吸收水平，在有序列变异的家族成员中显著低于没有变异的家族成员。这些数据表明，具有极端表型的个体中过多的序列变异反映了功能上有意义的变异的丰富。这些发现与电子计算机预测一致，即在健康个体中发现的一些序列变异与其他基因中导致单基因疾病的突变一样有害于蛋白质功能。这样的序列变异可能解释了人类数量表型变异的很大一部分。
Resequencing genes in individuals at extremes of the population distribution constitutes a powerful and efficient strategy to identify sequence variants associated with complex traits. An excess of sequence variants at one extreme relative to the other that is not due to chance or to population stratification constitutes evidence for genetic association and implies the presence of functionally significant sequence variants. Recently, we reported that non-synonymous sequence variants in Niemann-Pick type C1-like 1 (NPC1L1), an intestinal cholesterol transporter, were significantly more common among individuals with low cholesterol absorption than in those with high cholesterol absorption. To determine whether sequence variations identified in individuals with low cholesterol absorption affect protein function, we performed studies in cultured cells and in families. Expression of the mutant proteins in Chinese hamster ovarian-K1 cells revealed that a majority (14 of 20) of the variants identified in low absorbers were associated with very low levels of NPC1L1 protein. In two extended families, mean cholesterol absorption levels, as measured using stable isotopes, were significantly lower in family members with the sequence variants than in those without the variant. These data indicate that the excess of sequence variations in individuals with extreme phenotypes reflects an enrichment of functionally significant variants. These findings are consistent with in silico predictions that some sequence variations found in healthy individuals are as deleterious to protein function as mutations that, in other genes, cause monogenic diseases. Such sequence variations may explain a significant fraction of quantitative phenotypic variation in humans.