Genetic Analysis Of Klotho In Diseases Of Aging

根据对klotho突变小鼠的研究，klotho基因已知在抑制几种不同的衰老表型中发挥作用。klotho基因缺陷的纯合子小鼠表现出一种与人类衰老非常相似的综合征，包括动脉粥样硬化、骨质疏松症、肺气肿、不孕症和皮肤萎缩。我们已经在一批来自杰克逊实验室的特征良好的小鼠品系中寻找klotho基因的序列变异。对这20个菌株中klotho基因的每个外显子进行了测序，这项工作现在正在提交给《基因组学》杂志。具体来说，我们发现：1。在该小组中的16个实验室来源的近交系菌株中没有发现任何变异。2.在4个野生型自交系中，共发现45个变异体，包括43个单核苷酸替换、1个缺失和1个插入。在核苷酸取代中，6个导致氨基酸取代。3.对野生型菌株中klotho基因表达的实时RT-PCR分析表明，SPRET/Ei中的基因表达水平高于其他野生型或实验室来源的菌株。4.膜形式与分泌形式的klotho mRNA的比率在具有氨基酸取代的三种野生衍生菌株中高于对照菌株。 我们发现，野生来源的物种SPRET/Ei中的klotho mRNA的表达水平约为实验室来源的菌株的两倍，并且有四个氨基酸变化，这一发现令人感兴趣，因为SPRET/Ei和实验室来源的菌株之间存在可能与klotho表达相关的几种表型差异。这些表型差异包括寿命长，听力异常，总胆固醇低和高HDL水平。有趣的是，MOLF/Ei在野生型菌株中表现出最低的klotho表达水平，在小鼠表型组项目中测试的43种菌株中具有最高的总胆固醇水平和最低的HDL百分比。 我们推测，klotho mRNA的改变和SPRET/Ei表达水平的增加可能会对年龄相关疾病如听力损失和冠状动脉疾病提供保护。小鼠中的特定klotho变体也可能与人类的长寿有关。 在巴尔的摩老龄化纵向研究的参与者中，我们的IRB批准的寻找Klotho基因功能变体的方案今年扩大到包括InChianti人群。在过去的一年里，我们对整个BLSA和InChianti人群进行了KL-VS等位基因的基因分型。在接下来的一年里，我们将在意大利人群中寻找Klotho基因的新变体。数据分析将涉及在BLSA和InChianti研究中检查的特定等位基因变体和表型之间的相关性。 一份描述BLSA人群动脉粥样硬化和Klotho等位基因状态的初步分析的摘要被送往美国人类遗传学会，以在2003年10月的会议上发表：在巴尔的摩老龄化纵向研究中寻找Klotho等位基因变异和动脉粥样硬化的关联。A. Bektas，D. Taub，S. Najjar，D.穆勒湖费鲁奇角A.弗兰科马诺

The klotho gene is known to play a role in suppressing several different aging phenotypes, based on studies in the klotho mutant mouse. Mice homozygous for defects in the klotho gene exhibit a syndrome that closely resembles human aging, including atherosclerosis, osteoporosis, emphysema, infertility and skin atrophy. We have looked for sequence variation in the klotho gene in a paenl of well-characterized mouse strains from the Jackson Laboratory. Each exon of the klotho gene was sequenced in each of these 20 strains.This work is now being submitted to the journal Genomics. Specifically, we have found: 1. No variation was found in any of the 16 laboratory derived inbred stains in the panel. 2.Among the 4 wild-derived inbred strains, 45 variants were found, including 43 single nucleotide substitutions, one deletion and one insertion. Of the nucleotide substitutions, six resulted in amino acid substitutions. 3.Real-time RT-PCR analysis of klotho gene expression in the wild-derived strains has shown a higher level of gene expression in SPRET/Ei than in the other wild-derived or laboratory-derived strains. 4. The ratio of membrane form to secreted form of klotho mRNA is higher in the three wild-derived strains with amino acid substitutions that in the control strains. Our finding that the klotho mRNA in the wild-derived species SPRET/Ei is expressed at approximately twice the level of laboratory derived strains and has four amino acid changes is intriguing in light of several phenotypic differences between SPRET/Ei and laboratory derived strains that may be related to klotho expression. These phenotypic differences include a long life-span, exceptional hearing, low total cholesterol and high HDL levels. Interestingly, MOLF/Ei, which exhibited the lowest klotho expression levels of the wild-derived strains, had the highest total cholesterol levels and lowest percent HDL of the 43 strains tested in the mouse phenome project. We hypothesize that klotho mRNA alterations and increased expression levels in SPRET/Ei may provide protection against age-related diseases such as hearing loss and coronary artery disease. It is also possible that specific klotho variants in mice may be associated with increased longevity, as has been seen in humans. Our IRB-approved protocol to look for functional variants of the Klotho gene among participants in the Baltimore Longitudinal Study on Aging was expanded this year to include the InChianti population as well. Over the past year we have genotyped the entire BLSA and InChianti populations for the KL-VS allele. In the coming year we will be looking for new variants in the Klotho gene among this Italian population. Data analysis will involve a search for correlations between specific allelic variants and phenotypes examined in the BLSA and InChianti studies. An abstract describing the initial analysis of atherosclerosis and Klotho allele status in the BLSA population was sent to the American Society of Human Genetics for presentation at the 2003 meeting in October: Search for association with Klotho allele variation and atherosclerosis in the Baltimore Longitudinal Study on Aging. A. Bektas, D. Taub, S. Najjar, D. Muller, L. Ferrucci, C. A. Francomano.