Identification of type 2 diabetes mellitus susceptibility candidate genes in loci detected by QTL analysis of diabetic db mice,

本研究在BKS、Cg-m+ /+ Lepr^与C3 H或DBA 2（D2）杂交的F_2群体中定位了影响2型糖尿病（T2 D）表型的4个主要数量性状基因座（QTL）<db>。为了确定T2 D的疾病易感基因，我们使用同源小鼠绘制了该区域。我们的研究结果如下：1）我们通过将供体（db）小鼠与携带给定的含有QTL的基因组区域的D2品系受体小鼠重复回交来产生同源小鼠，以测试每个QTL对糖尿病表型的影响。在4个QTL中，D2小鼠的两个区域的渐渗与携带BKS等位基因的对照小鼠存在显著差异。表型差异在体重、脂肪垫重量、空腹血糖浓度和胰岛素水平（A区）;体重、脂肪垫重量和总胆固醇水平（B区）中重复。2)为了便于精细定位，我们从BKS/D2同源区域中分别获得了16个（A区）和22个（B区）同源亚系。3)通过对一个同系小鼠的7个亚系的分析，确定了影响体重、脂肪垫重量的3个Mb区域在A区。对另一个同源系小鼠的5个亚系进行分析，发现B区存在影响体重和脂肪垫重量的8 Mb区域。然而，我们无法在A区绘制与空腹血糖浓度相关的区域。这些同源亚系为精细定位表型QTL区域提供了有力的工具。为了鉴定靶基因，我们的实验室正在进行亚同源小鼠和对照小鼠的各种组织中的mRNA和蛋白质表达分析。

We previously mapped four major quantitative trait loci (QTLs) for type 2 diabetes mellitus (T2D), which affect T2D phenotypes in F_2 populations generated from a BKS.Cg-m+ /+ Lepr^<db> and C3H or DBA2 (D2) intercross. To identify the disease-susceptibility genes of T2D, we mapped the region using congenic mice. Our findings are as follows ; 1) We generated congenic mice by repeated backcross of donor (db) mice to recipient mice of D2 strain carrying a given QTL-containing genome region to test the effect of each QTL on diabetic phenotypes. Out of four QTLs, introgression of two regions of D2 mice was significantly different from that of control mice carrying BKS alleles. Differences in phenotypes were replicated in body weight, fat pad weight, fasting BG concentrations, and insulin level (A region) ; body weight, fat pad weight, and total cholesterol level (B region). 2) We generated 16 (for A region) or 22 (for B region) congenic sub-lines derived from BKS/D2 congenic region for two QTLs to facilitate fine mapping. 3) Analyses of seven sub-lines in one congenic mouse identified the region of three Mb, which affects body weight, fat pad weight in A region. Analyses of five sub-lines in another congenic mouse revealed the region of eight Mb, which affects body weight and fat pad weight in B region. However, we could not map the region correlating fasting BG concentrations in A region. These congenic sub-lines offered a powerful tool for fine mapping phenotypes-assigned QTL region. To identify the target gene, mRNA and protein expression analyses in various tissues from subcongenic and control mice are under way in our laboratory.