Functional analyses of SH2B1 mutations with relevance for body weight regulation

体重变异的遗传力很高。全基因组关联研究确定了98个与体重调节相关的基因组区域(Speliotes等人。2010年，Bradfield等人。2012年，Berndt等人。2012年)。作为世界范围内的第一个小组，我们在705名肥胖三人组中进行了一项GWAS，其中包括一名双亲都有亲生父母的极端肥胖指数患者(Scherag等人，2010年)。在这些家庭中，我们观察到SH2B1(Src-Homology 2B Adaptor Protein 1基因)基因座的肥胖风险等位基因过度传播给极度肥胖的儿童。SH2B1基因是肥胖的可靠候选基因。大规模的GWAS研究描述了该基因附近(Rs7359397)或编码区(rs7498665，Thr484Ala)的标记(例如Speliotes等人)。NAT Genet 2010)。动物基因敲除模型显示了与人类体重调节的相关性，因为小鼠模型是肥胖、高血压性、高脂血症、瘦素和胰岛素抵抗、高血糖和糖耐量减低。在极度肥胖的儿童和青少年的SH2B1编码区的突变筛查中，我们检测到导致该基因的两个剪接变体(betaThr656Ile/GammaPro674Ser)的氨基酸交换的突变。在11,406例超重和肥胖者中只有3人检测到这种罕见的突变，而在4,568名正常或体重不足的对照组中没有检测到这种罕见的突变。尽管在计算机分析中预测了该变体的潜在功能效应，但对瘦素信号的体外研究表明，与野生型SH2B1没有显著差异。与肥胖相关的常见多态rs7498665(Thr484Ala)对瘦素信号的功能也没有影响。这里我们将分析肥胖基因SH2B1中非同义变异的功能效应。在目前已知的变体中，选择了9个影响SH2B1不同功能区域的变体。这些SH2B1变体将被分析它们对瘦素和胰岛素受体信号的影响。这两条通路是SH2B1增强信号转导的能量动态平衡的主要调节者。此外，我们还将分析这些变异对SH2B1蛋白表达的影响。

Heritability for the variance of body weight is high. Genome-wide association studies (GWAS) identified 98 genomic regions that are relevant for weight regulation (Speliotes et al. 2010, Bradfield et al. 2012, Berndt et al. 2012). As the first group world-wide we conducted a GWAS in 705 obesity trios comprising an extremely obese index patient with both biological parents (Scherag et al., 2010). In these families, we observed over-transmission of the obesity risk allele at the SH2B1 (Src-homology 2B adaptor protein 1 gene) locus to extremely obese children. SH2B1 is a solid candidate gene for obesity. Large scale GWAS studies depicted markers in the vicinity (rs7359397) or coding region (rs7498665, Thr484Ala) of the gene (e.g. Speliotes et al. Nat Genet 2010). Animal knockout models showed a relevance for human body weight regulation, as the murine model is obese, hyperphagic, hyperlipidemic, leptin and insulin resistant, hyperglycaemic, and glucose intolerant. In a mutation screen of the coding region of SH2B1 in extremely obese children and adolescents that contributed to the intial transmission disequilibrium, we detected a mutation that leads to amino acid exchanges in two splice variants of the gene (betaThr656Ile/gammaPro674Ser). This rare mutation was detected only in three individuals among 11,406 overweight and obese cases but not in 4,568 normal or underweight controls. Although in silico analyses predicted a potential functional effect of this variant, in vitro studies of leptin signaling showed no significant difference to the wildtype variant of SH2B1. The common polymorphism rs7498665 (Thr484Ala) which is association to obesity showed also no functional influence on leptin signaling.Here we will analyze the functional effect of non-synonymous variants in the obesity gene SH2B1. Of the currently known variants nine were chosen that affect different functional domains of SH2B1.These SH2B1 variants will be analyzed for their impact on leptin- and insulin receptor signalling. These two pathways are the main regulators of energy homeostasis in which SH2B1 enhances signaling. In addition, we will analyze the impact of the variants on SH2B1 protein expression.