目的:GLIS3编码一个参与胰岛β细胞发育和功能的转录因子。罕见的致病性,GLIS3中的双等位基因突变导致综合征性新生儿糖尿病,而在该基因座上频繁的SNP与常见的2型糖尿病风险相关。因为稀有,位于2型糖尿病其他易感基因中的功能变异已经被证明会大大增加常见2型糖尿病的个体风险。我们旨在研究罕见致病性GLIS3变异体对2型糖尿病的影响.
方法:对来自糖尿病和肥胖(RaDiO)研究的罕见变异的5471名个体进行了GLIS3测序。根据美国医学遗传学和基因组学学院(ACMG)建立的标准评估变异的致病性。为了解决致病性强标准3(PS3),我们使用荧光素酶测定法对这些变体进行了功能研究,关注GLIS家族锌指3(GLIS3)结合并激活INS启动子的能力。然后评估了罕见致病性或可能致病性(P/LP)变异与2型糖尿病风险(和其他代谢特征)之间的关联。结合来自RaDiO的关联结果的荟萃分析,最终进行了52K研究(43,125例)和TOPMed研究(44,083例).
结果:通过对GLIS3的靶向重测序,我们鉴定出了来自RaDiO的395名参与者携带的105种罕见变异。其中,49个变体降低了INS启动子的激活。按照ACMG标准,18个罕见的变异被归类为P/LP,与其余外显子相比,最后两个外显子富集(p<5×10-6;OR>3.5)。在2型糖尿病患者中,这些P/LP变异的负担明显更高(p=3.0×10-3;OR3.9[95%CI1.4,12]),而肥胖,2型糖尿病变异携带者和非2型糖尿病携带者的诊断年龄和胆固醇水平相似.有趣的是,所有2型糖尿病携带者均对口服磺脲类药物敏感.在52K和TOPMed研究中鉴定了总共7种P/LP变体。从RaDiO获得的关联研究的荟萃分析,52K和TOPMed显示2型糖尿病个体中P/LPGLIS3变异的富集(p=5.6×10-5;OR2.1[95%CI1.4,2.9])。
结论:罕见的P/LPGLIS3变异确实有助于2型糖尿病的风险。位于蛋白质远端部分的变体可以通过影响其反式激活结构域对其功能活性产生直接影响,通过与小鼠GLIS3蛋白的同源性。此外,罕见的P/LPGLIS3变异似乎对β细胞功能有直接的临床作用,这可以通过使用磺酰脲类增加胰岛素分泌来改善。
OBJECTIVE: GLIS3 encodes a transcription factor involved in pancreatic beta cell development and function. Rare pathogenic, bi-allelic mutations in GLIS3 cause syndromic neonatal diabetes whereas frequent SNPs at this locus associate with common type 2 diabetes risk. Because rare, functional variants located in other susceptibility genes for type 2 diabetes have already been shown to strongly increase individual risk for common type 2 diabetes, we aimed to investigate the contribution of rare pathogenic GLIS3 variants to type 2 diabetes.
METHODS: GLIS3 was sequenced in 5471 individuals from the Rare Variants Involved in Diabetes and Obesity (RaDiO) study. Variant pathogenicity was assessed following the criteria established by the American College of Medical Genetics and Genomics (ACMG). To address the pathogenic strong criterion number 3 (PS3), we conducted functional investigations of these variants using luciferase assays, focusing on capacity of GLIS family zinc finger 3 (GLIS3) to bind to and activate the INS promoter. The association between rare pathogenic or likely pathogenic (P/LP) variants and type 2 diabetes risk (and other metabolic traits) was then evaluated. A meta-analysis combining association results from RaDiO, the 52K study (43,125 individuals) and the TOPMed study (44,083 individuals) was finally performed.
RESULTS: Through targeted resequencing of GLIS3, we identified 105 rare variants that were carried by 395 participants from RaDiO. Among them, 49 variants decreased the activation of the INS promoter. Following ACMG criteria, 18 rare variants were classified as P/LP, showing an enrichment in the last two exons compared with the remaining exons (p<5×10-6; OR>3.5). The burden of these P/LP variants was strongly higher in individuals with type 2 diabetes (p=3.0×10-3; OR 3.9 [95% CI 1.4, 12]), whereas adiposity, age at type 2 diabetes diagnosis and cholesterol levels were similar between variant carriers and non-carriers with type 2 diabetes. Interestingly, all carriers with type 2 diabetes were sensitive to oral sulfonylureas. A total of 7 P/LP variants were identified in both 52K and TOPMed studies. The meta-analysis of association studies obtained from RaDiO, 52K and TOPMed showed an enrichment of P/LP GLIS3 variants in individuals with type 2 diabetes (p=5.6×10-5; OR 2.1 [95% CI 1.4, 2.9]).
CONCLUSIONS: Rare P/LP GLIS3 variants do contribute to type 2 diabetes risk. The variants located in the distal part of the protein could have a direct effect on its functional activity by impacting its transactivation domain, by homology with the mouse GLIS3 protein. Furthermore, rare P/LP GLIS3 variants seem to have a direct clinical effect on beta cell function, which could be improved by increasing insulin secretion via the use of sulfonylureas.