Department of Laboratory Animal Medicine, Research Institute, National Center for Global Health and Medicine (NCGM), Shinjuku, Tokyo, Japan.
Laboratory of Laboratory Animal Science and Medicine, School of Veterinary Medicine, Kitasato University, Towada, Aomori, Japan.
PLoS One. 2020 Jun 5;15(6):e0234132. doi: 10.1371/journal.pone.0234132. eCollection 2020.
Diabetic animal models have made significant contributions to understanding the etiology of diabetes and to the development of new medications. Our research group recently developed a novel diabetic mouse strain, the insulin hyposecretion (ihs)mouse. The strain involves neither obesity nor insulitis but exhibits notable pancreatic β-cell dysfunction, distinguishing it from other well-characterized animal models. In ihs mice, severe impairment of insulin secretion from pancreas has been elicited by glucose or potassium chloride stimulation. To clarify the genetic basis of impaired insulin secretion, beginning with identifying the causative gene, genetic linkage analysis was performed using [(C57BL/6 × ihs) F1 × ihs] backcross progeny. Genetic linkage analysis and quantitative trait loci analysis for blood glucose after oral glucose loading indicated that a recessively acting locus responsible for impaired glucose tolerance was mapped to a 14.9-Mb region of chromosome 18 between D18Mit233 and D18Mit235 (the ihs locus). To confirm the gene responsible for the ihs locus, a congenic strain harboring the ihs locus on the C57BL/6 genetic background was developed. Phenotypic analysis of B6.ihs-(D18Mit233-D18Mit235) mice showed significant glucose tolerance impairment and markedly lower plasma insulin levels during an oral glucose tolerance test. Whole-genome sequencing and Sanger sequencing analyses on the ihs genome detected two ihs-specific variants changing amino acids within the ihs locus; both variants in Slc25a46 and Tcerg1 were predicted to disrupt the protein function. Based on information regarding gene functions involving diabetes mellitus and insulin secretion, reverse-transcription quantitative polymerase chain reaction analysis revealed that the relative abundance of Reep2 and Sil1 transcripts from ihs islets was significantly decreased whereas that of Syt4 transcripts were significantly increased compared with those of control C57BL/6 mice. Thus, Slc25a46, Tcerg1, Syt4, Reep2 and Sil1 are potential candidate genes for the ihs locus. This will be the focus of future studies in both mice and humans.
糖尿病动物模型在理解糖尿病的病因和开发新药物方面做出了重大贡献。我们的研究小组最近开发了一种新型糖尿病小鼠品系，即胰岛素分泌不足（ihs）小鼠。该品系既不肥胖也没有胰岛炎，但表现出明显的胰腺β细胞功能障碍，与其他特征明确的动物模型不同。在 ihs 小鼠中，葡萄糖或氯化钾刺激会引起胰腺胰岛素分泌严重受损。为了阐明胰岛素分泌受损的遗传基础，我们从确定致病基因开始，使用[(C57BL/6 × ihs) F1 × ihs]回交后代进行遗传连锁分析。遗传连锁分析和口服葡萄糖负荷后血糖的数量性状位点分析表明，一个负责葡萄糖耐量受损的隐性作用位点被定位到 18 号染色体上 D18Mit233 和 D18Mit235 之间的 14.9-Mb 区域（ihs 位点）。为了确认负责 ihs 位点的基因，我们开发了携带 C57BL/6 遗传背景上 ihs 位点的同基因品系。B6.ihs-(D18Mit233-D18Mit235) 小鼠的表型分析显示，口服葡萄糖耐量试验中葡萄糖耐量显著受损，血浆胰岛素水平明显降低。在 ihs 基因组上进行全基因组测序和 Sanger 测序分析检测到两个 ihs 特异性变异，改变了 ihs 位点内的氨基酸；Slc25a46 和 Tcerg1 中的两个变异都被预测会破坏蛋白质功能。基于涉及糖尿病和胰岛素分泌的基因功能信息，逆转录定量聚合酶链反应分析显示，与对照 C57BL/6 小鼠相比，ihs 胰岛中的 Reep2 和 Sil1 转录物的相对丰度显著降低，而 Syt4 转录物的相对丰度显著增加。因此，Slc25a46、Tcerg1、Syt4、Reep2 和 Sil1 是 ihs 位点的潜在候选基因。这将是未来在小鼠和人类中进行研究的重点。
