Immediate early response 3 interacting-protein 1 (IER3IP1) is an endoplasmic reticulum resident protein, highly expressed in pancreatic cells and the developing brain cortex. Homozygous mutations in IER3IP1 have been found in individuals with microcephaly and neonatal diabetes, yet the underlying mechanism causing beta cell failure remains unclear. Here, we utilized differentiation of genome edited-stem cells into pancreatic islet cells to elucidate the molecular basis of IER3IP1 neonatal diabetes. Using CRISPR-Cas9, we generated two distinct IER3IP1-mutant human embryonic stem cell lines: a homozygous knock-in model of a patient mutation (IER3IP1V21G), and a knockout model (IER3IP1-/-). While these mutant stem cell lines differentiated normally into definitive endoderm and pancreatic progenitors, we observed that IER3IP1-KO stem cell derived-islets (SC-islets) presented a significant decrease in beta cell numbers and elevated ER stress. Retention Using Selective Hooks (RUSH) assay revealed three-fold reduction in ER-to-Golgi trafficking of proinsulin in IER3IP1 mutant beta cells. Additionally, IER3IP1 mutant SC-islets implanted into immunocompromised mice displayed defective human insulin secretion, indicating the deleterious impact of IER3IP1 mutations on beta cell function. Our study provides valuable insights into the role of IER3IP1 in human beta cell biology and establishes a useful model to investigate ER-to-Golgi trafficking defects within beta cells.

中文翻译：

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IER3IP1 突变由于胰岛素原运输受损而导致新生儿糖尿病


速发型早期反应 3 相互作用蛋白 1 （IER3IP1） 是一种内质网驻留蛋白，在胰腺细胞和发育中的大脑皮层中高度表达。在小头畸形和新生儿糖尿病个体中发现了 IER3IP1 纯合突变，但导致 β 细胞衰竭的潜在机制仍不清楚。在这里，我们利用基因组编辑干细胞分化为胰岛细胞来阐明IER3IP1新生儿糖尿病的分子基础。使用 CRISPR-Cas9，我们生成了两种不同的IER3IP1突变人胚胎干细胞系：患者突变的纯合敲入模型 （IER3IP1V21G） 和敲除模型 （IER3IP1-/-）。虽然这些突变干细胞系正常分化为最终内胚层和胰腺祖细胞，但我们观察到 IER3IP1-KO 干细胞衍生胰岛 （SC-胰岛） 表现出 β 细胞数量的显着减少和 ER 应激升高。使用选择性钩子保留 （RUSH） 测定显示，IER3IP1突变型 β 细胞中胰岛素原的 ER 到高尔基体运输减少了 3 倍。此外，植入免疫功能低下小鼠的 IER3IP1 突变 SC 胰岛显示出人胰岛素分泌缺陷，表明 IER3IP1 突变对 β 细胞功能的有害影响。我们的研究为 IER3IP1 在人类 β 细胞生物学中的作用提供了有价值的见解，并建立了一个有用的模型来研究 β 细胞内的 ER 到高尔基体运输缺陷。