Defining the role of MafA in islet beta cells

我们对胰岛生理学的了解大多来自啮齿动物的研究。然而，我们现在知道， 啮齿动物和人类胰岛之间在（例如）结构，激素分泌， 和胰岛细胞转录因子（TF）的表达，证明了假设啮齿动物 模型完全模拟人类胰岛生理学和疾病。这种差异的一个例子是胰岛β 细胞富集MAFA TF，一种对出生后啮齿类动物的这些细胞至关重要的蛋白质。因此，MAFA 在人类胰岛β细胞中几乎检测不到一种蛋白质，直到9岁，而这种TF首先被检测到， 在啮齿动物胰岛素+细胞的整个生命周期中产生。我们认为人类 至少有两个出生后的、年龄依赖性的产生MAFA的β细胞群，能够维持 正常：幼年β细胞（即<~9岁），几乎没有MAFA（即MAFA低），幼年后β细胞， 鲁棒MAFA（MAFAHigh）。事实上，独立的研究已经建立了不同的分子和功能 这些人类细胞群的特性。在这里，我们将研究MAFA对人类β细胞的影响， 假设这种TF在调节成人胰岛素分泌中起重要作用。我们在第一次分析中 目的将使用从人胚胎干细胞（hESC）产生的β样细胞和诱导的β样细胞来进行。 多能干细胞（iPSC）（统称为人多能干细胞或hPSC）。这里我们将 确定MAFA的敲除和过表达如何影响β细胞的成熟和功能， 它们大大改善的葡萄糖刺激胰岛素分泌特性平行增强MAFA表达， 移植到免疫功能低下的NSG小鼠后。此外，我们将研究致病性 MAFA的变体（丝氨酸（S）64->苯丙氨酸（F））显著增加其蛋白质稳定性， β细胞活性。值得注意的是，MAFAS 64 F使受试者易患成人型糖尿病或胰岛素瘤病（即， 非综合征型胰岛素分泌β细胞肿瘤）。我们做了一个老鼠模型 在内源性MafA基因中携带这种突变，我们的结果显示男性葡萄糖耐受不良， 改善女性的葡萄糖清除率，模拟人类受试者的发现。值得注意的是， 雄性小鼠与过早的细胞老化和衰老有关。最近，独立报道称， 将病理性衰老β细胞群与1型糖尿病和2型糖尿病胰岛功能障碍联系起来。我们 第二个目的的实验将确定MAFAS 64 F在人类中的分子和功能结果。 β细胞。我们对人类胰岛细胞的整体关注被视为创新，以及人类胰岛细胞的组合使用。 干细胞衍生的β样细胞和人胰岛，用于获得新的生理学相关的机制见解。

Much of our knowledge of islet physiology stems from rodent studies. However, we now know that marked discrepancies exist between rodent and human islets in regard to (for example) architecture, hormone secretion, and islet cell transcription factor (TF) expression, demonstrating potential limitations in assuming that rodent models entirely mimic human islet physiology and disease. An example of such a discrepancy lies in the islet β cell enriched MAFA TF, a fundamentally important protein to these cells in postnatal rodents. Thus, the MAFA protein is barely detectable in human islet β cells until ~9 years of age, whereas this TF is first detected developmentally and then produced throughout the lifespan of rodent insulin+ cells. We propose that humans have at least two postnatal, age-dependent MAFA-producing β cell populations capable of maintaining euglycemia: juvenile β cells (i.e. <~9 years old) with little MAFA (i.e. MAFALow) and post-juvenile β cells with robust MAFA (MAFAHigh). In fact, independent studies have established distinct molecular and functional properties of these human cell populations. Here we will examine the impact of MAFA on human β cells and hypothesize that this TF plays an essential role in regulating insulin secretion in adults. Our analysis in the first aim will be conducted using the β-like cells produced from both human embryonic stem cells (hESC) and induced pluripotent stem cells (iPSC) (collectively termed human pluripotent stem cells, or hPSCs). Here we will determine how knockout and over-expression of MAFA influences β cell maturation and function, appreciating that their greatly improved glucose-stimulated insulin secretion properties parallel enhanced MAFA expression after transplantation into immunocompromised NSG mice. In addition, we will investigate how a pathogenic variant of MAFA (Serine (S) 64 -> Phenylalanine (F)) that prominently increases its protein stability affects human β cell activity. Notably, MAFAS64F predisposes subjects to either adult-onset diabetes or insulinomatosis (i.e. non-syndromic insulin-producing β cell tumors) in a gender-biased manner. We generated a mouse model harboring this mutation in the endogenous MafA gene, and our results show glucose intolerance in males and improved glucose clearance in females, mimicking the findings in human subjects. Significantly, dysfunction in male mice was associated with premature cellular aging and senescence. Recently, independent reports have linked pathologic, senescent β cell populations to type 1 diabetes and type 2 diabetes islet dysfunction. Our experimentation in the second aim will define the molecular and functional consequences of MAFAS64F in human β cells. Our overall focus on human islet cells is viewed as innovative, as well as the combined use of human stem cell derived β-like cells and human islets for obtaining novel, physiologically relevant mechanistic insights.