Antisense Oligonucleotides for Targeting Nonsense-mediated mRNA Decay in Frontotemporal Dementia

项目摘要 颗粒蛋白前体是一种溶酶体分泌蛋白，含有多个富含半胱氨酸的颗粒蛋白结构域;其 精确的分子功能仍然未知。颗粒蛋白前体（GRN）突变是额颞叶 痴呆症（FTD），这是一种毁灭性的疾病，从诊断开始平均存活3.8年，无法治愈 目前可用。由于前颗粒蛋白缺陷型FTD是一种单倍体功能不全的疾病，因此， 增加颗粒蛋白前体水平是可行的治疗方法。我们最近培育了一只基因敲入小鼠 携带常见患者无义突变GRNR 493 X的FTD模型，我们确定， 无义介导的mRNA衰变（NMD）途径导致突变颗粒蛋白前体显著减少 该小鼠模型中的mRNA水平，以及含有GRNR 493 X突变的患者来源的成纤维细胞中的mRNA水平。 此外，我们基于细胞的研究表明，颗粒蛋白前体R493 X突变蛋白是功能性的， 在前颗粒蛋白缺乏的细胞中表达。基于这些结果，我们假设抑制NMD介导的 突变体GrnR 493 X mRNA的降解将增加功能性颗粒蛋白前体水平，从而改善 FTD相关的行为变化和神经病理学。我们将在下面的两个例子中检验这个假设。 具体目的：目的1）在GrnR 493 X中测试阻断NMD介导的降解的ASO的体内功效 FTD敲入小鼠模型，目的2）设计并检测靶向NMD介导的FTD降解的ASO 人GRNR 493 X mRNA。这些研究的完成将产生重要的临床前数据， 深入了解基于ASO的NMD抑制作为前粒蛋白缺陷FTD治疗方法的效用。

Project Summary Progranulin is a lysosomal and secreted protein that contains multiple cysteine-rich granulin domains; its precise molecular function remains unknown. Progranulin (GRN) mutations are causal for frontotemporal dementia (FTD), which is a devastating disease with a mean survival of 3.8 years from diagnosis and no cure currently available. Since progranulin-deficient FTD is a disease of haploinsufficiency, strategies aimed at increasing progranulin levels are feasible therapeutic approaches. We recently generated a knock-in mouse model of FTD harboring the common patient nonsense mutation GRNR493X, and we established that the nonsense-mediated mRNA decay (NMD) pathway contributes to the markedly reduced mutant progranulin mRNA levels in this mouse model, as wel`l as in patient-derived fibroblasts containing the GRNR493X mutation. Moreover, our cell-based studies indicate that the progranulin R493X mutant protein is functional when re- expressed in progranulin-deficient cells. Based on these results, we hypothesize that inhibiting NMD-mediated degradation of the mutant GrnR493X mRNA would increase functional progranulin levels and thereby improve FTD-associated behavioral changes and neuropathology. We will test this hypothesis in the following two specific aims: Aim 1) Test in vivo efficacy of ASOs that block NMD-mediated degradation in the GrnR493X knock-in mouse model of FTD, and Aim 2) Design and test ASOs that target NMD-mediated degradation of the human GRNR493X mRNA. Completion of these studies will generate important preclinical data that provide insights into the utility of ASO-based NMD inhibition as a therapeutic approach for progranulin-deficient FTD.