Abstract：
Heterozygous loss-of-function mutations in the progranulin gene (GRN) are a major cause of frontotemporal dementia due to progranulin haploinsufficiency; complete deficiency of progranulin causes neuronal ceroid lipofuscinosis. Several progranulin-deficient mouse models have been generated, including both knockout mice and knockin mice harboring a common patient mutation (R493X). However, the GrnR493X mouse model has not been characterized completely. Additionally, while homozygous GrnR493X and Grn knockout mice have been extensively studied, data from heterozygous mice is still limited. Here, we performed more in-depth characterization of heterozygous and homozygous GrnR493X knockin mice, which includes biochemical assessments, behavioral studies, and analysis of fluid biomarkers. In the brains of homozygous GrnR493X mice, we found increased phosphorylated TDP-43 along with increased expression of lysosomal genes, markers of microgliosis and astrogliosis, pro-inflammatory cytokines, and complement factors. Heterozygous GrnR493X mice did not have increased TDP-43 phosphorylation but did exhibit limited increases in lysosomal and inflammatory gene expression. Behavioral studies found social and emotional deficits in GrnR493X mice that mirror those observed in Grn knockout mouse models, as well as impairment in memory and executive function. Overall, the GrnR493X knockin mouse model closely phenocopies Grn knockout models. Lastly, in contrast to homozygous knockin mice, heterozygous GrnR493X mice do not have elevated levels of fluid biomarkers previously identified in humans, including neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) in both plasma and CSF. These results may help to inform pre-clinical studies that use this Grn knockin mouse model and other Grn knockout models.
摘要：
颗粒蛋白前体基因（GRN）的杂合功能丧失突变是由于颗粒蛋白单倍体功能不全导致额颞叶痴呆的主要原因；颗粒蛋白完全缺乏会导致神经元类脂褐变。已经产生了几种缺乏颗粒蛋白的小鼠模型，包括基因敲除小鼠和具有常见患者突变的敲入小鼠（R493X）。然而,GrnR493X小鼠模型尚未完全表征。此外,而纯合GrnR493X和Grn基因敲除小鼠已被广泛研究，杂合小鼠的数据仍然有限。这里,我们对杂合和纯合GrnR493X敲入小鼠进行了更深入的表征，其中包括生化评估，行为研究,和流体生物标志物的分析。在纯合GrnR493X小鼠的大脑中，我们发现磷酸化的TDP-43随着溶酶体基因表达的增加，小胶质细胞增生和星形胶质细胞增生的标志物，促炎细胞因子，和补充因素。杂合GrnR493X小鼠不具有增加的TDP-43磷酸化,但表现出溶酶体和炎性基因表达的有限增加。行为研究发现，GrnR493X小鼠的社会和情感缺陷反映了在Grn基因敲除小鼠模型中观察到的缺陷，以及记忆和执行功能受损。总的来说,GrnR493X敲入小鼠模型接近表型Grn敲除模型。最后,与纯合敲入小鼠相反，杂合子GrnR493X小鼠没有先前在人类中鉴定的流体生物标志物水平升高，包括血浆和CSF中的神经丝轻链（NfL）和神经胶质纤维酸性蛋白（GFAP）。这些结果可能有助于告知使用该Grn敲入小鼠模型和其他Grn敲除模型的临床前研究。
