School of Life Sciences, Arizona State University, Tempe, AZ, USA.
Chemical Engineering, School for Engineering, Matter, Transport and Energy, Arizona State University, ECG301-501 Tyler Mall, Tempe, AZ, 85281-6106, USA.
BMC Neurosci. 2020 Sep 4;21(1):36. doi: 10.1186/s12868-020-00586-0.
Frontotemporal dementia (FTD) is the second leading cause of early onset dementia following Alzheimer's disease. It involves atrophy of the frontal and temporal regions of the brain affecting language, memory, and behavior. Transactive response DNA-binding protein 43 (TDP-43) pathology is found in most FTD and ALS cases. It plays a role in transcription, translation and serves as a shuttle between the nucleus and cytoplasm. Prior to its aggregation, TDP-43 exists as polyubiquitinated, hyperphosphorylated C-terminal fragments that correlate well with FTD disease progression. Because of the importance of TDP-43 in these diseases, reagents that can selectively recognize specific toxic TDP variants associated with onset and progression of FTD can be effective diagnostic and therapeutic tools.
We utilized a novel atomic force microscopy (AFM) based biopanning protocol to isolate single chain variable fragments (scFvs) from a phage display library that selectively bind TDP variants present in human FTD but not cognitively normal age matched brain tissue. We then used the scFvs (FTD-TDP1 through 5) to probe post-mortem brain tissue and sera samples for the presence of FTD related TDP variants. The scFvs readily selected the FTD tissue and sera samples over age matched controls. The scFvs were used in immunohistochemical analysis of FTD and control brain slices where the reagents showed strong staining with TDP in FTD brain tissue slice. FTD-TDP1, FTD-TDP2, FTD-TDP4 and FTD-TDP5 all protected neuronal cells against FTD TDP induced toxicity suggesting potential therapeutic value.
These results show existence of different disease specific TDP variants in FTD individuals. We have identified a panel of scFvs capable of recognizing these disease specific TDP variants in postmortem FTD tissue and sera samples over age matched controls and can thus serve as a biomarker tool.
额颞叶痴呆（FTD）是继阿尔茨海默病之后导致早发性痴呆的第二大原因。它涉及大脑额颞叶的萎缩，影响语言、记忆和行为。大多数 FTD 和肌萎缩侧索硬化症（ALS）病例中都发现了 TDP-43 蛋白病理。它在转录、翻译中发挥作用，并作为核质和细胞质之间的穿梭蛋白。在其聚集之前，TDP-43 以多聚泛素化、过度磷酸化的 C 端片段形式存在，与 FTD 疾病进展密切相关。由于 TDP-43 在这些疾病中的重要性，能够选择性识别与 FTD 发病和进展相关的特定毒性 TDP 变体的试剂，可以成为有效的诊断和治疗工具。
我们利用一种新型原子力显微镜（AFM）基于生物淘选的方案，从噬菌体展示文库中分离出单链可变片段（scFvs），这些 scFvs 选择性地结合存在于人类 FTD 但不存在于认知正常的年龄匹配脑组织中的 TDP 变体。然后，我们使用这些 scFvs（FTD-TDP1 到 5）来探测死后脑组织和血清样本中是否存在与 FTD 相关的 TDP 变体。scFvs 很容易从年龄匹配的对照中选择出 FTD 组织和血清样本。scFvs 被用于 FTD 和对照脑切片的免疫组织化学分析，其中试剂在 FTD 脑组织切片中显示出与 TDP 强烈的染色。FTD-TDP1、FTD-TDP2、FTD-TDP4 和 FTD-TDP5 都能保护神经元细胞免受 FTD TDP 诱导的毒性，表明具有潜在的治疗价值。
这些结果表明，FTD 个体中存在不同的疾病特异性 TDP 变体。我们已经鉴定出一组 scFvs，能够在死后 FTD 组织和血清样本中识别出这些疾病特异性的 TDP 变体，并且可以作为生物标志物工具。
