Isolation and characterization of antibody fragments selective for human FTD brain derived TDP-43 variants
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BMC Neuroscience Open Access
RESEARCH ARTICLE
Isolation and characterization of antibody fragments selective for human FTD brain derived TDP‑43 variants Lalitha Venkataraman1, Ping He2, Galam Khan3, Brent T. Harris3,4 and Michael R. Sierks2*
Abstract Background: 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. Results: 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. Conclusions: 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. Keywords: Frontotemporal dementia, TDP-43 variants, scFv, Biomarker, Brain tissue, Sera Background Frontotemporal dementia (FTD) is the second leading cause of early onset dementia following Alzheimer’s disease [1]. FTD is diverse and involves atrophy of the *Correspondence: [email protected] 2 Chemical Engineering, School for Engineering, Matter, Transport and Energy, Arizona State University, ECG301‑501 Tyler Mall, Tempe, AZ 85281‑6106, USA Full list of author information is available at the end of the article
frontal and temporal regions of the brain affecting language, memory and personality [2]. Based on prominent pathological protein inclusions of TDP-43, tau or Fused in Sarcoma (FUS), FTD is classified as either FTD-TDP, FTD-tau or FTD-FUS [3]. Studies have shown that these subtypes have overlapping molecular pathology, making diagnosis difficult [4–6], despite progre
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