Center for Alzheimer's and Related Dementias: Detection of cryptic exons (splicing differences) in TDP-43 as biomarkers for frontotemporal dementia and Alzheimer's disease

National Institute On Aging

Investigators

Abstract

Since 2022, we have obtained more than 200 samples of human CSF from patients with ALS, progressive supranuclear palsy (PSP), and control cases to determine if TDP-43 cryptic exons are present in diseased but not control patients. Our efforts using patient CSF have been critical in confirming and expanding on our findings in iPSC neurons. We detected 65 candidate cryptic exons and performed two-dimensional targeted mass spectrometry to identify lead cryptic peptide candidates (Seddighi et al., 2024). The data from this publication is available to the scientific community through the Alzheimer’s Disease Workbench (ADWB). We are now attempting to utilize the cryptic peptides and cryptic exons identified in this study to develop peptide and RNA-based biomarkers and ultra-sensitive bioassays for clinical application. We are currently working with industry partner BioMarin, Dr. Pietro Fratta from University College London, and Dr. David Walt from Harvard University to further investigate the creation of biomarkers. We developed preclinical assay for the top candidate biomarker, HDGFL2, using mass spectrometry-based proteomics and ultra sensitive immunoassay. The major milestones have achieved including:1)Successfully identified and characterized cryptic exons in TDP-43 knockdown iPSCs, with subsequent confirmation in human CSF and plasma samples; 2) Identified primary cryptic exon candidates suitable for biomarker and antibody development. These candidates have been validated through multiple experimental approaches and represent the most promising targets for clinical translation; 3) Developed comprehensive recombinant protein production strategies and biomarker development protocols from lead cryptic peptide candidates; 4) Successfully developed both polyclonal and monoclonal antibodies targeting lead cryptic peptide candidates; 5) Established clinical bioassay protocols for ALS/FTD early detection. We have published two manuscripts on this project: Brown, Anna-Leigh, et al. "TDP-43 loss and ALS-risk SNPs drive mis-splicing and depletion of UNC13A." Nature 603.7899 (2022): 131-137. https://doi.org/10.1038/s41586-022-04436-3 PubMed ID 35197628 PubMed Central ID PMC8891020 Sahba Seddighi et al. “Mis-spliced transcripts generate de novo proteins in TDP-43–related ALS/FTD.” Science Translational Medicine 16,eadg7162 (2024). https://doi.org/10.1126/scitranslmed.adg7162 PMID 38277467 PubMed Central ID