Karachanak-Yankova, S. | bioRxiv Science

bioRxiv2024

Changes in the Public IgM Repertoire and its Idiotypic Connectivity in Alzheimer's Disease and Frontotemporal Dementia

Alzheimers disease (AD) and frontotemporal dementia (FTD) are prevalent neurodegenerative disorders. Early diagnosis is challenging due to the lack of definitive biomarkers and reliance on invasive procedures. Immune biomarkers, particularly those reflecting the interaction between the central nervous system (CNS) and the peripheral immune system, have shown promise for non-invasive detection through blood samples. This study investigates the reactivity of serum IgM and IgG from AD and FTD patients against a library of mimotopes representing public IgM reactivities in healthy donors. Serum samples from AD, FTD, and other neurodegenerative dementias (ND) and controls were tested on peptide microarrays. The samples were pooled to mitigate individual variability. The reactivity data were analyzed using graphs to represent the cross-reactivity networks. The analysis revealed distinct reactivity patterns for the studied groups. Public IgM reactivities showed significant correlations with neurodegenerative conditions, with AD and FTD exhibiting loss or gain of specific IgM reactivities. Graph analysis highlighted significant differences between disease and control groups in graph density, clustering, and assortativity parameters. Mimotopes of IgM reactivities lost in dementia, particularly in AD, exhibited significant homology to HCDR3 sequences of human antibodies. Furthermore, clusters of reactivities showed significant distinctions between AD and FTD, with IgG reactivities providing additional differentiation. Several self-proteins related to neurodegeneration proved to have sequences homologous to disease-associated mimotopes. Interestingly, the beta-propeller signature sequence YWTD found in ApoEs receptor LRP1 proved a characteristic epitope for IgG in FTD but not AD. At the same time, the respective public |gM mimotope YWTDSSR coincides with a highly conserved sequence in many microorganisms and sequences found in human HCDR3. Thus, the public IgM repertoire, characterized by its broad reactivity and inherent autoreactivity, offers valuable insights into the immunological alterations in neurodegenerative diseases. The study supports the potential of IgM and IgG reactivity profiles as another compartment of non-invasive biomarkers for early diagnosis and differentiating AD and FTD.

immunology↗

bioRxiv2020

Ancient mitochondrial DNA pathogenic variants putatively associated with mitochondrial disease

Mitochondrial DNA variants associated with diseases are widely studied in contemporary populations, but their prevalence has not yet been investigated in ancient populations. The publicly available AmtDB database contains 1443 ancient mtDNA Eurasian genomes from different periods. The objective of this study was to use this data to establish the presence of pathogenic mtDNA variants putatively associated with mitochondrial diseases in ancient populations. The clinical significance, pathogenicity prediction and contemporary frequency of mtDNA variants were determined using online platforms. The analyzed ancient mtDNAs contain six variants designated as being "confirmed pathogenic" in modern patients. The oldest of these, m.7510T>C in the MT-TS1 gene, was found in a sample from the Neolithic period dated 5800-5400 BCE. All six have well established clinical association, and their pathogenic effect is corroborated by very low population frequencies in contemporary populations. In addition, ten variants designated as possibly or likely pathogenic were detected. The oldest of these were two variants in the MT-TD gene, m.7543A>G and m.7554G>A, from Neolithic samples dated 8205-7700 BCE. A novel mutation in contemporary populations, m.4440G>A in the MT-TM gene, is established in 12 ancient mtDNA samples from different periods ranging from 2800 BCE to 920 CE. The pathogenic effect of these possibly/likely pathogenic mutations is not yet well established, and further research is warranted. All detected mutations putatively associated with mitochondrial disease in ancient mtDNA samples are in tRNA coding genes. Most of these mutations are in a mt-tRNA type (Model 2) that is characterized by loss of D-loop/T-loop interaction. Seven mutations are located in CS-Anticodon stem, 4 are located in AS-Acceptor stem, 2 in TS-T{Psi}C stem, and single mutations are found in DL-Dihydrouridine Loop, CL-Anticodon Loop and DS-Dihydrouridine stem. Exposing pathogenic variants in ancient human populations expands our understanding of their origin.

genetics↗