Biology subjects

Hardy, J.

Publications and source records attributed to Hardy, J..

At least 19 recordsLinked to original sources

bioRxiv2026

An overlooked distal regulatory signal on a shared haplotype drives the neuroinflammatory cascade underlying GBA1-associated Parkinson's disease

BACKGROUNDThe persistent puzzle of how GBA1 coding variants underlying monogenic Gaucher disease confer such strong risk for polygenic Parkinsons disease (PD) remains unresolved. Here, we sought to resolve this long-standing paradox. METHODSUsing the Parkinsons Progression Markers Initiative resource, we integrated whole-genome sequencing from sporadic PD cases and controls with matched transcriptomic, epigenomic and cerebrospinal fluid proteomic data across Northern European and Ashkenazi Jewish populations. Ancestry-specific genetic maps enabled precise integration of disease localisation with eQTL, pQTL and chromatin architecture, linking genetic association to molecular mechanism, while evolutionary genetic analyses resolved the regional haplotypic architecture. RESULTSWe identified a PD-associated regulatory signal located 150 kilobases distal to GBA1 that robustly replicated across all molecular datasets and both ancestries. Integrative mapping identified rs77268551-G as the candidate regulatory variant, which we show resides on an extended haplotype also carrying the Gaucher disease-causing N370S allele. Evolutionary analyses reveal a clear signature of recent positive selection acting on the Gaucher disease-causing N370S allele, giving rise to this extended shared haplotype that likely concealed the underlying distal PD-associated regulatory signal. rs77268551-G resides within a neuronal enhancer with features consistent with super-enhancer activity that orchestrates hierarchical enhancer-to-enhancer-to-promoter interactions with eleven cis-target genes, including ADAR, IL6R and GBA1, driving a coordinated transcriptional programme. Proteomic profiling identified genotype-specific cerebrospinal fluid protein signatures, including PARK7, BIN1 and SAA1, consistent with a neuroinflammatory programme. CONCLUSIONSThe findings support a dual-hit model in which a distal regulatory element is the primary driver of PD-associated molecular programmes, while co-inherited GBA1 protein-coding variation on the same haplotype modifies and amplifies the risk established by the regulatory variant, giving rise to the clinically distinct GBA1-associated PD phenotype. Regulatory activation and GBA1-related functional effects converge on neuroinflammatory and lysosomal pathways, and the resulting molecular signatures suggest genotype-linked biomarkers with potential clinical relevance.

genetics↗

bioRxiv2026

GPNMB and glycosphingolipid measurements in cerebrospinal fluid and plasma from Parkinson's disease patients in the BioFind cohort

BackgroundParkinsons disease (PD) is a prevalent neurodegenerative disorder characterized by progressive motor dysfunction and broad cellular impairment, including significant disruptions in lysosomal function, lipid metabolism, and intracellular trafficking. Glycosphingolipids (GSLs), critical for various cellular processes, depend on effective lysosomal degradation. Aberrant GSL metabolism has been linked to PD pathology, and glycoprotein non-metastatic melanoma protein B (GPNMB) has emerged as a biomarker associated with lysosomal dysfunction and lipid imbalance in PD ObjectivesTo assess the relationship between GPNMB and GSL levels in cerebrospinal fluid (CSF) and plasma from PD patients and controls within the BioFIND cohort. We also investigated potential sex differences and associations with PD-related biomarkers such as -synuclein MethodsGSL species and GPNMB protein levels were quantified using high-performance liquid chromatography (HPLC) and ELISA assays, respectively, in matched CSF and plasma samples from PD patients and controls ResultsLevels of the paraglobosides GSL species, alpha-2,3SpG and pGb were significantly elevated in the plasma of PD patients compared to healthy controls, while levels of the ganglioside GD1a and the lacto-series GSL, Leb combined (GD1a + Leb), were significantly reduced in PD. GPNMB levels positively correlated with several GSL species in both plasma and CSF. Plasma GSLs and GPNMB concentrations were significantly higher in females compared to males, independent of PD diagnosis. CSF GPNMB correlated positively with age and -synuclein concentrations InterpretationOur findings confirm that GSL metabolism is altered in PD. They also highlight significant sex-based biochemical variations in GSL and GPNMB levels, emphasizing the need for sex-specific analyses in PD biomarker research. The relationship between GSLs and GPNMB supports their potential as interconnected biomarkers of lipid pathology in PD.

neuroscience↗

bioRxiv2026

Divergent consequences of PSEN1 knockout and PSEN2 knockout in stem cell derived models of the brain

{gamma}-secretase is a multi-subunit enzyme complex responsible for cleaving hundreds of substrates in diverse cellular contexts. Variation in subunit composition - including the use of alternate catalytic subunits Presenilin 1 (PSEN1) and Presenilin 2 (PSEN2) - results in diverse {gamma}-secretase complexes. Point mutations in PSEN1 and PSEN2 cause familial forms of Alzheimers disease, while loss-of-function mutations in the {gamma}-secretase subunits PSEN1, PSENEN and NCSTN cause acne inversa. To advance therapeutic strategies targeting {gamma}-secretase in Alzheimers disease, a better understanding of individual {gamma}-secretase complexes is required. In this study, we used CRISPR-Cas9 genome engineering to generate PSEN2-knockout iPSCs in order to compare the consequence of PSEN2 knockout versus PSEN1 knockout in iPSC-derived brain cells. In contrast to PSEN1-knockout, PSEN2-knockout did not alter APP cleavage or A{beta} generation in iPSC-neurons, nor did it disrupt Nicastrin maturation. Similarly, PSEN2-knockout had little impact on TREM2 processing in iPSC-microglia. Instead, our data indicate that loss of PSEN2 primarily impacts the endo-lysosomal system in iPSC-neurons, causing an accumulation of early endosome markers and a reduction in lysosomal markers - phenotypes not observed in PSEN1-knockout neurons. Taken together, these findings highlight distinct and non-redundant functions of PSEN1 and PSEN2 in human brain cells, reinforcing findings in animal models and subcellular localisation studies. This work advances our understanding of distinct {gamma}-secretase complex functions and provides insights that will support future therapeutic efforts to inhibit, modulate or stabilise {gamma}-secretase.

neuroscience↗

bioRxiv2025

Honey Bee Queen Susceptibility to Viral Infection Varies Across Developmental Stages in Queen Rearing Operations

Viruses are a large class of honey bee pathogens that negatively affect colony health, yet their prevalence and transmission dynamics in commercial queen production operations remain poorly understood. To address this gap, we conducted a series of controlled queen monitoring experiments and surveys to understand the prevalence and viral loads of seven viruses across developmental stages of queens, drones, royal jelly, and workers from associated colonies. All viruses except SBV were detected, with BQCV, DWV-B, and LSVs showing consistently high prevalence. Eggs were frequently infected with LSVs, DWV-B, and CBPV, suggesting vertical virus transmission, and highlighting the importance of selecting healthy breeder queens. BQCV, on the other hand, dominated in queen larvae, pupae, and adult stages. Mated queens, particularly those maintained in bank colonies, exhibited higher prevalence and viral loads than virgin queens, with DWV-B and BQCV being most abundant. Worker bees from bank colonies also showed slightly higher viral loads compared to other colonies, indicating potential risks associated with queen banking. Drone samples revealed high BQCV and DWV-B prevalence, indicative of their potential role in venereal transmission. The results from hierarchical clustering and correlation analyses provided evidence that viral profiles of queens did not necessarily match those of their resident colonies, highlighting complex viral transmission dynamics. Collectively, these findings provide novel insights into virus transmission dynamics during queen production and emphasize the need to improve queen health. Author summaryHoney bee queen failure is a frequent challenge in beekeeping operations, and viral infections are increasingly recognized as an important contributor. Since no chemical therapeutics are available for managing viral diseases in honey bees, understanding routes of viral transmission is critical for developing strategies to minimize infections. However, the diversity of viruses infecting queens, their prevalence, and their main transmission routes have not been systematically investigated within the queen production industry. Therefore, in this study we investigated viral prevalence, loads, and transmission dynamics in commercial queen production operations, using a diverse array of samples, including queens at different developmental stages, worker bees from associated colonies, drones, and Varroa mites. Our analysis consistently indicates that vertical transmission from infected breeder queens, natural mating, and bank colonies with high Varroa infestations are key points where queens are most vulnerable and become infected with viruses. These findings offer novel insights into virus transmission dynamics in queens, emphasizing the importance of selecting healthy breeder queens and controlling Varroa infestations in drone source and bank colonies.

pathology↗

bioRxiv2025

Alternate Splicing Directs PMCA2 to Lysosomes and is Linked to Neurodegeneration

Plasma membrane calcium ATPases (PMCAs) are believed to function exclusively at the plasma membrane where they expel calcium from the cytosol. We have unexpectedly identified a splice variant-dependent localisation of the PMCA isoform PMCA2 to the lysosome, where it forms an evolutionarily conserved complex with NPC1, the lysosomal membrane protein defective in the rare lysosomal storage disease Niemann-Pick disease type C (NPC). This interaction is required for lysosomal Ca2+ homeostasis and implicates PMCA2 as a mediator of Ca2+ uptake into lysosomes. Disruption of the NPC1-PMCA2 complex contributes to the pathophysiology of both Niemann-Pick disease type C and Parkinsons disease, revealing an unrecognised intracellular function for PMCA2 and a shared mechanism linking lysosomal Ca2+ and lipid regulation in neurodegeneration.

cell biology↗

bioRxiv2025

TDP-43 loss of function drives aberrant splicing in Parkinson's disease

Introductory paragraphWhile mRNA splicing dysregulation is a well-established contributor to neurodegeneration in disorders such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), its role in Parkinsons disease (PD) remains underexplored. Here, we analyse transcriptomic data from >500 post-mortem human brain samples from individuals with and without PD to show that splicing alterations are frequently detected. Differentially spliced genes were significantly more enriched for those causally-implicated in both PD and ALS than genes that were differentially expressed. Furthermore, we observed a strong association between these splicing alterations and dysfunction of the RNA-binding protein (RBP), TAR DNA-binding protein 43 (TDP-43). Strikingly, genes and exon junctions affected by TDP-43 knockdown overlapped significantly with those dysregulated across brain regions in PD. In brains from individuals with the LRRK2 c.6055G>A (p.G2019S) mutation, the most common genetic cause of PD, we also observed significant enrichment of TDP-43-dependent splicing changes. This finding was corroborated in human pluripotent stem cell-derived midbrain dopaminergic neurons and a LRRK2 p.G2019S knock-in mouse model, where reduced nuclear TDP-43 levels evidenced the well-recognised loss-of-function mechanism contributing to splicing dysregulation. By leveraging our RNA-based analyses we predicted TDP-43-dependent novel peptide sequences and validated their existence within human LRRK2 mutation mDNs, while also demonstrating an overall loss of protein and mRNA expression in mis-spliced genes. Collectively, our findings reveal that PD is marked by extensive splicing dysregulation dependent on TDP-43, making TDP-43 a promising new therapeutic target in PD.

neuroscience↗

bioRxiv2025

Spatially Resolved Microglial Expression Around Aβ Plaques in Human Alzheimers Disease Tissue

Using microglia-enriched spatial transcriptomics on human Alzheimers disease tissue, we identify distinct gene expression changes across microglia located in direct contact with plaques, in periplaque regions, and in areas distant from plaques. We define a group of plaque contact-only microglial (PCOM) genes whose expression increases exclusively in microglia directly contacting plaques. These genes show significant overlap with previously reported gene sets, suggesting that many of the well-characterised disease-associated microglia (DAM) and other AD-related gene-expression signatures are only upregulated when microglia contact plaques. We further identify distinct co-expression networks associated with disease-relevant covariates, including an immune module linked to APOE genotype and a synaptic-mitochondrial module negatively associated with Braak stage. Finally, we compare the human dataset to our previously published data from 18-month-old AppNL-F mice, generated using the same experimental paradigm and demonstrate cross-species concordance in gene expression particularly within plaque-contacting microglia.

neuroscience↗

bioRxiv2025

Early oligodendrocyte dysfunction signature in Alzheimer's disease: Insights from DNA methylomics and transcriptomics

Much research into the aetiology of Alzheimers disease (AD) has focused on neuronal cell types, while studies on the contribution of glial cells, particularly oligodendrocytes (OLGs), are only starting to emerge. Altered brain DNA methylation, an epigenetic modification that provides the interplay between genetics and environmental cues to tightly regulate gene expression, is well documented in AD. Yet, cell-type-specific investigations remain limited. Here, we examine the role of DNA methylation and OLGs in AD, and how such changes may impact gene expression. We performed weighted-gene correlation network analysis (WGCNA) on multiple brain omics AD datasets across species: human DNA methylation data from 4 brain regions, human brain single-nuclei RNA sequencing data and mouse brain RNA sequencing data. We compared AD-associated network modules enriched for OLG genes across AD brain regions, as well as with other neurodegenerative disease DNA methylation datasets. We identified a DNA methylation signature associated with AD, enriched for OLGs, and preserved across brain regions representing early and late AD pathology stages. Genes within this signature showed altered expression in AD OLGs, confirming cell-type specificity and relevance to AD. This OLG signature was also preserved in transgenic mice with early A{beta} pathology and in other neurodegenerative diseases without A{beta} pathology. We reveal a consistent pattern of OLG dysfunction spanning early to late stages of AD, across DNA methylation and gene expression. Our findings highlight OLG-associated DNA methylation changes as important in AD pathogenesis, and possibly in other neurodegenerative diseases, opening new avenues for therapeutic development.

neuroscience↗

bioRxiv2025

Using targeted therapy to promote a pro-inflammatory tumour microenvironment and anti-tumour immune response in high grade serous ovarian cancer

BACKGROUNDHigh-grade serous ovarian cancer (HGSOC) is characterized by elevated replication stress and an immunosuppressive microenvironment. A synergistic combination of checkpoint kinase 1 inhibitor (CHK1i) with low-dose hydroxyurea (LDHU) promotes a unique ATR-independent moderate replication stress response with potent anti-tumour effects. The ability of this approach to reprogram the tumour immune microenvironment (TIME) to overcome the immunosuppression and promote an anti-tumour immune response in HGSOC is the focus of this study. METHODSWe investigated the therapeutic potential of CHK1i+LDHU in established HGSOC cell cultures, fresh tumour cell explants from HGSOC patient ascites, and syngeneic mouse models, assessing tumour cell killing, immunogenic cell death, pro-inflammatory cytokine/chemokine expression, and anti-tumour immune responses. RESULTSCHK1i+LDHU effectively killed ovarian cancer cells regardless of chemotherapy resistance, BRCA2 mutation and homologous recombination repair status in vitro. In vivo, treatment significantly reduced tumour burden and ascites accumulation. CHK1i+LDHU enhanced expression of pro-inflammatory cytokines/chemokines and triggered immunogenic cell death in tumour. In syngeneic models, treatment promoted CD8+ cytotoxic T cell-dependent anti-tumour responses and reduced immunosuppressive signalling within the TIME. CONCLUSIONSCHK1i+LDHU is a promising therapy for chemotherapy-resistant HGSOC, combining direct cytotoxic effects with reprogramming the TIME to reduce immunosuppression and activate a CD8+ T cell-dependent anti-tumour response.

cancer biology↗

bioRxiv2025

Noninvasive detection of bacterial biofilms using an insect olfactory brain-based gas sensor

Bacteria emit volatile organic compounds (VOCs) that can be targeted for disease detection. Biological olfactory systems have keen senses of smell, can detect VOCs at low concentrations, and are naturally adapted to classifying mixtures of VOCs as odors. Here, we employed locust (Schistocerca americana) olfactory neural circuitry to differentiate biofilm and planktonic cultures of Pseudomonas aeruginosa and Staphylococcus aureus using their odors. In vivo extracellular neural recordings were taken from the second-order olfactory processing center (antennal lobe) of locusts. The VOCs from biofilm cultures evoked distinct spiking responses compared to the planktonic cultures for both bacterial species. By analyzing the population neuronal responses, we classified individual bacterial biofilm vs. planktonic odors with up to 96% accuracy. The neural responses were highly discriminatory within the first couple of seconds of odor presentation and our analysis was conducted on less than five seconds of data, highlighting the potential of our biological sensor for real-time biofilm detection.

neuroscience↗

bioRxiv2025

Independent Generation of Amyloid-β via Novel APP Transcripts

The amyloid precursor protein (APP) is processed by multiple enzymes to generate biologically active peptides, including amyloid-{beta} (A{beta}), which aggregates to form the hallmark pathology of Alzheimers disease (AD). A{beta} is produced through an initial {beta}-secretase cleavage of APP, generating a 99-amino acid C-terminal fragment (APP-C99). Subsequent cleavage of APP-C99 by {gamma}-secretase produces A{beta} peptides of varying lengths. To better understand the transcriptional regulation of A{beta} production, we employed long-read RNA sequencing and identified previously unannotated transcripts encoding APP-C99 with an additional methionine residue (APP-C100), generated independently of {beta}-secretase cleavage. These transcripts are expressed separately from full-length APP, and we observed that cells lacking full-length APP can still produce A{beta} through these shorter isoforms. Importantly, mass spectrometry analysis of cerebrospinal fluid (CSF) revealed peptides consistent with the methionine-extended A{beta} species, supporting the in vivo translation of these transcripts. Our findings reveal an alternative pathway for A{beta} generation and aggregation, highlighting a potential new target for modulating A{beta} accumulation in AD.

neuroscience↗

bioRxiv2025

Linking Aβ and tau in the amyloid cascade through the intersection of their proteostasis networks

Amyloid plaques and neurofibrillary tangles are molecular hallmarks of Alzheimers disease. According to the amyloid cascade hypothesis, aberrant A{beta} and tau behaviours contribute synergistically to accelerate the Alzheimers pathology. However, the complex molecular mechanisms linking A{beta} and tau dysregulation remain to be fully characterised. To address this problem, we investigated the connection between A{beta} and tau through the protein homeostasis (proteostasis) network. We asked whether A{beta} proteostasis is linked to tau proteostasis. To answer to this question, we first mapped the proteostasis networks of A{beta} and tau, and then studied the interplay of these two networks, identifying the molecular chaperone HSP90 as a central hub. To test this hub role of HSP90, we observed in a cell model that HSP90 and its co-chaperone SUGT1 mediate tau phosphorylation via GSK-3{beta} in an A{beta}42-dependent manner. Furthermore, we also observed that in turn HSP90 and SUGT1 increase the intracellular concentration of A{beta}42. These results suggest that the HSP90/SUGT1 system may act as a hub in the amyloid cascade by lying at the intersection of the A{beta} and tau proteostasis networks.

neuroscience↗

bioRxiv2025

17q21.31 locus regulates Parkinson's disease relevant pathways through KANSL1 activity

An inversion polymorphism at the 17q21.31 locus defines the H1 and H2 haplotypes, with the former linked to multiple neurodegenerative disorders, including an increased risk of Parkinsons disease (PD). Although the high linkage disequilibrium at this locus has made it difficult to decipher which gene(s) drive the PD association, there is increasing evidence to support the role of KANSL1 as a risk gene. KANSL1 has been shown to regulate the expression of some PD-associated genes and pathways, likely as part of the histone acetylating non-specific lethal (NSL) complex. Here for the first time, we studied the global effects of 17q21.31 haplotype variation using bulk and single-nuclear RNA-sequencing data from control and PD patient brain. We first analysed differential gene expression across haplotype groups, and then assessed the contribution of KANSL1 by comparing with the results of an siRNA knockdown in neuronal and glial human cell lines. We demonstrated that the PD risk-associated H1 haplotype downregulates autophagy, lysosomal and mitochondrial processes, all of which have already been implicated in PD aetiology. Furthermore, these effects were apparent in both neuronal and glial cell types, and in the case of the latter, appear to be associated with the modulation of innate and adaptive immune responses. Thus, we identify important links between NSL complex activity and PD pathophysiology that can be leveraged for novel therapeutic interventions.

neuroscience↗

bioRxiv2025

Molecular and cellular signatures differentiate Parkinson's disease from Parkinson's disease with dementia

Parkinsons disease (PD) affects millions of people worldwide, and up to 40% of these patients develop dementia, profoundly affecting their quality of life. Whether Parkinsons disease dementia (PDD) simply represents a late stage of PD or constitutes a distinct neurodegenerative process remains unresolved. To clarify this, we generated the largest single nuclear transcriptomic atlas of PD and PDD to date--almost one million nuclei derived from the anterior cingulate cortex and inferior parietal lobule of 64 post-mortem donors. By integrating these data with long-read RNA-seq, we found that the cellular compositions, biological pathways, and molecular profiles diverge substantially between PD and PDD, with limited overlap in differentially expressed genes and pathways. While PD was characterised by widespread upregulation of gene expression programs and robust regional signatures, PDD showed extensive pathway downregulation, loss of cortical regional identity, and significant shifts in transcript usage, including alterations in APP isoforms that may influence pathological amyloid beta accumulation. These findings reveal that PD and PDD represent fundamentally distinct disease states, offering important insights for understanding their underlying mechanisms and will guide the development of targeted therapies and more effective clinical trials.

neuroscience↗

bioRxiv2025

Transcriptomic analysis of repeat expansion-ataxias uncovers distinct non-neuronal cell type-specific signatures of disease across the human brain

Hereditary ataxias are a heterogeneous group of neurogenetic conditions characterised by the clinical syndrome of progressive loss of coordination from neurodegeneration of the cerebellum. A commonality across the most prevalent ataxias is the underlying disease mechanism secondary to expansions of short tandem DNA repeats. There is currently an incomplete understanding of the pathogenic mechanisms of these repeat expansion disorders, a core feature of which revolves around RNA-dysregulation. In this study, we used both bulk and single nuclear RNA-sequencing to study post-mortem brain tissue of human donors with a range of repeat-expansion ataxias to reveal further mechanistic insights. We compared post-mortem paired cerebellar and frontal cortex tissue bulk RNA-sequencing data from 23 ataxia patients and 22 sex-, age-matched controls from two brain banks (spinocerebellar ataxia (SCA)1, SCA2, SCA6, SCA7, SCA17, Friedreichs ataxia (FRDA), and 7 cases with unknown molecular diagnoses). We analysed bulk RNA-sequencing data for transcript usage, differential and cell-type-specific expression to transcriptomically profile these diseases. We also generated single nuclear RNA-sequencing data of the cerebellum from donors with SCA1, SCA2, SCA6 and FRDA to decipher changes in cell type proportions in the disease state. Using this approach, we found that: (i) despite the commonalities in the genetics of ataxia, there were components of their transcriptional signatures which were distinct; (ii) there were extensive transcriptional changes evident not only in the cerebellum but also the frontal cortex in ataxia cases; (iii) activation of immune and inflammatory pathways, as well as involvement of non-neuronal cell types was a feature of all ataxias to a lesser or greater extent. This study provides a novel resource to understand the mechanisms of disease in ataxia. Furthermore, taken together, these results highlight immune pathways and the role of non-neuronal cell types as early and potentially important therapeutic targets. These findings provide a map of transcriptomic changes in ataxia to further understanding of the underlying pathogenesis.

neuroscience↗

bioRxiv2024

Age and amyloidβ-dependent initiation of neurofibrillary tau tangles: an improved mouse model of Alzheimers disease without mutations in MAPT.

The lack of models in which ageing and amyloid-{beta} (A{beta}) initiate neurofibrillary tau tangles, independent of MAPT mutations, limits mechanistic insights into Alzheimers disease. Here, we characterise NLFTaum/h, a novel mouse model that recapitulates the gradual transition from A{beta} accumulation to tau pathology by 24 months. We show that combined effects of ageing, A{beta}, and human tau expression promote tau pathology. However, either A{beta} plaques or human tau alone can initiate tau pathology, but only in even older mice. This may be exacerbated by increased neuronal vulnerability across all genotypes with age. Moreover, multi-omic analyses reveal that human tau can induce early alterations in mitochondrial and synaptic pathways, priming this latent vulnerability preceding tau pathology. Together, this suggests that ageing and other interacting triggers accelerate the onset of tau pathology. This opens possibilities for translatable testing of improved therapies for Alzheimers disease, breaking the link between A{beta} and tau pathologies.

neuroscience↗

bioRxiv2024

Mutations in PSEN1 predispose inflammation in an astrocyte model of familial Alzheimer's disease through disrupted regulated intramembrane proteolysis

Mutations in PSEN1 cause familial Alzheimers disease with almost complete penetrance. Age at onset is highly variable between different PSEN1 mutations and even within families with the same mutation. Current research into late onset Alzheimers disease implicates inflammation in both disease onset and progression. PSEN1 is the catalytic subunit of {gamma}-secretase, responsible for regulated intramembrane proteolysis of numerous substrates that include cytokine receptors. For this reason, we tested the hypothesis that mutations in PSEN1 impact inflammatory responses in astrocytes, thereby contributing to disease progression. Here, using iPSC-astrocytes, we show that PSEN1 is upregulated in response to inflammatory stimuli, and this upregulation is disrupted by pathological PSEN1 mutations. Using transcriptomic analyses, we demonstrate that PSEN1 mutant astrocytes have an augmented inflammatory profile in their basal state, concomitant with an upregulation of genes coding for regulated intramembrane proteolytic and robust activation of JAK-STAT signalling. Using JAK-STAT2 as an example signalling pathway, we show altered phosphorylation cascades in PSEN1 mutant astrocytes, reinforcing the notion of altered cytokine signalling cascades. Finally, we use small molecule modulators of {gamma}-secretase to confirm a role for PSEN1/{gamma}-secretase in regulating the astrocytic response to inflammatory stimuli. Together, these data suggest that mutations in PSEN1 enhance cytokine signalling via impaired regulated intramembrane proteolysis, thereby predisposing astrocytic inflammatory profiles. These findings support a two-hit contribution of PSEN1 mutations to fAD pathogenesis, not only impacting APP and A{beta} processing but also altering the cellular response to inflammation.

neuroscience↗

bioRxiv2024

Increased burden of rare risk variants across gene expression networks predisposes to sporadic Parkinson's disease

Alpha-synuclein (Syn) is an intrinsically disordered protein that accumulates in the brains of patients with Parkinsons disease and forms intraneuronal inclusions called Lewy Bodies. While the mechanism underlying the dysregulation of Syn in Parkinsons disease is unclear, it is thought that prionoid cell-to-cell propagation of Syn has an important role. Through a high throughput screen, we recently identified 38 genes whose knock down modulates Syn propagation. Follow up experiments were undertaken for two of those genes, TAX1BP1 and ADAMTS19, to study the mechanism with which they regulate Syn homeostasis. We used a recently developed M17D neuroblastoma cell line expressing triple mutant (E35K+E46K+E61K) "3K" Syn under doxycycline induction. 3K Syn spontaneously forms inclusions that show ultrastructural similarities to Lewy Bodies. Experiments using that cell line showed that TAX1BP1 and ADAMTS19 regulate how Syn interacts with lipids and phase separates into inclusions, respectively, adding to the growing body of evidence implicating those processes in Parkinsons disease. Through RNA sequencing, we identified several genes that are differentially expressed after knock-down of TAX1BP1 or ADAMTS19. Burden analysis revealed that those differentially expressed genes (DEGs) carry an increased frequency of rare risk variants in Parkinsons disease patients versus healthy controls, an effect that was independently replicated across two separate cohorts (GP2 and AMP-PD). Weighted gene co-expression network analysis (WGCNA) showed that the DEGs cluster within modules in regions of the brain that develop high degrees of Syn pathology (basal ganglia, cortex). We propose a novel model for the genetic architecture of sporadic Parkinsons disease: increased burden of risk variants across genetic networks dysregulates pathways underlying Syn homeostasis, thereby leading to pathology and neurodegeneration.

cell biology↗