Biology subjects

Wong, P. C.

Publications and source records attributed to Wong, P. C..

At least 19 recordsLinked to original sources

bioRxiv2026

Fine-tuning genomic models on rare splicing events identifies a novel biomarker of TDP-43 pathology

Genomic foundation models (GFMs) are pretrained on large genomic datasets, but their ability to predict rare disease-associated events after fine-tuning remains unclear. We tested this using TDP-43 cryptic exons, well characterized splicing events linked to neurodegenerative disease that are poorly represented in standard annotations. We compared the state-of-the-art GFM AlphaGenome with OpenSpliceAI, a specialized splice site prediction model. Fine-tuned OpenSpliceAI detected held-out cryptic exons in human and mouse and captured allele-specific splicing effects at the disease-associated UNC13A locus. In contrast, a splicing prediction head trained on AlphaGenome's frozen pretrained backbone failed to predict cryptic exons. Unfreezing and fine-tuning all model weights, however, enabled AlphaGenome to generalize to held-out data. To investigate cryptic splicing in cell types that are difficult to study experimentally, we applied fine-tuned OpenSpliceAI across the genome to study cell type-specific genes. This led to the identification of new cryptic splicing events in CLDN11 and ARHGAP23, which were subsequently validated in FTLD-TDP brain tissue. Notably, the cryptic exon in CLDN11 is predicted to generate a neoepitope that could serve as an oligodendrocyte-specific biomarker of TDP-43 pathology. Our results show that even a state-of-the-art GFM can fail to generalize to rare splicing events, even with substantial pretraining. However, both foundation and specialized models that learn to generalize to rare biological events can have broad applications in biological discovery and medicine.

genomics↗

bioRxiv2026

Restoring multiple TDP-43 cryptic targets, but not solely Unc13a, rescues motor neuron disease

Dysfunction of TAR DNA-binding protein 43kDa (TDP-43) underlies amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder with limited therapeutic options. While current therapeutic approaches are designed to individually target unique cryptic exons of TDP-43 such as UNC13A, the sufficiency of such a strategy to mitigate motor neuron disease remains unclear. Using a mouse model lacking TDP-43 in spinal motor neurons which mimics early stages of ALS, we show that the exclusion of Unc13a cryptic exon fails to mitigate motor neuron disease. In contrast, the restoration of multiple TDP-43 cryptic targets, including Unc13a, attenuated motor neuron loss, and rescued motor neuron disease. Additionally, compared to brain neurons, spinal motor neurons accumulate markedly lower amounts of Unc13a cryptic exons in mice and humans, suggesting that the contribution of this TDP-43 cryptic target to spinal motor neuron loss may be limited. Together, these results strongly support ALS therapeutic strategies designed to simultaneously restore multiple TDP-43 cryptic targets to attenuate spinal motor neuron loss.

neuroscience↗

bioRxiv2026

Prevention of Unc13a cryptic splicing is sufficient to preserve memory

TDP-43 dysfunction is thought to underlie frontotemporal dementia and limbic-predominant age-related TDP-43 encephalopathy, neurodegenerative dementias currently without effective therapy. Therapeutic strategies are designed to correct individual cryptic targets of TDP-43, such as UNC13A, whereby its cryptic splicing compromises synaptic function, yet the sufficiency of such an approach to prevent memory deficits is unclear. Using a forebrain neuron-specific TDP-43 knockout mouse model that recapitulates TDP-43 dysfunction occurring during early stages of human disorders, we found here that prevention of cryptic splicing to include that of Unc13a attenuated memory deficits. We show that genetic ablation of Unc13a cryptic exon solely in such TDP-43 knockout mice is sufficient to preserve cognition, supporting the clinical value of targeting UNC13A to mitigate memory deficits. Prevention of cryptic splicing of multiple targets of TDP-43 additionally attenuate neuron loss. For optimal outcomes in TDP-43 related dementias, these findings thus strongly support strategies designed to repress cryptic splicing of multiple targets of TDP-43, including UNC13A.

pathology↗

bioRxiv2026

BCG vaccination mitigates tau pathology and restores cognitive function in PS19 mice.

Retrospective studies in patients with non-muscle invasive bladder cancer (NMIBC) have reported a significant reduction in Alzheimers disease (AD) incidence (12-78%) among Bacillus Calmette-Guerin (BCG) recipients versus controls. To investigate the underlying mechanisms, we evaluated BCG in the PS19 mouse model of tauopathy. We found that BCG administration reduced hippocampal phospho-tau and microgliosis while preserving neuronal markers. In vivo volumetric T2-MRI demonstrated attenuation of brain atrophy accompanied by increased glutamate-weighted CEST-MRI signals. Functionally, BCG-treated mice showed improved performance in the novel object recognition test (NORT), as well as improved body-weight maintenance and survival. Transcriptomic profiling of the hippocampus revealed near complete normalization of the PS19 disease-associated gene expression signature towards that of healthy controls. Flow cytometric profiling of brain myeloid populations demonstrated a reduction in activated resident microglia, but total microglia cells remain elevated. Moreover, an increase of the co-stimulatory marker CD80 on the recruited peripheral myeloid cells ensues following BCG treatment. Consistent with this shift in myeloid state, primary brain myeloid cells from BCG-treated mice also exhibited enhanced phagocytosis of FITC-labeled tau fibrils and increased lactate production. Together, these findings indicate that BCG induces systemic and CNS myeloid cell reprogramming that limits neuroinflammation, enhances tau clearance, and rescues cognitive and neurodegenerative phenotypes in a tauopathy model. BCG is a safe, readily available therapy that merits consideration as a preventive agent against dementia. One sentence summaryBCG therapy prevents tauopathy in PS19 mouse model.

neuroscience↗

bioRxiv2026

Tauopathy primes co-filament assembly and dysfunction of TDP-43

While most Alzheimers disease (AD) which is associated with Limbic Predominant Age-related TDP-43 Encephalopathy (LATE) exhibits accelerated brain atrophy, the pathogenic mechanism remains elusive. We show here, in mice harboring depositions of amyloid-{beta} and tau, the age-dependent emergence of TDP-43 proteinopathy. We demonstrate that TDP-43 dysfunction facilitates caspase 3-mediated endoproteolysis of tau, accelerates tauopathy and exacerbates neuron loss. Unexpectedly, we found that the emergence and spread of TDP-43 proteinopathy is associated with the spread of tauopathy and correlated with co-filament assembly of tau and TDP-43. Importantly, TDP-43 dysfunction precedes such co-filament assembly and TDP-43 cytoplasmic aggregates. Consistent with the idea that tauopathy could prime co-filament assembly and proteinopathy of TDP-43 to exacerbate neurodegeneration, we found tau co-filament assembly with TDP-43 in AD and AD-LATE cases. These findings suggest that TDP-43 dysfunction accelerates tauopathy, which, in turn, primes co-filament assembly and dysfunction of TDP-43 to exacerbate neuron loss in AD-LATE, a pathogenic mechanism disclosing novel targets and therapeutic strategies.

neuroscience↗

bioRxiv2025

Brain Iron as a Surrogate Biomarker of Pathological TDP-43 Identifies Brain Region-Specific Signatures in Ageing, Alzheimer's Disease and Amyotrophic Lateral Sclerosis

BackgroundTDP-43 pathology is a defining feature of several neurodegenerative diseases, but its prevalence and regional distribution in ageing and disease are not well characterised. We investigated the burden of brain TDP-43 pathology across ageing, Alzheimers disease (AD), and amyotrophic lateral sclerosis (ALS), and examined ferritin as a region-specific correlate of TDP-43 pathology. MethodsPathological TDP-43 was detected using an HDGFL2 cryptic exon in situ hybridisation probe and a TDP-43 RNA aptamer, providing greater sensitivity and specificity than antibody-based approaches. Amygdala, hippocampus, and frontal cortex tissue was analysed from non-neurological controls (ages 40-80), AD cases, and ALS cases. Ferritin (as a proxy for iron accumulation) was quantified in parallel to assess its association with TDP-43 pathology. FindingsTDP-43 pathology was detectable from the fourth decade of life, with a 4.5-fold increase in hippocampal involvement after age 60 years. In AD, pathology was present in 90% of cases and distinguished from ageing by selective amygdala involvement. In ALS, TDP-43 pathology was nearly ubiquitous across all regions studied. Regional ferritin strongly predicted TDP-43 burden: amygdala ferritin explained 87% of TDP-43 variance in ALS and 66% in AD, while hippocampal ferritin differentiated AD from controls. Across AD, ferritin explained between 43-81% of regional TDP-43 variance. InterpretationTDP-43 brain pathology emerges in midlife with increased involvement after age 60 years, exhibits disease-specific regional signatures in AD and ALS, and is closely linked to ferritin accumulation. As TDP-43 confers a worse prognosis in AD, the capacity of ferritin, detectable with iron-sensitive MRI, to serve as a proxy for regional TDP-43 burden highlights its promise as a biomarker for disease stratification and prognosis. Short AbstractHere we show that pathological TDP-43 emerges during normal ageing from the fourth decade of life, with a 4.5-fold increase in hippocampal involvement after 60 years. In Alzheimers disease (AD), TDP-43 pathology was present in 90% of cases and distinguished from ageing by disproportionate amygdala involvement, while in amyotrophic lateral sclerosis (ALS) it was nearly ubiquitous across hippocampus, amygdala, and frontal cortex. Using sensitive detection tools, we demonstrate that region-specific ferritin strongly predicts TDP-43 burden: amygdala ferritin explained 87% of variance in ALS and 66% in AD, while hippocampal ferritin differentiated AD from controls. Across AD, ferritin levels in all three regions explained 43-81% of TDP-43 variance. As TDP-43 pathology confers a worse prognosis in AD, the ability of ferritin, quantifiable with iron-sensitive MRI, to serve as a proxy for regional TDP-43 burden highlights its potential as a biomarker for disease stratification and prognostic assessment. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/680028v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@9c54b3org.highwire.dtl.DTLVardef@17cb415org.highwire.dtl.DTLVardef@12dabeorg.highwire.dtl.DTLVardef@1d72f95_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LITDP-43 brain pathology occurs in normal ageing from early in the fourth decade, characterised by a 4.5-fold increase in hippocampus pathology from the sixth decade. C_LIO_LITDP-43 brain pathology is detectable in 90% of AD cases, with a disease-signature of increased amygdala pathology relative to age-matched controls. C_LIO_LIIn ALS, TDP-43 is nearly ubiquitous in amygdala, hippocampus and frontal cortex. C_LIO_LIHippocampus high brain ferritin distinguishes AD from and age-matched controls C_LIO_LIBrain ferritin is a brain region-specific marker of TDP-43 pathology in ageing and disease, with amygdala ferritin explaining 87% of the variance in amygdala TDP-43 pathology in ALS, and 66% of amygdala TDP-43 pathology in AD C_LIO_LIIn AD, ferritin levels for all three brain regions explain between 43-81% of variance in their TDP-43 pathology levels C_LI

neuroscience↗

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

Broad brain biodistribution conferred by an AAV to restore TDP-43 function mitigates Frontotemporal Demenia-like deficits

TDP-43 dysfunction is an early pathogenic determinant of frontotemporal lobar degeneration with TDP-43 pathology (FTLD-TDP), a devastating disorder currently without effective therapy. Here, we exploit a blood-brain-barrier (BBB)-permeable AAV (AAV-PHP.eB) that confers broad brain biodistribution to restore TDP-43 function in a TDP-43 deficient model (CamKIIa-CreER;Tardbp mice) that mimics the early stage of TDP-43 dysfunction occurring in FTLD-TDP. Intracerebroventricular delivery by AAV-PHP.eB of CTR, our previously characterized splicing repressor, revealed its accumulation in [~]40% of adult hippocampal neurons. Remarkably, treatment of adult CamKIIa-CreER;Tardbpf/fmice with AAV-PHP.eB-CTR restored TDP-43 function, attenuated neuronal aberrant activity and memory deficits, and rescued neuron loss. Importantly, we showed that TDP-43s autoregulatory element restricts CTR expression to a physiological range. No overt phenotype was observed after long-term exposure to AAV-PHP.eB-CTR in aged mice, highlighting a favorable safety profile for this gene therapy. These results validate that BBB-crossing AAVs can deliver CTR with a biodistribution in the adult brain that is broad enough to rescue FTD-like phenotypes, supporting clinical testing of this gene therapy for FTLD-TDP.

neuroscience↗

bioRxiv2025

Symptomatic treatment by a BBB-permeable AAV engineered to restore TDP-43 function slows motor neuron disease and prevents paralysis

TAR DNA-binding protein 43kDa (TDP-43) dysfunction is an early pathogenic mechanism that underlies amyotrophic lateral sclerosis (ALS), a devastating neurodegenerative disorder that lacks disease modifying therapies. We previously developed a mouse model in which TDP-43 is selectively deleted from motor neurons (ChAT-Cre;Tardbpf/f) that mimics the early stages of ALS. Here, we demonstrate that intravenous delivery of a blood-brain-barrier (BBB) permeable AAV capsid expressing our rationally designed splicing repressor CTR (AAV-PHP.eB-CTR) in symptomatic ChAT-Cre;Tardbpf/f mice markedly slowed disease progression and prevented paralysis. Systemic delivery of AAV-PHP.eB-CTR led to transduction of [~]80% of spinal motor neurons, repression of TDP-43-associated cryptic exons within motor neurons expressing CTR, and attenuation of motor neuron loss. Notably, the addition of the TARDBP 3UTR autoregulatory element to CTR maintained its expression within a physiological range. In control littermates that received AAV-PHP.eB-CTR and were monitored for >20 months, grip strength and body weight remained normal, and no histopathological abnormalities were observed, underscoring a favorable safety profile for this gene therapy. These results provide preclinical proof-of-concept that BBB-crossing AAV delivery of CTR can rescue motor neuron disease through the restoration of TDP-43 function, offering a promising mechanism-based therapeutic strategy for ALS.

neuroscience↗

bioRxiv2025

Inhibition of nonsense-mediated decay in TDP-43 deficient neurons reveals novel cryptic exons

TAR DNA-binding protein 43 kDa (TDP-43) is an essential splicing repressor whose loss of function underlies the pathophysiology of amyotrophic lateral sclerosis and frontotemporal dementia (ALS-FTD). Nuclear clearance of TDP-43 disrupts its function and leads to the inclusion of aberrant cryptic exons. These cryptic exons frequently introduce premature termination codons resulting in the degradation of affected transcripts through nonsense-mediated mRNA decay (NMD). Conventional RNA sequencing approaches thus may fail to detect cryptic exons that are efficiently degraded by NMD, precluding identification of potential therapeutic targets. We generated a comprehensive set of neuronal targets of TDP-43 in human iPSC-derived i3Neurons (i3N) by combining TDP-43 knockdown with inhibition of multiple factors essential for NMD, revealing novel cryptic targets. We then restored expression of selected NMD targets in TDP-43 deficient i3Ns and determined which genes improved neuronal viability. Our findings highlight the role of NMD in masking cryptic splicing events and identify novel potential therapeutic targets for TDP-43-related neurodegenerative disorders.

neuroscience↗

bioRxiv2024

Depletion of TDP-43 exacerbates tauopathy-dependent brain atrophy by sensitizing vulnerable neurons to caspase 3-mediated endoproteolysis of tau in a mouse model of Multiple Etiology Dementia

TDP-43 proteinopathy, initially disclosed in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), coexists with tauopathy in a variety of neurodegenerative disorders, termed multiple etiology dementias (MEDs), including Alzheimers Disease (AD). While such co-pathology of TDP-43 is strongly associated with worsened neurodegeneration and steeper cognitive decline, the pathogenic mechanism underlying the exacerbated neuron loss remains elusive. The loss of TDP-43 splicing repression that occurs in presymptomatic ALS-FTD individuals suggests that such early loss could facilitate the pathological conversion of tau to accelerate neuron loss. Here, we report that the loss of TDP-43 repression of cryptic exons in forebrain neurons (CaMKII-CreER;Tardbpf/f mice) is necessary to exacerbate tauopathy-dependent brain atrophy by sensitizing vulnerable neurons to caspase 3-dependent cleavage of endogenous tau to promote tauopathy. Corroborating this finding within the human context, we demonstrate that loss of TDP-43 function in iPSC-derived cortical neurons promotes early cryptic exon inclusion and subsequent caspase 3-mediated endoproteolysis of tau. Using a genetic approach to seed tauopathy in CaMKII-CreER;Tardbpf/fmice by expressing a four-repeat microtubule binding domain of human tau, we show that the amount of tau seed positively correlates with levels of caspase 3-cleaved tau. Importantly, we found that the vulnerability of hippocampal neurons to TDP-43 depletion is dependent on the amount of caspase 3-cleaved tau: from most vulnerable neurons in the CA2/3, followed by those in the dentate gyrus, to the least in CA1. Taken together, our findings strongly support the view that TDP-43 loss-of-function exacerbates tauopathy-dependent brain atrophy by increasing the sensitivity of vulnerable neurons to caspase 3-mediated endoproteolysis of tau, resulting in a greater degree of neurodegeneration in human disorders with co-pathologies of tau and TDP-43. Our work thus discloses novel mechanistic insights and therapeutic targets for human tauopathies harboring co-pathology of TDP-43 and provides a new MED model for testing therapeutic strategies. HighlightsO_LILoss of TDP-43 repression of cryptic exons is necessary for caspase 3-dependent endoproteolysis of tau at D421 in the mouse brain and human iPSC-derived cortical neurons. C_LIO_LIThe level of caspase 3-dependent cleavage of tau is a major determinant of the vulnerability of mouse brain neurons lacking TDP-43. C_LIO_LIIn a novel mouse model of multiple etiology dementia, TDP-43 loss-of-function exacerbates tauopathy-dependent brain atrophy by sensitizing vulnerable neurons to caspase 3-mediated endoproteolysis of tau to drive tauopathy. C_LIO_LIIn human tauopathies with co-pathology of TDP-43, dysfunction of TDP-43 may promote caspase 3-dependent cleavage of endogenous tau in vulnerable neurons and exacerbate tauopathy-dependent neurodegeneration. C_LI SummaryThe pathogenic mechanism by which TDP-43 loss of repression function exacerbates tauopathy-dependent neurodegeneration in multiple etiology dementia (MED) with co-pathology of TDP-43 is unknown. In a novel mouse model of MED, loss of TDP-43 function exacerbates tauopathy-dependent brain atrophy by sensitizing vulnerable neurons to caspase 3-dependent cleavage of endogenous tau to drive tauopathy. This mechanistic insight informs novel targets and therapeutic strategies for MEDs harboring the co-pathologies of tau and TDP-43, which can be validated using this mouse model of MED.

neuroscience↗

bioRxiv2024

Large-scale RNA-seq mining reveals ciclopirox triggers TDP-43 cryptic exons

Nuclear clearance and cytoplasmic aggregation of TDP-43 in neurons, initially identified in ALS-FTD, are hallmark pathological features observed across a spectrum of neurodegenerative diseases. We previously found that TDP-43 loss-of-function leads to the transcriptome-wide inclusion of deleterious cryptic exons in brains and biofluids post-mortem as well as during the presymptomatic stage of ALS-FTD, but upstream mechanisms that lead to TDP-43 dysregulation remain unclear. Here, we developed a web-based resource (SnapMine) to determine the levels of TDP-43 cryptic exon inclusion across hundreds of thousands of publicly available RNA sequencing datasets. We established cryptic exon inclusion across a variety of human cells and tissues to provide ground truth references for future studies on TDP-43 dysregulation. We then explored studies that were entirely unrelated to TDP-43 or neurodegeneration and found that ciclopirox olamine (CPX), an FDA-approved antifungal, can trigger the inclusion of TDP-43-associated cryptic exons in a variety of mouse and human primary cells. CPX induction of cryptic exon occurs via heavy metal toxicity and oxidative stress, suggesting that similar vulnerabilities could play a role in neurodegeneration. Our work demonstrates how diverse datasets can be linked through common biological features and underscores that public archives of sequencing data represent a vastly underutilized resource with tremendous potential for uncovering novel insights into complex biological mechanisms and diseases.

neuroscience↗

bioRxiv2023

Brain Templates for Chinese Babies from Newborn to Three Months of Age

The infant brain develops rapidly and this area of research has great clinical implications. Neurodevelopmental disorders such as autism and developmental delay have their origins, potentially, in abnormal early brain maturation. Searching for potential early neural markers requires a priori knowledge about infant brain development and anatomy. One of the most common methods of characterizing brain features requires normalization of individual images into a standard stereotactic space and conduct of group-based analyses in this space. A population representative brain template is critical for these population-based studies. Little research is available on constructing brain templates for typical developing Chinese infants. In the present work, a total of 112 babies from 6 to 98 days of age were included with high resolution structural magnetic resonance imaging scans. T1-weighted and T2-weighted templates were constructed using an unbiased registration approach for babies from newborn to 3 months of age. Age-specific templates were also estimated for babies aged at 0, 1, 2 and 3 months old. Then we conducted a series of evaluations and statistical analyses over whole tissue segmentations and brain parcellations. Compared to the use of population mismatched templates, using our established templates resulted in lower deformation energy to transform individual images into the template space and produced a smaller registration error, i.e., smaller standard deviation of the registered images. Significant volumetric growth was observed across total brain tissues and most of the brain regions within the first three months of age. The total brain tissues exhibited larger volumes in baby boys compared to baby girls. To the best of our knowledge, this is the first study focusing on the construction of Chinese infant brain templates. These templates can be used for investigating birth related conditions such as preterm birth, detecting neural biomarkers for neurological and neurodevelopmental disorders in Chinese populations, and exploring genetic and cultural effects on the brain.

neuroscience↗

bioRxiv2023

Pathological Tau transmission initiated by binding lymphocyte-activation gene 3

The spread of prion-like protein aggregates is believed to be a common driver of pathogenesis in many neurodegenerative diseases. Accumulated tangles of filamentous Tau protein are considered pathogenic lesions of Alzheimers disease (AD) and related Tauopathies, including progressive supranuclear palsy, and corticobasal degeneration. Tau pathologies in these illnesses exhibits a clear progressive and hierarchical spreading pattern that correlates with disease severity1, 2. Clinical observation combined with complementary experimental studies3, 4 have shown that Tau preformed fibrils (PFF) are prion-like seeds that propagate pathology by entering cells and templating misfolding and aggregation of endogenous Tau. While several receptors of Tau are known, they are not specific to the fibrillar form of Tau. Moreover, the underlying cellular mechanisms of Tau PFF spreading remains poorly understood. Here, we show that the lymphocyte-activation gene 3 (Lag3) is a cell surface receptor that binds to PFF, but not monomer, of Tau. Deletion of Lag3 or inhibition of Lag3 in primary cortical neurons significantly reduces the internalization of Tau PFF and subsequent Tau propagation and neuron-to-neuron transmission. Propagation of Tau pathology and behavioral deficits induced by injection of Tau PFF in the hippocampus and overlying cortex are attenuated in mice lacking Lag3 selectively in neurons. Our results identify neuronal Lag3 as a receptor of pathologic Tau in the brain, and for AD and related Tauopathies a therapeutic target. One Sentence SummaryLag3 is a neuronal receptor specific for Tau PFF, and is required for uptake, propagation and transmission of Tau pathology.

neuroscience↗

bioRxiv2023

Elevated nuclear TDP-43 induces constitutive exon skipping

Cytoplasmic inclusions and loss of nuclear TDP-43 are key pathological features found in several neurodegenerative disorders, suggesting both gain- and loss-of-function mechanisms of disease. To study gain-of-function, TDP-43 overexpression has been used to generate in vitro and in vivo model systems. Our study shows that excessive levels of nuclear TDP-43 protein lead to constitutive exon skipping that is largely species-specific. Furthermore, while aberrant exon skipping is detected in some human brains, it is not correlated with disease, unlike the incorporation of cryptic exons that occurs after loss of TDP-43. Our findings emphasize the need for caution in interpreting TDP-43 overexpression data, and stress the importance of controlling for exon skipping when generating models of TDP-43 proteinopathy. Understanding the subtle aspects of TDP-43 toxicity within different subcellular locations is essential for the development of therapies targeting neurodegenerative disease.

neuroscience↗

bioRxiv2023

A fluid biomarker reveals loss of TDP-43 splicing repression in pre-symptomatic ALS

Loss of TAR DNA-binding protein 43 kDa (TDP-43) splicing repression is well-documented in postmortem tissues of amyotrophic lateral sclerosis (ALS), yet whether this abnormality occurs during early-stage disease remains unresolved. Cryptic exon inclusion reflects functional loss of TDP-43, and thus detection of cryptic exon-encoded peptides in cerebrospinal fluid (CSF) could reveal the earliest stages of TDP-43 dysregulation in patients. Here, we use a newly characterized monoclonal antibody specific to a TDP-43-dependent cryptic epitope (encoded by the cryptic exon found in HDGFL2) to show that loss of TDP-43 splicing repression occurs in C9ORF72-associated ALS, including pre-symptomatic mutation carriers. In contrast to neurofilament light and heavy chain proteins, cryptic HDGFL2 accumulates in CSF at higher levels during early stages of disease. Our findings indicate that loss of TDP-43 splicing repression occurs early in disease progression, even pre-symptomatically, and that detection of HDGFL2s cryptic neoepitope may serve as a prognostic test for ALS which should facilitate patient recruitment and measurement of target engagement in clinical trials.

molecular biology↗

bioRxiv2021

Stage-specific control of oligodendrocyte survival and morphogenesis by TDP-43

Generation of oligodendrocytes in the adult brain enables both adaptive changes in neural circuits and regeneration of myelin sheaths destroyed by injury, disease, and normal aging. This transformation of oligodendrocyte precursor cells (OPCs) into myelinating oligodendrocytes requires processing of distinct mRNAs at different stages of cell maturation. Although mislocalization and aggregation of the RNA binding protein TDP-43 occur in both neurons and glia in neurodegenerative diseases, the consequences of TDP-43 loss within different stages of the oligodendrocyte lineage are not well understood. By performing stage-specific genetic inactivation of Tardbp in vivo, we show that oligodendrocyte lineage cells are differentially sensitive to loss of TDP-43. While OPCs depend on TDP-43 for survival, with conditional deletion resulting in cascading cell loss followed by rapid regeneration to restore their density, oligodendrocytes become less sensitive to TDP-43 depletion as they mature. Deletion of TDP-43 early in the maturation process led to eventual oligodendrocyte degeneration, seizures and premature lethality, while oligodendrocytes that experienced late deletion survived and mice exhibited a normal lifespan. At both stages, TDP-43 deficient oligodendrocytes formed fewer and thinner myelin sheaths and extended new processes that inappropriately wrapped neuronal somata and blood vessels. Transcriptional analysis revealed that in the absence of TDP-43, key proteins involved in oligodendrocyte maturation and myelination were misspliced leading to aberrant incorporation of cryptic exons. Inducible deletion of TDP-43 from oligodendrocytes in the adult CNS induced the same progressive morphological changes and mice acquired profound hindlimb weakness, suggesting that loss of TDP-43 function in oligodendrocytes may contribute to neuronal dysfunction in neurodegenerative disease.

neuroscience↗

bioRxiv2021

Amyloid-beta and tau pathologies are both necessary to induce novel stage-specific microglia subtypes during Alzheimer's disease progression.

It is unknown whether specific microglia are selectively induced by amyloid-{beta} (A{beta}), tau pathologies, or both in combination. To address this, we use single-cell RNA-sequencing to profile mice bearing both A{beta} and tau pathologies during Alzheimers disease (AD) progression. We identify novel microglia subtypes induced in a disease stage-specific manner. We show that during early-stage disease, interferon signaling induces a subtype of microglia termed EADAM. During late-stage disease, a second microglia subtype termed LADAM is detected. While EADAM and LADAM-like microglia are observed in other neurodegenerative models, the magnitude and composition of subtype markers are distinct from microglia observed with AD-like pathology. The pattern of EADAM- and LADAM-associated gene expression is observed in microglia from human AD, during the early and late stages of disease, respectively. Furthermore, we observe that several siglec genes are selectively expressed in either EADAM or LADAM. Siglecg is expressed in white-matter-associated LADAM, and expression of the human orthologue of Siglecg is progressively elevated in AD-stage-dependent manner but not shown in non-AD tauopathy. Our findings imply that both A{beta} and tau pathologies are required for disease stage-specific induction of EADAM and LADAM.

neuroscience↗