Biology subjects

Zinman, L.

Publications and source records attributed to Zinman, L..

8 recordsLinked to original sources

bioRxiv2024

C9orf72 expansion creates the unstable folate-sensitive fragile site FRA9A

The hyper-unstable Chr9p21 locus, harbouring the interferon gene cluster, oncogenes and C9orf72, is linked to multiple diseases. C9orf72 (GGGGCC)n expansions (C9orf72Exp) are associated with incompletely penetrant amyotrophic lateral sclerosis, frontotemporal dementia and autoimmune disorders. C9orf72Exp patients display hyperactive cGAS-STING-linked interferon immune and DNA damage responses, but the source of immuno-stimulatory or damaged DNA is unknown. Here, we show C9orf72Exp in pre-symptomatic and ALS-FTD patient cells and brains cause the folate- sensitive chromosomal fragile site, FRA9A. FRA9A centers on >33kb of C9orf72 as highly-compacted chromatin embedded in an 8.2Mb fragility zone spanning 9p21, encompassing 46 genes, making FRA9A one of the largest fragile sites. C9orf72Exp cells show chromosomal instability, heightened global- and Chr9p-enriched sister-chromatid exchanges, truncated-Chr9s, acentric-Chr9s and Chr9-containing micronuclei, providing endogenous sources of damaged and immunostimulatory DNA. Cells from one C9orf72Exp patient contained highly-rearranged FRA9A-expressing Chr9 with Chr9-wide dysregulated gene expression. Somatic C9orf72Exp repeat instability and chromosomal fragility are sensitive to folate-deficiency. Age-dependent repeat instability, chromosomal fragility, and chromosomal instability can be transferred to CNS and peripheral tissues of transgenic C9orf72Exp mice, implicating C9orf72Exp as the source. Our results highlight unappreciated effects of C9orf72 expansions that trigger vitamin-sensitive chromosome fragility, adding structural variations to the disease-enriched 9p21 locus, and likely elsewhere. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=94 SRC="FIGDIR/small/620312v2_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@154b23borg.highwire.dtl.DTLVardef@1814a6dorg.highwire.dtl.DTLVardef@13d713eorg.highwire.dtl.DTLVardef@d5d994_HPS_FORMAT_FIGEXP M_FIG C_FIG

genetics↗

bioRxiv2023

Single-nucleus multiomic atlas of frontal cortex in amyotrophic lateral sclerosis with a deep learning-based decoding of alternative polyadenylation mechanisms

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are two age-related and fatal neurodegenerative disorders that lie on a shared disease spectrum. While both disorders involve complex interactions between neuronal and glial cells, the specific cell-type alterations and their contributions to disease pathophysiology remain incompletely understood. Here, we applied single-nucleus RNA sequencing of the orbitofrontal cortex, a region affected in ALS-FTLD, to map cell-type specific transcriptional signatures in C9orf72-related ALS (with and without FTLD) and sporadic ALS cases. Our findings reveal disease- and cell-type-specific transcriptional changes, with neurons exhibiting the most pronounced alterations, primarily affecting mitochondrial function, protein homeostasis, and chromatin remodeling. A comparison with independent datasets from different cortical regions of C9orf72 and sporadic ALS cases showed concordance in several pathways, with neuronal STMN2 and NEFL showing consistent up-regulation between brain regions and disease subtypes. We also interrogated alternative polyadenylation (APA) as an additional layer of transcriptional regulation, demonstrating that APA events are not correlated with identified gene expression changes. To interpret these events, we developed APA-Net, a deep learning model that integrates transcript sequences with RNA-binding protein expression profiles, revealing cell type-specific patterns of APA regulation. Our atlas illuminates cell type-specific pathomechanisms of ALS/FTLD, providing a valuable resource for further investigation.

neuroscience↗

bioRxiv2023

KCC2 as a novel biomarker and therapeutic target for motoneuron degenerative disease

Hyperexcitability in cells throughout the corticospinal tract is a presymptomatic feature of amyotrophic lateral sclerosis (ALS) associated with lethal motor degeneration 1-6. Disinhibition is a possible cause of this hyperexcitability, potentially implicating the central nervous system-specific potassium-chloride cotransporter, KCC2, a core regulator of the strength of GABAergic neurotransmission linked to several neurological disorders 7-11. Here, we show that KCC2 is downregulated in the membrane of motor cortex neurons from post-mortem SOD1-, C9orf72- and sporadic ALS is patients. Increased protein levels of KCC2 were found in plasma and cerebral spinal fluid of ALS patients and mice harbouring the SOD1*G93A mutation. Longitudinal analysis of disease progression in both SOD1*G93A and Prp-TDP43*A315T mice revealed a decrease of KCC2 membrane levels in cortical and spinal motor neurons which were already present at the presymptomatic phase. Using KCC2-enhancing compounds, CLP290 and prochlorperazine (PCPZ) restored KCC2 membrane expression and function, delayed motor deficit onset, and extended lifespan up to two months in mutant mice. Human-derived neurons differentiated from iPSC harbouring the SOD1*G93A mutation displayed KCC2 deficits which PCPZ treatment rescued. Acute administration of KCC2 enhancers restored chloride transport in presymptomatic and symptomatic mice and reversed motor neuron hyperexcitability in awake behaving mutant mice. These findings identify KCC2 as both an early biomarker and a disease-modifying therapeutic target for ALS.

neuroscience↗

bioRxiv2022

Loss of mitochondrial Chchd10 or Chchd2 in zebrafish leads to an ALS-like phenotype and Complex I deficiency independent of the mt-ISR

Mutations in CHCHD10 and CHCHD2, coding for two paralogous mitochondrial proteins, have been identified in amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTD), and Parkinsons disease (PD). Here we investigated the biological roles of these proteins during vertebrate development using knockout (KO) models in zebrafish. We demonstrate that loss of either or both proteins leads to a motor impairment, reduced survival, and compromised neuromuscular junction (NMJ) integrity in larval zebrafish. Compensation by Chchd10 was observed in the chchd2-/- model, but not by Chchd2 in the chchd10 -/- model. The assembly of mitochondrial respiratory chain Complex I was impaired in chchd10 -/- and chchd2 -/- zebrafish larvae, but unexpectedly not in the double chchd10 -/- & chchd2 -/- model, suggesting that reduced mitochondrial Complex I cannot be solely responsible for the observed phenotypes, which are generally more severe in the double KO. Activation of the mitochondrial integrated stress response (mt-ISR) was only observed in the double KO model, possibly implicating this pathway in the recovery of the Complex I defect, and suggesting that Complex I assembly defect in our single KO is independent of the mt-ISR. Our results demonstrate that both proteins are required for normal vertebrate development, but their precise molecular function in the mitochondrial biology of motor neurons remains to be discovered.

developmental biology↗

bioRxiv2021

Investigating the Contribution of White Matter Hyperintensities and Cortical Thickness to Empathy in Neurodegenerative and Cerebrovascular Diseases

Introduction: Change in empathy is an increasingly recognised symptom of neurodegenerative diseases and contributes to caregiver burden and patient distress. Empathy impairment has been associated with brain atrophy but its relationship to white matter hyperintensities (WMH) is unknown. We aimed to investigate the relationships amongst WMH, brain atrophy, and empathy deficits in neurodegenerative and cerebrovascular diseases. Methods: 513 participants with Alzheimers Disease/Mild Cognitive Impairment, Amyotrophic Lateral Sclerosis, Frontotemporal Dementia (FTD), Parkinsons Disease, or Cerebrovascular Disease (CVD) were included. Empathy was assessed using the Interpersonal Reactivity Index. WMH were measured using a semi-automatic segmentation and FreeSurfer was used to measure cortical thickness. Results: A heterogeneous pattern of cortical thinning was found between groups, with FTD showing thinning in frontotemporal regions and CVD in left superior parietal, left insula, and left postcentral. Results from both univariate and multivariate analyses revealed that several variables were associated with empathy, particularly cortical thickness in the fronto-insulo-temporal and cingulate regions, sex(female), global cognition, and right parietal and occipital WMH. Conclusions: Our results suggest that cortical atrophy and WMH may be associated with empathy deficits in neurodegenerative and cerebrovascular diseases. Future work should consider investigating the longitudinal effects of WMH and atrophy on empathy deficits in neurodegenerative and cerebrovascular diseases.

neuroscience↗

bioRxiv2020

TDP-43 stabilizes transcripts encoding stress granule protein G3BP1: potential relevance to ALS/FTD

TDP-43 nuclear depletion and concurrent cytoplasmic accumulation in vulnerable neurons is a hallmark feature of progressive neurodegenerative proteinopathies such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Cellular stress signalling and stress granule dynamics are now recognized to play a role in ALS/FTD pathogenesis. Defective stress granule assembly is associated with increased cellular vulnerability and death. G3BP1 (Ras-GAP SH3-domain-binding protein 1) is a critical stress granule assembly factor. Here, we define that TDP-43 stabilizes G3BP1 transcripts via direct binding of a highly conserved cis regulatory element within the 3UTR. Moreover, we show in vitro and in vivo that nuclear TDP-43 depletion is sufficient to reduce G3BP1 protein levels. Finally, we establish that G3BP1 transcripts are reduced in ALS/FTD patient neurons bearing TDP-43 cytoplasmic inclusions/nuclear depletion. Thus, our data suggest that, in ALS/FTD, there is a compromised stress granule response in disease-affected neurons due to impaired G3BP1 mRNA stability caused by TDP-43 nuclear depletion. These data implicate TDP-43 and G3BP1 loss of function as contributors to disease.

neuroscience↗

bioRxiv2020

Cerebral Atrophy in Amyotrophic Lateral Sclerosis Parallels the Pathological Distribution of TDP43

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by a preferential involvement of both upper and lower motor neurons. Evidence from neuroimaging and post-mortem studies confirms additional involvement of brain regions extending beyond the motor cortex. The aim of this study was to assess the extent of cerebral disease in ALS cross-sectionally and longitudinally, and to compare the findings with a recently proposed disease-staging model of ALS pathology. Deformation-based morphometry (DBM) was used to identify the patterns of brain atrophy associated with ALS and to assess their relationship with clinical symptoms. Longitudinal T1-weighted MRI data and clinical measures were acquired at baseline, 4 months, and 8 months, from 66 ALS patients and 43 age-matched controls who participated in the Canadian ALS Neuroimaging Consortium (CALSNIC) study. Whole brain voxel-wise mixed-effects modelling analysis showed extensive atrophy patterns differentiating ALS patients from the normal controls. Cerebral atrophy was present in the motor cortex and corticospinal tract, involving both GM and WM, and to a lesser extent in non-motor regions. More specifically, the results showed significant bilateral atrophy in the motor cortex, the corticospinal tract including the internal capsule and brainstem, with an overall pattern of ventricular enlargement; along with significant progressive longitudinal atrophy in the precentral gyrus, frontal and parietal white matter, accompanied by ventricular and sulcal enlargement. Atrophy in the precentral gyrus was significantly associated with greater disability as quantified with the ALS Functional Rating Scale-Revised (ALSFRS-R) (p<0.0001). The pattern of atrophy observed using DBM was consistent with the Brettschneiders four stage pathological model of the disease. Deformation based morphometry provides a sensitive indicator of atrophy in ALS, and has potential as a biomarker of disease burden, in both gray and white matter.

neuroscience↗

bioRxiv2019

FUS gene is dual-coding with both proteins united in molecular hallmarks of amyotrophic lateral sclerosis

Novel functional coding sequences (altORFs) are camouflaged within annotated ones (CDS) in a different reading frame. We discovered an altORF nested in the FUS CDS encoding a conserved 169 amino acid protein, altFUS. AltFUS is endogenously expressed in human tissues, notably in the motor cortex and motor neurons. Overexpression of wild-type FUS and/or amyotrophic lateral sclerosis-linked FUS mutants is known to trigger toxic mechanisms in different models. These include an inhibition of autophagy, loss of mitochondrial potential, and accumulation of cytoplasmic aggregates. We show here that altFUS, not FUS, is responsible for the inhibition of autophagy. AltFUS is also pivotal in the mechanisms leading to the mitochondrial potential loss and accumulation of cytoplasmic aggregates. Suppression of altFUS expression in a Drosophila model of FUS-related toxicity protects against neurodegeneration. Some mutations found in ALS patients are overlooked because of their synonymous effect on the FUS protein. Yet we showed they exert a deleterious effect via their missense consequence on the overlapping altFUS protein. These findings demonstrate that FUS is a bicistronic gene and suggest that both proteins, FUS and altFUS, cooperate in toxic mechanisms.

genetics↗