TDP-43 Is Associated with Subiculum and Cornu Ammonis 1 Hippocampal Subfield Atrophy in Primary Age-Related Tauopathy.

Background: TAR DNA binding protein 43 (TDP-43) has been shown to be associated with whole hippocampal atrophy in primary age-related tauopathy (PART). It is currently unknown which subregions of the hippocampus are contributing to TDP-43 associated whole hippocampal atrophy in PART. Objective: To identify which specific hippocampal subfield regions are contributing to TDP-43-associated whole hippocampal atrophy in PART. Methods: A total of 115 autopsied cases from the Mayo Clinic Alzheimer Disease Research Center, Neurodegenerative Research Group, and the Mayo Clinic Study of Aging were analyzed. All cases underwent antemortem brain volumetric MRI, neuropathological assessment of the distribution of Aß (Thal phase), and neurofibrillary tangle (Braak stage) to diagnose PART, as well as assessment of TDP-43 presence/absence in the amygdala, hippocampus and beyond. Hippocampal subfield segmentation was performed using FreeSurfer version 7.4.1. Statistical analyses using logistic regression were performed to assess for associations between TDP-43 and hippocampal subfield volumes, accounting for potential confounders. Results: TDP-43 positive patients (n = 37, 32%), of which 15/15 were type-α, had significantly smaller whole hippocampal volumes, and smaller volumes of the body and tail of the hippocampus compared to TDP-43 negative patients. Subfield analyses revealed an association between TDP-43 and the molecular layer of hippocampal body and the body of cornu ammonis 1 (CA1), subiculum, and presubiculum regions. There was no association between TDP-43 stage and subfield volumes. Conclusions: Whole hippocampal volume loss linked to TDP-43 in PART is mainly due to volume loss occurring in the molecular layer, CA1, subiculum and presubiculum of the hippocampal body.

A multimodal clinical diagnostic approach using MRI and 18F-FDG-PET for antemortem diagnosis of TDP-43 in cases with low-intermediate Alzheimer's disease neuropathologic changes and primary age-related tauopathy.

OBJECTIVE: To evaluate the utility of clinical assessment scales for MRI and 18F-FDG-PET as potential in vivo predictive diagnostic tools for TAR DNA-binding protein of 43 kDa (TDP-43) proteinopathy in cases with low-intermediate Alzheimer's disease neuropathologic changes (ADNC) and primary age-related tauopathy (PART). METHODS: We conducted a cross-sectional analysis on patients with antemortem MRI and 18F-FDG-PET scans and postmortem diagnosis of low-intermediate ADNC or PART (Braak stage ≤ III; Thal ß-amyloid phase 0-5). We employed visual imaging scales to grade structural changes on MRI and metabolic changes on 18F-FDG-PET and statistically compared demographic and clinicopathological characteristics between TDP-43 positive and negative cases. Independent regression analyses were performed to assess further influences of pathological characteristics on imaging outcomes. Within-reader repeatability and inter-reader reliability were calculated (CI = 0.95). Additional quantitative region-of-interest analyses of MRI gray matter volumes and PET ligand uptake were performed. RESULTS: Of the 64 cases in the study, 20 (31%) were TDP-43 ( +), of which 12 (60%) were female. TDP-43 ( +) cases were more likely to have hippocampal sclerosis (HS) (p = 0.014) and moderate-severe medial temporal lobe atrophy on MRI (p = 0.048). TDP-43( +) cases also showed a trend for less parietal atrophy on MRI (p = 0.086) and more medial temporal lobe hypometabolism on 18F-FDG-PET (p = 0.087) than TDP-43( - ) cases. Regression analysis showed an association between medial temporal hypometabolism and HS (p = 0.0113). ICC values for MRI and PET within one reader were 0.75 and 0.91; across two readers were 0.79 and 0.82. The region-of-interest-based analysis confirmed a significant difference between TDP-43( +) and TDP-43( - ) cases for medial temporal lobe gray matter volume on MRI (p = 0.014) and medial temporal metabolism on PET (p = 0.011). CONCLUSION: Visual inspection of the medial temporal lobe on MRI and FDG-PET may help to predict TDP-43 status in the context of low-intermediate ADNC and PART.

Frontotemporal dementia: from genetics to therapeutic approaches.

INTRODUCTION: Frontotemporal dementia (FTD) includes a group of neurodegenerative diseases characterized clinically by behavioral disturbances and by neurodegeneration of brain anterior temporal and frontal lobes, leading to atrophy. Apart from symptomatic treatments, there is, at present, no disease-modifying cure for FTD. AREAS COVERED: Three main mutations are known as causes of familial FTD, and large consortia have studied carriers of mutations, also in preclinical Phases. As genetic cases are the only ones in which the pathology can be predicted in life, compounds developed so far are directed toward specific proteins or mutations. Herein, recently approved clinical trials will be summarized, including molecules, mechanisms of action and pharmacological testing. EXPERT OPINION: These studies are paving the way for the future. They will clarify whether single mutations should be addressed rather than common proteins depositing in the brain to move from genetic to sporadic FTD.

Anterior insula is more vulnerable than posterior insula to TDP-43 pathology in common dementias and ALS.

Based on the anatomic proximity, connectivity, and functional similarities between the anterior insula and amygdala, we tested the hypothesis that the anterior insula is an important focus in the progression of TDP-43 pathology in LATE-NC. Blinded to clinical and neuropathologic data, phospho-TDP (pTDP) inclusion pathology was assessed in paired anterior and posterior insula samples in 105 autopsied patients with Alzheimer disease, Lewy body disease, LATE-NC and hippocampal sclerosis (HS), amyotrophic lateral sclerosis (ALS), and other conditions. Insular pTDP pathology was present in 34.3% of the study cohort, most commonly as neuronal inclusions and/or short neurites in lamina II, and less commonly as subpial processes resembling those described in the amygdala region. Among positive samples, pTDP pathology was limited to the anterior insula (41.7%), or occurred in both anterior and posterior insula (58.3%); inclusion density was greater in anterior insula across all diseases (p < .001). pTDP pathology occurred in 46.7% of ALS samples, typically without a widespread TDP-43 proteinopathy. In LATE-NC, it was seen in 30.4% of samples (mostly LATE-NC stages 2 and 3), often co-occurring with basal forebrain pathology and comorbid HS, suggesting this is an important step in the evolution of this pathology beyond the medial temporal lobe.

Detection of TDP-43 seeding activity in the olfactory mucosa from patients with frontotemporal dementia.

INTRODUCTION: We assessed TAR DNA-binding protein 43 (TDP-43) seeding activity and aggregates detection in olfactory mucosa of patients with frontotemporal lobar degeneration with TDP-43-immunoreactive pathology (FTLD-TDP) by TDP-43 seeding amplification assay (TDP43-SAA) and immunocytochemical analysis. METHODS: The TDP43-SAA was optimized using frontal cortex samples from 16 post mortem cases with FTLD-TDP, FTLD with tau inclusions, and controls. Subsequently, olfactory mucosa samples were collected from 17 patients with FTLD-TDP, 15 healthy controls, and three patients carrying MAPT variants. RESULTS: TDP43-SAA discriminated with 100% accuracy post mortem cases presenting or lacking TDP-43 neuropathology. TDP-43 seeding activity was detectable in the olfactory mucosa, and 82.4% of patients with FTLD-TDP tested positive, whereas 86.7% of controls tested negative (P < 0.001). Two out of three patients with MAPT mutations tested negative. In TDP43-SAA positive samples, cytoplasmatic deposits of phosphorylated TDP-43 in the olfactory neural cells were detected. DISCUSSION: TDP-43 aggregates can be detectable in olfactory mucosa, suggesting that TDP43-SAA might be useful for identifying and monitoring FTLD-TDP in living patients.

Different cohort, disparate results: Selection bias is a key factor in autopsy cohorts.

INTRODUCTION: Research-oriented autopsy cohorts provide critical insights into dementia pathobiology. However, different studies sometimes report disparate findings, partially because each study has its own recruitment biases. We hypothesized that a straightforward metric, related to the percentage of research volunteers cognitively normal at recruitment, would predict other inter-cohort differences. METHODS: The National Alzheimer's Coordinating Center (NACC) provided data on N = 7178 autopsied participants from 28 individual research centers. Research cohorts were grouped based on the proportion of participants with normal cognition at initial clinical visit. RESULTS: Cohorts with more participants who were cognitively normal at recruitment contained more individuals who were older, female, had lower frequencies of apolipoprotein E ε4, Lewy body disease, and frontotemporal dementia, but higher rates of cerebrovascular disease. Alzheimer's disease (AD) pathology was little different between groups. DISCUSSION: The percentage of participants recruited while cognitively normal predicted differences in findings in autopsy research cohorts. Most differences were in non-AD pathologies. HIGHLIGHTS: Systematic differences exist between autopsy cohorts that serve dementia research. We propose a metric to use for gauging a research-oriented autopsy cohort. It is essential to consider the characteristics of autopsy cohorts.

A complex network of interdomain interactions underlies the conformational ensemble of monomeric TDP-43 and modulates its phase behavior.

TAR DNA-binding protein 43 (TDP-43) is a multidomain protein involved in the regulation of RNA metabolism, and its aggregates have been observed in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Numerous studies indicate TDP-43 can undergo liquid-liquid phase separation (LLPS) in vitro and is a component of biological condensates. Homo-oligomerization via the folded N-terminal domain (aa:1-77) and the conserved helical region (aa:319-341) of the disordered, C-terminal domain is found to be an important driver of TDP-43 phase separation. However, a comprehensive molecular view of TDP-43 phase separation, particularly regarding the nature of heterodomain interactions, is lacking due to the challenges associated with its stability and purification. Here, we utilize all-atom and coarse-grained (CG) molecular dynamics (MD) simulations to uncover the network of interdomain interactions implicated in TDP-43 phase separation. All-atom simulations uncovered the presence of transient, interdomain interactions involving flexible linkers, RNA-recognition motif (RRM) domains and a charged segment of disordered C-terminal domain (CTD). CG simulations indicate these inter-domain interactions which affect the conformational landscape of TDP-43 in the dilute phase are also prevalent in the condensed phase. Finally, sequence and surface charge distribution analysis coupled with all-atom simulations (at high salt) confirmed that the transient interdomain contacts are predominantly electrostatic in nature. Overall, our findings from multiscale simulations lead to a greater appreciation of the complex interaction network underlying the structural landscape and phase separation of TDP-43.

Molecular fragment characteristics and distribution of tangle associated TDP-43 (TATs) and other TDP-43 lesions in Alzheimer's disease.

TAR DNA binding protein 43 (TDP-43) pathology is a defining feature of frontotemporal lobar degeneration (FTLD). In FTLD-TDP there is a moderate-to-high burden of morphologically distinctive TDP-43 immunoreactive inclusions distributed throughout the brain. In Alzheimer's disease (AD), similar TDP-43 immunoreactive inclusions are observed. In AD, however, there is a unique phenomenon of neurofibrillary tangle-associated TDP-43 (TATs) whereby TDP-43 intermingles with neurofibrillary tangles. Little is known about the characteristics and distribution of TATs, or how burden and distribution of TATs compares to burden and distribution of other FTLD-TDP-like lesions observed in AD. Here we characterize molecular fragment characteristics, burden and distribution of TATs and assess how these features compare to features of other TDP-43 lesions. We performed TDP-43 immunohistochemistry with anti-phosphorylated, C- and N-terminal TDP-43 antibodies in 20 high-probability AD cases and semi-quantitative burden of seven inclusion types within five brain regions (entorhinal cortex, subiculum, CA1 and dentate gyrus of hippocampus, occipitotemporal cortex). Hierarchical cluster analysis was used to analyze the dataset that consisted of 75 different combinations of neuropathological features. TATs were nonspherical with heterogeneous staining patterns and present in all regions except hippocampal dentate. All three antibodies detected TATs although N-terminal antibody sensitivity was low. Three clusters were identified: Cluster-1 had mild-moderate TATs, moderate-frequent neuronal cytoplasmic inclusions, dystrophic neurites, neuronal intranuclear inclusions and fine neurites, and perivascular and granular inclusions identified only with the N-terminal antibody throughout the brain; Cluster-2 had scant TATs in limbic regions and Cluster-3 mild-moderate TATs and mild-moderate neuronal cytoplasmic inclusions and dystrophic neurites throughout the brain and moderate fine neurites. Only 17% of cluster 1 cases had the TMEM106b GG (protective) haplotype and 83% had hippocampal sclerosis. Both features differed across clusters (p=0.03 & p=0.01). TATs have molecular characteristics, distribution and burden, and genetic and pathologic associations like FTLD-TDP lesions.

Dysregulation of the progranulin-driven autophagy-lysosomal pathway mediates secretion of the nuclear protein TDP-43.

The cytoplasmic accumulation of the nuclear protein transactive response DNA-binding protein 43 kDa (TDP-43) has been linked to the progression of amyotrophic lateral sclerosis and frontotemporal lobar degeneration. TDP-43 secreted into the extracellular space has been suggested to contribute to the cell-to-cell spread of the cytoplasmic accumulation of TDP-43 throughout the brain; however, the underlying mechanisms remain unknown. We herein demonstrated that the secretion of TDP-43 was stimulated by the inhibition of the autophagy-lysosomal pathway driven by progranulin (PGRN), a causal protein of frontotemporal lobar degeneration. Among modulators of autophagy, only vacuolar-ATPase inhibitors, such as bafilomycin A1 (Baf), increased the levels of the full-length and cleaved forms of TDP-43 and the autophagosome marker LC3-II (microtubule-associated proteins 1A/1B light chain 3B) in extracellular vesicle fractions prepared from the culture media of HeLa, SH-SY5Y, or NSC-34 cells, whereas vacuolin-1, MG132, chloroquine, rapamycin, and serum starvation did not. The C-terminal fragment of TDP-43 was required for Baf-induced TDP-43 secretion. The Baf treatment induced the translocation of the aggregate-prone GFP-tagged C-terminal fragment of TDP-43 and mCherry-tagged LC3 to the plasma membrane. The Baf-induced secretion of TDP-43 was attenuated in autophagy-deficient ATG16L1 knockout HeLa cells. The knockdown of PGRN induced the secretion of cleaved TDP-43 in an autophagy-dependent manner in HeLa cells. The KO of PGRN in mouse embryonic fibroblasts increased the secretion of the cleaved forms of TDP-43 and LC3-II. The treatment inducing TDP-43 secretion increased the nuclear translocation of GFP-tagged transcription factor EB, a master regulator of the autophagy-lysosomal pathway in SH-SY5Y cells. These results suggest that the secretion of TDP-43 is promoted by dysregulation of the PGRN-driven autophagy-lysosomal pathway.

Cryptic exon detection and transcriptomic changes revealed in single-nuclei RNA sequencing of C9ORF72 patients spanning the ALS-FTD spectrum.

The C9ORF72-linked diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are characterized by the nuclear depletion and cytoplasmic accumulation of TAR DNA-binding protein 43 (TDP-43). Recent studies have shown that the loss of TDP-43 function leads to the inclusion of cryptic exons (CE) in several RNA transcript targets of TDP-43. Here, we show for the first time the detection of CEs in a single-nuclei RNA sequencing (snRNA-seq) dataset obtained from frontal and occipital cortices of C9ORF72 patients that phenotypically span the ALS-FTD disease spectrum. We assessed each cellular cluster for detection of recently described TDP-43-induced CEs. Transcripts containing CEs in the genes STMN2 and KALRN were detected in the frontal cortex of all C9ORF72 disease groups with the highest frequency in excitatory neurons in the C9ORF72-FTD group. Within the excitatory neurons, the cluster with the highest proportion of cells containing a CE had transcriptomic similarities to von Economo neurons, which are known to be vulnerable to TDP-43 pathology and selectively lost in C9ORF72-FTD. Differential gene expression and pathway analysis of CE-containing neurons revealed multiple dysregulated metabolic processes. Our findings reveal novel insights into the transcriptomic changes of neurons vulnerable to TDP-43 pathology.

Rare exonic variant affects GRN splicing and contributes to frontotemporal lobar degeneration.

Heterozygous loss-of-function (LOF) mutations in the progranulin gene (GRN) cause frontotemporal lobar degeneration (FTLD) by a mechanism of haploinsufficiency. For most missense mutations, the contribution to FTLD is however unclear. We studied the pathogenicity of rare GRN missense mutations using patient biomaterials. We identified a new mutation in GRN, c.1178 A>C, in a patient with a diagnosis of primary progressive aphasia. Neuropathological examination of autopsied brain showed FTLD with TAR DNA-binding protein 43 (FTLD-TDP) type A pathology with concomitant Alzheimer's disease pathology. Serum progranulin protein levels were reduced to levels comparable to known LOF mutations. The mutation is in the last codon of exon 10, in the splice donor sequence. Our data provide evidence that the mutation leads to aberrant splicing, resulting in a frameshift (p.(Glu393AlafsTer31)) and consequently nonsense-mediated mRNA decay. Our finding demonstrates that carefully examining sequencing data around splice sites is needed since this mutation was annotated as a missense mutation. Unraveling the pathogenicity of variants of unknown significance is important for clinical diagnosis and genetic counseling.

5-Hydroxytryptamine: a potential therapeutic target in amyotrophic lateral sclerosis.

Previous studies have indicated that the pathogenesis of amyotrophic lateral sclerosis (ALS) is closely linked to 5-hydroxytryptamine (5-HT). To investigate this further, we administered 5-HT receptor antagonists to SOD1*G93A transgenic (ALS mouse model) and wide-type mice. This involved intraperitoneal injections of either granisetron, piboserod, or ritanserin, which inhibit the 5-HT3, 5-HT4, and 5-HT2 receptors, respectively. The transgenic mice were found to have fewer 5-HT-positive cells in the spinal cord compared with wide-type mice. We found that the administration of granisetron reduced the body weight of the transgenic mice, while piboserod and ritanserin worsened the motor functioning, as assessed using a hanging wire test. However, none of the 5-HT receptor antagonists affected the disease progression. We analyzed the distribution and/or expression of TAR DNA binding protein 43 (TDP-43) and superoxide dismutase 1 G93A (SOD1-G93A), which form abnormal aggregates in ALS. We found that the expression of these proteins increased following the administration of all three 5-HT receptor antagonists. In addition, the disease-related mislocalization of TDP-43 to the cytoplasm increased markedly for all three drugs. In certain anatomical regions, the 5-HT receptor antagonists also led to a marked increase in the number of astrocytes and microglia and a decrease in the number of neurons. These results indicate that 5-HT deficiency may play a role in the pathogenesis of amyotrophic lateral sclerosis by inducing the abnormal expression and/or distribution of TDP-43 and SOD1-G93A and by activating glial cells. 5-HT could therefore be a potential therapeutic target for amyotrophic lateral sclerosis.

Herpes Simplex Virus 1 (HSV-1) Infected Cell Protein 0 (ICP0) Targets of Ubiquitination during Productive Infection of Primary Adult Sensory Neurons.

Herpes simplex virus 1 (HSV-1) enters sensory neurons with the potential for productive or latent infection. For either outcome, HSV-1 must curtail the intrinsic immune response, regulate viral gene expression, and remove host proteins that could restrict viral processes. Infected cell protein 0 (ICP0), a virus-encoded E3 ubiquitin ligase, supports these processes by mediating the transfer of ubiquitin to target proteins to change their location, alter their function, or induce their degradation. To identify ubiquitination targets of ICP0 during productive infection in sensory neurons, we immunoprecipitated ubiquitinated proteins from primary adult sensory neurons infected with HSV-1 KOS (wild-type), HSV-1 n212 (expressing truncated, defective ICP0), and uninfected controls using anti-ubiquitin antibody FK2 (recognizing K29, K48, K63 and monoubiquitinated proteins), followed by LC-MS/MS and comparative analyses. We identified 40 unique proteins ubiquitinated by ICP0 and 17 ubiquitinated by both ICP0 and host mechanisms, of which High Mobility Group Protein I/Y (HMG I/Y) and TAR DNA Binding Protein 43 (TDP43) were selected for further analysis. We show that ICP0 ubiquitinates HMG I/Y and TDP43, altering protein expression at specific time points during productive HSV-1 infection, demonstrating that ICP0 manipulates the sensory neuronal environment in a time-dependent manner to regulate infection outcome in neurons.

In vivo analysis of aggregation propensity of low levels of mislocalized TDP-43 on cytopathological and behavioral phenotype of ALS/FTLD.

Mislocalization and aggregate formation of TAR DNA-biding protein of 43kD (TDP-43) in the cytoplasm are signatures of amyotrophic lateral sclerosis(ALS) and frontotemporal lobar degeneration (FTLD). However, the role of two cytopathologies in ALS/FTLD pathogenesis is unclear. This study aims to elucidate the difference in their causality of TDP-43 in ALS/FTLD in vivo, using transgenic mice expressing human TDP-43 with defective nuclear localizing signals in neurons (Cyto-TDP) and those with aggregation propensity (Cyto-aggTDP). The expression levels of both proteins are less than half of endogenous TDP-43. Despite the low amount of Cyto-aggTDP, the TDP-43 phosphorylation is more evident than Cyto-TDP. Histopathological study showed accelerated astrogliosis in the anterior cerebral cortex of both mice. Cyto-aggTDP mice demonstrated significant but faint loss of neurons in the perirhinal(PERI) and ectorhinal(ECT) areas and higher Iba1-staining in the spinal cord than aged control. Despite the lack of locomotor dysfunctions in both mice, the open-field test showed enhanced exploratory behavior, indicating that the perpetual mislocalization of TDP-43 may suffice to trigger FTLD behavior. Besides, the aggregation propensity of TDP-43 promotes phosphorylation, but its role in the clinicopathological phenotype may not be primary.

MicroRNA-183-5p regulates TAR DNA-binding protein 43 neurotoxicity via SQSTM1/p62 in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that selectively attacks motor neurons, and leads to progressive muscle weakness and death. A common pathological feature is the misfolding, aggregation, and cytoplasmic mislocalization of TAR DNA-binding protein 43 (TDP-43) proteins in more than 95% of ALS patients, suggesting a universal role TDP-43 proteinopathy in ALS. Mutations in SQSTM1/p62 have been identified in familial and sporadic cases of ALS. MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally regulate their target genes. Emerging evidence indicates that miRNA dysregulation is associated with neuronal toxicity and mitochondrial dysfunction, and also plays a pivotal role in ALS pathogenesis. Here, we report the first evidence that miR-183-5p is aberrantly upregulated in spinal cords of patients with ALS. Using luciferase reporter assays and miR-183-5p agomirs, we demonstrate that miR-183-5p regulates the SQSTM1/p62 3'-untranslated region to suppress expression. A miR-183-5p agomir attenuated SOSTM1/p62 expression and led to an increase in TDP-43 protein levels in neuronal and non-neuronal cells. In contrast, a miR-183-5p antagomir decreased TDP-43 but increased SQSTM1/p62 protein levels. The antagomir repressed formation of stress granules and aggregated TDP43 protein in neuronal cells under stress-induced conditions and protected against cytotoxicity. Knockdown of SQSTM1/p62 decreased total ubiquitination and increased TDP-43 protein aggregation, indicating that SQSTM1/p62 may play a protective role in cells. In summary, our study reveals a novel mechanism of TDP-43 proteinopathy mediated by the miR-183-5p and provides a molecular link between aberrant RNA processing and protein degradation, two major pillars in ALS pathogenesis.

A candidate protective factor in amyotrophic lateral sclerosis: heterogenous nuclear ribonucleoprotein G.

Heterogenous nuclear ribonucleoprotein G is down-regulated in the spinal cord of the Tg(SOD1*G93A)1Gur (TG) amyotrophic lateral sclerosis mouse model. However, most studies have only examined heterogenous nuclear ribonucleoprotein G expression in the amyotrophic lateral sclerosis model and heterogenous nuclear ribonucleoprotein G effects in amyotrophic lateral sclerosis pathogenesis such as in apoptosis are unknown. In this study, we studied the potential mechanism of heterogenous nuclear ribonucleoprotein G in neuronal death in the spinal cord of TG and wild-type mice and examined the mechanism by which heterogenous nuclear ribonucleoprotein G induces apoptosis. Heterogenous nuclear ribonucleoprotein G in spinal cord was analyzed using immunohistochemistry and western blotting, and cell proliferation and proteins (TAR DNA binding protein 43, superoxide dismutase 1, and Bax) were detected by the Cell Counting Kit-8 and western blot analysis in heterogenous nuclear ribonucleoprotein G siRNA-transfected PC12 cells. We analyzed heterogenous nuclear ribonucleoprotein G distribution in spinal cord in the amyotrophic lateral sclerosis model at various time points and the expressions of apoptosis and proliferation-related proteins. Heterogenous nuclear ribonucleoprotein G was mainly localized in neurons. Amyotrophic lateral sclerosis mice were examined at three stages: preonset (60-70 days), onset (90-100 days) and progression (120-130 days). The number of heterogenous nuclear ribonucleoprotein G-positive cells was significantly higher in the anterior horn of the lumbar spinal cord segment of TG mice at the preonset stage than that of control group but lower than that of the control group at the onset stage. The number of heterogenous nuclear ribonucleoprotein G-positive cells in both central canal and surrounding gray matter of the whole spinal cord of TG mice at the onset stage was significantly lower than that in the control group, whereas that of the lumbar spinal cord segment of TG mice was significantly higher than that in the control group at preonset stage and significantly lower than that in the control group at the progression stage. The numbers of heterogenous nuclear ribonucleoprotein G-positive cells in the posterior horn of cervical and thoracic segments of TG mice at preonset and progression stages were significantly lower than those in the control group. The expression of heterogenous nuclear ribonucleoprotein G in the cervical spinal cord segment of TG mice was significantly higher than that in the control group at the preonset stage but significantly lower at the progression stage. The expression of heterogenous nuclear ribonucleoprotein G in the thoracic spinal cord segment of TG mice was significantly increased at the preonset stage, significantly decreased at the onset stage, and significantly increased at the progression stage compared with the control group. heterogenous nuclear ribonucleoprotein G expression in the lumbar spinal cord segment of TG mice was significantly lower than that of the control group at the progression stage. After heterogenous nuclear ribonucleoprotein G gene silencing, PC12 cell survival was lower than that of control cells. Both TAR DNA binding protein 43 and Bax expressions were significantly increased in heterogenous nuclear ribonucleoprotein G-silenced cells compared with control cells. Our study suggests that abnormal distribution and expression of heterogenous nuclear ribonucleoprotein G might play a protective effect in amyotrophic lateral sclerosis development via preventing neuronal death by reducing abnormal TAR DNA binding protein 43 generation in the spinal cord.

Dysregulated Expression of Transposable Elements in TDP-43M337V Human Motor Neurons That Recapitulate Amyotrophic Lateral Sclerosis In Vitro.

Amyotrophic lateral sclerosis (ALS) is a disease that progressively annihilates spinal cord motor neurons, causing severe motor decline and death. The disease is divided into familial and sporadic ALS. Mutations in the TAR DNA binding protein 43 (TDP-43) have been involved in the pathological emergence and progression of ALS, although the molecular mechanisms eliciting the disease are unknown. Transposable elements (TEs) and DNA sequences capable of transposing within the genome become dysregulated and transcribed in the presence of TDP-43 mutations. We performed RNA-Seq in human motor neurons (iMNs) derived from induced pluripotent stem cells (iPSCs) from TDP-43 wild-type-iMNs-TDP-43WT-and mutant-iMNs-TDP-43M337V-genotypes at 7 and 14 DIV, and, with state-of-the-art bioinformatic tools, analyzed whether TDP-43M337V alters both gene expression and TE activity. Our results show that TDP-43M337V induced global changes in the gene expression and TEs levels at all in vitro stages studied. Interestingly, many genetic pathways overlapped with that of the TEs activity, suggesting that TEs control the expression of several genes. TEs correlated with genes that played key roles in the extracellular matrix and RNA processing: all the regulatory pathways affected in ALS. Thus, the loss of TE regulation is present in TDP-43 mutations and is a critical determinant of the disease in human motor neurons. Overall, our results support the evidence that indicates TEs are critical regulatory sequences contributing to ALS neurodegeneration.

Deep learning algorithm reveals probabilities of stage-specific time to conversion in individuals with neurodegenerative disease LATE.

Introduction: Limbic-predominant age-related TAR DNA-binding protein 43 (TDP-43) encephalopathy (LATE) is a recently defined neurodegenerative disease. Currently, there is no effective way to make a prognosis of time to stage-specific future conversions at an individual level. Methods: After using the Kaplan-Meier estimation and log-rank test to confirm the heterogeneity of LATE progression, we developed a deep learning-based approach to assess the stage-specific probabilities of time to LATE conversions for different subjects. Results: Our approach could accurately estimate the disease incidence and transition to next stages: the concordance index was at least 82% and the integrated Brier score was less than 0.14. Moreover, we identified the top 10 important predictors for each disease conversion scenario to help explain the estimation results, which were clinicopathologically meaningful and most were also statistically significant. Discussion: Our study has the potential to provide individualized assessment for future time courses of LATE conversions years before their actual occurrence.

TDP-43 and NEAT long non-coding RNA: Roles in neurodegenerative disease.

Understanding and ameliorating neurodegenerative diseases represents a key challenge for supporting the health span of the aging population. Diverse protein aggregates have been implicated in such neurodegenerative disorders, including amyloid-ß, α-synuclein, tau, fused in sarcoma (FUS), and transactivation response element (TAR) DNA-binding protein 43 (TDP-43). Recent years have seen significant growth in our mechanistic knowledge of relationships between these proteins and some of the membrane-less nuclear structures that fulfill key roles in the cell function. These include the nucleolus, nuclear speckles, and paraspeckles. The ability of macromolecular protein:RNA complexes to partition these nuclear condensates through biophysical processes that involve liquid-liquid phase separation (LLPS) has also gained attention recently. The paraspeckle, which is scaffolded by the architectural long-non-coding RNA nuclear enriched abundant transcript 1 (NEAT1) plays central roles in RNA processing and metabolism and has been linked dynamically to TDP-43. In this mini-review, we outline essential early and recent insights in relation to TDP-43 proteinopathies. We then appraise the relationships between TDP-43 and NEAT1 in the context of neuronal paraspeckles and neuronal stress. We highlight key areas for investigation based on recent advances in our understanding of how TDP-43 affects neuronal function, especially in relation to messenger ribosomal nucleic acid (mRNA) splicing. Finally, we offer perspectives that should be considered for translational pipelines in order to improve health outcomes for the management of neurodegenerative diseases.

Synaptic dysfunction in ALS and FTD: anatomical and molecular changes provide insights into mechanisms of disease.

Synaptic loss is a pathological feature of all neurodegenerative diseases including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). ALS is a disease of the cortical and spinal motor neurons resulting in fatal paralysis due to denervation of muscles. FTD is a form of dementia that primarily affects brain regions controlling cognition, language and behavior. Once classified as two distinct diseases, ALS and FTD are now considered as part of a common disease spectrum based on overlapping clinical, pathological and genetic evidence. At the cellular level, aggregation of common proteins and overlapping gene susceptibilities are shared in both ALS and FTD. Despite the convergence of these two fields of research, the underlying disease mechanisms remain elusive. However, recent discovers from ALS and FTD patient studies and models of ALS/FTD strongly suggests that synaptic dysfunction is an early event in the disease process and a unifying hallmark of these diseases. This review provides a summary of the reported anatomical and cellular changes that occur in cortical and spinal motor neurons in ALS and FTD tissues and models of disease. We also highlight studies that identify changes in the proteome and transcriptome of ALS and FTD models and provide a conceptual overview of the processes that contribute to synaptic dysfunction in these diseases. Due to space limitations and the vast number of publications in the ALS and FTD fields, many articles have not been discussed in this review. As such, this review focuses on the three most common shared mutations in ALS and FTD, the hexanucleuotide repeat expansion within intron 1 of chromosome 9 open reading frame 72 (C9ORF72), transactive response DNA binding protein 43 (TARDBP or TDP-43) and fused in sarcoma (FUS), with the intention of highlighting common pathways that promote synaptic dysfunction in the ALS-FTD disease spectrum.