Acta Neuropathologica Communications

Aggregation and cytoplasmic mislocalization of TDP-43 are key features of several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Neuroinflammatory processes mediated by glial cells play crucial roles in the pathophysiology of these and other diseases, defined as TDP-43 proteinopathies. Here, we characterized region-specific glial activation in two conditional mouse models: hTDP-43-WT (overexpressing nuclear wild-type human TDP-43) and hTDP-43-{Delta}NLS (expressing cytoplasmic TDP-43 with altered nuclear localization signal) following one month of transgene expression. Immunofluorescence analysis revealed distinct patterns of microglial activation across brain regions. hTDP-43-WT mice exhibited significant microgliosis in motor (MC) and somatosensory (SSC) cortices and hippocampal dentate gyrus (DG) with pronounced morphological alterations (i.e. increased soma size). Sholl analysis demonstrated reduced branching length and complexity in MC, SSC and hippocampal subfields. hTDP-43-{Delta}NLS mice displayed more pronounced microglial activation in hippocampal regions (CA1, DG) compared to cortical areas, with significant increases in microglial density. Additionally, we observed region-specific cortical astrocytosis in both models, suggesting coordinated glial reactivity. hTDP-43-{Delta}NLS mice showed decreased polarization of astrocytic water channel Aquaporin-4 (AQP4) around vascular structures in SSC and hippocampal CA1/DG. The changes in AQP4 localization, which is critical for glymphatic function, supports the hypothesis that this waste clearance system for the brain is altered in TDP-43 proteinopathies. These findings demonstrate that these different animal models of ALS/FTD induce distinct neuroinflammatory signatures, potentially contributing to the region-specific vulnerability observed in these diseases. Our data provide insights into early glial-mediated pathogenic mechanisms that could guide targeted therapeutic strategies for TDP-43 proteinopathies.

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by the degeneration of upper and lower motor neurons. A major neuropathological finding in ALS is the coexistence of glial activation and aggregation of the phosphorylated transactive response DNA-binding protein 43-kDa (pTDP43) in the motor cortex at the earliest stages of the disease. Despite this, the transcriptional alterations associated with these pathological changes in this major vulnerable brain region have yet to be fully characterized. Here, we have performed massive RNA sequencing of the motor cortex of ALS (n=11) and healthy controls (HC; n=8). We report extensive RNA expression alterations at gene and isoform levels, characterized by the enrichment of neuroinflammatory and synapse related pathways. The assembly of gene co-expression modules confirmed the involvement of these two principal transcriptomic changes, and showed a strong negative correlation between them. Furthermore, cell-type deconvolution using human single-nucleus RNA sequencing data as reference demonstrated that microglial cells are overrepresented in ALS compared to HC. Importantly, we also show for the first time in the human ALS motor cortex, that microgliosis is mostly driven by the increased proportion of a microglial subpopulation characterized by gene markers overlapping with the recently described disease associated microglia (DAM). Using immunohistochemistry, we further evidenced that this microglial subpopulation is overrepresented in ALS and that variability in pTDP43 aggregation among patients negatively correlates with the proportion of microglial cells. In conclusion, we report that neuroinflammatory changes in ALS motor cortex are dominated by microglia which is concomitant with a reduced expression of postsynaptic transcripts, in which DAM might have a prominent role. Microgliosis therefore represents a promising avenue for therapeutic intervention in ALS.

The transgenic SOD1G93A mouse model is the most widely used animal model of amyotrophic lateral sclerosis (ALS), a fatal disease of motor neuron degeneration. While genetic background influences onset and progression variability of motor dysfunction, the C57BL/6 background most reliably exhibits robust ALS phenotypes; thus, it is the most widely used strain in mechanistic studies. In this model, paresis begins in the hindlimbs and spreads rostrally to the forelimbs. Males experience earlier onset, greater disease severity, and shorter survival than females. However, the influence of sex on patterns of declining motor function between forelimbs and hindlimbs as well as among distinct, spinal-innervated muscle groups within each limb are not fully understood. To provide a higher resolution framework of degenerating motor function across the body, we conducted more comprehensive, limb-dependent and independent measures of motor decline over the course of disease. Subsequently, we compared the timing and intensity of these features across sex, and we consider to what extent these patterns are conserved in clinical observations from human ALS patients. We found male mice experienced earlier and less localized onset than females. We also report distinct motor features decline at different rates between sexes. Finally, mice showed differences in correlation between the decline of left- and right-side measures of the hindlimb. Consequently, our findings reinforce and refine the utility of the SOD1 mouse in modeling more highly resolved, sex-specific differences in ALS patient motor behavior. This may better guide preclinical studies in stratifying patients by sex and anatomical site of onset.

Neuronal intranuclear inclusion disease (NIID) is a polyglycine disease that primarily affects the neuronal and neuromuscular systems. Here, we developed a novel transgenic mouse model that faithfully recapitulates the multisystemic impairments associated with polyG intranuclear inclusions. Our findings demonstrate that polyG expression induces neurodegeneration, behavioral deficits, and age-dependent accumulation of uN2CpolyG aggregates across multiple tissues.

Frontotemporal dementia (FTD) is a neurodegenerative disorder with a strong heritable component. Frontotemporal lobar degeneration (FTLD) refers to the pathological changes seen in FTD, characterised by atrophy of the frontal and temporal lobes and the presence of abnormal protein inclusions. In the case of FTLD with hyperphosphorylated TDP-43 positive inclusions (FTLD-TDP), five pathological subtypes (A, B, C, D, and E) are observed based on the types and distribution of inclusions found in the brain. In all subtypes, there tends to be a large variability in the number of pathological inclusions observed between cases, with limited correlation to clinical manifestations. TDP-43 is an RNA binding protein belonging to the heterogeneous nuclear ribonucleoprotein (hnRNP) family which along with other hnRNPs modulates multiple aspects of RNA processing. HnRNPs other than TDP-43 have been implicated in several neurological diseases, including ALS, FTLD-TDP, FTLD-FUS and Alzheimers disease. Multiple hnRNPs have been found in pathological inclusions in specific subtypes of FTLD-TDP, suggesting potential roles in the disease process. The role of the hnRNP network in FTLD disease pathogenesis, however, has not yet been investigated. This study aimed to comprehensively evaluate the presence and expression of hnRNP proteins in two pathological subtypes of sporadic FTLD-TDP (A and C) as well as the genetic form FTLD-TDP A C9orf72 using immunohistochemistry and gene expression analysis by single-nuclei RNA-sequencing. We found that there was great variability in frequency of TDP-43 pathology across and within FTLD-TDP pathological subtypes. Finally, our findings suggest that distinct global transcriptomic profiles may underlie the different pathological subtypes of FTLD-TDP. The most prominent transcriptomic changes were observed in oligodendrocytes and astrocytes, involving multiple hnRNPs across FTLD subtypes compared to controls. Transcriptomic co-expression analysis further revealed that glial clusters were more strongly associated with RNA processing dysfunction and contribute to disease classification. Together, these findings highlight the involvement of the hnRNP network and glial-specific RNA processing alterations in FTLD-TDP pathophysiology, offering new insight into the molecular distinctions between pathological subtypes and potential targets for future investigation.

Regional heterogeneity of neurons and glia is a key feature of the brain, yet the effect of disease on heterogeneity and its relationship with selective neuronal vulnerability remains poorly understood. Using region-specific RNA sequencing, we identified a large number of differentially expressed genes (DEGs) across distinct regions of the cerebellar cortex, supporting the notable intrinsic regional transcriptional heterogeneity of the healthy cerebellum. Further, we used fiber photometry to identify regional physiological differences in the activity of Purkinje cells (PCs) during self-motivated, unrestrained walking and non-walking states. In the inherited cerebellar neurodegenerative disease Spinocerebellar ataxia type 1 (SCA1), patients exhibit preferential degeneration of the posterior cerebellum, suggesting regionally selective vulnerability. We demonstrated that in a mouse model of SCA1 the Purkinje cells and glia residing in the posterior vermis of cerebellum also undergo earlier and more severe pathology. Intriguingly, the intrinsic transcriptional heterogeneity of anterior and posterior cerebellum seen in healthy mice was diminished in SCA1 mice. This disruption was also demonstrated via fiber photometry, where we found notable impacts in PC activity in the posterior cerebellum as well as loss of regional differences in PC activity during self-motivated, unrestrained walking, and non-walking states in SCA1 mice. Our findings indicate regionally distinct mechanisms of pathogenesis across cerebellar regions that result in reduced intracerebellar heterogeneity.

DNA damage and DNA damage repair (DDR) dysfunction are insults with broad implications on cellular physiology, including in proteostasis, and have been recently implicated in many neurodegenerative diseases. Alpha-synuclein (aSyn), a pre-synaptic and nuclear protein associated with neurodegenerative disorders known as synucleinopathies, has been implicated in DNA double strand break (DSB) repair function. Consistently, DSB induction has been demonstrated in cell and animal models of synucleinopathy. Nevertheless, the types of DNA damage and the contribution of DNA damage towards Lewy body (LB) formation in synucleinopathies are unknown. Here, we demonstrate the increase of DSB in neuronal and non-neuronal cellular populations of post-mortem temporal cortex tissue from dementia with Lewy body (DLB) patients and demonstrate increases in DSBs early at a presymptomatic age of aSyn transgenic mice. Strikingly, in postmortem DLB tissue, DNA damage-derived ectopic cytoplasmic genomic material (eCGM) was evident within the majority of LBs examined. The observed cellular pathology was consistent with nucleoproteasomal upregulation of associated DNA damage repair proteins, particularly in base excision repair and DSB repair pathways. Collectively our study demonstrates the early occurrence of DNA damage and associated nucleoproteasomal changes in response to nuclear aSyn pathology. Furthermore, the data suggests a potential involvement for DNA damage derived eCGM for the facilitation of cytoplasmic aSyn aggregates. Ultimately, uncovering pathological mechanisms underlying DNA damage in DLB sheds light into novel disease mechanisms and opens novel possibilities for diagnosing and treating synucleinopathies.

The appearance of misfolded and aggregated proteins is a pathological hallmark of numerous neurodegenerative diseases including Alzheimers disease and Parkinsons disease. Sleep disruption is proposed to contribute to these pathological processes and is a common early feature among neurodegenerative disorders. Synucleinopathies are a subclass of neurodegenerative conditions defined by the presence of -synuclein aggregates, which may not only enhance cell death, but also contribute to disease progression by seeding the formation of additional aggregates in neighboring cells. The mechanisms driving intercellular transmission of aggregates remains unclear. We propose that disruption of sleep-active glymphatic function, caused by loss of precise perivascular AQP4 localization, inhibits -synuclein clearance and facilitates -synuclein propagation and seeding. We examined human post-mortem frontal cortex and found that neocortical -synuclein pathology was associated with AQP4 mis-localization throughout the gray matter. Using a transgenic mouse model lacking the adapter protein -syntrophin, we observed that loss of perivascular AQP4 localization impairs the glymphatic clearance of -synuclein from intersititial to cerebrospinal fluid. Using a mouse model of -synuclein propogation, using pre-formed fibril injection, we observed that loss of perivascular AQP4 localization increased -synuclein aggregates. Our results indicate -synuclein clearance and propagation are mediated by glymphatic function and that AQP4 mis-localization observed in the presence of human synucleinopathy may contribute to the development and propagation of Lewy body pathology in conditions such as Lewy Body Dementia and Parkinsons disease. SummaryIn a human postmortem case series, we observe that neocortical Lewy body pathology is associated with mis-localization of the astroglial water channel aquaporin-4 (AQP4). In mice, -synuclein is cleared from the brain along perivascular pathways, while loss of perivascular AQP4 localization impairs glymphatic -synuclein clearance to the CSF. Furthermore, loss of perivascular AQP4 localization promotes the development and propagation of -synuclein aggregates.

Sporadic cases of Amyotrophic Lateral Sclerosis (sALS) represent the most common form of motor neuron disease. sALS is characterised by pathological cytoplasmic inclusions of TDP-43, so-called reactive astrocyte pathology, and motor neuron degeneration. Early-stage alterations in certain subpopulations of synapses between neurons are thought to be a key driver of the early pathological mechanisms of ALS. However, we do not have a clear understanding of which types of synapses are impacted in ALS. Identifying vulnerable synapses affected in sALS models may provide insights into the key sites of disease pathogenesis. In this study we have performed quantitative high-resolution microscopy to survey different synapse subtypes, including excitatory (glutamatergic), inhibitory (glycinergic) and modulatory (cholinergic C-Bouton) synapses, in the spinal cord of a mouse model of sALS showing inducible TDP-43 pathology (TDP43{Delta}NLS) restricted to neurons. We have identified changes in cholinergic synapses and a subpopulation of excitatory synapses. Mice display robust neuronal TDP-43 pathology and evidence of TDP-43 changes at cholinergic C-boutons. We also observe no evidence of astrocytic pathology nor changes in the fraction of synapses that are contacted by astrocytes, demonstrating that synapse pathology is driven by cell-autonomous (neuronal) mechanisms. Overall, our findings highlight the selective vulnerability of distinct synapse populations in ALS.

Repeat expansion diseases, particularly those involving GC-rich motifs, have been increasingly recognized as contributors to neurological and neuromuscular disorders. Amyotrophic lateral sclerosis (ALS) has been linked to several such expansions, including intermediate-length repeats in genes implicated in oculopharyngodistal myopathy (OPDM). To investigate the possible involvement of CGG repeat expansions in ALS, 424 ALS patients and 312 controls of Japanese descent were screened for expansions in five genes associated with repeat expansion disorders, namely GIPC1, RILPL1, FMR1, AFF2, and NUTM2BAS1. Repeat-primed PCR and fragment analysis revealed that four ALS patients exhibited abnormal CGG expansions in GIPC1 (33-55 repeats), whereas two control individuals harbored expanded alleles (67 and 83 repeats). No expansions in the other genes were detected. Long-read sequencing confirmed repeat sizes and showed sequence instability. Histopathological analysis of ALS patients with GIPC1 expansion demonstrated classical ALS pathology, including phosphorylated TDP-43-positive inclusions. RNA fluorescence in situ hybridization revealed nuclear foci containing GIPC1 repeat RNA exclusively in ALS patients with GIPC1 expansions, suggesting RNA-mediated toxicity. These findings indicate that a subset of ALS patients present with intermediate CGG expansions in GIPC1, which may represent a novel pathogenic mechanism analogous to other noncoding repeat disorders. Given that GIPC1 full expansions are associated with OPDM, these results support the hypothesis of a pathological continuum between neurodegeneration and myopathy driven by repeat length and sequence context. Nonetheless, further investigations into the potential of GIPC1 CGG expansions as genetic risk factors or modifiers in ALS are warranted.

Human postmortem brain tissues provide an indispensable resource that is crucial for the understanding of neurological conditions, whether related to pathology subtype, burden, distribution or cell-type specificity. Pathology staging protocols provide guidelines for standardized sampling of brain tissues, but cover only a subset of regions affected by pathologies. Thus, to study how various neuropathologies and cell types in highly specialized circuit nodes correlate with functions specifically served by these nodes, additional protocols are necessary. This especially applies to brainstem tissues due to the small dimension of regions of interest and interindividual variability of specimens, whether due to procurement or intrinsic differences. Here we systematically assessed factors contributing to heterogeneity in the length of whole brainstem samples and then presented a standardized approach to reproducibly assign rostrocaudal levels, with standardization relying upon readily identifiable internal landmarks. We validated this approach using postmortem MRI imaging. Standardized brainstem length correlated positively with subject height and negatively with subject age of death. By providing a reference series, reproducible levels can be assigned to individual histological sections or MRI images, i.e. when full brainstem specimens are not available and irrespective of platform, promoting reproducibility.

Cerebral small vessel disease (SVD) is associated with white matter hyperintensities (WMHs), thereby contributing to vascular dementia and movement disorder. However, the pathomechanisms responsible for WMH-related small vessel degeneration remain poorly understood due to the technical limitations of current methods. The aim of this study was to clarify the 2- and 3-dimensional (2D and 3D) pathological features of small vessels and white matter (WM) in the brains of patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), HTRA1-autosomal dominant disease (HTRA1-AD) and sporadic SVD (sSVD). From a cohort of 86 consecutive autopsied patients with SVDs, we retrieved those with genetically confirmed CADASIL and HTRA1-AD (three and three, respectively), and four with sSVD. We quantitatively evaluated WM and vascular changes in the frontal portion of the centrum semiovale and temporal lobe using conventional 2D and chemically cleared 3D analytical methods with light-sheet fluorescence microscopy. Quantitatively, the WM pathology, including the density of myelin, axons and gliosis, was most severe in CADASIL, but unexpectedly sSVD was second in order of severity, followed by HTRA1-AD. The density of clasmatodendrocytes, known to be irreversibly injured astrocytes, was considerably highest in HTRA1-AD. The vascular pathology, including arteriole and capillary sclerosis and the extent of the perivascular space, was most severe in CADASIL, whereas the density of smooth muscle actin (SMA) positivity was most decreased in HTRA1-AD. 3D immunohistochemistry for SMA demonstrated two distinct patterns of SMA loss within the vessels: (1) CADASIL and sSVD: diffuse loss, being prominent in small branches, (2) HTRA1-AD: selective loss in main branches. Overall, the extent of WM and vascular degeneration is most severe in CADASIL, whereas SMA loss is most evident in HTRA1-AD. These differences in the size and distribution of affected vessels may be related to the heterogeneous WM pathology and underlying pathomechanisms of SVD.

Cerebral amyloid angiopathy (CAA) is a vasculopathy characterized by vascular {beta}-amyloid (A{beta}) deposition on cerebral blood vessels. CAA is closely linked to Alzheimers disease (AD) and intracerebral hemorrhage. CAA is associated with the loss of autoregulation in the brain, vascular rupture, and cognitive decline. To assess morphological and molecular changes associated with the degeneration of penetrating arterioles in CAA, we analyzed post-mortem human brain tissue from 26 patients with mild, moderate, and severe CAA end neurological controls. The tissue was optically cleared for three-dimensional light sheet microscopy, and morphological features were quantified using surface volume rendering. We stained A{beta}, vascular smooth muscle (VSM), lysyl oxidase (LOX), and vascular markers to visualize the relationship between degenerative morphological features, including vascular dilation, dolichoectasia (variability in lumenal diameter) and tortuosity, and the volumes of VSM, A{beta}, and LOX in arterioles. Atomic force microscopy (AFM) was used to assess arteriolar wall stiffness, and we identified a pattern of morphological features associated with degenerating arterioles in the cortex. The volume of VSM associated with the arteriole was reduced by around 80% in arterioles with severe CAA and around 60% in cases with mild/moderate CAA. This loss of VSM correlated with increased arteriolar diameter and variability of diameter, suggesting VSM loss contributes to arteriolar laxity. These vascular morphological features correlated strongly with A{beta} deposits. At sites of microhemorrhage, A{beta} was consistently present, although the morphology of the deposits changed from the typical organized ring shape to sharply contoured shards with marked dilation of the vessel. AFM showed that arteriolar walls with CAA were more than 400% stiffer than those without CAA. Finally, we characterized the association of vascular degeneration with LOX, finding strong associations with VSM loss and vascular degeneration. These results show an association between vascular A{beta} deposition, microvascular degeneration, and increased vascular stiffness, likely due to the combined effects of replacement of VSM by {beta}-amyloid, cross-linking of extracellular matrices (ECM) by LOX, and possibly fibrosis. This advanced microscopic imaging study clarifies the association between A{beta} deposition and vascular fragility. Restoration of physiologic ECM properties in penetrating arteries may yield a novel therapeutic strategy for CAA.

Mutations in the UBQLN2 gene cause amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The neuropathology of such UBQLN2-linked cases of ALS/FTD is characterised by aggregates of the ubiquilin 2 protein in addition to aggregates of the transactive response DNA-binding protein of 43 kDa (TDP-43). ALS and FTD without UBQLN2 mutations are also characterised by TDP-43 aggregates, that may or may not colocalise with wildtype ubiquilin 2. Despite this, the relative contributions of TDP-43 and ubiquilin 2 to disease pathogenesis remain largely under-characterised, as does their relative deposition as aggregates across the central nervous system (CNS). Here we conducted multiplex immunohistochemistry of three UBQLN2 p.T487I-linked ALS/FTD cases, three non-UBQLN2-linked (sporadic) ALS cases, and eight non-neurodegenerative disease controls, covering 40 CNS regions. We then quantified ubiquilin 2 aggregates, TDP-43 aggregates, and aggregates containing both proteins in regions of interest to determine how UBQLN2-linked and non-UBQLN2-linked proteinopathy differ. We find that ubiquilin 2 aggregates that are negative for TDP-43 are predominantly small and punctate, and are abundant in the hippocampal formation, spinal cord, all tested regions of neocortex, medulla, and substantia nigra in UBQLN2-linked ALS/FTD but not sporadic ALS. Curiously, the striatum harboured small punctate ubiquilin 2 aggregates in all cases examined, while large diffuse striatal ubiquilin 2 aggregates were specific to UBQLN2-linked ALS/FTD. Overall, ubiquilin 2 is mainly deposited in clinically unaffected regions throughout the CNS such that symptomology in UBQLN2-linked cases maps best to the aggregation of TDP-43.

Altered energy metabolism in Alzheimers disease (AD) is considered a major pathological hallmark implicated in the early stages of the disease process. Astrocytes play a central role in brain homeostasis and are increasingly implicated in multiple neurodegenerative diseases. We report that astrocytes differentiated from early onset familial Alzheimers disease (fAD) patients or control cells treated with Amyloid {beta} oligomers exhibit significant changes in their metabolism including glucose uptake, glutamate uptake and lactate release, with increases in oxidative and glycolytic metabolism. Furthermore, we demonstrate evidence of gliosis in fAD astrocytes in addition to a change in metabolic pathways including glutamate, purines, arginine, and the citric acid cycle. Homeostatic responses to brain activity and cellular metabolism are central to normal brain function. However, altered brain metabolism and cellular stress present significant risk factors for the onset and progression of neurodegenerative disease. This study demonstrates that fAD derived astrocytes present multiple metabolic and disease associated phenotypes early in their development suggesting that chronic alterations in fAD patient early in life that present significant risk factors for disease progression in mid-life and suggest key targets for potential diagnostic features and therapeutic agents late onset dementia in midlife.

Dementia with Lewy bodies is pathologically defined by the cytoplasmic accumulation of alpha-synuclein within neuronal cells in the brain. Alpha-synuclein is predominately pre-synaptic, but has been reported present in various subcellular compartments in cell and animal models. In particular, nuclear alpha-synuclein is evident in-vitro and in disease models and has been associated with altered DNA integrity, gene transcription, nuclear homeostasis. However, owing to various factors, the presence of alpha-synuclein in the nuclei of human brain cells remains controversial, as does its role in synucleinopathies. Here, we close this gap and provide a unique demonstration confirming the presence of nuclear alpha-synuclein in post-mortem brain tissue obtained from cases of dementia with Lewy bodies as well as from controls via immunohistochemistry, immunoblot, and label-free mass-spectrometry. Discrete intra-nuclear alpha-synuclein puncta reactive against phosphorylated serine 129-alpha-synuclein and pan-alpha-synuclein antibodies were observed in cortical neurons and non-neuronal cells in fixed brain sections and in isolated nuclear preparations from Dementia with Lewy bodies cases and matched controls. Subsequent biochemical analysis of subcellular fractionated tissue confirmed alpha-synuclein as present in a nuclear fraction at levels ~ 10-fold lower than in the cytoplasm. Critically, however, an increase in monomeric nuclear alpha-synuclein phosphorylated as serine 129 was observed in cases of dementia with Lewy bodies alongside higher molecular weight pan- and phosphorylation reactive alpha-synuclein species, consistent with the formation of intranuclear phosphorylated alpha-synuclein oligomers. Furthermore, the presence of nuclear alpha-synuclein was confirmed via label free mass spectrometry, as 6 unique alpha-synuclein derived peptide sequences were identified in nuclear fractions (71.4% sequence coverage). Collectively, our data confirm the presence of nuclear alpha-synuclein in human brain tissue and describe nuclear pathology associated with dementia with Lewy bodies. These findings address a major controversy in the synucleinopathy field by confirming the presence of nuclear alpha-synuclein in autoptic human brain tissue and, for the first time, identify that alpha-synuclein is aggregated into novel and potentially pathological assemblies in the nucleus as part of the disease process associated with dementia with Lewy bodies and thus may contribute to the disease phenotype.

Dominantly inherited mutation D395G in the gene encoding valosin-containing protein causes vacuolar tauopathy, a type of behavioural-variant frontotemporal dementia, with marked vacuolation and abundant filamentous tau inclusions made of all six brain isoforms. Here we report that tau inclusions were concentrated in layers II/III of the frontotemporal cortex in a case of vacuolar tauopathy. By electron cryo-microscopy, tau filaments had the chronic traumatic encephalopathy (CTE) fold. Tau inclusions of vacuolar tauopathy share this cortical location and the tau fold with CTE, subacute sclerosing panencephalitis and amyotrophic lateral sclerosis/parkinsonism-dementia complex, which are believed to be environmentally induced. Vacuolar tauopathy is the first inherited disease with the CTE tau fold.

Spinal ependymoma (SP-EPN) is a central nervous system (CNS) tumor that is associated with high morbidity. The only effective treatment for end-stage SP-EPN is surgery, but this is associated with high risk of injury to the sensorimotor spinal tracts and paralysis. There is a critical need to understand the cellular origins of this tumor so that disease models of tumor progression can be generated for drug development. Recent genomic studies with bulkRNA sequencing suggest the molecular signature of SP-EPN matches that of ependymal cells (EPCs). However, large-scale genomic studies can often misrepresent rare cancer stem cell populations within the tumor. In this study, we performed spatial transcriptomics (ST) on a SP-EPN resected from a patient with NF2-related neurofibromatosis to examine the spatial heterogeneity within the tumor. The SP-EPN sample exhibited cellular heterogeneity with diffuse expression of astrocytic and EPC markers, and smaller pockets with RGC or stem cell markers, as well as overlap between progenitor cell and mature cell markers. These findings suggest that there may be a developmental hierarchy within the EPC lineage in SP-EPN tumors, which may stem from aberrant radial glia cells.

BackgroundPolyglutamine (polyQ) tract expansion mutations in Ataxin-2 gene (ATXN2) are associated with neurodegenerative diseases spinocerebellar ataxia type 2 (SCA2) and amyotrophic lateral sclerosis (ALS), while the therapeutic reduction of ATXN2 confers strong health-/lifespan extension in models of both disorders. Although the involvement of ATXN2 in peripheral lipid metabolism has been elaborated in Atxn2 knock-out mice, its impact on nervous system lipid maintenance and a potential influence on oligodendrocytes remains unexplored. MethodsWe examine the nervous tissue of an authentic ATXN2 polyQ expansion mouse model in terms of (i) gross morphology of the brain and differential glial affection via immunohistochemical analyses, (ii) spinocerebellar proteome profile via label-free mass spectroscopy and (iii) alternative splicing patterns of oligodendroglial transcripts via quantitative RT-PCR. Finally, electrophysiological recording of sensory response in cerebellar Purkinje cells was performed as a phenotypic measure of demyelination. ResultsWe demonstrate a massive impairment in myelin maintenance due to ATXN2 polyQ expansion, affecting key oligodendroglial proteins accompanied by their splicing anomalies much earlier than disease manifestation. Oligodendroglial ATXN2 aggregates were documented for the first time in cerebellum, which sequestrated the RNA splicing factor Quaking (QKI). As an outcome of demyelination, our SCA2 model showed a significant delay in response to sensory stimuli. ConclusionsOverall, we provide pioneer evidence of oligodendroglial proteotoxicity leading to myelin maintenance defects in an authentic mouse model of SCA2. Our findings suggest that not only neuronal metabolism, but also that of oligodendroglia depends on ATXN2 and is affected during the disease course. This novel aspect of ATXN2 pathomechanism sheds light on potential outcomes of its therapeutic manipulation, and makes it relevant also for demyelination syndromes next to SCA2 and other polyQ disorders.

Spinocerebellar ataxia type 1 (SCA1) and Huntingtons disease (HD), are motor diseases caused by CAG expansions in ATXN1 and HTT, where SCA1 shows prominent cerebellar neurodegeneration and HD shows prominent striatal neurodegeneration, particularly in the Medium Spiny Neurons (MSNs). Since human and mouse studies demonstrate progressive striatal vulnerability in SCA1, we examined age-dependent molecular, cellular and functional striatal attributes in SCA1 (f-ATXN1146Q/2Q) knockin mice, by assessing RNA-sequencing, immunohistochemistry and electrophysiology. Striatal mRNAs are downregulated in SCA1 mice, many in common with HD mice, and specificity in MSNs is supported by the rescue of transcriptomic dysregulation with deletion of mutant Ataxin1 from MSNs. Immunohistochemistry assessed dopamine receptor 1 (D1R) and 2 (D2R) expression in indirect and direct MSNs. In HD mice (HttQ175/Q7), expression of both D1R and D2R proteins in MSNs decreased with age in parallel with their RNA levels. In the SCA1 mouse striatum, D1R protein expression decreased with age as seen in murine HD striatum. In contrast, while D2R protein level was decreased similar to D1R protein at 5-weeks of age, by 40-weeks expression of D2R protein recovered to levels recorded in WT mice. Electrophysiological assessment showed a reduction of excitatory synaptic transmission in SCA1 mouse MSNs, indicating functional deficits early in disease. In contrast to cerebellar and many other aspects of SCA1 pathology known to depend on proper nuclear localization of ATXN1 with an expanded polyglutamine, mutating ATXN1s nuclear localization failed to correct striatal MSN RNA and protein downregulations, indicating a difference in how ATXN1 exerts its pathological effects between the cerebellum and the striatum. Together, these data provide a molecular and cellular basis of striatal pathology in SCA1.