Amyotrophic lateral sclerosis (ALS) is a movement disorder lacking effective diagnostics and therapeutics, largely due to its clinical and etiological heterogeneity. The unifying hallmark of TDP-43 pathology is found in approximately 97

Ubiquilin 2, encoded by the X-linked UBQLN2 gene, is a ubiquitin-binding quality control protein. Pathogenic UBQLN2 genetic variants cause X-linked dominant amyotrophic lateral sclerosis and/or frontotemporal dementia (ALS/FTD), however, clinical phenotypes from these variants show striking inter- and intra-familial heterogeneity. Further, there are many UBQLN2 variants whose significance to disease is uncertain. Here, we examine the pathogenic potential of UBQLN2 variants reported in individuals with ALS/FTD and their non-symptomatic relatives. Meta-analysis from 27 published studies identified 186 affected individuals and 51 asymptomatic carriers, each harbouring one of 43 unique UBQLN2 coding variants. Features of identified variants, including evolutionary conservation, minor allele frequencies, localisation to protein domains, and in silico predictions of pathogenicity were compiled. Per biological sex, clinical features were compared between UBQLN2 variants segregated by pathogenicity. Pathogenic UBQLN2 variant carriers, most of whom are familial ALS cases, showed a sex-specific difference in age at onset wherein males developed disease on average 18.15 years prior to females (29.54 ± 11.9 versus 47.69 ± 13.4 years, p < 0.0001), with no change in disease duration (p = 0.2091). UBQLN2 variants of uncertain significance showed a bimodal distribution of onset age per sex suggesting a mixture of true benign and true pathogenic variants. In human brain tissue, two male UBQLN2 p.Thr487Ile (ALS-FTD and ALS) cases showed a greater burden of ubiquilin 2 aggregates than a related female case (ALS-FTD). These robust sex-specific differences in ALS/FTD presentation in carriers of pathogenic UBQLN2 variants may improve predictions of ALS/FTD risk in carriers, aiding in diagnosis and disease management.

Microglia are the innate immune cells of the brain with the capacity to react to damage or disease. Microglial reactions can be characterised in post-mortem tissues by assessing their pattern of protein expression, or immunophenotypes, and cell morphologies. We recently demonstrated that microglia have a phagocytic immunophenotype in early-stage ALS but transition to a dysfunctional immunophenotype by end stage, and that these states are driven by TAR DNA-binding protein 43 (TDP-43) aggregation in the human brain. However, it remains unclear how microglial morphologies are changed in ALS. Here we examine the relationship between microglial immunophenotypes and morphologies, and TDP-43 pathology in motor cortex tissue from people with ALS and from a TDP-43-driven ALS mouse model. Post-mortem human brain tissue from 10 control and 10 ALS cases was analysed alongside brain tissue from the bigenic NEFH-tTA/tetO-hTDP-43∆NLS (rNLS) mouse model of ALS at distinct disease stages. Sections were immunohistochemically labelled for microglial markers (HLA-DR, CD68, and Iba1) and phosphorylated TDP-43 (pTDP-43). Single-cell microglial HLA-DR, CD68, and Iba1 average intensities, and morphological features (cell body area, process number, total outgrowth, and branch number) were measured using custom image analysis pipelines. In human ALS motor cortex, we identified a significant change in microglial morphologies from ramified to hypertrophic, which was associated with increased Iba1 and CD68 levels. In the rNLS mouse motor cortex, the microglial morphologies changed from ramified to hypertrophic and increased Iba1 levels occurred in parallel with pTDP-43 aggregation, prior to increases in CD68 levels. Overall, the evidence presented in this study demonstrates that microglia change their morphologies prior to immunophenotype changes. These morphological changes may prime microglia near neurons with pTDP-43 aggregation for phagocytosis, in turn triggering immunophenotype changes; first, to a phagocytic state then to a dysfunctional one.

Huntington’s disease (HD) is a hereditary neurodegenerative condition caused by a CAG repeat expansion mutation in the gene encoding the huntingtin (HTT) protein. The accumulation of HTT inclusion bodies is a pathological hallmark of HD and a common target for therapeutic strategies. However, the limited efficacy of treatments targeting the HTT protein highlights the need for a better understanding of the role of HTT inclusion bodies in HD pathogenesis. This study examined the heterogeneity of HTT inclusion body composition by co-labelling with three HTT epitope-specific antibodies to characterize HTT inclusion body ‘immunophenotype’. We then characterized the size and sub-cellular location of HTT inclusions with distinct immunophenotypes. Using multiplex immunohistochemistry, we also examined the ubiquitination profile of each immunophenotype. Our findings demonstrate that HTT inclusions have a range of immunophenotypes, with some labelled by only one of the three antibodies and others exhibiting co-labelling by several antibodies, thus demonstrating the heterogeneity in inclusion composition and structure. We outline evidence that inclusion bodies exclusively labelled with the EM48 antibody are small, non-nuclear, and more abundant in HD cases with increased CAG repeat length, higher Vonsattel grade, and earlier age of onset. We also find that HTT inclusion bodies labelled by multiple antibodies are more likely to be ubiquitinated, predominantly by K63- rather than K48-linked ubiquitin, suggesting preferential degradation by autophagy. Lastly, we show that ubiquitinated HTT inclusion bodies are more highly immunoreactive for ubiquilin 2 than p62. Our findings highlight the need for multiple antibodies to capture the full spectrum of HTT pathology in HD and imply that future studies should consider the diversity of inclusion body composition and structure when correlating pathology formation to neurodegeneration, clinical symptoms, or disease severity.

Huntington's disease (HD) is a neurodegenerative disorder that severely affects the basal ganglia and regions of the cerebral cortex. While astrocytosis and microgliosis both contribute to basal ganglia pathology, the contribution of gliosis and potential factors driving glial activity in the human HD cerebral cortex is less understood. Our study aims to identify nuanced indicators of gliosis in HD which is challenging to identify in the severely degenerated basal ganglia, by investigating the middle temporal gyrus (MTG), a cortical region previously documented to demonstrate milder neuronal loss. Immunohistochemistry was conducted on MTG paraffin-embedded tissue microarrays (TMAs) comprising 29 HD and 35 neurologically normal cases to compare the immunoreactivity patterns of key astrocytic proteins (glial fibrillary acidic protein, GFAP; inwardly rectifying potassium channel 4.1, Kir4.1; glutamate transporter-1, GLT-1; aquaporin-4, AQP4), key microglial proteins (ionised calcium-binding adapter molecule-1, IBA-1; human leukocyte antigen (HLA)-DR; transmembrane protein 119, TMEM119; purinergic receptor P2RY12, P2RY12), and indicators of proliferation (Ki-67; proliferative cell nuclear antigen, PCNA). Our findings demonstrate an upregulation of GFAP+ protein expression attributed to the presence of more GFAP+ expressing cells in HD, which correlated with greater cortical mutant huntingtin (mHTT) deposition. In contrast, Kir4.1, GLT-1, and AQP4 immunoreactivity levels were unchanged in HD. We also demonstrate an increased number of IBA-1+ and TMEM119+ microglia with somal enlargement. IBA-1+, TMEM119+, and P2RY12+ reactive microglia immunophenotypes were also identified in HD, evidenced by the presence of rod-shaped, hypertrophic, and dystrophic microglia. In HD cases, IBA-1+ cells contained either Ki-67 or PCNA, whereas GFAP+ astrocytes were devoid of proliferative nuclei. These findings suggest cortical microgliosis may be driven by proliferation in HD, supporting the hypothesis of microglial proliferation as a feature of HD pathophysiology. In contrast, astrocytes in HD demonstrate an altered GFAP expression profile that is associated with the degree of mHTT deposition.

Low-density cosmic voids gravitationally lens the cosmic microwave background (CMB), leaving a negative imprint on the CMB convergence kappa. This effect provides insight into the distribution of matter within voids, and can also be used to study the growth of structure. We measure this lensing imprint by cross-correlating the Planck CMB lensing convergence map with voids identified in the Dark Energy Survey Year 3 (DES Y3) data set, covering approximately 4200 deg(2) of the sky. We use two distinct void-finding algorithms: a 2D void-finder that operates on the projected galaxy density field in thin redshift shells, and a new code, Voxel, which operates on the full 3D map of galaxy positions. We employ an optimal matched filtering method for cross-correlation, using the Marenostrum Institut de Ciencies ` de l'Espai N-body simulation both to establish the template for the matched filter and to calibrate detection significances. Using the DES Y3 photometric luminous red galaxy sample, we measure A(kappa) , the amplitude of the observed lensing signal relative to the simulation template, obtaining A(kappa) = 1.03 +/- 0.22 (4.6 sigma significance) for Voxel and A(kappa) = 1.02 +/- 0.17 (5.9 sigma significance) for 2D voids, both consistent with Lambda cold dark matter expectations. We additionally invert the 2D void-finding process to identify superclusters in the projected density field, for which we measure A(kappa) = 0.87 +/- 0.15 (5.9 sigma significance). The leading source of noise in our measurements is Planck noise, implying that data from the Atacama Cosmology Telescope, South Pole Telescope and CMB-S4 will increase sensitivity and allow for more precise measurements.

We engineered a novel human iPSC-derived organoid system enriched with mature, myelinating oligodendrocytes and functionally reactive microglia. This model enables the study of human CNS remyelination following a demyelinating insult, encapsulating: myelin fragmentation, microglial clearance of myelin debris and oligodendrocyte genesis, differentiation, and axon ensheathment. This system provides a powerful and unparalleled capacity to interrogate complex human cell behaviour, relevant to those studying glial biology and neurological disease mechanisms.### Competing Interest StatementThe authors have declared no competing interest.

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.

Pathogenic variants in the UBQLN2 gene cause X-linked dominant amyotrophic lateral sclerosis and/or frontotemporal dementia characterized by ubiquilin 2 aggregates in neurons of the motor cortex, hippocampus and spinal cord. However, ubiquilin 2 neuropathology is also seen in sporadic and familial amyotrophic lateral sclerosis and/or frontotemporal dementia cases not caused by UBQLN2 pathogenic variants, particularly C9orf72-linked cases. This makes the mechanistic role of mutant ubiquilin 2 protein and the value of ubiquilin 2 pathology for predicting genotype unclear. Here we examine a cohort of 44 genotypically diverse amyotrophic lateral sclerosis cases with or without frontotemporal dementia, including eight cases with UBQLN2 variants [resulting in p.S222G, p.P497H, p.P506S, p.T487I (two cases) and p.P497L (three cases)].Using multiplexed (five-label) fluorescent immunohistochemistry, we mapped the co-localization of ubiquilin 2 with phosphorylated TDP-43, dipeptide repeat aggregates and p62 in the hippocampus of controls (n = 6), or amyotrophic lateral sclerosis with or without frontotemporal dementia in sporadic (n = 20), unknown familial (n = 3), SOD1-linked (n = 1), FUS-linked (n = 1), C9orf72-linked (n = 5) and UBQLN2-linked (n = 8) cases.We differentiate between (i) ubiquilin 2 aggregation together with phosphorylated TDP-43 or dipeptide repeat proteins; and (ii) ubiquilin 2 self-aggregation promoted by UBQLN2 pathogenic variants that cause amyotrophic lateral sclerosis and/or frontotemporal dementia. Overall, we describe a hippocampal protein aggregation signature that fully distinguishes mutant from wild-type ubiquilin 2 in amyotrophic lateral sclerosis with or without frontotemporal dementia, whereby mutant ubiquilin 2 is more prone than wild-type to aggregate independently of driving factors.This neuropathological signature can be used to assess the pathogenicity of UBQLN2 gene variants and to understand the mechanisms of UBQLN2-linked disease. Mutations in UBQLN2 cause X-linked dominant ALS and/or FTD marked by the presence of ubiquilin 2 aggregates. However, ubiquilin 2 neuropathology is also seen in ALS/FTD cases unrelated to UBQLN2 mutations. Thumbadoo et al. identify a distinct signature of ubiquilin 2 clumping specific to cases of ALS/FTD caused by ubiquilin 2 mutations.

Microglia, the innate immune cells of the brain, are activated by damage or disease. In mouse models of amyotrophic lateral sclerosis (ALS), microglia shift from neurotrophic to neurotoxic states with disease progression. It remains unclear how human microglia change relative to the TAR DNA-binding protein 43 (TDP-43) aggregation that occurs in 97% of ALS cases. Here we examine spatial relationships between microglial activation and TDP-43 pathology in brain tissue from people with ALS and from a TDP-43-driven ALS mouse model. Post-mortem human brain tissue from the Neurological Foundation Human Brain Bank was obtained from 10 control and 10 ALS cases in parallel with brain tissue from a bigenic NEFH-tTA/tetO-hTDP-43∆NLS (rNLS) mouse model of ALS at disease onset, early disease, and late disease stages. The spatiotemporal relationship between microglial activation and ALS pathology was determined by investigating microglial functional marker expression in brain regions with low and high TDP-43 burden at end-stage human disease: hippocampus and motor cortex, respectively. Sections were immunohistochemically labelled with a two-round multiplexed antibody panel against; microglial functional markers (L-ferritin, HLA-DR, CD74, CD68, and Iba1), a neuronal marker, an astrocyte marker, and pathological phosphorylated TDP-43 (pTDP-43). Single-cell levels of microglial functional markers were quantified using custom analysis pipelines and mapped to anatomical regions and ALS pathology. We identified a significant increase in microglial Iba1 and CD68 expression in the human ALS motor cortex, with microglial CD68 being significantly correlated with pTDP-43 pathology load. We also identified two subpopulations of microglia enriched in the ALS motor cortex that were defined by high L-ferritin expression. A similar pattern of microglial changes was observed in the rNLS mouse, with an increase first in CD68 and then in L-ferritin expression, with both occurring only after pTDP-43 inclusions were detectable. Our data strongly suggest that microglia are phagocytic at early-stage ALS but transition to a dysfunctional state at end-stage disease, and that these functional states are driven by pTDP-43 aggregation. Overall, these findings enhance our understanding of microglial phenotypes and function in ALS.

Abstract BACKGROUND Glioblastoma tumours are highly vascular and angiogenic. However, they are also heterogeneous, comprising many different macro- and microenvironments. Reflecting this, tumour-associated blood vessels are variable in their distribution, structure, and function. Despite the significance of vasculature in the development and progression of glioblastoma, its complexity remains poorly defined. Therefore, characterising vascular diversity across the glioblastoma landscape is a crucial step in the development of targeted therapies. METHODS 40 glioblastoma and 5 epilepsy cases were immunohistochemically labelled with a vascular antibody panel (PDGFRβ, ColIV, αSMA, UEA-1 and GFAP) to identify and subtype vessels. Single-vessel image analysis was performed to analyse vascular coverage and to classify vascular subtypes based on marker co-expression. Labelling with haemoglobin, ZO-1, and claudin-5 allowed for the evaluation of vascular leakage and blood-brain barrier integrity. Tissue segmentation was performed to analyse vascular coverage, vascular subtypes, and vascular integrity across the tumour macro-environment. RESULTS No significant difference in gross vascular coverage was found between tumour and epilepsy tissue. However, vascular coverage within glioblastoma varied significantly depending on the tumour macro-environment. Whilst vascular coverage in the tumour periphery was comparable to epilepsy tissue, increased vessel density was observed in the intermediate tumour zone, followed by decreased vessel density towards the tumour core. Reflecting this variation, multiple vessel subtypes, including previously described glomerular microvascular proliferation, mother vessels, vascular malformations and hyperplastic vessels, were identified. These tumour vessels display highly irregular shapes, sizes, and cellular compositions. Finally, glioblastoma tissue displayed a significant increase in haemoglobin leakage and a decrease in vascular integrity compared to epilepsy tissue. CONCLUSION Characterising this vascular landscape provides valuable insights for treatment strategies related to hypoxia and angiogenesis, two key factors driving tumour growth. Indeed, targeting specific vessel subtypes to address compromised vascular function and aberrant vascularisation may improve outcomes for glioblastoma patients.

Abstract Background Glioblastoma (GBM) is the most common and aggressive primary brain tumor in adults. Whilst the role of the efflux transporters are well established in GBM, the expression and function of uptake transporters, such as the organic anion transporting polypeptide (OATP) family, are not well understood. OATPs possess broad substrate specificity that includes anti-cancer agents; therefore, we sought to investigate the expression of four OATP isoforms in human GBM cell types using patient tumor tissue. Methods We used fluorescent immunohistochemical labeling of paraffin-embedded surgically resected tissues and single-cell image analysis methods to explore the expression of the OATP isoforms in different tumor cell types through co-labeling with cell-type specific markers, such as IBA1 (pan-myeloid), GFAP (tumor cell), PDGFRβ (stromal cell), and UEA-1-lectin (endothelial). Results We found significant over-expression of all the OATP isoforms (OATP1A2, 2B1, 1C1 and 4A1) in GBM tumor sections when compared to non-neoplastic brain. A single-cell image analysis revealed that OATPs were significantly upregulated throughout the tumor parenchyma, with significantly higher expression found on lectin-positive blood vessels and IBA1-positive myeloid cells in GBM compared to non-tumor brain tissue. Qualitative analysis of the four OATP isoforms demonstrated greater expression of OATP4A1 in peri-necrotic regions of GBM tissue, which correlated with hypoxia-related markers within the Ivy GAP RNAseq dataset. Conclusion Here, we demonstrate, for the first time, the protein expression of four OATPs in human GBM tissue, including upregulation within the tumor microenvironment by myeloid cells and tumor vasculature, and isoform-specific upregulation within hypoxic niches.

Mutations in the UBQLN2 gene cause X-linked dominant amyotrophic lateral sclerosis (ALS) and/or frontotemporal dementia (FTD) characterised by ubiquilin 2 aggregates in neurons of the motor cortex, hippocampus, and spinal cord. However, ubiquilin 2 neuropathology is also seen in sporadic and familial ALS or FTD cases not caused by UBQLN2 mutations, particularly C9orf72 -linked cases. This makes the mechanistic role of ubiquilin 2 mutations and the value of ubiquilin 2 pathology for predicting genotype unclear. Here we examine a cohort of 41 genotypically diverse ALS cases with or without FTD, including five cases with UBQLN2 variants (resulting in p.S222G, p.P497H, p.P506S, and two cases with p.T487I). Using multiplexed (5-label) fluorescent immunohistochemistry, we mapped the co-localisation of ubiquilin 2 with phosphorylated TDP-43 (pTDP-43), dipeptide repeat aggregates, and p62, in the hippocampus of controls (n=5), or ALS with or without FTD in sporadic (n=20), unknown familial (n=3), SOD1 -linked (n=1), FUS -linked (n=1), C9orf72 -linked (n=5), and UBQLN2 -linked (n=5) cases. We differentiate between i) ubiquilin 2 aggregation together with pTDP-43 or dipeptide repeat proteins, and ii) ubiquilin 2 self-aggregation promoted by UBQLN2 gene mutations that cause ALS/FTD. Overall, we describe a hippocampal protein aggregation signature that fully distinguishes mutant from wildtype ubiquilin 2 in ALS with or without FTD, whereby mutant ubiquilin 2 is more prone than wildtype to aggregate independently of driving factors. This neuropathological signature can be used to assess the pathogenicity of UBQLN2 gene variants and to understand the mechanisms of UBQLN2 -linked disease.

Abstract Background Microglia and bone marrow-derived macrophages (BMDMs) are two ontogenetically distinct myeloid populations present within glioblastoma that can comprise 30-50% of the tumour mass. Historically, these cell types have been conflated and studied as a single population of ‘tumour-associated macrophages’. Recent advances in single-cell omics have allowed population delineation, suggesting microglia and BMDMs may play different roles within the tumour and subsequently differentially affect tumour progression. Despite building evidence for the unique functions of these cells within glioblastoma, the inherent heterogeneity of the tumour landscape has complicated such studies. Indeed, macrophages exist as phenotypically and functionally diverse populations that are polarised in a context-dependent manner. Hence, to understand the differences between microglia and BMDMs within glioblastoma, both ontogeny and spatial location must be considered. Material and Methods To elucidate the functional roles of microglia and BMDMs across the tumour landscape, a publicly available RNAseq dataset was utilised to classify myeloid cells into four populations based on spatial location and ontogeny. These were tumour core BMDMs and microglia, or tumour periphery BMDMs and microglia. Differential gene analysis was then performed to identify significant differentially expressed genes (DEGs) between classified myeloid populations. Tumour core DEGs were then compared against the Ivy Glioblastoma Atlas to define their expression across anatomical tumour regions. Finally, myeloid DEGs were validated at the protein level on human glioblastoma tissue through immunohistochemistry. Results Microglia and BMDMs showed different spatial distributions across the tumour landscape and displayed distinct functional expression profiles. Microglia held a more chemotactic and pro-inflammatory profile, whereas BMDMs held a more pro-tumoural profile. However, a comparison of microglia between the tumour core and periphery revealed that tumour microglia upregulate many pro-tumoural genes, including multiple genes that have previously been defined as ‘BMDM-enriched’. Moreover, we found myeloid DEGs identified within the tumour core cluster to distinct spatial tumour regions such as the vascular or hypoxic niche. Immunohistochemical staining reflected these spatial expression profiles, identifying a distinct population of phagocytic macrophages within the hypoxic niche. Conclusion Although microglia and BMDMs represent two ontogenetically distinct myeloid populations within glioblastoma, both cell types can adopt similar functional expression profiles within the tumour core, particularly within tumour niches. This indicates that myeloid cell function is strongly influenced by the tumour microenvironment, rather than ontogeny alone.

On 2019 August 14 at 21:10:39 UTC, the LIGO/Virgo Collaboration (LVC) detected a possible neutron star–black hole merger (NSBH), the first ever identified. An extensive search for an optical counterpart of this event, designated GW190814, was undertaken using the Dark Energy Camera on the 4 m Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory. Target of Opportunity interrupts were issued on eight separate nights to observe 11 candidates using the 4.1 m Southern Astrophysical Research (SOAR) telescope’s Goodman High Throughput Spectrograph in order to assess whether any of these transients was likely to be an optical counterpart of the possible NSBH merger. Here, we describe the process of observing with SOAR, the analysis of our spectra, our spectroscopic typing methodology, and our resultant conclusion that none of the candidates corresponded to the gravitational wave merger event but were all instead other transients. Finally, we describe the lessons learned from this effort. Application of these lessons will be critical for a successful community spectroscopic follow-up program for LVC observing run 4 (O4) and beyond.

Our understanding of amyotrophic lateral sclerosis and frontotemporal dementia has advanced dramatically since the discovery of cytoplasmic TAR DNA-binding protein 43 (TDP-43) inclusions as the hallmark pathology of these neurodegenerative diseases. Recent studies have provided insights into the physiological function of TDP-43 as an essential DNA-/RNA-modulating protein, and the triggers and consequences of TDP-43 dysfunction and aggregation. The formation of TDP-43 pathology is a progressive process, involving the generation of multiple distinct protein species, each with varying biophysical properties and roles in neurodegeneration. Here, we explore how the pathogenic changes to TDP-43, including mislocalisation, misfolding, aberrant liquid-liquid phase separation, stress granule assembly, oligomerisation, and post-translational modification, drive disease-associated aggregation in TDP-43 proteinopathies. We highlight how pathological TDP-43 species are formed and contribute to cellular dysfunction and toxicity, via both loss-of-function and gain-of-function mechanisms. We also review the role of protein homeostasis mechanisms, namely the ubiquitin proteasome system, autophagy-lysosome pathway, heat-shock response, and chaperone-mediated autophagy, in combating TDP-43 aggregation and discuss how their dysfunction likely promotes disease pathogenesis and progression. Finally, we evaluate pre-clinical studies aimed at enhancing TDP-43 protein clearance via these mechanisms and provide insight on promising strategies for future therapeutic advances. Harnessing the mechanisms that protect against or ameliorate TDP-43 pathology presents promising opportunities for developing disease-modifying treatments for these neurodegenerative diseases.

Binary supermassive black holes (BSBHs) are expected to be a generic byproduct from hierarchical galaxy formation. The final coalescence of BSBHs is thought to be the loudest gravitational wave (GW) siren, yet no confirmed BSBH is known in the GW-dominated regime. While periodic quasars have been proposed as BSBH candidates, the physical origin of the periodicity has been largely uncertain. Here, we report discovery of a periodicity (p = 1607 +/- 7 d) at 99.95 per cent significance (with a global p value of similar to 10(-3) accounting for the look elsewhere effect) in the optical light curves of a redshift 1.53 quasar, SDSS J025214.67-002813.7. Combining archival Sloan Digital Sky Survey data with new, sensitive imaging from the Dark Energy Survey, the total similar to 20-yr time baseline spans similar to 4.6 cycles of the observed 4.4-yr (rest frame 1.7-yr) periodicity. The light curves are best fit by a bursty model predicted by hydrodynamic simulations of circumbinary accretion discs. The periodicity is likely caused by accretion rate modulation by a milli-parsec BSBH emitting GWs, dynamically coupled to the circumbinary accretion disc. A bursty hydrodynamic variability model is statistically preferred over a smooth, sinusoidal model expected from relativistic Doppler boost, a kinematic effect proposed for PG1302-102. Furthermore, the frequency dependence of the variability amplitudes disfavours Doppler boost, lending independent support to the circumbinary accretion variability hypothesis. Given our detection rate of one BSBH candidate from circumbinary accretion variability out of 625 quasars, it suggests that future large, sensitive synoptic surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time may be able to detect hundreds to thousands of candidate BSBHs from circumbinary accretion with direct implications for Laser Interferometer Space Antenna.