Acta Neuropathologica Communications最新文献

It is currently understood that the characteristic loss of the repressive histone mark H3K27me3 in PFA ependymoma and diffuse midline glioma (DMG) are caused by complementary mechanisms mediated by EZHIP and the oncohistone H3K27M, respectively. To support the complementarity of these mechanisms, rare H3K27M-negative DMGs express EZHIP. Interestingly, EZHIP is one of the few genes recurrently mutated in PFA. The significance of EZHIP mutations in PFA, and whether EZHIP has wider functions in addition to repression of H3K27me3 deposition, are not known. Here, we investigated the mutational landscape of EZHIP in pediatric brain tumors. We found that EZHIP mutations occur not only in PFA, but also in rare medulloblastoma and pediatric high-grade glioma (HGG), including in H3K27-positive DMG. Contrary to current expectations, we show that mutant EZHIP is expressed in H3K27M-positive DMG. All the EZHIP-mutated HGG cases also have EGFR mutations. Further, we pursued better understanding of the function of EZHIP by expressing it in human-derived neural models. Our transcriptomic analyses indicate that EZHIP expression potentiates neuronal-like gene programs associated with synaptic function. Metabolomics data indicate that EZHIP leads to repression of methionine and polyamine metabolism, suggesting links between metabolic and epigenetic changes that are observed in PFA. Collectively, our results expand the repertoire of tumor types known to harbor EZHIP mutations and shed light on EZHIP-dependent metabolic and transcriptional programs in relevant neural models.

α-Synuclein seed amplification assays are a promising diagnostic tool for synucleinopathies such as Parkinson's disease and multiple system atrophy. Standardized conditions are required to ensure a high degree of inter- and intra-laboratory reproducibility when performing these assays. A significant issue that hinders the utility of seed amplification assays is the de novo aggregation propensity of the α-synuclein substrate as well as inter-batch heterogeneity. While much work has focused on determining appropriate seed amplification assay buffer compositions as well as the type and amount of seed used, a robust comparison of α-synuclein substrate purification methods has not been reported. We therefore compared the utility of recombinant α-synuclein purified using four different methods as seed amplification assay substrates across two laboratories. Osmotic shock-purified α-synuclein monomer substrate showed the lowest propensity for de novo aggregation, which translated into being the best substrate for seed amplification assay reactions seeded with α-synuclein preformed fibrils or patient brain homogenates. Furthermore, osmotic shock α-synuclein monomer showed the best inter-batch reproducibility compared to all other substrates tested. As α-synuclein seed amplification assays continue to evolve and move towards adoption in the clinical realm, this work showcases the vital importance of standardizing the production and characterization of recombinant α-synuclein substrate. We encourage the widespread adoption of osmotic shock α-synuclein monomer as the universal substrate for seed amplification assays to maximize intra- and inter-laboratory reproducibility.

Alzheimer's Disease (AD) is marked by the accumulation of pathology, neuronal loss, and gliosis and frequently accompanied by decline in cognition. Understanding brain cell interactions is key to identifying new therapeutic targets to slow its progression. Here, we used systems biology methods to analyze single-nucleus RNA sequencing (snRNASeq) data generated from dorsolateral prefrontal cortex (DLPFC) tissues of 424 participants in the Religious Orders Study or the Rush Memory and Aging Project (ROSMAP). We identified modules of co-regulated genes in seven major cell types and assigned them to coherent cellular processes. We showed that coexpression structure was conserved in the majority of modules across cell types, but we also found distinct communities with altered connectivity, especially when compared to bulk RNASeq, suggesting cell-specific gene co-regulation. These coexpression modules can also capture signatures of cell subpopulations and be influenced by cell proportions. Finally, we performed associations of modules with AD traits such as amyloid-β deposition, tangle density, and cognitive decline, and showed replications in an independent single-nucleus dataset. Using a Bayesian network framework, we modeled the direction of relationships between the modules and AD progression. We highlight one key module, the astrocytic module 19 (ast_M19), associated with cognitive decline through a subpopulation of stress-response cells. Our work provides cell-specific molecular networks modeling the molecular events leading to AD.

Parkinson's disease (PD) progression involves dopaminergic neurodegeneration and pathological α-synuclein aggregation, processes linked to metabolic dysregulation and autophagy-lysosomal pathway (ALP) impairment. Transaldolase1 (TAL1) is a key enzyme of the pentose phosphate pathway. While elevated TAL1 protein levels have been observed in postmortem substantia nigra of PD patients, the enzyme's functional role in disease pathogenesis remains undefined. In this study, we explored the role of TAL1 in PD-related pathologies using MPTP-induced and AAV-A53T mouse models. We demonstrate that TAL1 upregulation is associated with dopaminergic neuron degeneration across both experimental models. TAL1 knockdown activated TFEB-mediated transcription of autophagy-lysosomal genes (Ctsb, Ctsd, Lamp1, Becn1, and Map1Lc3b). In addition, targeted metabolomics revealed that TAL1 knockdown modulates the energy pathways, especially in the TCA cycle, and glycolysis. The neuroprotective effects were mediated through AMPK/mTORC1 pathway activation, evidenced by increased AMP levels, p-AMPK/AMPK ratios, and downstream ALP enhancement. Importantly, TAL1 inhibition improved locomotor function in AAV-A53T mice and normalized stride length in footprint analysis. Pathological experiments confirmed reduced phospho-α-synuclein level and preserved the neuron loss in substantia nigra. Our findings highlight TAL1 as a regulator of autophagy-lysosomal function and energy metabolism in PD-related experimental models, where its inhibition restores the degradation of α-synuclein through coordinated activation of autophagy-lysosomal clearance and energetic reprogramming. These results suggest that targeting TAL1 may offer a potential therapeutic approach to mitigate PD-associated neuropathology.

Extracranial metastasis of IDH-wildtype glioblastoma is very rare and poorly understood at the molecular level. We report a case of FGFR3::TACC3 fusion IDH-wildtype glioblastoma in a 61-year-old male, whose preoperative blood sample showed highly aberrant cfDNA fragmentation patterns, which could be suggestive of early systemic dissemination, undetected by standard-of-care imaging of his body. Eleven months post-resection and adjuvant therapy, he developed widespread extracranial metastases. Comprehensive molecular profiling of matched primary and metastatic tumors revealed broadly conserved genomic, transcriptomic, and copy number landscapes, with the metastasis harboring an additional ERCC6 deletion and enriched expression of receptor tyrosine kinase signaling genes. These findings provide rare insight into the genetic continuity and evolution underlying IDH-wildtype glioblastoma metastasis.

Atypical teratoid rhabdoid tumors (AT/RT) are characterized by a poor prognosis and a manifestation within the first 2 years of life. Genetic hallmark of these tumors is the homozygous inactivation of SMARCB1 or, in some rare cases, of SMARCA4. While heterozygous pathogenic variants of SMARCA4 have been described, inter alia, in the context of other CNS malignancies such as medulloblastoma or glioblastoma, the co-occurrence of pathogenic variants in both, SMARCB1 and SMARCA4, in the same AT/RT has to our knowledge not been reported previously. Liquid biopsy, a rapidly developing and promising technique measuring cell-free DNA (cfDNA) in body fluids such as the cerebrospinal fluid (CSF), offers a minimally invasive method to assess disease status. It has yet to be established as a standard procedure in the diagnostic workup of CNS tumors. We present the case of a three-year-old male diagnosed with an AT/RT that exhibits both biallelic alterations of SMARCB1 due to a frameshift mutation and loss of heterozygosity as well as a heterozygous missense variant in SMARCA4 presenting with early disease progression. We employed liquid biopsy successfully to monitor disease progression throughout treatment and the subsequent relapse. We highlight the ramifications that simultaneous alterations in two chromatin-modifying genes may have for tumor biology and clinical course.

Macrophages are crucial for neuroinflammatory responses following traumatic brain injury (TBI), encompassing various subtypes, such as border-associated macrophages (BAMs) that contribute to both brain damage and repair. However, the pathophysiological relevance of subtype-specific molecular markers is poorly understood. This study investigated the role of the BAM marker mannose receptor C-type 1 (MRC1, also known as CD206) during the early phase of TBI using controlled cortical impact (CCI). MRC1 gene expression was up-regulated, peaking between 3 to 7 days post-injury (dpi), and MRC1 protein expression predominantly localized to BAMs. To assess pathophysiological relevance, MRC1-deficient (MRC1-KO) and wild-type littermates (MRC1-WT) were examined following CCI for early neurological deficits, brain structural damage, intracerebral hematoma, and neuroinflammatory marker expression. At 5 dpi, MRC1-KO mice showed increased brain lesion volume and hippocampal neuron loss, with minor differences in neurological deficits compared to MRC1-WT mice. Intracerebral hematoma size increased in male but remained unchanged in female MRC1-KO mice. Immunostaining revealed no genotype-specific effects on GFAP⁺ astrocytes, while the number of perilesional CD68⁺ macrophages/microglia were reduced in MRC1-KO mice. Analysis of neuroinflammatory gene markers revealed an overall reduction in MRC1-KO mice. Sex-specific regulation was observed for the M2-like macrophage/microglia marker Arg1, with decreased expression in male and increased expression in female MRC1-KO compared to MRC1-WT mice. In conclusion, lack of MRC1 exacerbated brain tissue damage following experimental TBI. Reduced CD68+ macrophages/microglia and neuroinflammatory marker expression suggests impaired neuroinflammatory response in MRC1-KO, indicating MRC1 expression on BAMs contributes to beneficial early neuroinflammatory response following TBI.

Soluble tau oligomeric assemblies display neurotoxic properties and may provide a pathogenic link between neurofibrillary tangle evolution and selective neuronal vulnerability in Alzheimer's disease (AD). However, the precise molecular and cellular pathways mediating tau oligomer toxicity are unclear. We combined single-neuron laser capture microdissection with custom microarrays to investigate differences in the molecular signatures of basal forebrain neurons within the nucleus basalis of Meynert (nbM) labeled for p75^NTR, a cholinergic cell marker, or dual-labeled for p75^NTR and TOC1, a tau oligomer marker. Tissue was obtained postmortem from Rush Religious Orders Study participants who died with an antemortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI), or mild/moderate AD. Using clinical diagnosis as a covariate to isolate tau oligomer-specific mechanisms, we identified 140 differentially expressed genes (DEGs) in p75^NTR + /TOC1 + cholinergic nbM neurons compared to p75^NTR + /TOC1- neurons. STRING interactome and pathway analysis revealed that downregulated genes were associated with pre- and postsynaptic function, with additional enrichment in glutamate and acetylcholine signaling. By contrast, upregulated genes related to cellular stress responses and apoptosis were clustered with a subset of downregulated DEGs regulating mitochondrial metabolism and redox function, indicative of bioenergetic failure. Weighted gene co-expression correlation network analysis of the entire dataset revealed only two significantly correlated modules, which were either negatively correlated with the presence of TOC1 and enriched for synaptic signaling or positively correlated with TOC1 and enriched for cellular responses to hypoxia. These data show with single-neuron resolution that oligomeric tau formation in vulnerable cholinergic nbM neurons, even prior to MCI, is associated with the dysregulation of multiple classes of genes driving cell/mitochondrial stress and synaptic imbalances, which may be amenable for disease-modifying therapeutic approaches.