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Although SARS-CoV-2 primarily targets the respiratory system, patients with and survivors of COVID-19 can suffer neurological symptoms 1 – 3 . However, an unbiased understanding of the cellular and molecular processes that are affected in the brains of patients with COVID-19 is missing. Here we profile 65,309 single-nucleus transcriptomes from 30 frontal cortex and choroid plexus samples across 14 control individuals (including 1 patient with terminal influenza) and 8 patients with COVID-19. Although our systematic analysis yields no molecular traces of SARS-CoV-2 in the brain, we observe broad cellular perturbations indicating that barrier cells of the choroid plexus sense and relay peripheral inflammation into the brain and show that peripheral T cells infiltrate the parenchyma. We discover microglia and astrocyte subpopulations associated with COVID-19 that share features with pathological cell states that have previously been reported in human neurodegenerative disease 4 – 6 . Synaptic signalling of upper-layer excitatory neurons—which are evolutionarily expanded in humans 7 and linked to cognitive function 8 —is preferentially affected in COVID-19. Across cell types, perturbations associated with COVID-19 overlap with those found in chronic brain disorders and reside in genetic variants associated with cognition, schizophrenia and depression. Our findings and public dataset provide a molecular framework to understand current observations of COVID-19-related neurological disease, and any such disease that may emerge at a later date. Single-nucleus transcriptomes of frontal cortex and choroid plexus samples from patients with COVID-19 reveal pathological cell states that are similar to those associated with human neurodegenerative diseases and chronic brain disorders.

The neurovascular unit is critical for brain health, and its dysfunction has been linked to Alzheimer's disease (AD). However, a cell-type-resolved understanding of how diverse vascular cells become dysfunctional and contribute to disease has been missing. Here, we applied Vessel Isolation and Nuclei Extraction for Sequencing (VINE-seq) to build a comprehensive transcriptomic atlas from 101 individuals along AD progression. Our analysis of over 842,646 parenchymal and vascular nuclei reveals that vascular dysfunction in AD is driven by transcriptional changes rather than shifts in cell proportions, with brain endothelial cells (BECs) and smooth muscle cells (SMCs) most affected. Strikingly, these molecular signatures emerge early at the mild cognitive impairment (MCI) stage, implicating vascular dysfunction early in AD pathogenesis. Stratifying by pathology reveals distinct vascular responses to β-amyloid and tau: β-amyloid burden primarily perturbs BECs and SMCs, while tau pathology predominantly impacts glial cells. We identify dysregulated angiopoietin signaling across multiple vascular cell types as a key axis, with antagonistic ANGPT2 in vascular cells and ANGPT1 in astrocytes becoming progressively dysregulated with AD. Together, this work provides a foundational resource that reveals early and pathology-specific pathways of vascular dysfunction in AD.

Lithium (Li) is an established effective treatment for bipolar disorder. However, the molecular mechanism of its action is still unknown. Dehydroepiandrosterone (DHEA) and its sulphate ester (DHEA-S) are adrenal hormones also synthesized de novo in the brain as neurosteroids. Recent studies have suggested that DHEA has mood-elevating properties and may demonstrate antidepressant effects. 3′(2′)-Phosphoadenosine 5′-phosphate (PAP) phosphatase is a novel Li-inhibitable enzyme involved in sulphation processes. In the present study we examined the impact of 10 d Li treatment on serum and brain DHEA and DHEA-S levels in rats. Our results show that Li administration lowered frontal cortex and hippocampus DHEA and DHEA-S levels, in line with our hypothesis assuming that Li's inhibition of PAP phosphatase leads to elevated PAP levels resulting in inhibition of sulphation and reduction in brain DHEA-S levels. Future studies should address the involvement of neurosteroids in the mechanism of Li's mood stabilization.

Variants in cause Gaucher disease (GD), a lysosomal storage disorder, and represent the most common genetic risk factor for Parkinson's disease (PD). While some variants are associated with both GD and PD, several coding mutations, including E326K, specifically confer risk for developing PD. It is established that GD-linked variants in β-glucocerebrosidase (GCase), the enzyme encoded by , are loss-of-function, but it remains unclear whether variants solely associated with PD similarly reduce GCase activity. The mechanisms by which some of these variants impact GCase activity and PD-associated pathways, including lysosomal and mitochondrial function, are also poorly defined. Here, we show that the PD-linked E326K variant significantly reduces lysosomal GCase activity by impairing its delivery to lysosomes via altered interactions with its receptor, LIMP2. Biophysical and structural characterization of this variant, both alone and in complex with LIMP2, reveals a dimeric organization that appears to result from the loss of a key salt bridge between E326 and R329. Restoration of this salt bridge through the introduction of a negatively charged side chain at position 329 promotes monomeric organization and interaction with LIMP2 in cells. -p.E326K cell models show greater deficits in PD-linked pathways compared to more severe loss of GCase function, including secondary lysosomal lipid storage and mitochondrial dysfunction. We confirm the E326K variant impacts GCase pathway activity in relevant CNS cell types, including iPSC-derived microglia, and in biofluids from heterozygous p.E326K variant carriers. Together, our data provide key insights into the nature of GCase dysfunction in -PD and can inform the development of GCase-targeted therapeutic strategies to treat PD.