Ca2+-sensitive Mef2c protein interactions and chromatin function in microglia-like cells

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder for which there are no disease-modifying therapies. Genetic studies have identified over 50 susceptibility loci for sporadic AD including the locus encoding the transcription factor MEF2C. Most of the genes implicated in AD-risk are exclusively or preferentially expressed in microglia. Furthermore, AD-risk variants are enriched in microglial open chromatin regions that contain DNA binding motifs for MEF2C. Therefore, genetic variants that disrupt MEF2C binding to DNA in microglia may alter cis-gene expression, contributing to AD-risk. Understanding how MEF2C functions in microglia may provide valuable insights into the genetic basis of AD-risk. To investigate the role of Mef2c in AD, mass spectrometry was used to identify proteins that co-purify with the endogenous protein in BV2 microglia-like cells. Two major Mef2c isoforms exist in BV2 cells that associate with 110 putative interactors including the transcriptional repressors, Hdac4, Hdac5, and Cabin1. Ionomycin treatment, that raises intracellular [Ca2+], caused the partial dissociation of these repressors from Mef2c and resulted in recruitment of the microglial amyloid-β response proteins, Yes1 and Smpdl3b to the Mef2c complex. However, no Mef2c-activating proteins were identified in the remodelled complex. Having demonstrated that ionomycin treatment remodels the Mef2c interactome, the effect of this treatment on chromatin accessibility in BV2 cells was investigated using ATAC-seq. This revealed that while the motifs for three transcription factors, Atf4, NFATC3 and p53, were enriched at Ca2+ -dependent differentially accessible sites, Mef2c sites were not similarly enriched. However, Mef2c motif-containing differentially accessible regions were associated with genes that control the microglial inflammatory response. This thesis investigated two mechanisms by which [Ca2+] levels potentially influence gene regulation; altered protein interactions and chromatin accessibility and further contributes to our understanding of the transcription factor Mef2c, Ca2+ signalling, and chromatin function in BV2 cells. In conclusion, Ca2+ dysregulation in AD may result in remodelling of the Mef2c interactome leading to abnormal Mef2c-mediated inflammatory responses in microglia

Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study

Introduction: The multiorgan impact of moderate to severe coronavirus infections in the post-acute phase is still poorly understood. We aimed to evaluate the excess burden of multiorgan abnormalities after hospitalisation with COVID-19, evaluate their determinants, and explore associations with patient-related outcome measures. Methods: In a prospective, UK-wide, multicentre MRI follow-up study (C-MORE), adults (aged ≥18 years) discharged from hospital following COVID-19 who were included in Tier 2 of the Post-hospitalisation COVID-19 study (PHOSP-COVID) and contemporary controls with no evidence of previous COVID-19 (SARS-CoV-2 nucleocapsid antibody negative) underwent multiorgan MRI (lungs, heart, brain, liver, and kidneys) with quantitative and qualitative assessment of images and clinical adjudication when relevant. Individuals with end-stage renal failure or contraindications to MRI were excluded. Participants also underwent detailed recording of symptoms, and physiological and biochemical tests. The primary outcome was the excess burden of multiorgan abnormalities (two or more organs) relative to controls, with further adjustments for potential confounders. The C-MORE study is ongoing and is registered with ClinicalTrials.gov, NCT04510025. Findings: Of 2710 participants in Tier 2 of PHOSP-COVID, 531 were recruited across 13 UK-wide C-MORE sites. After exclusions, 259 C-MORE patients (mean age 57 years [SD 12]; 158 [61%] male and 101 [39%] female) who were discharged from hospital with PCR-confirmed or clinically diagnosed COVID-19 between March 1, 2020, and Nov 1, 2021, and 52 non-COVID-19 controls from the community (mean age 49 years [SD 14]; 30 [58%] male and 22 [42%] female) were included in the analysis. Patients were assessed at a median of 5·0 months (IQR 4·2–6·3) after hospital discharge. Compared with non-COVID-19 controls, patients were older, living with more obesity, and had more comorbidities. Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p<0·0001) and independently associated with COVID-19 status (odds ratio [OR] 2·9 [95% CI 1·5–5·8]; padjusted=0·0023) after adjusting for relevant confounders. Compared with controls, patients were more likely to have MRI evidence of lung abnormalities (p=0·0001; parenchymal abnormalities), brain abnormalities (p<0·0001; more white matter hyperintensities and regional brain volume reduction), and kidney abnormalities (p=0·014; lower medullary T1 and loss of corticomedullary differentiation), whereas cardiac and liver MRI abnormalities were similar between patients and controls. Patients with multiorgan abnormalities were older (difference in mean age 7 years [95% CI 4–10]; mean age of 59·8 years [SD 11·7] with multiorgan abnormalities vs mean age of 52·8 years [11·9] without multiorgan abnormalities; p<0·0001), more likely to have three or more comorbidities (OR 2·47 [1·32–4·82]; padjusted=0·0059), and more likely to have a more severe acute infection (acute CRP >5mg/L, OR 3·55 [1·23–11·88]; padjusted=0·025) than those without multiorgan abnormalities. Presence of lung MRI abnormalities was associated with a two-fold higher risk of chest tightness, and multiorgan MRI abnormalities were associated with severe and very severe persistent physical and mental health impairment (PHOSP-COVID symptom clusters) after hospitalisation. Interpretation: After hospitalisation for COVID-19, people are at risk of multiorgan abnormalities in the medium term. Our findings emphasise the need for proactive multidisciplinary care pathways, with the potential for imaging to guide surveillance frequency and therapeutic stratification