Biology subjects

Wells, P. M.

Publications and source records attributed to Wells, P. M..

7 recordsLinked to original sources

bioRxiv2026

Best Practices for Pre-Processing Large-Scale ATAC-Seq Data: Why Epidemiological Studies Demand Greater Stringency

Assay for transposase accessible chromatin using sequencing (ATAC-seq) and related techniques provide critical insight into the epigenetic mechanisms that regulate gene expression in health and disease. Accurate identification of biologically meaningful chromatin accessibility signals remains an underexplored analytical challenge. Advances in sequencing technologies have increased both the magnitude and complexity of ATAC-seq datasets, leading to demand for scalable, reproducible and robust computational analysis frameworks. Peak calling, which identifies regions of chromatin accessibility, is a critical step that underpins all downstream quantitative analyses. However, there is a lack of consensus regarding the optimal peak calling strategy. Here, we present a novel bioinformatics pipeline PIPPA (Pipeline for Integrative Peak calling in Population-scale ATAC-seq), for quality control and peak set curation of large-scale ATAC-seq datasets. Using two independent cell-type sorted ATAC-seq datasets, we show that peak calling performance is dataset-dependent and that no single significance threshold performs optimally across all scenarios. We provide practical recommendations for parameters to generate high-confidence chromatin accessibility profiles. Our peak calling approach is applicable for other genome wide epigenomic assays such as ChIP-seq and CUT&Tag. By standardising this process, the PIPPA pipeline enhances epidemiological studies focused in identifying epigenetic dysregulation associated with development and disease.

bioinformatics↗

bioRxiv2026

Cell type-specific histone acetylation landscape in Alzheimer's disease reveals a putative role of MITF in microglia

Alzheimer's disease (AD) is characterised by aberrant amyloid beta and tau aggregation, neuroinflammation, demyelination and neurodegeneration, which have been linked to changes in cell-specific gene expression signatures. Among the mechanisms driving cell-type-specific transcriptional changes, histone acetylation plays a central role in regulating gene activity. While global alterations in histone acetylation have been implicated in AD, the contribution of individual cell types to these epigenetic changes remains poorly understood. To decode cell-type-specific changes in gene regulation in AD pathogenesis, we profiled histone H3 lysine 27 acetylation (H3K27ac) in microglia, oligodendrocytes and neurons from the prefrontal cortex of individuals with late-stage AD and non-dementia controls. Oligodendrocytes had the highest number of differential H3K27ac regions in AD, followed by microglia. Genes nearest to differential H3K27ac in purified microglia were enriched for phagocytosis, lipid processing, inflammatory and disease-associated cell state signature genes. Gene network analysis revealed downregulation of homeostatic genes in AD microglia and upregulation of immune activation, including signatures of lipid-handling and monocyte-derived macrophages. Oligodendrocyte co-regulated regions were indicative of increased MHC class I antigen presentation and altered neuron-oligodendrocyte interactions in AD. We identified H3K27ac allele-specific variants (ASVs) enriched near endolysosomal and ubiquitin-proteasome-associated genes in microglia and neurons. ASVs coincided with AD genome-wide association study (GWAS) risk loci, including CLU in oligodendrocytes and HLA-DRB1 in microglia. DNA motif analysis identified putative transcription factor drivers of AD glial dysregulation, including the lysosomal-associated MITF, Cap'n'collar (CNC) family (BACH1 and NFE2) and AP-1 activation in microglia. DNA binding of the MITF protein in human microglia was localised to lysosomal-associated genes and enriched in H3K27ac regions upregulated in AD and near disease-associated microglia (DAM) genes. Collectively, these findings implicate lysosomal dysfunction and upstream transcriptional regulation via MITF as key processes in AD microglia.

neuroscience↗

bioRxiv2026

Post-transcriptional control by RNA-binding proteins links local synaptic translation to schizophrenia genetic risk

BackgroundSynaptic function is increasingly recognized as a core property of genes implicated in psychiatric disorders. Defining the specific synaptic molecular systems underlying genetic risk is critical step toward therapeutic advances. Synaptic processes rely on rapid protein production driven by local translation of mRNA in context-specific synapses. Synaptic mRNA metabolism, transport and local translation is regulated by RNA-binding proteins (RBPs). Here, we hypothesized that genetic risk converges on localised transcripts with synaptic function and aimed to identify RBP regulatory systems that capture this shared schizophrenia genetic risk. MethodsWe use recent human and mouse bulk and single-synapse transcriptomic and proteomic datasets to test for enrichment of schizophrenia genetic risk among mRNAs stratified by localization and synaptic function employing gene set association (MAGMA) and heritability enrichment (S-LDSC) analyses. Prioritized transcripts were further analyzed for RBP control through motif enrichment analysis (Transite) of the 3UTRs of these transcripts. Candidate RBPs were then evaluated based on the strength of genetic association among their predicted binding targets. ResultsWe demonstrate that genes encoding localised mRNAs with synaptic function show significantly greater genetic association than other synaptic genes. We identified a subset of RBPs, RBFOX1/2/3, CELF4, HNRNPR, and nELAVL, whose motifs are enriched in localised synaptic mRNAs and whose targets are enriched for schizophrenia risk variants. These RBPs are prioritized as candidate regulatory systems through which genetic risk may converge on the transport, splicing and translation of localised transcripts with synaptic function. ConclusionsOur results highlight potential regulatory systems through which genetic variation influences synaptic mechanisms and provide a scalable framework for refining the link between genetic association and post-transcriptional regulation in neuropsychiatric disorders.

neuroscience↗

bioRxiv2025

Optimised fluorescence-activated nuclei sorting for epigenomic analysis of cortical cell types

Increased understanding of the functional complexity of the genome has led to growing recognition of the role of non-sequence-based regulatory variation in disorders of the human central nervous system. Most genomic analyses of the brain are limited by the use of bulk tissue, which comprises a heterogeneous mix of different neural cell types with distinct epigenetic profiles, thereby limiting the ability to attribute regulatory changes to specific cell populations. Given the limited availability of human post-mortem tissue resources and the importance of integrating multi-omic data from the same samples, there is a critical need for methods that enable parallel, cell-type-resolved genomic profiling. We present optimised protocols using fluorescence-activated nuclei sorting (FANS) to isolate nuclei from different human and mouse brain cell types for downstream multi-omic analysis. Our approach enables the robust purification of neuronal, oligodendrocyte, microglial and other glial-origin nuclei from both adult and fetal brain tissue. We demonstrate that FANS-isolated nuclei are compatible with a wide range of genomic assays, including profiling of DNA modifications, histone modifications, chromatin accessibility, and gene expression. This protocol maximises the utility of limited post-mortem tissue resources and provides a unified workflow for comprehensive, cell-type-specific interrogation of molecular mechanisms involved in the brain.

genomics↗

bioRxiv2021

Influential factors of saliva microbiota composition

BackgroundThe oral microbiota is emerging as an influential factor of host physiology and disease state. Factors influencing oral microbiota composition have not been well characterised. In particular, there is a lack of population-based studies. We undertook a large hypothesis-free study of the saliva microbiota, considering potential influential factors of host health (frailty; diet; periodontal disease), demographics (age; sex; BMI) and sample processing (storage time), in a sample (n=679) of the TwinsUK cohort of adult twins. ResultsAlpha and beta diversity of the saliva microbiota was associated most strongly with frailty (alpha diversity: Q = 0.003, Observed; Q=0.002, Shannon; Q=0.003, Simpson; Beta diversity: Q = 0.002, Bray Curtis dissimilarity) and age (alpha diversity: Q=0.006, Shannon; Q=0.003, Simpson; beta diversity: Q=0.002, Bray Curtis dissimilarity; Q= 0.032, Weighted UniFrac) in multivariate models including age, frailty, sex, BMI, frailty and diet, and adjustment for multiple testing. Those with a more advanced age were more likely to be dissimilar in the saliva microbiota composition than younger participants (P = 5.125e-06, ANOVA). In subsample analyses, including consideration of periodontal disease (total n=138, periodontal disease n=66), the association with frailty remained for alpha diversity (Q=0.002, Observed ASVs; Q= 0.04 Shannon Index), but not beta diversity, whilst age was not demonstrated to associate with alpha or beta diversity in this subsample, potentially due to insufficient statistical power. Length of time that samples were stored prior to sequencing was associated with beta diversity (Q = 0.002, Bray Curtis dissimilarity). Six bacterial taxa were associated with age after adjustment for frailty and diet. ConclusionsFrailty and age emerged as the most influential factors of saliva microbiota composition. Whilst frailty and age are correlates, the associations were independent of each other, suggesting that both biological and chronological ageing are key drivers of saliva microbiota composition.

microbiology↗

bioRxiv2019

The urinary tract microbiome in older women exhibits host genetics and environmental influences

The urinary microbiome is a relatively unexplored niche despite the fact that we now know that it is not sterile. Moreover urinary microbes, especially in ageing populations, are associated with morbidity even when infection is subsequently not proven. We present the first large-scale study to explore factors defining urinary microbiome composition in community-dwelling older adult women without clinically active infection. Using 1600 twins, we estimate the contribution of genetic and environmental factors to variation in microbiome using both 16S and shotgun metagenomics. We found that the urinary microbiome is distinct from nearby sites and is unrelated to stool microbiome. Core urinary microbiome taxa were defined. The first component of weighted unifrac was heritable (18%) as were key taxa (e.g Escherichia-Shigella (A>0.15)). Age, menopausal status, prior UTI and host genetics were top among factors defining the urobiome. Increased composition was associated with older age, contrary to previous findings.

microbiology↗

bioRxiv2019

Genome-wide scan identifies novel genetic loci regulating salivary metabolite levels

Saliva, as a biofluid, is inexpensive and non-invasive to obtain, and provides a vital tool to investigate oral health and its interaction with systemic health conditions. There is growing interest in salivary biomarkers for systemic diseases, notably cardiovascular disease. Whereas hundreds of genetic loci have been shown to be involved in the regulation of blood metabolites leading to unprecedented insights into the pathogenesis of complex human diseases, little is known about the impact of host genetics on salivary metabolites. Here we report the first genome-wide association study exploring 476 salivary metabolites in 1,419 subjects of European ancestry from the TwinsUK cohort (discovery phase). A total of 14 salivary metabolites were significantly associated (p<10-10) with genetic variants that mapped to 11 distinct loci, most of which replicated in the Study of Health in Pomerania (SHIP-2) cohort. Interestingly, while only a limited number of the loci that are known to regulate blood metabolites were also associated with salivary metabolites in our study, we identified several novel saliva-specific locus-metabolite associations, including associations for the AGMAT (with the metabolites 4-guanidinobutanoate and beta-guanidinopropanoate), ATP13A5 (with the metabolite creatinine) and DPYS (with the metabolites 3-ureidopropionate and 3-ureidoisobutyrate) loci. Our study suggests that there are biological pathways which are specific to the regulation of the salivary metabolome. In addition, some of our findings may have clinical relevance, such as the utility of the pyrimidine (uracil) degradation metabolites in predicting 5-fluorouracil toxicity and the role of the agmatine pathway metabolites as biomarkers of oral health.

genetics↗