Biology subjects

Breeze, C.

Publications and source records attributed to Breeze, C..

5 recordsLinked to original sources

bioRxiv2021

Cell type-specific signal analysis in EWAS

Hundreds of epigenome-wide association studies (EWAS) have been performed, successfully identifying replicated epigenomic signals in processes such as ageing and smoking. Despite this progress, it remains a major challenge in EWAS to detect both cell type-specific and cell type confounding effects impacting study results. One way to identify these effects is through eFORGE (experimentally derived Functional element Overlap analysis of ReGions from EWAS), a published tool that uses 815 datasets from large-scale mapping studies to detect enriched tissues, cell types and genomic regions. Here, I show that eFORGE analysis can be extended to EWAS differentially variable positions (DVPs), identifying target cell types and tissues. In addition, I also show that eFORGE tissue-specific enrichment can be detected for sites below EWAS significance threshold. I develop on these and other analysis examples, extending our knowledge of eFORGE cell type- and tissue-specific enrichment results for different EWAS.

genomics↗

bioRxiv2021

Calling differential DNA methylation at cell-type resolution: avoiding misconceptions and promoting best practices

The accurate detection of cell-type specific DNA methylation alterations in the context of general epigenome studies is an important task to improve our understanding of epigenomics in disease development. Although a number of statistical algorithms designed to address this problem have emerged, the task remains challenging. Here we show that a recent commentary by Rahmani et al, that aims to address misconceptions and best practices in the field, continues to suffer from critical misconceptions in how statistical algorithms should be compared and evaluated. In addition, we report contradictory results on real EWAS datasets.

bioinformatics↗

bioRxiv2021

A mammalian methylation array for profiling methylation levels at conserved sequences

Infinium methylation arrays are not available for the vast majority of non-human mammals. Moreover, even if species-specific arrays were available, probe differences between them would confound cross-species comparisons. To address these challenges, we developed the mammalian methylation array, a single custom array that measures 36k CpGs that are well conserved across mammalian species. We designed a set of probes on the array that can tolerate specific cross-species mutations. We annotate the array in over 200 species and report CpG island status and chromatin states in select species. Calibration experiments demonstrate the high fidelity in humans, rats, and mice. The mammalian methylation array has several strengths: it applies to all mammalian species even those that have not yet been sequenced, it provides deep coverage of conserved cytosines facilitating the development epigenetic biomarkers, and it increases the probability that biological insights gained in one species will translate to others.

bioinformatics↗

bioRxiv2020

Epigenetic clock and methylation studies in the rhesus macaque

Methylation levels at specific CpG positions in the genome have been used to develop accurate estimators of chronological age in humans, mice, and other species. Although epigenetic clocks are generally species-specific, the principles underpinning them appear to be conserved at least across the mammalian class. This is exemplified by the successful development of epigenetic clocks for mice and several other mammalian species. Here, we describe epigenetic clocks for the rhesus macaque (Macaca mulatta), the most widely used nonhuman primate in biological research. Using a custom methylation array (HorvathMammalMethylChip40), we profiled n=281 tissue samples (blood, skin, adipose, kidney, liver, lung, muscle, and cerebral cortex). From these data, we generated five epigenetic clocks for macaques. These clocks differ with regards to applicability to different tissue types (pan-tissue, blood, skin), species (macaque only or both humans and macaques), and measure of age (chronological age versus relative age). Additionally, the age-based human-macaque clock exhibits a high age correlation (R=0.89) with the vervet monkey (Chlorocebus sabaeus), another Old World species. Four CpGs within the KLF14 promoter were consistently altered with age in four tissues (adipose, blood, cerebral cortex, skin). It is expected that the macaque clocks will reveal an epigenetic aging rate associated with a host of health conditions and thus lend themselves for identifying and validating anti-aging interventions.

developmental biology↗

bioRxiv2019

Running rabid: modelling of European bat lyssavirus (EBLV) pathways in a bat population

Worldwide the 16 species of lyssaviruses all exhibit a similar pathology in most mammals, including man; with successful infections usually ending with death. Recently it has been demonstrated that European bat lyssaviruses (EBLV) are not invariably fatal in their wild reservoir host bat species, however the mechanisms and epidemiological consequences of this resistance are interesting and unexplored and the fundamental pathology in bats is still unclear. Here we modelled alternative pathological pathways to explore which appear most plausible, with respect to our limited knowledge of bat-rabies epidemiology and also host population dynamics. Two models were created, one based on a standard progression of disease (classic SEIR model) and the other modified to allow for animals to become either rabid or immune (flexible model). Of these our flexible model was found to be more plausible, demonstrating a much lower sensitivity to epidemiological parameters and by inference the more likely to represent the real-life process occurring in wild European bat populations, with a comparative state space ratio of 1:47. This result implies that it is highly probable survival and post-infection immunity is a widespread epidemiological phenomenon rather than an infrequent consequence of an aborted infection in few individuals. These results can be used to inform laboratory studies on bat immunology and future bat modelling work.

ecology↗