Biology subjects

Turner, F.

Publications and source records attributed to Turner, F..

3 recordsLinked to original sources

bioRxiv2025

Loss of circulating glucocorticoid rhythm disrupts the circadian transcriptome and vascular reactivity in the mouse renal artery

AimsMolecular clocks in the vasculature contribute to the normal circadian blood pressure (BP) rhythm. Glucocorticoids are known to synchronise molecular clocks within peripheral tissues. Disruption of the endogenous glucocorticoid rhythm causes "non-dipping", a BP pattern associated with elevated cardiovascular risk. The mechanisms for this are unclear but vascular changes likely contribute. We examined the effect of impaired glucocorticoid rhythmicity on the time-of-day dependent vascular function and define the circadian transcriptome under control conditions and under arrhythmic glucocorticoids. Methods and ResultsMale C57BL6J mice kept on a 12:12 hour light/dark cycle were implanted with a subcutaneous slow-release pellet containing vehicle or corticosterone ([~]3.7mg/kg/day), which flattened the endogenous glucocorticoid rhythm. After 7 days, renal arteries were isolated at 7am and 7pm to measure vasoreactivity using wire myography. Other arteries were taken 2-hourly over a 48-hour period for RNA sequencing. In control arteries, endothelium-dependent and independent vasodilation was elevated at wake-phase compared to the sleep-phase. This temporal variation was absent in the renal arteries from corticosterone treated mice. Using CircaCompare and LimoRhyde, we found circadian rhythms in 459 of the 14 225 protein-coding transcripts in control arteries. Following corticosterone treatment, 156 genes lost their rhythm, including canonical clock genes, genes involved in "peroxide homeostasis" such as Nox4 and "TNF signalling" like Mmp14. Paradoxically 492 genes gained a rhythm and were predominantly mitochondrial-related. ConclusionsThis study expands the molecular landscape for understanding circadian vascular physiology and emphasises the impact of glucocorticoid rhythm on temporal changes in gene expression and vascular function. This is clinically relevant to the pathogenesis of vascular dysfunction associated with perturbed glucocorticoid signalling for e.g. in metabolic syndrome and chronic stress. TRANSLATIONAL PERSPECTIVEDisruption of the normal circadian rhythm of plasma glucocorticoid levels causes non-dipping blood pressure, a profile associated with enhanced cardiovascular risk. The role of vascular dysfunction in this context is unknown. We report that arrhythmic plasma glucocorticoid levels impair time-dependent vasoreactivity and alters the circadian transcriptome of the renal artery. We provide a molecular framework for investigations into glucocorticoid-induced vascular dysfunction across the 24-hour day. Clinically, this is relevant for patients on chronic glucocorticoid therapy but could have generalisable implications for the underlying mechanisms of blood pressure rhythm. Targeting rhythm-sensitive vascular pathways may offer novel avenues to improve blood pressure rhythms. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/650449v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1c988b8org.highwire.dtl.DTLVardef@2f0ee7org.highwire.dtl.DTLVardef@17b6e25org.highwire.dtl.DTLVardef@7c6afb_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2018

Genome-wide disruption of DNA methylation by 5-aza-2’-deoxycytidine in the parasitioid wasp Nasonia vitripennis

DNA methylation of cytosine residues across the genome influences how genes and phenotypes are regulated in a wide range of organisms. As such, understanding the role of DNA methylation and other epigenetic mechanisms has become very much a part of mapping genotype to phenotype, a major question in evolutionary biology. Ideally, we would like to manipulate DNA methylation patterns on a genome-wide scale, to help us to elucidate the role that epigenetic modifications play in phenotypic expression. Recently, the demethylating agent 5-aza-2-deoxycytidine (5-aza-dC; commonly used in the epigenetic treatment of certain cancers), has been deployed to explore the epigenetic regulation of a number of traits of interest to evolutionary ecologists, including facultative sex allocation in the parasitoid wasp Nasonia vitripennis. In a recent study, we showed that treatment with 5-aza-dC did not ablate the facultative sex allocation response in Nasonia, but shifted the patterns of sex allocation in a way predicted by genomic conflict theory. This was the first (albeit indirect) experimental evidence for genomic conflict over sex allocation facilitated by DNA methylation. However, that work lacked direct evidence of the effects of 5-aza-dC on DNA methylation, and indeed the effect of the chemical has since been questioned in Nasonia. Here, using whole-genome bisulphite sequencing of more than 4 million CpGs, across more than 11,000 genes, we demonstrate unequivocally that 5-aza-dC disrupts methylation on a large scale across the Nasonia vitripennis genome. We show that the disruption can lead to both hypo- and hyper-methylation, may vary across tissues and time of sampling, and that the effects of 5-aza-dC are context- and sequence specific. We conclude that 5-aza-dC does indeed have the potential to be repurposed as a tool for studying the role of DNA methylation in evolutionary ecology, whilst many details of its action remain to be discovered. Author SummaryShedding light on the mechanistic basis of phenotypes is a major aim in the field of evolutionary biology. If we understand how phenotypes are controlled at the molecular level, we can begin to understand how evolution has shaped that phenotype and conversely, how genetic architecture may constrain trait evolution. Epigenetic markers (such as DNA methylation) also influence phenotypic expression by regulating how and when genes are expressed. Recently, 5-aza-2-deoxycytidine (5-aza-dC), a hypomethylating agent used in the treatment of certain cancers, has been used to explore the epigenetic regulation of traits of interest to evolutionary ecologists. Previously, we used 5-aza-dC to validate a role for DNA methylation in facultative sex allocation behaviour in the parasitoid wasp Nasonia vitripennis. However, the direct effects of the chemical were not examined at that point and its efficacy in insects was questioned. Here, we demonstrate that 5-aza-dC disrupts DNA methylation on a genome-wide scale in a context- and sequence-specific manner and results in both hypo- and hyper-methylation. Our work demonstrates that 5-aza-dC has the potential to be repurposed as a tool for studying the role of DNA methylation in phenotypic expression.

evolutionary biology↗

bioRxiv2017

Maintaining their genetic distance; limited gene flow between widely hybridising species of Geum with contrasting mating systems

Mating system transition from outcrossing to selfing frequently gives rise to sister lineages with contrasting outcrossing rates. The evolutionary fate of such lineages depends on the extent to which they exchange genes. We measured gene flow between outcrossing Geum rivale and selfing G. urbanum, two sister species derived by mating system transition, which frequently hybridise. A draft genome was generated for G. urbanum and used to develop dd-RAD data scorable in both species. Coalescent analysis of RAD data from allopatric populations indicated that the two species diverged 2-3 Mya, and that long term gene flow between them has been very low (M=0.04). G. rivale showed greater genetic diversity in sympatry than allopatry, but genetic divergence between species was no lower in sympatry than allopatry, providing little evidence for recent introgression. Clustering of genotypes revealed that, apart from four early generation hybrids, individuals in sympatric populations fell into two genetically distinct groups with <1% admixture that corresponded exactly to their morphological species classification. Although our data suggest limited gene flow, we observed joint segregation of two putatively introgressed SNPs in G. urbanum populations that was associated with significant morphological variation; this provides tentative evidence for rare introduction of novel genetic diversity by interspecific gene flow. Our results indicate that despite frequent hybridisation, genetic exchange between G. rivale and G. urbanum has been very limited throughout their evolutionary history.

evolutionary biology↗