Biology subjects

Montgomery, C.

Publications and source records attributed to Montgomery, C..

At least 19 recordsLinked to original sources

bioRxiv2026

Molecular profiling implicates immune-driven adaptive homeostasis in maintaining intraocular pressure with age

Aging and ocular hypertension are primary risk factors for glaucoma - a major cause of blindness worldwide. Ocular hypertension results from dysfunction in the outflow tissues - the trabecular meshwork (TM) and Schlemm's canal (SC), which are key regulators of intraocular pressure (IOP) homeostasis. Despite lifelong multifaceted stress to the outflow pathway, ocular hypertension sufficient to develop glaucoma occurs in only a minority of individuals. The mechanisms that preserve physiological IOP with aging in most individuals remain poorly understood. Using single-cell RNA sequencing and protein validation in mouse outflow tissues, we found that aging is accompanied by subtype-specific changes in TM cells, including altered extracellular matrix maintenance, reduced trophic signaling to SC, and increased profibrotic signaling. Coincident with these changes, we observed age-dependent immune remodeling, marked by increased macrophage abundance in outflow tissues. Our model predicts that macrophages maintain SC homeostasis via VEGFA signaling - normally supplied by the TM and required for normal SC function, but impaired with age. This pattern supports a paradigm in which adaptive immune remodeling contributes to preserving IOP homeostasis despite progressive aging-associated cellular dysfunction. More broadly, we identify the TM/SC outflow pathway as a model for understanding how aging tissues preserve physiological function through coordinated structural, trophic, and adaptive immune remodeling.

cell biology↗

bioRxiv2026

Ancestry-specific rewiring of BCR-MAPK signaling in sarcoidosis B cells

Sarcoidosis is a heterogenous disease of unknown etiology characterized by non-caseating granulomas. Disease prevalence and presentation vary significantly by ancestry and ranges from acute, self-resolving disease to severe, chronic disease. Following previous reports suggesting B cells in the development and pathogenesis of sarcoidosis, we present here results of single-cell RNA sequencing, supporting B cell involvement in sarcoidosis through altered immediate early response, rewiring of MAPK signaling, and ancestry-specific preferential expansion of B cell receptors. Peripheral blood mononuclear cells were obtained from individuals of African or European Ancestry (AA and EA, respectively) including 48 healthy controls, 59 sarcoidosis patients, and 28 systemic lupus erythematosus (SLE) patients. SLE samples were used as a disease control. Differential expression analysis highlighted many differentially expressed genes (DEGs) with almost 5x more in the AA sarcoidosis versus AA control group compared to the EA sarcoidosis versus EA control group. B cells had the most DEGs of all cell types and expression patterns were similar between ancestries, however, sarcoidosis had an opposite transcription pattern than SLE, demonstrating an alternative immune response to acute activation than that seen in a prototypical autoinflammatory disease. This trend was maintained when examining specialized B cell subsets, with the most pronounced effect in the AA sarcoidosis versus AA control comparison. Our results strongly support further investigation of the role of humoral immune response in sarcoidosis and the potential to highlight patient groups likely to benefit from existing B cell therapies.

immunology↗

bioRxiv2025

Oligodendrocytes show enriched expression of amyloid precursor protein and GABA B receptor isoform 1a

Amyloid precursor protein (APP) is a type I transmembrane protein that undergoes proteolytic processing to generate amyloid-{beta}, the main component of amyloid plaques found in brains with Alzheimers disease. The proteolytic processing of APP also generates soluble APP alpha (sAPP) which can modulate synaptic transmission and neurite outgrowth through the {gamma}-aminobutyric acid type B receptor (GABABR). Whether GABABR mediates functions of sAPP in other neural cell types such as glia remains unknown. sAPP binds the R1a subunit isoform of GABABR1 which contains two sushi domains absent in R1b. It is unclear whether both GABABR1 isoforms are expressed equally across brain cell types. We determined relative RNA levels of the GABABR1a and 1b isoforms in oligodendrocytes, microglia, endothelial cells, astrocytes, and neurons in adult mice using two approaches. We developed a GABABR1 isoform-specific RNAseq analysis workflow to probe a publicly available dataset. We also isolated five cell types from a single mouse brain and performed RT-qPCR. We show that the GABABR1a and 1b isoforms are differentially expressed among cell types. GABABR1a expression was highest in oligodendrocytes and GABABR1b expression was highest in astrocytes, suggesting that sAPP-mediated GABABR signaling may be most prominent in oligodendrocytes. We also confirmed that APP is expressed in all five cell types and showed that APP RNA levels are highest in oligodendrocytes. Together, our findings uncover cell type-specific expression of GABABR isoforms and highlight oligodendrocytes as a principal cell type for GABABR1a-mediated APP signaling, providing a foundation for future mechanistic studies.

neuroscience↗

bioRxiv2025

Single-Cell Characterization of Anterior Segment Development: Cell Types, Pathways, and Signals Driving Formation of the Trabecular Meshwork and Schlemm's Canal

Morphogenesis of the anterior segment (AS) is crucial for healthy ocular physiology and vision but is only partially understood. The Schlemms canal (SC) and trabecular meshwork (TM) are essential drainage tissues within the AS, and their proper development and function are critical for maintaining normal intraocular pressure; abnormalities in either tissue can result in elevated pressure and glaucoma. Here, we use single-cell transcriptomic profiling to provide high-resolution molecular detail of AS development with a particular focus on SC and TM. We report transcriptomes for [~]130,000 single cells at key developmental stages from postnatal day 2 (P2) to P60. We provide the first annotation of cell types across these developmental stages and crucial information about dynamic changes in pathways/gene expression. Further, we trace developmental trajectories for TM cell and SC endothelial cell (SEC) subtypes and determine genes and signaling networks driving their specific cell fates. We demonstrate dynamic changes in signaling interactions between SC and the TM cells during their synchronized development. Collectively, our data lay a deep molecular foundation for AS development that will direct understanding of normal ocular physiology, glaucoma, and other AS conditions.

developmental biology↗

bioRxiv2025

Male and Female Mice Are Similarly Susceptible to Chronic Nondiscriminatory Social Defeat Stress Despite Differences in Attack Frequency from Aggressor

RationaleMood disorders are often precipitated by chronic stress and can result in an inability to adapt to the environment and increased vulnerability to challenging experiences. While diagnoses of mood disorders are diagnosed twice as frequently in women than in men, most preclinical chronic social defeat stress mouse models exclude females due to decreased aggression toward female intruders. ObjectivesWe previously reported that the chronic non-discriminatory social defeat stress (CNSDS) paradigm is effective in both sexes, allowing for comparisons between male and female mice. We aimed to improve the screening protocol to identify CD-1 aggressors for use in CNSDS and the method for determining susceptibility to CNSDS. Finally, we aimed to determine whether susceptibility to CNSDS correlated with impaired performance in a satiety- based outcome devaluation task. MethodsWe analyzed CNSDS screening and social defeat sessions to determine appropriate parameters for selecting CD-1 aggressors and investigated aggressions toward male and female intruder mice. We also investigated CNSDS effects on a reward valuation task. ResultsWe observed that despite receiving fewer attacks, female mice are equally susceptible to CNSDS as males and that CNSDS abolished satiety-based outcome devaluation in susceptible male and female mice, but not in resilient male and female mice. ConclusionsThese data suggest that CNSDS-defined susceptible and resilient phenotypes extend to reward behaviors.

neuroscience↗

bioRxiv2025

Pyruvate and Related Energetic Metabolites Modulate Resilience Against High Genetic Risk for Glaucoma

A glaucoma polygenic risk score (PRS) can effectively identify disease risk, but some individuals with high PRS do not develop glaucoma. Factors contributing to this resilience remain unclear. Using 4,658 glaucoma cases and 113,040 controls in a cross-sectional study of the UK Biobank, we investigated whether plasma metabolites enhanced glaucoma prediction and if a metabolomic signature of resilience in high-genetic-risk individuals existed. Logistic regression models incorporating 168 NMR-based metabolites into PRS-based glaucoma assessments were developed, with multiple comparison corrections applied. While metabolites weakly predicted glaucoma (Area Under the Curve=0.579), they offered marginal prediction improvement in PRS-only-based models (P=0.004). We identified a metabolomic signature associated with resilience in the top glaucoma PRS decile, with elevated glycolysis-related metabolites--lactate (P=8.8E-12), pyruvate (P=1.9E-10), and citrate (P=0.02)--linked to reduced glaucoma prevalence. These metabolites combined significantly modified the PRS-glaucoma relationship (Pinteraction=0.011). Higher total resilience metabolite levels within the highest PRS quartile corresponded to lower glaucoma prevalence (Odds Ratiohighest vs. lowest total resilience metabolite quartile=0.71, 95% Confidence Interval=0.64-0.80). As pyruvate is a foundational metabolite linking glycolysis to tricarboxylic acid cycle metabolism and ATP generation, we pursued experimental validation for this putative resilience biomarker in a human-relevant Mus musculus glaucoma model. Dietary pyruvate mitigated elevated intraocular pressure (P=0.002) and optic nerve damage (P<0.0003) in Lmx1bV265D mice. These findings highlight the protective role of pyruvate-related metabolism against glaucoma and suggest potential avenues for therapeutic intervention.

genomics↗

bioRxiv2024

Single-cell profiling of trabecular meshwork identifies mitochondrial dysfunction in a glaucoma model that is protected by vitamin B3 treatment

Since the trabecular meshwork (TM) is central to intraocular pressure (IOP) regulation and glaucoma, a deeper understanding of its genomic landscape is needed. We present a multimodal, single-cell resolution analysis of mouse limbal cells (includes TM). In total, we sequenced 9,394 wild-type TM cell transcriptomes. We discovered three TM cell subtypes with characteristic signature genes validated by immunofluorescence on tissue sections and whole-mounts. The subtypes are robust, being detected in datasets for two diverse mouse strains and in independent data from two institutions. Results show compartmentalized enrichment of critical pathways in specific TM cell subtypes. Distinctive signatures include increased expression of genes responsible for 1) extracellular matrix structure and metabolism (TM1 subtype), 2) secreted ligand signaling to support Schlemms canal cells (TM2), and 3) contractile and mitochondrial/metabolic activity (TM3). ATAC-sequencing data identified active transcription factors in TM cells, including LMX1B. Mutations in LMX1B cause high IOP and glaucoma. LMX1B is emerging as a key transcription factor for normal mitochondrial function and its expression is much higher in TM3 cells than other limbal cells. To understand the role of LMX1B in TM function and glaucoma, we single-cell sequenced limbal cells from Lmx1bV265D/+mutant mice (2,491 TM cells). In V265D/+ mice, TM3 cells were uniquely affected by pronounced mitochondrial pathway changes. Mitochondria in TM cells of V265D/+ mice are swollen with a reduced cristae area, further supporting a role for mitochondrial dysfunction in the initiation of IOP elevation in these mice. Importantly, treatment with vitamin B3 (nicotinamide), to enhance mitochondrial function and metabolic resilience, significantly protected Lmx1b mutant mice from IOP elevation.

molecular biology↗

bioRxiv2024

IOP-induced blood-retinal barrier compromise contributes to RGC death in glaucoma

The integrity of the blood-retinal barrier (BRB) has been largely unexplored in glaucoma. We reveal that elevated intraocular pressure (IOP) partially compromises the BRB in two human-relevant inherited mouse models of glaucoma (DBA/2J and Lmx1bV265D). Experimentally increasing IOP in mouse eyes further confirms this. Notably, the compromise induces subtle leakage, happening without bleeding or detected endothelial cell junction disruption, and it precedes neurodegeneration. Leakage occurs from peripheral veins in the retinal ganglion cell layer with a concomitant loss of the transcytosis inhibitor MFSD2A. Importantly, stabilizing {beta}-catenin in retinal endothelial cells prevents both vascular leakage and neurodegeneration in the DBA/2J model. The occurrence of leakage in all 3 high IOP models indicates that BRB compromise may be a common, yet overlooked, mechanism in glaucoma. These findings suggest that IOP-induced BRB compromise plays a critical role in glaucoma, offering a new therapeutic target.

neuroscience↗

bioRxiv2024

In vivo quantification of anterior and posterior chamber volumes in mice: implications for aqueous humor dynamics

PurposeAqueous humor inflow rate, a key parameter influencing aqueous humor dynamics, is typically measured by fluorophotometery. Analyzing fluorophotometric data depends, inter alia, on the volume of aqueous humor in the anterior, but not the posterior, chamber. Previous fluorophotometric studies of aqueous inflow rate in mice have assumed the ratio of anterior:posterior volumes in mice to be similar to those in humans. Our goal was to measure anterior and posterior chamber volumes in mice to facilitate better estimates of aqueous inflow rates. MethodsWe used standard near-infrared optical coherence tomography (OCT) and robotic visible-light OCT (vis-OCT) to visualize, reconstruct and quantify the volumes of the anterior and posterior chambers of the mouse eye in vivo. We used histology and micro-CT scans to validate relevant landmarks from ex vivo tissues to facilitate in vivo measurement. ResultsPosterior chamber volume is 1.1 times the anterior chamber volume in BALB/cAnNCrl mice, i.e. the anterior chamber constitutes about 47% of the total aqueous humor volume, which is very dissimilar to the situation in humans. Anterior chamber volumes in 2-month-old BALB/cAnNCrl and 7-month-old C57BL6/J mice were 1.55 {+/-} 0.36 {micro}L (n=10) and 2.41 {+/-} 0.29 {micro}L (n=8), respectively. This implies that previous studies likely over-estimated aqueous inflow rate by approximately two-fold. ConclusionsIt is necessary to reassess previously reported estimates of aqueous inflow rates, and thus aqueous humor dynamics in the mouse. For example, we now estimate that only 0-15% of aqueous humor drains via the pressure-independent (unconventional) route, similar to that seen in humans and monkeys.

physiology↗

bioRxiv2024

From Cardiac Myosin to the Beta Receptor: Autoantibodies Promote a Fibrotic Transcriptome and Reduced Ventricular Recovery in Human Myocarditis

BackgroundMyocarditis leads to dilated cardiomyopathy (DCM) with one-third failing to recover normal ejection fraction (EF50%), and there is a critical need for prognostic biomarkers to assess risk of nonrecovery. Cardiac myosin (CM) autoantibodies (AAbs) cross-reactive with the {beta}-adrenergic receptor ({beta}AR) are associated with myocarditis/DCM, but their potential for prognosis and functional relevance is not fully understood. MethodsCM AAbs and myocarditis-derived human monoclonal antibodies (mAbs) were investigated to define pathogenic mechanisms and CM epitopes of nonrecovery. Myocarditis patients who do not recover ejection fraction (EF<50%) by one year were studied in a longitudinal (n=41) cohort. Sera IgG and human mAbs were investigated for autoreactivity with CM and CM peptides by ELISA, protein kinase A (PKA) activation, and transcriptomic analysis in H9c2 heart cell line. ResultsCM AAbs were significantly elevated in nonrecovered compared to recovered patients and correlated with reduced EF (<50%). CM epitopes specific to nonrecovery were identified. Transcriptomic analysis revealed serum IgG and mAb 2C.4 induced fibrosis/apoptosis pathways in vitro similar to isoproterenol treated cells. Sera IgG and 2C.4 activated PKA in an IgG and {beta}AR-dependent manner. Endomyocardial biopsies from myocarditis/DCM revealed IgG+ trichrome+ tissues. ConclusionsCM AAbs were significantly elevated in nonrecovered patients, suggesting novel prognostic relevance. CM AAbs correlated with lower EF, and Ab-induced fibrosis/apoptosis pathways suggested a role for CM AAbs in patients who do not recover and develop irreversible heart failure. Homology between CM and {beta}ARs supports mechanisms related to cross-reactivity of CM AAbs with the {beta}AR, a potential AAb target in nonrecovery.

immunology↗

bioRxiv2024

TLR4 deficiency does not alter glaucomatous progression in a mouse model of chronic glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide. Toll-like receptor 4 (TLR4) is a pattern-recognition transmembrane receptor that induces neuroinflammatory processes in response to injury. Tlr4 is highly expressed in ocular tissues and is known to modulate inflammatory processes in both anterior and posterior segment tissues. TLR4 activation can lead to mitochondrial dysfunction and metabolic deficits in inflammatory disorders. Due to its effects on inflammation and metabolism, TLR4 is a candidate to participate in glaucoma pathogenesis. It has been suggested as a therapeutic target based on studies using acute models, such as experimentally raising IOP to ischemia-inducing levels. Nevertheless, its role in chronic glaucoma needs further evaluation. In the current study, we investigated the role of TLR4 in an inherited mouse model of chronic glaucoma, DBA/2J. To do this, we analyzed the effect of Tlr4 knockout (Tlr4-/-) on glaucoma-associated phenotypes in DBA/2J mice. Our studies found no significant differences in intraocular pressure, iris disease, or glaucomatous progression in Tlr4-/- compared to Tlr4+/+ DBA/2J mice. These data do not identify a role for TLR4 in this chronic glaucoma, but further research is warranted to understand its role in other glaucoma models and different genetic contexts.

neuroscience↗

bioRxiv2023

Transcriptomic profiling of Schlemm's canal cells reveals a lymphatic-biased identity and three major cell states

Schlemms canal (SC) is central in intraocular pressure regulation but requires much characterization. It has distinct inner and outer walls, each composed of Schlemms canal endothelial cells (SECs) with different morphologies and functions. Recent transcriptomic studies of the anterior segment added important knowledge, but were limited in power by SEC numbers or did not focus on SC. To gain a more comprehensive understanding of SC biology, we performed bulk RNA sequencing on C57BL/6J SC, blood vessel, and lymphatic endothelial cells from limbal tissue ([~]4500 SECs). We also analyzed mouse limbal tissues by single-cell and single-nucleus RNA sequencing (C57BL/6J and 129/Sj strains), successfully sequencing 903 individual SECs. Together, these datasets confirm that SC has molecular characteristics of both blood and lymphatic endothelia with a lymphatic phenotype predominating. SECs are enriched in pathways that regulate cell-cell junction formation pointing to the importance of junctions in determining SC fluid permeability. Importantly, and for the first time, our analyses characterize 3 molecular classes of SECs, molecularly distinguishing inner wall from outer wall SECs and discovering two inner wall cell states that likely result from local environmental differences. Further, and based on ligand and receptor expression patterns, we document key interactions between SECs and cells of the adjacent trabecular meshwork (TM) drainage tissue. Also, we present cell type expression for a collection of human glaucoma genes. These data provide a new molecular foundation that will enable the functional dissection of key homeostatic processes mediated by SECs as well as the development of new glaucoma therapeutics. Significance statementSchlemms canal is a critical ocular drainage structure that maintains intraocular pressure with important consequences for glaucoma. Despite this, Schlemms canal has been relatively understudied with the molecular process that mediate its function, maintain its health, or that are compromised in glaucoma needing much deeper characterization. This study is important as it provides the most comprehensive molecular characterization of Schlemms canal cells to date providing a wealth of molecular details. In addition to highlighting important biological pathways, this information will guide studies to develop new treatments against glaucoma.

genomics↗

bioRxiv2023

Low Gut Microbial Diversity Augments Estrogen-driven Pulmonary Fibrosis in Female-Predominant Interstitial Lung Disease

Although profibrotic cytokines such as IL-17A and TGF-{beta}1 have been implicated in interstitial lung disease (ILD) pathogenesis, interactions between gut dysbiosis, gonadotrophic hormones and molecular mediators of profibrotic cytokine expression, such as phosphorylation of STAT3, have not been defined. Here we show by chromatin immunoprecipitation sequencing (ChIP-seq) analysis of primary human CD4+ T cells that regions within the STAT3 locus are significantly enriched for binding by the transcription factor estrogen receptor alpha (ERa). Using the murine model of bleomycin-induced pulmonary fibrosis, we found significantly increased regulatory T cells compared to Th17 cells in the female lung. Genetic absence of ESR1 or ovariectomy in mice significantly increased pSTAT3 and IL-17A expression in pulmonary CD4+ T cells, which was reduced after repletion of female hormones. Remarkably, there was no significant reduction in lung fibrosis under either condition, suggesting that factors outside of ovarian hormones also contribute. Assessment of lung fibrosis among menstruating females in different rearing environments revealed that environments favoring gut dysbiosis augment fibrosis. Furthermore, hormone repletion following ovariectomy further augmented lung fibrosis, suggesting pathologic interactions between gonadal hormones and gut microbiota on lung fibrosis severity. Analysis in female sarcoidosis patients revealed a significant reduction in pSTAT3 and IL-17A levels and a concomitant increase in TGF-{beta}1 levels in CD4+ T cells, compared to male sarcoidosis patients. These studies reveal that estrogen is profibrotic in females and that gut dysbiosis in menstruating females augments lung fibrosis severity, supporting a critical interaction between gonadal hormones and gut flora in lung fibrosis pathogenesis.

immunology↗

bioRxiv2022

Regulation of ATAD2B bromodomain binding activity by the histone code

The ATPase family AAA+ domain containing 2 (ATAD2) protein, and its paralog ATAD2B, have a C-terminal bromodomain that functions as a reader of acetylated lysine residues on histone proteins. Using a structure-function approach, we investigated the ability of the ATAD2 and ATAD2B bromodomains to select acetylated lysine among multiple histone post-translational modifications. Isothermal titration calorimetry experiments revealed that the ATAD2 and ATAD2B bromodomains selectively recognize distinct patterns of acetylated lysine residues on the N-terminal tails of histone proteins. Adjacent methylation or phosphorylation marks were found to either enhance or weaken the recognition of acetylated lysine by the ATAD2/B bromodomains. Complementary structural studies provide mechanistic insights into how residues within the bromodomain binding pocket coordinate the acetyllysine group in the context of adjacent post- translational modifications. Furthermore, we investigated how sequence changes in amino acids of the histone ligands, either as onco mutations or as histone variants, impact the recognition of an adjacent acetylated lysine residue. In summary, our study highlights how the interplay between multiple combinations of histone modifications influences the reader activity of the ATAD2 and ATAD2B bromodomains, resulting in distinct binding modes of the two bromodomains. KEY POINTSO_LIMultiple independent ATAD2 gene duplication events are evident during metazoan evolution, indicating expansion of functionality in the ATAD2 gene family and suggesting distinct functions for ATAD2 and ATAD2B. C_LIO_LIHigh-resolution structures of the ATAD2 and ATAD2B bromodomains in complex with their histone ligands demonstrate how multiple post-translational modifications are coordinated. C_LIO_LIRecognition of different subsets acetylated histone ligands by the ATAD2 and ATAD2B bromodomains is driven by unique features within the binding pockets of these paralogous proteins. C_LIO_LIOnco-histone mutations and histone variants that change the amino acid sequence of the histone tails modulate the ATAD2 and ATAD2B bromodomain activity. C_LIO_LIThis study demonstrates how the combinatorial activity of multiple post- translational modifications forms a histone code and influences the recognition of acetylated lysine by bromodomain-containing proteins. C_LI

biochemistry↗

bioRxiv2021

Acyl-CoA Thioesterases; a rheostat that controls activated fatty acids modulates dengue virus serotype 2 replication

During infection with dengue viruses (DENVs), the lipid landscape within host cells is significantly altered to assemble membrane platforms that support viral replication and particle assembly. Fatty acyl-CoAs are key intermediates in the biosynthesis of complex lipids that form these membranes. They also function as key signaling lipids in the cell. Here, we carried out loss of function studies on acyl-CoA thioesterases (ACOTs), a family of enzymes that hydrolyze fatty acyl-CoAs to free fatty acids and coenzyme A, to understand their influence on the lifecycle of DENVs. Loss of function of the type I ACOTs 1 (cytoplasmic) and 2 (mitochondrial) together significantly increased DENV serotype 2 (DENV2) viral replication and infectious particle release. However, isolated knockdown of mitochondrial ACOT2 significantly decreased DENV2 protein translation, genome replication, and infectious virus release. Furthermore, loss of ACOT7 function, a mitochondrial type II ACOT, similarly suppressed DENV2. As ACOT1 and ACOT2 are splice variants, these data suggest that location (cytosol and mitochondria, respectively) rather than function of these proteins may account for the differences in DENV2 infection phenotype. Additionally, loss of mitochondrial ACOT2 and ACOT7 expression also altered the expression of several ACOTs located in multiple organelle compartments within the cell highlighting a complex relationship between ACOTs in the DENV2 virus lifecycle.

microbiology↗

bioRxiv2020

Testing evolutionary explanations for the lifespan benefit of dietary restriction in Drosophila melanogaster

Dietary restriction (DR), limiting calories or specific nutrients, extends lifespan across diverse taxa. This lifespan extension has been explained as diet-mediated changes in the trade-off between lifespan and reproduction, with survival favoured with scarce resources. Another evolutionary hypothesis suggests the selective benefit of the response is the maintenance of reproduction. This hypothesis predicts that lifespan extension is a side effect of benign laboratory conditions, where DR individuals are frailer and unable to deal with additional stressors, and thus lifespan extension should disappear under more stressful conditions. We tested this by rearing outbred female Drosophila melanogaster on 10 different protein:carbohydrate diets. Flies were either infected with a bacterial pathogen (Pseudomonas entomophila), injured or unstressed. We monitored lifespan, fecundity and ageing measures. DR extended lifespan and reduced reproduction irrespective of injury and infection. These results do not support lifespan extension under DR being a side effect of benign laboratory conditions.

evolutionary biology↗

bioRxiv2020

Comparison of the knockdown resistance locus (kdr) in Anopheles stephensi, An. arabiensis, and Culex pipiens s.l. suggests differing mechanisms of pyrethroid resistance in east Ethiopia

The malaria vector, Anopheles stephensi, which is typically restricted to South Asia and the Middle East, was recently detected in the Horn of Africa. Controlling the spread of this vector could involve integrated vector control that considers the status of insecticide resistance of multiple vector species in the region. Previous reports indicate that the knockdown resistance mutations (kdr) in the voltage-gated sodium channel (vgsc) are absent in both pyrethroid resistant and sensitive variants of An. stephensi in east Ethiopia but similar information on other vector species in the same areas is limited. In this study, kdr and the neighboring intron was analyzed in An. stephensi, An. arabiensis, and Culex pipiens s. l. collected in east Ethiopia between 2016 and 2017. Sequence analysis revealed that all of Cx. pipiens s.l. (n = 42) and 71.6% of the An. arabiensis (n=67) carried kdr L1014F known to confer target-site pyrethroid resistance. Intronic variation was only observed in An. stephensi (segregating sites = 6, haplotypes = 3) previously shown to have no kdr mutations. In addition, no evidence of non-neutral evolutionary processes was detected at the An. stephensi kdr intron which further supports target-site mechanism not being a major resistance mechanism in this An. stephensi population. Overall, these results suggest differences in evolved mechanisms of pyrethroid/DDT resistance in populations of vector species from the same region. Variation in insecticide resistance mechanisms in East Ethiopian mosquito vectors highlight possible species or population specific biological factors and distinct environmental exposures that shape their evolution.

evolutionary biology↗

bioRxiv2020

Population sequencing data reveal a compendium of mutational processes in human germline

Mechanistic processes underlying human germline mutations remain largely unknown. Variation in mutation rate and spectra along the genome is informative about the biological mechanisms. We statistically decompose this variation into separate processes using a blind source separation technique. The analysis of a large-scale whole genome sequencing dataset (TOPMed) reveals nine processes that explain the variation in mutation properties between loci. Seven of these processes lend themselves to a biological interpretation. One process is driven by bulky DNA lesions that resolve asymmetrically with respect to transcription and replication. Two processes independently track direction of replication fork and replication timing. We identify a mutagenic effect of active demethylation primarily acting in regulatory regions. We also demonstrate that a recently discovered mutagenic process specific to oocytes can be localized solely from population sequencing data. This process is spread across all chromosomes and is highly asymmetric with respect to the direction of transcription, suggesting a major role of DNA damage.

genetics↗