Biology subjects

Wenk, M. R.

Publications and source records attributed to Wenk, M. R..

18 recordsLinked to original sources

bioRxiv2025

MRMhub: one-stop solution for automated processing of large-scale targeted metabolomics data

Data processing and quality control are essential for complex targeted mass spectrometry (MS) assays in large-scale metabolomics studies. However, existing software solutions have significant gaps in robustness and scalability. We report MRMhub, a one-stop solution for streamlined processing of large-scale targeted MS data. MRMhub consists of a novel peak integration engine with unique algorithmic design to address the scalability challenge and a comprehensive collection of post-acquisition data processing and analytical quality control tools. The ensemble facilitates rapid and consistent processing of complex chromatograms, quantification, drift and batch correction, quality assessment and control, feature filtering, and data/workflow sharing and reporting. MRMhub can process data from highly complex assays in population-scale studies within minutes, with full digital footprints warranting reproducibility and traceability. We demonstrate its performance using two large-scale lipidomics data sets. We distribute the source code and data sets freely for community development.

bioinformatics↗

bioRxiv2023

MFSD7c functions as a transporter of choline at the blood-brain barrier

Mutations of MFSD7c (also known as Flvcr2), which is an orphan transporter, are linked to Fowler syndrome 1, 2. Here, we use Mfsd7c knockout mice and cell-based assays to reveal that MFSD7c is a choline transporter at the blood-brain barrier (BBB). We performed comprehensive metabolomics and detected differential changes of metabolites in the brains and livers of Mfsd7c knockout (Mfsd7c-/-) embryos. Particularly, we found that choline-related metabolites were altered in the brains but not in the livers of Mfsd7c-/- embryos. Thus, we hypothesized that MFSD7c regulates the levels of choline in the brain. Indeed, expression of human MFSD7c in cells significantly increased choline uptake. Interestingly, we showed that choline uptake by MFSD7c is greatly increased by choline-metabolizing enzymes, leading us to demonstrate that MFSD7c is a facilitative transporter of choline. Furthermore, single-cell patch-clamp showed that the import of choline by MFSD7c is electrogenic. Choline transport function of MFSD7c is conserved in vertebrates, but not in yeasts. We show that human MFSD7c is a functional ortholog of HNM1, the yeast choline importer. Employing our transport assays, we showed that several missense mutations of human MFSD7c from Fowler patients had abolished or reduced choline transport activity. Mice lacking Mfsd7c in the CNS endothelial cells suppressed the import of exogenous choline from blood but unexpectedly had increased choline levels in the brain. Stable-isotope tracing study revealed that MFSD7c is required for exporting choline derived from lysophosphatidylcholine (LPC) in the brain. Collectively, our work identifies MFSD7c as a choline transporter at the BBB. This study suggests that defective export of choline in the brain may be a cause of Fowler syndrome.

biochemistry↗

bioRxiv2022

SPNS1 is required for the transport of lysosphingolipids and lysoglycerophospholipids from lysosomes

Accumulation of sphingolipids, especially sphingosines, in the lysosomes is attributed to the pathogenesis of several lysosomal storage diseases. In search for a lysosomal protein that mediates the release of sphingosines, we identified SPNS1 which shares the highest homology to SPNS2, a sphingosine-1-phosphate (S1P) transporter. We generated knockout cells and mice for Spns1 and employed lipidomics and metabolomics to identify SPNS1 ligands. We found that knockouts of Spns1 resulted in the accumulation of sphingolipids, including sphingosines in embryonic brains and cell lines. These results suggest that deficiency of SPNS1 affects the clearance of sphingolipids in lysosomes. Biochemical assays demonstrated that sphingosines released from lysosomes required SPNS1. Furthermore, by performing a comprehensive analysis of metabolites from livers of postnatal Spns1 knockout mice (gSpns1-cKO), we detected a striking accumulation of lysoglycerophospholipids including LPC, LPE, LPG, and lysoplasmalogens. Interestingly, the release of these lysoglycerophospholipids also required SPNS1. Global knockout of Spns1 (gSpns1-KO) resulted in embryonic lethality between E12.5-E13.5 with developmental defects. Postnatal deletion of Spns1 in mice caused lipid accumulation in the lysosomes and pathological conditions reminiscent of lysosomal storage diseases. These results reveal a critical molecular role of SPNS1 as a transporter for lysosphingolipids and lysoglyerophospholipids from the lysosomes and link its physiological functions with lysosomal storage diseases. SignificancePhospholipids, including glycerophospholipids and sphingolipids, are delivered to the lysosomes for recycling. The hydrolysis of these lipids by lysosomal enzymes generates the corresponding lysoglycerophospholipids, such as lysophosphatidylcholine and lysosphingolipids, such as sphingosine, which are believed to be exported out of the lysosomes for recycling in the cytoplasm. However, it is unknown how these lysophospholipids are released from the lysosomes. The current study utilized genetic knockout models in combination with mass spectrometry analysis of complex phospholipids and sphingolipids to characterize the roles of an orphan lysosomal transporter, namely SPNS1. These findings show that deficiency of SPNS1 results in the accumulation of lysophospholipids in cells and animal tissues and that the transporter is required to transport both lysoglycerophospholipids and lysosphingolipids out of the lysosomes. SPNS1 is critical for early development in mice. Ablation of SPNS1 at postnatal life causes pathological conditions reminiscent of lysosomal storage diseases in mice. These findings reveal the molecular functions of SPNS1 as a lysophospholipid transporter and provide a foundation for studying the transport of these lysolipids in lysosomal storage diseases.

biochemistry↗

bioRxiv2022

Depleting cationic lipids involved in antimicrobial resistance drives adaptive lipid remodeling in Enterococcus faecalis

The bacterial cell membrane is an interface for cell envelope synthesis, protein secretion, virulence factor assembly and a target for host cationic antimicrobial peptides (CAMPs). To resist CAMP killing, several Gram-positive pathogens encode the multiple peptide resistance factor (MprF) enzyme that covalently attaches cationic amino acids to anionic phospholipids in the cell membrane. While E. faecalis encodes two mprF paralogs, MprF2 plays a dominant role in conferring resistance to killing by the CAMP human {beta}-defensin 2 (hBD-2) in E. faecalis strain OG1RF. The goal of the current study is to understand the broader lipidomic and functional roles of E. faecalis mprF. We analyzed the lipid profiles of parental wild type and mprF mutant strains and show that while {triangleup}mprF2 and {triangleup}mprF1 {triangleup}mprF2 mutants completely lacked cationic lysyl-phosphatidylglycerol (L-PG), the {triangleup}mprF1 mutant synthesized [~]70% of L-PG compared to the parent. Unexpectedly, we also observed a significant reduction of PG in {triangleup}mprF2 and {triangleup}mprF1 {triangleup}mprF2. In the mprF mutants, particularly {triangleup}mprF1 {triangleup}mprF2, the decrease in L-PG and PG is compensated by an increase in the phosphorus-containing lipid, GPDGDAG, and D-ala-GPDGDAG. These changes were accompanied by a downregulation of de novo fatty acid biosynthesis and an accumulation of long-chain acyl-acyl carrier proteins (long-chain acyl-ACPs), suggesting that the suppression of fatty acid biosynthesis was mediated by the transcriptional repressor FabT. Growth in chemically defined media lacking fatty acids revealed severe growth defects in the {triangleup}mprF1 {triangleup}mprF2 mutant strain, but not the single mutants, which was partially rescued through supplementation with palmitic and stearic acids. Changes in lipid homeostasis correlated with lower membrane fluidity, impaired protein secretion, and increased biofilm formation in both {triangleup}mprF2 and {triangleup}mprF1 {triangleup}mprF2, compared to wild type and {triangleup}mprF1. Collectively, our findings reveal a previously unappreciated role for mprF in global lipid regulation and cellular physiology, which could facilitate the development of novel therapeutics targeting MprF. Significance StatementThe cell membrane plays a pivotal role in protecting bacteria against external threats, such as antibiotics. Cationic phospholipids such as lysyl-phosphatidyglycerol (L-PG) resist the action of cationic antimicrobial peptides through electrostatic repulsion. Here we demonstrate that L-PG depletion has several unexpected consequences in Enterococcus faecalis, including a reduction of phosphatidylglycerol (PG), enrichment of a phosphorus-containing lipid, reduced fatty acid synthesis accompanied by an accumulation of long-chain acyl-acyl carrier proteins (long chain acyl-ACPs), lower membrane fluidity, and impaired secretion. These changes are not deleterious to the organism as long as exogenous fatty acids are available for uptake from the culture medium. Our findings suggest an adaptive mechanism involving compensatory changes across the entire lipidome upon removal of a single phospholipid modification. Such adaptations must be considered when devising antimicrobial strategies that target membrane lipids.

microbiology↗

bioRxiv2022

Restoration of PITPNA in Type 2 diabetic human islets reverses pancreatic beta-cell dysfunction

Defects in insulin processing and granule maturation are linked to pancreatic beta-cell failure during type 2 diabetes (T2D). Phosphatidylinositol transfer protein alpha (PITPNA) stimulates activity of phosphatidylinositol (PtdIns) 4-OH kinase to produce sufficient PtdIns-4-phosphate (PtdIns-4-P) in the trans-Golgi network to promote insulin granule maturation. PITPNA in beta-cells of T2D human subjects is markedly reduced suggesting its depletion accompanies beta-cell dysfunction. Conditional deletion of Pitpna in the beta-cells of Ins-Cre;Pitpnaflox/flox mice leads to hyperglycemia resulting from decreased glucose-stimulated insulin secretion (GSIS) and reduced pancreatic beta-cell mass. Furthermore, PITPNA silencing in human islets confirmed its role in PtdIns-4-P synthesis and led to impaired insulin granule maturation and docking, GSIS, and proinsulin processing with evidence of ER stress. Restoration of PITPNA in islets of T2D human subjects reversed these beta-cell defects and identify PITPNA as a critical target linked to beta-cell failure in T2D.

cell biology↗

bioRxiv2022

Diacylglycerol consumption at the inner nuclear membrane fuels nuclear envelope expansion required for closed mitosis

Nuclear envelope (NE) expansion must be controlled to maintain nuclear shape and function. The nuclear membrane expands massively during closed mitosis, enabling chromosome segregation within an intact NE. Phosphatidic acid (PA) and diacylglycerol (DG) can both serve as biosynthetic precursors for membrane lipid synthesis. How they are regulated in time and space and what are the implications of changes in their flux for mitotic fidelity is largely unknown. Using genetically encoded PA and DG probes, we show that DG is depleted from the inner nuclear membrane during mitosis in the fission yeast Schizosaccharomyces pombe, but PA does not accumulate, indicating that it is rerouted to membrane synthesis. We demonstrate that DG-to-PA conversion catalysed by the diacylglycerol kinase Dgk1 and direct glycerophospholipid synthesis from DG by diacylglycerol cholinephosphotransferase / ethanolaminephosphotransferase Ept1 reinforce NE expansion. We conclude that DG consumption through both de novo and the Kennedy pathways fuels a spike in glycerophospholipid biosynthesis, controlling NE expansion, and ultimately, mitotic fidelity.

cell biology↗

bioRxiv2021

Mfsd2b and Spns2 are essential for maintenance of blood vessels during development and protection of anaphylaxis

Sphingosine-1-phosphate (S1P) is a potent lipid mediator that is secreted by several cell types to induce signaling. We recently showed that Mfsd2b is an S1P transporter from hematopoietic cells, which contributes approximately 50% plasma S1P. To further determine the sources of plasma S1P, here, we report the characterizations of compound deletions of Mfsd2b and Spns2, another S1P transporter from endothelial cells. Global deletion of Mfsd2b and Spns2 (gDKO) resulted in embryonic lethality between E13.5 and E14.5 with severe hemorrhage that largely recapitulated the phenotypes from global S1P1 knockout mice, indicating that together with Mfsd2b, Spns2 also provides embryonic source of S1P for S1P1 stimulation. The hemorrhagic phenotypes in gDKO embryos were accompanied by increased angiogenesis and defects of tight junction proteins, indicating that S1P from Mfsd2b and Spns2 is essential for blood vessel integrity and maturation. The various sources of S1P in postnatal stages are yet to be fully understood. Postnatal ablation of S1P synthesis enzymes using Mx1Cre shows that Mx1Cre-sensitive cells provide most of plasma S1P. Interestingly, we showed that compound postnatal deletion of Mfsd2b and Spns2 using Mx1Cre (ctDKO-Mx1Cre) resulted in maximal reduction of 80% plasma S1P. Thus, a small amount of plasma S1P is supplied from other sources independent of Mfsd2b and Spns2. Nevertheless, the vasculature in the lung of ctDKO-Mx1Cre mice was compromised. Furthermore, ctDKO-Mx1Cre mice also exhibited severe susceptibility to anaphylaxis, indicating that S1P from Mfsd2b and Spns2 is indispensable during vascular stress. Together, our results show that Mfsd2b and Spns2 provide a critical source of S1P for embryonic development and they also provide a majority of plasma S1P for vascular homeostasis.

molecular biology↗

bioRxiv2021

Developmental and Intergenerational Landscape of Human Circulatory Lipidome and its Association with Obesity Risk

Lipids play a vital role in human health and development, but changes to their circulatory levels during gestation and in early life are poorly understood. Here we present the first developmental and intergenerational landscape of the human circulatory lipidome, derived by profiling of 480 lipid species representing 25 lipid classes, in mothers and their offspring (n=2491). Levels of 66% of the profiled lipids increased in maternal circulation during gestation, while cord blood had higher concentrations of acylcarnitines and lysophospholipids. The offspring lipidome at age six years revealed striking similarities with postnatal maternal lipidome (adult) in its lipid composition and concentrations. Comparison of lipids associated with child and maternal adiposity identified a 92% overlap, implying intergenerational similarities in the lipid signatures of obesity risk. We also catalogued lipid signatures linked with maternal adiposity during gestation and offspring birthweight, and validated (>70% overlap) the findings in an independent birth-cohort (n=1935).

systems biology↗

bioRxiv2021

Destabilization of β-cell FIT2 by saturated fatty acids contribute to ER stress and diabetes

Western type diets are linked to obesity and diabetes partly because of their high saturated fatty acid (SFA) content. We found that SFAs, but not unsaturated fatty acids (USFAs), reduced the number of lipid droplets (LDs) within pancreatic {beta}-cells. Mechanistically, SFAs but not USFAs disabled LD biogenesis by inducing palmitoylation and subsequent ERAD-C mediated degradation of LD formation protein, Fat storage-Inducing Transmembrane protein 2 (FIT2). Targeted ablation of FIT2 reduced {beta}-cell LD numbers, lowered {beta}-cell ATP levels, reduced Ca2+ signaling, downregulated {beta}-cell transcription factors (RNA sequencing analysis), and exacerbated diet-induced diabetes in mice. Subsequent mass spectrometry studies revealed increased C16:0 ceramide accumulation in islets of mice lacking {beta}-cell FIT2 under lipotoxic conditions. Inhibition of ceramide synthases ameliorated the enhanced ER stress. Overexpression of FIT2 increased number of intracellular LDs and rescued SFA-induced ER-stress and apoptosis thereby highlighting the protective role of FIT2 and LDs against {beta}-cell lipotoxicity and diet-induced diabetes.

biochemistry↗

bioRxiv2021

The composition and function of Enterococcus faecalismembrane vesicles

Membrane vesicles (MVs) contribute to various biological processes in bacteria, including virulence factor delivery, host immune evasion, and cross-species communication. MVs are frequently being discharged from the surface of both Gram-negative and Gram-positive bacteria during growth. In some Gram-positive bacteria, genes affecting MV biogenesis have been identified, but the mechanism of MV formation is unknown. In Enterococcus faecalis, a causative agent of life-threatening bacteraemia and endocarditis, neither mechanisms of MV formation nor their role in virulence has been examined. Since MVs of many bacterial species are implicated in host-pathogen interactions, biofilm formation, horizontal gene transfer, and virulence factor secretion in other species, we sought to identify, describe, and functionally characterize MVs from E. faecalis. Here we show that E. faecalis releases MVs that possess unique lipid and protein profiles, distinct from the intact cell membrane, and are enriched in lipoproteins. MVs of E. faecalis are specifically enriched in unsaturated lipids that might provide membrane flexibility to enable MV formation, providing the first insights into the mechanism of MV formation in this Gram-positive organism.

microbiology↗

bioRxiv2020

FasR regulates fatty acid biosynthesis and is essential for virulence of Mycobacterium tuberculosis

Mycobacterium tuberculosis, the etiologic agent of human tuberculosis, is the worlds leading cause of death from an infectious disease. One of the main features of this pathogen is the complex and dynamic lipid composition of the cell envelope, which adapts to the variable host environment and defines the fate of infection by actively interacting with and modulating immune responses. However, while much has been learned about the enzymes of the numerous lipid pathways, little knowledge is available regarding the proteins and metabolic signals regulating lipid metabolism during M. tuberculosis infection. In this work, we constructed and characterized a FasR-deficient mutant in M. tuberculosis and demonstrated that FasR positively regulates fas and acpS expression. Lipidomic analysis of the wild type and mutant strains revealed complete rearrangement of most lipid components of the cell envelope, with phospholipids, mycolic acids, sulfolipids and phthiocerol dimycocerosates relative abundance severely altered. As a consequence, replication of the mutant strain was impaired in macrophages leading to reduced virulence in a mouse model of infection. Moreover, we show that the fasR mutant resides in acidified cellular compartments, suggesting that the lipid perturbation caused by the mutation prevented M. tuberculosis inhibition of phagolysosome maturation. This study identified FasR as a novel factor involved in regulation of mycobacterial virulence and provides evidence for the essential role that modulation of lipid homeostasis plays in the outcome of M. tuberculosis infection.

microbiology↗

bioRxiv2020

The bacterial quorum sensing signal DSF hijacks Arabidopsis thaliana sterol biosynthesis to suppress plant innate immunity

Quorum sensing (QS) is a recognized phenomenon that is crucial for regulating population-related behaviors in bacteria. However, the direct specific effect of QS molecules on host biology is largely under-studied. In this work, we show that the QS molecule DSF (cis-11-methyl-dodecenoic acid) produced by Xanthomonas campestris pv. campestris can suppress pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) in Arabidopsis thaliana, mediated by flagellin-induced activation of flagellin receptor FLS2. The DSF-mediated attenuation of innate immunity results from the alteration of oligomerization states and endocytic internalization of plasma membrane FLS2. DSF altered the lipid profile of Arabidopsis, with a particular increase of the phytosterol species, which impairs the general endocytosis pathway mediated by clathrin and FLS2 nano-clustering on the plasma membrane. The DSF effect on receptor dynamics and host immune responses could be entirely reversed by sterol removal. Together, our results highlighted the importance of sterol homeostasis to plasma membrane organization and demonstrate a novel mechanism by which pathogenic bacteria use their communicating molecule to manipulate PAMP-triggered host immunity. SIGNIFICANCE STATEMENTBacteria rely on small signalling molecules called quorum sensing (QS) signals to communicate and coordinate their behaviors. QS is known to regulate gene expression, production of virulence factors, and biofilm formation for pathogenic bacteria to effectively colonize their hosts and cause diseases. In this work, we found a class of QS molecule called diffusible-signal factor (DSF), produced by devastating phytopathogenic bacteria such as Xanthomonas spp. and Xylella fastidiosa, could communicate directly with plant host and subvert plant innate immunity by inducing plant sterol production and thereby, attenuating receptor signalling through hindering the receptor clustering and plant endocytosis. The results significantly enrich our understanding of the mechanisms in the tug-of-war between bacterial pathogenesis and host immunity.

plant biology↗

bioRxiv2019

Concurrent lipidomics and proteomics on malignant plasma cells from multiple myeloma patients: Probing the lipid metabolome

BackgroundMultiple myeloma (MM) is a hematological malignancy characterized by the clonal expansion of malignant plasma cells. Though durable remissions are possible, MM is considered incurable, with relapse occurring in almost all patients. There has been limited data reported on the lipid metabolism changes in plasma cells during MM progression. Here, we evaluated the feasibility of concurrent lipidomics and proteomics analyses from patient plasma cells, and report these data on a limited number of patient samples, demonstrating the feasibility of the method, and establishing hypotheses to be evaluated in the future. MethodsPlasma cells were purified from fresh bone marrow aspirates using CD138 microbeads. Proteins and lipids were extracted using a bi-phasic solvent system with methanol, methyl tert-butyl ether, and water. Untargeted proteomics, untargeted and targeted lipidomics were performed on 7 patient samples using liquid chromatography-mass spectrometry. Two comparisons were conducted: high versus low risk; relapse versus newly diagnosed. Proteins and pathways enriched in the relapsed group was compared to a public transcriptomic dataset from Multiple Myeloma Research Consortium reference collection (n=222) at gene and pathways level. ResultsFrom one million purified plasma cells, we were able to extract material and complete untargeted ([~]6000 and [~]3600 features in positive and negative mode respectively) and targeted lipidomics (313 lipids), as well as untargeted proteomics analysis ([~]4100 reviewed proteins). Comparative analyses revealed limited differences between high and low risk groups (according to the standard clinical criteria), hence we focused on drawing comparisons between the relapsed and newly diagnosed patients. Untargeted and targeted lipidomics indicated significant down-regulation of phosphatidylcholines (PCs) in relapsed MM. Although there was limited overlap of the differential proteins/transcripts, 76 significantly enriched pathways in relapsed MM were common between proteomics and transcriptomics data. Further evaluation of transcriptomics data for lipid metabolism network revealed enriched correlation of PC, ceramide, cardiolipin, arachidonic acid and cholesterol metabolism pathways to be exclusively correlated among relapsed but not in newly-diagnosed patients. ConclusionsThis study establishes the feasibility and workflow to conduct integrated lipidomics and proteomics analyses on patient-derived plasma cells. Potential lipid metabolism changes associated with MM relapse warrant further investigation.

systems biology↗

bioRxiv2019

Metabolic stress is a primary pathogenic event in transgenic Caenorhabditis elegans expressing neuronal human amyloid-β

Alzheimers disease (AD) is the most common neurodegenerative disease affecting the elderly worldwide. Mitochondrial dysfunction has been proposed as a key event in the etiology of AD. We have previously modeled amyloid-beta (A{beta})-induced mitochondrial dysfunction in a transgenic Caenorhabditis elegans strain by expressing human A{beta} peptide specifically in neurons (GRU102). Here, we focus on a deeper analysis of these metabolic changes associated with A{beta}-induced mitochondrial dysfunction. Integrating metabolomics, transcriptomics, biochemical studies and computational modeling, we identify alterations in Tricarboxylic Acid (TCA) cycle metabolism following even low-level A{beta} expression. In particular, GRU102 show reduced activity of a rate-limiting TCA cycle enzyme, alpha-ketoglutarate dehydrogenase. These defects are associated with elevation of protein carbonyl content specifically in mitochondria. Importantly, metabolic failure occurs before any significant increase in global protein aggregate is detectable. Treatment with an antidiabetes drug, Metformin, reverses A{beta}-induced metabolic defects, reduces protein aggregation and normalizes the lifespan of GRU102. Our results point to metabolic dysfunction as an early and causative event in AD pathology and a promising target for intervention.

neuroscience↗

bioRxiv2019

Long acyl chain ceramides govern cholesterol and cytoskeleton dependence of membrane outer leaflet dynamics

The cellular plasma membrane composition and organization is crucial for the regulation of biological processes. Based on our earlier work showing that the same lipid probe, DiI, exhibits different dynamics in CHO-K1 and RBL-2H3 cells, we investigate the molecular factors that govern these differences. First, we determined that the cytoskeleton-interacting Immunoglobulin E receptor (Fc{varepsilon}RI), which is abundant in RBL-2H3 but not in CHO-K1 cells, is not responsible for the DiI confinement found in RBL-2H3 cells. Second, lipid mass spectrometry of the plasma membrane of the two cells indicated differences in ceramide content, especially with long and very long acyl chains (C16 to C24). We, therefore, measure membrane dynamics by imaging total internal reflection fluorescence correlation spectroscopy in dependence on these ceramides. Our results show that C24 and C16 saturated ceramides uniquely alter the membrane dynamics by promoting the formation of cholesterol-independent domains and by elevating inter-leaflet coupling.

biophysics↗

bioRxiv2018

Step-wise evolution of temperature-mediated phenotypic plasticity in eyespot size across nymphalid butterflies

There are two disparate views regarding phenotypic plasticity. One regards plasticity as a derived adaptation to help organisms survive in variable environments1, 2 while the other views plasticity as the outcome of flexible, non-canalized, developmental processes, ancestrally present in most organisms, that helps them colonize or adapt to novel environments3-5 e.g., a pre-adaptation. Both views of plasticity currently lack a rigorous, mechanistic examination of ancestral and derived states and direction of change2. Here we show that the origin of phenotypic plasticity in eyespot size in response to environmental temperature observed in Bicyclus anynana butterflies is a derived adaptation of this lineage. Eyespot size is regulated by temperature-mediated changes in levels of a steroid hormone, 20E, that affects proliferation of eyespot central cells expressing the 20E receptor (EcR)6, 7. By estimating the origin of the known physiological and molecular components of eyespot size plasticity in a comparative framework, we showed that 20E titer plasticity in response to temperature is a pre-adaptation shared by all butterfly species examined, whereas the origin of expression of EcR in eyespot centers, and the origin of eyespot sensitivity to the hormone-receptor complex are both derived traits found only in a subset of species with eyespots. The presence of all three molecular components required to produce a plastic response is only observed in B. anynana. This gradual, step-wise, physiological/molecular response to temperature is a likely adaptation to temperature variation experienced across wet and dry seasons in the habitat of this species. This work supports, thus, the first view of plasticity as a derived adaptation.

evolutionary biology↗

bioRxiv2017

Slowing ageing using drug synergy in C. elegans

Pharmacological interventions that target human ageing would extend individual healthspan and result in dramatic economic benefits to rapidly ageing societies worldwide. For such interventions to be contemplated they need to comprise drugs that are efficacious when given to adults and for which extensive human safety data are available. Here we show that dramatic lifespan extension can be achieved in C.elegans by targeting multiple, evolutionarily conserved ageing pathways using drugs that are already in human use. By targeting multiple synergistic ageing pathways, we are able to slow ageing rate, double lifespan and improves healthspan while minimize developmental and fitness trade-offs. Moreover, we established that there is no synergistic benefit in a daf-2 or daf-7 background, implying the involvement of the TGF{beta} and IGF pathways in this synergy. Employing lipidomics and transcriptomics analysis we found lipid metabolism to be affected resulting in increased monounsaturated fatty acids (MUFA) and decrease membrane peroxidation index. Our best drug combination showed a conserved lifespan extension in fruit flies. To the best of our knowledge, this is the largest lifespan effect ever reported for any adult-onset drug treatment in C. elegans. This drug-repurposing approach, using drugs already approved for humans to target multiple conserved aging pathways simultaneously, could lead to interventions that prevent age-related diseases and overall frailty in a rapidly ageing population.

biochemistry↗

bioRxiv2017

Sex Differences In 20-Hydroxyecdysone Hormone Levels Control Sexual Dimorphism In Bicyclus anynana Butterfly Wing Patterns

In contrast to the important role of hormones in the development of sexual dimorphic traits in vertebrates [1], the differentiation of these traits in insects is attributed exclusively to variation in cell-autonomous mechanisms controlled by members of the sex determination pathway [2], such as doublesex (dsx). Although hormones can shape the development of sexual traits in insects, and interact with dsx to create dimorphisms, variation in hormone levels are not known to cause dimorphism in these traits [3]. Here we show that butterflies use sex-specific differences in 20-hydroxyecdysone (20E) hormone titers to create sexually dimorphic wing ornaments, without the local involvement of dsx. Females of the dry season (DS) form of Bicyclus anynana display a larger sexual ornament on their wings than males, whereas in the wet season (WS) form both sexes have similarly sized ornaments [4]. High levels of circulating 20E during larval development in DS females and WS forms cause proliferation of the cells fated to give rise to this wing ornament, and results in sexual dimorphism in the DS forms. This study advances our understanding of how the environment regulates sex-specific patterns of plasticity of sexual ornaments and conclusively shows that sex-specific variation in hormone titers can play a role in the development of secondary sexual traits in insects, just like they do in vertebrates.\n\nHighlights O_LISex-specific levels of 20E, an insect molting hormone, regulate secondary sexual trait dimorphism and plasticity in butterflies.\nC_LIO_LI20E levels above a threshold promote local patterns of cell division in one sex, but not in the other sex, to create sexually dimorphic eyespots.\nC_LI\n\neTOCSexual selection drives the evolution of ornaments for individuals to display to the opposite sex. Yet, the mechanisms by which sexual selection operates are still not well understood. Here Bhardwaj et al. provide conclusive evidence, for the first time, that male and female insects use variation in levels of hormones to create dimorphism in their sexual ornaments. Authors show that 20-hydroxyecdyone, the insect molting hormone, also functions as a sex hormone in a butterfly. They also show how the environment shapes the development of sexual ornaments at a proximate level.

developmental biology↗