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Introduction
Our research aims to understand the molecular nuts and bolts of how early-life environmental stresses alter gene expression, metabolism and physiology. The laboratory makes extensive use of the genetic model organism Drosophila as well as other models. We employ a range of different technologies, including genetics to find out how genes work, and mass spectrometry imaging to see where metabolites are located inside cells and organs.
Additional affiliations
July 2012 - March 2015
January 1998 - June 2012
January 1992 - December 1997
Publications
Publications (129)
Artificial sweeteners are used as calorie-free sugar substitutes in many food products and their consumption has increased substantially over the past years¹. Although generally regarded as safe, some concerns have been raised about the long-term safety of the consumption of certain sweeteners2–5. In this study, we show that the intake of high dose...
Background: Maternal malnutrition can lead to fetal growth restriction. This is often associated with organ sparing and long-lasting physiological dysfunctions during adulthood, although the underlying mechanisms are not yet well understood.
Methods: Low protein (LP) dietary models in C57BL/6J mice were used to investigate the proximal effects of m...
Lipid droplets are highly dynamic intracellular organelles that store neutral lipids such as cholesteryl esters and triacylglycerols. They have recently emerged as key stress response components in many different cell types. Lipid droplets in the nervous system are mostly observed in vivo in glia, ependymal cells and microglia. They tend to become...
Glioblastoma is thought to originate from neural stem cells (NSCs) of the subventricular zone that acquire genetic alterations. In the adult brain, NSCs are largely quiescent, suggesting that deregulation of quiescence maintenance may be a pre-requisite for tumour initiation. Although inactivation of the tumour suppressor p53 is a frequent event in...
Background: Maternal malnutrition can lead to fetal growth restriction. This is often associated with organ sparing and long-lasting physiological dysfunctions during adulthood, although the underlying mechanisms are not yet well understood.
Methods: Low protein (LP) dietary models in C57BL/6J mice were used to investigate the proximal effects of m...
There is an increasing appreciation for the role of metabolism in cell signaling and cell decision making. Precise metabolic control is essential in development, as evident by the disorders caused by mutations in metabolic enzymes. The metabolic profile of cells is often cell‐type specific, changing as cells differentiate or during tumorigenesis. R...
Obesity-related renal lipotoxicity and chronic kidney disease (CKD) are prevalent pathologies with complex aetiologies. One hallmark of renal lipotoxicity is the ectopic accumulation of lipid droplets in kidney podocytes and in proximal tubule cells. Renal lipid droplets are observed in human CKD patients and in high-fat diet (HFD) rodent models, b...
Obesity-related renal lipotoxicity and chronic kidney disease (CKD) are prevalent pathologies with complex aetiologies. One hallmark of renal lipotoxicity is the ectopic accumulation of lipid droplets in kidney podocytes and in proximal tubule cells. Renal lipid droplets are observed in human CKD patients and in high-fat diet rodent models but thei...
Cryogenic OrbiSIMS decreases molecular fragmentation and expands the chemical space that is amenable to mass spectrometry imaging with high spatial and mass resolution. Semi‐volatile and non‐volatile molecules can now be imaged simultaneously in biological tissues.
Abstract
OrbiSIMS is a recently developed instrument for label‐free imaging of chem...
OrbiSIMS is a recently developed instrument for label‐free imaging of chemicals with micron spatial resolution and high mass resolution. We report a cryogenic workflow for OrbiSIMS (Cryo‐OrbiSIMS) that improves chemical detection of lipids and other biomolecules in tissues. Cryo‐OrbiSIMS boosts ionization yield and decreases ion‐beam induced fragme...
OrbiSIMS is a recently developed instrument for label-free imaging of chemicals with micron spatial resolution and high mass resolution. Here we report a cryogenic workflow for OrbiSIMS (Cryo-OrbiSIMS) that improves chemical detection of lipids and other biomolecules in tissues. Cryo-OrbiSIMS decreases ion-beam induced fragmentation, allowing large...
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Rewired metabolism of glutamine in cancer has been well documented, but less is known about other amino acids such as histidine. Here, we use Drosophila cancer models to show that decreasing the concentration of histidine in the diet strongly inhibits the growth of mutant clones induced by loss of Nerfin-1 or gain of Notch activity. In contrast, ch...
The measurement of absolute metabolite concentrations in small samples remains a significant analytical challenge. This is particularly the case when the sample volume is only a few microlitres or less and cannot be determined accurately via direct measurement. We previously developed volume determination with two standards (VDTS) as a method to ad...
The confusingly named growth-blocking peptides are nutrient-dependent adipokines that stimulate insulin secretion and boost growth in developing flies. In this issue of Developmental Cell, Meschi et al. (2018) show that these adipose tissue-derived factors regulate insulin secretion by silencing a pair of inhibitory neurons that synapse with insuli...
Sexual size dimorphism (SSD), a sex difference in body size, is widespread throughout the animal kingdom, raising the question of how sex influences existing growth regulatory pathways to bring about SSD. In insects, somatic sexual differentiation has long been considered to be controlled strictly cell-autonomously. Here, we discuss our surprising...
Environmental stresses experienced during development exert many long-term effects upon health and disease. For example, chemical oxidants or genetic perturbations that induce low levels of reactive oxygen species can extend lifespan in several species. In some cases, the beneficial effects of low-dose oxidants are attributed to adaptive protective...
Early-life nourishment exerts long-term influences upon adult physiology and disease risk. These lasting effects of diet are well established but the underlying mechanisms are only partially understood. Here we show that restricting dietary yeast during Drosophila development can, depending upon the subsequent adult environment, more than double me...
Sexual dimorphisms in body size are widespread throughout the animal kingdom but their underlying mechanisms are not well characterized. Most models for how sex chromosome genes specify size dimorphism have emphasized the importance of gonadal hormones and cell-autonomous influences in mammals versus strictly cell-autonomous mechanisms in Drosophil...
Mid-L2 and early-L3 larvae show no sex differences in insulin signalling.
(A-B) Immunostaining for Ilp2 levels in insulin producing cells (IPCs) in mid-L2 (A) and early L3 (B) larvae. Ilp2 quantifications show mean, SD and individual data points for each CNS (see Materials and methods). C) Western blot for phospho-Akt, Akt and tubulin in whole body...
Sxl knockdown in oenocytes or midgut does not affect female body size and SSD.
(A) Body mass of wandering L3 larvae expressing Sxl RNAi in oenocytes using PromE-Gal4. Graph shows mean, SD and individual data points. (B) Body mass of wandering L3 larvae expressing Sxl RNAi in midgut enterocytes using Mex1-Gal4. Graph shows mean body mass and SD for...
Loss of neuronal Sxl expression following knockdown of Sxl and msl-2 or Sxl alone.
(A) Sxl immunostaining in the early L3 thoracic ventral nerve cord of control, elavc155>Sxl RNAi and and elavc155>Sxl RNAi + msl-2 RNAi larvae. DNA is labelled by DAPI. (B) Quantification of Sxl expression (mean signal intensity) in regions of interest similar to tho...
Expression patterns of Ilp2-Gal4 and Ilp2-lexA drivers used in this study.
Confocal Z-projections of the CNSs from female late L3 larvae showing expression of membrane-targeted GFP (UAS-CD8::GFP or lexAOP-CD2::GFP) in green and DNA stained by DAPI in blue. Ilp2-Gal4 and Ilp215-1-Gal4 are weakly active in some neurons of the ventral nerve cord (VNC)...
Restoration of Sxl in IPCs rescues the SSD phenotype of Ilp2>Sxl RNAi larvae.
(A-C) Single confocal sections through clusters of IPCs from female larvae, immunostained for Sxl and Ilp2 (to mark IPCs), with DNA stained by DAPI (blue). Sxl in the nuclei of IPCs is strongly expressed in control females (A) but absent in those of Ilp2-Gal4>UAS-Sxl RNAi...
Sxl, tra and tra-2 manipulations in the fat body have minor effects on female body size and SSD.
(A-B) Body mass of wandering L3 larvae expressing tra RNAi in the fat body using Cg-Gal4. (A) shows mean body mass per larva in mg (weighed in groups of n = 6–14 larvae) and (B) shows mean body mass and SD of individually weighed larvae (n = 27–30 larva...
Neuronal knockdown of Sxl abolishes the establishment of larval body SSD.
(A) Body mass of control and elavc155>Sxl RNAi 1 larvae at 3-24h after synchronization at the L1/L2 molt. Early L3 occurs at ~24h after L1/L2 molt. Mean body mass and SD was measured for replicate groups of 3–6 larvae (3h, 6h and 11h time points) or for individual larvae (18h...
Sxl does not function in glia to control larval body SSD.
(A) Confocal image projection of a late third instar larval CNS, with elavc155-Gal4-expressing cells permanently marked with GFP (green) and glial cells stained by anti-Repo antibody (red). There is no detectable overlap between elavc155-Gal4 driver activity and Repo signal. (B) Confocal ima...
amon386Y-Gal4 and VGAT-Gal4 but not Gad1-Gal4 are expressed in IPCs.
Confocal Z-projections of CNSs from late L3 larvae. UAS-CD8::GFP expression reveals that amon386Y-Gal4 (A) and VGAT-Gal4 (B) but not Gad1-Gal4 (C) are expressed in IPCs (marked by anti-Ilp2 immunostaining, Ilp2 also marks IPC projections in the corpora cardiaca of the ring gland,...
Cell-autonomous SSD contributions of Sxl and tra in the wing imaginal disc and larval fat body.
(A-B) nubbin-Gal4 driving expression of UAS-Sxl RNAi 1, UAS-tra RNAi 1, UAS-TraF or UAS-InR RNAi decreases the SSD of the wing pouch. Gal4-expressing cells in the wing pouch were marked by UAS-RFP. To measure cell-autonomous effects, the mean ratios and...
Underlying data for main and supporting figures.
In this Excel file, separate worksheets contain the data used in each figure panel as indicated.
(XLSX)
SSD screen of Gal4 drivers using UAS-Sxl RNAi.
Females of the genotype UAS-Sxl RNAi 1/CyO, Dfd-YFP; UAS-Dcr2 were crossed to control or Gal4 driver males but, for Gal4 drivers located on the X-chromosome, the cross was reversed. Wandering L3 larvae were sorted by sex and YFP expression into UAS-Sxl RNAi 1versus CyO, Dfd-YFP genotypes. Mean body mas...
Expression patterns of the Gad1-GAL4 and VGAT-GAL4 drivers in this study.
Confocal Z-projections of the CNSs from late L3 larvae showing Gad1-GAL4 (A) or VGAT-GAL4 (B) driving expression of membrane-targeted GFP (UAS-CD8::GFP) in green. DNA is stained by DAPI in blue.
(TIF)
SSD phenotypes of Sxl knockdown with Ilp215-1-Gal4, VGAT-Gal4 or amon386Y-Gal4 are not altered by blocking Gal4 activity in VNC neurons with tsh-Gal80.
(A) CNS expression patterns in female larvae at late L3 of Ilp215-1-Gal4, VGAT-Gal4 or amon386Y-Gal4 driving UAS-CD8::GFP (green) in the absence (left) or presence (right) of tsh-Gal80. All images s...
Male and female larvae differ in absolute but not mass-specific food intake.
Absolute (per larva) and mass-specific (per mg of larval body mass) food intake in early L2 and early L3 larvae, measured during 20 min (early L2) or 25 min (early L3) in groups of 9–20 larvae. Graphs plot mean, SD and data points for individual replicates. P-values are sh...
Expression patterns of Gal4 drivers.
Expression patterns were examined in late L3 larvae, with Gal4 drivers activating the expression of UAS-CD8::GFP. For elavc155-Gal4, expression was examined using act>stop>Gal4, UAS-GFP/GlaBc; UAS-Flp/TM6 to permanently label Gal4-expressing cells. An X or listed structures indicates expression present in some o...
IPC and Ilp manipulations affecting Insulin signalling do not alter larval body SSD.
(A) IPC overexpression of UAS-Ilp2 or UAS-Ilp5 using a combination of Ilp2-GAL4 + Ilp215-3-Gal4 has no effect on body size or SSD. (B) IPC inhibition of PI3K signalling (UAS-p60 driven by Ilp2-GAL4 + Ilp215-3-Gal4) reduces body size in both males and females but it...
Female-biased expression of dmyc is maintained in elavc155>Sxl RNAi larvae.
Graph shows qPCR quantitation of dmyc transcript levels from whole early L3 larvae, normalised to the geometric mean of tubulin and RNA polymerase II transcript levels. Individual data points are shown for replicates normalised to the mean female value for each genotype and...
Lipid droplets are cytoplasmic organelles that store neutral lipids and are critically important for energy metabolism. Their function in energy storage is firmly established and increasingly well characterized. However, emerging evidence indicates that lipid droplets also play important and diverse roles in the cellular handling of lipids and prot...
Metabolic pathway flux is a fundamental element of biological activity, which can be quantified using a variety of mass spectrometric techniques to monitor incorporation of stable isotope-labelled substrates into metabolic products. This article contrasts developments in electrospray ionisation mass spectrometry (ESI-MS) for the measurement of lipi...
Cell growth and proliferation depend upon many different aspects of lipid metabolism. One key signaling pathway that is utilized in many different anabolic contexts involves Phosphatidylinositide 3-kinase (PI3K) and its membrane lipid products, the Phosphatidylinositol (3,4,5)-trisphosphates. It remains unclear, however, which other branches of lip...
NR represses PI3K signaling more strongly in fat body than oenocytes.
Panels in top two rows show endogenous FoxO expression in fat body (left) and oenocytes (right, marked with PromE>mGFP) from Fed48 and NR66 larvae. Redistribution of FoxO from the cytoplasm to the nucleus (associated with decreased PI3K signaling) during NR is more pronounced in...
Quantitation of protein knockdowns with Acc, Kar, Cyp4g1 and Cpr RNAi.
(A) Antibody staining for Acc, Kar, Cyp4g1 and Cpr in oenocytes following PromE-GAL4 driven RNAi in NR larvae. Scale bar is 20μm. (B) Staining for Kar in nlsGFP positive Flp-out clones expressing Kar Ri in oenocytes. Scale bar is 10μm. (C) Graph of relative immunostaining intens...
Genetic interactions between FarO and PI3K.
(A) In Fed48 larvae, PromE>Dp110DN induces a low level of oenocyte lipid droplets that are suppressed in PromE>FarO Ri Dp110DN. In NR larvae, PromE>Dp110DN does not noticeably alter lipid droplet induction and thus inhibition of NR droplet induction is similar in PromE>FarO Ri and in PromE>FarO Ri Dp110DN...
FarO and Kar do not limit the size of oenocytes at the late larval stage.
(A) Neither Kar nor FarO RNAi detectably alter lipid droplets in the fat body. Flp-out clones for Kar RNAi (top row) or FarO RNAi (bottom row), marked with nlsGFP, show no detectable change in lipid droplets (LipidTOX), nuclear size or cell size in NR larvae. Nuclei are marke...
Kar but not FarO RNAi significantly increases oenocyte membrane p-Akt.
(A, B) Quantitation of membrane p-Akt intensity, relative to the control genotype, in NR oenocytes expressing FarO RNAi (A) or Kar RNAi (B). Membrane p-Akt intensity increases 1.7 fold with Kar RNAi but does not change significantly with FarO RNAi. (C) Panels show p-Akt staining...
Quantitations of cell size and membrane p-Akt expression.
(A, B) Fat body cell areas in Flp-out clones. Dp110 overexpression increases cell size relative to controls in NR larvae (A) and Dp110DN expression decreases cell size relative to controls in Fed48 larvae (B). (C, D) Quantitation of Oenocyte membrane p-Akt expression. Membrane p-Akt expressi...
Quantitations of neutral lipid content.
The relative lipid contents, calculated from neutral LipidTOX stainings, for experiments shown in the main Figures. (A,B) Flp-out clones in the fat body expressing Dp110 in NR (A) or Dp110DN in Fed48 larvae (B). (C-E) PromE-GAL4 controls in Fed48 and NR larvae (C) and PromE-GAL4 driven expression of Dp110 or...
Ilp6 is not required for NR induction of lipid droplets in larval oenocytes.
Clusters of oenocytes from NR larvae, marked with streptavidin-A555 and showing lipid droplets (LipidTOX) and nuclei (DAPI). (A) Larvae deficient for Ilp6 (Df(1)Ilp6) show lipid droplet induction similar to controls (w1118). (B) Larvae with fat body-specific RNAi knockdown...
Stem cells reside in specialized microenvironments known as niches. During Drosophila development, glial cells provide a niche that sustains the proliferation of neural stem cells (neuroblasts) during starvation. We now find that the glial cell niche also preserves neuroblast proliferation under conditions of hypoxia and oxidative stress. Lipid dro...
Hox genes encode a conserved family of homeodomain transcription factors regulating development along the major body axis. During embryogenesis, Hox proteins are expressed in segment-specific patterns and control numerous different segment-specific cell fates. It has been unclear, however, whether Hox proteins drive the epithelial cell segregation...
Oenocytes have intrigued insect physiologists since the nineteenth century. Many years of careful but mostly descriptive research on these cells highlights their diverse sizes, numbers, and anatomical distributions across Insecta. Contemporary molecular genetic studies in Drosophila melanogaster and Tribolium castaneum support the hypothesis that o...
The accurate measurement of metabolite concentrations in miniscule biological sample volumes is often desirable, yet it remains challenging. In many cases, the starting analyte volumes are imprecisely known, or not directly measurable, and hence absolute metabolite concentrations are difficult to calculate. Here we introduce Volume Determination us...
Cardiomyocytes are vulnerable to hypoxia in the adult, but adapted to hypoxia in utero. Current understanding of endogenous cardiac oxygen sensing pathways is limited. Myocardial oxygen consumption is determined by regulation of energy metabolism, which shifts from glycolysis to lipid oxidation soon after birth, and is reversed in failing adult hea...
Systemic signals provided by nutrients and hormones are known to coordinate the growth and proliferation of different organs during development. However, within the brain, it is unclear how these signals influence neural progenitor divisions and neuronal diversity. Here, in the Drosophila visual system, we identify two developmental phases with dif...
Mass spectrometry with stable isotope labels has been seminal in discovering the dynamic state of living matter, but is limited to bulk tissues or cells. We developed multi-isotope imaging mass spectrometry (MIMS) that allowed us to view and measure stable isotope incorporation with submicrometre resolution. Here we apply MIMS to diverse organisms,...
Mass spectrometry with stable isotope labels has been seminal in discovering the dynamic state of living matter 1,2 , but is limited to bulk tissues or cells. We developed multi-isotope imaging mass spectrometry (MIMS) that allowed us to view and measure stable isotope incorporation with submicrometre resolution 3,4 . Here we apply MIMS to diverse...
Developing animals survive periods of starvation by protecting the growth of critical organs at the expense of other tissues. Here, we use Drosophila to explore the as yet unknown mechanisms regulating this privileged tissue growth. As in mammals, we observe in Drosophila that the CNS is more highly spared than other tissues during nutrient restric...
Many stem, progenitor and cancer cells undergo periods of mitotic quiescence from which they can be reactivated. The signals triggering entry into and exit from this reversible dormant state are not well understood. In the developing Drosophila central nervous system, multipotent self-renewing progenitors called neuroblasts undergo quiescence in a...
Coenzyme Q (CoQ) or ubiquinone is a lipid component of the electron transport chain required for ATP generation in mitochondria. Mutations in CoQ biosynthetic genes are associated with rare but severe infantile multisystemic diseases. CoQ itself is a popular over-the-counter dietary supplement that some clinical and rodent studies suggest might be...
Cell and particle quantification is one of the frequently used techniques in biology and clinical study. Variations of cell/particle population and/or protein expression level can provide information on many biological processes. In this chapter, we propose an image-based automatic quantification approach that can be applied to images from both flu...
Neural stem and progenitor cells generate the central nervous system (CNS) in organisms as diverse as insects and mammals. In Drosophila, multipotent asymmetrically dividing progenitors called neuroblasts produce neurons and glia throughout the developing CNS. Nevertheless, the time-windows of mitotic activity, the division modes, the termination m...
It is well established in species as diverse as insects and mammals that different neuronal and glial subtypes are born at distinct times during central nervous system development. In Drosophila, there is now compelling evidence that individual multipotent neuroblasts express a sequence of progenitor transcription factors which, in turn, regulates...
The timing mechanisms responsible for terminating cell proliferation toward the end of development remain unclear. In the Drosophila CNS, individual progenitors called neuroblasts are known to express a series of transcription factors endowing daughter neurons with different temporal identities. Here we show that Castor and Seven-Up, members of thi...
