Scholarly Works - Physiology, Development and Neuroscience


Recent Submissions

Now showing 1 - 20 of 441
  • ItemAccepted versionOpen Access
    A PAX5-OCT4-PRDM1 developmental switch specifies human primordial germ cells.
    (Springer Nature, 2018-06) Fang, Fang; Angulo, Benjamin; Xia, Ninuo; Sukhwani, Meena; Wang, Zhengyuan; Carey, Charles C; Mazurie, Aurélien; Cui, Jun; Wilkinson, Royce; Wiedenheft, Blake; Irie, Naoko; Surani, M Azim; Orwig, Kyle E; Reijo Pera, Renee A; Surani, Azim [0000-0002-8640-4318]
    Dysregulation of genetic pathways during human germ cell development leads to infertility. Here, we analysed bona fide human primordial germ cells (hPGCs) to probe the developmental genetics of human germ cell specification and differentiation. We examined the distribution of OCT4 occupancy in hPGCs relative to human embryonic stem cells (hESCs). We demonstrated that development, from pluripotent stem cells to germ cells, is driven by switching partners with OCT4 from SOX2 to PAX5 and PRDM1. Gain- and loss-of-function studies revealed that PAX5 encodes a critical regulator of hPGC development. Moreover, an epistasis analysis indicated that PAX5 acts upstream of OCT4 and PRDM1. The PAX5-OCT4-PRDM1 proteins form a core transcriptional network that activates germline and represses somatic programmes during human germ cell differentiation. These findings illustrate the power of combined genome editing, cell differentiation and engraftment for probing human developmental genetics that have historically been difficult to study.
  • ItemAccepted versionOpen Access
    In vitro generation of mouse polarized embryo-like structures from embryonic and trophoblast stem cells
    (Springer Nature, 2018-07) Harrison, sarah ellys; Sozen, berna; Zernicka-Goetz, magdalena; Sozen Kaya, Berna [0000-0001-5834-5819]; Zernicka-Goetz, Magdalena [0000-0002-7004-2471]
    Mammalian embryogenesis requires the coordination of embryonic and extra-embryonic tissues to enable implantation into the uterus and post-implantation development to establish the body plan. Mouse embryonic stem cells (ESCs) are a useful tool for studying pluripotent embryonic tissue in vitro. However, they cannot undertake correct embryogenesis alone. Many attempts to model the early embryo in vitro involve the aggregation of ESCs into spheroids of variable size and cell number that undertake germ-layer specification but fail to recapitulate the characteristic architecture and arrangement of tissues of the early embryo. Here, we describe a protocol to generate the first embryo-like structures by directing the assembly of mouse ESCs and extra-embryonic trophoblast stem cells (TSCs) in a 3D extracellular matrix (ECM) into structures we call ‘polarized embryo-like structures’. By establishing the medium and culture conditions needed to support the growth of both stem cell types simultaneously, embryonic architecture is generated within 4 d of co-culture. This protocol can be performed by those proficient in standard ESC culture techniques and can be used in developmental studies to investigate the interactions between embryonic and extra-embryonic tissues during mammalian development.
  • ItemAccepted versionOpen Access
    IFPA meeting 2017 workshop report: Clinical placentology, 3D structure-based modeling of placental function, placental bed, and treating placental dysfunction.
    (Elsevier, 2018-04) Acharya, Ganesh; Aplin, John; Brownbill, Paul; Bulmer, Judith; Burton, Graham; Chamley, Larry; Chernyavsky, Igor; Clark, Alys; Collins, Sally; Cottrell, Elizabeth; Dilworth, Mark; Elad, David; Filoche, Marcel; Hannan, Natalie; Heazell, Alexander EP; Jensen, Oliver; Johnstone, Edward D; Leach, Lopa; Lewis, Rohan; Morgan, Terry; Myers, Jenny; Nye, Gareth; Oyen, Michelle; Salafia, Carolyn; Schneider, Henning; O'Tierney-Ginn, Perrie; Burton, Graham [0000-0001-8677-4143]; Oyen, Michelle [0000-0002-3428-748X]
    Workshops are an important part of the IFPA annual meeting as they allow for discussion of specialized topics. At IFPA meeting 2017 there were four themed workshops, all of which are summarized in this report. These workshops discussed new knowledge and technological innovations in the following areas of research: 1) placental bed; 2) 3D structural modeling; 3) clinical placentology; 4) treatment of placental dysfunction.
  • ItemAccepted versionOpen Access
    Tracing cellular dynamics in tissue development, maintenance and disease.
    (Elsevier BV, 2016-12) Rulands, Steffen; Simons, Benjamin D; Rulands, Steffen [0000-0001-6398-1553]; Simons, Benjamin [0000-0002-3875-7071]
    The coordination of cell proliferation and differentiation is central to the development and maintenance of tissues, while its dysregulation underlies the transition to diseased states. By combining lineage tracing with transcriptional profiling and marker-based assays, statistical methods are delivering insights into the dynamics of stem cells and their developmental precursors. These studies have provided evidence for molecular heterogeneity and fate priming, and have revealed a role for stochasticity in stem cell fate, refocusing the search for regulatory mechanisms. At the same time, they present a quantitative platform to study the initiation and progression of disease. Here, we review how quantitative lineage tracing strategies are shaping our understanding of the cellular mechanisms of tissue development, maintenance and disease.
  • ItemPublished versionOpen Access
    Kuhnian revolutions in neuroscience: the role of tool development.
    (Springer Science and Business Media LLC, 2018) Parker, David; Parker, David [0000-0002-5345-348X]
    The terms "paradigm" and "paradigm shift" originated in "The Structure of Scientific Revolutions" by Thomas Kuhn. A paradigm can be defined as the generally accepted concepts and practices of a field, and a paradigm shift its replacement in a scientific revolution. A paradigm shift results from a crisis caused by anomalies in a paradigm that reduce its usefulness to a field. Claims of paradigm shifts and revolutions are made frequently in the neurosciences. In this article I will consider neuroscience paradigms, and the claim that new tools and techniques rather than crises have driven paradigm shifts. I will argue that tool development has played a minor role in neuroscience revolutions.
  • ItemPublished versionOpen Access
    Isolating the direct effects of adverse developmental conditions on in vivo cardiovascular function at adulthood: the avian model.
    (Cambridge University Press (CUP), 2018-08) Skeffington, KL; Beck, C; Itani, N; Giussani, DA; Giussani, Dino [0000-0002-1308-1204]
    It is now well accepted that exposure to adverse environmental conditions in utero can predispose a fetus to disease later in life. Using an avian model to study the programming of disease has a unique advantage as it allows isolation of the direct effects of adverse conditions on fetal physiology, without any confounding effects via the mother or placenta. However, experiments in avian models are limited by the lack of well-established surgical protocols for the adult bird, which we have established in this study. Surgery was performed on seven young adult Bovan Brown chickens (body weight 1617±214 g, mean±s.d.) in order to instrument them with femoral arterial and venous catheters and a femoral arterial flow probe. Isoflurane and lidocaine were both found to have depressive effects on chicken cardiovascular function. Optimised methods of anaesthesia, intraoperative monitoring, surgical approach, postoperative care, and experimentation are described. Chickens recovered rapidly from surgery without significant blood gas perturbation, and basal in vivo cardiovascular studies were performed following 5 days of recovery. These techniques allow detailed investigation of avian cardiometabolic function, permitting determination of the consequences in later life of direct environmental insults to fetal physiology, isolated from additional effects on maternal physiology and/or placental endocrinology.
  • ItemAccepted versionOpen Access
    Roger Yonchien Tsien (February 1, 1952 - August 24, 2016)
    (Royal Society Publishing, 2018-12-01) Huang, CL; Huang, Christopher [0000-0001-9553-6112]
    Roger Yonchien Tsien (1952-2016; Elected ForMemRS 2006) displayed precocious childhood talents in chemistry. After graduating from Harvard University in chemistry and physics in 1972, he pursued a PhD programme in the Physiological Laboratory, Cambridge, under Prof. Richard Adrian’s supervision with Marshal Scholarship support. His thesis “The design and use of organic chemical tools in cellular physiology” won the Gedge Prize, and a Comyns Berkeley Research Fellowship by Gonville and Caius College supporting his postdoctoral work developing Ca2+-sensitive electrodes and fluorescent probes measuring cellular [Ca2+]. His novel tetracarboxylate quin-2 readily accessed cells as its subsequently cleavable acetomethoxy-ester and signalled in the physiological [Ca2+] range. At Berkeley, further improved ratiometric and strongly fluorescent probes included the Ca2+-sensing indo-1, fura-2 and fluo-3, sensors for other strategic ions, and molecules that could photolytically uncage key intracellular regulators. At San Diego, design of fluorescent protein complexes build from the cAMP-binding phosphokinase A was followed by Nobel prizewinning work expressing green fluorescent protein (GFP) and developing spectral GFP variants forming fluorescent resonance energy transfer (FRET) pairs. Their conjugation with further proteins specifically binding particular ions or molecules under study permitted measurement of these by optical methods. Further detector protein complexes such as DsRED, fluorescent at longer wavelengths were to complement GFP. These interests culminated in the development of chemical tools with potential diagnostic and therapeutic clinical applications through their optical and magnetic resonance signals. His scientific work bequeathed a lasting wealth of chemical tools invaluable for physiological investigation with both current and future applicability.
  • ItemAccepted versionOpen Access
    Regulatory actions of 3',5'-cyclic adenosine monophosphate on osteoclast function: possible roles of Epac-mediated signaling.
    (Wiley, 2018-12) Jeevaratnam, Kamalan; Salvage, Samantha C; Li, Mengye; Huang, Christopher L-H; Salvage, Samantha [0000-0002-5793-2349]; Huang, Christopher [0000-0001-9553-6112]
    Alterations in cellular levels of the second messenger 3',5'-cyclic adenosine monophosphate ([cAMP]i ) regulate a wide range of physiologically important cellular signaling processes in numerous cell types. Osteoclasts are terminally differentiated, multinucleated cells specialized for bone resorption. Their systemic regulator, calcitonin, triggers morphometrically and pharmacologically distinct retraction (R) and quiescence (Q) effects on cell-spread area and protrusion-retraction motility, respectively, paralleling its inhibition of bone resorption. Q effects were reproduced by cholera toxin-mediated Gs -protein activation known to increase [cAMP]i , unaccompanied by the [Ca2+ ]i changes contrastingly associated with R effects. We explore a hypothesis implicating cAMP signaling involving guanine nucleotide-exchange activation of the small GTPase Ras-proximate-1 (Rap1) by exchange proteins directly activated by cAMP (Epac). Rap1 activates integrin clustering, cell adhesion to bone matrix, associated cytoskeletal modifications and signaling processes, and transmembrane transduction functions. Epac activation enhanced, whereas Epac inhibition or shRNA-mediated knockdown compromised, the appearance of markers for osteoclast differentiation and motility following stimulation by receptor activator of nuclear factor kappa-Β ligand (RANKL). Deficiencies in talin and Rap1 compromised in vivo bone resorption, producing osteopetrotic phenotypes in genetically modified murine models. Translational implications of an Epac-Rap1 signaling hypothesis in relationship to N-bisphosphonate actions on prenylation and membrane localization of small GTPases are discussed.
  • ItemPublished versionOpen Access
    Suppression of epithelial folding at actomyosin-enriched compartment boundaries downstream of Wingless signalling
    (The Company of Biologists, 2018-04-24) Sanson, B; Urbano; Naylor; Scarpa, E; Muresan; Sanson, Benedicte [0000-0002-2782-4195]; Muresan, Leila [0000-0002-7602-0249]
    Epithelial folding shapes embryos and tissues during development. Here, we investigate the coupling between epithelial folding and actomyosin-enriched compartmental boundaries. The mechanistic relationship between the two is unclear, because actomyosin-enriched boundaries are not necessarily associated with folds. Also, some cases of epithelial folding occur independently of actomyosin contractility. We investigated the shallow folds called parasegment grooves that form at boundaries between anterior and posterior compartments in the early Drosophila embryo. We demonstrate that formation of these folds requires the presence of an actomyosin enrichment along the boundary cell-cell contacts. These enrichments, which require Wingless signalling, increase interfacial tension not only at the level of the adherens junctions but also along the lateral surfaces. We find that epithelial folding is normally under inhibitory control because different genetic manipulations, including depletion of the Myosin II phosphatase Flapwing, increase the depth of folds at boundaries. Fold depth correlates with the levels of Bazooka (Baz), the Par-3 homologue, along the boundary cell-cell contacts. Moreover, Wingless and Hedgehog signalling have opposite effects on fold depth at the boundary that correlate with changes in Baz planar polarity.
  • ItemPublished versionOpen Access
    Rhythmic actomyosin-driven contractions induced by sperm entry predict mammalian embryo viability.
    (Springer Science and Business Media LLC, 2011-08-09) Ajduk, Anna; Ilozue, Tagbo; Windsor, Shane; Yu, Yuansong; Seres, K Bianka; Bomphrey, Richard J; Tom, Brian D; Swann, Karl; Thomas, Adrian; Graham, Chris; Zernicka-Goetz, Magdalena; Tom, Brian [0000-0002-3335-9322]; Zernicka-Goetz, Magdalena [0000-0002-7004-2471]
    Fertilization-induced cytoplasmic flows are a conserved feature of eggs in many species. However, until now the importance of cytoplasmic flows for the development of mammalian embryos has been unknown. Here, by combining a rapid imaging of the freshly fertilized mouse egg with advanced image analysis based on particle image velocimetry, we show that fertilization induces rhythmical cytoplasmic movements that coincide with pulsations of the protrusion forming above the sperm head. We find that these movements are caused by contractions of the actomyosin cytoskeleton triggered by Ca(2+) oscillations induced by fertilization. Most importantly, the relationship between the movements and the events of egg activation makes it possible to use the movements alone to predict developmental potential of the zygote. In conclusion, this method offers, thus far, the earliest and fastest, non-invasive way to predict the viability of eggs fertilized in vitro and therefore can potentially improve greatly the prospects for IVF treatment.
  • ItemPublished versionOpen Access
    HLA class II regulation and structure. Analysis with HLA-DR3 and HLA-DP point mutants.
    (Rockefeller University Press, 1985-10-01) Pious, D; Dixon, L; Levine, F; Cotner, T; Johnson, R; Johnson, Randall [0000-0002-4084-6639]
    Point mutations that affect HLA-DR structure or expression have not previously been described. In the present study, we isolated such mutants by immunoselection of an ethyl methanesulfonate-mutagenized HLA-DR3 cell line with an anti-HLA-DR3 monoclonal antibody, 16.23. To facilitate analysis, we used a parent cell line with a preexisting deletion of one haplotype encompassing DR and DQ alpha and beta. The selection yielded two sets of mutants, one with defects in DR3 structure, the other with defects in different steps leading to DR expression. Of the expression-defective mutants, one had undergone a second deletion removing the remaining DR alpha gene but no other class II genes. It had a normal abundance of DR beta mRNA but had lost binding of DR monomorphic antibodies, indicating that DR beta chains do not form noncognate dimers. A second mutant had an abnormally large DR alpha mRNA, probably resulting from a splice site mutation. Several mutants had marked reductions in DR beta mRNA levels; in two of these, the lesion appeared to be transcriptional because the reduction in DR beta mRNA was paralleled by an altered methylation pattern of one of the DR beta genes. Other expression-defective mutants had different posttranscriptional defects. Some of the mutations were similar to those that have been found in mouse strains defective in I-E expression, whereas others have no known natural counterpart. The matrix of reactivities of anti-HLA class II monomorphic antibodies with these and similar mutants allowed us to define the gene products recognized by these antibodies. A set of seven mutants were "epitope defective," that is, they expressed normal or near normal levels of HLA-DR3 but no longer bound 16.23. Unexpectedly, each of the epitope mutants had decreased DR dimer stability. These mutants should be useful in localizing the DR3 alloepitope and in elucidating its contribution as a restriction element in the presentation of soluble antigen to immune T cells.
  • ItemPublished versionOpen Access
    Microsaccadic sampling of moving image information provides Drosophila hyperacute vision.
    (eLife Sciences Publications, Ltd, 2017-09-05) Juusola, Mikko; Dau, An; Song, Zhuoyi; Solanki, Narendra; Rien, Diana; Jaciuch, David; Dongre, Sidhartha Anil; Blanchard, Florence; de Polavieja, Gonzalo G; Hardie, Roger C; Takalo, Jouni; Juusola, Mikko [0000-0002-4428-5330]; Dau, An [0000-0002-7802-565X]; Song, Zhuoyi [0000-0001-9991-4053]; Dongre, Sidhartha Anil [0000-0003-2575-4362]; de Polavieja, Gonzalo G [0000-0001-5359-3426]; Hardie, Roger C [0000-0001-5531-3264]
    Small fly eyes should not see fine image details. Because flies exhibit saccadic visual behaviors and their compound eyes have relatively few ommatidia (sampling points), their photoreceptors would be expected to generate blurry and coarse retinal images of the world. Here we demonstrate that Drosophila see the world far better than predicted from the classic theories. By using electrophysiological, optical and behavioral assays, we found that R1-R6 photoreceptors' encoding capacity in time is maximized to fast high-contrast bursts, which resemble their light input during saccadic behaviors. Whilst over space, R1-R6s resolve moving objects at saccadic speeds beyond the predicted motion-blur-limit. Our results show how refractory phototransduction and rapid photomechanical photoreceptor contractions jointly sharpen retinal images of moving objects in space-time, enabling hyperacute vision, and explain how such microsaccadic information sampling exceeds the compound eyes' optical limits. These discoveries elucidate how acuity depends upon photoreceptor function and eye movements.
  • ItemOpen Access
    Neural control of dynamic 3-dimensional skin papillae for cuttlefish camouflage.
    (iScience, 2018-02-15) Gonzalez Bellido, Paloma; Scaros, Alexia; Hanlon, Roger; Wardill, Trevor; Wardill, Trevor [0000-0002-2049-113X]
    The colour and pattern changing abilities of octopus, squid and cuttlefish via chromatophore neuro-muscular organs are unparalleled. Cuttlefish and octopuses also have a unique muscular hydrostat system in their skin. When expressed, dermal bumps called papillae disrupt body shape and imitate the fine texture of surrounding objects, yet the control system is unknown. Here we report for papillae: (i) the motoneurons and the neurotransmitters that control activation and relaxation, (ii) a physiologically fast expression and retraction system, and (iii) a complex of smooth and striated muscles that enables long-term expression of papillae through sustained tension in the absence of neural input. The neural circuits controlling acute shape-shifting skin papillae in cuttlefish show homology to the iridescence circuits in squids. The sustained-tension in papillary muscles for long-term camouflage utilizes muscle heterogeneity, and points toward the existence of a "catch-like" mechanism that would reduce the necessary energy expenditure.
  • ItemOpen Access
    Non-canonical Phototransduction Mediates Synchronization of the Drosophila melanogaster Circadian Clock and Retinal Light Responses.
    (Elsevier BV, 2018-06-04) Ogueta, Maite; Hardie, Roger C; Stanewsky, Ralf; Hardie, Roger [0000-0001-5531-3264]
    The daily light-dark cycles represent a key signal for synchronizing circadian clocks. Both insects and mammals possess dedicated "circadian" photoreceptors but also utilize the visual system for clock resetting. In Drosophila, circadian clock resetting is achieved by the blue-light photoreceptor cryptochrome (CRY), which is expressed within subsets of the brain clock neurons. In addition, rhodopsin-expressing photoreceptor cells contribute to light synchronization. Light resets the molecular clock by CRY-dependent degradation of the clock protein Timeless (TIM), although in specific subsets of key circadian pacemaker neurons, including the small ventral lateral neurons (s-LNvs), TIM and Period (PER) oscillations can be synchronized by light independent of CRY and canonical visual Rhodopsin phototransduction. Here, we show that at least three of the seven Drosophila rhodopsins can utilize an alternative transduction mechanism involving the same α-subunit of the heterotrimeric G protein operating in canonical visual phototransduction (Gq). Surprisingly, in mutants lacking the canonical phospholipase C-β (PLC-β) encoded by the no receptor potential A (norpA) gene, we uncovered a novel transduction pathway using a different PLC-β encoded by the Plc21C gene. This novel pathway is important for behavioral clock resetting to semi-natural light-dark cycles and mediates light-dependent molecular synchronization within the s-LNv clock neurons. The same pathway appears to be responsible for norpA-independent light responses in the compound eye. We show that Rhodopsin 5 (Rh5) and Rh6, present in the R8 subset of retinal photoreceptor cells, drive both the long-term circadian and rapid light responses in the eye.
  • ItemOpen Access
    The Role of Kiss1 Neurons As Integrators of Endocrine, Metabolic, and Environmental Factors in the Hypothalamic-Pituitary-Gonadal Axis.
    (Frontiers Media SA, 2018) Yeo, Shel-Hwa; Colledge, William H; Colledge, Bill [0000-0002-9603-4429]
    Kisspeptin-GPR54 signaling in the hypothalamus is required for reproduction and fertility in mammals. Kiss1 neurons are key regulators of gonadotropin-releasing hormone (GnRH) release and modulation of the hypothalamic-pituitary-gonadal (HPG) axis. Arcuate Kiss1 neurons project to GnRH nerve terminals in the median eminence, orchestrating the pulsatile secretion of luteinizing hormone (LH) through the intricate interaction between GnRH pulse frequency and the pituitary gonadotrophs. Arcuate Kiss1 neurons, also known as KNDy neurons in rodents and ruminants because of their co-expression of neurokinin B and dynorphin represent an ideal hub to receive afferent inputs from other brain regions in response to physiological and environmental changes, which can regulate the HPG axis. This review will focus on studies performed primarily in rodent and ruminant species to explore potential afferent inputs to Kiss1 neurons with emphasis on the arcuate region but also considering the rostral periventricular region of the third ventricle (RP3V). Specifically, we will discuss how these inputs can be modulated by hormonal, metabolic, and environmental factors to control gonadotropin secretion and fertility. We also summarize the methods and techniques that can be used to study functional inputs into Kiss1 neurons.
  • ItemPublished versionOpen Access
    Visual approach computation in feeding hoverflies.
    (The Company of Biologists, 2018-05-22) Thyselius, Malin; Gonzalez-Bellido, Paloma T; Wardill, Trevor J; Nordström, Karin; Gonzalez-Bellido, Paloma T [0000-0003-2201-991X]; Wardill, Trevor J [0000-0002-2049-113X]; Nordström, Karin [0000-0002-6020-6348]
    On warm sunny days, female hoverflies are often observed feeding from a wide range of wild and cultivated flowers. In doing so, hoverflies serve a vital role as alternative pollinators, and are suggested to be the most important pollinators after bees and bumblebees. Unless the flower hoverflies are feeding from is large, they do not readily share the space with other insects, but instead opt to leave if another insect approaches. We used high-speed videography followed by 3D reconstruction of flight trajectories to quantify how female Eristalis hoverflies respond to approaching bees, wasps and two different hoverfly species. We found that, in 94% of the interactions, the occupant female left the flower when approached by another insect. We found that compared with spontaneous take-offs, the occupant hoverfly's escape response was performed at ∼3 times higher speed (spontaneous take-off at 0.2±0.05 m s-1 compared with 0.55±0.08 m s-1 when approached by another Eristalis). The hoverflies tended to take off upward and forward, while taking the incomer's approach angle into account. Intriguingly, we found that, when approached by wasps, the occupant Eristalis took off at a higher speed and when the wasp was further away. This suggests that feeding hoverflies may be able to distinguish these predators, demanding impressive visual capabilities. Our results, including quantification of the visual information available before occupant take-off, provide important insight into how freely behaving hoverflies perform escape responses from competitors and predators (e.g. wasps) in the wild.
  • ItemAccepted versionOpen Access
    Metabolic adjustment to high-altitude hypoxia: from genetic signals to physiological implications.
    (Portland Press Ltd., 2018-06-19) Murray, Andrew J; Montgomery, Hugh E; Feelisch, Martin; Grocott, Michael PW; Martin, Daniel S; Murray, Andrew [0000-0002-0929-9315]
    Ascent to high altitude is associated with physiological responses that counter the stress of hypobaric hypoxia by increasing oxygen delivery and by altering tissue oxygen utilisation via metabolic modulation. At the cellular level, the transcriptional response to hypoxia is mediated by the hypoxia-inducible factor (HIF) pathway and results in promotion of glycolytic capacity and suppression of oxidative metabolism. In Tibetan highlanders, gene variants encoding components of the HIF pathway have undergone selection and are associated with adaptive phenotypic changes, including suppression of erythropoiesis and increased blood lactate levels. In some highland populations, there has also been a selection of variants in PPARA, encoding peroxisome proliferator-activated receptor alpha (PPARα), a transcriptional regulator of fatty acid metabolism. In one such population, the Sherpas, lower muscle PPARA expression is associated with a decreased capacity for fatty acid oxidation, potentially improving the efficiency of oxygen utilisation. In lowlanders ascending to altitude, a similar suppression of fatty acid oxidation occurs, although the underlying molecular mechanism appears to differ along with the consequences. Unlike lowlanders, Sherpas appear to be protected against oxidative stress and the accumulation of intramuscular lipid intermediates at altitude. Moreover, Sherpas are able to defend muscle ATP and phosphocreatine levels in the face of decreased oxygen delivery, possibly due to suppression of ATP demand pathways. The molecular mechanisms allowing Sherpas to successfully live, work and reproduce at altitude may hold the key to novel therapeutic strategies for the treatment of diseases to which hypoxia is a fundamental contributor.
  • ItemPublished versionOpen Access
    GKAP Acts as a Genetic Modulator of NMDAR Signaling to Govern Invasive Tumor Growth.
    (Elsevier BV, 2018-04-09) Li, Leanne; Zeng, Qiqun; Bhutkar, Arjun; Galván, José A; Karamitopoulou, Eva; Noordermeer, Daan; Peng, Mei-Wen; Piersigilli, Alessandra; Perren, Aurel; Zlobec, Inti; Robinson, Hugh; Iruela-Arispe, M Luisa; Hanahan, Douglas; Robinson, Hugh [0000-0002-5048-9954]
    Genetic linkage analysis previously suggested that GKAP, a scaffold protein of the N-methyl-D-aspartate receptor (NMDAR), was a potential modifier of invasion in a mouse model of pancreatic neuroendocrine tumor (PanNET). Here, we establish that GKAP governs invasive growth and treatment response to NMDAR inhibitors of PanNET via its pivotal role in regulating NMDAR pathway activity. Combining genetic knockdown of GKAP and pharmacological inhibition of NMDAR, we implicate as downstream effectors FMRP and HSF1, which along with GKAP demonstrably support invasiveness of PanNET and pancreatic ductal adenocarcinoma cancer cells. Furthermore, we distilled genome-wide expression profiles orchestrated by the NMDAR-GKAP signaling axis, identifying transcriptome signatures in tumors with low/inhibited NMDAR activity that significantly associate with favorable patient prognosis in several cancer types.
  • ItemPublished versionOpen Access
    Altered autonomic control of heart rate variability in the chronically hypoxic fetus.
    (Wiley, 2018-12) Shaw, CJ; Allison, BJ; Itani, N; Botting, KJ; Niu, Y; Lees, CC; Giussani, DA; Shaw, CJ [0000-0002-8002-2976]; Allison, BJ [0000-0002-1060-513X]; Itani, N [0000-0001-6171-1349]; Botting, KJ [0000-0003-4290-9821]; Niu, Y [0000-0002-8843-9952]; Lees, CC [0000-0002-2104-5561]; Giussani, DA [0000-0002-1308-1204]
    KEY POINTS: Fetal heart rate variability (FHRV) has long been recognised as a powerful predictor of fetal wellbeing, and a decrease in FHRV is associated with fetal compromise. However, the mechanisms by which FHRV is reduced in the chronically hypoxic fetus have yet to be established. The sympathetic and parasympathetic influences on heart rate mature at different rates throughout fetal life, and can be assessed by time domain and power spectral analysis of FHRV. In this study of chronically instrumented fetal sheep in late gestation, we analysed FHRV daily over a 16 day period towards term, and compared changes between fetuses of control and chronically hypoxic pregnancy. We show that FHRV in sheep is reduced by chronic hypoxia, predominantly due to dysregulation of the sympathetic control of the fetal heart rate. This presents a potential mechanism by which a reduction in indices of FHRV predicts fetuses at increased risk of neonatal morbidity and mortality in humans. Reduction in overall FHRV may therefore provide a biomarker that autonomic dysregulation of fetal heart rate control has taken place in a fetus where uteroplacental dysfunction is suspected. ABSTRACT: Although fetal heart rate variability (FHRV) has long been recognised as a powerful predictor of fetal wellbeing, the mechanisms by which it is reduced in the chronically hypoxic fetus have yet to be established. In particular, the physiological mechanism underlying the reduction of short term variation (STV) in fetal compromise remains unclear. In this study, we present a longitudinal study of the development of autonomic control of FHRV, assessed by indirect indices, time domain and power spectral analysis, in normoxic and chronically hypoxic, chronically catheterised, singleton fetal sheep over the last third of gestation. We used isobaric chambers able to maintain pregnant sheep for prolonged periods in hypoxic conditions (stable fetal femoral arterial PO2 10-12 mmHg), and a customised wireless data acquisition system to record beat-to-beat variation in the fetal heart rate. We determined in vivo longitudinal changes in overall FHRV and the sympathetic and parasympathetic contribution to FHRV in hypoxic (n = 6) and normoxic (n = 6) ovine fetuses with advancing gestational age. Normoxic fetuses show gestational age-related increases in overall indices of FHRV, and in the sympathetic nervous system contribution to FHRV (P < 0.001). Conversely, gestational age-related increases in overall FHRV were impaired by exposure to chronic hypoxia, and there was evidence of suppression of the sympathetic nervous system control of FHRV after 72 h of exposure to hypoxia (P < 0.001). This demonstrates that exposure to late gestation isolated chronic fetal hypoxia has the potential to alter the development of the autonomic nervous system control of FHRV in sheep. This presents a potential mechanism by which a reduction in indices of FHRV in human fetuses affected by uteroplacental dysfunction can predict fetuses at increased risk.
  • ItemAccepted versionOpen Access
    HIF isoforms in the skin differentially regulate systemic arterial pressure.
    (Proceedings of the National Academy of Sciences, 2013-10-22) Cowburn, Andrew S; Takeda, Norihiko; Boutin, Adam T; Kim, Jung-Whan; Sterling, Jane C; Nakasaki, Manando; Southwood, Mark; Goldrath, Ananda W; Jamora, Colin; Nizet, Victor; Chilvers, Edwin R; Johnson, Randall S; Cowburn, Andrew [0000-0001-9145-4275]; Chilvers, Edwin [0000-0002-4230-9677]; Johnson, Randall [0000-0002-4084-6639]
    Vascular flow through tissues is regulated via a number of homeostatic mechanisms. Localized control of tissue blood flow, or autoregulation, is a key factor in regulating tissue perfusion and oxygenation. We show here that the net balance between two hypoxia-inducible factor (HIF) transcription factor isoforms, HIF-1α and HIF-2α, is an essential mechanism regulating both local and systemic blood flow in the skin of mice. We also show that balance of HIF isoforms in keratinocyte-specific mutant mice affects thermal adaptation, exercise capacity, and systemic arterial pressure. The two primary HIF isoforms achieve these effects in opposing ways that are associated with HIF isoform regulation of nitric oxide production. We also show that a correlation exists between altered levels of HIF isoforms in the skin and the degree of idiopathic hypertension in human subjects. Thus, the balance between HIF-1α and HIF-2α expression in keratinocytes is a control element of both tissue perfusion and systemic arterial pressure, with potential implications in human hypertension.