1
|
Specterman MJ, Aziz Q, Li Y, Anderson NA, Ojake L, Ng KE, Thomas AM, Finlay MC, Schilling RJ, Lambiase PD, Tinker A. Hypoxia Promotes Atrial Tachyarrhythmias via Opening of ATP-Sensitive Potassium Channels. Circ Arrhythm Electrophysiol 2023; 16:e011870. [PMID: 37646176 PMCID: PMC10510820 DOI: 10.1161/circep.123.011870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Accepted: 08/15/2023] [Indexed: 09/01/2023]
Abstract
BACKGROUND Hypoxia-ischemia predisposes to atrial arrhythmia. Atrial ATP-sensitive potassium channel (KATP) modulation during hypoxia has not been explored. We investigated the effects of hypoxia on atrial electrophysiology in mice with global deletion of KATP pore-forming subunits. METHODS Whole heart KATP RNA expression was probed. Whole-cell KATP current and action potentials were recorded in isolated wild-type (WT), Kir6.1 global knockout (6.1-gKO), and Kir6.2 global knockout (6.2-gKO) murine atrial myocytes. Langendorff-perfused hearts were assessed for atrial effective refractory period (ERP), conduction velocity, wavefront path length (WFPL), and arrhymogenicity under normoxia/hypoxia using a microelectrode array and programmed electrical stimulation. Heart histology was assessed. RESULTS Expression patterns were essentially identical for all KATP subunit RNA across human heart, whereas in mouse, Kir6.1 and SUR2 (sulphonylurea receptor subunit) were higher in ventricle than atrium, and Kir6.2 and SUR1 were higher in atrium. Compared with WT, 6.2-gKO atrial myocytes had reduced tolbutamide-sensitive current and action potentials were more depolarized with slower upstroke and reduced peak amplitude. Action potential duration was prolonged in 6.1-gKO atrial myocytes, absent of changes in other ion channel gene expression or atrial myocyte hypertrophy. In Langendorff-perfused hearts, baseline atrial ERP was prolonged and conduction velocity reduced in both KATP knockout mice compared with WT, without histological fibrosis. Compared with baseline, hypoxia led to conduction velocity slowing, stable ERP, and WFPL shortening in WT and 6.1-gKO hearts, whereas WFPL was stable in 6.2-gKO hearts due to ERP prolongation with conduction velocity slowing. Tolbutamide reversed hypoxia-induced WFPL shortening in WT and 6.1-gKO hearts through ERP prolongation. Atrial tachyarrhythmias inducible with programmed electrical stimulation during hypoxia in WT and 6.1-gKO mice correlated with WFPL shortening. Spontaneous arrhythmia was not seen. CONCLUSIONS KATP block/absence leads to cellular and tissue level atrial electrophysiological modification. Kir6.2 global knockout prevents hypoxia-induced atrial WFPL shortening and atrial arrhythmogenicity to programmed electrical stimulation. This mechanism could be explored translationally to treat ischemically driven atrial arrhythmia.
Collapse
Affiliation(s)
- Mark J. Specterman
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| | - Qadeer Aziz
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| | - Yiwen Li
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| | - Naomi A. Anderson
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| | - Leona Ojake
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| | - Keat-Eng Ng
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| | - Alison M. Thomas
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| | - Malcolm C. Finlay
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| | - Richard J. Schilling
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| | - Pier D. Lambiase
- Institute of Cardiovascular Science, University College London, United Kingdom (P.D.L.)
| | - Andrew Tinker
- William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom (M.J.S., Q.A., Y.L., N.A.A., L.O., K.-E.N., A.M.T., M.C.F., R.J.S., A.T.)
| |
Collapse
|
2
|
Bercea C, Limbu R, Behnam K, Ng KE, Aziz Q, Tinker A, Tamagnini F, Cottrell GS, McNeish AJ. Omega-3 polyunsaturated fatty acid-induced vasodilation in mouse aorta and mesenteric arteries is not mediated by ATP-sensitive potassium channels. Front Physiol 2022; 13:1033216. [PMID: 36589427 PMCID: PMC9797959 DOI: 10.3389/fphys.2022.1033216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 11/30/2022] [Indexed: 12/23/2022] Open
Abstract
There is strong evidence that the omega-3 polyunsaturated fatty acids (n-3 PUFAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) have cardioprotective effects. n-3 PUFAs cause vasodilation in hypertensive patients, in part controlled by increased membrane conductance to potassium. As KATP channels play a major role in vascular tone regulation and are involved in hypertension, we aimed to verify whether n-3 PUFA-mediated vasodilation involved the opening of KATP channels. We used a murine model in which the KATP channel pore subunit, Kir6.1, is deleted in vascular smooth muscle. The vasomotor response of preconstricted arteries to physiologically relevant concentrations of DHA and EPA was measured using wire myography, using the channel blocker PNU-37883A. The effect of n-3 PUFAs on potassium currents in wild-type native smooth muscle cells was investigated using whole-cell patch clamping. DHA and EPA induced vasodilation in mouse aorta and mesenteric arteries; relaxations in the aorta were sensitive to KATP blockade with PNU-37883A. Endothelium removal didn't affect relaxation to EPA and caused a small but significant inhibition of relaxation to DHA. In the knock-out model, relaxations to DHA and EPA were unaffected by channel knockdown but were still inhibited by PNU-37883A, indicating that the action of PNU-37883A on relaxation may not reflect inhibition of KATP. In native aortic smooth muscle cells DHA failed to activate KATP currents. We conclude that DHA and EPA cause vasodilation in mouse aorta and mesenteric arteries. Relaxations in blocker-treated arteries from knock-out mice demonstrate that KATP channels are not involved in the n-3 PUFA-induced relaxation.
Collapse
Affiliation(s)
- Cristiana Bercea
- McNeish Laboratory, School of Chemistry, Food and Pharmacy, Department of Pharmacology, University of Reading, London, United Kingdom
- Tinker Laboratory, William Harvey Research Institute, Clinical Pharmacology and Precision Medicine, Queen Mary University, London, United Kingdom
| | - Roshan Limbu
- McNeish Laboratory, School of Chemistry, Food and Pharmacy, Department of Pharmacology, University of Reading, London, United Kingdom
| | - Kamila Behnam
- McNeish Laboratory, School of Chemistry, Food and Pharmacy, Department of Pharmacology, University of Reading, London, United Kingdom
| | - Keat-Eng Ng
- Tinker Laboratory, William Harvey Research Institute, Clinical Pharmacology and Precision Medicine, Queen Mary University, London, United Kingdom
| | - Qadeer Aziz
- Tinker Laboratory, William Harvey Research Institute, Clinical Pharmacology and Precision Medicine, Queen Mary University, London, United Kingdom
| | - Andrew Tinker
- Tinker Laboratory, William Harvey Research Institute, Clinical Pharmacology and Precision Medicine, Queen Mary University, London, United Kingdom
| | - Francesco Tamagnini
- McNeish Laboratory, School of Chemistry, Food and Pharmacy, Department of Pharmacology, University of Reading, London, United Kingdom
| | - Graeme S Cottrell
- McNeish Laboratory, School of Chemistry, Food and Pharmacy, Department of Pharmacology, University of Reading, London, United Kingdom
| | - Alister J McNeish
- McNeish Laboratory, School of Chemistry, Food and Pharmacy, Department of Pharmacology, University of Reading, London, United Kingdom
| |
Collapse
|
3
|
Ng KE, Delaney PJ, Thenet D, Murtough S, Webb CM, Zaman N, Tsisanova E, Mastroianni G, Walker SLM, Westaby JD, Pennington DJ, Pink R, Kelsell DP, Tinker A. Early inflammation precedes cardiac fibrosis and heart failure in desmoglein 2 murine model of arrhythmogenic cardiomyopathy. Cell Tissue Res 2021; 386:79-98. [PMID: 34236518 PMCID: PMC8526453 DOI: 10.1007/s00441-021-03488-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 06/18/2021] [Indexed: 12/19/2022]
Abstract
The study of a desmoglein 2 murine model of arrhythmogenic cardiomyopathy revealed cardiac inflammation as a key early event leading to fibrosis. Arrhythmogenic cardiomyopathy (AC) is an inherited heart muscle disorder leading to ventricular arrhythmias and heart failure due to abnormalities in the cardiac desmosome. We examined how loss of desmoglein 2 (Dsg2) in the young murine heart leads to development of AC. Apoptosis was an early cellular phenotype, and RNA sequencing analysis revealed early activation of inflammatory-associated pathways in Dsg2-null (Dsg2-/-) hearts at postnatal day 14 (2 weeks) that were absent in the fibrotic heart of adult mice (10 weeks). This included upregulation of iRhom2/ADAM17 and its associated pro-inflammatory cytokines and receptors such as TNFα, IL6R and IL-6. Furthermore, genes linked to specific macrophage populations were also upregulated. This suggests cardiomyocyte stress triggers an early immune response to clear apoptotic cells allowing tissue remodelling later on in the fibrotic heart. Our analysis at the early disease stage suggests cardiac inflammation is an important response and may be one of the mechanisms responsible for AC disease progression.
Collapse
Affiliation(s)
- K E Ng
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, EC1M 6BQ, UK.,Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - P J Delaney
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - D Thenet
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - S Murtough
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - C M Webb
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - N Zaman
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - E Tsisanova
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, EC1M 6BQ, UK
| | - G Mastroianni
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - S L M Walker
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, EC1M 6BQ, UK
| | - J D Westaby
- CRY Dept. of Cardiovascular Pathology, Cardiology Clinical Academic Group, Molecular and Clinical Sciences Research Institute, St. George's University of London, Jenner WingCranmer Terrace, London, SW17 0RE, UK
| | - D J Pennington
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - R Pink
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Headington Campus, Oxford, OX3 0BP, UK
| | - D P Kelsell
- Blizard Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK.
| | - A Tinker
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, EC1M 6BQ, UK.
| |
Collapse
|
4
|
Hall CL, Gurha P, Sabater-Molina M, Asimaki A, Futema M, Lovering RC, Suárez MP, Aguilera B, Molina P, Zorio E, Coarfa C, Robertson MJ, Cheedipudi SM, Ng KE, Delaney P, Hernández JP, Pastor F, Gimeno JR, McKenna WJ, Marian AJ, Syrris P. RNA sequencing-based transcriptome profiling of cardiac tissue implicates novel putative disease mechanisms in FLNC-associated arrhythmogenic cardiomyopathy. Int J Cardiol 2019; 302:124-130. [PMID: 31843279 DOI: 10.1016/j.ijcard.2019.12.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 11/26/2019] [Accepted: 12/02/2019] [Indexed: 11/25/2022]
Abstract
Arrhythmogenic cardiomyopathy (ACM) encompasses a group of inherited cardiomyopathies including arrhythmogenic right ventricular cardiomyopathy (ARVC) whose molecular disease mechanism is associated with dysregulation of the canonical WNT signalling pathway. Recent evidence indicates that ARVC and ACM caused by pathogenic variants in the FLNC gene encoding filamin C, a major cardiac structural protein, may have different molecular mechanisms of pathogenesis. We sought to identify dysregulated biological pathways in FLNC-associated ACM. RNA was extracted from seven paraffin-embedded left ventricular tissue samples from deceased ACM patients carrying FLNC variants and sequenced. Transcript levels of 623 genes were upregulated and 486 genes were reduced in ACM in comparison to control samples. The cell adhesion pathway and ILK signalling were among the prominent dysregulated pathways in ACM. Consistent with these findings, transcript levels of cell adhesion genes JAM2, NEO1, VCAM1 and PTPRC were upregulated in ACM samples. Moreover, several actin-associated genes, including FLNC, VCL, PARVB and MYL7, were suppressed, suggesting dysregulation of the actin cytoskeleton. Analysis of the transcriptome for dysregulated biological pathways predicted activation of inflammation and apoptosis and suppression of oxidative phosphorylation and MTORC1 signalling in ACM. Our data suggests dysregulated cell adhesion and ILK signalling as novel putative pathogenic mechanisms of ACM caused by FLNC variants which are distinct from the postulated disease mechanism of classic ARVC caused by desmosomal gene mutations. This knowledge could help in the design of future gene therapy strategies which would target specific components of these pathways and potentially lead to novel treatments for ACM.
Collapse
Affiliation(s)
- Charlotte L Hall
- Centre for Heart Muscle Disease, Institute of Cardiovascular Science, University College London, London, UK
| | - Priyatansh Gurha
- Center for Cardiovascular Genetics, Institute of Molecular Medicine, University of Texas Health Sciences Center at Houston, USA
| | - Maria Sabater-Molina
- Laboratorio de Cardiogenética, Instituto Murciano de Investigación Biosanitaria and Universidad de Murcia, Murcia, Spain
| | - Angeliki Asimaki
- Cardiology Clinical Academic Group, Molecular and Clinical Sciences Research Institute, St Georges University of London, London, UK
| | - Marta Futema
- Centre for Heart Muscle Disease, Institute of Cardiovascular Science, University College London, London, UK
| | - Ruth C Lovering
- Functional Gene Annotation Group, Pre-clinical and Fundamental Science, Institute of Cardiovascular Science, University College London, London, UK
| | - Mari Paz Suárez
- Instituto Nacional de Toxicologia y Ciencias Forenses de Madrid (INTCF), Madrid, Spain
| | - Beatriz Aguilera
- Instituto Nacional de Toxicologia y Ciencias Forenses de Madrid (INTCF), Madrid, Spain
| | - Pilar Molina
- Department of Pathology at the Instituto de Medicina Legal y Ciencias Forenses de Valencia (IMLCF-Valencia), Histology Unit at the Universitat de València, and Research Group on Inherited Heart Diseases, Sudden Death and Mechanisms of Disease (CaFaMuSMe) from the Instituto de Investigación Sanitaria (IIS) La Fe, Valencia, Spain
| | - Esther Zorio
- Cardiology Department at Hospital Universitario y Politécnico La Fe and Research Group on Inherited Heart Diseases, Sudden Death and Mechanisms of Disease (CaFaMuSMe) from the Instituto de Investigación Sanitaria (IIS) La Fe, Valencia, Spain; Center for Biomedical Network Research on Cardiovascular Diseases (CIBERCV), Madrid, Spain
| | | | | | - Sirisha M Cheedipudi
- Center for Cardiovascular Genetics, Institute of Molecular Medicine, University of Texas Health Sciences Center at Houston, USA
| | - Keat-Eng Ng
- William Harvey Heart Centre, Queen Mary University of London, London, UK
| | - Paul Delaney
- William Harvey Heart Centre, Queen Mary University of London, London, UK
| | | | - Francisco Pastor
- Servicio de Anatomía Patológica del Hospital Reina Sofía, Murcia, Spain
| | - Juan R Gimeno
- Servicio de Cardiologia del Hospital Universitario Virgen de la Arrixaca and Departamento de Medicina Interna de la Universidad de Murcia, Murcia, Spain; Center for Biomedical Network Research on Cardiovascular Diseases (CIBERCV), Madrid, Spain
| | - William J McKenna
- Centre for Heart Muscle Disease, Institute of Cardiovascular Science, University College London, London, UK
| | - Ali J Marian
- Center for Cardiovascular Genetics, Institute of Molecular Medicine, University of Texas Health Sciences Center at Houston, USA
| | - Petros Syrris
- Centre for Heart Muscle Disease, Institute of Cardiovascular Science, University College London, London, UK.
| |
Collapse
|
5
|
Finlay M, Bhar-Amato J, Ng KE, Santos D, Orini M, Vyas V, Taggart P, Grace AA, Huang CLH, Lambiase PD, Tinker A. Autonomic modulation of the electrical substrate in mice haploinsufficient for cardiac sodium channels: a model of the Brugada syndrome. Am J Physiol Cell Physiol 2019; 317:C576-C583. [PMID: 31291141 DOI: 10.1152/ajpcell.00028.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A murine line haploinsufficient in the cardiac sodium channel has been used to model human Brugada syndrome: a disease causing sudden cardiac death due to lethal ventricular arrhythmias. We explored the effects of cholinergic tone on electrophysiological parameters in wild-type and genetically modified, heterozygous, Scn5a+/- knockout mice. Scn5a+/- ventricular slices showed longer refractory periods than wild-type both at baseline and during isoprenaline challenge. Scn5a+/- hearts also showed lower conduction velocities and increased mean increase in delay than did littermate controls at baseline and blunted responses to isoprenaline challenge. Carbachol exerted limited effects but reversed the effects of isoprenaline with coapplication. Scn5a+/- mice showed a reduction in conduction reserve in that isoprenaline no longer increased conduction velocity, and this was not antagonized by muscarinic agonists.
Collapse
Affiliation(s)
- Malcolm Finlay
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Justine Bhar-Amato
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Keat-Eng Ng
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Diogo Santos
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Michele Orini
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Vishal Vyas
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| | - Peter Taggart
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Andrew A Grace
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Christopher L-H Huang
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Pier D Lambiase
- Institute of Cardiovascular Science, University College London, London, United Kingdom
| | - Andrew Tinker
- William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, United Kingdom
| |
Collapse
|
6
|
Arcidiacono P, Webb CM, Brooke MA, Zhou H, Delaney PJ, Ng KE, Blaydon DC, Tinker A, Kelsell DP, Chikh A. p63 is a key regulator of iRHOM2 signalling in the keratinocyte stress response. Nat Commun 2018; 9:1021. [PMID: 29523849 PMCID: PMC5844915 DOI: 10.1038/s41467-018-03470-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Accepted: 02/14/2018] [Indexed: 02/06/2023] Open
Abstract
Hyperproliferative keratinocytes induced by trauma, hyperkeratosis and/or inflammation display molecular signatures similar to those of palmoplantar epidermis. Inherited gain-of-function mutations in RHBDF2 (encoding iRHOM2) are associated with a hyperproliferative palmoplantar keratoderma and squamous oesophageal cancer syndrome (termed TOC). In contrast, genetic ablation of rhbdf2 in mice leads to a thinning of the mammalian footpad, and reduces keratinocyte hyperproliferation and migration. Here, we report that iRHOM2 is a novel target gene of p63 and that both p63 and iRHOM2 differentially regulate cellular stress-associated signalling pathways in normal and hyperproliferative keratinocytes. We demonstrate that p63-iRHOM2 regulates cell survival and response to oxidative stress via modulation of SURVIVIN and Cytoglobin, respectively. Furthermore, the antioxidant compound Sulforaphane downregulates p63-iRHOM2 expression, leading to reduced proliferation, inflammation, survival and ROS production. These findings elucidate a novel p63-associated pathway that identifies iRHOM2 modulation as a potential therapeutic target to treat hyperproliferative skin disease and neoplasia.
Collapse
Affiliation(s)
- Paola Arcidiacono
- Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - Catherine M Webb
- Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - Matthew A Brooke
- Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - Huiqing Zhou
- Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
- Department of Molecular Developmental Biology, Radboud University, Nijmegen, The Netherlands
| | - Paul J Delaney
- Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - Keat-Eng Ng
- Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - Diana C Blaydon
- Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK
| | - Andrew Tinker
- The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Charterhouse Square, London, EC1M 6BQ, UK
| | - David P Kelsell
- Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK.
| | - Anissa Chikh
- Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, E1 2AT, UK.
| |
Collapse
|
7
|
Buyandelger B, Mansfield C, Kostin S, Choi O, Roberts AM, Ware JS, Mazzarotto F, Pesce F, Buchan R, Isaacson RL, Vouffo J, Gunkel S, Knöll G, McSweeney SJ, Wei H, Perrot A, Pfeiffer C, Toliat MR, Ilieva K, Krysztofinska E, López-Olañeta MM, Gómez-Salinero JM, Schmidt A, Ng KE, Teucher N, Chen J, Teichmann M, Eilers M, Haverkamp W, Regitz-Zagrosek V, Hasenfuss G, Braun T, Pennell DJ, Gould I, Barton PJR, Lara-Pezzi E, Schäfer S, Hübner N, Felkin LE, O'Regan DP, Brand T, Milting H, Nürnberg P, Schneider MD, Prasad S, Petretto E, Knöll R. ZBTB17 (MIZ1) Is Important for the Cardiac Stress Response and a Novel Candidate Gene for Cardiomyopathy and Heart Failure. ACTA ACUST UNITED AC 2015; 8:643-52. [PMID: 26175529 DOI: 10.1161/circgenetics.113.000690] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 07/02/2015] [Indexed: 12/30/2022]
Abstract
BACKGROUND Mutations in sarcomeric and cytoskeletal proteins are a major cause of hereditary cardiomyopathies, but our knowledge remains incomplete as to how the genetic defects execute their effects. METHODS AND RESULTS We used cysteine and glycine-rich protein 3, a known cardiomyopathy gene, in a yeast 2-hybrid screen and identified zinc-finger and BTB domain-containing protein 17 (ZBTB17) as a novel interacting partner. ZBTB17 is a transcription factor that contains the peak association signal (rs10927875) at the replicated 1p36 cardiomyopathy locus. ZBTB17 expression protected cardiac myocytes from apoptosis in vitro and in a mouse model with cardiac myocyte-specific deletion of Zbtb17, which develops cardiomyopathy and fibrosis after biomechanical stress. ZBTB17 also regulated cardiac myocyte hypertrophy in vitro and in vivo in a calcineurin-dependent manner. CONCLUSIONS We revealed new functions for ZBTB17 in the heart, a transcription factor that may play a role as a novel cardiomyopathy gene.
Collapse
|
8
|
Aziz Q, Thomas AM, Gomes J, Ang R, Sones WR, Li Y, Ng KE, Gee L, Tinker A. The ATP-Sensitive Potassium Channel Subunit, Kir6.1, in Vascular Smooth Muscle Plays a Major Role in Blood Pressure Control. Hypertension 2014; 64:523-9. [DOI: 10.1161/hypertensionaha.114.03116] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Qadeer Aziz
- From The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom (Q.A., A.M.T., Y.L., K.-E.N., L.G., A.T.); and Department of Medicine, University College London, London, United Kingdom (J.G., R.A., W.R.S., A.T.)
| | - Alison M. Thomas
- From The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom (Q.A., A.M.T., Y.L., K.-E.N., L.G., A.T.); and Department of Medicine, University College London, London, United Kingdom (J.G., R.A., W.R.S., A.T.)
| | - John Gomes
- From The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom (Q.A., A.M.T., Y.L., K.-E.N., L.G., A.T.); and Department of Medicine, University College London, London, United Kingdom (J.G., R.A., W.R.S., A.T.)
| | - Richard Ang
- From The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom (Q.A., A.M.T., Y.L., K.-E.N., L.G., A.T.); and Department of Medicine, University College London, London, United Kingdom (J.G., R.A., W.R.S., A.T.)
| | - William R. Sones
- From The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom (Q.A., A.M.T., Y.L., K.-E.N., L.G., A.T.); and Department of Medicine, University College London, London, United Kingdom (J.G., R.A., W.R.S., A.T.)
| | - Yiwen Li
- From The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom (Q.A., A.M.T., Y.L., K.-E.N., L.G., A.T.); and Department of Medicine, University College London, London, United Kingdom (J.G., R.A., W.R.S., A.T.)
| | - Keat-Eng Ng
- From The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom (Q.A., A.M.T., Y.L., K.-E.N., L.G., A.T.); and Department of Medicine, University College London, London, United Kingdom (J.G., R.A., W.R.S., A.T.)
| | - Lorna Gee
- From The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom (Q.A., A.M.T., Y.L., K.-E.N., L.G., A.T.); and Department of Medicine, University College London, London, United Kingdom (J.G., R.A., W.R.S., A.T.)
| | - Andrew Tinker
- From The Heart Centre, William Harvey Research Institute, Barts and the London School of Medicine and Dentistry, London, United Kingdom (Q.A., A.M.T., Y.L., K.-E.N., L.G., A.T.); and Department of Medicine, University College London, London, United Kingdom (J.G., R.A., W.R.S., A.T.)
| |
Collapse
|
9
|
Neary MT, Ng KE, Ludtmann MHR, Hall AR, Piotrowska I, Ong SB, Hausenloy DJ, Mohun TJ, Abramov AY, Breckenridge RA. Hypoxia signaling controls postnatal changes in cardiac mitochondrial morphology and function. J Mol Cell Cardiol 2014; 74:340-52. [PMID: 24984146 PMCID: PMC4121533 DOI: 10.1016/j.yjmcc.2014.06.013] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 06/11/2014] [Accepted: 06/17/2014] [Indexed: 12/17/2022]
Abstract
Fetal cardiomyocyte adaptation to low levels of oxygen in utero is incompletely understood, and is of interest as hypoxia tolerance is lost after birth, leading to vulnerability of adult cardiomyocytes. It is known that cardiac mitochondrial morphology, number and function change significantly following birth, although the underlying molecular mechanisms and physiological stimuli are undefined. Here we show that the decrease in cardiomyocyte HIF-signaling in cardiomyocytes immediately after birth acts as a physiological switch driving mitochondrial fusion and increased postnatal mitochondrial biogenesis. We also investigated mechanisms of ATP generation in embryonic cardiac mitochondria. We found that embryonic cardiac cardiomyocytes rely on both glycolysis and the tricarboxylic acid cycle to generate ATP, and that the balance between these two metabolic pathways in the heart is controlled around birth by the reduction in HIF signaling. We therefore propose that the increase in ambient oxygen encountered by the neonate at birth acts as a key physiological stimulus to cardiac mitochondrial adaptation. The reduction in HIF signaling encountered by the heart following birth acts as a physiological switch. Reduced postnatal cardiac HIF signaling affects mitochondrial number, structure and function. Experimental study of mitochondria is prone to artifacts due to the effect of oxygen. Cardiomyocytes employ multiple strategies to function in low oxygen in utero.
Collapse
Affiliation(s)
- Marianne T Neary
- MRC National Institute for Medical Research, Mill Hill, London NW7 1AA
| | - Keat-Eng Ng
- MRC National Institute for Medical Research, Mill Hill, London NW7 1AA
| | | | - Andrew R Hall
- The Hatter Cardiovascular Institute, London WC1E 6HX
| | | | - Sang-Bing Ong
- The Hatter Cardiovascular Institute, London WC1E 6HX
| | | | - Timothy J Mohun
- MRC National Institute for Medical Research, Mill Hill, London NW7 1AA
| | | | - Ross A Breckenridge
- MRC National Institute for Medical Research, Mill Hill, London NW7 1AA; UCL Division of Medicine, London WC1E 6JJ
| |
Collapse
|
10
|
Breckenridge RA, Piotrowska I, Ng KE, Ragan TJ, West JA, Kotecha S, Towers N, Bennett M, Kienesberger PC, Smolenski RT, Siddall HK, Offer JL, Mocanu MM, Yelon DM, Dyck JRB, Griffin JL, Abramov AY, Gould AP, Mohun TJ. Hypoxic regulation of hand1 controls the fetal-neonatal switch in cardiac metabolism. PLoS Biol 2013; 11:e1001666. [PMID: 24086110 PMCID: PMC3782421 DOI: 10.1371/journal.pbio.1001666] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 08/15/2013] [Indexed: 12/15/2022] Open
Abstract
This study reveals a novel pathway that responds to hypoxia and modulates energy metabolism by cardiomyocytes in the mouse heart, thereby determining oxygen consumption. 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 hearts, accompanying re-expression of several “fetal” genes whose role in disease phenotypes remains unknown. Here we show that hypoxia-controlled expression of the transcription factor Hand1 determines oxygen consumption by inhibition of lipid metabolism in the fetal and adult cardiomyocyte, leading to downregulation of mitochondrial energy generation. Hand1 is under direct transcriptional control by HIF1α. Transgenic mice prolonging cardiac Hand1 expression die immediately following birth, failing to activate the neonatal lipid metabolising gene expression programme. Deletion of Hand1 in embryonic cardiomyocytes results in premature expression of these genes. Using metabolic flux analysis, we show that Hand1 expression controls cardiomyocyte oxygen consumption by direct transcriptional repression of lipid metabolising genes. This leads, in turn, to increased production of lactate from glucose, decreased lipid oxidation, reduced inner mitochondrial membrane potential, and mitochondrial ATP generation. We found that this pathway is active in adult cardiomyocytes. Up-regulation of Hand1 is protective in a mouse model of myocardial ischaemia. We propose that Hand1 is part of a novel regulatory pathway linking cardiac oxygen levels with oxygen consumption. Understanding hypoxia adaptation in the fetal heart may allow development of strategies to protect cardiomyocytes vulnerable to ischaemia, for example during cardiac ischaemia or surgery. Regulation of oxygen usage in cardiomyocytes is of great medical interest, because adult cardiac tissue is extremely vulnerable to hypoxia during myocardial infarction and cardiac surgery. While some progress has been made toward protecting cardiomyocytes from hypoxia in these circumstances, it has been limited by a lack of understanding of endogenous oxygen-sensing pathways. In contrast to adult cardiac tissue, embryonic cardiomyocytes are highly resistant to hypoxia, although the mechanisms underlying this have hitherto been unclear. Using mice we show that the transcription factor Hand1 is expressed at high levels in the fetal heart, under direct control of HIF1α signaling, a pathway well known to respond to hypoxia. We show that Hand1 expression decreases at birth as the neonate is exposed to higher levels of oxygen. By experimentally increasing Hand1 expression in the neonatal heart, we see lower oxygen consumption in cardiomyocytes and this is caused by Hand1 repressing key regulatory genes involved in cardiomyocyte lipid metabolism. This has the effect of decreasing mitochondrial ATP generation via the tricarboxylic acid cycle. Furthermore, we show that increasing Hand1 expression in adult transgenic hearts is protective against myocardial infarction, suggesting that a hypoxia–Hand1 pathway may also be of importance in the adult heart.
Collapse
Affiliation(s)
- Ross A. Breckenridge
- Developmental Biology, MRC–National Institute for Medical Research, London, United Kingdom
- Division of Medicine, University College London, London, United Kingdom
- * E-mail:
| | - Izabela Piotrowska
- Developmental Biology, MRC–National Institute for Medical Research, London, United Kingdom
| | - Keat-Eng Ng
- Developmental Biology, MRC–National Institute for Medical Research, London, United Kingdom
| | - Timothy J. Ragan
- Division of Molecular Structure, MRC–National Institute for Medical Research, London, United Kingdom
| | - James A. West
- Department of Biochemistry, Cambridge University, Cambridge, United Kingdom
| | - Surendra Kotecha
- Developmental Biology, MRC–National Institute for Medical Research, London, United Kingdom
| | - Norma Towers
- Developmental Biology, MRC–National Institute for Medical Research, London, United Kingdom
| | - Michael Bennett
- Developmental Biology, MRC–National Institute for Medical Research, London, United Kingdom
| | - Petra C. Kienesberger
- Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | | | - Hillary K. Siddall
- Hatter Institute, Institute of Cardiovascular Sciences, University College London, London, United Kingdom
| | - John L. Offer
- Physical Biochemistry, MRC–National Institute for Medical Research, London, United Kingdom
| | - Mihaela M. Mocanu
- Hatter Institute, Institute of Cardiovascular Sciences, University College London, London, United Kingdom
| | - Derek M. Yelon
- Hatter Institute, Institute of Cardiovascular Sciences, University College London, London, United Kingdom
| | - Jason R. B. Dyck
- Cardiovascular Research Centre, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
| | - Jules L. Griffin
- Department of Biochemistry, Cambridge University, Cambridge, United Kingdom
| | - Andrey Y. Abramov
- Institute of Neurology, University College London, London, United Kingdom
| | - Alex P. Gould
- Division of Physiology and Metabolism, MRC–National Institute for Medical Research, London, United Kingdom
| | - Timothy J. Mohun
- Developmental Biology, MRC–National Institute for Medical Research, London, United Kingdom
| |
Collapse
|
11
|
Ng KE, Joly P, Jayasinghe SN, Vernay B, Knight R, Barry SP, McComick J, Latchman D, Stephanou A. Bio-electrospraying primary cardiac cells: in vitro tissue creation and functional study. Biotechnol J 2011; 6:86-95. [PMID: 21053334 DOI: 10.1002/biot.201000125] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Manifestations of myocardial infarctions have been recognized as one of the major killers in the Western world. Therefore, advancing and developing novel cardiac tissue repair and replacement therapeutics have great implications to our health sciences and well-being. There are several approaches for forming cardiac tissues, non-jet-based and jet-based methodologies. A unique advantage of jet-based approaches is the possibility to handle living cells with a matrix for cell distribution and deposition in suspension, either as single or heterogeneous cell populations. Our previous studies on bio-electrospraying of cardiac cells have shown great promise. Here, we show for the first time the ability to bio-electrospray the three major cell types of the myocardium, both independently and simultaneously, for forming a fully functional cardiac tissue. Several samples are characterized in vitro and found to be indistinguishable in comparison to controls. Thus, we are describing a swiftly emerging novel biotechnique for direct cardiac tissue generation. Moreover, the present investigations pave the way for the development and optimization of a bio-patterning approach for the fabrication of biologically viable cardiac tissue grafts for the potential treatment of severe heart failure after myocardial infarction.
Collapse
Affiliation(s)
- Keat-Eng Ng
- Medical Molecular Biology Unit, University College London, Institute of Child Health, 30 Guilford Street, London, WC1N 1EH, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Buyandelger B, Ng KE, Miocic S, Piotrowska I, Gunkel S, Ku CH, Knöll R. MLP (muscle LIM protein) as a stress sensor in the heart. Pflugers Arch 2011; 462:135-42. [PMID: 21484537 PMCID: PMC3114083 DOI: 10.1007/s00424-011-0961-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 03/11/2011] [Accepted: 03/24/2011] [Indexed: 01/22/2023]
Abstract
Muscle LIM protein (MLP, also known as cysteine rich protein 3 (CSRP3, CRP3)) is a muscle-specific-expressed LIM-only protein. It consists of 194 amino-acids and has been described initially as a factor involved in myogenesis (Arber et al. Cell 79:221-231, 1994). MLP soon became an important model for experimental cardiology when it was first demonstrated that MLP deficiency leads to myocardial hypertrophy followed by a dilated cardiomyopathy and heart failure phenotype (Arber et al. Cell 88:393-403, 1997). At this time, this was the first genetically altered animal model to develop this devastating disease. Interestingly, MLP was also found to be down-regulated in humans with heart failure (Zolk et al. Circulation 101:2674-2677, 2000) and MLP mutations are able to cause hypertrophic and dilated forms of cardiomyopathy in humans (Bos et al. Mol Genet Metab 88:78-85, 2006; Geier et al. Circulation 107:1390-1395, 2003; Hershberger et al. Clin Transl Sci 1:21-26, 2008; Knöll et al. Cell 111:943-955, 2002; Knöll et al. Circ Res 106:695-704, 2010; Mohapatra et al. Mol Genet Metab 80:207-215, 2003). Although considerable efforts have been undertaken to unravel the underlying molecular mechanisms-how MLP mutations, either in model organisms or in the human setting cause these diseases are still unclear. In contrast, only precise knowledge of the underlying molecular mechanisms will allow the development of novel and innovative therapeutic strategies to combat this otherwise lethal condition. The focus of this review will be on the function of MLP in cardiac mechanosensation and we shall point to possible future directions in MLP research.
Collapse
Affiliation(s)
- Byambajav Buyandelger
- Myocardial Genetics, British Heart Foundation-Centre for Research Excellence, National Heart & Lung Institute, Imperial College, South Kensington Campus, Flowers Building, 4th floor, London, SW7 2AZ, UK
| | | | | | | | | | | | | |
Collapse
|
13
|
Ng KE, Schwarzer S, Duchen MR, Tinker A. The intracellular localization and function of the ATP-sensitive K+ channel subunit Kir6.1. J Membr Biol 2010; 234:137-47. [PMID: 20306027 DOI: 10.1007/s00232-010-9241-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Accepted: 03/04/2010] [Indexed: 10/19/2022]
Abstract
Our aim was to determine the subcellular localization and functional roles of the K(ATP) channel subunit Kir6.1 in intracellular membranes. Specifically, we focused on the potential role of Kir6.1 as a subunit of the mitochondrial ATP-sensitive K+ channel. Cell imaging showed that a major proportion of heterologously expressed Kir6.1-GFP and endogenously expressed Kir6.1 was distributed in the endoplasmic reticulum with little in the mitochondria or plasma membrane. We used pharmacological and molecular tools to investigate the functional significance of this distribution. The K(ATP) channel opener diazoxide increased reactive oxygen species production, and glibenclamide abolished this effect. However, in cells lacking Kir6.1 or expressing siRNA or dominant negative constructs of Kir6.1, the same effect was seen. Ca2+ handling was examined in the muscle cell line C2C12. Transfection of the dominant negative constructs of Kir6.1 significantly reduced the amplitude and rate of rise of [Ca2+]( c ) transients elicited by ATP. This study suggests that Kir6.1 is located in the endoplasmic reticulum and plays a role in modifying Ca2+ release from intracellular stores.
Collapse
Affiliation(s)
- Keat-Eng Ng
- Deparment of Medicine, The Rayne Institute, University College London, Room 107, University Street, London, WC1E 6JF, UK
| | | | | | | |
Collapse
|
14
|
Prin F, Ng KE, Thaker U, Drescher U, Guthrie S. Ephrin-As play a rhombomere-specific role in trigeminal motor axon projections in the chick embryo. Dev Biol 2005; 279:402-19. [PMID: 15733668 DOI: 10.1016/j.ydbio.2004.12.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2004] [Revised: 12/20/2004] [Accepted: 12/21/2004] [Indexed: 11/19/2022]
Abstract
In this study, we investigate the possible role of ephrin-Eph signaling in trigeminal motor axon projections. We find that EphA receptors are expressed at higher levels by rhombomere 2 (r2) trigeminal motor neurons than by r3 trigeminal motor neurons in the chick embryo. Mapping of rhombomere-specific axon projections shows that r2 and r3 trigeminal motor neurons project to different muscle targets, including the mandibular adductor and the intermandibularis muscles respectively. Ephrin-A5 is expressed in these muscles, especially in some regions of the intermandibularis muscle, and can cause growth cone collapse of both r2 and r3 motor axons in vitro. We demonstrate that in vivo overexpression of ephrin-A5 in the intermandibularis muscle, or overexpression of dominant-negative EphA receptors in trigeminal motor neurons leads to a reduction in branching of r3-derived motor axons specifically. Overexpression of full-length EphA receptors impairs the formation of r3 projections to the intermandibularis muscle. These findings indicate that ephrins and their Eph receptors play a role in trigeminal motor axon topographic mapping and in rhombomere 3-derived projections in particular.
Collapse
Affiliation(s)
- Fabrice Prin
- MRC Centre for Developmental Neurobiology, 4th Floor New Hunt's House, King's College, Guy's Campus, London SE1 1UL, United Kingdom
| | | | | | | | | |
Collapse
|
15
|
Abstract
In this paper a novel approach to the development of the architecture of a knowledge-based decision support system for the management of patients with cancer of the breast is described. Its initial design and subsequent realization in a prototype version was facilitated by examining closely the overall clinical task and identifying its associated activities and related knowledge. Implementation in KEE highlights the value of rigorous conceptual modelling that leads to a design able to assess treatment response and disease progression as well as providing specific therapy advice. The approach is general and may be applied to the development of decision support systems for other areas of cancer and medicine.
Collapse
Affiliation(s)
- M S Leaning
- Department of Statistical Science, University College London, UK
| | | | | |
Collapse
|
16
|
Abstract
The condensation reactions of activated nucleotides, ImpN or 2-MeImpN, with the self-complementary ribo-octanucleotide GCGCGCGC or with the partially self-complementary heptanucleotide GCGCGCG were studied. The template-directed reaction of 2-MeImpC with the heptamer yields the 3'-5' octamer as the main product. All other reactions yield 2'-5'-linked octamers and pyrophosphates as major products. Surprisingly, 2-MeImpG facilitates the reaction of 2-MeImpC with the heptamer. Procedures for the analysis by gel electrophoresis of the oligomeric products obtained in reactions of this kind are described.
Collapse
Affiliation(s)
- K E Ng
- Salk Institute for Biological Studies, San Diego, California 92138
| | | |
Collapse
|
17
|
Abstract
When aqueous solutions of adenosine-5'-mono-, di-, or triphosphates are treated with a water soluble carbodiimide the major product is the expected diadenosine-5'-5'-polyphosphate. The yields of these pyrophosphates are greatly increased in the presence of the Mg2+ ion. Adenosine-5'-tetraphosphate behaves differently. The major product is adenosine-5'-monophosphate. We believe that this hydrolysis occurs via a cyclic trimetaphosphate intermediate.
Collapse
|