The role of oligodendrocytes in higher-order circuit functions Dissertation for the award of the degree “Doctor rerum naturalium” of the Georg-August-Universität Göttingen within the doctoral program IMPRS Neuroscience of the Georg-August University School of Science (GAUSS) Submitted by Sharlen Yared Moore Corona From Mexico City, Mexico Göttingen 2018 Thesis Committee Dr. Livia de Hoz (Supervisor) Department of Neurogenetics, Max Planck Institute of Experimental Medicine Prof. Klaus-Armin Nave, PhD (Reviewer) Department of Neurogenetics, Max Planck Institute of Experimental Medicine Prof. Dr. Mikael Simons (Reviewer) Institute of Neuronal Cell Biology Technical University Munich German Center for Neurodegenerative Diseases Prof. Dr. Swen Hülsmann Experimental Neuroanesthesiology, University Medical Center Göttingen Members of the Examination Board Prof. Dr. Tobias Moser University Medical Center Göttingen Institute for Auditory Neuroscience & InnerEar Lab Camin Dean, Ph.D. Trans-synaptic Signaling group European Neuroscience Institute, Göttingen Prof. Dr. Ralf Heinrich Department of Cellular Neurobiology Schwann-Schleiden Research Centre Date of oral examination: 5th, June, 2018. Table of contents Abstract …...........................................................................................................................1 I. Preface .............................................................................................................................3 I.I. Myelin: not the textbook ‘insulator’ .....................................................................3 I.II. Myelin in gray-and-white ......................................................................................4 I.III. The multiple players of conduction velocity regulation ...................................5 I.IV. Myelin pathologies ..............................................................................................6 I.V. Adaptive myelination and the role of oligodendrocytes in shaping neuronal circuits .........................................................................................................................7 I.VI. Myelin relevance in sensory processing and cognitive functions .................7 I.VII. Myelin basic protein: a handle into myelin manipulation ...............................9 II. Materials and Methods .........................................................................................11 II.I. Animals ................................................................................................................11 II.I.I Complete dysmyelination model ..........................................................11 II.I.II. Partial dysmyelination model ..............................................................11 II.I.III. Axo-glial metabolic deficiency model ...............................................12 II.I.IV. Myelinating-cells metabolic deficiency model .................................12 II.II. Wide-use solutions.............................................................................................13 II.II.I. Fixatives ................................................................................................13 II.II.II. Anesthetics ..........................................................................................13 II.III Data management and analysis generalities ...................................................13 II.IV. Electron microscopy ........................................................................................14 II.IV.I. Solutions ..............................................................................................14 II.IV.II. Procedure ...........................................................................................14 II.V. Acute electrophysiology ...................................................................................15 II.V.I. Surgical procedure ..............................................................................15 II.V.II. Specifics of experimental animals ....................................................16 II.V.III. Data acquisition .................................................................................17 II.V.IV. Acoustic stimulation .........................................................................17 II.V.V. Sound protocols .................................................................................18 II.V.V.I. Frequency sweep ..................................................................18 II.V.V.II Click-tracing sweep ..............................................................18 II.V.V.III. Two broad-band noise pulses separated by a gap……....18 II.V.V.IV. Oddball protocol .................................................................18 II.V.VI. Analysis ..............................................................................................20 II.V.VI.I. General information .............................................................20 II.V.VI.II. Post-stimulus time histogram ............................................20 II.V.VI.III. Baseline activity .................................................................21 II.V.VI.IV. Latency ...............................................................................21 II.V.VI.V. Peak activity ........................................................................21 II.V.VI.VI. Temporal reliability ............................................................21 II.V.VI.VII. Temporal acuity ................................................................22 II.V.VI.VII.I. Assessment of the response to the first pulse ........................................................................................22 II.V.VI.VII.II. Assessment of gap-detection ...........................23 II.V.VI.VIII. Tuning ...............................................................................23 II.V.VI.IX. Stimulus-specific adaptation ............................................23 II.VI. Auditory brainstem recordings .......................................................................24 II.VI.I. Procedure and acquisition .................................................................24 II.VI.II. Specifics of experimental animals ...................................................25 II.VI.III. Analysis .............................................................................................26 II.VII. Optic nerve recordings ...................................................................................26 II.VII.I. Solutions and electrodes ..................................................................26 II.VII.II. Optic nerve preparation and stimulation ........................................27 II.VII.II.I. Current-voltage dependence ..............................................28 II.VII.II.II. Ramp stimulation ...............................................................28 II.VII.III. CAP analysis ....................................................................................28 II.VII.III.I CAP amplitude during IV curves ........................................29 II.VII.III.II. Depolarizing and hyperpolarization area ........................29 II.VII.III.III. High-rate stimulation ........................................................29 II.VII.III.IV. Conduction velocity .........................................................30 II.VIII. Axon initial segment length quantification ..................................................30 II.VIII.I. Solutions and antibodies .................................................................30 II.VIII.II. Immunostaining ...............................................................................30 II.VIII.III. Imaging ............................................................................................31 II.VIII.IV. Analysis ...........................................................................................31 II.IX. Behavioral paradigms ......................................................................................31 II.IX.I. Pre-pulse inhibition of the startle reflex using silent gaps …..…....31 II.IX.I.I. Specifics of experimental animals .......................................32 II.IX.I.II. Protocol and acquisition ......................................................32 II.IX.I.III. Gap-PPI analysis .................................................................33 II.IX.II. AudioBox ............................................................................................34 II.IX.II.I. Behavioral system and animal procedure .........................34 II.IX.II.II. Gap detection paradigm .....................................................37 II.IX.II.III. Analysis ...............................................................................38 II.X. Paw preference test ...........................................................................................39 II.X.I. Test paradigm .......................................................................................39 II.X.II. Analysis ...............................................................................................41 Chapter 1 - Not quite my tempo: auditory abnormalities caused by dysmyelination .......................................................................................................43 1.1 Introduction .........................................................................................................43 1.1.1. Hearing and sound ..............................................................................43 1.1.2. Temporal processing ..........................................................................44