Lecture: Introduction to nervous system development Prof. Ilan Davis, Department of Biochemistry. Wellcome Senior Research Fellow Senior Research Fellow, Jesus College ilan.davis@bioch.ox.ac.uk http://www.ilandavis.com
References Molecular Biology of the Cell, Sixth Edition Authors: Alberts et al. Chapter 21: Development of Multicellular Organisms Principles of Neurobiology, 1st Edition Author: Liqun Luo ISBN: 9780815344926 For movies: http://garlandscience.com/ (click on student and register for resources)
Content of lectures 3 1. How does the human brain develop? 2. Janelia Research Campus 3. The brain initiative 4. The human brain and MRI 5. The mouse brain 6. The steps of brain development in a nutshell 7. The anatomy of neurons 8. Axon pathfinding 9. Memory and learning 10. Synaptic plasticity and localised translation 11. Optogenetics
How does the human brain develop and function in health and disease? 11 10 neurons 4 10 11 connections
https://www.janelia.org
The Brain initiative
The human brain
Using MRI scanning to record brain activity in humans Major drawbacks: Poor resolution - single cell imaging not possible Poor specificity - imaging specific molecules not possible
The mouse brain
Regions of the mammalian brain are organised into layers Camillo Golgi Ramon Y Cajal Brainbow 1843-1926 1852-1934 Silver Nitride stain Randomly expressed red, green and blue fluorescent proteins
Brain development and function? Specify the correct neurons in the right place Create appropriate circuits - axon path finding Modulate the connections Synaptic plasticity Human brain: ~10 10 neurons ~10 14 synapses
Brain development in a nutshell
Typical mammalian neutron and glia
There are many types of neurons
Axon pathfinding in Xenopus
Cytoskeleton and molecular motors in neurons
Memory What is the molecular mechanism of memory formation? Known Unknown
The organisation of the human central nervous system (CNS)
Long term potentiation (LTP) Figure Legend: (A) Experimental setup. The stimulating electrode was placed at the perforant path, which consists of axons that innervate dentate gyrus granule cells. A second electrode was placed near the granule cell bodies to record the field excitatory postsynaptic potential (fepsp), which represents the collective EPSPs from the population of granule cells near the recording electrode. Axons of dentate gyrus granule cells form the mossy fibers. (B) High-frequency stimulations (downward arrows, each representing 10 s of 15-Hz stimulation) caused an increase in the amplitude of fepsps produced afterward by single stimuli (green dots) compared to controls (yellow dots, no highfrequency stimulation). (Adapted from Bliss TVP & Lomo T [1973] J Physiol 232:331 356. With permission from The Physiological Society.)
Synaptic plasticity Dendrite Inhibitory input Axon Axons Excitatory input Dendrite Dendrite New connection Strengthen or weaken existing connection
Live cell imaging of the NMJ during chemical activation (assay for synaptic plasticity) Ataman et.al 2006 Lu Yang and mcd8-gfp Ilan Davis in (unpublished) motorneurons Richard Parton Ataman et al Neuron 2008 http://dx.doi.org/10.1016/j.neuron.2008.01.026
Much is known about LTP and synaptic plasticity at the molecular level Dlg CamKII Scaffolding Vesicles Membranes Neurotransmitters Ion receptors Calcium channels Calcium binding Signalling Actin Microtubules Translation machinery Calabrese et al. 2006 DOI: 10.1152/physiol.00042.2005
The big unknowns Dendrites Axon 1) Synapses in different parts of cell are modulated independently 2) Distance from cell body to synapses too large for transcriptional regulation
Hypothesis: local translation Dendrites Axon 1) mrnas present at dendrite and axon termini 2) Local translation of pre-synaptic mrna
Arc mrna moves into dendrites in response to neuronal activation Sections of mouse brains O Steward (2001) PNAS Colloquium. A cellular mechanism for targeting newly synthesized mrnas to synaptic sites on dendrites www.pnas.org/content/98/13/7062.full.pdf
More support for the hypothesis Wang et al and Kelsey C. Martin. (2009) Synapse- and stimulus-specific local translation during long-term neuronal plasticity, Science, 324, 1536-1540, 2009. https://www.ncbi.nlm.nih.gov/pmc/articles/pmc2821090/pdf/nihms174880.pdf Susanne tom Dieck, Cyril Hanus, and Erin M. Schuman (2014) Neuron 81: 958 958.e1 SnapShot: Local Protein Translation in Dendrites http://brain.mpg.de/fileadmin/user_upload/documents/papers/papers_schuman/tom_dieck_et_al_2014.pdf Toshiaki Shigeoka et al, and Christine E. Holt (2016) Cell 166: 181. Dynamic Axonal Translation in Developing and Mature Visual Circuits. http://www.cell.com/cell/pdf/s0092-8674(16)30580-3.pdf
How does optogenetics work? A light sensitive ion channel cloned from algae into transgenic flies The channel rhodopsin is expressed in a specific set of neurones using the GAL4/UAS system ion channel opens when exposed to blue light A flash of blue light causes the neurones to fire
Optogenetics - channel rhodopsin Wild type control Thomas Germe and Ilan Davis
Thanks Any questions?
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