(and glial cells)

Pietro De Camilli

October 11, 2012 Golgi Stain

Camillo Golgi Cajal Genetically encoded dyes

Martin Chalfie

Aequorea victoria green fluorescent

Jeff Lichtman Roger Tsien Genetically encoded dyes

Brainbows

Jeff Lichtman Neurons have a variety of shapes as polarized cells

(typically only one)

Stages of axonal development (in vitro)

axon Dotti and Banker Axon and dendrites have different properties

perikaryon cell body

DENDRITES AXON (INPUT) (OUTPUT)

Nerve cell grown in vitro

Red: axonal marker Green: dendritic marker Both dendrites and can be extremely branched axons are typically longer (can be much longer)

axon and dendrites of a single neuron

Inhibitory (dendrites blue, axon red) shown adjacent to a schematic of a hippocampal pyramidal neuron

http://www.clp.northwestern.edu/news/rewrite-textbooks-findings-challenge-conventional-wisdom-how-neurons-operate Neurons are organized in neuronal circuits

Schematic diagram of the neuronal circuit mediating tail and siphon withdrawal reflex in Aplysia (an invertebrate organism)

Demian Barbas, Luc DesGroseillers, Vincent F. Castellucci, et al. Learn. Mem. 10: 373, 2003 Key compartments of the neuron: cell body (soma, perikaryon) dendrites axons NeuronalMotor Neurons perikarya Ventral Horn blood capillary Most organelles of the cell body extend into the main dendritic branches

Cell body or Nissl substance = RER perikaryon

Axon hillock NeuronalMotor Neurons perikarya Ventral Horn blood capillary Entry of organlles in axons is selective. Dendrite There are no rough or ribosomes (and thus no protein synthesis) and Golgi complex in mature axons Cell body or Nissl substance = RER perikaryon

Axon hillock

Axon hillock Purkinje cells Purkinje cells (cerebellum) (cerebellum) Dendritic trees

Purkinje cells (cerebellum)

Dendritic spines axons Golgi complex Neuron Cytoplasm

RER

Golgi Complex Golgi complex Neuron Cytoplasm

RER

Silver impregnation Golgi (From Camillo Golgi) Complex

immunofluorescence Axon size The length of the axons poses special needs:

-Structural support -Assisted organelle transport -Local synthesis and degradation of metabolites -Signal propagation Axons are surrounded by glial cells

Unmyelinated Axons Axons are surrounded by glial cells Axon Myelinated axon

Schwann cells (PNS) (CNS)

Development of myelin Myelin

Development of myelin Node of Ranvier Node of Ranvier, EM K+ channel Na+ channel βIV-spectrin K+ channel Node of Ranvier

mutation: quivering mouse

Nodes of Ranvier A prominent cytoskeletal scaffold

Myelinated Axon Quick-freeze-deep-etch view longitudinal-section From Hirokawa Axonal transport • Anterograde, slow 2-4 mm/day – cytosolic , cytoskeletal elements… • Anterograde, fast (kinesins) 100-400 mm/day – organelles, particles

• Retrograde, fast (cytoplasmic dynein) – organelles, particles (, targeting to lyososomes) Organelle transport (microtubular motors in axonal cytoplasm)

From Paul Forscher From Nabutaka Hirokawa Microtubular motors: kinesin(s) and cytoplasmic dynein

A multiplicity of kinesins (different cargo vesicles) Axonal block

From Tsukita and Ishikawa Weiss axoplasmic flow

Proximal to axonal block Distal to axonal block A continuous smooth ER from the cell body to

arrows = endoplasmic reticulum From Broadwell and Cataldo, 1984 Several forms of hereditary spastic paraplegias are due to mutations in proteins that control the shape and the dynamics of the ER Signal propagation in axons Unmyelinated 4.6 mM 140 mM

K+ + closed opened Na inactivated closed Conduction 0.6-2 m/sec + + + + - - - - - + +

+ + + + + + Na+ + + + + + -70 mV unmyelinated nerveK

17 mM Na+ channel 90 mM

gradient of Na+ and K+ across the plasma membrane is mantained by Na+/K+ ATPase Signal propagation in axons Myelinated nerve

Saltatory conduction opened closed inactivated - - Conduction 5-120 m/sec

+ +

+ +

- -

nodes of Ranvier Growth cones

DIC

attraction/repulsion

Microtubules

Actin Lab of Paul Forscher filaments Elke Stein Growth Cone

Lab of Paul Forscher, Yale Axonal Degeneration and Regeneration

Axon regeneration occurs in the peripheral but does not occur in the of the

white matter gray matter

Model organisms tools to study principles in neurons and circuits development

Caenorhabditis elegans

302 neurons (instead of billions as in the human brain)

wild type daf-18 mutant

AIY neurons Colon Ramos lab Axonal Regeneration

Axotomy Regeneration

Lab of Marc Hammarlund, Yale CNNR Glial cells Glial cells Glial cells

ASTROCYTES

Structural support Physical isolation of neurons Buffer of extracellular ions (f.e.sink for K+) Uptake /clearance of of Metabolic functions to support neurons Secretion of growth factors Response to injury Blood-brain barrier Radial tracks for neuronal migration during brain development

from F. Polleaux

developing cerebral cortex: the youngest cells are the ones closests to the pial surface Myelin generating cells: Oligodendrocytes (CNS) & Schwann cells (PNS)

Schwann cells = peripheral Oligodendrocytes = central nervous system nervous system Multiple Sclerosis (MS)

1. Inflammation 2. Demyelination 3. Impairment of nerve conduction 4. Neurological deficits

plaques

Macrophage engulfing myelin in experimental autoimmune encephalytis (EAE)mouse model for MS Remyelination I. Recruitment phase (Proliferation, Migration)

Acute lesion Recruitment of OPCs

Oligodendrocyte progenitor cells (OPCs) Franklin NatRevNeurosci 2002 the macrophages of the brain Microglia

Wenbiao Gan (NYU) Neurodegeneration

Alzheimer plaques iPS cells Motor neurons from patient with ALS

Dimos/Eggan Lab at HSCI.

John B. Gurdon, Shinya Yamanaka 2012 Physiology and Medicine Nobel Prize Gensat project http://www.gensat.org/index.html

different shapes and differential gene expression

NIH funded, publicly available gene expression atlas of the developing and adult nervous system