lecture vi. making connections

September 14, 2009 Lecture VI. Making Connections 1

Lecture VI. Making Connections

Bio 3411 Monday

September 14, 2009

• T. Woolsey

• 3802 North Building

• 362-3601

• [email protected]

3Lecture VI. Making ConnectionsSeptember 14, 2009

Reading

NEUROSCIENCE: 4th ed, Chapter 23, pp 577-609

4Lecture VI. Making ConnectionsSeptember 14, 2009


Selected References:

Bentley, D., & Caudy, M. (1983). Pioneer axons lose directed growth after selective killing of guidepost cells. Nature, 304(5921), 62-65.

Foty, R. A., & Steinberg, M. S. (2004). Cadherin-mediated cell-cell adhesion and tissue segregation in relation to malignancy. Int J Dev Biol, 48(5-6), 397-409.

Hayashi, T., & Carthew, R. W. (2004). Surface mechanics mediate pattern formation in the developing retina. Nature, 431(7009), 647-652.

Moscona, A., & Moscona, H. (1952). The dissociation and aggregation of cells from organ rudiments of the early chick embryo. J Anat, 86(3), 287-301.

Myers, P. Z., & Bastiani, M. J. (1993). Cell-cell interactions during the migration of an identified commissural growth cone in the embryonic grasshopper. J Neurosci, 13(1), 115-126.

Sperry, R. W. (1963). Chemoaffinity in the Orderly Growth of Nerve Fiber Patterns and Connections. Proc Natl Acad Sci U S A, 50, 703-710.

Tessier-Lavigne, M., & Goodman, C. S. (1996). The molecular biology of axon guidance. Science, 274(5290), 1123-1133.

Townes, P. L., & Holtfreter, J. (1955). Directed movements and selective adhesion of embryonic amphibian cells. J Exp Zool, 123, 53–120.

Walter, J., Henke-Fahle, S., & Bonhoeffer, F. (1987). Avoidance of posterior tectal membranes by temporal retinal axons. Development, 101(4), 909-913.

Wilson, H. (1907). A new method by which sponges may be artificially reared. Science, 23, 161-174.

What the last Lecture was about

• Programmed cell death (apoptosis) is a physiological mechanism distinct from necrotic cell death.

• Apoptosis occurs widely during normal development of the nervous system.

• Isolation of specific molecules involved in promoting growth and survival – “trophism,” e.g., Nerve Growth Factor (NGF).

• What is the “death mechanism” that NGF (and other neruotrophins) inhibit?

• Broader implications: controlled cell death in neuroembryology vs uncontrolled cell growth of cancer.

• Gene homologies between organisms - humans and worms (nematodes)

• Molecular models for apoptosis

• How do trophic factors connect to this cell death pathway(s)?


What this Lecture is about

• General mechanisms for assembling neurons and groups of neurons

• Diffusion vs Contact

• Attraction vs Repulsion

• Examples of impacts of contact

• Examples of impacts of diffusion

• Specification by growth factors

• The chemoaffinity hypothesis


September 14, 2009 9Lecture VI. Making Connections

Fertilization

Embryonic morphogenesis

Induction of Neuroectoderm

Neurulation

Differentiation:1. Formation and placement of neuroblasts2. Axonal outgrowth3. Growth cones, selective migration4. Selective fasciculation5. Target selection6. Synaptogenesis7. Etc…(cell shape, neurotransmitter, ionic channels, receptors)

Adult neuronal plasticity(Activity-dependent?)

Segm

enta

tion

Outline of Neurodevelopment

Selective Adhesion Determines Specificity of Tissue and Cellular Associations


Selective Aggregation of dissociated embryonic tissues (vertebrate and invertebrate) suggests ancient (surface)

Adhesion Molecules


(Townes and Holtfretter, 1955)

1. Sponges (Wilson, 1907)

2. Amphibians (Townes and Holtfretter, 1955)

3. Chick (Moscona, 1952)

Epidermis+

Mesoderm


Experimental recreation of morphogenesis by mixing cells expressing low and high levels of one surface

adhesion gene (N-cadherin)

Green = high N-cadherinRed = low N-cadherin

+4 hrs +24 hrs

(Foty and Steinberg, 2004)


Effect/Proximity

Attraction Repulsion

DistantContact


(Play GFP-Actin Growth Cone Movie)Dr. Andrew Matus

Friedrich Miescher Institute, Switzerland

E:\ADW-D on Aguan's office (Salk-adw)\OLD DRIVE D\Bio3411\Fall 02\Lecture 18 - Making Connections\Movies\WMediaPlayer\GroCone1.mov

Conserved Structural Classes of Axonal Guidance Molecules: Modular Construction and Multifunctionality

1. Laminin, fibronectin and extracellular matrix proteins.2. Cadherins and catenins. (Ca+2 dependent)3. Cell adhesion molecules (CAMs) (containing IgG domains).4. Receptor tyrosine kinases and receptor phosphatases.


Molecules Mediating Axonal Guidance


Screen for Mutantsof Neuronal Specificity

Clone Mutant Genes

Observe WTNeuronal Specificity

IdentifyFactors

(Semphorins, Slit,Robo, Commissureless...)


Drosophila robo disrupts longitudinal

tract formation

Robo acts as a receptor for a midline repulsive cue

Retinotectal Mapping Visualized by Dye Injection in Zebrafish


VD

N

T

DV

N

T

(Friche,et al. 2001)

Zebrafish ROBO Mutant (astray)Disrupts Midline Retinotectal Axonal Projections


WT WT

ast WT ast WT

WT ast

What this Lecture was about

• Grouping neurons and processes

• Partner selection

• Some genetic foundations/correlates

• Systematic organization of connections

• Roles of contact and diffusion

• Deja vu


Sequential Restrictions (Refinements) are the Bases for Development


pluripotent, stem cell

differentiated

genetic

environmental


FInis


Human ROBO Mutation causes HGPPS(Horizontal Gaze Palsy with

Progressive Scoliosis)

HG

PP

SN

orm

al

(reduced hindbrain volume) (scoliosis)

(horizontal gaze palsy)

(Jen, et al., 2004)

The Axon Guidance Receptor Gene ROBO1Is a Candidate Gene for Developmental Dyslexia

Katariina Hannula-Jouppi1, Nina Kaminen-Ahola1, Mikko Taipale1,2, Ranja Eklund1, Jaana Nopola Hemmi1,3,Helena Kaariainen4,5, Juha Kere1,6*

1 Department of Medical Genetics, University of Helsinki, Finland, 2 European Molecular Biology Laboratory, Gene Expression Programme, Heidelberg, Germany,3 Department of Pediatrics, Jorvi Hospital, Espoo, Finland, 4 Department of Medical Genetics, The Family Federation of Finland, Helsinki, Finland, 5 Department of Medical Genetics, University of Turku, Turku, Finland, 6 Department of Biosciences at Novum and Clinical Research Centre, Karolinska Institutet, Stockholm, Sweden

PLOS Genetics (2005) 1: 0467



Physical forces of surface contacts largely determine cell shape:Drosophila cone cell morphology modeled by soap bubbles!

(1 cell)

(2 cells)

(3 cells)

(5 cells)

(6 cells)

DrosophilaRough eye (Roi) mutants

Drosophila retina

WT

(4 cells) Soap bubbles

Hayashi & Carthew, (2004)

September 14, 2009

Do Molecular Cues Determine the Retinotectal Spatial-topic Map?

39Lecture VI. Making Connections

A(T)D

V

T N

RetinaP(N)

M(D)

L(V)

Optic Tectum

A(T)

P(N)

dorsal ventral

temporal nasal

L(V)

M(D)Optic tectum

Retinotectal Map is Preserved Despite Experimental Rotation of the Eye:“Chemaffinity Hypothesis”


(Sperry, 1956)

D

V

T N

Retina Optic Tectum

(T)

(N)

(D) (V)Subjective “up”

Rot

ate

Eye

180

o

N

V

D

T

(T)

(N)

(D) (V)Subjective “down”

Subjective “down”

Early Embryonic Insect Neurons form a Repeated Segmental Scaffold: Favorable preparation for studying

axonal guidance


Grasshopperembryo

CommissuralTracts

Longitudinal

Tracts

Identified Neurons

Q1 pCCaCC

MP1

Q1

Q1

MP1

MP1

pCCaCC

Q1(Meyers and Bastiani, 1993)

Pioneer Neurons Create the Early Scaffold of the Adult Nervous System


pioneer neuron

guidepost cells

growth cone

selectivefasciculation

Pioneer neuron and guidepost cells may die after pathway is pioneered,

by apoptosis

Molecules Mediating Axonal Guidance

1. Biochemical approach: Friedrich Bonhoeffer, retinotectal culture assay.

43

Temporal Nasal

Functional Assay

Fractionate Native Factors

ObserveNeuronal Specificity

Purify and IdentifyFactor

(Ephrins...)

Temporal AxonsNasal Axons

September 14, 2009 Lecture VI. Making Connections

Pioneer Neurons and Guidepost Cells guide the initial path of peripheral nervetracts in embryonic grasshopper

limbs

(Bentley and Caudy, 1983)


PioneerNeurons

Guidepost Cells Growth Cone

CT1 Photoablated Control

Growth Cones are Dynamic Sensory Organelles that Guide the Growth of Embryonic Axons


(Forscher lab)

Sensing and Transducing:• Diffusible Cues• Contact-dependent Cues• Trophic Factors• Neurotransmitters

F-actin

Tubulin

lamellipodia

filapodia

Extracellular Cues

Intracellular SignalingPathways

CytoskeletalRearrangment

Ca+2

GTPcAMP

2ndMessengers

Functional Classes of Axonal Guidance Molecules

(Secreted)

(Membrane Associated)

(netrin) (sema, slit)

(fas) (eph)

Molecules may function for both:1. Selective adhesion2. Intracellular signaling


Axonal Guidance Cues


selectivefasciculation

diffusibleattractant

diffusiblerepellant

Contact-dependentattractant

Contact-dependentrepellant

(Timing is critical)

lecture vi. making connections

Documents

cellcell interactions

controlled cell death

necrotic cell death

cell death pathways

directed growth

death mechanism

nerve growth factor

j neurosci