Farrer Lecture on Nerve Growth

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Questions and Answers

What is the main function of the optic chiasm in the brain?

To allow optic nerves to cross and facilitate depth perception (correct)

To regulate the eye's focus

To connect the optic nerves to the spinal cord

To process auditory signals

Which part of the retina sends its projections across to the opposite side of the brain?

Temporal part

Central part

Nasal part (correct)

Peripheral part

What change occurs in the eye positioning of frogs during metamorphosis?

Eyes remain in the same position but change shape

Eyes shift to the top of the head and gain binocularity (correct)

Eyes become completely hidden during metamorphosis

Eyes move laterally and develop a monocular vision

What role does the molecule Efrin B play in the development of frog eyes?

Promotes axon growth towards the midline without crossing Signup and view all the answers

What advantage do animals with frontal positioned eyes have compared to those with laterally positioned eyes?

Enhanced depth perception through binocular vision Signup and view all the answers

What is necessary for axonal growth cone regeneration?

Local protein synthesis Signup and view all the answers

What might be the role of mitochondria in axon maintenance?

Regulating local protein synthesis Signup and view all the answers

What does the initial navigation analogy suggest about axon pathways?

Existing pathways dictate axonal growth direction Signup and view all the answers

Who was recognized for their long-term collaboration in the research discussed?

Bill Harris Signup and view all the answers

What can be inferred about the nature of mitochondrial genes in axons?

They are crucial for axonal health across all ages Signup and view all the answers

What happens to the Caida protein's color when exposed to UV light?

It changes irreversibly to red. Signup and view all the answers

What indicates the synthesis of new Caida protein in the growth cone after netrin is added?

The green signal returns. Signup and view all the answers

What role does the molecule NFPC play in the experiment?

It is an adhesion molecule. Signup and view all the answers

Which guidance molecule is associated with the axon bending observed in the mid part of the tract?

SAMA3A Signup and view all the answers

What observation was made about the growth cones in the lower tract after photo-conversion?

They did not return the green signal. Signup and view all the answers

How does netrin influence the growth cone in a gradient?

By promoting actin assembly on the near side of the growth cone. Signup and view all the answers

What happens to the growth cone's behaviour in a repulsive gradient when beta-actin translation is blocked?

The growth cone still turns away from the gradient. Signup and view all the answers

What role does cofilin play in the growth cone's response to repellents?

It disassembles the actin cytoskeleton on the near side. Signup and view all the answers

What characterizes the differential translation model in response to external signals?

Different sets of RNAs are translated depending on the activated receptors. Signup and view all the answers

What is the main outcome of the polarised recruitment and translation process in a gradient of attractant?

Directional bias towards the source of the attractant. Signup and view all the answers

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Study Notes

Introduction to Farrer Lecture

The Biological Secretary of the Royal Society, John Scahill, introduced the Farrer Lecture, awarded to Professor Christine Holt.
The lecture recognizes pioneering work in understanding molecular mechanisms of nerve growth, guidance, and targeting.
Sir David Ferrier, a pioneer in experimental brain physiology and the originator of modern cerebral surgery in the 1800s, is honored by the lecture's name.
His study focused on the brain regions connected to vision and hearing.

Professor Christine Holt's Lecture

Christine Holt, a Professor of Developmental Neurobiology at Cambridge, will present research on nerve connections between the eye and brain.
Her research includes the demonstration on how nerve fiber growth involves protein production at the axon tips.
Her lecture, "Wiring Up the Brain: How Axons Navigate," will discuss axon guidance or axon navigation, the process that establishes precise connections between neurons.

Neuronal Structure and Function

The brain contains billions of neurons (nerve cells) wired together in a highly complex way.
Neurons have target neurons located frequently long distances away.
Their ability to connect precisely is crucial for the animal's interactions with the surroundings and survival.
There are processes called dendrites, which are short branches on neurons and an axon, a longer process that extends from the cell body.

Axon Guidance and Growth Cone

The growth cone is a specialized structure on the axon tip that guides the axon through the brain.
The formation of these long-distance connections happens early in development.
Cajal, a Spanish neuroanatomist, described the growth cone as a structure with exquisite chemical sensitivity and rapid amoeboid (cellular) movement.
These are dynamic structures that constantly and actively explore their surroundings.
A simple analogy for growth cones is an amoeba on a leash extending out the axon.
The lecture notes give a brief overview of the process of navigating the brain.

Axon Path and Signposts

Axons navigate the brain by sensing their environment, using the concept of following signposts.
Signposts in the brain are molecular clues.
Examples of such signposts as Netrin, Efrin, Slit, and others, that growth cones have receptors that help them recognize and bind to these signposts, activating cellular signaling pathways and guiding the axon route.

The Optic Chiasm

The optic chiasm is the area of the brain where optic nerves cross or partially cross.
Visual information from the nasal half of each eye crosses over to the opposite side of the brain.
Visual information from the temporal portion of the eye stays on the same side of the brain.
The crossing over occurs at the optic chiasm.
This arrangement allows for binocular vision and depth perception for the animal.

Molecular Mechanisms (Repulsive and Attractive)

The growth cone is repelled at the optic chiasm by Efrin-related molecules.
The growth cone guidance depends heavily on receptor expression.
The growth cone also responds to attractive signals by proteins like netrin.
Different proteins drive the translation of various components that influence the cytoskeleton, and affect the shape of growth cones.

RNA Activity and Translation in Axons

Specific RNAs are transported out into the axon, where they direct the synthesis of local proteins.
This local synthesis of proteins is important for guiding the axons.
The process of protein synthesis is regulated by guidance molecules and the proteins are translated specifically where necessary.
The local translation supports the growth cone’s ability to respond to signals and adjust its direction throughout its path or even in the event of injury.
The researchers have found that multiple types of RNA are responsible, not just a single type.

Questions from the Audience

Questions about the role of mitochondria in protein synthesis and the role of genes in neural development were asked.
The role of microtubules in consciousness was also a topic of discussion.

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Description

This quiz covers the highlights of the Farrer Lecture presented by Professor Christine Holt, who discusses her pioneering research on nerve connections between the eye and brain. It also honors Sir David Ferrier, a key figure in experimental brain physiology. Delve into the molecular mechanisms of nerve growth and axon navigation.