Cours : Synapse formation (II) and Synapse plasticity

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Questions and Answers

What does the acronym NMJ stand for?

Neuro Muscular Junction (correct)

Neural Muscle Junction

Neural Motor Junction

Neurological Motor Junction

The document mentions that synapses and neural systems...

are formed only in specific locations.

have evolved more than once. (correct)

are part of the digestive system.

are independent from synaptic genes.

What is the most likely research topic of the document?

The function of the human brain

The development of the digestive system

The origins of synaptic function (correct)

How to evolve artificial intelligence

Which of the following species is NOT mentioned in the figure?

Batrachospermum repens (D) Signup and view all the answers

Based on the figure's organization, which species is likely most closely related to Batrachospermum virgatum?

Batrachospermum helminthosum (D) Signup and view all the answers

What does the figure imply about synapse development in most species?

Most species do not require synapses for development. (A) Signup and view all the answers

Which of the following species is most likely to have a more complex nervous system based on its position in the figure?

Pterocladiella melanoidea (C) Signup and view all the answers

What does the organization of the figure suggest about the relationships between organisms?

Species closer together are more likely to be closely related. (D) Signup and view all the answers

What does the figure imply about the evolution of synapses?

Synapses evolved independently in different lineages. (C) Signup and view all the answers

Which of the following statements accurately reflects the information presented in the figure?

Only a few organisms listed in the figure have a complex nervous system. (B) Signup and view all the answers

What is the most likely reason that the figure focuses on the development of synapses?

Synapse development is a key characteristic for complex lifeforms. (B) Signup and view all the answers

Which of the following species would you expect to have a more complex nervous system: Batrachospermum helminthosum or Cephalocystis furcellata?

Cephalocystis furcellata (A) Signup and view all the answers

Which of the following statements is most consistent with the information presented in the figure?

Synapse development is likely a more recent evolutionary development. (A) Signup and view all the answers

What is the most likely implication for organisms that do not develop synapses?

They are less likely to have a complex nervous system. (D) Signup and view all the answers

Which of the following statements best summarizes the main point of the figure?

Synapses are a comparatively recent and specialized feature of life. (B) Signup and view all the answers

Based on its placement in the figure, which of the following species would you anticipate having a more complex nervous system: Meiodiscus spetsbergensis or Erythrocolon podagricum?

Meiodiscus spetsbergensis (C) Signup and view all the answers

What does the figure imply about the relationship between complexity of nervous systems and the presence of synapses?

Complex nervous systems are more likely to require synapses for development. (C) Signup and view all the answers

Which of the following species is most likely to have a simple nervous system based on its placement in the figure?

Sarcodiotheca g... (D) Signup and view all the answers

Study Notes

Synapse Formation and Plasticity

Synapses are fundamental for communication between neurons
Synapse formation is a complex process involving several stages
Synapse development involves both pre and postsynaptic components
Synaptic evolution likely occurred more than once in different lineages.
Many organisms do not even need synapses.
Synaptic strength is determined by multiple factors, including neurotransmitter release probability.

Synaptic Modules

Synapses are composed of three main components: vesicle fusion, active zone, and postsynaptic density.
Vesicle fusion can occur in the absence of cytoplasmic scaffolds or Ca2+.
Functional presynapses can form without a postsynaptic partner

Active Zone Assembly

Presynaptic lysosome-related vesicles (PLVs) contain active zone proteins and synaptic vesicle proteins.
Partial axonal co-transport in PLVs transport these components in Drosophila and human neurons.

Genes Involved in Active Zone Assembly

Genes such as dsyd-1 (Drosophila) and msyd-IA (mouse) are crucial for synaptic vesicle targeting in both the peripheral nervous system (PNS) and central nervous system (CNS).

Evolutionary Conservation

Molecular mechanisms underlying synapse development are conserved between flies and mice (~700 million years apart)

Today's Synaptic Assemblies

Todays synapse assemblies include postsynaptic assembly, postsynaptic & transsynaptic molecules, maturation, and plasticity.

Postsynaptic Density

Neurexin expression in non-neuronal cells influences glutamate and GABA postsynaptic protein clustering in dendrites.
Neuroligin isoforms determine the polarity of synapses(inhibitory or excitatory).

Postsynaptic Density Assembly

Neuroligin expression in non-neuronal cells may induce the accumulation of postsynaptic scaffolding proteins in dendrites.
Neurexins mediate excitatory postsynaptic formation and Neuroligins mediate inhibitory postsynaptic formation

Synaptic CAMs

Specific cell adhesion molecules (CAMs) are expressed in non-neuronal cells, that induce pre/postsynaptic features when in co-culture with neurons.
Specific CAMs, e.g. Neuroligins, regulate the formation of presynaptic and postsynaptic compartments.

PSD Assembly

'Non-synaptic' postsynaptic protein clusters and 'Synaptic' postsynaptic proteins differ in their behavior in formation.
Some postsynaptic scaffolding proteins transport in a coordinated or non-coordinated manner that dictates whether a synapse will form.
Some postsynaptic proteins (like PSD-95) accumulate at active synapses after a period of neuronal activity after uncaging glutamate.

Activity-Dependent Processes

Synaptic activity can trigger glutamate uncaging which results in the grow of a post synaptic structures such as spines.
Neuroligin 1 facilitates glutamate uncaging-induced spinogenesis.
The presynaptic protein Munc13 may represent presynaptic release sites.
Normal spine development and glutamate uncaging occur in Munc-1/3 double knock-out mice.

PALM of PSD-95

Photoactivated localization microscopy (PALM) can be used to quantify the number of PSD-95 molecules.

Pre/Post Alignment

PALM shows alignment of presynaptic and postsynaptic proteins into “nanocolumns”.

Timing of Synaptogenesis

Cell adhesion molecules (CAMs) orchestrate the timing between pre and post synapic assembly, in general, presynaptic assembly comes before the postsynaptic assembly, in certain cases this may not hold true.

Synapse Maturation

Synapse maturation involves the refinement of synaptic topography, convergence, and postsynaptic compartment.
Numerous synapses are typically pruned during the maturation process of development. The elimination of synapses follows a pattern, involving both segregation and specific activity-levels of the neurons involved.
In vivo mouse NMJs (neuromuscular junctions) serve as a model for investigating synaptic maturation.
Synapse elimination is accompanied by input segregation and eventually terminal withdrawal.
Patterns of motor neuron activity influence synapse elimination during neural development.
The “winner synapse” undergoes LTP, resulting in its strengthening and leading to the elimination of the remaining synapses.

Synaptic Plasticity and Competition

Synchronous activation of climbing fibers and Purkinje cells (PCs) can lead to long-term potentiation (LTP).
LTP at large inputs results in enhanced AMPA-type glutamate receptor conductance.

How to Build a Synapse

Synaptogenesis occurs through transitive signaling primarily mediated by cellular adhesion proteins.
Synaptic activity plays a role in both the activation and deactivation of synapse processes.

Summary of Findings

The formation of synapses is a complex process regulated by various factors including molecular mechanisms, and neural activity.
Synaptic plasticity and competition play critical roles in synapse formation, maturation, and structure.

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Description

Test your knowledge on molecular life sciences with this quiz that covers key concepts related to synapses, neural systems, and evolutionary relationships among species. The questions delve into research topics, species comparison, and the implications of synapse development as depicted in figures. Challenge yourself to understand the connections within this fascinating field!