Mechanisms for synaptogenesis

Question 1

When does synaptogenesis occur?

Answer 1

Synaptogenesis starts in the embryo after neuronal development, and continues though out adolescence, and even in adulthood (learning).

Question 2

At what age is the synaptic density the highest in humans?

Answer 2

Around 2 years

Question 3

What are the main components of a synapse in the CNS?

Answer 3

Cell adhesion proteins.
Active zone and vesicle release machinery.
Post synaptic density.
Receptors.
Scaffolding proteins.

Question 4

What are the four steps of synapse formation?

Answer 4

1) Axon guidance
2) Priming of synapse formation
3) Adhesion and induction of differentiation
4) Formation of active zone and postsynaptic density

Question 5

What are priming factors? When are they relevant?

Answer 5

Priming factors are secreted proteins, that prepare axons and dendrites for contact. They are relevant for priming of synapse formation

Question 6

What signalling pathway is involved in the initial patterning of the neural tube, and later neuron specification?

Answer 6

The wnt pathway

Question 7

What are the three different pathways Wnt signalling can activate?

Answer 7

1) The canonical pathway
2) The planar cell polarity pathway
3) The calcium pathway

Question 8

Via what pathway does Wnt affect presynaptic clustering?

Answer 8

The canonical pathway

Question 9

Via what pathway does Wnt affect postsynaptic activation?

Answer 9

The calcium pathway

Question 10

What cellular processes does Wnt signaling induce in the presynaptic region?

Answer 10

Increased growth of cone size and complexity, and increased brancing

Question 11

What cellular processes does Wnt signaling induce in the postsynaptic region?

Answer 11

Clustering of receptors by scaffolding proteins.
(Scaffolding proteins in the membrane facilitate that receptors go there)

Question 12

How does BDNF release affect a synapse?

Answer 12

It helps to stabilize it

Question 13

What type of protein is found in many variations, causing the high number of specific synapses

Answer 13

Adhesion and induction factors

Question 14

What are the four most important adhesion factors in the synapse?

Answer 14

1) Neuroligins & neurexins
2) Ephrins & Eph receptors
3) Caherins & protocadherins
4) Syn-CAMs

Question 15

How is it possible for cells to create a high number of very specific adhesion molecules?

Answer 15

Alternative splicing

Question 16

What is the active zone? What is transported here?

Answer 16

The active zone is the membrane on the pre-synaptic terminal. Axonal transport packets with many different proteins are transported here

Question 17

Where are dendritic and axonal transport packets transported to?

Answer 17

Axonal packets are transported to the pre-synaptic terminal.
Dendritic packets are transported to the post-synaptic terminal.

Question 18

How is specificity of contact between pre- and postsynaptic partners ensured?

Answer 18

Adhesion molecules and synapse organizing molecules interacting across the synaptic cleft