Developmental Molecular Neuroscience
From Neural Induction to Circuit Assembly
Developmental Principles
Neural development is controlled by gradients of morphogens, guidance cues, adhesion molecules, and activity-dependent signaling. These mechanisms specify neuronal fate, position, connectivity, and maturation.
Key Molecular Families
Patterning Idea
Early developmental gradients assign broad identity, while later cell-cell interactions refine connectivity and synaptic specificity.
What is the main function of morphogen gradients?
Morphogens provide positional information that influences developmental fate decisions.
Correct answer: To specify cell fate based on concentration
What process guides growing axons toward their targets?
Axon guidance uses attractive and repulsive cues to direct neurite growth.
Correct answer: Axon guidance
Synaptogenesis and Pruning
After neurons are generated and positioned, they form synapses and later prune inappropriate connections. Activity-dependent competition helps refine circuits, while molecular signals stabilize useful contacts and eliminate less active ones.
Developmental Stages
Specification
- Cell fate decisions
- Driven by transcription factors and morphogens
Connectivity
- Axon targeting and synapse formation
- Driven by guidance cues and adhesion
Assembly of a Neural Circuit
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1
Step 1: Neural progenitors are specified.
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2
Step 2: Neurons migrate to appropriate locations.
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3
Step 3: Axons and dendrites navigate using guidance cues.
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4
Step 4: Synapses form with selected partners.
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5
Step 5: Activity refines and stabilizes the circuit.
Which molecular process is most important for refining synaptic circuits after initial formation?
Circuit refinement relies on pruning and stabilization of selected synapses.
Correct answer: Pruning and activity-dependent stabilization
Name one class of molecules involved in axon guidance.
Netrins are one example; others include semaphorins, ephrins, and slits.
Correct answer: Netrins