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Extensive Structural Remodeling of the Axonal Arbors of Parvalbumin Basket Cells during Development in Mouse
Kristina D Micheva1, Marianna Kiraly2, Marc M Perez2
1Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305 kmicheva@stanford.edu madison@stanford.edu.
Summary
Parvalbumin-containing (PV+) basket cells rapidly myelinate their axons and prune synapses during early development. These refinements establish the precise neural connections crucial for reliable brain function in adult mice.
Area of Science:
- Neuroscience
- Developmental Biology
- Cellular Neuroscience
Background:
- Parvalbumin-containing (PV+) basket cells are key interneurons regulating neuronal circuits with high temporal precision.
- Understanding the developmental establishment of PV+ interneuron connectivity is crucial for comprehending their functional roles.
Purpose of the Study:
- To map the development of synaptic connectivity and myelination in PV+ interneurons.
- To investigate how axon-myelin units and synapse numbers change during postnatal development.
Main Methods:
- Utilized array tomography to map synaptically connected PV+ interneurons and postsynaptic neurons in the mouse neocortex.
- Quantified synapse numbers, axonal path lengths, and myelination at various developmental time points (2 weeks to 7 months).
Main Results:
- Rapid myelination of proximal axons occurred within the third and fourth postnatal weeks.
- Synaptic contacts per connection were significantly reduced by approximately two-thirds by the end of the first postnatal month.
- Axonal reorganization and target refinement continued beyond two months, with increased uniformity in myelination and path length.
Conclusions:
- Early and rapid development of PV+ interneuron axons, including myelination and synapse pruning, is critical for mature circuit function.
- Ongoing axonal refinement contributes to the precise and reliable inhibitory signaling characteristic of adult PV+ basket cells.
