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Pyramidal neuron polarity axis is defined at the bipolar stage
Froylan Calderon de Anda1, Annette Gärtner, Li-Huei Tsai
1Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Building 46, Room 4235A, Cambridge, MA 02139, USA.
Journal of Cell Science
|January 12, 2008
Summary
Neuronal polarity, crucial for brain development, is established early when the first two neurites form. This intrinsic program dictates axon-dendrite identity, guiding neuronal growth.
Area of Science:
- Neuroscience
- Cell Biology
- Developmental Biology
Background:
- Neuronal development involves establishing distinct axon-dendrite identities.
- Previous studies presented conflicting models for axonal fate determination, in vivo versus in vitro.
- Understanding the precise timing and mechanisms of neuronal polarity is critical.
Purpose of the Study:
- To investigate the initial definition of neuronal polarity during neurite outgrowth.
- To reconcile in vivo and in vitro findings on axon-dendrite specification.
- To elucidate the temporal and spatial hierarchy of polarized growth.
Main Methods:
- In situ observation of developing hippocampal and cortical neurons.
- Analysis of neurite fate from emergence from the cell body.
- Experimental manipulation (cutting) of neurites to assess regrowth potential.
Main Results:
- Neuronal polarity is defined at the bipolar stage, with one of the first two neurites becoming the axon.
- This initial fate determination is independent of the number of subsequent neurites formed.
- The first two neurites exhibit the highest growth potential, with regeneration occurring at the opposite pole after cutting.
Conclusions:
- Polarized growth is initiated by an intrinsic program, temporally and spatially defined.
- Microtubule dynamics and membrane transport precede and support this intrinsic polarity.
- Axon specification molecules likely act on early neurites, with extrinsic cues refining final polarity.
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