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Published on: March 17, 2011
The role of a LAR-like receptor tyrosine phosphatase in growth cone collapse and mutual-avoidance by sibling
1Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
Abstract:
Among the many cells or parts of cells that a growth cone may encounter during its embryonic migrations are other processes or parts of its parent cell. Such an event can be expected to be relatively frequent in the genesis of neuronal arbors, for instance, where the density of innervation of a target region can be quite high. Few experimental studies have addressed the very interesting question of whether a process "recognizes" siblings in some unique way, in a manner that can be distinguished from, say, how it interacts with unrelated cells. One example can be found in the leech, where sibling branches in the terminal fields of identified mechanosensory cells avoid each other strictly while permitting some significant continuing contact and overlap with homologues, a phenomenon that has been dubbed "self-avoidance." Another example has been reported in cultured Helisoma neurons, where severing a branch of a neuron allows sibling neurites to form electrical junctions with it, although normally sibling neurites do not do so. In both of these instances, coincidental activity was proposed as one means to achieve recognition of self and as possibly leading to the blocking of a continuing interaction among the parts, although alternative explanations were indeed considered possible.
Insights
Neuronal growth cones exhibit "self-avoidance," a phenomenon where sibling branches avoid each other during embryonic development. This unique recognition mechanism guides neuronal arbor formation and target innervation.
Area of Science:
- Neuroscience
- Developmental Biology
Background:
- Growth cones navigate complex environments during embryonic development.
- High innervation density in target regions increases encounters between neuronal processes.
- Limited research exists on whether neuronal processes distinguish between sibling and non-sibling cells.
Purpose of the Study:
- To investigate the phenomenon of neuronal self-avoidance.
- To explore whether neuronal processes recognize and interact differently with sibling versus non-sibling cells.
- To understand the mechanisms underlying sibling neurite recognition.
Main Methods:
- Observation of identified mechanosensory cells in leeches.
- Analysis of neurite interactions in cultured Helisoma neurons.
- Experimental manipulation, including severing neuronal branches.
Main Results:
- Leech mechanosensory cells display strict self-avoidance between sibling branches.
- Cultured Helisoma sibling neurites form electrical junctions upon branch severing, unlike normal interactions.
- Coincidental neural activity is a proposed mechanism for self-recognition and interaction blocking.
Conclusions:
- Neuronal processes can distinguish and avoid self (siblings) during development.
- Self-avoidance is a crucial mechanism for proper neuronal arbor formation.
- Further research is needed to fully elucidate the molecular and activity-dependent mechanisms of self-recognition.
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