The ability of our nervous system to function properly relies on elaborate and precise connections between nerve cells and their targets. In a new study, researchers at The Neuro - The Montreal Neurological Institute and Hospital, McGill University identify a receptor capable of directing and controlling a set of nerve cell projections to their specific target. This information is crucial for understanding how nerve cells are guided to their appropriate targets in the extremely complex environment of the brain and in turn for treating nervous systems damaged through spinal cord injury or neurodegenerative diseases such as Alzheimer's and Parkinson's.
The study published in The Journal of Neuroscience identifies the receptor Robo-2 as having a key role in ensuring that sensory nerve cell projections or axons reach their specific target locations in the accessory olfactory bulb, a part of the mouse olfactory system involved in the regulation of sexual behavior and social dominance.
Nerve cells are highly specialized and connect to very specific locations within an organ, muscle or tissue. These precisely targeted connections are determined by guidance cues that either attract or repel nerve cell axons towards their target during development. These cues act by binding to receptors on the nerve cell surface, which cause a signal inside the cell to direct axon growth either towards or away from the source. Making the correct connections in the mouse olfactory system is crucial as these signal the correct behavior in response to compounds in the environment.
"The overall context of our study is to understand how nerve cell axons find their appropriate synaptic partners in a complex target field with the hope that we will be able to control the growth and targeting of axons, in order to establish regenerative therapies for various diseases such as Parkinson's, or Alzheimer's and to treat spinal cord injury. Under the proper conditions, axons have an infinite capacity to regenerate," says Dr. Jean-Francois Cloutier, neuroscientist at The Neuro and principal investigator in the study.
"We have identified a cell surface receptor, Robo-2, as capable of controlling the targeting of a subset of neuron axons to a specific region of the accessory olfactory bulb in the mouse. In the absence of this receptor, the axons inappropriately innervate or connect with, other regions of the target field. Understanding how this receptor controls the targeting of these axons will allow us in the future to develop strategies to control the formation of synapses by regenerating axons following cell replacement therapies."
This work was supported by the Canadian Institutes for Health Research, the Fonds Quebecois pour la Recherche sur la Nature et les Technologies, the Montreal Neurological Institute Centre of Excellence in Commercialization and Research, and a grant from the Wellcome Trust.