A receptor on the axon called DCC, or Deleted in Colon Cancer, responds to the signal from netrin. But why the axon knows to move in a certain direction once it sees that signal was an unknown, Dr. Xiong says. The researchers have now found that once this receptor binds to netrin, focal adhesion kinase is activated that tells the axon to reorganize its structure or cytoskeleton and the restructured axon knows how to move. When they delete the kinase, the axon doesn't make the proper journey or the proper connection.
Developing axons can sense and navigate their environment but how the two functions work together to result in the axon getting where it needs to be is poorly understood, Dr. Xiong says. "Everybody in the developmental neurobiology field is wondering what is the mechanism, how the neuron, once it senses the environment, couples with the motor activity. This provides information for that kind of puzzle," she says of the newly published work.
The researchers are looking for other molecules that also play a role in directing axonal growth. "We have lots of information about how this molecule talks with other molecules," Dr. Xiong says. "We just need to get a system to figure out how they talk to each other."
She's also moving toward an injury model to see what happens to this molecular talk after a spinal cord injury. "We know this factor can turn on but we don't know how it turns on. If you sever the spinal cord, the important crossing of the axon is gone. Right now, we don't know how to make it go back."
Drs. Xiong's MCG collaborators on the study include her husband, Dr. Lin Mei, also a developmental neurobiologist; research technician Zhu Feng and graduate student Qiang Wang as well as researchers at the
Contact: Toni Baker
Medical College of Georgia