A single brain cell or neuron can send signals to hundreds of others using its axon — a thin fiber that acts like a telephone cable carrying electrical messages and splitting into numerous tree-like branches. Different cellular materials need to be transported along the axon and its elaborate branches to support the development and function of brain cells, but how they do it has been a puzzle.
Neuroscientist Le Ma, PhD, and colleagues developed a simple method to tackle the question. They cultured neurons in a dish and studied transport at the junction of two branches by tagging a cellular cargo called lysosomes, small sacs that travel along branches to remove waste and recycle nutrients. They found that if the two branches were the same length, the lysosomes traveled equally to both. However, if one branch was longer than the other, more lysosomes travelled to the longer one, suggesting that branch length influenced transport.
They also looked at the growth cone — the branch tip that acts like a sensor, looking for things to grow toward or to avoid. They found that lysosomes preferred traveling to branches with more dynamic growth cones over the still ones. Interestingly, when they used a molecular tool to make a still branch more dynamic, the lysosomes swarmed to it.
“These experiments showed us how trafficking is regulated in brain cells and could give insight into how neuronal transport impacts conditions like nerve injury and memory loss,” says Dr. Ma.
