A pair of enzymes control where synapses form in neurons by guiding the transport of energy-producing organelles called mitochondria.

Credit: JULIEN COURCHET

A team led by Franck Polleux at the Scripps Research Institute in La Jolla, California, identified two enzymes that are required for axons (the long message-transmitting stalks of neurons) to branch and form synapses with other neurons. When these enzymes were overexpressed in neurons, mitochondria moving down the axon, along microtubules, were immobilized at the point where axons would form synapses. Higher levels of these enzymes boosted axon branching (pictured), whereas lower levels reduced it.

The researchers suggest that the two enzymes work together to tell mitochondria where to stop and thus where synapses will form. Mitochondrial transport could factor in the development of a wide range of disorders, including autism, through its effects on synapse formation, the authors say.

Cell http://dx.doi.org/10.1016/j.cell.2013.05.021 (2013)