Replication complexes in neuronal morphology

A replication initiation complex finds things to do in neurons that no longer replicate, as shown by Huang et al. (page 527). The origin recognition complex (ORC), the authors show, allows dendrites to expand their territory and make new synaptic connections.

Adult neurons are postmitotic; they thus have little or no need for DNA replication. Yet the authors noticed that ORC subunits were expressed in the mouse brain. Further, the proteins were found in dendrites rather than in the nucleus, where their typical function is performed. Knock-down studies revealed that neurons require ORC for dendritic branching and spine formation, which are the morphological mechanisms of synaptic plasticity in adult neurons.

ORC-lacking dendrites were unable to send out filopodia, which initiate both branches and spines. The actin-bundling proteins Mena and VASP, which are necessary for...