Postsynaptic CPG15 promotes synaptic maturation and presynaptic axon arborelaboration in vivo

The formation of CNS circuits is characterized by the coordinated developme nt of neuronal structure and synaptic function. The activity-regulated cand idate plasticity gene 15 (cpg15) encodes a glycosylphosphatidylinositol (GP I)-linked protein whose in vivo expression increases the dendritic arbor gr owth rate of Xenopus optic tectal cells. We now demonstrate that tectal cel l expression of CPG15 significantly increases the elaboration of presynapti c retinal axons by decreasing rates of branch retractions. Whole-cell recor dings from optic tectal neurons indicate that CPG15 expression promotes ret inotectal synapse maturation by recruiting functional AMPA receptors to syn apses. Expression of truncated CPG15, lacking its GPI anchor, does not prom ote axon arbor growth and blocks synaptic maturation. These results suggest that CPG15 coordinately increases the growth of pre- and postsynaptic stru ctures and the number and strength of their synaptic contacts.