Rab3A is required for brain-derived neurotrophic factor-induced synaptic plasticity: Transcriptional analysis at the population and single-cell levels

Brain-derived neurotrophic factor (BDNF) modulates synaptic strength in hip pocampal neurons, in addition to promoting survival and differentiation. To identify genes involved in trophic regulation of synaptic plasticity, we h ave used a multidisciplinary approach of differential display and family-sp ecific slot blots in combination with whole-cell patch-clamp recordings of dissociated hippocampal neurons. Three hour exposure to BDNF elicited a 2.6 -fold increase in synaptic charge and a concomitant induction of 11 genes a s revealed by differential display, including the small GTP-binding vesicul ar trafficking protein Rab3A and the enzyme guanylate cyclase (GC). Slot bl ot analysis on a population of neurons confirmed an average of 3.1-fold ind uction of these clones. In contrast, individual pyramidal-like neurons that were first characterized electrophysiologically in the presence of BDNF an d subjected to transcriptional analysis displayed more robust increases (4. 8-fold), emphasizing the neuronal heterogeneity. Transcriptional changes of Rab3A and GC were accompanied by translational regulation, shown by Wester n blot analysis. Furthermore, a number of GC-associated and Rab3A effector molecules were induced by BDNF at either the gene or protein levels. The fu nctional role of Rab3A in BDNF-induced synaptic plasticity was assessed usi ng cells derived from Rab3A knock-out mice. These neurons failed to show an increase in synaptic charge in response to BDNF at 10 min; however a late response to BDNF was detected at 20 min. This late response was similar in time course to that induced by postsynaptic activation of glutamate recepto rs. Our results demonstrate a requirement for Rab3A and may reveal a tempor al distinction between presynaptic and postsynaptic mechanisms of BDNF-indu ced synaptic plasticity associated with learning and memory.