Gap Junction Between Excitatory Neurons In Neocortex Plays Role In Cortical Development

In the developing cerebral cortex, sister excitatory neurons produced by the same radial glial cell in the VZ (ventricular zone, VZ) and SVZ (subventricular zone, SVZ) migrate along the radial glial fiber to the cortical plate, resulting in the formation of ontogenetic column. Our recent work has shown that sister excitatory neurons preferentially form transient electrical synapse with each other at first postnatal week. These electrical synapses regulate the subsequent formation of preferential chemical synapse and contribute to functional similarity between sister excitatory neurons. However, little is known about the role of these electrical synapse in the development of excitatory neuron, network. By taking advantage of CreER-Loxp system, we hypodermically injected tamoxifen to pups at postnatal day 1 (P1) to induce conditional knockout of connexin26 (Cx26) in excitatory neurons at early postnatal stage. Combined with immunohistochemistry, single-cell reverse transcription PCR, western blot, whole-cell patch clamp recordings, large-scale calcium image, Golgi staining, we found knockout of Cx26 between excitatory neurons in early postnatal neocortex leads to simpler dendrite structure, reduced dendritic spine density, lower mEPSC (miniature excitatory postsynaptic current, mEPSC), mPSC (miniature inhibitory postsynaptic current, mIPSC) frequency. Our results indicate transient electrical synapses in early postnatal neocortex have important role in neural maturation and synaptic function.