XENOPUS SPINAL NEURONS EXPRESS KV2 POTASSIUM CHANNEL TRANSCRIPTS DURING EMBRYONIC-DEVELOPMENT

Developmentally regulated delayed rectifier potassium currents determi ne the waveform of the action potential in all Xenopus embryonic prima ry spinal neurons. To examine this developmental program at the molecu lar level, we have isolated Xenopus Kv2 potassium channel genes Kv2.1 and Kv2.2. Both genes induce functional heterologous expression of del ayed rectifier potassium currents. Transcripts from both Kv2 genes are present in developing embryos; however, only Kv2.2 mRNA is detectable in embryonic spinal neurons. Notably, Kv2.2 transcripts localize to v entral spinal neurons, whereas previously described Kv1.1 transcripts are found in dorsal spinal neurons. Thus, spinal neuron subtypes expre ss distinct potassium channel genes, yet they temporally coordinate fu nctional expression of delayed rectifier potassium currents.