Xenopus Spinal Neurons Express Kv2 Potassium Channel. Transcripts during .... by adult Xenopus breeding pairs or in vitro fertilization. (Moon and Christian,.
The Journal
of Neuroscience,
Xenopus Spinal Neurons Express Kv2 Potassium Transcripts during Embryonic Development Corinna
Burger’
and Angeles
February
15, 1996, 76(4):1412-l
421
Channel
B. RiberalJ
l Programs in Neuroscience and Cell and Developmental Health Sciences Center, Denver, Colorado 80262
Biology,
and 2Department
of Physiology,
University
of Colorado
Developmentally regulated delayed rectifier potassium currents determine the waveform of the action potential in all Xenopus embryonic primary spinal neurons. To examine this developmental program at the molecular level, we have isolated Xenopus Kv2 potassium channel genes Kv2.1 and Kv2.2. Both genes induce functional heterologous expression of delayed 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 ventral spinal neurons, whereas previously described Kvl .l transcripts are found in dorsal spinal neurons. Thus, spinal neuron subtypes express distinct potassium channel genes, yet they temporally coordinate functional expression of delayed rectifier potassium currents. Key words: potassium channels; gene expression; Xenopus embryo; electrical excitability; neuronal differentiation; spinal neurons
In the developing Xenopus nervous system, ion channel gene expression is amenable to both molecular and functional analyses. Previous biophysical studies of Xenopus embryonic spinal neurons have demonstrated that developmental regulation of the delayed rectifier potassium current (ZK-) causes modulation of the action potential duration. Z,, is initially a small, slowly activating current that matures to a larger, more rapidly activating one (O’Dowd et al., 1988) (for review, see Ribera and Spitzer, 1992). Although much is known about differentiation of I,, at the functional level, the molecular mechanisms that synchronize development of I, in motor, inter-, and sensory spinal neurons are unknown. Two lines of evidence are consistent with the notion that regulation of functional expression of I,
