Sustained upregulation in embryonic spinal neurons of a Kv3.1 potassium channel gene encoding a delayed rectifier current

Differentiation of electrical excitability entails changes in the currents that generate action potentials in spinal neurons of Xenopus embryos, resul ting in reduced calcium entry during impulses generated at later stages of development, A dramatic increase in delayed rectifier current (I-Kv) during the first day of development plays the major role in this process. Identif ication of potassium channel genes responsible for the increase in I-Kv is critical to understanding the molecular mechanisms involved. Several member s of the Shaw Kv3 gene subfamily encode delayed rectifier currents, indicat ing that they could contribute to the upregulation of I-Kv that reduces the duration of action potentials. We isolated a Xenopus (x) Kv3.1 gene whose expression is restricted to the central nervous system, which is upregulate d throughout the period during which I-Kv develops in vivo. The fraction of neurons in which transcripts of this gene are detected by single-cell RT-P CR increases to 40 % with time in culture, paralleling the development of I -Kv in neurons in vitro. Expression of xKv3.1 mRNA generates a delayed rect ifier potassium current in oocytes, suggesting that xKv3.1 contributes to t he maturation of I-Kv and shortening of the action potential. (C) 2000 John Wiley & Sons, Inc.