OVEREXPRESSION OF A POTASSIUM CHANNEL GENE PERTURBS NEURAL DIFFERENTIATION

Functional regulation of potassium currents in developing neurons is p ivotal for changes in excitability and action potential waveform. Here , we test whether an excess of potassium channel transcripts is suffic ient to drive functional expression of potassium current and shortenin g of the duration of the action potential. Injection of Shaker-like po tassium channel transcripts into two-cell stage embryos achieves incre ases in RNA levels. The elevated levels of. potassium channel RNA prod uce larger delayed-rectifier currents. Action potential durations are briefer, indicating that larger potassium currents are not compensated by changes in inward currents. Strikingly, overexpression of potassiu m current RNA leads to a reduction in the number of morphologically di fferentiated neurons in culture. We suggest that, by prematurely reduc ing the duration of the impulse, early overexpression of potassium cha nnel activity suppresses normal developmental cues.