Meeting Abstract
Weakly electric fishes use electric signals produced in the muscle-derived electric organs for social communication and to sense their environment. Some species generate brief electric pulses lasting only a few hundred microseconds. Generation of these brief electric pulses is enabled by a potassium channel (Kcna7a) which is expressed only in the electric organ. Kcna7a evolved by duplication of an ancestral gene (Kcna7) that is widely expressed in muscle; expression of the other duplicate gene, Kcna7b, remains in the muscle. The electric organ Kcna7a channel has evolved rapidly to open quickly and at much more negative potentials than the Kcna7b channel, thereby allowing brief electric discharges. The sequences also reveal amino acid substitutions in the tetramerization domain of Kcna7a channel, but which came first: localization of protein expression or an inability to tetramerize? Could loss of tetramerization between these channel subunits have enabled the rapid sequence evolution of Kcna7a? To investigate this, we expressed variable ratios of Kcna7a and Kcna7b in heterologous cells by injecting mixes of mRNA and measuring the electrophysiological properties of these channels. We found that, despite sequence variability, these channels likely are able to tetramerize. This suggests that their rapid evolution was probably enabled by expression localization or that ability to tetramerize may not constrain evolution of gene duplicates.
