Collaborative Research: Analysis of a Rapidly Evolving Potassium Channel in an Electric Fish

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Ion channels, specialized proteins that reside in the cell membrane, shape the electrical activity of nervous systems in all forms of life. Naturally occurring variation (mutations) in genes that encode ion channel proteins can determine electrical properties throughout the nervous system. To better understand the relationship between sequence, structure and function of ion channels, the investigators will use mutations discovered in a potassium channel gene found only among the weakly electric fishes of Africa. They hypothesize that these mutations confer extraordinarily rapid molecular movements, and thus rapid electrical activity, enabling these fishes to produce rapid pulses of electricity used in communication and navigation. The first aim of this grant will be to sequence this gene from a variety of African electric fishes to determine the evolutionary origin of this mutation. The second aim will be to express these genes in-vitro to investigate the physical properties that the mutation confers. This work is important because it gives us greater insight into the role that genetic changes play in determining electrical properties of all types of cells, including heritable diseases of the nervous system (channelopathies), as well as adaptive differences that may shape the nervous system in the evolution of new behaviors. As part of their work, the investigators will train undergraduates, including those from underrepresented groups in science, through coursework and laboratory experiences in molecular evolution, physiology and genomics.Investigators will investigate the relationship between sequence evolution and biophysical properties of a potassium channel (Kv) exclusively expressed in the electric organ, a derivative of muscle, in African electric fish. Most electric organ discharges (EODs), are used for communication and navigation, and are extraordinarily brief (500 microseconds) within this group, however a few species have secondarily evolved long duration discharges. One Kv channel (kcna7a) is abundantly expressed in the electric organ, and preliminary data suggests high rates of sequence evolution and amino acid substitutions in otherwise highly conserved regions of this protein, likely conferring unique biophysical properties. In the first aim investigators will perform RNAseq on electric organ and muscle tissues from 10 species of African electric fish strategically chosen for their phylogenetic relationships and waveform duration, and examine kcna7a sequence evolution as it relates to EOD phenotypic evolution. In the second aim, investigators will perform site-directed mutagenesis on kcna7a channel genes, guided by discoveries in aim 1, express mutagenized channels in frog oocytes, and perform physiological recordings to determine biophysical properties conferred by specific amino acids. This work will give insights into the genetic basis of rapid evolution of a communication signal involved in speciation; investigate novel amino acid substitutions in a class of medically-relevant ion channels that are universally important in shaping neural activity; potentially provide resources for making channels with hyper-fast kinetics for shaping electrical activity in tissue engineering and provide transcriptomic resources for laboratories studying other aspects of electric organ development and evolution.