Meeting Abstract

120.2  Tuesday, Jan. 7 10:45  Two roads diverged 100 million years after a duplication. THOMPSON, A.M.*; ZAKON, H.H.; Univ. Texas, Austin ammonthompson@gmail.com

Gene duplication is an important source of new genetic information. How gene families expand and diversify is especially important in the research of the genetics of adaptation. One particularly interesting example of gene duplication is the expansion of the voltage-gated ion channel gene family during the evolution of the nervous system in animals. This gene family has expanded from many duplication events to provide numerous channels selective to different ions, contributing to a wide variety of electrical functions in excitable tissue along with the elaboration of unique and adaptive cell types. One novel excitable cell type is the electrocyte, which has evolved in two different teleost fish lineages. It is derived from muscle cells and specializes in generating electrical impulses used for communication with conspecifics as well as for sensing and navigating their nocturnal world. Interestingly, in both electric lineages the same duplicate sodium channel was co-opted from its muscle function to specialize as an electrocyte-specific sodium channel, leaving the other duplicate behind in the muscle. Why was the same paralog co-opted for this novel organ? Through measuring relative gene expression of the two paralogs in muscle and ancestral character state reconstruction we have determined that the paralog that was turned off was greatly down-regulated in the non-electric ancestor of both these electric fish, suggesting it was “easier” to turn off in muscle and specialize for a novel function in electrocytes. The evolution of a duplicate sodium channel during the convergent evolution of a novel excitable tissue is another fascinating chapter in the expansion of the ion channel gene family as animal nervous systems grow and diversify in complexity and function.