Octopus inhabit a wide range of thermal environments from deep polar waters where temperatures are near or below 0°C, to shallow tropical estuaries with temperatures above 35°C.
In my project, I am looking for evidence of molecular-level adaptation to life in these conditions. Specifically, I am studying a voltage-gated potassium channel, Kv1, which is involved in repolarization of the action potential in cephalopod motor axons. Because the kinetics of this channel are highly temperature sensitive, we expected that different species of octopus would have evolved modifications to the primary structure of the channel that allow them to function optimally at their native temperatures.
I found that the genomically encoded Kv1 channels are highly conserved among octopus, and have almost identical electrophysiological properties. However, A-to-I RNA editing introduces additional variation, and appears to be regulated differently in the octopus species we’ve studied so far.
Currently, I am focusing on a single editing site, I321V, which produces an isoleucine to valine substitution in the pore domain of the channel. The I321V site is found in all of the eight octopus species I’ve examined, but is edited in a much higher percentage of mRNA’s for cold-water species than for temperate and tropical species. This single isoleucine to valine substitution dramatically speeds up the rate of channel closure, a phenotype which we think could be beneficial for cold adapted octopus. I’m currently working to determine the mechanism by which this substitution speeds channel closure.