We have identified for the first time a mutation in the skeletal muscle-specific regulatory γ3 subunit of AMPK in humans. The γ3R225W mutation has significant functional effects as demonstrated by increases in basal and AMP-activated AMPK activities, increased muscle glycogen and decreased IMTG. Overall, these findings are consistent with an important regulatory role for AMPK γ3 in human muscle energy metabolism.
Costford SR, Kavaslar N, Ahituv N, Chaudhry SN, Schackwitz WS, et al. (2007) Gain-of-Function R225W Mutation in Human AMPKγ3 Causing Increased Glycogen and Decreased Triglyceride in Skeletal Muscle. PLoS ONE 2(9): e903. doi:10.1371/journal.pone.0000903. You can discuss at PLOS One of course. I'm interested in this as it relates to the earlier paper which shows that some populations have a loss of function mutation which alters muscle metabolism. This variant on the other hand is a gain of function, which tend to be rarer and obviously of more biochemical interest because of its novelty. Note that this locus seems much more polymorphic in the Yoruba in the HapMap data set, and there is already known variation in regards to Type II diabetes susceptibility between populations. There's some stuff to look at if you follow some of p-ters guidelines on how to sniff population substructure and poke into evolutionary dynamics, though I'll leave it to you as an exercise if you are curious (HapMap queries can't be linked, they seem to be submitted via POST).