Years ago, my friend Rick Bribiescas and I got into a friendly debate about the cause of muscle atrophy and bone loss during space flight. We both felt that a homeostatic mechanism was thrown out of whack by the circumstances of weightlessness. One of us suggested that zero gravity caused to lose their ability to regulate tissue mass because gravity would be part of the mechanism for measuring this variable. The other of us thought the body was reacting as though it was falling, and transforming ingested material into bodily tissue would be forestalled until some time after hitting the ground, but that never happened. I can't remember which of us thought which.
But we were probably both wrong. It may be the case that gravity is an expected contextual feature of normal cellular activity, so when there is either not much gravity (as in zero-G of space flight) or even too much gravity, cellular processes to awry more or less randomly, which would ultimately translate into gene expression being up or down regulated, more or less randomly, across the genome.
A recent study placed fertile fruit fly eggs in three different environments: High magnetism and normal gravity, simulated zero G caused by a magnetic field, and double G caused by the same magnetic field but turned upside down.
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It shouldn't be too difficult to test it in actual zero-g/extra-g. The former may be prohibitively expensive for the particular research group, but then again, NASA has just opened a new office for people to apply to get experiments flown on the ISS. Part of me is concerned that the magnetism-induced simulated microgravity will not adequately replicate the true freefall environment of spaceflight. After all, the magnet only acted up on the water molecules inside of the flies. While the files are, like all living things, primarily water, they are not entirely water and I have to wonder whether this could have affected the results. They have dealt with half of that problem, by including groups exposed to similar magnetic fields which do not cause levitation, but I'd like to see it replicated in actual space. If nothing else, it'd be awesome. ;-)
The extra-g situation could be tested with a centrifuge. Not sure if they'd be better off renting one of the ones built for people or building their own, smaller-scale device for the critters.
So wait. They invented anti-gravity to test fruit fly development, and the news-worthy item is the fruit-flies??
Reminds me of this: http://www.gunnerkrigg.com/archive_page.php?comicID=71
(Yes of course I know they didn't really invent zero gravity.)