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Ant Behavior Significantly Altered By Injecting a Single Enzyme (arstechnica.com)
New submitter Fiona_OHanlon writes: According to an article at Ars Technica, researchers injected enzymes into ant larvae brains, causing genetically identical ants from different castes to behave as if they were from the opposite caste. From the story: "Carpenter ants live in a caste system, where some members of the colony grow into large, strong worker guards known as majors and others grow into small, inquisitive food scouts known as minors. [The researchers] focused specifically on enzymes that affect 160 genes whose activity diverged the most between minors and majors. Those genes included ones associated with learning, memory, and the way neurons communicate with each other in the brain. ... After several experiments with feeding the substance to their insect subjects, the researchers figured out how to inject the enzymes into the brains of major workers shortly after hatching (abstract). The treatment made the ants take on new social roles immediately. ... The modification ultimately depended on changing the behavior of one particular gene, Rpd3, which set off a cascade effect that changed the behavior of other genes too."
The major trick, in humans, is that (so far as we know) there aren't a bunch of conveniently defined castes to work with. With these ants there ended up being a single fairly neat switch that the researchers could apply to get an entire cascade of behavioral changes because that entire cascade of changes is already one that the ants have evolved to employ. We know of similar things in humans(the most dramatic probably being the developmental trajectory into either male or female development from an originally very similar state); but we don't seem to have a 'service-sector worker', or 'pre-med' caste, despite the frantic efforts of parents to the contrary.
This isn't to say that applications in humans would be impossible; but there is a reason why we've been medicating for generations(arguably, at least since we developed brewing, possibly earlier in populations whose hunter-gathering regions had decent psychoactives naturally available): because we rarely even know what we want, except in the vaguest terms, much less how to get there.
Rpd3 is a histone deacetylase, for those who want intelligent discussion, rather than paranoid rambling.
For those who aren't up to speed on HDACs, eukariotic (which includes all multicellular organisms) genomes are folded up in the nucleus, wrapped in coils around protein complexes called "histones". As DNA has phosphate groups (the "acid" part in "deoxyribonucleic acid"), in order to wrap up the DNA compactly, these proteins need to neutralize the negative charges on the phosphate groups, which they do with positively charged lysine sidechains. But the cell can regulate how efficiently that wrapping goes by adding/removing an acetyl group to the lysines with histone acetyltransferases (HATs) and histone deacetylases (HDACs). Eukaryotes use this wrapping/unwrapping to help control gene expression: genes need to be unwrapped in order to be expressed. Normally, gene activation involves things like HDAC recruitment to remove histones from the gene in order to help unwrap the DNA and start expression.
So what's happening here is that they inject a whole bunch of this histone deacetylase into the ants' brains, which then presumably gets into the nucleus (which is actually the most interesting part, from my perspective), and rips off the acetyl groups from the histones surrounding certain genes, leading to their expression. Apparently, the Rpd3 HDAC has a location of action which specifically rips off the acetyl groups from around those genes which are involved in changing the ants' brain into a forager. (It's probably not all that precise, but it's just that Rpd3 has an activity profile which is biased toward those genes - it hits a bunch of stuff, but that's the major locations which show the biggest effect.) It could very well be that Rpd3 is one of the "master regulator switches" in ants which gets turned on in development for making foragers.
From a certain perspective, it's not all that surprising. We know that both types of ants have basically the same DNA and the same genes. The only difference between worker and guard is the gene expression profile, and sequestering unused genes in condensed chromatin (basically tightly-wrapped histones) is the best way we know about for long-term gene inactivation, short of actual DNA editing. So it makes sense that the developmental process which makes one ant a forager and one a guard involves wrapping one section or the other up in histones. Inject this HDAC into the brain, and you unwrap those sections for forager behavior. It's basically the equivalent of giving massive amounts of testosterone/estrogen to humans to perform a sex change - certain developmental features are already locked in, but injecting the hormone/HDAC changed the gene expression pattern and subsequent behavior of the individual.