Inside every cell there are tiny workers called enzymes. One of them, EDTP, strips chemical tags off fat molecules. If there is too little of this enzyme, the cell starts to run poorly. Scientists took Drosophila flies with weakened EDTP and looked at what would change.
It turned out that these flies live shorter lives and lay fewer eggs. In males, the sperm fertilizes eggs less effectively, even though the males themselves mate even more often. When the scientists put a working copy of the gene back, the flies once again lived long and reproduced normally. So the enzyme really is the culprit.
The biggest surprise was the muscles. The scientists thought EDTP helped cells clear out junk, and that with too little of it, harmful clumps would pile up in the muscles. But the flies' muscles were healthy, and there were no clumps. In the eye, though, the same enzyme did help clear clumps. It seems that in different parts of the body the same protein does different jobs: in the eye it is like a janitor, while in the muscles it is like a traffic cop who does not haul away the trash but keeps things in order.
The human homolog of EDTP was named hJumpy because of the jumpy behavior of flies with a mutation in this gene. DJ694 flies indeed show hyperactivity when startled and have trouble stopping their wing buzzing after landing.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.