There is a fish that lives its entire life in half a year. The African killifish ages so fast that scientists can watch its eyes go from youth to old age in just a few weeks. But to understand which genes switch on and off along the way, you need an accurate map of those genes. The old map was poor: nearly half of its entries looked like nameless numbers, and it was impossible to tell what exactly was changing.
The new map is built differently. Scientists took retinas from young and old fish, read all the RNA molecules end to end without chopping them into pieces, and assembled a complete list of genes. Now 71.9% of genes have meaningful names, and almost all of them match human genes. When the same data were analyzed with the new map, the share of correctly recognized molecules rose, and a quarter more cells were found.
A comparison of young and old retinas revealed 1683 genes with altered activity. Some genes linked to inflammation ramp up, while others responsible for cellular energy wind down. It is like an old house where the heating breaks first and then chaotic repairs begin. Researchers can now study eye aging in this fish and compare the results with human data. The map, however, still works well only for the retina and the brain; for other organs it needs further refinement.
The African killifish lives only 4-6 months, yet its retina ages much like a human one: DNA damage accumulates and visual acuity declines. It also carries two nearly identical green opsin genes, and with age one of them goes silent.
In Alan Dean Foster's novel 'The Man Who Used the Universe,' aliens live very short lives but have complex biology. The killifish, as a model of accelerated aging, resembles such fictional species, letting us study processes that stretch over decades in humans.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.