How the Biggest Biological Cells on Earth Work

By Kristen Philipkoski on at

Have you ever heard of an endocycle? Endocycles are happening all around you! They're one way that biological cells grow, and they generate more than half the earth's biomass. But how exactly endocycles work has been elusive to scientists until now.

You might also be interested to know that it's the first time scientists have deciphered a new cell mechanism since the 1980s when scientists described mitosis, or cell division. Endocycling, on the other hand, increases cell mass without mitosis. Instead it doubles down on DNA and in the process doubles a cell's size. The process generates big cells in invertebrate animals and plants, and even some human tissues including placenta, liver and muscle. Most cells in plants and invertebrate animals such as insects, crustaceans, and mollusks grow by endocycling.

But scientists knew all that already. For this new research, geneticists at the Fred Hutchinson Cancer Research Center and some German and Canadian colleagues report in the October 30 issue of Nature how exactly this DNA duplication works. They figured it out by studying the fruit fly (a.k.a. drosophila).

They found that two transcription factors, or proteins that bind to specific DNA sequences and control the flow of genetic information, oscillate to facilitate the duplication process. One transcription factor called E2F is temporarily snuffed by an enzyme called CRL4. That happens during the replication. E2F comes back to life when the replication is finished, and then the cycle repeats.

Knowing this new info might eventually have implications in medicine and agriculture, but it doesn't bring scientists any big immediate eureka breakthrough. Alas, that's not how science usually works. Breakthroughs are made up of incremental steps, and even when they get there, scientists aren't alway sure it's a breakthrough. So let's just take pleasure in this bit of new knowledge about endocycling, shall we?

You should also know that this research was publicly funded! The money came from the National Institutes of Health, the National Institute for General Medical Sciences, and the National Science Foundation, as well as a some German and Canadian outfits: the German Academic Exchange Service, the German Cancer Research Center and the Canadian Institutes of Health Research.

[Nature; Image: National Science Foundation]