Frogs’ eggs key to anemia research

Published 9:00 pm Monday, January 30, 2006

PORTLAND, Ore. – A large, clawed frog is helping Oregon Health and Science University researchers better understand how the rare genetic disorder Fanconi anemia leads to DNA damage that typically causes cancer and early death.

An extract from the eggs of the African clawed frog suggest that Fanconi anemia resulted from a genetic defect in the ability to repair DNA damage during replication – when strands of DNA copy themselves to help make new cells that are the building blocks of every living thing.

Maureen Hoatlin, an OHSU molecular biologist who led the study, said there are many advantages to using frog eggs, instead of human cells, to study Fanconi anemia.

“In human cells, most of the Fanconi proteins are hard to detect, so you have to grow millions of cells over long periods of time to collect enough to study,” Hoatlin said.

In the frog eggs, however, Fanconi proteins are stockpiled and cell divisions occur at the same time, greatly speeding up the process.

The use of frog eggs in research has been common since the mid-1980s, when scientists started using pellet-sized eggs to probe the ways DNA is replicated – something not easily done for humans and other mammals.

Since a frog egg is not fertilized until after it is laid outside the body of the female frog, it’s in a relative state of suspension until it is fertilized.

During this time, scientists can use chemicals and a centrifuge to keep the DNA from replicating. This creates an extract rich in all the essential components needed for replication.

Then, by chemically activating the extract and adding sperm DNA from the male frog, the proteins in the extract unwind the DNA and the replication process begins while researchers study the process.

“That’s just the beginning of what we want to do with these extracts to study how the Fanconi proteins work,” Hoatlin said.

The study was published this month in the journal Molecular and Cellular Biology.