Mother frogs control gene activity in embryos

NIJMEGEN, Netherlands, Dec. 18 (UPI) -- Mother frogs use special egg cell proteins to control gene regulation and expression in each individual embryo.

In a study, published in the journal Nature Communications, researchers at Radboud University showed frog embryos not only inherit half of their genetic code from their mothers, but also get instruction on how to use their DNA.

Researchers followed the development of the western clawed frog, Xenopus tropicalis, as the species develops rapidly, with only six hours between fertilization and embryonic RNA production.

The mother frog influences gene expression by endowing embryos with proteins and RNA, which establish strict parameters for which genes can and cannot be turned on or off.

Researchers were surprised by the level of influence mothers have on their offspring's gene expression. When scientists manipulated embryo DNA to turn off RNA production, they observed few changes in embryonic development.

"That was not only the case for important genes during early embryonic development, but also much later, well into the stages of organogenesis," study author Saartje Hontelez, a biologist at Radboud, said in a press release. "This shows very clearly that the mother is responsible for the early stages of embryonic development, and that her influence is still strongly present in later stages as well."

Given the large scale and fast pace at which amphibian reproduction happens, a strong maternal influence makes sense.

"When you consider the amount of eggs a frog lays, and how many of those eggs successfully develop into frogs, it is not surprising that embryos get a little help from their mother," Hontelez explained. "It is a pre-programmed system, making sure that early embryonic development usually succeeds."

Though mammalian embryos begin making their own RNA after initial cell division -- much earlier in the development process than reptiles and amphibians -- researchers say the new evidence suggests similar mechanisms are likely at play in humans.