Retrotransposon gene codes for placenta

Researchers have provided the first direct evidence that an evolutionarily conserved, retrotransposon-derived gene is essential for embryonic development, at least in mice, according to a study published in Nature Genetics this week. The findings suggest that the mammal-specific gene, Peg10, could have transformed egg-laying mammals into placental mammals more than 92 million years ago.

This gene family originated before the emergence of placental mammals, agreed Jean-Nicolas Vollf, at the University of Würzburg in Germany, who did not participate in the study. "There is one example of the genes being present in marsupials," he said, meaning that the domestication of the retrotransposon -- which led to the formation of the Peg10 gene family -- occurred before the formation of placental mammals.

The Japanese team, led by Tomoko Kaneko-Ishino from Tokai University in Japan, studied Peg10 knockout mice made by recombinant and cloning techniques, and found that no embryos survived...