In contrast to short-lived adaptive immunity, however, this small RNA-driven immunity has a long reach. The team's experiments show that the effect on fertility doesn't just impact the child alone, but also the next generation. Because the trait fertility is controlled or encoded in the RNA, "you're passing on a trait that's essentially not only controlling an event that happens in the organism's adulthood, but is also propagated to the progeny of that organism," explains Hannon.
The impact of environment
The ability of the mother to transmit epigenetic information can be altered by the environment that she finds herself in. Other researchers have found that raising the temperature in which female flies are reared raises the proportion of fertile progeny.
To the CSHL team, this suggests that "the experience of the mother translates into a dominant effect on the progeny." The group's data suggest that one way that the mother's experience might get communicated to the child is through variations in the populations of small RNAs that get deposited in the oocytes.
Now that one trait has been discovered to be driven by maternally inherited piRNA, Hannon is eager to know if the spectrum of information that's transmitted in this way can be broadened to cover other cellular processes. And of course, it also remains to be seen whether this mechanism of epigenetic inheritance is found in organisms besides fruit flies. "Small RNAs are probably deposited in oocytes of every animal," he hypothesizes.
|Contact: Hema Bashyam|
Cold Spring Harbor Laboratory