These results alone are cause for any lab to start chilling the champagne, yet a surprising coda to the study, leaves readers with yet another revelation. Collaborating with Fengli Guo, Ph.D., head of the Stowers electron microscopy core, the team prepared highly magnified images of mouse sperm and observed that both Ell3 and Pol II were present, in sperm nuclei.
In mammals, gene expression regulated by Pol II, a process known as transcription, does not begin until the formation of a single-celled zygote, that is, well after the union of sperm and egg germ cells. "It is very significant that Ell3 and other factors that regulate transcription are found in sperm," says Lin, the study's first author. Lin is cautious in interpreting this finding, "but it would be very exciting to further investigate whether transcription factors found in sperm could contribute to the decondensation of sperm chromatin or even further gene activation after fertilization by serving as epigenetic markers."
Shilatifard is also cautious as questions remain to be explored, among them whether Ell3 and Pol II actually contact DNA inside sperm or whether similar processes occur in unfertilized eggs and function in this process. Nonetheless, he feels this finding has fundamental implications, not only for development, but also for where he's going next.
"This work has opened up a whole new area of research in my lab," says Shilatifard, who has in the last decade focused on aberrant gene expression associated with leukemia. "If we find that transcription factors bind to specific regions of chromatin in germ cells, I may focus on germ cells in the next few decades. This would open a huge door enabling us to determine the role of these factors in early development."
|Contact: Gina Kirchweger|
Stowers Institute for Medical Research