ARS | Publication request: INVOLVEMENT OF MICRORNAS IN EMBRYONIC GENOME ACTIVATION AS SHOWN BY DICER EXPRESSION IN RAINBOW TROUT

Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: July 21, 2007
Publication Date: July 21, 2007
Citation: Ramachandra, R., Gahr, S.A., Rexroad III, C.E., Yao, J. 2007. Involvement of micrornas in embryonic genome activation as shown by dicer expression in rainbow trout. Society for the Study of Reproduction Annual Meeting.

Technical Abstract: Most maternal transcripts including many housekeeping genes are degraded at or around embryonic genome activation as evidenced by our initial studies. This degradation appears to be global but highly regulated. MicroRNAs are naturally occurring small (19-24bp) RNAs that are shown to be involved in mRNA degradation and/or translation repression. We hypothesized that microRNAs are involved in the above mentioned mRNA decay process. Dicer is an enzyme involved in processing of microRNAs. It has been shown that dicer is required for normal embryonic development in zebrafish and normal differentiation and centromeric silencing in mouse embryonic stem cells. In this study, we aim to determine if dicer expression is correlated to maternal transcript decay in early embryonic development in rainbow trout. Mature oocytes (day 0) and embryos (day 1 through 7 post-fertilization) from rainbow trout were collected and used for RNA extraction (n=5). Quantitative real time PCR was used to quantify dicer mRNA levels in early stages of embryonic development in rainbow trout. Dicer transcript levels are significantly high in mature oocyes (day 0) and day 1 embryos and decrease in abundance suddenly in day 2 embryos. This down-regulation is at the time of mid-blastula which is approximately the time of embryonic genome activation in teleosts. Up-regulated dicer is involved in processing of microRNAs which are possibly responsible for degradation of other transcripts. It is also possible that the microRNAs regulate the abundance of dicer itself and down-regulate it by day 2. This is the first known study to investigate involvement of microRNAs in embryonic genome activation. Our results suggest that dicer might play a very important role in degradation of maternal transcripts and thereby embryonic genome activation.