Submission Number: GAR-4-25-20

Abstract Number: 15

TRANSCRIPTIONAL CO-ACTIVATOR EXPRESSION AND INTRACELLULAR TRAFFICKING DURING OOCYTE DEVELOPMENT, MEIOSIS, AND EARLY EMBRYOGENESIS.

Gary D Smith*, Xiao-Tie Liu, Rowena Angeles, Hiroto Uechi and Roland PS Kwok

Depts of OB/GYN, Physiology, Urology, and Biological Chemistry, Reproductive Sciences Program, University of Michigan, Ann Arbor, MI. ¹

Abstract:
CREB binding protein (CBP) and p300, two transcriptional co-activators, have been shown to regulate transcription by acetylating histones and recruiting RNA Pol II to transcription start-sites. We have recently shown that mouse oocytes contain CBP and p300, which translocate from the cytoplasm to the nucleus as growth and transcriptional activity is initiated. Objectives of current studies were to determine CBP/p300 gene expression, protein expression and intracellular trafficking during oocyte and early embryo development. Using RT-PCR, we have identified CBP transcripts, but not p300, in oocytes. The CBP transcripts were markedly reduced in 2-cell embryos and absent until the blastocyst stage. In contrast, p300 transcripts were undetectable in 2-cell embryos, but were first detected in 4-cell embryos. Using immunocytochemistry and confocal microscopy, we have shown that nuclear CBP translocates from the nucleus to the cytoplasm upon germinal vesicle breakdown, and remains in the cytoplasm during development through metaphase II. CBP relocates to the nucleus following fertilization, and is predominantly nuclear at the 2-cell stage and throughout preimplantation embryo development. However, p300 remains associated with chromatin and/or spindles during meiotic progression to metaphase I and II. P300 translocates from the nucleus to the cytoplasm upon fertilization and is markedly reduced within the nucleus at the 2-cell stage through blastocyst formation. These results indicate that CBP and p300 gene expression and intracellular trafficking are different during oocyte/preimplantation embryo development, suggesting that CBP and p300 may play different roles in development. Collectively, the presence of CBP/absence of p300 within the 2-cell embryo nucleus, CBP's histone acetyltransferase activity and its role in RNA Pol II transcription would suggest that CBP is an excellent candidate for the regulation of zygotic genome activation. .

Keywords: preimplantation embryo, oocyte, transcriptional co-activators

This abstract is being presented at: 3:30 PM in session:
SESSION 3: DETERMINANTS OF NORMAL AND ABNORMAL PREIMPLANTATION DEVELOPMENT