Implantation, Pregnancy and Parturition
(W573) AP-2 TRANSCRIPTION FACTOR DURING BOVINE EMBRYO DEVELOPMENT AND PLACENTA FORMATION.
Aston, Kenneth1, Johnson, Heidi1, White, Kenneth1, Winger, Quinton1, 1 Utah State University, Logan, UT
ABSTRACT- Mouse embryos lacking AP-2 have defects in extraembryonic trophoblast, fail to implant appropriately, and die at around 7.5dpc. The evidence is strong that this mutation affects the proliferation of trophoblast cells and their differentiation into giant cells. Abnormal placental development remains the major cause of pregnancy failure during the production of bovine nuclear transfer (NT) embryos. In the bovine placenta the binucleate cell is an analogous cell type to the mouse giant cell and therefore, AP-2 may play a role in regulating binucleate cells. Interestingly, in bovine NT pregnancies it is common to observe a large increase in the number of binucleate cells. We would like to investigate the potential role of AP-2 in bovine embryo development and any potential link to increased binucleate cells in the NT embryos. However, very little is known about AP-2 in the cow. In the mouse AP-2 has been detected throughout the pre-implantation stages of embryo development. Bovine nucleotide sequence was not available for AP-2, primers were designed based on the mouse sequence and were able to amplify a 320 bp AP-2 RT-PCR product from bovine blastocysts. Comparing this sequence we found a high similarity to dog (93%), human (90%) and mouse (83%) AP-2 sequences. The AP-2 transcripts were detected by RT-PCR in 8-cell, morula and blastocyst stage embryos but unlike the mouse, were not detected in oocytes. In addition to embryos, we collected tissue from cotyledon areas at d60 and d90 of pregnancy from control and NT bovine pregnancies. AP-2 transcript was detected in cotyledons from both control and NT pregnancies from both d60 and d90 samples. Differences in the level of expression in clones compared to control cotyledons have been detected and need to be further verified since AP-2 may be responsible for the increased numbers of binucleate cells in clones. The presence of AP-2 in the cow suggests the potential for a similar critical role of AP-2 during bovine development as has been reported in the mouse. Inappropriate gene regulation of AP-2 may lead to placenta defects that cause NT embryos to fail.
KEY WORDS: AP-2, bovine, nuclear transfer, embryo