PARENT SESSION
IMPLANTATION AND PREGNANCY - A

Monday, August 2, 2004
10:30 AM–12:30 PM
Buchanan Courtyard

(255) DETECTION OF OCT-4 GENE EXPRESSION IN PORCINE CONCEPTUSES DURING PREIMPLANTATION DEVELOPMENT.

Spencer, Diana¹, Ross, Jason ², Geisert, Rodney², Rickords, Lee^{1, 3}, ¹ Dept of Biochemistry, Tulsa, OK² Dept of Animal Science, Stillwater, OK³ Dept of Animal, Dairy and Veterinary Sciences, Logan, UT

ABSTRACT- Oct-4 is a transcriptional regulator in pluripotent cells during embryonic and germ cell lineage prior to cellular differentiation. This critical factor is presumed to be involved with murine, bovine and porcine preimplantation development. An essential component of regulation for germline maintenance, Oct-4 is expressed in the murine inner cell mass (ICM) but not in the pre-trophectodermal cells. In contrast to murine Oct-4 expression, bovine and porcine expression is detected in both the ICM and the trophectoderm. Delayed down regulation of Oct-4 gene expression in these larger mammals may be a consequence of the lengthened period of preimplantation. Following blastulation, day 11-12 porcine embryos undergo a dramatic morphological rearrangement of their trophectoderm in which a 10-11mm spherical conceptus elongates to greater than 150mm within 3-4 h, and continues trophectodermal expansion at a much lower rate until day 15. Expression of Oct-4 has not been characterized during this unique transitional stage of development (days 10-17 of gestation). The objective of this study was to characterize the expression of the Oct-4 gene and compare the stage-specific gene expression during porcine preimplantation development. Total RNA was extracted from multiple pools of conceptuses representing development from day 10 (2-4mm), day 12 (early filamentous), and days 13, 15 and 17 of pregnancy. Employing quantitative RT-PCR, we assayed Oct-4 mRNA using 18S gene expression as a normalization control. Oct-4 expression differences between stages of embryonic development were determined using the comparative CT method. Day of conceptus development significantly affected (P<0.001) Oct-4 gene expression. Conceptus expression of Oct-4 was greatest on days 10 and 12 of pregnancy being approximately 2, 8 and 11-fold greater compared to expression on day 13, 15 and 17, respectively. The down regulation of Oct-4 gene expression between days 12 and 17 is temporally and spatially associated with extended trophoblastic elongation and placental differentiation. Results from the present study suggest that down regulation of the regulatory transcription factor, Oct-4, may be critical in trophoblastic expansion and uterine epithelial attachment during establishment of pregnancy in the pig.

KEY WORDS: embryo, implantation, OCT-4, porcine