251 COMPARATIVE ANALYSIS OF GENE EXPRESSION PATTERNS IN PORCINE PRE-IMPLANTATION EMBRYOS DERIVED FROM DIFFERENT ORIGINS

Abstract

The amount of information gathered on the kinetics and quantitative profile of gene expression in nuclear transferred (NT) pre-implantation embryos is still scarce and limited to a handful of genes in pig. In the present study, we compared the relative abundance (RA) of six development-related genes of pre-implantation embryos from different origins. Cumulus-oocyte complexes (COCs) were matured, fertilized and cultured by the method of Abeydeera et al. (2000 Theriogenology 54, 787-797). Parthenogenetic (PA) and NT embryos were produced as described by Kim et al. (2005 Mol. Rep. Dev. 70, 308-313). Sets of 10 embryos each at 4-cell, 8-16-cell, morula, and Day 7 blastocyst stages were used to extract total RNA for analyzing the expression pattern of Bax (pro-apoptotic), Bcl-xl (anti-apoptotic), Oct-4 (pluripotent transcription), Stat3 (cytoplasmic transcription), IFN-tau (implantation) and VEGF (vasculogenesis) genes (three replicates) with real-time quantitative PCR (LightCycler�; Roche Diagnostics, Mannheim, Germany) following RNA isolation (with Dynabeads� mRNA Direct" kit; Dynal, Oslo, Norway) and cDNA amplification (Oligo (dT)12-18 primer and Superscript" III cDNA synthesis kit; Invitrogen, Carlsbad, CA, USA). The expression of each gene was normalized to Histone H2A expression. Statistically significant (P < 0.05) differences in gene expression were analyzed by ANOVA. Oct-4, Stat3, Bax, and Bcl-xl were expressed at the 4-cell stage. However, IFN-tau and VEGF were expressed at the morula stage. The expression patterns of all genes throughout the embryonic development in all types of embryos were similar. However, the relative abundance (RA) of Bax in the 8-16 cell stage of NT and PA was significantly (P < 0.05) increased as compared to that in IVP counterparts. The RA of Oct-4 and Bcl-xl did not differ throughout all stages in NT and PA embryos. There were no significant differences in all types of embryos with respect to the RA of Oct-4 and Bcl-xl with exception of the blastocysts in NT (significantly decreased, P < 0.01). The RA of Stat3 was significantly (P < 0.05) increased in the 8-16 cell stage (NT and PA) and in blastocysts (NT). Similarly, the RA of IFN-tau was significantly (P < 0.05) increased in NT blastocysts. The RA of VEGF was not significantly different in all stages and types of embryos except NT blastocysts (decreased expression, P < 0.01). These results suggest that expression patterns of Bax, Bcl-xl, Oct-4, Stat3, IFN-tau, and VEGF can be used as markers to assess the developmental competence of porcine nuclear transfer embryos. This work was supported by Grant No. 1000520040020000 from Biogreen 21, Republic of Korea.