PARENT SESSION

(M502) CROSS-SPECIES COMPARISON OF GENE EXPRESSION PROFILE IN THE OOCYTE USING OLIGONUCLEOTIDE ARRAYS.

Vallee, Maud¹, Aiba, Kazuhiro², Piao, Yulan², Palin, Marie-France³, Ko, Minoru², Sirard, Marc-Andre¹, ¹ CRBR, Universite Laval, Quebec, QC, Canada² National Institute on Aging, NIH, Baltimore, MD³ Dairy and Swine Research and Development Centre, AAFC, Lennoxville, QC, Canada

ABSTRACT- Cross-species comparison of gene expression is a powerful approach for the discovery of important genes conserved throughout evolution. The objective of this study was to identify genes expressed in the oocyte and conserved across species. We believe that these candidate genes are presumably very important in the molecular mechanisms related to the unique reprogramming functions found in oocytes. In this study, we compared the gene expression profiles of bovine, mouse and Xenopus laevis oocytes using the NIA mouse development 22K 60-mer oligo microarray from Agilent. This microarray platform contains 60-mer oligonucleotide probes representing approximately 22,000 unique mouse transcripts, assembled primarily from sequences of stem cell, oocyte and early embryo cDNA libraries. Hybridizations were performed in triplicates with total RNA from bovine, mouse and Xenopus laevis oocytes. A two rounds amplification procedure was performed to generate labeled cRNAs. Data were extracted from scanned microarray images using Feature Extraction 5.1.1 software (Agilent), dye-normalized, and background-subtracted. Analysis was subsequently performed by ANOVA tool (NIA) and data reproducibility was verified by calculating the coefficient of correlation across the replicated experiments. This was done to see if the variability observed was similar within the three species or if it was higher in the bovine and/or Xenopus laevis hybridizations. All coefficients of correlation are above 0.90 for replicated experiments within each species, and not significantly higher in the mouse hybridizations. Analysis based on intensity values revealed that 14,086 transcripts are commonly expressed in oocytes from all three species when a cut off value of log intensity > 2.5 is chosen. From this subgroup, 80% of the oocyte-specific genes previously identified in the NIA EST collection are present. Moreover, detection of numerous genes already known to be associated with oocytes such as gdf9, bmp15, and h1foo increased confidence in the quality of the hybridizations. Results of our study demonstrate the feasibility of cross-species hybridization with oligonucleotide arrays. Further characterization of the uncharacterized cDNAs will be necessary to explore their putative role. Research supported by NSERC Canada.

KEY WORDS: oocyte, gene expression, microarray