Analysis of mRNA expression profiles in bovine endometrium during the pre-attachment period. Bos taurus

The endometrium plays a central role among the reproductive tissues in the context of early embryo-maternal communication and pregnancy. This study investigated transcriptome profiles of endometrium samples from Day 18 pregnant vs. non-pregnant heifers to get insight into the molecular mechanisms involved in conditioning the endometrium for embryo attachment and implantation. Using a combination of subtracted cDNA libraries and cDNA array hybridization 109 mRNAs with at least twofold higher abundance in endometrium of pregnant animals and 70 mRNAs with higher levels in the control group were identified. Among the mRNAs with higher abundance in pregnant animals at least 41 are already described as induced by interferons. In addition, transcript levels of many new candidate genes involved in regulation of transcription, cell adhesion, modulation of the maternal immune system, and endometrial remodeling were found as increased. The different expression level was confirmed with quantitative real-time PCR for nine genes. Localization of mRNA expression in the endometrium was shown by in situ hybridization for AGRN, LGALS3BP, LGALS9, USP18, PARP12, and BST2. A comparison with similar studies in humans and mice revealed species-specific and common molecular markers of uterine receptivity. Keywords: Comparison of endometrium of pregnant versus control animals Overall design: Endometrial tissue samples of day 18 pregnant cows (n=4) were compared to non-pregnant controls (n=6). First, subtracted cDNA libraries were produced enriched for cDNAs of genes upregulated either in pregnant animals (18KB) or in the controls (18KO). 1536 clones of every library were picked and PCR-amplified cDNA fragments were spotted on a separate array, respectively. These two arrays were then simultaneously hybridized with P-33 labeled probes derived from the 10 tissue samples (10 hybridizations, 18KB and 18KO array together in 1 hybridization vial). Differentially expressed cDNA clones in comparison of the pregnant and the non-pregnant control group were detected with SAM (Significance analysis of microarrays, Tusher et al. 2001) according to the following parameters: fold-change = 2; FDR = 1%. Signals of these cDNA clones were manually evaluated to eliminate false-positive signal differences. The differentially expressed cDNA clones and some additional interesting cDNA clones were sequenced.