Differential gene expression in day 12 and day 15 equine conceptuses

Complex changes in gene expression must occur at the proper time and in the appropriate tissues for pregnancy to be successful. Therefore, research aimed at defining the regulation of gene expression in conceptuses is of critical importance. However, information on developmentally regulated changes in gene expression in horse conceptuses is sparse and inadequate. In the present study, suppression subtractive hybridization was used to identify genes that are expressed more highly at day 15 than on day 12 of gestation. This period encompasses maternal recognition of pregnancy and the beginning of mesoderm formation and gastrulation. Clones (n=50) were isolated, partially sequenced and the sequences obtained were compared with known sequences to determine their identity. Analysis of glyceraldehyde-3-phosphate dehydrogenase and alpha-fetoprotein (AFP) in subtracted and unsubtracted samples indicated a high efficiency of subtraction. Some of the genes identified included pregnancy-associated glycoprotein (PAG), fumarylacetoacetase, cytokeratins 8 and 18, and isocitrate and succinate dehydrogenases. Differential gene expression of PAG and AFP between days 12 and 15 was confirmed. PAG expression increased approximately 30 times and AFP expression increased at least 1000 times between days 12 and 15.