Fertilization and development of mouse embryos occur in the ampullae of oviduct. We hypothesize that fetal-maternal communication exists in the preimplantation period, allowing optimal development of embryos. It is known that embryotrophic factors from oviduct affect the development of embryos. Although embryos affect their own transport in the oviduct, the mechanism of action is unknown. As a step toward understanding the action of embryos on oviductal physiology, we adopted suppression subtractive hybridization (SSH) to compare the gene expression in the mouse oviduct containing early embryos with that of oviduct containing oocytes. Ten to twelve 1-cell mouse embryos were transferred to one oviduct of a foster mother and similar number of oocytes were transferred to the contralateral oviduct. The animals were sacrificed after 48 h and their oviducts were excised for mRNA study. Using SSH, we screened out 250 putative positive clones from the subtracted embryo-ontaining oviduct library and 97 of them were screened positive by reverse dot-blot analysis. DNA sequence analysis identified genes that shared high homology with sequences in GenBank/EMBL database with unknown functions. Overall, 13 of the 90 high-uality sequences (14%) were homologous to 6 different genes previously described. Reverse Northern analysis confirmed that the expression of these genes were higher in the embryo-containing oviduct than in the oocyte-containing oviduct. About 12% of these clones (11/90) were novel. This article is the first to report identification of genes in the oviduct that are upregulated in the presence of embryos during the preimplantation period. (C) 2002 Elsevier Science (USA).