Novel differential transcript expression identified by LongSAGE in the mouse endometrium during the implantation...

Full development of a receptive uterus is necessary for embryo implantation; however, many genes that are required for the endometrial modifications that occur during this process remain unidentified. To identify novel genes that control endometrial modifications during this period, we investigated the differential gene expression profile in the endometrium of mice on days 2 (D2) (pre-implantation) and 4 (D4) of pregnancy (i.e., the implantation window) using 17-bp long serial analysis of gene expression (LongSAGE). One hundred fifty-six tags were annotated as unique transcripts. Of these, 101 tags were significantly upregulated, and 55 tags were downregulated in the D4 library relative to the D2 library. These differentially expressed genes should therefore be of increased importance in the establishment of uterine receptivity. The differential expressions of certain of the identified genes, namely, Hspa8, Tctp, Sparc, Ifitm1, Ik, serbp1 and Dnmt1, were validated by semi-quantitative RT-PCR and/or immunohistochemistry. Functional grouping analysis classified 86 of the mapped tags into 17 categories, which are closely associated with morphological modifications of the endometrium during pregnancy. Ingenuity pathways analysis revealed that the identified differentially expressed genes fell into six primary networks, which themselves contain numerous factors that are related to key modulators of signaling pathways that are vital for endometrial modifications. These findings will aid in the further understanding of the molecular events that underlie the implantation physiology in mice.