However, at day 14 of the estrous cycle only subtle differences were observed in their transcriptomes by endometrial receptivity. To refine these results, and to obtain information about expression earlier in estrous, we performed endometrial expression profiling at days 3 and 7 of estrous in cows from high and low receptivity groups. Additionally, transcription factor analyses were conducted to identify the cascade of upstream transcriptional regulators Lomitapide Mesylate inducing gene expression changes in the endometria. Embryo implantation is a complex process. Successful implantation requires appropriate communication between the embryo and the maternal endometrium, a tissue that is crucial for the establishment and maintenance of pregnancy. A receptive endometrium and a normal and functional embryo at the blastocyst developmental stage are prerequisites of a successful implantation, which is characterized by a synchronized dialogue between maternal and embryonic tissues. However, the regulation of implantation remains incompletely understood. On one hand, the process of implantation is driven by embryonic signals conveyed through various proteins, cytokines, and growth factors that systematically modulate maternal anatomy, endocrinology, immunology, and physiology to create an environment conductive to fetal development and survival. On the other hand, however, inadequate uterine receptivity is thought to be responsible for two-thirds of implantation failure. A recent report described transcriptional changes in the endometrium during the menstrual cycle and embryonic implantation in human. Similarly, expression profiling has been performed during both the estrous cycle and implantation in cattle, even Gomisin-D accounting for different biotechniques used to derive embryos. These reports identified the endometrium as an early sensor for the presence and implantation of embryos in the uterus. The microarray data reported here indicate that endometrial expression patterns and alterations of transcript abundance are indicative of the receptivity of the endometrium and, thus, of pregnancy success. Several molecules involved in integrin signaling, cytoskeleton signalling, and Rac signaling were enriched in the high receptive endometrium at the beginning of the estrous cycle. Transcripts of these pathways were found to increase during the window of implantation and were proposed as markers for the implantation process. Integrins participate in cell�Cmatrix and cell�Ccell adhesion in many physiologically important processes. Cellular aggregation leads to the recruitment of a network of cytoskeletal proteins and intracellular signaling complexes. The acquisition of adhesion ligands, together with the loss of inhibitory components that may act as a barrier to an attaching embryo, contribute to endometrial receptivity. In cattle a number of mRNAs coding for components of the cytoskeleton and extracellular matrix proteins were as enriched at estrous. Our study shows that genes of molecular signaling pathways that determine the communication skills of the endometrium are differentially expressed between the high and low receptive groups at a time early in advance of implantation. Many transcripts showed lower abundance in the low receptive endometrium at 
day 3 of estrous belong to biofunctions relevant to energy supply, including mitochondrial pathways. This indicates that defects in these pathways may contribute to the development of low receptive endometrium. The role of estrogen in directly and indirectly affecting mitochondrial activity is well established and was functionally exploited in experiments using estrogen receptora knockout mice and ovariectomized rats in combination with estrogen supplementation. Others reported that estrogen increases NRF-1 transcription, resulting in a coordinated increase of expression of nuclear and mitochondrial-encoded genes.