Reproduction Abstracts

Gamete final maturation, fertilization, and embryo cleavage occur in the oviduct. It is known that oviductal luminal fluid composition differentially changes in the presence of oocytes, spermatozoa or embryos, prompting for a molecular cross-talk between the gametes/embryo and the oviductal epithelium. However, our understanding of the regulatory molecular mechanisms of gamete/embryo-maternal cross-talk is still fragmentary and controversial. The deciphering of these mechanisms could have a major impact on the optimization of assisted reproductive techniques and reproductive control strategies. The Notch cell signaling pathway is known to regulate cell communication in several embryonic and adult tissues. Our research goal is to evaluate the role of Notch signaling in gamete-maternal cross-talk in the bovine model. The expression of Notch components (receptors: Notch1–4; ligands: Dll1, 3–4, Jagged1 and 2; effectors: Hes1 and 2) was analyzed in the oviductal isthmus, ampulla, and infundibulum epithelia of prepubertal (n=3) and cyclic (estrous: n=3 and metaestrous phase: n=3) heifers by immunohistochemistry. Gene transcription/expression of Notch components was analyzed in ejaculated frozen-thawed spermatozoa by RT-PCR (Notch1–4, Dll1, Dll4; Jagged1 and 2) and immunofluorescence (Notch3, Jagged1 and 2). Notch1–3, Dll4 and Hes1 and 2 proteins are expressed in the epithelium of all oviduct segments, whereas Dll3 and Jagged2 are not expressed. The expression of Notch4 and Jagged1 is affected by estrous cycle stage and oviductal segment. Gene transcription and expression of Notch3 and Jagged2 was detected in spermatozoa, whereas Jagged1 is only found at the protein level. This temporal and spatial expression pattern of Notch components prompts for a regulatory role of Notch signaling in the oviductal epithelium and spermatozoa-oviductal cross-talk.