Expression of cell adhesion molecules during human preimplantation embryo development

Formation of a fully differentiated, implantation competent blastocyst requires the expression of a complex repertoire of molecules. However, the events that drive morphogenesis are poorly elucidated in the human embryo. In this work, we describe the amplification of representative cDNAs from morphologically and developmentally normal, individual human embryos at all stages from pronucleate to blastocyst. These cDNAs were probed to reveal the temporal expression pattern of cell adhesion molecules thought to play a key role in murine preimplantation embryo development. We demonstrated constitutive expression of beta actin, beta1 and alpha6 integrins, ZO-1 and E-cadherin, as shown previously in mouse embryos. No expression of beta3, alpha2, alpha3 or alpha7 integrins nor of L or P selectin was detected at any stage of preimplantation development. beta5 integrin showed a regulated pattern of expression and was not expressed in blastocysts, while desmocollin-2 could only be detected at the blastocyst stage. Expression and localization of beta1, beta5 and alpha6 integrins and ZO-1 and E-cadherin proteins was confirmed in blastocyst stage embryos by immunocytochemistry. We have identified differences in the expression of integrin molecules between mouse and human embryos, and propose a role for alphavbeta5 and alpha6beta1 integrin dimers in the human embryo at implantation.