Expression Pattern Of E-cad, Ocln And Zo-1 In Cleavage-stage Monodelphis Domestica Embryos
During blastocyst formation in the laboratory opossum, M. domestica, each blastomere adheres to the zona pellucida, flattens against the zona, and later forms tight junctions with its neighbors. This contrasts greatly with mouse blastocyst formation, wherein cells adhere to each other and later form tight junctions, at no time adhering to the zona. We hypothesized that the spatio-temporal expression of the proteins encoded by E-Cad, Ocln and ZO-1 may explain the difference between eutherian (mouse) and marsupial (opossum) blastocyst formation. Confocal microscopy revealed that E-cadherin is found in both cytoplasm and embryonic coats (zona pellucida, mucoid layer). Its presence in the cytoplasm declined as blastocyst formation became imminent. The tight-junction proteins occludin and zona occludens were expressed similarly in the cytoplasm, although occludin later appeared in the perivitelline space, eventually becoming contained in the blastocoel. Both occludin and zona occludens were detected in zygotic nuclei. Occludin reappeared in larger amounts in cell nuclei during blastocyst formation. The presence of these cell-membrane proteins in nuclei warrants further investigation. Although the antibodies used in this investigation were molecularly similar only E-cadherin, not occludin or zona occludens, was detected in extracellular coats. It is thus unlikely that this E-cadherin expression pattern is artifactual. Rather, its presence in embryonic coats as well as cell surfaces (as occurs in mouse) suggests that it may facilitate blastomere-zona adhesion well in advance of blastomere-blastomere adhesion.
Wang, Vicki N., and Yolanda P. Cruz. 2010. "Expression Pattern Of E-cad, Ocln And Zo-1 In Cleavage-stage Monodelphis Domestica Embryos." Developmental Biology 344(1): 75.