Immunohistochemical localization of entactin and laminin in mouse embryos and fetuses.

The temporal appearance and the anatomic distribution of entactin in the developing mouse embryo was studied by light and electron microscopic immunohistochemistry and compared with the appearance and the distribution of laminin. Immunohistochemically detectable entactin first appeared in the hatched blastocysts, in contrast to laminin which became apparent as early as the 8-cell stage of development. However, beginning with the appearance of entactin in the hatched blastocyst, antibodies to these two basement membrane glycoproteins co-localized in all extraembryonic matrices. These findings indicate that the synthesis of entactin and laminin is asynchronous in the early stages of mouse embryonic development but becomes synchronized in the postimplantational stages of development.