Heparan sulfate proteoglycan (perlecan) expression by mouse embryos during acquisition of attachment competence.

Cell surface expression of the basement membrane form of heparan sulfate proteoglycan (HSPG), perlecan, basic fibroblast growth factor (bFGF) binding forms of heparan sulfate, and laminin has been examined by immunofluorescence during the attachment and outgrowth phases of mouse embryo development in vitro and in utero. The results indicate that both HSPG and laminin are expressed at the exterior surface of the trophectoderm during the attachment phase of implantation in vivo. HSPG expression correlated with acquisition of attachment competence by embryos in vitro. The intensity of immunofluorescence signal appeared to decrease by the outgrowth stage of development in vitro. It is concluded that expression of HSPG at the trophectodermal surface is coordinated with development of attachment competence by mouse embryos in vitro and in utero.