Extracellular matrix in development of the early embryo

Entactin and laminin gamma1-chain gene expression in the early chick embryo

“…The in situ hybridization results ( Fig. 2A) in concert with the immunoprecipitation (Zagris et al, 2000) and immunohistochemistry findings (review Zagris 2001) showed that strong signals of laminin γ1 chain mRNAs were detected at stage X but massive expression of the protein was detected shortly thereafter in the extracellular matrix, including the basement membrane on the ventral surface of the epiblast and in epiblast and hypoblast in embryos at stage XIII. Pertinent to these results are data which showed that also the hypoblast synthesizes non-collagenous glycoproteins which contribute to the extracellular matrix, including the basement membrane, in chick blastula (stage XIII) (review Zagris 2001).…”

“…The high affinity binding of entactin to laminins mediates the connection of laminins to the collagen IV network and to other proteins such as perlecan and is considered to be an essential step in the stabilization of basement membranes and the pericellular matrix. Massive presence of laminin and entactin coincided with the formation of the first basement membrane on the ventral surface of the epiblast and the epithelialization of the epiblast and was also detected in the extracellular matrix in the blastocoel in embryos at stage XIII (review Zagris, 2001). The presence of entactin and laminin before formation of the primitive streak indicates a primary role of these gene products during the morphogenetic movements of gastrulation.…”

“…2E. Neural crest cells migrate extensively along well-characterized pathways through cell-free space rich in laminin/other matrix molecules and laminin is enriched in basement membranes of the neural tube, ectoderm and somite (Duband and Thiery, 1987;Zagris, 2001). It is intriguing neural crest cells express laminin genes strongly (Zagris et al, 2000) and even single cells within a stream of migrating neural crest cells along the neural tube ventrally can be seen labeled (Fig.…”

“…Entactin may be essential as a bridging molecule for the assembly of the basement membranes and it may modulate the biological activities of the macromolecules to which it binds in the developing embryo. The first extracellular matrix starts to assemble into an organized fibrilar network in the blastocoel at stage XIII (blastula) before the initiation of the first major cellular migrations of gastrulation in the early embryo (Zagris, 2001). Cell interaction with extracellular matrix plays an important role in cell attachment, directional migration, mitogenetic modulation, neurite outgrowth, axon guidance, survival of cells, maintenance of differentiated cell phenotypes and the induction of new expression patterns.…”

“…3 E,e) but gave no signal in endoderm and in lateral ectoderm (not shown). After the neural plate folding to produce the neural tube, immunofluorescence had shown strong presence of laminin (Duband and Thiery, 1987;Zagris, 2001) and entactin (Zagris et al, 1993) in the lumen and surrounding the neural tube. The intense expression of laminin plate anchoring to the mesoderm and furrowing to form the neural tube in the chick embryo; inhibition of function of the α7 integrin by blocking antibodies showed that α7 integrin-laminin signaling may play a critical role in tissue organization of the neural plate and neural tube closure (Zagris et al, 2004).…”