Differential expression of laminin genes in early chick embryo

The expression patterns of laminin alpha1 and beta1 genes were examined by In situ hybridization of their mRNAs in the early chick embryo from the blastoderm at stage X (morula) to the 10-somite stage. The laminin alpha1 and beta1 transcripts were found in abundance in the chick blastoderm at stage X before initiation of synthesis of the protein. Laminin polypeptides were detected shortly thereafter in embryos at stage XIII (blastula). The expression of the laminin transcripts was intense in the epiblast and in the hypoblast of embryos at stage XIII. During gastrulation (stage HH3-4), the laminin (alpha1 and beta1 cRNAs gave strong signals in the cells ingressing through the primitive streak, in the migrating mesenchymal cells and the cells of the lower layer. The expression of laminin alpha1 and beta1 genes was restricted to specific cell populations later in development. At the neurula stage (stage HH5-6), the expression of laminin transcripts was low in epithelial ectoderm and strong in chordamesoderm neural ectoderm and may implicate important developmental roles for laminin in the morphogenetic movements of neural plate bending during primary neurulation. At the 10-somite stage (stage HH10-11), the (alpha1 and beta1 cRNAs gave no signals in the neural tube, notochord, and ectoderm. The alpha1 and beta1 cRNAs gave strong signals in neural crest cells and this may indicate that the neural crest cells can produce laminin. The alpha1 cRNAs gave strong signals in the dermamyotome and no signal in the sclerotome of somites, and intense signals in the pronephric tubules. The laminin expression pattern in somites may show transient expression of the alpha1 and/or expression of a distinct alpha1 isoform in the sclerotome. The selective expression of laminin alpha1 and beta1 subunits which shows a developmentally regulated, tissue specific distribution suggests potential roles for different members of the same subfamily of genes in the developing chick embryo.