Isolation of Novel cDNAs by Subtractions between the Anterior Mesendoderm of Single Mouse Gastrula Stage Embryos

Abstract

AbstractThe anterior mesendoderm of mid- to late primitive streak stage mouse embryos has the ability to induce anterior neuroectodermal fate in naive epiblast [S.-L. Ang and J. Rossant (1993)Development118, 139–149]. A number of genes have been found to be expressed in this tissue, notably the transcription factorLim1. Lim1-null mice have anterior mesendoderm defects that result in a lack of head formation. Thus, the anterior mesendoderm of gastrula stage mouse embryos should expressLim1-regulated genes that are essential for head development. To identifyLim1-regulated genes, a differential screen with subtraction was developed, using cDNA pools that were amplified from the anterior mesendoderm of single wild-type andLim1-null gastrula stage embryos. This novel screen strategy has yielded 22 cDNAs that show differential expression between anterior mesendoderm cells of wild-type andLim1-null embryos. The expression of one novel cDNA SII6 initially colocalizes withLim1in the anterior mesendoderm of gastrula stage embryos. Moreover, SII6 expression is undetectable in the anterior mesendoderm ofLim1-null embryos. This screen identifies a set of putativeLim1target genes that may have important roles in vertebrate head formation. Furthermore, this differential screen strategy should provide a broadly applicable approach to identify differences in gene expression between embryonic tissues of limiting quantity