Irx1 and Irx2 expression in early lung development

We describe a comparative lung expression analysis of the murine Irx1 and I rx2 genes. At embryonic day 8.5 (E8.5), the Irx1 and Irx2 expression starts in the foregut region, where the laryngo-tracheal groove will form. The ex pression is prominent in the lung epithelium during glandular development. It declines at the end of the canalicular phase. We further compare the Irx 1 and Irx2 expression domains to Gli1, 2, 3 and Mash1. Their homologues in Drosophila melanogaster are known as regulative partners of the iroquois co mplex. The Irx and Gli genes are coexpressed in the developing lungs at the same time. Their transcripts are not localised in the same cells but adjac ent to each other in either mesenchymal or epithelial structures. It is tho ught that the lung development is regulated by the mesenchymal/epithelial i nteractions. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.