Spatiotemporal localization of flectin in the mouse embryo

Flectin is an extracellular matrix (ECM) protein that was originally extracted from the interphotoreceptor matrix of the developing eye in the chick embryo (Mieziewska et al., I994). We recently reported on a specific left/right asymmetric expression of flectin prior to and throughout the looping process during heart development in avian embryos. The present study was to analyze flectin distribution using flectin antibody F-22 in the mouse embryo between embryonic day (ED) 7.5 to ED 15 to determine whether flectin similarly localizes to specific regions in the mouse embryo as in the avian during development. Immunotustochemical localization of flectin was performed in ED 7.5, 8.5, 11 and 15 mouse embryos. In ED 7.5 embryos, flectin localizes in placenta! tissue and is present in the heart forming regions (HFRs) Greater flectin staining is present in the left HFR than right; also, the left HFR appears further in its development than the right. In ED 8.5 embryos, flectin localizes in an asymmmetric fashion in the myocardium and in the ECM of the looping heart. Flectin is expressed in neural crest cell migration pathways near the neural tube, as well as in the branchial arches. In ED 11 embryos, flectin is expressed generally in the future conotruncus region of the heart and asymmetrically in the bulbus cordis region. It is also localized in specific regions of the developing brain, in the somites, and in areas of chondrogenesis In ED 15 embryos, flectin localization is no longer apparent in the heart Flectin is expressed at key developmental stages in different matrix components of a number of vertebrate species. This molecule appears to be evolutionarily highly conserved and to play an essential role in development in a number of tissues.