Cloning of rat fibrillin-2 cDNA and its role in branching morphogenesis ofembryonic lung

Fibrillin-2 is an extracellular matrix protein. It is associated with elast ic fibers in several tissues and is believed to serve as a ligand for alpha v beta 3 integrin, the latter being a known morphogen. In this study, the role of fibrillin-2 in lung development was investigated. Also, rat fibrill in-2 cDNA was isolated and sequenced and its spatiotemporal expression dete rmined. It had similar to 88% homology with human fibrillin-2 and had Ca2binding epidermal growth factor-like domains, transforming growth factor-be ta binding protein motifs, and two RGD binding sites. Northern blot analysi s revealed an similar to 10-kb transcript, and fibrillin-2 expression was d evelopmentally regulated, and it paralleled that of tropoelastin. At day 13 of gestation, fibrillin-2 was expressed in the mesenchyme and at the epith elial:mesenchymal interface. From day 13 to 19 of gestation, its expression intensified and was confined around the tracheobronchial airways, while it lessened during the postnatal period. Immunoprecipitation revealed an simi lar to 350-kDa band by SDS-PAGE. Treatment with fibrillin-2 antisense oligo deoxynucleotide induced dysmorphogenesis of the lung explants. They were sm aller and had rudimentary lung bud branches, collapsed conducting airways, and loose expanded mesenchyme. Concomitantly, fibrillin-2 mRNA, antibody re activity in the explants, and fibrillin-2-specific radioincorporation were reduced. Anti-alpha v and -laminin antibody reactivity and their respective incorporated specific radioactivities were unaltered. These data indicate that fibrillin-2 modulates organogenesis of the lung in the context of epit helial: mesenchymal interactions. Conceivably, the collapse of the conducti ng airways may also be related to the perturbed biology of the fibrillin-2 interacting protein, i.e., elastin, the latter being critical for the norma l biophysiology of the lungs. (C) 1999 Academic Press.