Laminin isoforms and lung development: All isoforms are not equal

The embryonic lung has abundant laminin isoforms. Studies of embryonic lung explants and organotypic co-cultures show that laminin α1 and laminin 111 are important for epithelial branching morphogenesis and that laminin α2 and laminin 211 have a role in smooth muscle cell differentiation. In vivo studies of laminin α5-deficient mice indicate that this laminin chain, found in laminins 511 and 521, is essential for normal lobar septation in early lung development and normal alveolization and distal epithelial cell differentiation and maturation in late lung development. Laminin α4 null mice do not have obvious lung abnormalities and laminin γ2 null mice have only minimal changes in lung development. It is clear that multiple laminin isoforms are crucial for lung development and that different laminin isoforms exhibit specific, nonoverlapping functions.