The γ3 chain of laminin is widely but differentially expressed in murine basement membranes: Expression and functional studies

Laminins are heterotrimeric extracellular glycoproteins found in, but not confined to, basement membranes (BMs). They are important components in formation of the molecular networks of BMs as well as in cell polarity, cell differentiation and tissue morphogenesis. Each laminin is composed by an alpha, a beta and a gamma chain. Previous studies have shown that the gamma 3 chain is partnered with either the beta 1 chain (in placenta) or beta 2 chain (in the CNS) (Libby et al., 2000). Several studies, including our own, suggested that the gamma 3 chain is expressed in both apical and basal compartments (Koch et al., 1999; Gersdorff et al., 2005; Van and Cheng, 2006). This study investigates the expression pattern of the gamma 3 chain in mouse. We developed three new gamma 3-reactive antibodies, and we show that the gamma 3 chain is present in BMs. The distribution pattern is considerably more restricted than that of the gamma 1 chain and within any tissue there is differential deposition into BM compartments. This is particularly true in the retina and brain, where gamma 3 is uniquely expressed in a subset of the vascular basement membranes and the pial surface. We used conventional genetic ablation techniques to remove the gamma 3 chain in mice; unlike other laminin null mice (alpha 5, beta 2, gamma 1 nulls), these mice live a normal lifespan and have only minor abnormalities, the most striking of which are ectopic granule cells in the cerebellum and an apparent increase in capillary branching in the outer retina. These data support the suggestion that the gamma 3 chain is deposited in BMs and contributes some unique properties to their function, particularly in the nervous system. (c) 2011 Elsevier B.V. All rights reserved.