The role of the laminin β subunit in laminin heterotrimer assembly and basement membrane function and development in C. elegans

Laminins are components of basement membranes that are required for morphogenesis, organizing cell adhesions and cell signaling. Studies have suggested that laminins function as α_x β_y γ_z heterotrimers in vivo. In C. elegans, there is only one laminin β gene, suggesting that it is required for all laminin functions. Our analysis is consistent with the role of the laminin β as a subunit of laminin heterotrimers; the same cells express the laminin α, β, and γ subunits, the laminin β subunit localizes to all basement membranes throughout development, and secretion of the β subunit requires an α subunit. RNAi inhibition of the β subunit gene or of the other subunit genes causes an embryonic lethality phenotype. Furthermore, a distinctive set of phenotypes is caused by both viable laminin α and β partial loss-of-function mutations. These results show developmental roles for the laminin β subunit, and they provide further genetic evidence for the importance of heterotrimer assembly in vivo.