We have obtained
cDNA clones coding for the A, B1, and B2 chains of
laminin by screening a cDNA library prepared from mouse
EHS tumor poly(A)RNA in the lambda gt11 expression vector with polyclonal antibody against denatured
laminin. These
cDNA clones were used in combination with a
cDNA clone coding for the alpha 1
type IV collagen chain to study the regulation of genes for these basement membrane
proteins in
retinoic acid-induced differentiating mouse F9
teratocarcinoma cells and in various adult murine tissues. The levels of
mRNA for the
laminin A, B1, and B2 chains and for the alpha 1
type IV collagen chain were increased simultaneously and reached a maximum at almost the same time during the differentiation of F9 cells, suggesting coordinate expression in these cells. The tissue levels of
mRNA encoding for the basement membrane components, however, varied considerably. The highest level of the B1 chain
mRNA was observed in kidney, whereas, the levels of
mRNA for A and B2 chains were highest in heart. Almost the same levels of expression of the alpha 1(IV)
collagen mRNA were found in kidney, lung, and heart. The results indicate that the expression of genes for the basement membrane
proteins is not coordinately regulated in these tissues. It is thus possible that different subunit structures of the
laminin molecule may exist in tissues.