Differentiation-dependent expression of laminin-8 (α4β1γ1) mRNAs in mouse 3T3-L1 adipocytes☆

Abstract We report that laminin-8 (α4β1γ1) is the specific isoform of laminin synthesized in adipocytes. Reverse transcription-polymerase chain reaction (RT-PCR) of mRNA from mouse 3T3-L1 cells with paired primers for α1, α2, α3, α4, α5, β1, β2, β3, γ1 and γ2 laminins yielded amplified fragments only for α4, β1 and γ1. A polyclonal antibody against mouse laminin-1 (α1β1γ1) precipitated α4 in addition to β1 and γ1, while the antibody against a deduced peptide sequence of mouse α4 precipitated β1 and γ1 in addition to α4. Thus, laminin-8 (α4β1γ1) is the only isoform expressed in 3T3-L1 cells. Northern blots showed that the levels of α4, β1 and γ1 mRNAs increased 2.5-fold during adipose conversion of 3T3-L1 cells. A 1062 bp cDNA fragment cloned by RT-PCR demonstrated a polymorphism in the mouse α4 gene which would lead to five amino acid changes in the domain G.