DIFFERENTIATION-DEPENDENT EXPRESSION OF LAMININ-8 (ALPHA-4-BETA-1-GAMMA-1) MESSENGER-RNAS IN MOUSE 3T3-L1 ADIPOCYTES

We report that laminin-8 (alpha 4 beta 1 gamma 1) is the specific isof orm of laminin synthesized in adipocytes. Reverse transcription-polyme rase chain reaction (RT-PCR) of mRNA from mouse 3T3-L1 cells with pair ed primers for alpha 1, alpha 2, alpha 3, alpha 4, alpha 5, beta 1, be ta 2, beta 3, gamma 1 and gamma 2 laminins yielded amplified fragments only for alpha 4, beta 1 and gamma 1. A polyclonal antibody against m ouse laminin-1 (alpha 1 beta 1 gamma 1) precipitated alpha 4 in additi on to beta 1 and gamma 1, while the antibody against a deduced peptide sequence of mouse alpha 4 precipitated beta 1 and gamma 1 in addition to alpha 4. Thus, laminin-8 (alpha 4 beta 1 gamma 1) is the only isof orm expressed in 3T3-L1 cells. Northern blots showed that the levels o f alpha 4, beta 1 and gamma 1 mRNAs increased 2.5-fold during adipose conversion of 3T3-L1 cells. A 1062 bp cDNA fragment cloned by RT-PCR d emonstrated a polymorphism in the mouse alpha 4 gene which would lead to five amino acid changes in the domain G.