CHARACTERIZATION OF MYOCYTE ENHANCER FACTOR-2 (MEF2) EXPRESSION IN B-CELL AND T-CELL - MEF2C IS A B-CELL-RESTRICTED TRANSCRIPTION FACTOR INLYMPHOCYTES

Our studies examined the expression and DNA binding activity of myocyt e enhancer factor 2 (MEF2A-D) transcription factors in lymphopoietic t issues, cell lines, and primary lymphocytes. Our analyses demonstrate that mef2C expression is restricted to B cells within the lymphocyte l ineage. Using in situ hybridization, mefS2C is detected in foci in fet al liver and postnatal thymic medulla, and both mef2B and mef2C are ex pressed in areas of the postnatal spleen and lymph node that also expr ess kappa light chain (C-kappa), a B cell-specific marker. Reverse tra nscriptase-PCR (RT-PCR) analyses demonstrate that all mef2 family memb ers are expressed in B cell lines, and all except mef2C are expressed in T cell lines. Immunoblot analyses of cell lines and primary thymic and splenic lymphocytes show that MEF2C and MEF2D proteins are express ed in B cells and that MEF2D is expressed in T cells; however, MEF2A p rotein is not detected in lymphocytes. Electrophoretic mobility shift assays (EMSA) demonstrate that B cell lines have MEF2C-containing, MEF 2-specific DNA binding complexes whereas T cells do not. Our data is t he first to describe mef2C expression in the lymphocyte lineage, and t his finding suggests possible roles for MEF2C activity in B cell devel opment and function. (C) 1998 Elsevier Science Ltd. All rights reserve d.