Kinetics of E2A basic helix-loop-helix-protein expression during myelopoiesis and primary B cell differentiation.

The DNA-binding factors encoded by the E2A gene, which include the basic helix-loop-helix proteins E12 and E47, are thought to regulate Ig gene expression. In the rat these factors are products of the Pan locus and are referred to as Pan-2 and Pan-1, respectively. To determine when during B cell differentiation Pan (E2A) DNA-binding proteins are first expressed, cells from a newly developed rat long term lymphoid bone marrow culture system were analyzed molecularly and phenotypically using a newly defined anti-Pan mAb. The data indicate that Pan-expressing cells appear in B cell progenitors before the appearance of the CD45R B lineage-associated Ag or microH chain protein. The results also indicate that Pan proteins are present in cells that had undergone D-JH rearrangements. Finally, although Pan (E2A) proteins are present in myeloid precursors, expression is extinguished as differentiation into mature myeloid cells occurs.