BOTH E12 AND E47 ALLOW COMMITMENT TO THE B-CELL LINEAGE

The E2A gene products, E12 and E47, are required for proper B cell dev elopment. Mice lacking the E2A gene products generate only a very smal l number of 8220(+) cells, which lack immunoglobulin DJ(H) rearrangeme nts. We have now generated mice expressing either E12 or E47. B cell d evelopment in mice expressing E12 but lacking E47 is perturbed at the pro-B cell stage, and these mice lack IgM(+)B220(+) B cells in both bo ne marrow and spleen. IgM(+)B220(+) B cells can be detected, albeit at significantly reduced levels, in the bone marrow and spleen of mice l acking E12. Ectopic expression of both E12 and E47 in a null mutant ba ckground shows that E12 and E47 act in concert to promote B lineage de velopment. Taken together, the data indicate that both E12 and E47 all ow commitment to the B cell lineage and act synergistically to promote B lymphocyte maturation.