Regulation of B lymphocyte development by the truncated immunoglobulin heavy chain protein Dμ

The development of B lymphocytes from progenitor cells is dependent on the expression of a pre-B cell-specific receptor made up by a CL heavy chain associated with the surrogate light chains, immunoglobulin (Ig)alpha, and Ig beta. A variant pre-B cell receptor can be formed in which the mu heavy chain is exchanged for a truncated mu chain denoted D mu. To investigate the role of this receptor in the development of B cells, we have generated transgenic mice that express the D mu protein in cells of the B lineage. Analysis of these mice reveal that D mu expression leads to a partial block in B cell development at the early pre-B cell stage, probably by inhibiting V-H to D(H)J(H) rearrangement. Furthermore, we provide evidence that D mu induces V-L to J(L) rearrangements.