Genes required for B cell development.

Mutations in a variety of genes can cause congenital agammaglobulinemia and a failure of B cell development. The currently known genes encode components of the pre-B cell receptor or proteins that are activated by cross-linking of the pre-B cell receptor. Defects in these genes result in a block in B cell differentiation at the pro-B to pre-B cell transition. A patient with a translocation involving a previously unknown gene, LRRC8, demonstrated a block at exactly the same point in B cell differentiation (see the related article beginning on page 1707). It will be interesting to determine whether the protein encoded by this gene interacts with the pre-B cell receptor signal transduction pathway or is involved in a new pathway.