The Ikaros gene is required for the development of all lymphoid lineages

The Ikaros gene encodes a family of early hematopoietic- and lymphocyte-restricted transcription factors. Mice homozygous for a germline mutation in the Ikaros DNA-binding domain lack not only T and B lymphocytes and natural killer cells but also their earliest defined progenitors. In contrast, the erythroid and myeloid lineages were intact in these mutant mice. We propose that Ikaros promotes differentiation of pluripotential hematopoietic stem cell(s) into the lymphocyte pathways. In the absence of a functional Ikaros gene, these stem cells are exclusively diverted into the erythroid and myeloid lineages.