Multiple Hemopoietic Defects and Lymphoid Hyperplasia in Mice Lacking the Transcriptional Activation Domain of the c-Rel Protein

The c-rel protooncogene encodes a member of the Rel/nuclear factor (NF)-kappaB family of transcriptional factors. To assess the role of the transcriptional activation domain of c-Rel in vivo, we generated mice expressing a truncated c-Rel (Deltac-Rel) that lacks the COOH-terminal region, but retains a functional Rel homology domain. Mice with an homozygous mutation in the c-rel region encoding the COOH terminus of c-Rel (c-relDeltaCT/DeltaCT) display marked defects in proliferative and immune functions. c-relDeltaCT/DeltaCT animals present histopathological alterations of hemopoietic tissues, such as an enlarged spleen due to lymphoid hyperplasia, extramedullary hematopoiesis, and bone marrow hypoplasia. In older c-relDeltaCT/DeltaCT mice, lymphoid hyperplasia was also detected in lymph nodes, liver, lung, and stomach. These animals present a more severe phenotype than mice lacking the entire c-Rel protein. Thus, in c-relDeltaCT/DeltaCT mice, the lack of c-Rel activity is less efficiently compensated by other NF-kappaB proteins.