Altered functional balance of Gfi-1 and Gfi-1b as an alternative cause of reticular dysgenesis?

Reticular dysgenesis (RD) is a rare form of severe combined immunodeficiency (SCID). The underlying genetic defect for most cases of RD was recently identified in the gene encoding adenylate kinase 2 (AK2). However, rare patients with RD and no mutations in AK2 exist, suggesting that mutations in other genes may also cause RD. Although rare, RD has a devastating presentation involving severe neutropenia and T cell lymphopenia, in addition to life non-threatening, but still disabling sensori-neural deafness. An identical phenotype is observed in mice deficient for growth factor independence-1 (Gfi-1) or transgenic for Gfi-1b, related nucleoproteins with opposing, antagonizing roles in development. We hypothesize that a genetically based, altered functional balance between these two factors may be an alternative cause of RD.