Transgenic GATA1ie3.9int - DAPK2 Mice Exhibit Low-Grade Anemia, Deficient Stress Erythropoiesis, and Compromised Erythroblast Survival.

Death-associated protein kinases (DAPKs) include DAPK-1, DAPK-2, ZIPK and death receptor associated kinase 1 & 2 (DRAK-1 and -2). DAPK-1 and -2 are highly homologous in their shared serine-threonine kinase domains, and calmodulin and phospho-serine regulatory regions. DAPK1 is cytoskeletally associated via ankyrin repeats, and modulates a p19ARF/p53 pathway. DAPK2 is cytoplasmic, less widely distributed, and is expressed predominantly in erythroid cells. Hypothesized effects of DAPK2 on erythroblast formation presently were tested by preparing and studying several independent lines of GATA1ie3.9int-DAPK2 transgenic mice. At steady-state, hematocrits in GATA1ie3.9int-DAPK2 mice were mildly yet significantly decreased (while other lineages were essentially unaffected). Reticulocyte production also was modestly increased, and spleen morphologies were altered. During hemolytic anemia, however, DAPK2 mice exhibited comparably sharp deficiencies in stress erythropoiesis including prolonged decreases in hematocrits (as observed in repeated experiments at varied phenylhydrazine dosing). The basis for this stress-associated erythropoietic defect due to DAPK2 was investigated further in primary bone marrow erythroid progenitor cells ex vivo. A stage-specific defect in erythroblast formation was discovered specifically at Kit^negCD71^highTer119^neg stage. Later stage CD71^highTer119^pos DAPK2-erythroblasts also were somewhat under-represented (but perhaps as a consequence of decreased Kit^negCD71^high pools.) In addition, DAPK2-progenitors gave rise to increased frequencies of Annexin V positive apoptotic erythroblasts. These first-time analyses of DAPK2 function in a relevant primary cell model reveal negative regulation of stage-specific erythroblast pool selectively during stress erythropoiesis, and in part via pro-apoptotic mechanisms.