Spherocytic Hemolytic Anemia Caused by Disruption of GATA1-FOG1 Interaction.

Abstract 775

Transcription factor GATA1 is essential for erythroid/megakaryocytic cell differentiation. Gene ablation studies have revealed that GATA1 plays essential roles in the differentiation of erythroid and megakaryocytic lineages. Two functional zinc finger domains have been identified within the GATA1 molecule, and N-terminal finger (NF) is required for the association with cofactor FOG1 and also DNA recognition. Several substitution mutations in the GATA1 NF that diminish association of GATA1-FOG1 have been identified in patients with thrombocytopenia and anemia. We previously established a genetically engineered mouse model, which mimics a human disease X-linked thrombocytopenia with inherited GATA1 mutation, utilizing the transgenic complementation rescue approach. GATA1-deficient mice were successfully rescued from embryonic lethality by excess expression of mutant GATA1 (GATA1^V205G) and showed severe thrombocytopenia with impaired cytoplasmic maturation of megakaryocytes resembling the human disease. However, these mice did not show dyserythropoietic phenotype except for the attenuated erythropoiesis under stress conditions. On the contrary, GATA1-deficient mice rescued by transgenic expression of GATA1^V205G at the level comparable with that of the endogenous GATA1 hardly survived though the postnatal stage. Accordingly, we analyzed rescued embryos during perinatal period. At 18.5 embryonic days, expected number of rescued embryos survived although they showed macroscopic anemia, indicating that embryonic erythropoiesis was not fully sustained by transgenic expression of GATA1^V205G at the endogenous level. Surprisingly, rescued newborns suffered from severe anemia and jaundice. Serum indirect bilirubin level was significantly elevated and circulating erythrocytes showed abnormal morphology characterized as spherocytes by means of scanning electron microscopic observation. The expressions of Band3 gene/protein were strikingly diminished in the rescued erythroid cells, while expression of the other membrane related genes varied in individuals. Thus, these results indicate that hemolytic event associated with the lack of Band3 and dysfunction of erythrocyte membrane is induced during perinatal period, and GATA1 maintains the erythroid membrane homeostasis through interaction with FOG1.