Loss-of-Function and Gain-of-Function Consequences of GATA2 Disease Mutations

• Published in: Blood 2019-11, Vol.134 (Supplement_1), p.2519-2519
• Main Authors: Katsumura, Koichi Ricardo, Liu, Peng, Mehta, Charu, Hewitt, Kyle J, Soukup, Alexandra, Fraga de Andrade, Isabela J, Ranheim, Erik A., Johnson, Kirby D, Bresnick, Emery H
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood-2019-129447

The master regulator of hematopoiesis GATA2 controls generation and function of hematopoietic stem and progenitor cells, and heterozygous GATA2 mutations create a predisposition to develop immunodeficiency, myelodysplasia, and acute myeloid leukemia (Spinner et al. Blood, 2014; Dickinson et al. Blood, 2014; Churpek and Bresnick J. Clin. Invest. 2019). Although mechanisms that trigger the transition of a non-pathogenic GATA2 mutation into overt pathology are enigmatic, a paradigm has arisen in which GATA2 mutations are considered to be loss-of-function. We developed a genetic rescue assay to quantify the function of wild type GATA2 and GATA2 disease mutants when expressed at near-physiological levels in primary progenitor cells and demonstrated that GATA2 disease mutations abrogate certain biological and molecular activities, while enabling others (Katsumura et al., 2018, PNAS). We isolated lineage-negative (Lin-) or Lin-Kit+ cells from fetal liver of mice with a homozygous mutation of the Gata2 -77 enhancer, which downregulates Gata2 expression by ~80%. The mutant progenitor cells are largely defective in erythroid, megakaryocytic and granulocytic differentiation and exhibit a predominant monocytic differentiation fate (Johnson et al., 2015, Science Adv.). We compared GATA2 and GATA2 disease mutant activities in the rescue system using a colony formation assay. GATA2, R307W mutant (in N-finger) and T354M mutant (in DNA-binding C-finger) rescued myeloid colony formation and promoted granulocyte proliferation. Surprisingly, R307W and T354M induced more CFU-GM than GATA2. GATA2 and R307W, but not T354M, rescued BFU-E. These data indicated that GATA2 disease mutations were not strictly inhibitory, and in certain contexts, mutant activities exceeded that of GATA2. To extend these results, we subjected -77+/+ or -77-/- Lin- cells to a short-term ex vivo liquid culture, expressed GATA2, R307W, or T354M and used RNA-seq to elucidate progenitor cell transcriptomes. While -77+/+ Lin- cells generate erythroid and myeloid cells, -77-/- Lin- cells are competent for myeloid, but not erythroid, differentiation. Comparison of -77+/+ and -77-/- cell transcriptomes revealed 3064 differentially expressed genes (>2-fold). 1824 genes were >2-fold higher in -77+/+ cells, and 1240 genes were >2-fold higher in -77-/- cells. GATA2 expression in -77-/- cells activated 834 genes >2-fold and repressed 503 genes >2-fold. 60-65% of these genes overlapped with genes differentially expre