GATA2 monoallelic expression underlies reduced penetrance in inherited GATA2- mutated MDS/AML

Although familial myelodysplasia and acute myeloid leukemia (MDS/AML) is rare, its true prevalence is likely underestimated due to wide variations in the age of onset, disease latency and outcome between and within families, with some mutation carriers remaining asymptomatic into late adulthood. Reduced penetrance is a notable feature of germline GATA2 p.Thr354Met pedigrees. In this study, we demonstrate that silencing of the wildtype (WT) GATA2 allele discriminates between symptomatic and asymptomatic carriers and is linked with allele-specific differences in DNA methylation and H3K4me3 promotor deposition, providing a molecular explanation for the clinical heterogeneity observed within a GATA2-mutated AML family. Bone marrow (BM) and/or peripheral blood (PB) diagnostic samples were obtained from members of the family with written consent and ethical approval (06/Q0401/31) received in accordance with the declaration of Helsinki. Targeted deep sequencing of 33 genes frequently mutated in MDS/AML was used to determine the secondary mutational repertoire in this family. Quantitative real-time PCR was performed to measure global GATA2 expression with Sanger sequencing used to measure allelic GATA2 expression. Allele-specific differences in GATA2 promoter methylation were assessed by bisulphite cloning and sequencing and allele-specific variations in chromatin deposition were assessed by chromatin-immunoprecipitation (ChIP) using either H3K4me3 or H3K27me3 antibodies. RNA-seq was used to analyze transcriptomic differences between GATA2 monoallelic vs. biallelic groups