Effect of somatic STAG2 mutations on clonal hematopoiesis in GATA2 associated familial myelodysplastic syndromes

GATA2单倍体功能不全是儿童骨髓增生异常综合征(MDS)最常见的诱因种系缺陷，并与进展为急性髓系白血病(AML)的高风险相关。GATA2缺陷患者通常在造血干细胞的关键调节因子上获得额外的体细胞突变，这可能会加速疾病的进展。对先导队列中GATA2缺陷患者的突变分析显示，以前未知的粘附素亚单位STAG2突变显着丰富。目前尚不清楚STAG2突变对GATA2缺陷患者疾病进展的生物学机制和影响。因此，我们将在更大的队列中对GATA2缺乏症患者的骨髓样本进行深度靶向测序，以确定获得性体细胞突变并表征系列样本中的克隆动力学。通过将这些数据与临床病理变量相关联，我们将调查获得性STAG2突变如何影响临床表型。为了进一步明确STAG2突变在造血干细胞功能中的作用，我们将研究STAG2缺陷对Gata2单倍体缺陷小鼠的造血干细胞自我更新能力和谱系特异性分化的影响。此外，我们将在同基因髓系白血病细胞系模型中检测STAG2缺失和GATA2单倍体缺陷对整体转录、染色质可及性和GATA2靶基因占有率的联合影响，以阐明促进GATA2缺陷患者发生STAG2突变的潜在机制。研究GATA2和STAG2等关键造血调控基因协同突变的病理机制及其对疾病进展的影响，不仅对于为家族性MDS综合征患者提供最好的医疗服务至关重要，而且对于更好地了解髓系恶性肿瘤的克隆性扩张是如何演变的也是至关重要的。

GATA2 haploinsufficiency presents the most common predisposing germline defect in myeloid dysplastic syndrome (MDS) in children and is associated with a high risk of progression to acute myeloid leukemia (AML). GATA2 deficient patients often acquire additional somatic mutations in key regulators of hematopoietic stem cells which can accelerate disease progression. Mutational analysis of GATA2 deficient patients in a pilot cohort revealed a previously unknown significant enrichment of mutations in the cohesin-subunit STAG2. Biological mechanisms and effects of STAG2 mutations on disease progression in GATA2 deficient patients are currently unknown. Therefore, we will use deep targeted sequencing of bone marrow samples of patients with GATA2 deficiency syndrome in a larger cohort to identify acquired somatic mutations and to characterize clonal dynamics in serial samples. By correlating these data with clinicopathologic variables we will investigate how acquired STAG2 mutations affect the clinical phenotype. To further define the role of STAG2 mutations in hematopoietic stem cell function we will study the impact of Stag2 deficiency on hematopoietic stem cell self-renewal capacity and lineage-specific differentiation in Gata2 haploinsufficient mice. Moreover, we will determine combinatorial effects of STAG2 loss and GATA2 haploinsufficiency on global transcription, chromatin accessibility and GATA2 target gene occupancy in an isogenic myeloid leukemia cell line model to elucidate the underlying mechanisms that promote the occurrence of STAG2 mutations in GATA2 deficient patients. The investigation of pathomechanistic principles of cooperative mutations in key hematopoietic regulatory genes such as GATA2 and STAG2 and their influence on disease progression is not only essential to provide the best medical care for patients with familial MDS syndromes but also to gain a better understanding of how clonal expansion evolves in myeloid malignancies in general.