Modeling genetic modifiers of hematopoiesis with induced pluripotent stem cells

描述（由申请人提供）：了解基因如何相互作用以协调组织发育并导致人类疾病是生物医学的一个基本问题。我们通过对唐氏综合症（DS， 21三体，T21）和造血转录因子GATA-1的研究来解决这个难题。DS引起多种造血异常，包括红细胞增多症、血小板减少症和两种相关的克隆性疾病：短暂性骨髓增生性疾病（TMD）和急性巨核母细胞白血病（AMKL）。后一种疾病是多步骤进展的一部分，需要体细胞GATA1突变导致称为gata -1的83个氨基酸截断的蛋白质。类似的种系突变导致整倍体患者贫血。这些临床观察提出了几个有趣的问题：1)21号染色体（HSA21）上的哪些基因调节造血？2) GATA-1氨基端如何促进造血分化？3)相同的GATA1突变如何在T21患者和非T21患者中引起不同的疾病？4) T21和GATA1突变如何独特地协同作用导致骨髓增生？小鼠模型提供了重要的信息，但不能完全概括人类疾病。我们正在使用人类胎儿肝脏标本和诱导多能干细胞（iPSCs）来研究这些问题，这些干细胞来自DS、TMD和gata1s相关贫血患者。初步研究表明，具有T21和gata -1的iPSCs表现出明显的造血异常，这些异常概括了相关人类疾病的许多方面。现在，我们将对T21、gata -1或两者兼有的iPSCs进行原始（卵黄囊型）和最终（胎儿肝型）造血的系统表征。我们将在iPSCs中操纵候选HSA21基因的表达，以确定导致ds相关血液异常的基因。同时，我们将使用我们的患者来源的iPSCs和mep样细胞系进行研究

DESCRIPTION (provided by applicant): Understanding how genes interact to coordinate tissue development and cause human disease is a fundamental problem in biomedicine. We are drawn to this puzzle through studies of Down syndrome (DS, trisomy 21, T21) and the hematopoietic transcription factor GATA-1. DS causes multiple hematopoietic abnormalities including polycythemia, thrombocytopenia and two related clonal disorders: transient myeloproliferative disorder (TMD) and acute megakaryoblastic leukemia (AMKL). The latter disorders are part of a multi-step progression that requires somatic GATA1 mutations resulting in an 83 amino acid truncated protein termed GATA-1s. Similar germline mutations in GATA1 cause anemia in euploid patients. These clinical observations raise several interesting questions: 1) what genes on chromosome 21 (HSA21) regulate hematopoiesis? 2) How does the GATA-1 amino terminus facilitate hematopoietic differentiation? 3) How do the same GATA1 mutations cause different diseases in patients with and without T21? and 4) How do T21 and GATA1 mutations synergize uniquely to cause myeloproliferation? Murine models have provided important information, but do not fully recapitulate the human diseases. We are studying these problems using human fetal liver specimens and induced pluripotent stem cells (iPSCs) generated from patients with DS, TMD, and GATA1s-associated anemias. Preliminary studies indicate that iPSCs with T21 and GATA-1s exhibit distinct hematopoietic abnormalities that recapitulate many aspects of the associated human disorders. Now, we will perform systematic characterization of primitive (yolk sac-type) and definitive (fetal liver-type) hematopoiesis in iPSCs with T21, GATA-1s or both. We will manipulate the expression of candidate HSA21 genes in iPSCs to identify those responsible for DS-associated blood abnormalities. In parallel, we will use our patient-derived iPSCs and a MEP-like cell line to study how GATA1s mutations dysregulate hematopoietic gene expression and investigate the associated mechanisms through efforts to identify proteins that interact with the GATA-1 amino terminus. Our studies will elucidate how GATA1 and HSA21 genes, separately and together, modulate hematopoiesis. More generally, we hope to create new paradigms in which other hematopoietic diseases can be modeled through creation and manipulation of patient-derived iPSCs.