GATA1 Mutation in Defective Erythropoiesis

描述（由申请人提供）：GATA 1是红系细胞存活和成熟所需的转录因子。在缺乏GATA 1的情况下，小鼠胚胎在妊娠中期死于贫血。在人类中，GATA 1突变与一系列血液疾病相关，包括先天性红细胞生成不良性贫血和血小板减少症、卟啉症和Diamond-Blackfan贫血（DBA）。在存在21三体的情况下，缺失N-末端的GATA 1突变导致唐氏综合征相关的急性巨核细胞白血病（DS-AMKL）。我们最近证明，GATA 1突变体，它不能结合FOG 1，并与罕见的情况下，红细胞生成不良性贫血，不能结合染色质以相同的方式作为野生型GATA 1。这种不同的染色质结合允许GATA 1促进肥大细胞的形成，而不是红细胞或巨核细胞的发育。以类似的方式，我们最近发现，GATA 1分子，缺乏N-末端激活结构域，在DBA和DS-AMKL，也不能结合染色质的全长GATA 1相同的方式。感兴趣的是，未被GATA 1正确结合或调节的基因包括关键的红细胞基因，如Alas 2，Slc 4a 1和Klf 1（EKLF）。在这项资助中，我们将精确地定义红细胞发育中对GATA 1 N-末端的要求。我们的目标是发现GATA 1突变如何导致GATA 1表达而不是全长蛋白质导致红系缺陷和先天性贫血，包括DBA。我们的总体假设是，减少染色质结合和异常的基因调控GATA 1导致受损的规格和终末分化的红细胞。我们的目标是：1）将GATA 1的染色质占有率与原代GATA 1敲入红系祖细胞中的基因表达缺陷相关联，以鉴定失调的关键直接靶基因; 2）研究GATA 1突变对红系特化和分化的影响; 3）确定N末端的缺失是否减少了与必需辅因子的相互作用，进而影响其染色质占有率。本提案中描述的研究将大大扩展我们对GATA 1 N-末端缺失如何改变红细胞生成的认识，并将使先天性贫血和DS-AMKL患者受益。

DESCRIPTION (provided by applicant): GATA1 is a transcription factor that is required for survival and maturation of erythroid cells. In the absence of GATA1, mouse embryos die from anemia in mid-gestation. In humans, GATA1 mutations are associated with a spectrum of blood disorders, including congenital dyserythropoietic anemia and thrombocytopenia, porphyria, and Diamond-Blackfan Anemia (DBA). In the presence of trisomy 21, GATA1 mutations that delete the N- terminus lead to Down syndrome associated Acute Megakaryoblastic Leukemia (DS-AMKL). We recently demonstrated that a GATA1 mutant, which fails to bind FOG1 and is associated with rare cases of cases of dyserythropoietic anemia, fails to bind chromatin in the same manner as wild-type GATA1. This differential chromatin binding allows GATA1 to promote mast cell formation instead of red cell or megakaryocyte development. In a similar fashion, we have recently discovered that GATA1 molecules that lack the N-terminal activation domain, seen in both DBA and DS-AMKL, also fail to bind chromatin in the same way as full-length GATA1. Of interest, genes that are not properly bound or regulated by GATA1s include critical red cell genes such as Alas2, Slc4a1, and Klf1 (EKLF). In this grant, we will precisely define the requirement for the N- terminus of GATA1 in red cell development. Our aim is to discover how the GATA1 mutations that lead to expression of GATA1s in place of the full-length protein cause defects in the erythroid lineage and congenital anemia, including DBA. Our overarching hypothesis is that the reduced chromatin binding and aberrant gene regulation by GATA1s leads to impaired specification and terminal differentiation of red blood cells. Our aims are to: 1 Correlate chromatin occupancy of GATA1s with gene expression defects in primary GATA1s knock-in erythroid progenitor cells to identify key direct target genes that are dysregulated; 2) Investigate the consequences of the GATA1s mutation on erythroid specification and differentiation; and 3) Determine if loss of the N-terminus reduces the interaction with essential cofactors and in turn affects their chromatin occupancy. The research described in this proposal will greatly expand our insights into how loss of the N-terminus of GATA1 alters erythropoiesis and will benefit patients with congenital anemia and DS-AMKL.