Characterization of the hematopoietic stem cell lineage

为了了解血液疾病，如白血病，淋巴瘤和自身免疫性疾病，必须了解造血干细胞（HSC）产生血液谱系的基因表达的完整补充。虽然在成人中，HSC主要存在于骨髓中，但在胚胎中，它们可以追溯到胎儿肝脏、性腺-中肾和胎盘内皮。2011年，我们发表了一篇论文（Dev Dynamics 240：2290），其中我们描述了小鼠发育过程中的胚胎谱系，其特征在于Tbx 4基因的表达，该基因编码“T-box”类的转录因子。这篇论文还描述了一个有用的小鼠品系，称为Tbx 4-Cre，我们已经使用了它，在一个合作的努力中，证明了Roundabout受体在胚胎发生过程中对前肠与体壁的分离至关重要（开发单元24：我们对胚外组织中Tbx 4谱系的分析启发我们推测Tbx 4表达将早期细胞标记为两个区室，每一种都产生内皮，其中只有一种能够产生HSC（“生血内皮”）。如果这一假设是正确的，Tbx 4表达可能是最早已知的标记物之一，可用于分离和纯化将产生生血内皮细胞。因此，今年我们已经开始进行实验来测试这一假设，并产生了数据，证明Tbx 4要么是一个上级的其他常用的标记物的生血内皮细胞，或与这些其他标记物结合时，大大提高了我们的能力，分离这种关键的细胞亚型。我们现在正在进行实验，使用这种新方法来分离和表征在这些细胞中表达的基因。这些数据将使我们能够了解HSC的生物学。

In order to understand diseases of the blood, such as leukemias, lymphomas and autoimmune diseases, it is essential to understand the full complement of gene expression that occurs the hematopoietic stem cells (HSCs) that give rise to the blood lineage. Although in the adult, HSCs are found primarily in the bone marrow, in the embryo they can be traced to the fetal liver, the aorta-gonad-mesonephros and the endothelium of the placenta. In 2011 we published a paper (Dev Dynamics 240:2290) in which we characterized the embryonic lineage during mouse development that is marked by the expression of the Tbx4 gene, which encodes a transcription factor of the "T-box" class. This paper also characterized a useful mouse line, called Tbx4-Cre, that we have since used, in a collaborative effort, to demonstrate that Roundabout receptors are critical for foregut separation from the body wall during embryogenesis (Dev Cell 24: 52) Our analysis of the Tbx4 lineage in the extraembryonic tissue inspired us to speculate that Tbx4 expression marked early cells into two compartments, each giving rise to an endothelium, only one of which is capable of generating HSCs ("hemogenic endothelium"). If this hypothesis is correct, Tbx4 expression may be one of the earliest known markers useful in isolating and purifying cells that will generate hemogenic endothelium. Therefore, this year we have embarked on experiments to test this hypothesis and have generated data that demonstrates that Tbx4 either is a superior to other commonly used markers of hemogenic endothelium or, when combined with these other markers, vastly improves our ability to isolate this crucial cellular subtype. We are now embarking on experiments to use this new approach to isolate and characterize the genes that are expressed in these cells. Such data will allow us to understand the biology of the HSC.