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，有必要了解产生血液谱系的造血干细胞（hsc）的全部基因表达。虽然在成人中，造血干细胞主要存在于骨髓中，但在胚胎中，它们可以追溯到胎儿肝脏、主动脉-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以Tbx4基因表达为标志的胚胎谱系，该基因编码“T-box”类转录因子。这篇论文还描述了一个有用的小鼠系，称为Tbx4-Cre，我们已经使用它，在合作的努力中，证明Roundabout受体在胚胎发生期间对前肠与体壁分离至关重要。52)我们对胚胎外组织中Tbx4谱系的分析启发我们推测Tbx4的表达将早期细胞标记为两个区室，每个区室产生内皮，其中只有一个能够产生造血干细胞（“造血内皮”）。如果这一假设是正确的，那么Tbx4的表达可能是已知最早用于分离和纯化产生造血内皮细胞的标志物之一。因此，今年我们开始进行实验来验证这一假设，并产生了数据，表明Tbx4要么优于其他常用的造血内皮标志物，要么与这些其他标志物结合使用，极大地提高了我们分离这一关键细胞亚型的能力。我们现在正着手进行实验，利用这种新方法分离和表征这些细胞中表达的基因。这些数据将使我们能够了解HSC的生物学特性。

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.