Sánchez M, Göttgens B, Sinclair A M, Stanley M, Begley C G, Hunter S, Green A R
University of Cambridge, Department of Haematology, MRC Centre, Hills Road, Cambridge CB2 2QH, UK.
Development. 1999 Sep;126(17):3891-904. doi: 10.1242/dev.126.17.3891.
The SCL gene encodes a basic helix-loop-helix transcription factor which is expressed in early haematopoietic progenitors throughout ontogeny and is essential for the normal development of blood and blood vessels. Transgenic studies have characterised spatially distinct 5' enhancers which direct lacZ expression to subdomains of the normal SCL expression pattern, but the same elements failed to produce appropriate haematopoietic expression. We now describe an SCL 3' enhancer with unique properties. It directed lacZ expression in transgenic mice to extra-embryonic mesoderm and subsequently to both endothelial cells and to a subset of blood cells at multiple sites of embryonic haematopoiesis including the yolk sac, para-aortic splanchnopleura and AGM region. The 3' enhancer also targeted expression to haematopoietic progenitors in both foetal liver and adult bone marrow. Purified lacZ(+ )cells were highly enriched for clonogenic myeloid and erythroid progenitors as well as day-12 spleen colony forming units (CFU-S). Within the total gated population from bone marrow, 95% of the myeloid and 90% of the erythroid colony-forming cells were contained in the lacZ(+) fraction, as were 98% of the CFU-S. Activation of the enhancer did not require SCL protein. On the contrary, transgene expression in yolk sacs was markedly increased in an SCL-/- background, suggesting that SCL is subject to negative autoregulation. Alternatively the SCL-/- environment may alter differentiation of extra-embryonic mesoderm and result in an increased number of cells capable of expressing high levels of the transgene. Our data represents the first description of an enhancer that integrates information necessary for expression in developing endothelium and early haematopoietic progenitors at distinct times and sites throughout ontogeny. This enhancer provides a potent tool for the manipulation of haematopoiesis and vasculogenesis in vivo.
SCL基因编码一种碱性螺旋-环-螺旋转录因子，该因子在个体发育过程中的早期造血祖细胞中表达，对血液和血管的正常发育至关重要。转基因研究已鉴定出空间上不同的5'增强子，这些增强子将lacZ表达导向正常SCL表达模式的亚结构域，但相同的元件未能产生适当的造血表达。我们现在描述一种具有独特性质的SCL 3'增强子。它在转基因小鼠中引导lacZ表达至胚外中胚层，随后在胚胎造血的多个部位，包括卵黄囊、主动脉旁脏壁中胚层和AGM区，导向内皮细胞和一部分血细胞。3'增强子还将表达靶向至胎儿肝脏和成年骨髓中的造血祖细胞。纯化的lacZ(+)细胞高度富集了克隆性髓系和红系祖细胞以及第12天的脾集落形成单位（CFU-S）。在来自骨髓的总门控群体中，95%的髓系和90%的红系集落形成细胞包含在lacZ(+)部分中，CFU-S的这一比例为98%。增强子的激活不需要SCL蛋白。相反，在SCL-/-背景下，卵黄囊中的转基因表达显著增加，这表明SCL受到负向自动调节。或者，SCL-/-环境可能会改变胚外中胚层的分化，并导致能够表达高水平转基因的细胞数量增加。我们的数据首次描述了一种增强子，它整合了在个体发育过程中不同时间和部位在发育中的内皮细胞和早期造血祖细胞中表达所需的信息。这种增强子为体内造血和血管生成的操纵提供了一种有力工具。
