A crucial role of the ubiquitously expressed transcription factor Sp1 at early stages of hematopoietic specification [array]

Mammalian development is regulated by the interplay of tissue-specific and ubiquitously expressed transcription factors, such as Sp1. Sp1 knock-out mice die in utero with multiple phenotypic aberrations, but the underlying molecular mechanism of this differentiation failure has been elusive. Here we used conditional knock-out mice as well as the differentiation of mouse ES cells as a model to address this issue. To this end we examined differentiation potential, global gene expression patterns and Sp1 target regions in Sp1 wild-type and deficient cells representing different stages of hematopoiesis. Sp1-/- cells progress through most embryonic stages of blood cell development but cannot complete terminal differentiation. For most Sp1 target and non-target genes, gene expression is unaffected by Sp1 inactivation. However, Cdx and multiple Hox genes are stage-specific targets of Sp1 and are down-regulated at an early stage. As a consequence, expression of genes involved in hematopoietic specification are progressively deregulated, highlighting the regulatory hierarchy of hematopoietic specification. Our work demonstrates that the early absence of active Sp1 sets a cascade in motion that culminates in a failure of terminal hematopoietic differentiation and emphasizes the role of ubiquitously expressed transcription factors for tissue-specific gene regulation. Microarray expression data, 16 arrays with 2 independent biological replicates (8 arrays wildtype and 8 arrays knock out) obtained from differentiation of ES cells to study the transcription factor Sp1 activity at early stages of early hematopoietic specification.

哺乳动物发育的调控依赖于组织特异性转录因子（tissue-specific transcription factors）与泛在表达转录因子（ubiquitously expressed transcription factors）之间的相互作用，以转录因子Sp1为例。Sp1基因敲除（knock-out）小鼠会在子宫内死亡，并伴随多种表型异常，但该分化失败背后的分子机制始终不明。本研究使用条件性基因敲除（conditional knock-out）小鼠与小鼠胚胎干细胞（embryonic stem cells，简称ES细胞）分化模型来解答这一科学问题。为此，我们针对造血过程不同阶段的Sp1野生型（wild-type）与基因缺陷型细胞，检测了其分化潜能、全基因表达谱及Sp1靶区域。Sp1纯合敲除细胞可完成血细胞发育的多数胚胎阶段，但无法完成终末分化。对于绝大多数Sp1靶基因与非靶基因而言，其表达不受Sp1失活的影响。但Cdx基因与多个同源框（Hox）基因属于Sp1的阶段特异性靶基因，会在早期阶段被下调。因此，参与造血特化（hematopoietic specification）的基因表达会逐渐失调，凸显出造血特化的调控层级关系。本研究表明，早期活性Sp1的缺失会触发级联反应（cascade），最终导致造血终末分化失败，同时强调了泛在表达转录因子在组织特异性基因调控中的重要作用。本数据集包含源自ES细胞分化过程的基因芯片（microarray）表达数据：共16张芯片，设置2次独立生物学重复（biological replicates），其中8张为野生型芯片，8张为基因敲除型芯片，用于研究造血特化早期阶段转录因子Sp1的活性调控机制。