Cairns Linda A, Moroni Emanuela, Levantini Elena, Giorgetti Alessandra, Klinger Francesca G, Ronzoni Simona, Tatangelo Laura, Tiveron Cecilia, De Felici Massimo, Dolci Susanna, Magli Maria Cristina, Giglioni Barbara, Ottolenghi Sergio
Dipartimento Biotecnologie e Bioscienze, Università Milano-Bicocca-Piazza delle Scienze, 2 Milan, Italy.
Blood. 2003 Dec 1;102(12):3954-62. doi: 10.1182/blood-2003-04-1296. Epub 2003 Aug 7.
The Kit (White) gene encodes the transmembrane receptor of stem cell factor/Kit ligand (KL) and is essential for the normal development/maintenance of pluripotent primordial germ cells (PGCs), hematopoietic stem cells (HSCs), melanoblasts, and some of their descendants. The molecular basis for the transcriptional regulation of Kit during development of these important cell types is unknown. We investigated Kit regulation in hematopoietic cells and PGCs. We identified 6 DNase I hypersensitive sites (HS1-HS6) within the promoter and first intron of the mouse Kit gene and developed mouse lines expressing transgenic green fluorescent protein (GFP) under the control of these regulatory elements. A construct driven by the Kit promoter and including all 6 HS sites is highly expressed during mouse development in Kit+ cells including PGCs and hematopoietic progenitors (erythroid blast-forming units and mixed colony-forming units). In contrast, the Kit promoter alone (comprising HS1) is sufficient to drive low-level GFP expression in PGCs, but unable to function in hematopoietic cells. Hematopoietic expression further requires the addition of the intronproximal HS2 fragment; HS2 also greatly potentiates the activity in PGCs. Thus, HS2 acts as an enhancer integrating transcriptional signals common to 2 developmentally unrelated stem cell/progenitor lineages. Optimal hematopoietic expression further requires HS3-HS6.
Kit（白色）基因编码干细胞因子/Kit配体（KL）的跨膜受体，对于多能原始生殖细胞（PGC）、造血干细胞（HSC）、成黑素细胞及其一些后代的正常发育/维持至关重要。在这些重要细胞类型发育过程中Kit转录调控的分子基础尚不清楚。我们研究了造血细胞和PGC中Kit的调控。我们在小鼠Kit基因的启动子和第一个内含子内鉴定出6个DNA酶I高敏位点（HS1 - HS6），并构建了在这些调控元件控制下表达转基因绿色荧光蛋白（GFP）的小鼠品系。由Kit启动子驱动并包含所有6个HS位点的构建体在小鼠发育过程中在包括PGC和造血祖细胞（红系爆式集落形成单位和混合集落形成单位）的Kit +细胞中高表达。相比之下，单独的Kit启动子（包含HS1）足以在PGC中驱动低水平的GFP表达，但在造血细胞中无功能。造血表达还需要添加内含子近端的HS2片段；HS2也极大地增强了在PGC中的活性。因此，HS2作为一个增强子整合了2个发育上不相关的干细胞/祖细胞谱系共有的转录信号。最佳的造血表达还需要HS3 - HS6。
