Cerisoli Francesco, Cassinelli Letizia, Lamorte Giuseppe, Citterio Stefania, Bertolotti Francesca, Magli Maria Cristina, Ottolenghi Sergio
Institute of Biomedical Technologies, National Council of Research, Pisa, Italy.
Haematologica. 2009 Mar;94(3):318-25. doi: 10.3324/haematol.13689. Epub 2009 Jan 30.
The transcriptional regulation of stem cell genes is still poorly understood. Kit, encoding the stem cell factor receptor, is a pivotal molecule for multiple types of stem/progenitor cells. We previously generated mouse lines expressing transgenic green fluorescent protein under the control of Kit promoter/first intron regulatory elements, and we demonstrated expression in hematopoietic progenitors.
In the present work we investigated whether the transgene is also expressed in hematopoietic stem cells of adult bone marrow and fetal liver. To this purpose, we tested, in long-term repopulating assays, cell fractions expressing different levels of green fluorescent protein within Kit-positive or SLAM-selected populations.
The experiments demonstrated transgene expression in both fetal and adult hematopoietic stem cells and indicated that the transgene is transcribed at distinctly lower levels in hematopoietic stem cells than in pluripotent and committed progenitors.
These results, together with previous data, show that a limited subset of DNA sequences drives gene expression in number of stem cell types (hematopoietic stem cells, primordial germ cells, cardiac stem cells). Additionally, our results might help to further improve high level purification of hematopoietic stem cells for experimental purposes. Finally, as the Kit/green fluorescent protein transgene is expressed in multiple stem cell types, our transgenic model provides powerful in vivo system to track these cells during development and tissue regeneration.
干细胞基因的转录调控仍知之甚少。Kit编码干细胞因子受体，是多种类型干细胞/祖细胞的关键分子。我们之前构建了在Kit启动子/第一内含子调控元件控制下表达转基因绿色荧光蛋白的小鼠品系，并证明其在造血祖细胞中表达。
在本研究中，我们调查了该转基因是否也在成年骨髓和胎儿肝脏的造血干细胞中表达。为此，我们在长期重建实验中测试了Kit阳性或SLAM选择群体中表达不同水平绿色荧光蛋白的细胞组分。
实验证明该转基因在胎儿和成年造血干细胞中均有表达，并表明该转基因在造血干细胞中的转录水平明显低于多能祖细胞和定向祖细胞。
这些结果与之前的数据一起表明，有限的DNA序列子集可驱动多种干细胞类型（造血干细胞、原始生殖细胞、心脏干细胞）中的基因表达。此外，我们的结果可能有助于进一步改进用于实验目的的造血干细胞的高效纯化。最后，由于Kit/绿色荧光蛋白转基因在多种干细胞类型中表达，我们的转基因模型提供了一个强大的体内系统，用于在发育和组织再生过程中追踪这些细胞。
