Division of Experimental Hematology, Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
Stem Cells. 2012 Feb;30(2):210-21. doi: 10.1002/stem.1002.
The side population phenotype is associated with the Hoechst dye efflux activity of the Abcg2 transporter and identifies hematopoietic stem cells (HSCs) in the bone marrow. This association suggests the direct use of Abcg2 expression to identify adult stem cells in various other organs. We have generated a lineage tracing mouse model based on an allele that coexpresses both Abcg2 and a CreERT2 expression cassette. By crossing these mice with lox-STOP-lox reporter lines (LacZ or YFP), cells that express Abcg2 and their progeny were identified following treatment with tamoxifen (Tam). In the liver and kidney, in which mature cells express Abcg2, reporter gene expression verified the expected physiologic expression pattern of the recombinant allele. Long-term marking of HSCs was seen in multiple peripheral blood lineages from adult mice, demonstrating that Abcg2(+) bone marrow HSCs contribute to steady-state hematopoiesis. Stem cell tracing patterns were seen in the small intestine and in seminiferous tubules in the testis 20 months after Tam treatment, proving that stem cells from these organs express Abcg2. Interstitial cells from skeletal and cardiac muscle were labeled, and some cells were costained with endothelial markers, raising the possibility that these cells may function in the repair response to muscle injury. Altogether, these studies prove that Abcg2 is a stem cell marker for blood, small intestine, testicular germ cells, and possibly for injured skeletal and/or cardiac muscle and provide a new model for studying stem cell activity that does not require transplant-based assays.
侧群表型与 Abcg2 转运蛋白的 Hoechst 染料外排活性相关，并可鉴定骨髓中的造血干细胞（HSCs）。这种关联表明可以直接利用 Abcg2 表达来鉴定各种其他器官中的成人干细胞。我们基于同时表达 Abcg2 和 CreERT2 表达盒的等位基因生成了一种谱系追踪小鼠模型。通过将这些小鼠与lox-STOP-lox 报告基因系（LacZ 或 YFP）杂交，在用他莫昔芬（Tam）处理后，可以鉴定出表达 Abcg2 及其后代的细胞。在肝脏和肾脏中，成熟细胞表达 Abcg2，报告基因表达验证了重组等位基因的预期生理表达模式。在成年小鼠的多个外周血谱系中观察到 HSCs 的长期标记，表明 Abcg2(+) 骨髓 HSCs 有助于稳态造血。在 Tam 处理 20 个月后，在小肠和睾丸的精小管中观察到干细胞追踪模式，证明来自这些器官的干细胞表达 Abcg2。骨骼和心肌的间质细胞被标记，一些细胞与内皮标记物共染色，这提示这些细胞可能在肌肉损伤的修复反应中发挥作用。总之，这些研究证明 Abcg2 是血液、小肠、睾丸生殖细胞的干细胞标记物，并且可能是受损的骨骼和/或心肌的干细胞标记物，并提供了一种新的模型来研究不需要基于移植的测定的干细胞活性。
