小鼠皮肤干细胞染色体非随机分配方式的研究

目的：以小鼠皮肤干细胞为研究对象，对无论干细胞分裂多少次的一组DNA“永生化”链，能持续存在于干细胞基因组中的这一假说进行验证。方法：利用溴脱氧尿嘧啶核苷（BrdU）掺入法，检测发育期和成年期标记的小鼠皮肤BrdU阳性细胞存在情况。结果：免疫组化结果表明，BrdU标记停止后24h，发育期和成年期标记的小鼠皮肤上皮细胞均为阳性，阳性部位为细胞核，7天后仍为阳性。90天后发育期小鼠皮肤上皮细胞中仍有少数阳性细胞，它们主要存在于毛囊的隆突部位，另有少数阳性细胞散落在基底层。但成年期小鼠30天后皮肤BrdU阳性上皮细胞已全部转为阴性。结论：本实验结果证实，小鼠皮肤干细胞中存在DNA永生化链，其染色体发生了非随机分配。

The study of nonrandom segregation of mitotic chromosomes in mouse skin stem cells

Objective:It was proposec that a set of "immortal strands" persists in stem cells through successive cell divisions. In this study we tested this hypothesis in the mouse epidermal stem cells. Methods: DNA label retaining methods and immunolabelling were used to chase the changes of BrdU positive cells in iurenile and adult mouse skin tissue. Results: During the chase period, immunolabelling showed that an extremely high percentage of keratinocytes of juvenile and adult mice incorporated the BrdU 24h after final BrdU labeling confirming that these cells were in cycling, and most keratinocytes are BrdU positive 7 days later. some keratinocytes of mice BrdU labeled during juvenile period were BrdU positive even 90 days later. Most of these cells were within the bulge of hair follicle and some scattered in the basal layer of skin. In contrast, all keratinocytes of mice labeled during adult period were completely BrdU negative 30 days after the final BrdU injection. Conclusion: We confirmed both the existence of immortal DNA strands and the cosegregation of chromosomes that bear them in mouse epidermal stem cells.