Maintenance of the mammalian inactive X chromosome

哺乳动物失活 X 染色体的维持

• 批准号: 13672372
• 负责人: YOSHIDA Ikuya
• 金额: $ 2.3万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13672372/
• 关键词: inactive X chromosome; heterochromatinization; embryonal carcinoma cells; mouse; histone acetylation; Xist RNA; late DNA replication; macroH2A1.2; X染色体; RNA

The mouse embryonal carcinoma cell line MC12 carries two X chromosomes, one of which replicates late in S phase and shares properties with the normal inactive X chromosome, and is therefore considered to be inactivated. Since the hypoxanthine phosphoribosyl transferase (HPRT) gene on the active X chromosome is mutated (hprt^-), MC12 cells lack HPRT activity. After subjecting MC12 cells to selection in HAT medium, however, a number of HAT-resistant clones (HAT^R) appeared. The high frequency of HAT resistance (3.18x10^<-4>) suggested reactivation of hprt^+ on the inactive X chromosome rather than reversion of hprt^-. Consistent with this view, cytological analyses showed that the reactivation occurred over the length of the inactive X chromosome in 11 out of 20 HAT^R clones isolated. The remaining 9 clones retained a normal heterochromatic inactive X chromosome. The spontaneous reactivation rate of the hprt^+ on the inactive X chromosome was relatively high (1.34x10^<-6>) and comparable to that observed for Xist-deleted somatic cells (Csankovszki et al., 2001), suggesting that the inactivated state is poorly maintained in MC12 cells.

小鼠胚胎癌细胞系MC 12携带两条X染色体，其中一条在S期晚期复制，并与正常的失活X染色体共享特性，因此被认为是失活的。由于活性X染色体上的次黄嘌呤磷酸核糖转移酶（HPRT）基因发生突变（hprt^-），MC 12细胞缺乏HPRT活性。然而，在HAT培养基中对MC 12细胞进行选择后，出现了许多HAT抗性克隆（HAT^R）。HAT抗性的高频率（3.18 × 10 ^-3<-4>）表明失活X染色体上的hprt^+被重新激活，而不是hprt^-的逆转。与此观点相一致的是，细胞学分析表明，在分离的20个HAT^R克隆中，有11个在失活的X染色体上发生了再激活。其余9个克隆保留了正常的异染色质失活X染色体。失活X染色体上hprt^+的自发再激活率相对较高（1.34 × 10 ^<-6>），与Xist缺失体细胞的观察结果相当（Csankovszki et al.，2001），表明失活状态在MC 12细胞中维持得很差。

项目成果

YOSHIDA, Ikuuya: "Spontaneous Reactivation of the Inactive X chromosome in Mouse Embryonal Carcinoma Cells"Cytogenet and Genome Research. in press. (2003)

YOSHIDA, Ikuuya：“小鼠胚胎癌细胞中失活 X 染色体的自发再激活”细胞遗传学和基因组研究。

I.Yoshida: "Spontaneous reactivation of the inactive Xchromoseme in mouse emoryonal carcinoma cells"Cytogenetic and Genome Research. (in press).

I.Yoshida：“小鼠胚胎癌细胞中非活性X染色体的自发再激活”细胞遗传学和基因组研究。

I.Yoshida: "Spontaneous reactivation of the inactive X chromosome in mouse embryonal carcinoma cells"Cytogenet and Genome Research. (in press).

I.Yoshida：“小鼠胚胎癌细胞中失活的 X 染色体的自发再激活”细胞遗传学和基因组研究。