Human XIST yeast artificial chromosome transgenes show partial X inactivation center function in mouse embryonic stem cells
Human XIST yeast artificial chromosome transgenes show partial X inactivation center function in mouse embryonic stem cells
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DOI：
10.1073/pnas.96.12.6841
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发表时间：
1999-06-08
影响因子：
11.1
通讯作者：
Avner, P
中科院分区：
文献类型：
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作者：
Heard, E;Mongelard, F;Avner, P
X染色体失活的起始需要X失活中心（XIC）的顺式存在。Xist基因位于人和小鼠的XIC区域内，并且具有仅从雌性体细胞中的失活X染色体表达的独特性质，已知其对于基于小鼠中的靶向缺失的X失活是必需的。虽然我们对小鼠Xist基因的发育调控和功能的理解进展迅速，但对其人类同源物的了解较少。为了解决这个问题，并评估跨物种的保护X失活，一个480 kb的酵母人工染色体含有人类XIST基因被引入到小鼠胚胎干细胞（ES）。人XIST转录物被表达并且可以包被其转录的小鼠常染色体，这表明顺式缔合所需的因子在小鼠ES细胞中是保守的，仅在一部分分化细胞中发现了由于人XIST表达而导致的顺式失活，这表明XIST RNA包被下游的事件最终导致稳定失活可能需要物种特异性因子。人XIST RNA似乎在体外分化前在ES细胞中包被小鼠常染色体，与小鼠Xist基因在未分化ES细胞中的行为相反，在未分化ES细胞中发现不稳定的转录本和没有染色体包被。这可能不仅反映了Xist调控的重要物种差异，而且提供了证据表明，与Xist RNA染色体包被有关的因子可能已经存在于未分化ES细胞中。
Initiation of X chromosome inactivation requires the presence, in cis, of the X inactivation center (XIC), The Xist gene, which lies within the XIC region in both human and mouse and has the unique property of being expressed only from the inactive X chromosome in female somatic cells, is known to be essential for X inactivation based on targeted deletions in the mouse. Although our understanding of the developmental regulation and function of the mouse Xist gene has progressed rapidly, less is known about its human homolog. To address this and to assess the cross-species conservation of X inactivation, a 480-kb yeast artificial chromosome containing the human XIST gene was introduced into mouse embryonic stem (ES) cells. The human XIST transcript was expressed and could coat the mouse autosome from which it was transcribed, indicating that the factors required for cis association are conserved in mouse ES cells, Cis inactivation as a result of human XIST expression was found in only a proportion of differentiated cells, suggesting that the events downstream of XIST RNA coating that culminate in stable inactivation may require species-specific factors. Human XIST RNA appears to coat mouse autosomes in ES cells before in vitro differentiation, in contrast to the behavior of the mouse Xist gene in undifferentiated ES cells, where an unstable transcript and no chromosome coating are found. This may not only reflect important species differences in Xist regulation but also provides evidence that factors implicated in Xist RNA chromosome coating may already be present in undifferentiated ES cells.