Cytogenetic and molecular studies on a recombinant human X chromosome: implications for the spreading of X chromosome inactivation.
Cytogenetic and molecular studies on a recombinant human X chromosome: implications for the spreading of X chromosome inactivation.
复制标题
重组人 X 染色体的细胞遗传学和分子研究：对 X 染色体失活传播的影响。
DOI：
10.1073/pnas.84.14.4954
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发表时间：
1987
影响因子：
11.1
通讯作者：
Shapiro,LJ
中科院分区：
文献类型：
--
作者：
Mohandas,T;Geller,RL;Yen,PH;Rosendorff,J;Bernstein,R;Yoshida,A;Shapiro,LJ
在一个家系中鉴定了一个人类X染色体的着丝粒周围倒位和一个从倒位内交换而来的重组X染色体[rec(X)]。REC(X)具有Xq26.3-Xqter片段的重复和Xp22.3-Xpter的缺失，并被解释为Xqter-Xq26.3：：Xp22.3-Xqter。为了鉴定rec(X)染色体，用多个X染色体探针对重排的X染色体携带者的基因组DNA进行了剂量印迹。结果表明，4D8、Hx120A、DX13和St14探针与长臂末端的匿名序列以及葡萄糖-6-磷酸脱氢酶(G6PD)基因座在REC(X)上重复。构建了保持rec(X)活性或非活性状态的鼠-人细胞杂交体。对X染色体远端短臂标记的分析表明，rec(X)保留了类固醇硫酸酯酶(STS)和细胞表面抗原12E7(MIC2)的基因座，但不保留假常染色体序列113D。这些分子研究证实，rec(X)不出所料是一条复制缺陷染色体。在细胞杂交体中，STS和MIC2(通常逃脱X染色体失活)从rec(X)中表达，而G6PD则不表达。因此，在rec(X)中，X染色体失活已经通过STS和MIC2传播，使这些基因座不受影响，并在人类X染色体的q26.3-QTER区域缺乏失活中心的情况下使G6PD失活。失活的传播机制似乎是以序列特异性的方式运作的。或者，STS和MIC2最初可能已经失活，但不能保持在非激活状态。
A pericentric inversion of a human X chromosome and a recombinant X chromosome [rec(X)] derived from crossing-over within the inversion was identified in a family. The rec(X) had a duplication of the segment Xq26.3----Xqter and a deletion of Xp22.3----Xpter and was interpreted to be Xqter----Xq26.3::Xp22.3----Xqter. To characterize the rec(X) chromosome, dosage blots were done on genomic DNA from carriers of this rearranged X chromosome using a number of X chromosome probes. Results showed that anonymous sequences from the distal end of the long arm to which probes 4D8, Hx120A, DX13, and St14 bind as well as the locus for glucose-6-phosphate dehydrogenase (G6PD) were duplicated on the rec(X). Mouse-human cell hybrids were constructed that retained the rec(X) in the active or inactive state. Analyses of these hybrid clones for markers from the distal short arm of the X chromosome showed that the rec(X) retained the loci for steroid sulfatase (STS) and the cell surface antigen 12E7 (MIC2); but not the pseudoautosomal sequence 113D. These molecular studies confirm that the rec(X) is a duplication-deficiency chromosome as expected. In the inactive state in cell hybrids, STS and MIC2 (which usually escape X chromosome inactivation) were expressed from the rec(X), whereas G6PD was not. Therefore, in the rec(X) X chromosome inactivation has spread through STS and MIC2 leaving these loci unaffected and has inactivated G6PD in the absence of an inactivation center in the q26.3----qter region of the human X chromosome. The mechanism of spreading of inactivation appears to operate in a sequence-specific fashion. Alternatively, STS and MIC2 may have undergone inactivation initially but could not be maintained in an inactive state.