Department of Biological Science, Florida State University, Tallahassee, Florida, United States of America.
PLoS One. 2011 Apr 22;6(4):e18969. doi: 10.1371/journal.pone.0018969.
Macrosatellites are some of the most polymorphic regions of the human genome, yet many remain uncharacterized despite the association of some arrays with disease susceptibility. This study sought to explore the polymorphic nature of the X-linked macrosatellite DXZ4. Four aspects of DXZ4 were explored in detail, including tandem repeat copy number variation, array instability, monomer sequence polymorphism and array expression. DXZ4 arrays contained between 12 and 100 3.0 kb repeat units with an average array containing 57. Monomers were confirmed to be arranged in uninterrupted tandem arrays by restriction digest analysis and extended fiber FISH, and therefore DXZ4 encompasses 36-288 kb of Xq23. Transmission of DXZ4 through three generations in three families displayed a high degree of meiotic instability (8.3%), consistent with other macrosatellite arrays, further highlighting the unstable nature of these sequences in the human genome. Subcloning and sequencing of complete DXZ4 monomers identified numerous single nucleotide polymorphisms and alleles for the three microsatellite repeats located within each monomer. Pairwise comparisons of DXZ4 monomer sequences revealed that repeat units from an array are more similar to one another than those originating from different arrays. RNA fluorescence in situ hybridization revealed significant variation in DXZ4 expression both within and between cell lines. DXZ4 transcripts could be detected originiating from both the active and inactive X chromosome. Expression levels of DXZ4 varied significantly between males, but did not relate to the size of the array, nor did inheritance of the same array result in similar expression levels. Collectively, these studies provide considerable insight into the polymorphic nature of DXZ4, further highlighting the instability and variation potential of macrosatellites in the human genome.
大片段卫星是人类基因组中最具多态性的区域之一，但尽管一些阵列与疾病易感性有关，许多仍然没有得到描述。本研究旨在探索 X 连锁大片段卫星 DXZ4 的多态性。详细探讨了 DXZ4 的四个方面，包括串联重复拷贝数变异、阵列不稳定性、单体序列多态性和阵列表达。DXZ4 阵列包含 12 到 100 个 3.0 kb 重复单元，平均阵列包含 57 个。通过限制酶消化分析和扩展纤维 FISH 证实单体排列在不间断的串联阵列中，因此 DXZ4 包含 36-288 kb 的 Xq23。三个家族三代传递的 DXZ4 表现出高度的减数分裂不稳定性（8.3%），与其他大片段卫星阵列一致，进一步突出了这些序列在人类基因组中的不稳定性质。对完整 DXZ4 单体的亚克隆和测序确定了位于每个单体内的三个微卫星重复的许多单核苷酸多态性和等位基因。DXZ4 单体序列的成对比较表明，来自一个阵列的重复单元彼此之间比来自不同阵列的重复单元更为相似。DXZ4 表达的 RNA 荧光原位杂交显示了细胞系内和细胞系之间的显著差异。可以从活性和非活性 X 染色体上检测到 DXZ4 转录本。DXZ4 的表达水平在男性之间存在显著差异，但与阵列的大小无关，也与相同阵列的遗传无关，导致相似的表达水平。总的来说，这些研究为 DXZ4 的多态性提供了重要的见解，进一步突出了人类基因组中大片段卫星的不稳定性和变异潜力。
