在用一种具有单染色体分辨率的CO-FISH方法所进行的实验中，Yukiko Yamashita 和 Swathi Yadlapalli发现，性染色体（而不是常染色体）的姐妹染色单体在果蝇雄性生殖细胞 (GSCs) 的非对称细胞分裂过程中是被非随机分离的。姐妹染色单体分离在GSC过度增殖过程中和在“去分化的”GSCs中被随机化。鉴于这些发现，作者提出：非随机姐妹染色单体分离不大可能像以前人们所提出的那样保护所谓的“不朽链”（immortal strand），以避免发生由复制诱导的突变。(生物谷Bioon.com)
生物谷推荐英文摘要：
Nature doi:10.1038/nature12106
Chromosome-specific nonrandom sister chromatid segregation during stem-cell division
Swathi Yadlapalli & Yukiko M.Yamashita
Adult stem cells undergo asymmetric cell division to self-renew and give rise to differentiated cells that comprise mature tissue. Sister chromatids may be distinguished and segregated nonrandomly in asymmetrically dividing stem cells, although the underlying mechanism and the purpose it may serve remain elusive. Here we develop the CO-FISH (chromosome orientation fluorescence in situ hybridization) technique with single-chromosome resolution and show that sister chromatids of X and Y chromosomes, but not autosomes, are segregated nonrandomly during asymmetric divisions of Drosophila male germline stem cells. This provides the first direct evidence, to our knowledge, that two sister chromatids containing identical genetic information can be distinguished and segregated nonrandomly during asymmetric stem-cell divisions. We further show that the centrosome, SUN–KASH nuclear envelope proteins and Dnmt2 (also known as Mt2) are required for nonrandom sister chromatid segregation. Our data indicate that the information on X and Y chromosomes that enables nonrandom segregation is primed during gametogenesis in the parents. Moreover, we show that sister chromatid segregation is randomized in germline stem cell overproliferation and dedifferentiated germline stem cells. We propose that nonrandom sister chromatid segregation may serve to transmit distinct information carried on two sister chromatids to the daughters of asymmetrically dividing stem cells.
