O'Hare T H, Delany M E
Department of Animal Science, University of California, Davis, USA.
Cytogenet Genome Res. 2011;135(1):65-78. doi: 10.1159/000330125. Epub 2011 Aug 3.
Telomere maintenance is an important genetic mechanism controlling cellular proliferation. Normally, telomeres are maintained by telomerase which is downregulated upon cellular differentiation in most somatic cell lineages. Telomerase activity is upregulated in immortalized cells and cancers to support an infinite lifespan and uncontrolled cell growth; however, some immortalized and transformed cells lack telomerase activity. Telomerase-negative tumors and immortalized cells utilize an alternative mechanism for maintaining telomeres termed alternative lengthening of telomeres (ALT). This research explored evidence for the ALT pathway in chicken cell lines by studying nontransformed immortalized cell lines (DF-1 and OU2) and comparing them to a normal (mortal) cell line and a transformed cell line (DT40). The research consisted of molecular and cellular analyses including profiling of telomeric DNA (array sizing and total content), telomerase activity, and expression of genes involved in the telomerase, recombination, and ALT pathways. In addition, an immunofluorescence analysis for an ALT marker, i.e. ALT-associated promyelocytic leukemia bodies (APBs), was conducted. Evidence for ALT was observed in the telomerase-negative immortalized cell lines. Additionally, the APB marker was also found in the other cell systems. The attributes of the chicken provide an additional vertebrate model for investigation of the ALT pathway.
端粒维持是控制细胞增殖的一种重要遗传机制。正常情况下，端粒由端粒酶维持，在大多数体细胞谱系中，端粒酶在细胞分化时下调。在永生化细胞和癌症中，端粒酶活性上调以支持无限寿命和不受控制的细胞生长；然而，一些永生化和转化细胞缺乏端粒酶活性。端粒酶阴性肿瘤和永生化细胞利用一种称为端粒替代延长（ALT）的替代机制来维持端粒。本研究通过研究未转化的永生化细胞系（DF-1和OU2），并将它们与正常（有限寿命）细胞系和转化细胞系（DT40）进行比较，探索了鸡细胞系中ALT途径的证据。该研究包括分子和细胞分析，包括端粒DNA分析（阵列大小和总含量）、端粒酶活性以及参与端粒酶、重组和ALT途径的基因表达。此外，还对一种ALT标志物，即ALT相关早幼粒细胞白血病小体（APB）进行了免疫荧光分析。在端粒酶阴性的永生化细胞系中观察到了ALT的证据。此外，在其他细胞系统中也发现了APB标志物。鸡的特性为研究ALT途径提供了另一种脊椎动物模型。
