Dang-Nguyen Thanh Quang, Haraguchi Seiki, Furusawa Tadashi, Somfai Tamas, Kaneda Masahiro, Watanabe Shinya, Akagi Satoshi, Kikuchi Kazuhiro, Tajima Atsushi, Nagai Takashi
Department of Animal Breeding and Reproduction, NARO Institute of Livestock and Grassland Science, Ibaraki 305-0901, Japan.
J Reprod Dev. 2013;59(1):27-32. doi: 10.1262/jrd.2012-118. Epub 2012 Sep 28.
Telomere is a nucleoprotein structure at the ends of chromosomes that helps to protect the ends of chromosomes from being fused with other chromosomes. Knockout of histone methyltransferases Suv39h1 and Suv39h2 increases the telomere length in murine cells, whereas downregulation of SUV39H1 and SUV39H2 genes decreases the telomere length in human cells, suggesting that telomere biology is different among mammalian species. However, epigenetic regulation of the telomere has not been studied in mammals other than the human and mouse. In the present study, the effect of knockdown of SUV39H1 and SUV39H2 genes on telomere length was examined in porcine embryonic stem-like cells (pESLCs) and porcine embryonic fibroblasts (PEFs). The telomeres in SUV39H1 and SUV39H2 knockdown (SUV39KD) pESLCs (37.1 ± 0.9 kb) were longer (P<0.05) compared with those of the control (33.0 ± 0.7 kb). Similarly, SUV39KD PEFs had longer telomeres (22.1 ± 0.4 kb; P<0.05) compared with the control (17.8 ± 1.1 kb). Telomerase activities were not different between SUV39KD pESLCs (10.4 ± 1.7) and the control (10.1 ± 1.7) or between SUV39KD PEFs (1.0 ± 0.3) and the control (1.0 ± 0.4), suggesting that telomerase activities did not contribute to the telomere elongation in SUV39KD pESLCs and SUV39KD PEFs. Relative levels of trimethylation of histone H3 lysine 9 and expressions of DNMT1, DNMT3A and DNMT3B were decreased in SUV39KD cells, suggesting that telomere lengthening in SUV39KD pESLCs and SUV39KD PEFs might be not only related to the loss of histone modification marks but also linked to the decrease in DNA methyltransferase in pigs.
端粒是染色体末端的一种核蛋白结构，有助于保护染色体末端不与其他染色体融合。敲除组蛋白甲基转移酶Suv39h1和Suv39h2可增加小鼠细胞中的端粒长度，而SUV39H1和SUV39H2基因的下调则会缩短人类细胞中的端粒长度，这表明不同哺乳动物物种的端粒生物学存在差异。然而，除了人类和小鼠之外，尚未在其他哺乳动物中研究端粒的表观遗传调控。在本研究中，检测了敲低SUV39H1和SUV39H2基因对猪胚胎干细胞样细胞（pESLCs）和猪胚胎成纤维细胞（PEFs）中端粒长度的影响。与对照组（33.0±0.7 kb）相比，SUV39H1和SUV39H2基因敲低（SUV39KD）的pESLCs中的端粒更长（37.1±0.9 kb，P<0.05）。同样，与对照组（17.8±1.1 kb）相比，SUV39KD的PEFs具有更长的端粒（22.1±0.4 kb，P<0.05）。SUV39KD的pESLCs（10.4±1.7）与对照组（10.1±1.7）之间或SUV39KD的PEFs（1.0±0.3）与对照组（1.0±0.4）之间的端粒酶活性没有差异，这表明端粒酶活性对SUV39KD的pESLCs和SUV39KD的PEFs中的端粒延长没有贡献。在SUV39KD细胞中，组蛋白H3赖氨酸9的三甲基化相对水平以及DNMT1、DNMT3A和DNMT3B的表达均降低，这表明SUV39KD的pESLCs和SUV39KD的PEFs中的端粒延长可能不仅与组蛋白修饰标记的缺失有关，还与猪中DNA甲基转移酶的减少有关。
