Merico Valeria, Barbieri Jessica, Zuccotti Maurizio, Joffe Boris, Cremer Thomas, Redi Carlo Alberto, Solovei Irina, Garagna Silvia
Dipartimento di Biologia Animale, Laboratorio di Biologia dello Sviluppo, Piazza Botta 9, Universita' degli Studi di Pavia, 27100, Pavia, Italy.
Chromosome Res. 2007;15(3):341-60. doi: 10.1007/s10577-007-1130-5. Epub 2007 May 10.
Chromosomes, sub-chromosomal regions and genes are repositioned during cell differentiation to acquire a cell-type-specific spatial organization. The constraints that are responsible for this cell-type-specific spatial genome positioning are unknown. In this study we addressed the question of whether epigenetic genome modifications may represent constraints to the acquisition of a specific nuclear organization. The organization of kinetochores, pericentric heterochromatin and the nucleolus was analysed in pre-implantation mouse embryos obtained by in-vitro fertilization (IVF), parthenogenetic activation (P) and nuclear transfer (NT) of differentiated somatic nuclei, which possess different epigenomes. Each stage of pre-implantation embryonic development is characterized by a stage-specific spatial organization of nucleoli, kinetochores and pericentric heterochromatin. Despite differences in the frequencies and the time-course of nuclear architecture reprogramming events, by the eight-cell stage P and NT embryos achieved the same distinct nuclear organization in the majority of embryos as observed for IVF embryos. At this stage the gametic or somatic nuclear architecture of IVF or P and NT embryos, respectively, is replaced by a common embryonic nuclear architecture. This finding suggests that the epigenome of the three types of embryos partially acts as a constraint of the nuclear organization of the three nuclear subcompartments analysed.
在细胞分化过程中，染色体、亚染色体区域和基因会重新定位，以获得细胞类型特异性的空间组织。导致这种细胞类型特异性空间基因组定位的限制因素尚不清楚。在本研究中，我们探讨了表观遗传基因组修饰是否可能是获取特定核组织的限制因素这一问题。我们分析了通过体外受精（IVF）、孤雌激活（P）和分化体细胞核移植（NT）获得的植入前小鼠胚胎中的动粒、着丝粒周围异染色质和核仁的组织情况，这些胚胎具有不同的表观基因组。植入前胚胎发育的每个阶段都以核仁、动粒和着丝粒周围异染色质的阶段特异性空间组织为特征。尽管核结构重编程事件的频率和时间进程存在差异，但到八细胞阶段时，P和NT胚胎在大多数胚胎中实现了与IVF胚胎相同的独特核组织。在此阶段，IVF或P和NT胚胎的配子或体细胞核结构分别被共同的胚胎核结构所取代。这一发现表明，这三种类型胚胎的表观基因组部分地对所分析的三个核亚区室的核组织起到了限制作用。
