核移植后的细胞核再程序化机制研究进展

Progress on Mechanism of Nuclear Reprogramming After Nuclear Transfer

目前动物克隆技术体系极待完善 ,其极低的成功率及克隆动物普遍存在的早衰、早夭现象是阻碍研究深入进行的首要问题 ,其突破的关键在于对核移植后的细胞核再程序化机制的阐明。从移植核在结构上的重塑、移植核与受体卵细胞质所处的细胞周期及其相互作用、重构胚与两性胚在分子水平的变化等多方面研究表明 :受体细胞质的环境对于细胞核的再程序化至关重要 ,处于有丝分裂各时期的细胞作为核供体一旦移植到卵母细胞后 ,移植核在卵质环境里将出现结构上的重塑和分子的再程序化 ;移植核与受体卵间细胞周期的相容性、重构胚的染色体倍性的正确与否 ,可能是决定重构胚发育率高低的重要因素 ;合子型基因激活是基因表达再程序化的关键事件之一 ;印记基因对于体细胞克隆动物移植核的再程序化过程可能起着非常独特的作用。

Despite cloned animals becoming almost commonplace,there is no perfect cloning technique system yet and behind every success lies hundreds of failures.Moreover,cloned animals often age and die quickly.All of those problems hinder further research in nuclear transplantation.The key to make a break-through in the research of cloned animals relies on elucidating mechanism of nuclear reprogramming.Therefore,progress on nuclear reprogramming in nuclear transplantation has been reviewed in some aspects,for example remodeling of the nuclear structure,nucleocytoplasmic interactions and effects of the cell cycle,difference of gene expression and genomic imprinting between reconstructed embryos and fertilized embryos,etc.These results indicate that cytoplastmic environment is very important for the reprogramming of transplanted nuclei.When a donor nucleus in any stage of the cell cycle is transferred into the cytoplasm of an oocyte,there are the twin processes of structural remodeling and molecular reprogramming of the nucleus after transplantation.It is evident that the cell cycle coordination between donor cell and recipient cytoplast to avoid DNA damage and to maintain correct ploidy of the reconstructed embryo is of critical importance in determining the developmental capacity of reconstructed embryos.A dramatic reprogramming of gene expression occurs during zygotic gene activation.The time of zygotic gene activation may affect nuclear reprogramming and consequently the development of reconstructed embryo to offspring.Imprinted genes are related to the reprogramming and aberrant development seen in manipulated embryos,and may be critical in the reprogramming of transplanted somatic cell.