5-methylcytosine (m5C) as a rare base exists in eucaryotic genomes, it is a normal constituent of many eucaryotic DNA, whose existence is a character of eucaryotic DNA. In the regular physiological conditions, cytosin...5-methylcytosine (m5C) as a rare base exists in eucaryotic genomes, it is a normal constituent of many eucaryotic DNA, whose existence is a character of eucaryotic DNA. In the regular physiological conditions, cytosine residue of eucaryotic DNA is methylated to be popular. Up to the present, many people consider that the m5C may be mutation hotspots by the m5C deamination leading to gene mutation. Our theoretical investigations indicated that the spontaneous mutation caused by the transition of G - C-A - T, in eukaryotic DNA, may be a result caused by the tautomer changing base pairs and may also be caused by other factor actions, however it could not be caused by the deamination of m5C.展开更多
By using the approach of immunofluorescence staining with an antibody against 5-methylcytosine(5MeC),the present study detected the DNA methylation patterns of cloned ovine embryos.The em-bryos derived from in vitro f...By using the approach of immunofluorescence staining with an antibody against 5-methylcytosine(5MeC),the present study detected the DNA methylation patterns of cloned ovine embryos.The em-bryos derived from in vitro fertilization were also examined for reference purpose.The results showed that:(1)during the pre-implantation development,cloned embryos displayed a similar demethylation profile to the fertilized embryos;that is,the methylation level decreased to the lowest at 8-cell stage,and then increased again at morulae stage.However,methylation level was obviously higher in cloned embryos than in stage-matched fertilized embryos,especially at 8-cell stage and afterwards;(2)at blastocyst stage,the methylation pattern in cloned embryos was different from that in fertilized em-bryos.In cloned blastocyst,inner cell mass(ICM)exhibited a comparable level to trophectoderm cells(TE),while in in-vitro fertilized blastocyst the methylation level of ICM was lower than that of TE,which is not consistent with that reported by other authors.These results indicate that DNA methylation is abnormally reprogrammed in cloned embryos,implying that aberrant DNA methylation reprogramming may be one of the factors causing cloned embryos developmental failure.展开更多
文摘5-methylcytosine (m5C) as a rare base exists in eucaryotic genomes, it is a normal constituent of many eucaryotic DNA, whose existence is a character of eucaryotic DNA. In the regular physiological conditions, cytosine residue of eucaryotic DNA is methylated to be popular. Up to the present, many people consider that the m5C may be mutation hotspots by the m5C deamination leading to gene mutation. Our theoretical investigations indicated that the spontaneous mutation caused by the transition of G - C-A - T, in eukaryotic DNA, may be a result caused by the tautomer changing base pairs and may also be caused by other factor actions, however it could not be caused by the deamination of m5C.
基金the National Natural Science Foundation of China(Grant No.30270956)High-Tech Research & Development Program of China(Grant No.2006AA02Z148)
文摘By using the approach of immunofluorescence staining with an antibody against 5-methylcytosine(5MeC),the present study detected the DNA methylation patterns of cloned ovine embryos.The em-bryos derived from in vitro fertilization were also examined for reference purpose.The results showed that:(1)during the pre-implantation development,cloned embryos displayed a similar demethylation profile to the fertilized embryos;that is,the methylation level decreased to the lowest at 8-cell stage,and then increased again at morulae stage.However,methylation level was obviously higher in cloned embryos than in stage-matched fertilized embryos,especially at 8-cell stage and afterwards;(2)at blastocyst stage,the methylation pattern in cloned embryos was different from that in fertilized em-bryos.In cloned blastocyst,inner cell mass(ICM)exhibited a comparable level to trophectoderm cells(TE),while in in-vitro fertilized blastocyst the methylation level of ICM was lower than that of TE,which is not consistent with that reported by other authors.These results indicate that DNA methylation is abnormally reprogrammed in cloned embryos,implying that aberrant DNA methylation reprogramming may be one of the factors causing cloned embryos developmental failure.
