RESUMO
The developmental dynamics of DNA methylation events have been well studied. Active demethylation of the paternal genome occurs in the zygote, passive demethylation occurs during cleavage stages, and de novo methylation occurs by the blastocyst stage. It is believed that the paternal genome has lower levels of methylation during early development than the maternal genome. However, in this study, we provide direct and indirect evidence of genome-wide de novo DNA methylation of the paternal genome after the first cell cycle in mouse embryos. Although very little methylation was detected within the male pronucleus in zygotes, an intense methylation signal was clearly visible within the androgenetic 2-cell embryos. Moreover, the DNA methylation level of the paternal genome in the post-zygotic metaphase embryos was similar to that of the maternal genome. Using indirect immunofluorescence with an antibody to methylated lysine 9 in histone H3, we provided new evidence to support the concept of spatial compartmentalization of parental genomes in 2-cell mouse embryos. Nevertheless, the transient segregation of parental genomes was not observed by determining the DNA methylation distribution in the 2-cell embryos even though DNA methylation asymmetry between the maternal and paternal pronucleus existed in the 1-cell stage. The disappearance of separate immunofluorescence signals of 5-methyl cytosine in the 2-cell embryos might be attributed to the de novo methylation of the paternal genome during the first mitotic cycle.
Assuntos
Blastocisto/metabolismo , Metilação de DNA , Genoma , Impressão Genômica , Animais , Feminino , Masculino , CamundongosRESUMO
Insulin-like growth factors (IGFs) are regulators that modulate the proliferation and differentiation of muscle tissues. We quantified the messenger RNA (mRNA) expression of IGF-I, IGF-II, and type I and II IGF receptors (IGF-IR and IGF-IIR) in muscle tissues including the breast, leg, and myocardium during an early postnatal development growth stage (post-hatching weeks 1-8) in ducks. The results showed a significant age-related change in mRNA in these muscle tissues. In breast muscle, the developmental expression of IGF-I and IGF-II was highest during week 1 but decreased quickly and maintained a relatively lower level. Leg muscle had the highest mRNA expression of IGF-I and IGF-II genes at week 3. In myocardial tissues, the expression level of IGF-IR and IGF-IIR genes exhibited a "rise-decline" developmental trend. The expression patterns of IGF-I/IGF-IR and IGF-II/IGF-IIR were different between weeks 4 and 6. The same expression pattern was observed for IGF-I and IGF-IR; however, it was different from that observed for IGF-II and IGF-IIR. Our results showed a negative correlation between IGF-II mRNA expression and leg muscle weight at week 4 (P < 0.05). A negative correlation was also found between IGF-II mRNA expression and breast muscle weight (P < 0.01), and a positive correlation was found between IGF-IR expression and breast muscle weight. At week 6, a positive correlation was found between IGF-IR expression and breast muscle weight. However, at week 8, a negative correlation was found between IGF-IR expression and breast muscle weight. The results showed that the expression of IGF mRNA in duck tissues exhibits a specific developmental trend and an age-related pattern, suggesting that the regulation mechanism of these 4 genes in proliferation and differentiation of muscle tissues differed.
Assuntos
Proteínas Aviárias/genética , Patos/crescimento & desenvolvimento , Músculo Esquelético/metabolismo , Somatomedinas/genética , Animais , Proteínas Aviárias/metabolismo , Patos/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Especificidade de Órgãos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores de Somatomedina/genética , Receptores de Somatomedina/metabolismo , Somatomedinas/metabolismo , TranscriptomaRESUMO
Typically, production of induced pluripotent stem cells requires direct contact with feeder cells. However, once the stem cells have reached the appropriate maturation point, it is difficult to separate them from feeder cells, which must be irradiated with γ-rays or treated with the antibiotic mitomycin-C. We used a microporous poly-membrane-based indirect contact co-culture system with mouse embryonic fibroblasts to induce mouse pluripotent stem cells without radiation or antibiotics. We found that induced pluripotent stem cells induced by this co-culture method had a reprogramming efficiency and time similar to those induced using traditional methods. Furthermore, strongly expressed pluripotent markers showed a normal karyotype and formation and contained all three germ layers in a teratoma.