| Using the model of Yorkshire and Erhualian reciprocal crosses pigs as experiment animals and raise them under the same conditions. F1 crossbreds were produced from Yorkshire boars x Erhualian sows (F1:YE) as well as Erhualian boars x Yorkshire sows (F1: EY). We randomly selected F1 crossbreds at 50(E50),70(E70) and 90(E90) days of embryonic stage and at 1(D1),20(D20),70(D70),120(D120) and 180(D180) days of postnatal development. Then we separately collected the samples of longissimus dorsi muscle and semitendinosus muscle from those pigs, there are four parts in our studies.1. Expression of the insulin-like growth factor system in skeletal muscle during embryonic and postnatal development in the first filial generation pigs from Erhualian and Yorkshire reciprocal crossesIn this study, we used real-time quantitative PCR to measure the developmental expression patterns of IGF-Ⅰ, IGF-Ⅱ, IGF-ⅠR, IGF-ⅡR and IGFBP-3 mRNA in skeletal muscle of pigs. The results indicated that:(1) The expression of IGF-Ⅰand IGF-ⅡmRNA in skeletal muscle tissues was changed with developmental age (P<0.05). The expression of IGF-I mRNA exhibited fluctuant ascending trend, in contrast, IGF-ⅡmRNA showed fluctuant descending trend after birth in YE and EY pigs. The levels of IGF-IR mRNA were higher (P<0.05) before than after birth except for D120 of LD in EY pig. The IGF-IIR mRNA expression was changed remarkably with age and breeds in general (P<0.05). The expression of IGFBP-3 mRNA was changed with developmental age and breeds in general (P<0.05), but it had no differences after birth in LD muscle. (2) We found IGF-II(E50-D180), IGF-IR(E50-D180), IGF-IIR(E50-D1 in LD and E70-D20 in ST)and IGFBP-3 (E70-D20 in LD and E50-D180 in ST) were positively correlated with IGF-I; IGF-IR(E50-D180), IGF-IIR(E50-D20 in LD and E70-D20 in ST) and IGFBP-3(E50-D180) were positively correlated with IGF-II; IGF-IIR(E50-D20 in LD and E50-D1 in ST) and IGFBP-3(E50-D180) were positively correlated with IGF-IR; IGF-IIR(E70-D70) was positively correlated with IGFBP-3. (3) The changed trend of cross-sectional area of myofibres (CAS) was similar to IGF-I, IGF-IR and IGF-IIR while CAS was converse to IGF-II and IGFBP-3. These data suggest that the expression mRNAs of IGFs system genes exhibit specific developmental pattern in skeletal muscle tissues of reciprocal crosses pigs at different developmental stages and may show linked expression during certain periods of development. Our results can provide a valuable resource for the molecular breeding of pigs.2. Expression of MyoD, MyoG and MSTN mRNA in skeletal muscle during embryonic and postnatal development in the first filial generation pigs from Erhualian and Yorkshire reciprocal crossesIn this study, we found that:The expression of MyoD mRNA remarkably changed with age and reciprocal cross type in general (P<0.05). The expression of MSTN and MyoG mRNA levels were higher before birth compared with after birth (P<0.05) except for MyoG mRNA of YE pigs at D180 and they were also obviously affected by reciprocal cross type (P<0.05). MSTN mRNA was positively correlated with MyoG from E50 to D180 in LD and ST, the expression patterns MSTN mRNA was similar to a MyoD. These data suggest that the expression of MyoD, MyoG and MSTN genes exhibits specific developmental patterns in skeletal muscle of pigs from reciprocal crosses at different developmental stages. Our results may provide a valuable resource for the molecular breeding of pigs.3. Histone modifications at promoters of MyoD, MyoG and MSTN genes expressed in skeletal muscle during embryonic and postnatal development of pigsRecent advances in chromatin biology have enhanced our understanding of gene regulation. It is now widely appreciated that gene regulation is dependent upon post-translational modifications to the histones. Active genes are known to be associated with acetylation of histones (H3ac) and trimethylation of lysine 4 in histone H3 (H3K4me3). Chromatin immunoprecipitation (ChIP) and real-time quantitative PCR were used to examine histone modifications at promoters of MyoD, MyoG and MSTN genes expressed in skeletal muscle during embryonic and postnatal development of pigs, we compared differences between developmental age and breeds in general. The results indicated that:(1) In YE pig, H3ac at MyoD was similar to MyoG except for 90E and ID, which exhibited fluctuant patterns. In EY pig, H3ac at MyoD was same as at MyoG, which was higher at 120D. H3ac at MSTN107 and MSTN279 was similar, in YE pig, H3ac at MSTN306, MSTN163 and MSTN278 exhibited highly fluctuant patterns. In EY pig, the fluctuant changes of H3ac were higher at MSTN163. (2)In YE pig, H3K4me3 at MyoD was similar to MyoG, which exhibited fluctuant patterns. In EY pig, there were no significant changes in H3K4me3 at MyoD, and H3K4me3 at MyoG were higher at D1, D70, D120, and D180 compared with embryonic periods and D20, which was higher at D120. There were similar patterns in H3K4me3 at MSTN except for MSTN278 at D180. In short, there were higher in H3ac and H3K4me3 at MyoD, MyoG and MSTN compared YE with EY during embryonic periods, the expression of those genes were lower compared YE with EY, which was oppose corresponds with histones modifications. But, the expression of those genes were higher compared YE with EY, which similarly corresponds with the histones modifications.4. DNA methylation at promoters of MyoD and MyoG genes expressed in skeletal muscle during embryonic and postnatal development of pigsIn this study, we used MassARRAY system to examine DNA methylation at promoters of MyoD and MyoG genes expressed in skeletal muscle during embryonic and postnatal development of pig, we compared differences between developmental age and breeds in general. The results indicated that:(1) there were eight sites of CpG at promoters of MyoD, we found different level of DNA methylation in different sites, site 1,2,3 was higher, site5,6 and site7,8 were lower. The level of DNA methylation in sitel,2,3 was similar in YE pigs and EY pigs (P<0.05). But, there different level of DNA methylation in site5,6 and site7,8 during specific developmental stages between YE pigs and EY pigs. There were no significant differences in Total DNA methylation levels at MyoD gene except for E50 and E70 were higher than D120 and D180 of EY pig. (2) we examined eight sites of CpG at promoters of MyoG, MyoG exhibited different fluctuant DNA methylation patterns In YE pigs and EY pigs, DNA methylation at MyoG were higher EY pigs compared with YE pigs at E70 (P<0.05)、D 20 (P<0.05)、D70 (P<0.01)、D120 (P<0.01) and D180 (P<0.01). |
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