Study On The Relationship Between DNA Methylation And Heterosis In Beef Cattle

In this experiment,Chongqing mountainous cattle(CM)and its F1 to Hereford, Limousin,Black Angus,Red Angus and Simmental were used as the source of DNA samples,the methylation sensitive amplified polymorphism(MSAP)was used for the determination of DNA methylation contents in the ear tissue of cattle.At the same time, the significant differences in DNA methylation level between parental line and its hybrids,among different cross combinations,were analyzed.In addition,the association analyses' between DNA methylation and growth traits were performed. These will offer theory support for heterosis.1.The ear tissue DNAs were amplified using 10 MSAP selective primer combinations,and about 20000 bands were amplified altogether.In CM,the total methylation level was 40.03%,including 27.03%full-methylation and 13.00% hemimethylation.The total methylation level in Red Angus×Chongqing(RC), Simmental×Chongqing(SC),Black Angus×Chongqing(BC),Hereford×Chongqing (HC),Limousin×Chongqing(LC)were 33.10%,35.67%,34.36%,34.07%and 37.31% respectively.Full-methylation were 22.53%,24.58%,23.09%,22.73%,25.63%,and hemimethylation were 10.57%,11.08%,11.27%,11.34%and 11.69%,respectively. According to total methylation level,full-methylation and hemimethylation,hybrid was lower than parent,and full-methylation was the chief methylation status in six breeds.2.To analyze significant difference if the CM and its upgrading offsprings,and different cross combinations in methylation level had been reached,and the data were compared with one-way analysis of variance.The difference of total methylation between CM and HC,SC,BC,RC,between LC and HC,BC,RC were extremely siguificant(P＜0.01).The difference of total methylation between CM and LC was significant(P＜0.05).In full-methylation level,CM,LC had extremely significant difference with HC,BC,RC(P＜0.01),SC had significant difference with RC, CM(P＜0.05).In hemimethylation level,CM had extremely significant difference with SC,RC,BC,HC(P＜0.01).The difference of hemimethylation between CM and LC was significant(P＜0.05).In addition,amplified fragments were not identical between parental line and its hybrids,among different cross combinations,based different primer combinations.The datum were treated with paired-samples T test,and the difference between CM and SC,RC,HC was significant(P＜0.05).3.The SPSS statistics software was used to analyze the relationship between methylation level and growth traits,heterosis rates:in the CM and their hybrids, methylation affected heart girth and body weight highly significantly(P＜0.01), methylation and body slanting length significantly(P＜0.05).Methylation content and heterosis rates of heart girth,body weight showed signifcant correlation(P＜0.05).