Genomic Imprinting And DNA Methylation Status Of PEG11Gene In Naturally Reproduced And SCNT Cattle

Somatic cell nuclear transfer (SCNT) has been successfully applied to manymammalian species. However, many of those that can develop to birth often display avariety of the organ abnormalities. It appears to be a great barrier to efficient cloning. Theincomplete reprogramming of donor cell nuclei leading to aberrant expression or lack ofexpression of some developmentally important genes has been implicated as a primaryreason for the low efficiency of SCNT. DNA methylation is a major epigeneticmodification of the genome that regulates some crucial aspects of its function. Genomicimprinting is an epigenetic phenomenon that results in an allele-specific expression,depending on its parental origin.The result of dendrogram of six mammal species (sheep, mouse, panda, pig, humanand bovine) indicated that bovine and pig shared the minimum genetic distance. Theimprinting status of PEG11has not been established in cattle. In this study, a SNP (A/Gtransition) was identified in PEG11gene and used to analysis its allele-specific expressionand DNA methylation in natural breeding and SCNT cattle. Our analysis demonstrated that,in natural breeding bovines, one paternal allele expression of PEG11was observed inseven tissues, including heart, liver, spleen, kidney, lung, fat and skeletal muscles,suggesting that PEG11is imprinted in cattle. But PEG11showed abnormal biallelicexpression in lung tissue of died SCNT cattle, which had serious developmental defect. CGPlot analysis revealed that no CGs islands (CGI) exist in transcriptional start sites of cattlePEG11, but rich CGI are found in gene body.In order to determine whether gene body methylation plays a role in regulation of thePEG11imprinting, the allele-specific DNA methylation status of54intragenic CGsposition were analyzed in natural breeding cattle. Seriously hypermethylated (>96%) wasexhibited in both of parental strands (A-strand and G-strand, which were named by SNPlocus), implying that the intragenic DNA methylation didn’t involve in regulation of thePEG11imprinting expression. When the DNA methylation was examed in lungs of SCNTbovines, which showing aberrant biallelic expression of PEG11, hypermethylated(97.26%) status were found similar to that of normal bovines, which provide a furtherevidence for no function of intragenic DNA methylation in regulation of the PEG11 imprinting expression. The aberrant biallelic expression of PEG11may be associated withthe lung aberrant development in died SCNT bovines.