Dysregulation of genome-wide gene expression and DNA methylation in abnormal cloned piglets (MeDIP-seq)

Backgroud:Epigenetic modifications (especially altered DNA methylation) resulting in altered gene expression may be one reason for development failure or the abnormality of the cloned animals, but the underlying mechanism of the abnormal phenotype in the cloned piglets remains unrevealed. Some cloned piglets in our study showed abnormal phenotypes such as big tongue (longer and thicker), limp, and exomphalos, which is similar to the human BWS syndrome. Here we conducted DNA methylation (DNAm) immunoprecipitation binding high throughput sequencing (MeDIP-seq) and RNA sequencing (RNA-seq) of muscle tissues of cloned piglets to investigate the relationship of abnormal DNAm with gene dysregulation and the unusual phenotypes in cloned piglets. Results:Analysis of the methylomes revealed that abnormal cloned piglets suffered more hypomethylated differentially methylated regions (DMRs) than hypermethylated DMRs compared to the normal cloned piglets. The DNAm level in the CpG Island was higher in the abnormal cloned piglets. Some repetitive elements, such as SINE/tRNA-Glu Satellite/centr also showed significant differences. Besides we detected 1,711 differentially expressed genes (DEGs) between the two groups, of which 243 genes also changed methylation level in the abnormal cloned piglets. The altered DNA methylation mainly affected the low and silent expression genes. We also found some interesting pathways and genes, such as MAPK signalling pathway, hypertrophic cardiomyopathy pathway, TPM3 gene and the imprinted gene PLAGL1, which may played important roles in the abnormal phenotype development. Conclusions;The abnormal cloned piglets showed substantial change both in the DNAm and the gene expression levels. Our data may provide new insights into understanding the molecular mechanisms of the reprogramming of genetic information in cloned animals. We dissected the biceps femoris muscle from the abnormal cloned piglets and the normal cloned piglets, and analyzed the difference of MeDIP-seq and RNA-seq between the two groups.