DNA Methylation Status of Three Imprinted Genes in the Cloned Sheep
1. College of Life Science,Inner Mongolia Agricultural University2. Inner Mongolia Saikexing Reproductive Biotechnology Co3. Inner Mongolia Key Laboratory of Bio-Manufacture
摘要：Somatic cell nuclear transfer（SCNT）has been successfully applied to many mammalian species.However,many defects have been found in whole program or in the offspring body,such as increased abortion rate,perinatal death,low pregnancy rates and increased fetal and placental abnormalities（called as large offspring syndrome,LOS）.Until now,abnormal epigenetic modifications,such as DNA methylation,histone modifications and chromatin reconstructions,have been reported in several cloned species.Particularly,genomic imprinting and DNA methylation have an important impact on normal mammalian development,fetal growth and adult behavior.At present,many cloned animals also showed heterogeneous DNA methylation profiles.However,fewer were well demonstrated both in normal development and in SCNT cloned lambs owe to limited resources of the cloned offspring,the ovine genome and study about ovine genomic imprinting.In this study,in order to show the reprogramming degree of cloned lambs,we investigated DNA methylation patterns in CpG islands and in differentially methylated regions（DMRs）of putative imprinted gene Peg3,Cdknlc and Gtl2 in cloned lambs.Different organs（livers,kidneys,hearts,muscles and lungs）from two cloned lambs that died shortly after birth and two normal controls were sampled.We cloned the putative DMRs and predicted the CpG islands of these imprinted genes.Peg3 was seriously methylated in both groups tested,whereas Cdknlc and Gtl2 showed unmethylated state or hypomethylation in cloned lambs.However,DNA methylation status of three imprinted genes has a very steady state and both groups showed nearly the same DNA methylation for the putative imprinted genes.In summary,SCNT-cloned sheep experienced relatively completed DNA methylation reprogramming.