Study On The Mechanism Of Cell Memory For Mammalian Genomic Imprinting

Genomic imprinting is a new genetic phenomenon that differs from the classical Mendel genetic law, the imprinted genes always express monoallelically. It was shown that, many genes related to development and growth closely are imprinted genes,and some human disease such as cancers were resulted from the abnormal imprint of some genes.But the expressed pattern of these genes are not well known.In our experiment,using DNase I and Hpa II to analyze the promoter and differentially methylated region(DMR) of two illu minated imprinted genes, U2afl-rsl and lgf2r,we found that,as the important regulating elements for imprinted genes,promoter and DMR all show hypersensitivity to DNase I and Hpa II in metaphase.So, as our review, there are some loose chromosomal structure which are decondensated in mitosis while oTher chromatin are condensated in this phase.And, the methylation in promoter is differential between the two alleles in metaphase.DNasel assay on DMR2 of Igf2r gene indicated that differential chromatic structure between allelic sites characterized the DMR2.It followed that,the loose chromatic structure in promoter and DMR2 may be consistent with nonmethylation in these regions.It was concluded that the expressed pattern of imprinted genes marked/imprinted on the chromatin strictly, which(specific chromatic structure) may be the mark for cell memory.Furthermore,we established a novel and faithful method to detect methylation-nested PCR,this method using only three primers can profoundly increase the reliability of the results and avoid the pseudo-positive results.