Bisulfite genomic sequencing-derived methylation profile of the Xist gene throughout early mouse development

Differential epigenetic modification by methylation of CpG; dinucleotides i s a candidate mechanism that may identify the alleles of imprinted genes an d result in monoallelic expression of either the maternal or the paternal a llele. Determination of the allelic methylation status of imprinted genes i n the gametes and during early development is constrained by the limiting q uantities of genomic DNA available from these early developmental stages. T o circumvent this problem we have used bisulfite genomic sequencing to dete rmine the allelic methylation status of the minimal promoter and a l-kb reg ion within the Xist gene during preimplantation development. We find that t he parental Xist alleles are not differentially methylated in these regions . Our findings are discussed in the context of previous conflicting data ob tained using methylation-sensitive restriction enzyme digestion followed by PCR amplification to assay for methylation. (C) 1998 Academic Press.