Retrotransposon-Derived Promoter of Mammalian Aebp2

Variable DNA methylation in promoter regions has been implicated in altering transcriptional regulation. The current study analyzed the evolutionary origin and DNA methylation pattern of one of the promoters of Aebp2. According to the results, the first promoter of Aebp2 has been derived from retrotransposons independently in the primate and rodent lineages. DNA methylation analyses revealed that this promoter is unmethylated in sperm, methylated in mature oocytes, and partially methylated at embryonic day 10.5 (78.3%) and 14.5 (58.3%). This promoter also shows variable levels of DNA methylation among adult organs, ranging from the highest in spleen (~80%) to the lowest in tail (~50%). The results from the F1 hybrid of interspecific crossing further indicated that both alleles are equally methylated without any allele bias, also supported by its biallelic expression. Therefore, the partial methylation observed among somatic tissues is an outcome of the genome-wide resetting of DNA methylation during the implantation stage, but not of the inherited allelic methylation pattern preset during gametogenesis. Taken together, mammalian Aebp2 has adopted retrotransposons as its promoter, which displays partial DNA methylation pattern of allelic- or non-allelic origin during the different stages of development.