Differential DNA Methylation Regions in Adult Human Sperm following Adolescent Chemotherapy: Potential for Epigenetic Inheritance

The potential that adolescent chemotherapy can impact the epigenetic programming of the germ line to influence later life adult fertility and promote epigenetic inheritance was investigated. Adult males approximately ten years after pubertal exposure to chemotherapy were compared to adult males with no previous exposure. Sperm were collected to examine differential DNA methylation regions (DMR) between the exposed and control populations. A statistically significant signature of DMRs was identified in the chemotherapy exposed male sperm. The DMRs, termed epimutations, were found in CpG desert regions of primarily 1 kilobase size. Gene associations and correlations to genetic mutations (copy number variation) were also investigated. Observations indicate adolescent chemotherapy exposure can promote epigenetic alterations that persist in later life. The germline (i.e. sperm) epimutations identified suggest chemotherapy has the potential to promote epigenetic inheritance to the next generation. Overall design: DNA from the semen samples was isolated and equal amounts of DNA from 3 individuals pooled to generate three different pools of control (no previous chemotherapy) and three different pools of adolescent chemotherapy exposed cancer survivors labeled human sperm pools (HS#) #1 through #6. The pooled DNA was immunoprecipitated with 5 methyl cytosine monoclonal antibody for a methylated DNA immunoprecipitation (MeDIP). The MeDIP DNA was used to generate libraries and bar coded (index primers) separately for analysis by next generation sequencing (MeDIP-Seq).