DNA Methylation Analysis in Sperm from Infertile/Subfertile Boars

Male infertility is an increasing health challenge for our societies, either for human or livestock’s populations. As diffusion of the genetic progress goes through sires, male infertility consequently slows the improvement of animal selection schemas and farms’ productivity.

We are studying the epigenetic marks in sperm and somatic DNA from fertile and subfertile/infertile boars. As some imprinted loci are altered in infertile humans, we focused our analysis on several imprinted loci in the pig. We first compare the methylation level of almost a hundred imprinted loci both in fertile and subfertile/infertiles animals. We then selected specific loci showing a variation in their methylation level and we analyzed those regions by bisulfite conversion and pyrosequencing. We noticed at least one imprinted gene with a high DNA hypermethylation in the spermatic DNA of oligo-astheno-teratospermic animals compared to fertile animals, two of them carrying chromosomal rearrangements. No change was observed in somatic DNA.

In addition, we provide here the genome-wide distribution of methylation and hydroxymethylation in sperm DNA from fertile Large White boars using MeDIP-seq technology. In our analysis, we specifically focused on imprinted genes and genes involved during early development and pluripotency.

Our aim is to define epigenetic signatures of farm animals’ infertility. These epigenetic signatures will be an additional parameter to evaluate the sperm quality and to lower the number of potentially infertile males in the selection schemas. Moreover our study provides novel data on mammalian sperm methylome and will help to understand DNA methylation and hydroxymethylation function in mammalian gametes.