What the human sperm methylome tells us

Area of Science:

• Reproductive Biology
• Epigenetics
• Genomics

Background:

• Sperm DNA methylation patterns are crucial for male fertility and embryonic development.
• Understanding the sperm methylome provides insights into epigenetic inheritance.

Purpose of the Study:

• To characterize the comprehensive DNA methylation profile of human spermatozoa.
• To identify genes and chromosomal regions with distinct methylation patterns in fertile donors.

Main Methods:

• Semen samples from 19 proven fertile donors were analyzed.
• Bisulfite-converted sperm DNA was profiled using the HumanMethylation450 Infinium BeadChip array.
• CpG methylation levels were quantified as β-values.

Main Results:

• The sperm methylome exhibits high homogeneity and is generally hypomethylated.
• Hypomethylated promoters are enriched in genes associated with spermatogenesis and embryogenesis.
• Sex chromosomes are the most hypomethylated, highlighting their role in sperm development.
• 94 demethylation-resistant genes were identified as candidates for transgenerational epigenetic inheritance.

Conclusions:

• Spermatozoa possess a homogeneous methylation profile that serves as a record of spermatogenesis.
• This methylation pattern is optimized for successful embryogenesis.
• Sperm methylation may influence offspring adult life through transgenerational effects.