Genomic imprinting is a gene regulatory mechanism based on differential methylation, whereby only one of two parental alleles is expressed. Imprinting disorders can lead to abnormal fetal development and malignant disease, and have been previously noted in oocytes (Lancet 2003; 361: 1975-77), but this is the first report showing imprinting defects in sperm.
To investigate whether abnormal genomic imprinting could be associated with disturbed spermatogenesis, Professor Mario Sousa and colleagues extracted sperm DNA from 123 men with low or normal sperm counts. All the men with normal sperm counts had correct methylation, whereas 24% of those with low sperm counts showed methylation defects in their profiles. The less healthy the sperm, the more imprinting defects were observed.
Professor Sousa comments: "Our data suggest an association between abnormal genomic imprinting and hypospermatogenesis, and that spermatozoa from oligozoospermic patients carry a raised risk of transmitting imprinting errors."