Bolan Yu
Key Laboratory, China
Title: Cigarette smoking is associated with epigenetic instability in human sperm
Biography
Biography: Bolan Yu
Abstract
Smoking is one of the most common risk factor for reproductive health worldwide, and it has been proven to be associated with decreased fertility and poor semen quality. During human spermatogenesis, transition of histone to protamine and the remodeling of methylation of whole genome in mature sperm are two critical important epigenetic processes. However, whether cigarette smoke exposure could affect them are largely unknown. In our recent study, we demonstrated that both histone to protamine transition and methylation in sperm from heavy smoking men had significantly alterations compared to their nonsmoking counterparts in an ethnic Han Chinese population in South China. The abnormalities of sperm histone replacement in heavy smokers were found to be closely correlated with sperm motility, viability, concentration, counts, and cotinine levels. The ratios of protamine 1 to protamine 2 mRNA expression also significantly increased in heavy smokers and in TM3 cells treated with cigarette smoke condensate. In addition, heavy smokers had significantly increased global methylation in sperm DNA than nonsmokers. Further microarray data demonstrated that methylation status had significantly altered in many loci from sperm DNA of heavy smokers, including many imprinting genes and functional genes. These results are being validated in a large group of smoking population. Overall, our study demonstrated that smoking could lead to sperm DNA epigenetic instability by increasing the abnormalities of histone to protamine transition, causing alteration of protamine mRNA expression in mature sperm, and changing methylation profiling in human sperm DNA. These epigenetic alterations associated with smoking may potentially affect human fertilization, embryo development, and offspring growth.