Abnormal methylation of the promoter of CREM is broadly associated with male factor infertility and poor sperm quality but is improved in sperm selected by density gradient centrifugation

ObjectiveTo evaluate the methylation status of the promoter of CREM in patients with an abnormal protamine 1/protamine 2 (P1/P2) ratio or oligozoospermia. The effects of density gradient centrifugation and aging of males on CREM promoter methylation were also investigated.DesignExperimental research study.SettingUniversity andrology and research laboratory.Patient(s)Patients with abnormally low (n = 24) and high (n = 36) P1/P2 ratio; patients with oligozoospermia (n = 32); and normozoospermic, fertile controls with normal P1/P2 ratio (n = 40).Intervention(s)The CpG methyaltion pattern of the promoter of CREM was examined using pyrosequencing.Main Outcome Measure(s)The percentage of methylation of 12 CpGs in the CREM promoter was compared between patients and fertile controls.Result(s)There was a significantly higher rate of methylation of CREM in patients with abnormal protamination and oligozoospermia compared with the control group. Sperm concentration, sperm motility, and normal head morphology were negatively correlated with the amount of CpG methylation. Sperm selected from the 90% gradient fraction exhibited less methylation than sperm from the 35% fraction.Conclusion(s)Patients with two types of male factor infertility display an increased abnormal methylation of CREM compared with control subjects. Increased methylation is associated with decreased semen quality, and sperm selected by density gradient centrifugation have less methylation. Further research is necessary to investigate whether epimutations can be found on other nonimprinted gene promoters as well.