Molecular Markers of Human Sperm Function

Objectives: Male factor infertility is poorly understood and our ability to evaluate the male contribution to a couple's infertility is very limited. The overarching goal of this project is to understand at the molecular level what functional activities in human sperm are required for successful fertilization leading to full term development. These findings will allow us to develop new methods to determine the impact of environmental exposures on sperm quality and male fertility. A sperm protein known as phospholipase C zeta (PLC zeta) initiates embryo development at fertilization. The primary objective of this study is to test the hypothesis that human PLC zeta activity correlates directly with the proportion of fertilized eggs that undergo early cleavage during an in vitro fertilization (IVF) cycle. Secondary objectives for the study are to generate preliminary data regarding the variability in sperm PLC zeta activity within and between individuals and to determine if there are clinical or laboratory correlates for sperm PLC zeta activity. Study population: The study population will consist of 178 infertile couples undergoing IVF procedures at Duke Fertility Center (DFC) from which we will obtain 154 evaluable couples for the study. Overall Design: An observational cohort study design will be used to assess the association of PLC zeta activity in the residual sperm from the sample used for an IVF cycle with the proportion of eggs per couple that undergo early cleavage during the same cycle. Infertile couples enrolling in an IVF treatment cycle at DFC will be approached for inclusion in the study. Consent will be obtained from both male and female partners, and historical medical information and information about their IVF cycle will be collected by chart review. Blood for isolation of serum and DNA will be collected only from the male partner for evaluation of hormone levels and genetic analyses related to infertility. On the day of the egg retrieval, residual sperm not needed for clinical purposes will be transported via courier to NIEHS. Sperm PLC zeta activity will be measured in the investigator's laboratory using an experimental bioassay. Sperm PLC zeta protein will be analyzed at the University of Massachusetts. Outcome Parameters: The primary outcome will be the proportion of embryos that undergo early cleavage. Secondary outcomes will include proportion of eggs fertilized, embryo development parameters, and pregnancy outcome. Association of PLC zeta activity with male partner's clinical or laboratory information will be determined. Variability in sperm PLC zeta activity will be determined within and between individuals.