The t complex in the mouse affects the function of sperm in fertilization. Sperm carrying a t complex (t sperm) from t/+ mice fertilize most or all oocytes. We have recently shown that this apparent advantage of t sperm in fertilization is due to the dysfunction of sperm not carrying a t complex (+ sperm) from the same male. The mechanism by which + sperm become defective, and the specific abnormalities which prevent them from participating in fertilization, are not known. We have shown that sperm from t/+ mice (mutant sperm), after several hours in vitro, develop a unique type of non-progressive motility called """"""""dancing."""""""" We now have preliminary evidence that mutant sperm also begin hyperactivation (HA) sooner than sperm from congenic +/+ mice (normal sperm). Thus mutant sperm may have several motility defects. Our preliminary evidence indicates that the timing of capacitation (CAP) is similar in mutant and normal sperm, implying that HA occurs earlier than CAP in mutant sperm. If so, the t complex provides a unique system in which to study the relationship between HA and CAP. The overall objective of this proposal is to characterize the abnormalities in motility of mutant sperm, using the novel quantitative motility parameters we have developed to measure various aspects of translational (whole-sperm) movement in individual mouse sperm; to determine the relationship of the motility abnormalities to CAP; and to explore several approaches to investigating the mechanism(s) causing the abnormal motility. Specifically, we will determine the kinetics of HA, CAP and dancing in mutant sperm, and determine the factors upon which each of these processes is dependent. We will also probe the subcellular site of the cause of the defective motility and determine whether dancing or the early onset of HA is dependent on the other known defect of mutant sperm, elevated surface galactosyl transferase activity. The proposed studies will increase our understanding of how the t complex affects sperm motility, and how the t complex affects HA and CAP, sperm functions essential for fertilization. These studies may also provide clues to the cause of the abnormal motility. Since it appears that HA is uncoupled from CAP in mutant sperm, these experiments may also contribute to our knowledge of the relationship between HA and CAP in normal sperm.
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