PARENT SESSION
SLIDE SESSION 16: FERTILIZATION
Chairs: William Breed, Nuch Tanphaichitr, Becky Sortini (Trainee)
Univ Ottawa-UCU Auditorium
1:30 PM-3:30 PM

PRESENCE OF MOUSE SPERM SURFACE ARYLSULFATASE-A AND ITS POTENTIAL ROLE IN MOUSE SPERM-EGG INTERACTION.

Tantibhedhyangkul, Julierut¹, Weerachatyanukul, Wattana ¹, Tanphaichitr, Nongnuj^1,2, ^{1 2}

ABSTRACT- We have shown that arylsulfatase-A (AS-A) is localized to the pig sperm surface and has a specific binding property to the homologous zona pellucida (ZP). In this report, the presence of AS-A on the mouse sperm surface and its potential role in mouse sperm-ZP binding were investigated. Indirect immunofluorescence of live mouse sperm using affinity-purified antiAS-A IgG localized AS-A to the convex ridge and the postacrosome of the mouse sperm head, the sites of ZP binding. Ultimately, immunogold electron microscopy revealed the presence of AS-A on the mouse sperm plasma membrane. Evaluation of the significance of sperm surface AS-A in the gamete interaction revealed that sperm pretreatment with antiAS-A IgG consistently inhibited sperm-ZP binding in vitro, in a concentration- dependent manner (reaching a maximum inhibition at 100 micrograms/ml). A similar inhibitory effect was observed when an equimolar antiAS-A Fab concentration was used instead of antiAS-A IgG, confirming that the observed inhibition was specific to AS-A but not to the steric hindrance of the divalent IgG. The inhibition of sperm-egg binding was not due to premature acrosome reaction, following the highest concentration (100 micrograms/ml) of antiAS-A IgG used in sperm-egg binding experiment. Moreover, sperm pretreatment with antiAS-A IgG did not affect the rate of ZP-induced acrosome reaction. Finally, purified pig AS-A conjugated with Alexa 430 could bind to the mouse ZP uniformly. These results strongly suggested that gamete surface AS-A played an important role in mouse sperm-ZP binding. Supported by CIHR grant MT 10366 and the Rockefeller Foundation.

KEY WORDS: arylsulfatase-A, sperm-egg interaction, zona pellucida