Sperm competent for fertilization can become capacitated, bind to the zona pellucida (ZP) of an egg in a specific manner, and complete acrosomal exocytosis. Failure to carry out these functions results in infertility. Although the interactions between the ZP and the plasma membrane overlying the sperm acrosome have been considered important for sperm-egg recognition and signaling, recent results have prompted a reassessment of current paradigms concerning these interactions. The broad, long-term objective of this proposal is to understand how the acrosome functions in fertilization. The general hypothesis is that acrosomal exocytosis leads to the exposure of acrosomal matrix proteins that become a de facto extracellular matrix (ECM) on the surface of the sperm head, and that the dynamic interactions of this newly-exposed sperm ECM with the egg ECM (the ZP) govern sperm-egg recognition and sperm penetration of the ZP.
Specific Aim 1 is to investigate acrosomal exocytosis using novel, sensitive analytical approaches to monitor OAM and PM fusion events in live sperm. The possibility will be examined that spontaneous acrosomal exocytosis is initiated during capacitation, a poorly defined maturation process that normally takes place within the female reproductive tract but can be mimicked experimentally. The hypothesis is that acrosomal exocytosis is initiated during capacitation and, in the absence of stimulatory factors, is a slow, discontinuous and Ca- dependent process. However, in the presence of stimulatory factors (e.g., ZP), acrosomal exocytosis is completed at an accelerated rate.
Specific Aim 2 is to characterize the interactions of the acrosomal matrix with the zonae pellucidae of mammalian eggs. Components of the AM will be studied to determine if they possess ligand-binding properties that enable them to bind to the ZP of unfertilized eggs.
Specific Aim 3 is to determine how structural properties and exocytosis-associated processing of AM components, e.g., sp56, affect their function. Structural determinants of sp56 will be studied to learn which domains are essential for binding of sperm to ZP glycoproteins by examining the structure-function relationships of mutated recombinant sp56 proteins. In addition, mutant mice null for the sp56 gene will be created to determine if sp56 is essential for fertilization. The proposed experiments will develop new technologies for the study of molecular mechanisms of acrosomal exocytosis. Results from these experiments may provide new ways to address the poor ZP binding of sperm from some human infertility patients and may offer new avenues for contraception through the disruption of purposeful sperm-ZP binding.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD041552-03
Application #
6874411
Study Section
Special Emphasis Panel (ZRG1-REN (01))
Program Officer
Rankin, Tracy L
Project Start
2003-05-28
Project End
2008-04-30
Budget Start
2005-05-01
Budget End
2006-04-30
Support Year
3
Fiscal Year
2005
Total Cost
$311,959
Indirect Cost
Name
University of Pennsylvania
Department
Obstetrics & Gynecology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Caballero-Campo, Pedro; Buffone, Mariano G; Benencia, Fabian et al. (2014) A role for the chemokine receptor CCR6 in mammalian sperm motility and chemotaxis. J Cell Physiol 229:68-78
Muro, Yuko; Buffone, Mariano G; Okabe, Masaru et al. (2012) Function of the acrosomal matrix: zona pellucida 3 receptor (ZP3R/sp56) is not essential for mouse fertilization. Biol Reprod 86:1-6
Buffone, Mariano G; Ijiri, Takashi W; Cao, Wenlei et al. (2012) Heads or tails? Structural events and molecular mechanisms that promote mammalian sperm acrosomal exocytosis and motility. Mol Reprod Dev 79:4-18
Kim, Kye-Seong; Foster, James A; Kvasnicka, Kevin W et al. (2011) Transitional states of acrosomal exocytosis and proteolytic processing of the acrosomal matrix in guinea pig sperm. Mol Reprod Dev 78:930-41
Buffone, Mariano G; Kim, Kye-Seong; Doak, Birgit J et al. (2009) Functional consequences of cleavage, dissociation and exocytotic release of ZP3R, a C4BP-related protein, from the mouse sperm acrosomal matrix. J Cell Sci 122:3153-60
Buffone, Mariano G; Rodriguez-Miranda, Esmeralda; Storey, Bayard T et al. (2009) Acrosomal exocytosis of mouse sperm progresses in a consistent direction in response to zona pellucida. J Cell Physiol 220:611-20
Buffone, Mariano G; Foster, James A; Gerton, George L (2008) The role of the acrosomal matrix in fertilization. Int J Dev Biol 52:511-22
Rodriguez-Miranda, Esmeralda; Buffone, Mariano G; Edwards, Scott E et al. (2008) Extracellular adenosine 5'-triphosphate alters motility and improves the fertilizing capability of mouse sperm. Biol Reprod 79:164-71
Buffone, Mariano G; Zhuang, Tiangang; Ord, Teri S et al. (2008) Recombinant mouse sperm ZP3-binding protein (ZP3R/sp56) forms a high order oligomer that binds eggs and inhibits mouse fertilization in vitro. J Biol Chem 283:12438-45
Cheng, Yong; Buffone, Mariano G; Kouadio, Martin et al. (2007) Abnormal sperm in mice lacking the Taf7l gene. Mol Cell Biol 27:2582-9

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