Metabolic substrates exhibit differential effects on functional parameters of mouse sperm capacitation Public Deposited

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  • March 22, 2019
Creator
  • Goodson, Summer G.
    • Affiliation: School of Medicine, Department of Cell Biology and Physiology
Abstract
  • Sperm are capable of fertilization only after undergoing physiological changes in the female reproductive tract. These changes, known as capacitation, include the onset of a form of sperm motility called hyperactivation. Capacitation requires glycolysis, and sperm deficient in glycolytic enzymes are infertile due to defects in ATP levels and motility. Despite evidence of the importance of glycolysis in fertilization, several substrates not metabolized by this pathway have been shown to support sperm motility. To investigate the effects of substrate utilization on sperm functional changes required for fertilization, we first developed a method to evaluate patterns of mouse sperm motility. This tool, called CASAnova, is based on a multiclass support vector machines (SVM) model incorporating kinematic parameters of sperm motion generated by computerassisted sperm analysis (CASA). Over 2,000 tracks were visually classified into five patterns of motility, and CASA parameters associated with these tracks were incorporated into established SVM algorithms to generate four equations. These equations, integrated into a decision tree, sequentially sort tracks into progressive, intermediate, hyperactivated, slow, or weakly motile groups. CASAnova incorporates these equations into a program for the automatic classification of sperm motility profiles. Comparisons of motility profiles of capacitating versus non-capacitating sperm confirmed the ability of CASAnova to distinguish hyperactivated motility. Furthermore, CASAnova accurately classified sperm with severe motility defects and revealed differences in motility profiles of sperm from genetically diverse inbred strains. Our analyses indicate that CASAnova provides rapid and reproducible measurements of sperm motility. We utilized CASAnova in conjunction with other measurements of sperm function to investigate the metabolic requirements of mouse sperm during in vitro capacitation. Our results demonstrate that mouse sperm maintained comparable ATP levels and percent motility when metabolizing either glycolytic or nonglycolytic substrates. However, only glucose and mannose supported the full spectrum of events associated with capacitation. Analyses of sperm incubated with metabolic inhibitors indicate that sperm utilizing fructose are capable of hyperactivation if oxidative phosphorylation is uncoupled. Metabolomic analyses of sperm incubated with glucose or fructose revealed alterations in antioxidant metabolites, suggesting that changes in redox state may contribute to the differential abilities of these substrates to support hyperactivation.
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  • In Copyright
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  • "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Cell and Developmental Biology."
Advisor
  • O'Brien, Deborah A.
Degree
  • Doctor of Philosophy
Graduation year
  • 2011
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