[Frontiers in Bioscience 16, 1344-1363, January 1, 2011]

Markers of human sperm functions in the ICSI era

Monica Muratori, Sara Marchiani, Lara Tamburrino, Gianni Forti, Michaela Luconi, Elisabetta Baldi

Department of Clinical Physiopathology, Andrology and Endocrinology Units, Center of Excellence "DeNothe", University of Florence, Italy

TABLE OF CONTENTS

1. Abstract
2. Introductory remarks
2.1. Markers of sperm functions: is there still a role in the era of ICSI?
2.2. The new reference values of the WHO guidelines: which future for routine semen analysis?
3. Molecular markers of post-ejaculatory maturation events
3.1. Sperm capacitation
3.1.1. Intracellular pathways activated during capacitation
3.1.2. Intracellular calcium
3.1.3. Protein phosphorylation
3.2. Sperm Motility
3.2.1. Molecular bases of sperm motility
3.2.2. Structural and scaffolding proteins
3.2.3. Kkinase and phosphatase system
3.2.4. Calcium
3.2.5. Sperm motility and ART
4. Molecular markers of sperm-oocyte interaction
4.1. Sperm-zona binding and sperm-oocyte fusion
4.2. Sperm acrosome reaction
5. Other markers of sperm functions
5.1. Sperm DNA integrity
5.2. Post-translational modifications of proteins by ubiquitination and sumoylation
5.2.1. Ubiquitination
5.2.2. Sumoylation
6. Conclusions
7. Acknowledgement
8. References

1. ABSTRACT

The process of fertilization is crucial for species development and maintenance. Due to social and environmental problems, the number of infertile couples is increasing worldwide. Male and female factors contribute equally, and about 7% of men experiences problems in conceiving a child due to sperm defects. Assisted reproduction techniques (ARTs), including the most invasive intracytoplasmic sperm injection (ICSI), are the only available therapy for severe male factor infertility. Whether such techniques are associated with increased birth defects is still debated, and search for alternative options should go on. A better understanding of the molecular mechanisms involved in the process of fertilization may lead to the development of new pharmacological strategies to treat infertile men and new male contraceptive agents. In addition, in view of the low predictive power of routine semen analysis, new tests aimed to better predict the fertilization potential could be developed. The present review smmarizes current evidence of the molecular mechanisms involved in fertilization in human spermatozoa, with particular emphasis on the main post-ejaculatory maturation events, i.e. sperm