Institute for Biogenesis Research
University of Hawaii John A. Burns School of Medicine

Supported by IBR-COBRE (Center of Biomedical Research Excellence) IDeA Program
NCRR 5P20RR024206-01, NIGMS 8P20GM103457-05

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Name W. Steven Ward
Affiliation JABSOM
Position Professor
Degree Ph.D. (Vanderbilt University)
Phone 808-956-5189
Fax 808-956-7316
Address IBR, 1960 East-West Rd., UH-Manoa
Honolulu, HI 96822

Research projects:

The function and structure of mammalian sperm chromatin.

Description of research:

Our research is focused on the structure of mammalian sperm chromatin and how this is related to function. The main hypothesis that we have tested is that the sperm cell provided the newly developing embryo with more than just the genetic code in the DNA sequence; it also provides a three dimensional organization of the DNA that provides crucial information as to how to use the father's genetic code.

DNA is packaged very densely in the sperm nucleus in a manner that is different from any other cell type. Most of the histones are replaced by protamines, and the DNA is crystallized into dense toroids with roughly 50,000 bp of DNA, each. Protamine condensation protects the sperm DNA from damage from external insults, and prevents transcription or DNA replication from occurring. We have shown that one structural feature present in all other somatic cells is also retained in sperm chromatin – the organization of DNA into loop domains attached at their bases to the nuclear matrix. This organization is crucial to two aspects of sperm chromatin function. Shortly after fertilization, the protamines are removed from the sperm DNA and the chromatin is repackaged with histones. The DNA is then replicated, and we have demonstrated that this DNA synthesis requires the loop domain organization to be intact. On the other hand, spermatozoa have the ability to digest their own DNA through an apoptotic-like process in which the sperm DNA is degraded. This degradation occurs on the nuclear matrix.

Our current research efforts are focused on understanding how sperm chromatin structure is related to the events that occur shortly after fertilization and how the DNA packaging in the sperm cell contributes to embryonic development.

Selected Publications:

  • Ward, W. S., Partin, A. W., and Coffey, D. S.: DNA loop domains in mammalian spermatozoa. Chromos. 98:153-159, 1989.
  • Ward, W. S., and Coffey. D.S.: DNA packaging and organization in mammalian spermatozoa: comparison with somatic cells. Biol. Reprod. 44:569-574, 1991.
  • Ward, W. S.: DNA loop domain tertiary structure in mammalian spermatozoa. Biol. Reprod. 48:1193-1201, 1993.
  • Ward, W. S.: The structure of the sleeping genome: implications of sperm DNA organization for somatic cells. J. Cell. Biochem. 55:77-82 1994.
  • Nadel, B., de Lara, J., Finkernagel, S. W., and Ward, W. S.: Cell specific organization of the 5S rRNA gene cluster DNA loop domains in spermatozoa and somatic cells. Biol. Reprod. 53;1222-1228, 1995.
  • Ward, W. S., McNeil, J., de Lara, J,, Lawrence, J. "Localization of three genes in the hook shaped hamster sperm nucleus by fluorescent in situ hybridization." Biol. Reprod. 54(6):1271 1278, 1996.
  • Ward, W. S., Kimura, Y., Yanagimachi, R., "An Intact Sperm Nuclear Matrix May be Necessary for the Paternal Genome to Participate in Embryonic Development". Biology of Reproduction, 60:702-706, 1999.
  • Sotolongo, B., and Ward, W. S.. "DNA Loop Domain Organization: The Three Dimensional Genomic Code" Journal of Cellular Biochemistry, 35:23-26, 2001.
  • Klaus, A. V., McCarrey, J. R., Farkas, A., and Ward, W. S.. "Changes in DNA Loop Domain Structure During Spermatogenesis and Embryogenesis in the Syrian Golden Hamster". Biology of Reproduction, 64:1297-1306, 2001.
  • Mohar, I., Szczygiel, M. A., Yanagimachi, R., and Ward, W. S.. "Sperm Nuclear Halos Can Transform into Normal Chromosomes after Injection into Oocytes", Molecular Reproduction and Development, 63:416-420, 2002.
  • Sotolongo, B., Lino, E., and Ward, W. S.. "Hamster Spermatozoa have the Ability to Digest Their Own DNA", Biology of Reproduction, 69:2029-2035, 2003.
  • Ward, M. A., and Ward, W. S.. "A Model for the Function of Sperm DNA Degradation", Fertility, Reproduction and Development, Vol. 16 (5): 547-554, 2004.
  • Shaman, J. A., Prisztoka, R., and Ward, W. S.. Topoisomerase IIB and an Extracellular Nuclease Interact to Digest Sperm DNA in an Apoptotic-Like Manner. Biology of Reproduction, 75:741-748, 2006.
  • Yamauchi, Y., Shaman, J. A., and Ward, W. S.. "Topoisomerase II Mediated Breaks in Spermatozoa Cause the Specific Degradation of Paternal DNA in Fertilized Oocytes". Biology of Reproduction, 76:666-672, 2007.
  • Shaman, J. A., Yamauchi, Y., and Ward, W. S.. "The Sperm Nuclear Matrix is Required for Paternal DNA Replication". Journal of Cellular Biochemistry, 102:680-688, 2007.
  • Yamauchi, Y., Shaman, J. A., Boaz, S. M., and Ward, W. S.. "Paternal Pronuclear DNA Degradation is Functionally Linked to DNA Replication in Mouse Oocytes". Biology of Reproduction, 77:407-415, 2007.
  • Boaz, S. M., Dominguez, K., Shaman, J. A., and Ward, W. S.. "Mouse Spermatozoa Contain a Nuclease that Is Activated by Pretreatment with EGTA and Subsequent Calcium Incubation." Journal of Cellular Biochemistry, 103:1636-1645, 2008.
  • Yasuhiro, Y., Ward, M. A., and Ward, W. S.. "Asynchronous DNA Replication and Origin Licensing in the Mouse One Cell Embryo." Journal of Cellular Biochemistry, 107:214-223, 2009.
  • Dominguez, K., and Ward, W. S. "A Novel Nuclease Activity that is Activated by Ca2+ Chelated to EGTA.", Systems Biology in Reproductive Medicine, 55:193-199, 2009.
  • Ward, W. S., "Function of Sperm Chromatin Structural Elements in Fertilization and Development". Molecular Human Reproduction, 16:30-36, 2010.
  • Barratt, C. R. L., Aitken, R. J., de Boer, P., Björndahl, L., Carrell, D. T., Perreault, S. D., Kvist, U., Lewis, S. E. M., Perry, M. J., Ramos, L., Robaire, B., Ward, W. S., and Zini, A. “Sperm DNA: organization, protection and vulnerability: from basic science to clinical applications. A position report.” Human Reproduction, 25:824-838, 2010. PMC Journal – In Process
  • Ortega, M.A., Sil, P., and Ward, W. S. “Mammalian Sperm Chromatin as a Model for Chromatin Function in DNA Degradation and DNA Replication” Systems Biology in Reproductive Medicine, 57:43-49, 2011. PMCID: PMC3040494 [Available on 2012/2/1]
  • Yamauchi, Y., Shaman, J. A., and Ward, W. S. “Non-Genetic Contributions of the Sperm Nucleus to Embryonic Development”. Asian Journal of Andrology, 13:31-35, 2011. PMCID: PMC3015006 [Available on 2012/1/1].
  • Ward, W. S. “Regulating DNA Supercoiling: Sperm Points the Way”. Biology of Reproduction, 84:841-843, 2011. PMCID: PMC3080416.
  • Yamazaki, Y. and Ward, W. S. “A new Speedy/RINGO protein may help regulate male meiosis”. Asian Journal of Andrology, 13:363, 2011. PMCID: PMC3111482 [Available on 2012/5/1]
  • Dominguez, K., Arca, C.D.R., and Ward, W. S. “The Relationship between Chromatin Structure and DNA Damage in Mammalian Spermatozoa” In: Sperm Chromatin: Biological and Clinical Applications in Male Infertility and Assisted Reproduction, ed. by: Zini, A., and Agarwal, A., (Springer, New York, ISBN-13: 9781441917812) 2011.
  • Ortega, M. A., Marh, J., Alarcon, V., and Ward, W. S. “Unique Pattern of ORC2 and MCM7 Localization During DNA Replication Licensing in the Mouse Zygote". Biology of Reproduction, 87:62, 2012. PMCID:PMC3463414
  • Gawecka, J., and Ward, W. S. “Sperm Topoisomerase II May be Inherited by the Paternal Pronucleus”. In: Sperm Cell Research in the 21st Century: Historical Discoveries to New Horizons, ed. by M. Morisawa (Adthree Publishing Co., Ltd., Tokoyo), 2012. Preprint
  • Ward, W. S. “Isolation of sperm nuclei and nuclear matrices from the mouse, and other rodents”. Methods Mol. Biol. 927:437-444, 2013. PMCID: PMC3478126. Preprint
  • Gawecka, J.E., Marh, J., Ortega, M.A., Yamauchi, Y., Ward, M.A., and Ward, W. S. “Mouse Zygotes Respond to Severe Sperm DNA Damage by Delaying Paternal DNA Replication and Embryonic Development”. PLOS ONE, 8:1- 13, e56385 2013. PMCID: PMC3576397. Article
  • Ribas-Maynou, J., Gawecka, J. E., Benet, J., and Ward, W. S. “Double stranded DNA breaks hidden by the neutral Comet assay suggest a role of the sperm nuclear matrix in DNA integrity maintenance”. Molecular Human Reproduction, Apr;20(4):330-40, 2014. PMID: 24282283. Preprint
  • Nguyen, H., Ortega, M. A., Ko, M., Marh, J., Ward, W. S. “ORC4 Surrounds Extruded Chromatin in Female Meiosis”. Journal of Cellular Biochemistry, 116:778-786. PMID: 25502171 Preprint, Supplement
  • Gawecka, J.E, Ribas-Maynou, J., Benet, J., Ward, W. S. “A Model for the Control of DNA Integrity by the Sperm Nuclear Matrix”. Asian Journal of Andrology, 17:610-615, 2015. PMC Journal. Preprint
  • Ortega, M. A., Nguyen, H., Ward, W. S. “ORC Proteins in the Mammalian Zygote”. Cell and Tissue Research, in press, 2015. NIHMSID 721822. Preprint
  • Gawecka, J. E., Boaz, S., Kasperson, K., Nguyen, H., Evenson, D. P., Ward, W. S. “Luminal Fluid of Epididymis and Vas Deferens Contributes to Sperm Chromatin Fragmentation”. Human Reproduction, in press, 2015. PMC Journal. Preprint

Lab members

Hieu Nguyen
Graduate Student
Office 956-3969
Ryuei Sato
Graduate Student

Past lab members

Michael Ortega
Postdoctoral Research Fellow
University of Virginia