Theses and Dissertations

Author

Sule Dogan

Issuing Body

Mississippi State University

Advisor

Memili, Erdogan

Committee Member

Gordon, Donna M.

Committee Member

Larson, Jamie

Committee Member

Ray, David A.

Date of Degree

1-1-2012

Document Type

Dissertation - Open Access

Major

Life Sciences/Genetics

Degree Name

Doctor of Philosophy

College

College of Agriculture and Life Sciences

Department

Department of Animal and Dairy Sciences

Abstract

The impacts of the paternal genome and proteins transferred to the oocyte through spermatozoa cannot be neglected during mammalian embryonic development. Studies over the past 40 years suggest that sperm chromatin alterations (such as DNA fragmentation induced by either chromatin condensation errors, apoptosis and/or oxidative stress) might be negatively associated with fertilization and early embryonic development [1, 2], [3] [4].However, precise molecular mechanisms by which sperm chromatin integrity and sperm proteins impact early embryonic development still remain unclear. Therefore, the objectives of this study were 1) determine DNA fragmentation induced by apoptosis its relationship with male fertility in spermatozoa from bulls with varying fertility, and 2) identify expression dynamics of Protamine 1 and examine chromatin structure in spermatozoa from bulls with varying fertility. To accomplish our goals we determined 1) the DNA damage, phosphatidylserine (PS) translocation, and expression of pro- and anti-apoptotic proteins (BAX and BCL-2) as well as 2) the expression and localization of Protamine 1 (PRM1) with chromatin condensation and protamination in sperm from bulls with varying fertility. Our results demonstrated that the most relevant fertility markers might be the percentage of necrotic spermatozoa detected by flow cytometry and live spermatozoa determined via eosin-nigrosin staining and that there was no relationship between apoptosis and male fertility. While BCL-2 was not expressed, BAX was identified in bovine spermatozoa. However, the expression of BAX did not differ among groups. In addition, defective chromatin condensation and protamination errors were significantly increased in sperm from low fertility bulls, while the expression of PRM1 was significantly abundant in high fertility bulls. Bull fertility was negatively correlated with protamination errors and defective chromatin condensation, and it was positively correlated with the expression of PRM1. We concluded that defective sperm DNA condensation, not abortive apoptosis, might be the major reason of male infertility in bulls and that sperm chromatin stability differs among bulls with varying fertility. Improper chromatin packaging during spermatogenesis might be caused by the limited expression and/or mislocalization of PRM1. Thus, inadequate chromatin dynamics were associated with bull infertility, which might lead improper fertilization.

URI

https://hdl.handle.net/11668/17683

Comments

male fertility||spermatozoa||protamine 1||apoptosis||DNA damage

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