Doctoral Dissertations

Date of Award

12-2003

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biochemistry and Cellular and Molecular Biology

Major Professor

Mary Ann Handel

Committee Members

Bruce McKee, John Koontz, Cymbeline Culiat, Cynthia Peterson

Abstract

Meiosis is the process that ensures the continued propagation of new organisms and is a source of genetic variability within a population. During meiotic prophase many dynamic rearrangements occur in the nucleus of the cell. These rearrangements include homologous chromosome pairing, recombination, synaptonemal complex breakdown, chromosome condensation and spindle assembly. The regulatory mechanisms behind these complex processes at the G2/MI transition have not been completely elucidated, preventing our complete understanding of the processes. The purpose of this work is to provide new insight to the events and players involved in the regulation of the G2/MI transition in mouse spermatocytes.

Part I will provide an overview of meiosis, focusing in particular on how little is known of the kinases regulating the first meiotic division of spermatogenesis. As a way to fill the gaps in our knowledge about what events occur, in what order they occur, and how they may be interrelated we used antibodies against various proteins involved in chromosome pairing, recombination, spindle assembly, and those that mediate the cell cycle and followed their localization by immunofluorescence. These results are presented in Part II and provide a framework for which both mechanisms of normal meiosis as well as mutant phenotypes can be monitored.

Part III focuses on elucidation of the participants involved in regulation of the first meiotic division in spermatogenesis, with particular attention given to the mitogen-activated protein kinases (MAPKs). Chemical inhibitors and mutant genetic mouse models were used to investigate the pathway leading to the activation of the MAPKs and their role in the G2/MI transition. The results suggest that spermatocytes may have a novel mechanism for MAPK activation and that this regulation may depend, directly or indirectly, on maturation promoting factor (MPF).

In Part IV the findings of collaborative projects with other laboratories analyzing the expression of chromosomal proteins and the characterization of meiotic mutants is discussed. These studies provide new information as to the players and their roles in sister chromatid cohesion (REC8, RAD21, SMC1, SMC1b, SMC3), recombination (mei1) and chromatin remodeling (H1a, H1t) during spermatogenesis.

Overall the findings reported in this dissertation will aid in our understanding of the meiotic G2/MI transition in mouse spermatocytes. Specifically in the final part of this dissertation, Part V, the landmarks of meiotic prophase and the players regulating the transition in males will be compared to those known to regulate the meiotic divisions in the female. These findings will shed new light onto the sexual dimorphisms that exist between the male and female meiotic divisions, but more importantly on the regulatory molecules involved at the G2/MI transition.

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