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4 October 2017 The developmental origin and compartmentalization of glutathione-s-transferase omega 2 isoforms in the perinuclear theca of eutherian spermatozoa
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Abstract

The perinuclear theca (PT) is a condensed, nonionic detergent resistant cytosolic protein layer encapsulating the sperm head nucleus. It can be divided into two regions: the subacrosomal layer, whose proteins are involved in acrosomal assembly during spermiogenesis, and the postacrosomal sheath (PAS), whose proteins are implicated in sperm–oocyte interactions during fertilization. In continuation of our proteomic analysis of the PT, we have isolated two prominent PT-derived proteins of 28 and 31 kDa from demembranated bovine sperm head fractions. These proteins were identified by mass spectrometry as isoforms of glutathione-s-transferase omega 2 (GSTO2). Immunoblots probed with anti-GSTO2 antibodies confirmed the presence of the GSTO2 isoforms in these fractions while fluorescent immunocytochemistry localized the isoforms to the PAS region of the bull, boar, and murid PT. In addition to the PAS labeling of GSTO2, the performatorium of murid spermatozoa was also labeled. Immunohistochemistry of rat testes revealed that GSTO2 was expressed in the third phase of spermatogenesis (i.e., spermiogenesis) and assembled in the PAS and perforatorial regions of late elongating spermatids. Fluorescent immunocytochemistry performed on murine testis cells co-localized GSTO2 and tubulin on the transient microtubularmanchette of elongating spermatids. These findings imply that GSTO2 is transported and deposited in the PAS region by the manchette, conforming to the pattern of assembly found with other PAS proteins. The late assembly of GSTO2 and its localization in the PAS suggests a role in regulating the oxidative and reductive state of covalently linked spermatid/sperm proteins, especially during the disassembly of the sperm accessory structures after fertilization.

Summary Sentence

GSTO2 isoforms are prominent constituents of the perinuclear theca and are deposited in this sperm head region by the microtubular-manchette late in spermiogenesis.

© The Authors 2017. Published by Oxford University Press on behalf of Society for the Study of Reproduction. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com
Lauren E Hamilton, Genevieve Acteau, Wei Xu, Peter Sutovsky, and Richard Oko "The developmental origin and compartmentalization of glutathione-s-transferase omega 2 isoforms in the perinuclear theca of eutherian spermatozoa ," Biology of Reproduction 97(4), 612-621, (4 October 2017). https://doi.org/10.1093/biolre/iox122
Received: 19 May 2017; Accepted: 29 September 2017; Published: 4 October 2017
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