Differential expression of members of the E2F family of transcription factors in rodent testes

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Differential expression of members of the E2F family of transcription factors in rodent testes Kame S El-Darwish*1, Martti Parvinen2 and Jorma Toppari1 Address: 1Departments of Physiology and Pediatrics, University of Turku, Kiinamyllynkatu 10, FIN- 20520, Turku, Finland and 2Department of Anatomy, University of Turku, Kiinamyllynkatu 10, FIN- 20520, Turku, Finland Email: Kame S El-Darwish* - [email protected]; Martti Parvinen - [email protected]; Jorma Toppari - [email protected] * Corresponding author

Published: 05 December 2006 Reproductive Biology and Endocrinology 2006, 4:63

doi:10.1186/1477-7827-4-63

Received: 13 October 2006 Accepted: 05 December 2006

This article is available from: http://www.rbej.com/content/4/1/63 © 2006 El-Darwish et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract Background: The E2F family of transcription factors is required for the activation or repression of differentially expressed gene programs during the cell cycle in normal and abnormal development of tissues. We previously determined that members of the retinoblastoma protein family that interacts with the E2F family are differentially expressed and localized in almost all the different cell types and tissues of the testis and in response to known endocrine disruptors. In this study, the cell-specific and stage-specific expression of members of the E2F proteins has been elucidated. Methods: We used immunohistochemical (IHC) analysis of tissue sections and Western blot analysis of proteins, from whole testis and microdissected stages of seminiferous tubules to study the differential expression of the E2F proteins. Results: For most of the five E2F family members studied, the localizations appear conserved in the two most commonly studied rodent models, mice and rats, with some notable differences. Comparisons between wild type and E2F-1 knockout mice revealed that the level of E2F-1 protein is stage-specific and most abundant in leptotene to early pachytene spermatocytes of stages IX to XI of mouse while strong staining of E2F-1 in some cells close to the basal lamina of rat tubules suggest that it may also be expressed in undifferentiated spermatogonia. The age-dependent development of a Sertoli-cell-only phenotype in seminiferous tubules of E2F-1 knockout males corroborates this, and indicates that E2F-1 is required for spermatogonial stem cell renewal. Interestingly, E2F-3 appears in both terminally differentiated Sertoli cells, as well as spermatogonial cells in the differentiative pathway, while the remaining member of the activating E2Fs, E2F-2 is most concentrated in spermatocytes of mid to late prophase of meiosis. Comparisons between wildtype and E2F-4 knockout mice demonstrated that the level of E2F-4 protein displa