Ectoplasmic specializations are specialized actin-based adherens junctional complexes formed between Sertoli cells (basal ES) and between Sertoli and germ cells (apical ES) in the testis. The importance of this junctional complex is evidenced by the fact that the abnormal or disrupted ES contributes to spermatid sloughing and oligospermia in pathological conditions associated with reduced fertility potential, including varicocele, hyperprolactinemia, diabetes and idiopathic oligospermia. The greater vulnerability of ES to alterations in testis microenvironment compared to other junctional complexes, may explain why ES is frequently disrupted in cases of impaired fertility. Therefore, identification of the regulatory molecules and signaling pathways that regulate ES dynamics is vital to understand the mechanism of ES susceptibility and its role in male fertility. Recently, we have obtained interesting results that show signaling protein """"""""?-catenin, which is highly expressed in the germ cells and Sertoli cells, to play an important role in regulating germ cell- Sertoli cell adhesion at the apical ES. We show that spermatid-specific deletion of ?-catenin not only results in spermatid sloughing (indicating an impaired apical ES), but also causes significantly reduced sperm count and increased germ cell apoptosis. These results led us to hypothesize that ?-catenin is the molecular link that integrates Sertoli cells-germ cells adhesion with the signaling events essential for germ cell development and maturation. We propose that binding of germ cell ?-catenin-complex to ?-catenin-complex on Sertoli cell at the apical ES surface triggers a signaling cascade that regulates post-meiotic germ cell differentiation.
Two specific aims are proposed to test these hypotheses: (1) To elucidate the function of ?-catenin in germ cell development and maturation by targeting events at the apical ectoplasmic specialization. In this aim, we are targeting events only at the apical ES by generating protamine 1 (Prm1) promoter driven conditional knockout mice that specifically silences ?-catenin in elongating spermatids, thereby distinguishing the events occurring at the cell lumen from those at the base of the cell. (2) To identify and characterize signaling pathways regulated by ?-catenin at the apical ES. In this aim, by performing microarray analysis, we will identify and characterize ?-catenin regulated genes to determine specific roles they might play in regulating apical ES functions. The results of this basic research will provide insights into the role of ES in male fertility and a better understanding of the mechanisms by which defects in these critical pathways lead to infertility. In addition, these studies could lead to new insights for therapeutically compromising germ cell movement in the seminiferous epithelium, thereby disrupting spermatogenesis, as a novel approach to reversible male contraception.

Public Health Relevance

This study will provide insights into the role of ectoplasmic specialization (an actin-based junctional complex in the testis) in male fertility and a better understanding of the mechanisms by which defects in these critical pathways lead to infertility. In addition, these studies could lead to new approaches for therapeutically compromising germ cell movl ES) in the testis [19]. The importance of this junctional complex is evidenced by the fact that the abnormal or disrupted ES contributes to spermatid sloughing and oligospermia in pathological conditions associated with reduced fertility potential, including varicocele, hyperprolactinemia, diabetes and idiopathic oligospermia [13-16]. The greater vulnerability of ES to alterations in testis microenvironment compared to other junctional complexes, may explain why ES is frequently disrupted in cases of impaired fertility. Therefore, identification of the regulatory molecules and signaling pathways that regulate ES dynamics is vital to understand the mechanism of ES susceptibility and its role in male fertility. Recently, we have obtained interesting results that reveal signaling protein ?-catenin, which is highly expressed in the germ cells and Sertoli cells, to play an important role in germ cell-Sertoli cell adhesion at the apical ES. We show that spermatid-specific deletion of ?-catenin not only results in spermatid sloughing (indicating an impaired apical ES), but also causes significantly reduced sperm count and increased germ cell apoptosis. These results led us to hypothesize that ?-catenin is the molecular link that integrates Sertoli cell-germ cell adhesion with the signaling events essential for germ cell development and maturation. We propose that binding of germ cell ?-catenin-complex to ?-catenin-complex on Sertoli cell at the apical ES surface triggers a signaling cascade that regulates post-meiotic germ cell differentiation. Two specific aims are proposed to test these hypotheses: (1) To elucidate the function of ?-catenin in germ cell development and maturation by targeting events at the apical ectoplasmic specialization. In this aim, we are targeting events only at the apical ES by generating protamine 1 (Prm1) promoter driven conditional knockout mice that specifically silences ?-catenin in elongating spermatids, thereby distinguishing the events occurring at the cell lumen from those at the base of the cell. (2) To identify and characterize signaling pathways regulated by ?-catenin at the apical ES. In this aim, by performing gene expression analyses we will identify and characterize ?-catenin regulated genes to determine specific roles they might play in mediating apical ES functions. The results of this basic research will provide insights into the role of ES in male fertility and a better understanding of the mechanisms by which defects in these critical pathways lead to infertility. In addition, these studies could lead to new insights for therapeutically compromising germ cell movement in the seminiferous epithelium, thereby disrupting spermatogenesis, as a novel approach to reversible male contraception. Modified Public Health Relevance Section This study will provide insights into the role of ectoplasmic s

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
1R01HD057118-01A2
Application #
7654332
Study Section
Cellular, Molecular and Integrative Reproduction Study Section (CMIR)
Program Officer
Moss, Stuart B
Project Start
2009-09-30
Project End
2011-06-30
Budget Start
2009-09-30
Budget End
2010-06-30
Support Year
1
Fiscal Year
2009
Total Cost
$296,833
Indirect Cost
Name
University of Texas Health Science Center San Antonio
Department
Type
Schools of Medicine
DUNS #
800772162
City
San Antonio
State
TX
Country
United States
Zip Code
78229
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Chang, Yao-Fu; Lee-Chang, Jennifer S; Panneerdoss, Subbarayalu et al. (2011) Isolation of Sertoli, Leydig, and spermatogenic cells from the mouse testis. Biotechniques 51:341-2, 344
Chang, Yao-Fu; Lee-Chang, Jennifer S; Harris, Krystle Y et al. (2011) Role of ?-catenin in post-meiotic male germ cell differentiation. PLoS One 6:e28039