The Wilms tumor gene, Wt1, maintains testicular cord integrity by regulating the expression of Col4a1 and Col4a2.

Wt1 is specifically expressed in Sertoli cells in the developing testis. A previous study has demonstrated that Wt1 plays a critical role in maintaining the integrity of testicular cords. However, the underlying mechanism is unclear. In this study, we found that the laminin-positive basal lamina lining the testicular cords was fragmented and completely absent in some areas of Wt1(-/flox); Amh-Cre testes, indicating that the testicular cord disruption can be attributed to the breakdown of the basement membrane. To explore the molecular mechanism underlying this effect, we examined the expression of cell adhesion molecules (CAMs) and testicular cord basal lamina components by real-time RT-PCR, Western blotting, and immunostaining. Compared with control testes, the expression of CAMs (such as E-cadherin, N-cadherin, claudin11, occludin, beta-catenin, and ZO-1) was not obviously altered in Wt1(-/flox); Amh-Cre testes. However, the mRNA level of Col4a1 and Col4a2 was significantly decreased in Wt1-deficient testes. Immunostaining assays further confirmed that the collagen IV protein levels were dramatically reduced in Wt1(-/flox); Amh-Cre testes. Moreover, luciferase and point mutation analyses revealed that the Col4a1 and Col4a2 promoters were additively transactivated by WT1 and SOX9. Given this finding and previous results showing that SOX9 expression declines rapidly after Wt1 deletion, we conclude that the loss of Wt1 in Sertoli cells results in the downregulation of the important basal lamina component, which in turn causes the breakdown of the basal lamina and subsequent testicular cord disruption.

The Heat-Induced Reversible Change in the Blood-Testis Barrier (BTB) Is Regulated by the Androgen Receptor (AR) via the Partitioning-Defective Protein (Par) Polarity Complex in the Mouse.

Scrotal hypothermia is essential for normal spermatogenesis, and temporal heat stress causes a reversible disruption of the blood-testis barrier (BTB). Previous studies have shown that AR expression in primary monkey Sertoli cells (SCs) was dramatically reduced after temporary heat treatment. However, the mechanisms underlying the heat-induced reversible disruption of the BTB, including whether it is directly regulated by the AR, remain largely unknown. In this study, we demonstrated that the AR acts upstream to regulate the heat-induced reversible change in the BTB in mice. When the AR was overexpressed in SCs using an adenovirus, the heat stress-induced down-regulation of BTB-associated proteins (Zonula occludens-1 (ZO-1), N-Cadherin, E-Cadherin, α-Catenin, and ß-Catenin) was partially rescued. AR knockdown by RNAi or treatment with flutamide (an AR antagonist) in SCs inhibited the recovery of BTB-associated protein expression after 43°C heat treatment for 30 min. The results of an in vivo AR antagonist injection experiment further showed that the recovery of BTB permeability induced by temporal heat stress was regulated by the AR. Furthermore, we observed that the co-localization and interactions of partitioning-defective protein (Par) 6-Par3-aPKC-Cdc42 polarity complex components were disrupted in both AR-knockdown and heat-induced SCs. AR overexpression in SCs prevented the disruption of these protein-protein interactions after heat treatment. AR knockdown or treatment with flutamide in SCs inhibited the restoration of these protein-protein interactions after heat treatment compared with heat treatment alone. Together, these results demonstrate that the AR plays a crucial role in the heat-induced reversible change in BTB via the Par polarity complex.

Wnt/ß-catenin signaling regulates follicular development by modulating the expression of Foxo3a signaling components.

Wnt signaling is an evolutionarily conserved pathway that regulates cell proliferation, differentiation and apoptosis. To investigate the possible role of Wnt signaling in the regulation of ovarian follicular development, secondary follicles were isolated and cultured in vitro in the presence or absence of its activator (LiCl or Wnt3a) or inhibitor (IWR-1). We have demonstrated that activation of ß-catenin signals by activators dramatically suppressed follicular development by increasing granulosa cell apoptosis and inhibiting follicle steroidogenesis. In contrast, inhibition of Wnt signaling by IWR-1 was observed with better developed follicles and increased steroidogenesis. Further studies have shown that the transcription factor Forkhead box O3a (Foxo3a) and its downstream target molecules were modulated by the activators or the inhibitor. These findings provide evidence that Wnt signaling might negatively regulate follicular development potentially through Foxo3a signaling components.

Expression of inhibin-alpha is regulated synergistically by Wilms' tumor gene 1 (Wt1) and steroidogenic factor-1 (Sf1) in sertoli cells.

Wt1 encodes a zinc finger nuclear transcriptional factor, which is specifically expressed in testicular Sertoli cells and knockdown of Wt1 in Sertoli cells causes male mice subfertility. However, the underlying mechanism is still unclear. In this study, we found that expression of inhibin-α is significantly reduced in Wt1-deficient Sertoli cells. Luciferase assays using the inhibin-α promoter indicated that the inhibin-α promoter is transactivated by the Wt1 A, and B isoforms (-KTS), but not the C, and D isoforms (+KTS). Analysis of the Wt1 responsive element of the inhibin-α promoter region using site-directed mutagenesis showed that the nucleotides between -58 and -49 are essential for Wt1-dependent transactivation of the inhibin-α promoter. ChIP assays indicated that Wt1 directly interacts with the inhibin-α promoter. In addition, the inhibin-α promoter is activated synergistically by Wt1 and Sf1. Mutation of the ligand binding domain (LBD) of Sf1 (residues 235-238) completely abolished the synergistic action between Wt1 and Sf1, but did not affect the physical interaction between these two proteins, suggesting that other factor(s) may also be involved in the regulation of inhibin-α in Sertoli cells. Further studies demonstrated that ß-catenin enhances the synergistic activation of Wt1 and Sf1 on the inhibin-α promoter. Given the fact that inhibin-α, a subunit of inhibin, is known to be involved in the regulation of spermatogenesis and testicular steroidogenesis, this study reveals a new regulatory mechanism of inhibin-α in Sertoli cells and also sheds light on the physiological functions of Wt1 in gonad development and spermatogenesis.

Notch signaling is involved in ovarian follicle development by regulating granulosa cell proliferation.

Notch signaling is an evolutionarily conserved pathway, which regulates cell proliferation, differentiation, and apoptosis. It has been reported that the members of Notch signaling are expressed in mammalian ovaries, but the exact functions of this pathway in follicle development is still unclear. In this study, primary follicles were cultured in vitro and treated with Notch signaling inhibitors, L-658,458 and N-[N-(3,5-Difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT). We found that the cultured follicles completely stopped developing after L-658,458 and DAPT treatment, most of the granulosa cells were detached, and the oocytes were also degenerated with condensed cytoplasma. Further studies demonstrated that the proliferation of granulosa cells was dependent on the Notch signaling. L-658,458 and DAPT treatment inhibited proliferation of in vitro cultured primary granulosa cells and decreased the expression of c-Myc. Lentivirus mediated overexpression of Notch intracellular domain 2, and c-Myc could promote the proliferation of granulosa cells and rescue the growth inhibition induced by L-658,458 and DAPT. In conclusion, Notch signaling is involved in follicular development by regulating granulosa cell proliferation.

Testosterone induces redistribution of forkhead box-3a and down-regulation of growth and differentiation factor 9 messenger ribonucleic acid expression at early stage of mouse folliculogenesis.

Increasing evidence has shown that excess androgen may be a main cause of polycystic ovary syndrome (PCOS). However, the molecular mechanism of androgen action on the ovary is unclear. To investigate the possible impacts of androgen on early follicular development, neonatal mouse ovaries mainly containing primordial follicles were cultured with testosterone. We demonstrated that the number of primary follicles was increased after 10 d culture with testosterone treatment via phosphatidylinositol 3-kinase/Akt pathway. Androgen induced Forkhead box (Foxo)-3a activation, and translocation of Foxo3a protein from oocyte nuclei to cytoplasm, which might be a key step for primordial follicle activation. Interestingly, testosterone was also capable of down-regulating growth and differentiation factor-9 expression via its receptor. In summary, we infer that intraovarian excess androgen in PCOS might result in excess early follicles by inducing oocyte Foxo3a translocation and follicular arrest by down-regulating growth and differentiation factor-9 expression.

Acrosome formation-associated factor is involved in fertilization.

OBJECTIVE: To investigate the effects of a novel acrosome formation-associated factor (Afaf) on fertilization by its regulation of acrosomal exocytosis and endosomal trafficking. DESIGN: Controlled laboratory study. SETTING: Institution-affiliated state key laboratory. SUBJECTS: ICR mice. INTERVENTION(S): Sperm penetration assay and in vitro fertilization experiment were performed to study the effects of the Afaf antibody on acrosome reaction and fertilization. Acrosome exocytosis (AE) with streptolysin O (SLO) permeabilization was conducted to test the Afaf's action in calcium events. Colocalization and coimmunoprecipitation was done to determine the interaction between Afaf and SNAP25 (synaptosome-associated protein of 25,000 daltons). Transferrin (Tf) uptake assay was performed to demonstrate the impact of Afaf on endosomal pathway. RNAi was used to rescue the inhibition of Afaf on Tf uptake. MAIN OUTCOME MEASURE(S): Number of penetrated sperms, in vitro fertilization rate. Acrosomal exocytosis index, relative Tf fluorescence. RESULT(S): The Afaf antibodies were capable of significantly inhibiting sperm penetration of the eggs, therefore reducing the rate of in vitro fertilization. Acrosome formation-associated factor was involved in calcium-triggered AE by acting upstream of the calcium efflux from the acrosome inside. Acrosome formation-associated factor might exert an interaction with SNAP25, which is a crucial component in both exocytosis and endosomal trafficking. Acrosome formation-associated factor was also involved in the endocytic pathway by down-regulating Tf endocytosis in the HeLa cells, and the miRNA-mediated RNAi could rescue this alternation induced by Afaf. CONCLUSION(S): Acrosome formation-associated factor might play an important role in membrane trafficking during acrosome formation and participate in fertilization.