Fkbp52 Regulates Androgen Receptor Transactivation Activity and Male Urethra Morphogenesis

Abstract

Hypospadias is a common birth defect in humans, yet its etiology and pattern of onset are largely unknown. Recent studies have shown that male mice with targeted ablation of FK506-binding protein-52 (Fkbp52) develop hypospadias, most likely due to actions of Fkbp52 as a molecular co-chaperone of the androgen receptor (AR). Here, we further dissect the developmental and molecular mechanisms that underlie hypospadias in Fkbp52-deficient mice. Scanning electron microscopy revealed a defect in the elevation of prepucial swelling that led to the onset of the ventral penile cleft. Interestingly, expression of Fkbp52 was highest in the ventral aspect of the developing penis that undergoes fusion of the urethral epithelium. Although in situ hybridization and immunohistochemical analyses suggested that Fkbp52 mutants had a normal urethral epithelium signaling center and epithelial differentiation, a reduced apoptotic cell index at ventral epithelial cells at the site of fusion and a defect of genital mesenchymal cell migration were observed. Supplementation of gestating females with excess testosterone partially rescued the hypospadic phenotype in Fkbp52 mutant males, showing that loss of Fkbp52 desensitizes AR to hormonal activation. Direct measurement of AR activity was performed in mouse embryonic fibroblast cells treated with dihydrotestosterone or synthetic agonist R1881. Reduced AR activity at genes controlling sexual dimorphism and cell growth was found in Fkbp52-deficient mouse embryonic fibroblast cells. However, chromatin immunoprecipitation analysis revealed normal occupancy of AR at gene promoters, suggesting that Fkbp52 exerts downstream effects on the transactivation function of AR. Taken together, our data show Fkbp52 to be an important molecular regulator in the androgen-mediated pathway of urethra morphogenesis.Male external genital development in mammals is composed of distinct hormone-independent and hormone-dependent stages (1-3). The first phase (androgen-independent) is characterized by initial patterning and outgrowth of genitourinary structures in both male and female early embryos (embryonic day (E)10.5-E13.5 in the mouse). In males, the second phase (androgen-dependent) involves further outgrowth and differentiation of the glans penis, closure of the urethral fold (urethral epithelium remodeling) and scrotal development. Insufficient or altered hormonal signaling during development leads to many birth defects in the reproductive system, including hypospadias (4, 5). Hypospadias is a common birth defect in humans, in which altered urethral epithelial fusion causes ectopic openings at the ventral surface of the male external tubercle. Hypospadias is thought to result from androgen insufficiency or insensitivity. However, most cases of hypospadias have no clear link to defects in androgen production or androgen receptor (AR) 3 mutations (5). Fkbp52 and Fkbp51 are the best known of several tetratricopeptide repeat proteins that co-chaperone steroid receptors, including AR, progesterone receptor, and...

Computational modeling and simulation of genital tubercle development

“…Prior to sexual differentiation, GT development is directed by a number of signaling pathways, including SHH/IHH, FGF, BMP, HOX, WNT, RAR/RXR, and ephrin/EphB2 [3,[8][9][10][11][12][13][14][15]. Subsequently, the GT develops into a male or female phenotype depending on androgen production from the fetal testis [16][17][18][19] and estrogen production from maternal and other sources [20][21][22][23]. In human populations, an increased risk of hypospadias has been associated with single nucleotide polymorphisms (SNPs) in the SHH and FGF pathways [24,25].…”

“…The latter follows from prenatal exposure to environmental chemicals that may alter endocrine balance in the developing fetus, such as bisphenol A, flutamide, phthalates, and vinclozolin [26][27][28]. Although disruption of androgen-responsive pathways is a primary cause of hypospadias [29][30][31], knocking out morphogenetic signaling pathways such as SHH/IHH or FGF10 in mice causes profound changes in GT development, including changes in epithelial structure [32], suppression of mesenchymal proliferation, and the distribution of programmed cell death (apoptosis) [3,10,16,18]. Still, relatively little is known about the morphoregulatory consequences of androgen/estrogen balance during GT development [3,[32][33][34][35].…”

Androgen Regulates Dimorphic F-Actin Assemblies in the Genital Organogenesis

“…Several genes have been identified as essential regulators of male-and female-type reproductive organ formation [Miyagawa et al, 2009;Chen et al, 2010;Chen et al, 2011;Suzuki et al, 2014]. However, the cel-lular level of differentiation, particularly mesenchymal characters in the male-and female-type genital organ formation processes remain unelucidated.…”

“…Mesenchymally-derived androgen signaling is indispensable for the formation of the penile urethra [Miyagawa et al, 2009]. Genetic and molecular mechanisms involved in androgen driven formation of the penile urethra have been studied [Yong et al, 2007;Miyagawa et al, 2009;Chen et al, 2010]. However, the mode of androgen actions regulating cellular differentiation of urethral mesenchymal cells (UMCs) in ventral GT remains to be elucidated.…”

FKBP52 and Its Role of in the DNA Damage Repair

“…Male FKBP52-null mice show infertility and reduced AR activity indicating that FKBP52 is required for proper function of the AR (H. Chen et al, 2010;Cheung-Flynn et al, 2005;Yong et al, 2007).…”