Tissue-specific roles of Fgfr2 in development of the external genitalia

An extra-genital cell population contributes to urethra closure during mouse penis development

Hypospadias, or incomplete closure of the urethra along the penis, is the second most common birth defect in the United States. We discovered a population of extra-genital mesenchymal cells that are essential for proper penile urethra closure in mouse embryos. This extra-genital population first appeared in the mesenchyme posterior to the hindlimb of the fetus after the onset of penis formation. These extra-genital cells, which transiently express a lineage marker Nr5a1, migrated centrally and colonized the penis bilateral to the urethra epithelium. Removal of the Nr5a1+ extra-genital cells, using a cell-type specific ablation model, resulted in severe hypospadias. The absence of extra-genital cells had the most significant impacts on another mesenchymal cells, the peri-urethra that were immediately adjacent to the Nr5a1+ extra-genital cells. Single cell mRNA sequencing revealed that the extra-genital cells extensively interact with the peri-urethra, particularly through Neuregulin 1, an epidermal Growth Factor (EGF) ligand. Disruption of Neuregulin 1 signaling in the ex-vivo slice culture system led to failure of urethra closure, recapitulating the phenotypes of extra-genital cell ablation. These results demonstrate that the Nr5a1+ extra-genital mesenchymal cells from outside of the fetal penis are indispensable for urethra closure through their interaction with the peri-urethra mesenchymal cells. This discovery provides a new entry point to understand the biology of penis formation and potential causes of hypospadias in humans.

A Genetics Study in the Foreskin of Boys with Hypospadias

Introduction

Hypospadias is a malformation of the genitourinary system in males, characterized by the placement of the urethral opening in the ventral surface of the penis. Although controversies continue about etiology, endocrine disrupting chemicals that disrupt normal endocrine signaling at the receptor or signal transduction level are thought to play an essential role in etiology. This study aimed to investigate the receptor gene expressions of the sex hormones and FGFR2, HOXA13, and TGFB1, which are considered to play an essential role in developing hypospadias.

Methods

The samples from the foreskin of 26 patients with hypospadias and 26 healthy children who underwent circumcision operations were collected. ESR1, AR, FGFR2, HOXA13, and TGFB gene expressions were investigated by real-time PCR in samples obtained during surgery.

Results

In the hypospadias group, ESR1 expression was increased (p = 0.013), and AR and FGFR2 expressions were decreased, which were found to be statistically significant (p = 0.027 and p = 0.003, respectively). There was no statistically significant difference between hypospadias and control groups in TGFBand HOXA13expression levels (p > 0.05).

Discussion

The results suggest that sex hormone receptors and FGFR2 may play an essential role in developing male external genital structures at the gene level. The defects in the expression of these genes can contribute to understanding the development of hypospadias.

Research advances in endometriosis-related signaling pathways: A review

Endometriosis (EM) is characterized by the existence of endometrial mucosa outside the uterine cavity, which causesinfertility, persistent aches, and a decline in women's quality of life. Both hormone therapies and nonhormone therapies, such as NSAIDs, are ineffective, generic categories of EM drugs. Endometriosis is a benign gynecological condition, yet it shares a number of features with cancer cells, including immune evasion, survival, adhesion, invasion, and angiogenesis. Several endometriosis-related signaling pathways are comprehensively reviewed in this article, including E2, NF-κB, MAPK, ERK, PI3K/Akt/mTOR, YAP, Wnt/β-catenin, Rho/ROCK, TGF-β, VEGF, NO, iron, cytokines and chemokines. To find and develop novel medications for the treatment of EM, it is essential to implicitly determine the molecular pathways that are disordered during EM development. Additionally, research on the shared pathways between EM and tumors can provide hypotheses or suggestions for endometriosis therapeutic targets.

Development of an in-vitro high-throughput screening system to identify modulators of genitalia development

Sexually dimorphic outgrowth and differentiation of the embryonic genital tubercles (GTs) give rise to the penis in males and the clitoris in females. Defects in androgen production or in response to androgen signaling can lead to various congenital penile anomalies in both mice and humans. Due to lack of a high-throughput screening system, identification of crucial regulators of GT sexual differentiation has been slow. To overcome this research barrier, we isolated embryonic GT mesenchymal (GTme) cells to model genitalia growth and differentiation in vitro. Using either a mechanical or fluorescence-activated cell sorting-assisted purification method, GTme cells were isolated and assayed for their proliferation using a microscopy and image analysis system, on a single cell level over time. Male and female GTme cells inherently exhibit different cellular dynamics, consistent with their in-vivo behaviors. This system allows for the rapid quantitative analyses of numerous drug treatments, and enables the discovery of potential genetic modulators of GT morphogenesis on a large scale. Using this system, we completed a 438-compound library screen and identified 82 kinase inhibitor hits. In mice, in-utero exposure to one such candidate kinase inhibitor, Cediranib, resulted in embryos with severe genitalia defects, especially in males. Gene silencing by RNAi was optimized in this system, laying the foundation for future larger-scale genetic screenings. These findings demonstrate the power of this novel high-throughput system to rapidly and successfully identify modulators of genitalia growth and differentiation, expanding the toolbox for the study of functional genomics and environmental factors.

Clinical application of a double-modified sulfated bacterial cellulose scaffold material loaded with FGFR2-modified adipose-derived stem cells in urethral reconstruction

BACKGROUND

Urethral stricture and reconstruction are one of the thorny difficult problems in the field of urology. The continuous development of tissue engineering and biomaterials has given new therapeutic thinking to this problem. Bacterial cellulose (BC) is an excellent biomaterial due to its accessibility and strong plasticity. Moreover, adipose-derived stem cells (ADSCs) could enhance their wound healing ability through directional modification.

METHODS

First, we used physical drilling and sulfonation in this study to make BC more conducive to cell attachment and degradation. We tested the relevant mechanical properties of these materials. After that, we attached Fibroblast Growth Factor Receptor 2 (FGFR2)-modified ADSCs to the material to construct a urethra for tissue engineering. Afterward, we verified this finding in the male New Zealand rabbit model and carried out immunohistochemical and imaging examinations 1 and 3 months after the operation. At the same time, we detected the potential biological function of FGFR2 by bioinformatics and a cytokine chip.

RESULTS

The results show that the composite has excellent repairability and that this ability is correlated with angiogenesis. The new composite in this study provides new insight and therapeutic methods for urethral reconstruction. The preliminary mechanism showed that FGFR2 could promote angiogenesis and tissue repair by promoting the secretion of Vascular Endothelial Growth Factor A (VEGFA) from ADSCs.

CONCLUSIONS

Double-modified sulfonated bacterial cellulose scaffolds combined with FGFR2-modified ADSCs provide new sight and treatments for patients with urethral strictures.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Spatiotemporal map of key signaling factors during early penis development

The formation of the external genitalia is a highly complex developmental process, considering it involves a wide range of cell types and results in sexually dimorphic outcomes. Development is controlled by several secreted signalling factors produced in complex spatiotemporal patterns, including the hedgehog (HH), bone morphogenic protein (BMP), fibroblast growth factor (FGF) and WNT signalling families. Many of these factors act on or are influenced by the actions of the androgen receptor (AR) that is critical to masculinisation. This complexity of expression makes it difficult to conceptualise patterns of potential importance. Mapping expression during key stages of development is needed to develop a comprehensive model of how different cell types interact in formation of external genitalia, and the global regulatory networks at play. This is particularly true in light of the sensitivity of this process to environmental disruption during key stages of development. The goal of this review is to integrate all recent studies on gene expression in early penis development to create a comprehensive spatiotemporal map. This serves as a resource to aid in visualising potentially significant interactions involved in external genital development.

Diagrams of published RNA and protein localisation data for key secreted signalling factors during early penis development.

Unconventional expression patterns are identified that suggest novel signalling axes during development.

Key research gaps and limitations are identified and discussed.

Single cell transcriptomic analysis of external genitalia reveals complex and sexually dimorphic cell populations in the early genital tubercle

External genital organs are among the most recognizable sexually dimorphic characters. The penis and clitoris develop from the embryonic genital tubercle, an outgrowth at the anterior margin of the cloaca that undergoes an extensive period of development in male and female embryos prior to the onset of sexual differentiation. In mice, differentiation into the penis and clitoris begins around embryonic day (E)15.5. Current knowledge of cell types that comprise the genital tubercle is limited to a few studies that have fate mapped derivatives of endoderm, mesoderm, and ectoderm. Here we use single cell transcriptomics to characterize the cell populations in the genital tubercles of male and female mouse embryos at E14.5, approximately 24 ​h before the onset of sexual differentiation, and we present the first comprehensive atlas of single-cell gene expression during external genital development. Clustering analyses and annotation using marker genes shows 19 distinct cell populations in E14.5 genital tubercles. Mapping of cell clusters to anatomical locations using in situ gene expression patterns revealed granularity of cellular specializations and positional identities. Although E14.5 precedes sexually dimorphic morphogenesis of the genital tubercle, comparative analysis of males and females identified sexual dimorphisms at the single cell level, including male-specific cell clusters with transcriptional signatures of smooth muscle and bone progenitors, both of which are known to be sexually dimorphic in adult genitalia, as well as immune cells. These results provide a new resource for classification of external genital cell types based on gene expression profiles and reveal sex-specific cellular specializations in the early genital tubercle.

Etiology of Hypospadias: A Comparative Review of Genetic Factors and Developmental Processes Between Human and Animal Models

Hypospadias is a congenital anomaly of the penis with an occurrence of approximately 1 in 200 boys, but the etiology of the majority of hypospadias has remained unknown. Numerous genes have been reported as having variants in hypospadias patients, and many studies on genetic deletion of key genes in mouse genital development have also been published. Until now, no comparative analysis in the genes related literature has been reported. The basic knowledge of penile development and hypospadias is mainly obtained from animal model studies. Understanding of the differences and similarities between human and animal models is crucial for studies of hypospadias. In this review, mutations and polymorphisms of hypospadias-related genes have been compared between humans and mice, and differential genotype–phenotype relationships of certain genes between humans and mice have been discussed using the data available in PubMed and MGI online databases, and our analysis only revealed mutations in seven out of 43 human hypospadias related genes which have been reported to show similar phenotypes in mutant mice. The differences and similarities in the processes of penile development and hypospadias malformation among human and commonly used animal models suggest that the guinea pig may be a good model to study the mechanism of human penile development and etiology of hypospadias.

Meeting report on the NIDDK/AUA Workshop on Congenital Anomalies of External Genitalia: challenges and opportunities for translational research

Congenital anomalies of the external genitalia (CAEG) are a prevalent and serious public health concern with lifelong impacts on the urinary function, sexual health, fertility, tumor development, and psychosocial wellbeing of affected individuals. Complications of treatment are frequent, and data reflecting long-term outcomes in adulthood are limited. To identify a path forward to improve treatments and realize the possibility of preventing CAEG, the National Institute of Diabetes and Digestive and Kidney Diseases and the American Urological Association convened researchers from a range of disciplines to coordinate research efforts to fully understand the different etiologies of these common conditions, subsequent variation in clinical phenotypes, and best practices for long term surgical success. Meeting participants concluded that a central data hub for clinical evaluations, including collection of DNA samples from patients and their parents, and short interviews to determine familial penetrance (small pedigrees), would accelerate research in this field. Such a centralized datahub will advance efforts to develop detailed multi-dimensional phenotyping and will enable access to genome sequence analyses and associated metadata to define the genetic bases for these conditions. Inclusion of tissue samples and integration of clinical studies with basic research using human cells and animal models will advance efforts to identify the developmental mechanisms that are disrupted during development and will add cellular and molecular granularity to phenotyping CAEG. While the discussion focuses heavily on hypospadias, this can be seen as a potential template for other conditions in the realm of CAEG, including cryptorchidism or the exstrophy-epispadias complex. Taken together with long-term clinical follow-up, these data could inform surgical choices and improve likelihood for long-term success.

Foxa1 and Foxa2 orchestrate development of the urethral tube and division of the embryonic cloaca through an autoregulatory loop with Shh

Congenital anomalies of external genitalia affect approximately 1 in 125 live male births. Development of the genital tubercle, the precursor of the penis and clitoris, is regulated by the urethral plate epithelium, an endodermal signaling center. Signaling activity of the urethral plate is mediated by Sonic hedgehog (SHH), which coordinates outgrowth and patterning of the genital tubercle by controlling cell cycle kinetics and expression of downstream genes. The mechanisms that govern Shh transcription in urethral plate cells are largely unknown. Here we show that deletion of Foxa1 and Foxa2 results in persistent cloaca, an incomplete separation of urinary, genital, and anorectal tracts, and severe hypospadias, a failure of urethral tubulogenesis. Loss of Foxa2 and only one copy of Foxa1 results in urethral fistula, an additional opening of the penile urethra. Foxa1/a2 participate in an autoregulatory feedback loop with Shh, in which FOXA1 and FOXA2 positively regulate transcription of Shh in the urethra, and SHH feeds back to negatively regulate Foxa1 and Foxa2 expression. These findings reveal novel roles for Foxa genes in development of the urethral tube and in division of the embryonic cloaca.

FGF8, FGF10 and FGF receptor 2 in foreskin of children with hypospadias: an analysis of immunohistochemical expression patterns and gene transcription

INTRODUCTION

Fibroblast growth factors (FGFs) play a crucial role in early embryogenesis of the genital tubercle and are involved in the development of hypospadias, affecting both endo- and ectodermally derived tissues. It was hypothesized that expression of FGFs could be qualitatively or quantitatively altered in skin of children with hypospadias.

OBJECTIVE

The objective of the study was to investigate expression patterns and transcription levels of FGF8, FGF10, and FGF Receptor 2 (FGFR2) in patients with hypospadias compared to normal controls.

PATIENTS AND METHODS

Skin samples from the ventro-lateral aspect of the foreskin of 32 patients with hypospadias (17 distal and 15 proximal, mean age 25 months) and 10 normal foreskin samples (mean age 77 months) were analyzed by immunohistochemistry. Staining, localization, and distribution of positive cells in epidermis and dermis were categorized independently by two researchers. Complementary DNA (cDNA) samples prepared from messenger RNA (mRNA) isolates of the same samples were analyzed by quantitative polymerase chain reaction (qPCR), comparing expressions of FGF8, FGF10, and FGFR2 with loading controls.

RESULTS

Patients with hypospadias consistently showed aberrant immunohistochemical staining patterns for FGF8/FGF10/FGFR2 in epidermis and dermis compared to patients without penile malformation (p < 0.01 for all markers). qPCR displayed no difference in expression levels on mRNA level (FGFR2 p = 0.44, FGF8 p = 0.77, and FGF10 p = 0.17) comparing normal foreskin with foreskin from patients with hypospadias. Figure.

DISCUSSION

The results point at an impact of FGF signaling during embryological development of hypospadias on skin, as an ectodermally derived tissue. Similar to the urethral development, this might be a result of mesothelial-epithelial interactions. The differing expression patterns in immunohistochemistry are not matched by a quantitative difference in marker expression on the mRNA level, putatively caused by post-translational modifications or alterations of the downstream pathway. FGFs, particularly FGF10 and FGFR2, are critically involved in wound healing.

CONCLUSIONS

There are significant differences in localization and distribution of FGF8, FGF10, and FGFR2 in comparisons of normal foreskin to foreskin of patients with hypospadias, whereas there is no difference in the quantitative expression of these markers on the mRNA level. This confirms the notion that penile skin is affected as well by the embryological aberrations during the embryogenesis of hypospadias.

Androgen receptor expression in preputial dartos tissue correlates with physiological androgen exposure in congenital malformations of the penis and in controls

INTRODUCTION

The androgen receptor (AR) plays an important role in the development of male genitalia, and impaired androgen signalling has been hypothesised to underlie congenital penile malformations (CPM) such as hypospadias. Previous studies exploring the role of AR expression in the development of CPM have yielded conflicting results.

OBJECTIVES

To assess AR expression in human foreskin of boys/men born with hypospadias, buried penis versus controls.

STUDY DESIGN

Foreskin samples of 428 boys and men undergoing primary penile surgery (198 controls, 197 hypospadias, and 33 buried penis) were collected between October 2013 and July 2018. AR staining was performed in all samples and semi-quantitatively scored by two researchers independently, using a modified quick score (mQuicks) that assesses the proportion and intensity of AR staining in smooth muscle fibres.

RESULTS

The interobserver variability of the mQuicks had a high level of agreement for the total score, as well as for the subscores. Two phases of high AR expression were observed in all groups, the first following the postnatal gonadotropin surge (i.e., mini-puberty) and the second in (pre-) puberty. No differences in AR expression were found in hypospadias or buried penis cases as compared to controls matched for age at time of surgery.

DISCUSSION

This study describes the physiological evolution in AR expression in the human foreskin of boys with CPM and explains the cause of the previously reported, conflicting results. Despite the very large cohort, the limitations of this study are the low number of cases younger than six months at the time of surgery and the lack of Tanner stages to correlate with the mQuicks in adolescents.

CONCLUSIONS

The mQuicks is a straightforward and informative tool to semi-quantitatively assess AR expression in the dartos tissue. In this study, AR expression in human foreskin shows a bimodal distribution in boys with CMP and controls, following physiological androgen exposure. No statistically significant difference in AR expression could be found between both groups. Whether other local mechanisms are affected by these physiological changes is currently unclear. However, strict age-matching should be considered when exploring the mechanisms underlying disturbed penile and urethral development in CMP.

Hormonal and Molecular Regulation of Phallus Differentiation in a Marsupial Tammar Wallaby

Congenital anomalies in phalluses caused by endocrine disruptors have gained a great deal of attention due to its annual increasing rate in males. However, the endocrine-driven molecular regulatory mechanism of abnormal phallus development is complex and remains largely unknown. Here, we review the direct effect of androgen and oestrogen on molecular regulation in phalluses using the marsupial tammar wallaby, whose phallus differentiation occurs after birth. We summarize and discuss the molecular mechanisms underlying phallus differentiation mediated by sonic hedgehog (SHH) at day 50 pp and phallus elongation mediated by insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein 3 (IGFBP3), as well as multiple phallus-regulating genes expressed after day 50 pp. We also identify hormone-responsive long non-coding RNAs (lncRNAs) that are co-expressed with their neighboring coding genes. We show that the activation of SHH and IGF1, mediated by balanced androgen receptor (AR) and estrogen receptor 1 (ESR1) signalling, initiates a complex regulatory network in males to constrain the timing of phallus differentiation and to activate the downstream genes that maintain urethral closure and phallus elongation at later stages.

Bmp4 is an essential growth factor for the initiation of genital tubercle (GT) outgrowth

The external genitalia are appendage organs outgrowing from the posterior body trunk. Murine genital tubercle (GT), anlage of external genitalia, initiates its outgrowth from embryonic day (E) 10.5 as a bud structure. Several growth factors such as fibroblast growth factor (FGF), Wnt and Sonic hedgehog (Shh) are essential for the GT outgrowth. However, the mechanisms of initiation of GT outgrowth are poorly understood. We previously identified bone morphogenetic protein (Bmp) signaling as a negative regulator for GT outgrowth. We show here novel aspects of Bmp4 functions for GT outgrowth. We identified the Bmp4 was already expressed in cloaca region at E9.5, before GT outgrowth. To analyze the function of Bmp4 at early stage for the initiation of GT outgrowth, we utilized the Hoxa3-Cre driver and Bmp4 ^flox/flox mouse lines. Hoxa3 ^Cre/+ ; Bmp4 ^flox/flox mutant mice showed the hypoplasia of GT with reduced expression of outgrowth promoting genes such as Wnt5a, Hoxd13 and p63, whereas Shh expression was not affected. Formation of distal urethral epithelium (DUE) marked by the Fgf8 expression is essential for controlling mesenchymal genes expression in GT and subsequent its outgrowth. Furthermore, Fgf8 expression was dramatically reduced in such mutant mice indicating the defective DUE formation. Hence, current results indicate that Bmp4 is an essential growth factor for the initiation of GT outgrowth independent of Shh signaling. Thus, Bmp4 positively regulates for the formation of DUE. The current study provides new insights into the function of Bmp signaling at early stage for the initiation of GT outgrowth.

Langerhans cells in hypospadias: an analysis of Langerin (CD207) and HLA-DR on epidermal sheets and full thickness skin sections

BACKGROUND

Hypospadias are among the most common genital malformations. Langerhans Cells (LCs) play a pivotal role in HIV and HPV infection. The migration of LC precursors to skin coincides with the embryonic period of hypospadias development and genetic alterations leading to the formation of hypospadias impact the development of ectodermally derived tissues. We hypothesized that this might be associated with a difference in frequency or morphology of epidermal and dermal LCs in hypospadias patients.

METHODS

A total of 43 patients from two centers were prospectively included into this study after parental consent and ethics approval. Epidermal and dermal sheets were prepared from skin samples of 26 patients with hypospadias, 13 patients without penile malformations and 4 patients with penile malformations other than hypospadias. Immunofluorescence staining of sheets was performed with anti-HLA-DR-FITC and anti-CD207/Langerin-A594 antibodies. Skin sections from 11 patients without penile malformation and 11 patients with hypospadias were stained for Langerin. Frequencies as well as morphology and distribution of epidermal and dermal LCs on sheets and sections were microscopically evaluated. Cell counts were compared by unpaired t-tests.

RESULTS

There was no difference in frequency of epidermal LCs, Neither on sheets (873 ± 61 vs. 940 ± 84LCs/mm², p = 0.522) nor on sections (32 ± 3 vs. 30 ± 2LCs/mm², p = 0.697). Likewise, the frequency of dermal LCs (5,9 ± 0,9 vs. 7.5 ± 1.3LCs/mm², p = 0.329) was comparable between patients with hypospadias and without penile malformation. No differences became apparent in subgroup analyses, comparing distal to proximal hypospadias (p = 0.949), younger and older boys (p = 0.818) or considering topical dihydrotestosterone treatment prior to surgery (p = 0.08). The morphology of the LCs was not different comparing hypospadias patients with boys without penile malformations.

CONCLUSIONS

LCs are present in similar frequencies and with a comparable morphology and distribution in patients with hypospadias as compared to children without penile malformations. This suggests that patients with hypospadias are not different from patients with normal penile development considering this particular compartment of their skin immunity.

LIM homeodomain transcription factor Isl1 affects urethral epithelium differentiation and apoptosis via Shh

Urethral hypoplasia, including failure of urethral tube closure, is one of the common phenotypes observed in hereditary human disorders, the mechanism of which remains unclear. The present study was thus designed to study the expression, functions, and related mechanisms of the LIM homeobox transcription factor Isl1 throughout mouse urethral development. Results showed that Isl1 was highly expressed in urethral epithelial cells and mesenchymal cells of the genital tubercle (GT). Functional studies were carried out by utilizing the tamoxifen-inducible Isl1-knockout mouse model. Histological and morphological results indicated that Isl1 deletion caused urethral hypoplasia and inhibited maturation of the complex urethral epithelium. In addition, we show that Isl1-deleted mice failed to maintain the progenitor cell population required for renewal of urethral epithelium during tubular morphogenesis and exhibited significantly increased cell death within the urethra. Dual-Luciferase reporter assays and yeast one-hybrid assays showed that ISL1 was essential for normal urethral development by directly targeting the Shh gene. Collectively, results presented here demonstrated that Isl1 plays a crucial role in mouse urethral development, thus increasing our potential for understanding the mechanistic basis of hereditary urethral hypoplasia.

Regulatory roles of epithelial-mesenchymal interaction (EMI) during early and androgen dependent external genitalia development

Development of external genitalia (ExG) has been a topic of long mystery in the field of organogenesis research. Early stage male and female of mouse embryos develop a common genital tubercle (GT) in the perineum whose outgrowth extends distally from the posterior cloacal regions. Concomitant with GT outgrowth, the cloaca is divided into urogenital sinus and anorectum by urorectal septum (URS) internally. The outgrowth of the GT is associated with the formation of endodermal epithelial urethral plate (UP) attached to the ventral epidermis of the GT. Such a common developmental phase is observed until around embryonic day 15.5 (E15.5) morphologically in mouse embryogenesis. Various growth factor genes, such as Fibroblast growth factor (Fgf) and Wnt genes are expressed and function during GT formation. Since the discovery of key growth factor signals and several regulatory molecules, elucidation of their functions has been achieved utilizing mouse developmental models, conditional gene knockout mouse and in vitro culture. Analyses on the phenotypes of such mouse models have revealed that several growth factor families play fundamental roles in ExG organogenesis based on the epithelial-mesenchymal interaction (EMI). More recently, EMI between developing urethral epithelia and its bilateral mesenchyme of later stages is also reported during subsequent stage of androgen-dependent male-type urethral formation in the mouse embryo. Mafb, belonging to AP-1 family and a key androgen-responsive mesenchymal gene, is identified and starts to be expressed around E14.5 when masculinization of the urethra is initiated. Mesenchymal cell condensation and migration, which are regulated by nonmuscle myosin, are shown to be essential process for masculinization. Hence, studies on EMI at various embryonic stages are important not only for early but also for subsequent masculinization of the urethra. In this review, a dynamic mode of EMI for both early and late phases of ExG development is discussed.

A loss of estrogen signaling in the aromatase deficient mouse penis results in mild hypospadias

Hypospadias is the abnormal opening of the urethra on the underside of the penis and occurs in approximately 1/125 live male births worldwide. The incidence rate of hypospadias has dramatically increased over the past few decades. This is now attributed, at least in part, to our exposure to endocrine-disrupting chemicals (EDCs) which alter the hormonal signals required for development of the penis. In humans androgens are the main drivers of fusion of the urethral folds to form the urethra within the shaft of the penis, a process required for termination of the urethra in its normal location at the tip of the penis. However, recent research has suggested that estrogen also plays a role in this process. To better understand how EDCs impact urethral development it is essential that we understand the normal function of hormones during development of the penis. To define the role of estrogen in urethral development we examined development of the penis in the aromatase (Cyp19a1) Knockout (ArKO) mouse strain in which endogenous estrogen production is completely ablated. We found that the ArKO penis had a mild hypospadias phenotype. The developing ArKO postnatal penis displayed an early disruption in preputial development, which likely causes the mild hypospadias observed in adults. Using qPCR, we found altered expression of keratin genes and key urethral patterning genes in response to the disrupted estrogen signaling. The hypospadias phenotype was almost identical to that reported for the estrogen receptor α (ERα) knockout confirming that ERα is the predominant receptor for mediating estrogen action during development of the mouse penis. Our results show that estrogen is required for normal prepucial development and placement of the mature urethral opening at the distal aspect of the penis. We also identified several genes which are potential downstream targets of estrogen during normal urethral closure. With this knowledge, we can now better understand how anti-estrogenic as well as estrogenic EDCs disrupt urethral closure to cause mild hypospadias in both mice and humans.

The efficacy of cisplatin on nasopharyngeal carcinoma cells may be increased via the downregulation of fibroblast growth factor receptor 2

Cisplatin is one of the primary compounds used in the treatment of nasopharyngeal carcinoma (NPC), and fibroblast growth factor receptor 2 (FGFR2) has emerged to be a promising target for treatment in various tumors. Therefore, the present study aimed to explore whether the expression levels of FGFR2 in NPC tissues and cell lines were altered, and whether the efficiency of cisplatin was increased following the downregulation of FGFR2. The downregulation of FGFR2 was achieved by transfection with a small interfering RNA against FGFR2. Tissues of patients with NPC were analyzed by immunohistochemistry. Cell viability was examined using a Cell Counting Kit‑8 assay. Cell cycle analysis was performed using flow cytometry. mRNA and protein levels were measured by reverse transcription quantitative polymerase chain reaction and western blot analysis, respectively. FGFR2 was observed to be overexpressed in cancer tissues of patients with NPC and in the NPC SUNE1, C666‑1, 6‑10B and HNE‑3 cell lines, and resulted in an unfavorable prognosis. Cisplatin treatment decreased cell viability and increased FGFR2 expression. The silencing of FGFR2 was demonstrated to augment the effects of cisplatin treatment, including decreasing the cell viability and inducing cell cycle arrest, which involved the increase and decrease of the durations of G1 and S phases, respectively, and a decrease in the expression levels of cyclin D1 and CDC25A, and increasing the rate of apoptosis via the intrinsic apoptosis pathway, as demonstrated by the upregulation of cleaved caspase‑3 and B‑cell lymphoma 2 (Bcl‑2)‑associated X protein and downregulation of Bcl‑2, in SUNE1 and C666‑1 cell lines. FGFR2 was overexpressed in the cancer tissues of patients with NPC and in NPC cell lines, resulting in an unfavorable prognosis. The downregulation of FGFR2 decreased cell viability via cell cycle arrest at G1 phase, and increased the efficacy of the cisplatin‑based induction of apoptosis through the intrinsic apoptosis pathway.

Androgen and Oestrogen Affect the Expression of Long Non-Coding RNAs During Phallus Development in a Marsupial

There is increasing evidence that long non-coding RNAs (lncRNAs) are important for normal reproductive development, yet very few lncRNAs have been identified in phalluses so far. Unlike eutherians, phallus development in the marsupial tammar wallaby occurs post-natally, enabling manipulation not possible in eutherians in which differentiation occurs in utero. We treated with sex steroids to determine the effects of androgen and oestrogen on lncRNA expression during phallus development. Hormonal manipulations altered the coding and non-coding gene expression profile of phalluses. We identified several predicted co-regulatory lncRNAs that appear to be co-expressed with the hormone-responsive candidate genes regulating urethral closure and phallus growth, namely IGF1, AR and ESR1. Interestingly, more than 50% of AR-associated coding genes and lncRNAs were also associated with ESR1. In addition, we identified and validated three novel co-regulatory and hormone-responsive lncRNAs: lnc-BMP5, lnc-ZBTB16 and lncRSPO4. Lnc-BMP5 was detected in the urethral epithelium of male phalluses and was downregulated by oestrogen in males. Lnc-ZBTB16 was downregulated by oestrogen treatment in male phalluses at day 50 post-partum (pp). LncRSPO4 was downregulated by adiol treatment in female phalluses but increased in male phalluses after castration. Thus, the expression pattern and hormone responsiveness of these lncRNAs suggests a physiological role in the development of the phallus.

Epithelial-mesenchymal transformation and apoptosis in rat urethra development

BackgroundTo examine the mechanism of urethral seam formation during embryonal development of rat urethra.MethodsTime-mated Sprague-Dawley rats were killed and the genital tubercles of male pups harvested on embryonic day (ED) 15, 16, 18, and 19. External morphology was observed under scanning electron microscope. Serial transverse sections were prepared to examine dynamic changes in the urethral seam morphology with hematoxylin-eosin staining, immunohistochemistry, transmission electron microscopy, and double immunofluorescence.ResultsBilateral outgrowth of urethral swelling followed by urethral plate fusion in the midline to form urethral seam was observed from ED 16 onwards. Coexpression of epithelial and mesenchymal markers was observed in several cells at the urethral seam; a few cells with coexpression of epithelial and apoptotic markers were also observed. Mesenchymal transformation of epithelial cells and apoptotic epithelial cells was observed under transmission electron microscope.ConclusionUrethral formation occurs by tubulogenesis, which initiates proximally and progresses distally. This is the first study to demonstrate epithelial-mesenchymal transformation and epithelial cell apoptosis in the urethral seam cells of fetal rats. These findings provide new insights into the mechanisms involved in embryonal development of the urethra.

Expression patterns of Fgf8 and Shh in the developing external genitalia of Suncus murinus

Reciprocal epithelial–mesenchymal interactions and several signalling pathways regulate the development of the genital tubercle (GT), an embryonic primordium of external genitalia. The morphology of the adult male external genitalia of the Asian house musk shrew Suncus murinus (hereafter, laboratory name: suncus) belonging to the order Eulipotyphla (the former order Insectivora or Soricomorpha) differs from those of mice and humans. However, the developmental process of the suncus GT and its regulatory genes are unknown. In the present study, we explored the morphological changes and gene expression patterns during the development of the suncus GT. Morphological observations suggested the presence of common (during the initial outgrowth) and species-specific (during the sexual differentiation of GT) developmental processes of the suncus GT. In gene expression analysis, fibroblast growth factor 8 (Fgf8) and sonic hedgehog (Shh), an indicator and regulator of GT development in mice respectively, were found to be expressed in the cloacal epithelium and the developing urethral epithelium of the suncus GT. This pattern of expression specifically in GT epithelium is similar to that observed in the developing mouse GT. Our results indicate that the mechanism of GT formation regulated by the FGF and SHH signalling pathways is widely conserved in mammals.

Modeling congenital disease and inborn errors of development in Drosophila melanogaster

Fly models that faithfully recapitulate various aspects of human disease and human health-related biology are being used for research into disease diagnosis and prevention. Established and new genetic strategies in Drosophila have yielded numerous substantial successes in modeling congenital disorders or inborn errors of human development, as well as neurodegenerative disease and cancer. Moreover, although our ability to generate sequence datasets continues to outpace our ability to analyze these datasets, the development of high-throughput analysis platforms in Drosophila has provided access through the bottleneck in the identification of disease gene candidates. In this Review, we describe both the traditional and newer methods that are facilitating the incorporation of Drosophila into the human disease discovery process, with a focus on the models that have enhanced our understanding of human developmental disorders and congenital disease. Enviable features of the Drosophila experimental system, which make it particularly useful in facilitating the much anticipated move from genotype to phenotype (understanding and predicting phenotypes directly from the primary DNA sequence), include its genetic tractability, the low cost for high-throughput discovery, and a genome and underlying biology that are highly evolutionarily conserved. In embracing the fly in the human disease-gene discovery process, we can expect to speed up and reduce the cost of this process, allowing experimental scales that are not feasible and/or would be too costly in higher eukaryotes.

Systematic Review to Compare Urothelium Differentiation with Urethral Epithelium Differentiation in Fetal Development, as a Basis for Tissue Engineering of the Male Urethra

BACKGROUND

Tissue-engineered (TE) urethra is desirable in men with urethral disease (stricture or hypospadias) and shortage of local tissue. Although ideally a TE graft would contain urethral epithelium cells, currently, bladder epithelium (urothelium) is widely used, but morphologically different. Understanding the differences and similarities of urothelium and urethral epithelium could help design a protocol for in vitro generation of urethral epithelium to be used in TE grafts for the urethra.

PURPOSE

To understand the development toward urethral epithelium or urothelium to improve TE of the urethra.

METHODS

A literature search was done following PRISMA guidelines. Articles describing urethral epithelium and bladder urothelium development in laboratory animals and humans were selected.

RESULTS

Twenty-nine studies on development of urethral epithelium and 29 studies on development of urothelium were included. Both tissue linings derive from endoderm and although adult urothelium and urethral epithelium are characterized by different gene expression profiles, the signaling pathways underlying their development are similar, including Shh, BMP, Wnt, and FGF. The progenitor of the urothelium and the urethral epithelium is the early fetal urogenital sinus (UGS). The urethral plate and the urothelium are both formed from the p63+ cells of the UGS. Keratin 20 and uroplakins are exclusively expressed in urothelium, not in the urethral epithelium. Further research has to be done on unique markers for the urethral epithelium.

CONCLUSION

This review has summarized the current knowledge about embryonic development of urothelium versus urethral epithelium and especially focuses on the influencing factors that are potentially specific for the eventual morphological differences of both cell linings, to be a basis for developmental or tissue engineering of urethral tissue.

Requirement for basement membrane laminin α5 during urethral and external genital development

Hypospadias, a congenital malformation of the penis characteristic of an abnormal urethral orifice, affects 1 in every 125 boys, and its incidence is rising. Herein we test the hypothesis that the basement membrane protein laminin α5 (LAMA5) plays a key role in the development of the mouse genital tubercle, the embryonic anlage of the external genitalia. Using standard histological analyses and electron microscopy, we characterized the morphology of the external genitalia in Lama5 knockout (LAMA5-KO) mouse embryos during both androgen-independent genital tubercle development and androgen-mediated sexual differentiation. We compared regulatory gene expression between control and LAMA5-KO by in situ hybridization. We also examined the epithelial structure of the mutant genital tubercle using immunofluorescence staining and histological analyses of semi-thin sections. We found that Lama5 was expressed in both ectodermal and endodermal epithelia of the cloaca. The LAMA5-KO displayed a profound external genital malformation in which the genital tubercle was underdeveloped with a large ectopic orifice at the proximal end. In older embryos, the urethra failed to form a tubular structure and was left completely exposed. These defects were not associated with a significant alteration in regulatory gene expression, but rather with a defective ectodermal epithelium and an abnormal disintegration of the cloacal membrane. We conclude that LAMA5 is required in the basement membrane to maintain normal architecture of the ventral ectoderm during genital tubercle development, which is essential for the formation of a tubular urethra. Perturbation of LAMA5, and possibly other basement membrane components, may cause hypospadias in humans.

Computational modeling and simulation of genital tubercle development

Hypospadias is a developmental defect of urethral tube closure that has a complex etiology involving genetic and environmental factors, including anti-androgenic and estrogenic disrupting chemicals; however, little is known about the morphoregulatory consequences of androgen/estrogen balance during genital tubercle (GT) development. Computer models that predictively model sexual dimorphism of the GT may provide a useful resource to translate chemical-target bipartite networks and their developmental consequences across the human-relevant chemical universe. Here, we describe a multicellular agent-based model of genital tubercle (GT) development that simulates urethrogenesis from the sexually-indifferent urethral plate stage to urethral tube closure. The prototype model, constructed in CompuCell3D, recapitulates key aspects of GT morphogenesis controlled by SHH, FGF10, and androgen pathways through modulation of stochastic cell behaviors, including differential adhesion, motility, proliferation, and apoptosis. Proper urethral tube closure in the model was shown to depend quantitatively on SHH- and FGF10-induced effects on mesenchymal proliferation and epithelial apoptosis-both ultimately linked to androgen signaling. In the absence of androgen, GT development was feminized and with partial androgen deficiency, the model resolved with incomplete urethral tube closure, thereby providing an in silico platform for probabilistic prediction of hypospadias risk across combinations of minor perturbations to the GT system at various stages of embryonic development.

The Genetic Basis of Baculum Size and Shape Variation in Mice

The rapid divergence of male genitalia is a preeminent evolutionary pattern. This rapid divergence is especially striking in the baculum, a bone that occurs in the penis of many mammalian species. Closely related species often display diverse baculum morphology where no other morphological differences can be discerned. While this fundamental pattern of evolution has been appreciated at the level of gross morphology, nearly nothing is known about the genetic basis of size and shape divergence. Quantifying the genetic basis of baculum size and shape variation has been difficult because these structures generally lack obvious landmarks, so comparing them in three dimensions is not straightforward. Here, we develop a novel morphometric approach to quantify size and shape variation from three-dimensional micro-CT scans taken from 369 bacula, representing 75 distinct strains of the BXD family of mice. We identify two quantitative trait loci (QTL) that explain ∼50% of the variance in baculum size, and a third QTL that explains more than 20% of the variance in shape. Together, our study demonstrates that baculum morphology may diverge relatively easily, with mutations at a few loci of large effect that independently modulate size and shape. Based on a combination of bioinformatic investigations and new data on RNA expression, we prioritized these QTL to 16 candidate genes, which have hypothesized roles in bone morphogenesis and may enable future genetic manipulation of baculum morphology.

Timing of androgen receptor disruption and estrogen exposure underlies a spectrum of congenital penile anomalies

Congenital penile anomalies (CPAs) are among the most common human birth defects. Reports of CPAs, which include hypospadias, chordee, micropenis, and ambiguous genitalia, have risen sharply in recent decades, but the causes of these malformations are rarely identified. Both genetic anomalies and environmental factors, such as antiandrogenic and estrogenic endocrine disrupting chemicals (EDCs), are suspected to cause CPAs; however, little is known about the temporal window(s) of sensitivity to EDCs, or the tissue-specific roles and downstream targets of the androgen receptor (AR) in external genitalia. Here, we show that the full spectrum of CPAs can be produced by disrupting AR at different developmental stages and in specific cell types in the mouse genital tubercle. Inactivation of AR during a narrow window of prenatal development results in hypospadias and chordee, whereas earlier disruptions cause ambiguous genitalia and later disruptions cause micropenis. The neonatal phase of penile development is controlled by the balance of AR to estrogen receptor α (ERα) activity; either inhibition of androgen or augmentation of estrogen signaling can induce micropenis. AR and ERα have opposite effects on cell division, apoptosis, and regulation of Hedgehog, fibroblast growth factor, bone morphogenetic protein, and Wnt signaling in the genital tubercle. We identify Indian hedgehog (Ihh) as a novel downstream target of AR in external genitalia and show that conditional deletion of Ihh inhibits penile masculinization. These studies reveal previously unidentified cellular and molecular mechanisms by which antiandrogenic and estrogenic signals induce penile malformations and demonstrate that the timing of endocrine disruption can determine the type of CPA.