Hoxa-10 deficient male mice exhibit abnormal development of the accessory sex organs

Male reproductive phenotypes of genetically altered laboratory mice (Mus musculus): a review based on pertinent literature from the last three decades

Laboratory mice (Mus musculus) are preferred animals for biomedical research due to the close relationship with humans in several aspects. Therefore, mice with diverse genetic traits have been generated to mimic human characteristics of interest. Some genetically altered mouse strains, on purpose or by accident, have reproductive phenotypes and/or fertility deviating from wild-type mice. The distinct reproductive phenotypes of genetically altered male mice mentioned in this paper are grouped based on reproductive organs, beginning with the brain (i.e., the hypothalamus and anterior pituitary) that regulates sexual maturity and development, the testis where male gametes and sex steroid hormones are produced, the epididymis, the accessory sex glands, and the penis which involve in sperm maturation, storage, and ejaculation. Also, distinct characteristics of mature sperm from genetically altered mice are described here. This repository will hopefully be a valuable resource for both humans, in terms of future biomedical research, and mice, in the aspect of the establishment of optimal sperm preservation protocols for individual mouse strains.

Characterization of the human fetal gonad and reproductive tract by single-cell transcriptomics

During human fetal development, sex differentiation occurs not only in the gonads but also in the adjacent developing reproductive tract. However, while the cellular composition of male and female human fetal gonads is well described, that of the adjacent developing reproductive tract remains poorly characterized. Here, we performed single-cell transcriptomics on male and female human fetal gonads together with the adjacent developing reproductive tract from first and second trimesters, highlighting the morphological and molecular changes during sex differentiation. We validated different cell populations of the developing reproductive tract and gonads and compared the molecular signatures between the first and second trimesters, as well as between sexes, to identify conserved and sex-specific features. Together, our study provides insights into human fetal sex-specific gonadogenesis and development of the reproductive tract beyond the gonads.

HOXA10 promotes Gdf5 expression in articular chondrocytes

Growth differentiation factor 5 (GDF5), a BMP family member, is highly expressed in the surface layer of articular cartilage. The GDF5 gene is a key risk locus for osteoarthritis and Gdf5-deficient mice show abnormal joint development, indicating that GDF5 is essential in joint development and homeostasis. In this study, we aimed to identify transcription factors involved in Gdf5 expression by performing two-step screening. We first performed microarray analyses to find transcription factors specifically and highly expressed in the superficial zone (SFZ) cells of articular cartilage, and isolated 11 transcription factors highly expressed in SFZ cells but not in costal chondrocytes. To further proceed with the identification, we generated Gdf5-HiBiT knock-in (Gdf5-HiBiT KI) mice, by which we can easily and reproducibly monitor Gdf5 expression, using CRISPR/Cas9 genome editing. Among the 11 transcription factors, Hoxa10 clearly upregulated HiBiT activity in the SFZ cells isolated from Gdf5-HiBiT KI mice. Hoxa10 overexpression increased Gdf5 expression while Hoxa10 knockdown decreased it in the SFZ cells. Moreover, ChIP and promoter assays proved the direct regulation of Gdf5 expression by HOXA10. Thus, our results indicate the important role played by HOXA10 in Gdf5 regulation and the usefulness of Gdf5-HiBiT KI mice for monitoring Gdf5 expression.

What snakes and caecilians have in common? Molecular interaction units and the independent origins of similar morphotypes in Tetrapoda

Developmental pathways encompass transcription factors and cis-regulatory elements that interact as transcription factor-regulatory element (TF-RE) units. Independent origins of similar phenotypes likely involve changes in different parts of these units, a hypothesis promisingly tested addressing the evolution of the rib-associated lumbar (RAL) morphotype that characterizes emblematic animals such as snakes and elephants. Previous investigation in these lineages identified a polymorphism in the Homology region 1 [H1] enhancer of the Myogenic factor-5 [Myf5], which interacts with HOX10 proteins to modulate rib development. Here we address the evolution of TF-RE units focusing on independent origins of RAL morphotypes. We compiled an extensive database for H1-Myf5 and HOX10 sequences with two goals: (i) evaluate if the enhancer polymorphism is present in amphibians exhibiting the RAL morphotype and (ii) test a hypothesis of enhanced evolutionary flexibility mediated by TF-RE units, according to which independent origins of the RAL morphotype might involve changes in either component of the interaction unit. We identified the H1-Myf5 polymorphism in lineages that diverged around 340 Ma, including Lissamphibia. Independent origins of the RAL morphotype in Tetrapoda involved sequence variation in either component of the TF-RE unit, confirming that different changes may similarly affect the phenotypic outcome of a given developmental pathway.

One Tool for Many Jobs: Divergent and Conserved Actions of Androgen Signaling in Male Internal Reproductive Tract and External Genitalia

In the 1940s, Alfred Jost demonstrated the necessity of testicular secretions, particularly androgens, for male internal and external genitalia differentiation. Since then, our knowledge of androgen impacts on differentiation of the male internal (Wolffian duct) and external genitalia (penis) has been drastically expanded upon. Between these two morphologically and functionally distinct organs, divergent signals facilitate the establishment of tissue-specific identities. Conversely, conserved actions of androgen signaling are present in both tissues and are largely responsible for the growth and expansion of the organs. In this review we synthesize the existing knowledge of the cell type-specific, organ specific, and conserved signaling mechanisms of androgens. Mechanistic studies on androgen signaling in the Wolffian duct and male external genitalia have largely been conducted in mouse model organisms. Therefore, the majority of the review is focused on mouse model studies.

A Review of Prostate Organogenesis and a Role for iPSC-Derived Prostate Organoids to Study Prostate Development and Disease

The prostate is vulnerable to two major age-associated diseases, cancer and benign enlargement, which account for significant morbidity and mortality for men across the globe. Prostate cancer is the most common cancer reported in men, with over 1.2 million new cases diagnosed and 350,000 deaths recorded annually worldwide. Benign prostatic hyperplasia (BPH), characterised by the continuous enlargement of the adult prostate, symptomatically afflicts around 50% of men worldwide. A better understanding of the biological processes underpinning these diseases is needed to generate new treatment approaches. Developmental studies of the prostate have shed some light on the processes essential for prostate organogenesis, with many of these up- or downregulated genes expressions also observed in prostate cancer and/or BPH progression. These insights into human disease have been inferred through comparative biological studies relying primarily on rodent models. However, directly observing mechanisms of human prostate development has been more challenging due to limitations in accessing human foetal material. Induced pluripotent stem cells (iPSCs) could provide a suitable alternative as they can mimic embryonic cells, and iPSC-derived prostate organoids present a significant opportunity to study early human prostate developmental processes. In this review, we discuss the current understanding of prostate development and its relevance to prostate-associated diseases. Additionally, we detail the potential of iPSC-derived prostate organoids for studying human prostate development and disease.

An evo-devo perspective of the female reproductive tract

The vertebrate female reproductive tract has undergone considerable diversification over evolution, having become physiologically adapted to different reproductive strategies. This review considers the female reproductive tract from the perspective of evolutionary developmental biology (evo-devo). Very little is known about how the evolution of this organ system has been driven at the molecular level. In most vertebrates, the female reproductive tract develops from paired embryonic tubes, the Müllerian ducts. We propose that formation of the Müllerian duct is a conserved process that has involved co-option of genes and molecular pathways involved in tubulogenesis in the adjacent mesonephric kidney and Wolffian duct. Downstream of this conservation, genetic regulatory divergence has occurred, generating diversity in duct structure. Plasticity of the Hox gene code and wnt signaling, in particular, may underlie morphological variation of the uterus in mammals, and evolution of the vagina. This developmental plasticity in Hox and Wnt activity may also apply to other vertebrates, generating the morphological diversity of female reproductive tracts evident today.

A tale of two tracts: history, current advances, and future directions of research on sexual differentiation of reproductive tracts†

Alfred Jost's work in the 1940s laid the foundation of the current paradigm of sexual differentiation of reproductive tracts, which contends that testicular hormones drive the male patterning of reproductive tract system whereas the female phenotype arises by default. Once established, the sex-specific reproductive tracts undergo morphogenesis, giving rise to anatomically and functionally distinct tubular organs along the rostral-caudal axis. Impairment of sexual differentiation of reproductive tracts by genetic alteration and environmental exposure are the main causes of disorders of sex development, and infertility at adulthood. This review covers past and present work on sexual differentiation and morphogenesis of reproductive tracts, associated human disorders, and emerging technologies that have made impacts or could radically expand our knowledge in this field.

Roles of the HOXA10 gene during castrate-resistant prostate cancer progression

Homeobox A10 (HOXA10) is an important transcription factor that regulates the development of the prostate gland. However, it remains unknown whether it modulates prostate cancer (PCa) progression into castrate-resistant stages. In this study, we have applied RNA in situ hybridization assays to demonstrate that downregulation of HOXA10 expression is associated with castrate-resistant PCa. These findings are supported by public RNA-seq data showing that reduced HOXA10 expression is correlated with poor patient survival. We show that HOXA10 suppresses PCa cell proliferation, anchorage colony formation and xenograft growth independent to androgens. Using AmpliSeq transcriptome sequencing, we have found that gene groups associated with lipid metabolism and androgen receptor (AR) signaling are enriched in the HOXA10 transcriptome. Furthermore, we demonstrate that HOXA10 suppresses the transcription of the fatty acid synthase (FASN) gene by forming a protein complex with AR and prevents AR recruitment to the FASN gene promoter. These results lead us to conclude that downregulation of HOXA10 gene expression may enhance lipogenesis to promote PCa cell growth and tumor progression to castrate-resistant stage.

Gene and protein expression in the reproductive tract of Brazilian Somalis rams

Brazilian Somalis is a locally-adapted breed of rams raised in tropical climate and native pastures. The present study was conducted to evaluate gene expression and proteome of the reproductive tract of such rams. Samples were collected from testes, epididymides, seminal vesicles and bulbourethral glands of four rams. Expression of clusterin (CLU), osteopontin (OPN) and prostaglandin D2 synthase (PGDS) genes were evaluated in all samples by real-time PCR. Shotgun proteomic analysis was performed using samples from the head, corpus and cauda epididymides and from all other structures as well. Gene ontology terms and protein interactions were obtained from UniProtKB databases and MetaCore v.6.8 platform. CLU trasncripts were detected in the testes, epididymides, seminal vesicles and bulbourethral glands of the Somalis rams. The initial region and body of the epididymis had the greatest CLU expression. OPN mRNA was localized in all tissues of the ram reproductive tract. PGDS mRNA was detected in the testes and epididymides. Lable-free mass spectrometry allowed the identification of 137 proteins in all samples. Proteins of the epididymis head mainly participate in cellular processes and response to stimulus, participating in catalityc activity and binding. Proteins of epididymis body acted as regulatory proteins and in cellular processes, with binding and catalytic activity. Cauda epididymis molecules were associated with cellular processes and regulation, with binding function and catalytic activity as well. Testis proteins were mainly linked to cell processes and response to stimuli, and had catalytic function. Seminal vesicle proteins were involved in regulation and mainly with binding functions. Most bulbourethral gland proteins participated in cellular processes. The present study is the first to evaluate the proteome and gene expressions in the reproductive tract of Brazilian Somalis rams. Such pieces of information bring significant cointribution for the understanding of the reproductive physiology of locally-adapted livestock.

Prostate Organogenesis

The prostate is a male exocrine gland that secretes components of the seminal fluid. In men, prostate tumors are one of the most prevalent cancers. Studies on the development of the prostate have given a better understanding of the processes and genes that are important in the formation of this organ and have provided insights into the mechanisms of prostate tumorigenesis. These developmental studies have provided evidence that some of the genes and signaling pathways involved in development are reactivated or deregulated during prostate cancer. The prostate goes through a number of different stages during organogenesis, which include organ specification, epithelial budding, branching morphogenesis, canalization, and cytodifferentiation. During development, these processes are tightly regulated, many of which are controlled by the male hormone androgens. The majority of prostate tumors remain hormone regulated, and antiandrogen therapy is a first-line therapy, highlighting the important link between prostate organogenesis and cancer. In this review, we describe some of the data on genes that have important roles during prostate development that also have strong evidence linking them to prostate cancer.

Morphoregulatory pathways in prostate ductal development

The mouse prostate is a male sex-accessory gland comprised of a branched ductal network arranged into three separate bilateral lobes: the anterior, dorsolateral, and ventral lobes. Prostate ductal development is the primary morphogenetic event in prostate development and requires a complex regulation of spatiotemporal factors. This review provides an overview of prostate development and the major genetic regulators and signaling pathways involved. To identify new areas for further study, we briefly highlight the likely important, but relatively understudied, role of the extracellular matrix (ECM). Finally, we point out the potential importance of the ECM in influencing the behavior and prognosis of prostate cancer. Developmental Dynamics 246:89-99, 2017. © 2016 Wiley Periodicals, Inc.

Prostate organogenesis: tissue induction, hormonal regulation and cell type specification

Prostate organogenesis is a complex process that is primarily mediated by the presence of androgens and subsequent mesenchyme-epithelial interactions. The investigation of prostate development is partly driven by its potential relevance to prostate cancer, in particular the apparent re-awakening of key developmental programs that occur during tumorigenesis. However, our current knowledge of the mechanisms that drive prostate organogenesis is far from complete. Here, we provide a comprehensive overview of prostate development, focusing on recent findings regarding sexual dimorphism, bud induction, branching morphogenesis and cellular differentiation.

HOXB13 mutations and binding partners in prostate development and cancer: Function, clinical significance, and future directions

The recent and exciting discovery of germline HOXB13 mutations in familial prostate cancer has brought HOX signaling to the forefront of prostate cancer research. An enhanced understanding of HOX signaling, and the co-factors regulating HOX protein specificity and transcriptional regulation, has the high potential to elucidate novel approaches to prevent, diagnose, stage, and treat prostate cancer. Toward our understanding of HOX biology in prostate development and prostate cancer, basic research in developmental model systems as well as other tumor sites provides a mechanistic framework to inform future studies in prostate biology. Here we describe our current understanding of HOX signaling in genitourinary development and cancer, current clinical data of HOXB13 mutations in multiple cancers including prostate cancer, and the role of HOX protein co-factors in development and cancer. These data highlight numerous gaps in our understanding of HOX function in the prostate, and present numerous potentially impactful mechanistic and clinical opportunities for future investigation.

Epigenetic Alterations Affecting Transcription Factors and Signaling Pathways in Stromal Cells of Endometriosis

Endometriosis is characterized by growth of endometrial-like tissue outside the uterine cavity. Since its pathogenesis may involve epigenetic changes, we used Illumina 450K Methylation Beadchips to profile CpG methylation in endometriosis stromal cells compared to stromal cells from normal endometrium. We validated and extended the Beadchip data using bisulfite sequencing (bis-seq), and analyzed differential methylation (DM) at the CpG-level and by an element-level classification for groups of CpGs in chromatin domains. Genes found to have DM included examples encoding transporters (SLC22A23), signaling components (BDNF, DAPK1, ROR1, and WNT5A) and transcription factors (GATA family, HAND2, HOXA cluster, NR5A1, OSR2, TBX3). Intriguingly, among the TF genes with DM we also found JAZF1, a proto-oncogene affected by chromosomal translocations in endometrial stromal tumors. Using RNA-Seq we identified a subset of the DM genes showing differential expression (DE), with the likelihood of DE increasing with the extent of the DM and its location in enhancer elements. Supporting functional relevance, treatment of stromal cells with the hypomethylating drug 5aza-dC led to activation of DAPK1 and SLC22A23 and repression of HAND2, JAZF1, OSR2, and ROR1 mRNA expression. We found that global 5hmC is decreased in endometriotic versus normal epithelial but not stroma cells, and for JAZF1 and BDNF examined by oxidative bis-seq, found that when 5hmC is detected, patterns of 5hmC paralleled those of 5mC. Together with prior studies, these results define a consistent epigenetic signature in endometriosis stromal cells and nominate specific transcriptional and signaling pathways as therapeutic targets.

Understanding normal and abnormal development of the Wolffian/epididymal duct by using transgenic mice

The development of the Wolffian/epididymal duct is crucial for proper function and, therefore, male fertility. The development of the epididymis is complex; the initial stages form as a transient embryonic kidney; then the mesonephros is formed, which in turn undergoes extensive morphogenesis under the influence of androgens and growth factors. Thus, understanding of its full development requires a wide and multidisciplinary view. This review focuses on mouse models that display abnormalities of the Wolffian duct and mesonephric development, the importance of these mouse models toward understanding male reproductive tract development, and how these models contribute to our understanding of clinical abnormalities in humans such as congenital anomalies of the kidney and urinary tract (CAKUT).

Hox genes and evolution

Hox proteins are a deeply conserved group of transcription factors originally defined for their critical roles in governing segmental identity along the antero-posterior (AP) axis in Drosophila. Over the last 30 years, numerous data generated in evolutionarily diverse taxa have clearly shown that changes in the expression patterns of these genes are closely associated with the regionalization of the AP axis, suggesting that Hox genes have played a critical role in the evolution of novel body plans within Bilateria. Despite this deep functional conservation and the importance of these genes in AP patterning, key questions remain regarding many aspects of Hox biology. In this commentary, we highlight recent reports that have provided novel insight into the origins of the mammalian Hox cluster, the role of Hox genes in the generation of a limbless body plan, and a novel putative mechanism in which Hox genes may encode specificity along the AP axis. Although the data discussed here offer a fresh perspective, it is clear that there is still much to learn about Hox biology and the roles it has played in the evolution of the Bilaterian body plan.

Is the Epididymis a Series of Organs Placed Side By Side?

The mammalian epididymis is more than a highly convoluted tube divided into four regions: initial segment, caput, corpus and cauda. It is a highly segmented structure with each segment expressing its own and overlapping genes, proteins, and signal transduction pathways. Therefore, the epididymis may be viewed as a series of organs placed side by side. In this review we discuss the contributions of septa that divide the epididymis into segments and present hypotheses as to the mechanism by which septa form. The mechanisms of Wolffian duct segmentation are likened to the mechanisms of segmentation of the renal nephron and somites. The renal nephron may provide valuable clues as to how the Wolffian duct is patterned during development, whereas somitogenesis may provide clues as to the timing of the development of each segment. Emphasis is also placed upon how segments are differentially regulated, in support of the idea that the epididymis can be considered a series of multiple organs placed side by side. One region in particular, the initial segment, which consists of 2 or 4 segments in mice and rats, respectively, is unique with respect to its regulation and vascularity compared to other segments; loss of development of these segments leads to male infertility. Different ways of thinking about how the epididymis functions may provide new directions and ideas as to how sperm maturation takes place.

Mesenchymal Hox6 function is required for mouse pancreatic endocrine cell differentiation

Despite significant advances in our understanding of pancreatic endocrine cell development, the function of the pancreatic mesodermal niche in this process is poorly understood. Here we report a novel role for mouse Hox6 genes in pancreatic organogenesis. Hox6 genes are expressed exclusively in the mesoderm of the developing pancreas. Genetic loss of all three Hox6 paralogs (Hoxa6, Hoxb6 and Hoxc6) leads to a dramatic loss of endoderm-derived endocrine cells, including insulin-secreting β-cells, and to mild delays and disruptions in pancreatic branching and exocrine differentiation. Ngn3-expressing pan-endocrine progenitor cells are specified normally in Hox6 mutant pancreata, but fail to mature into hormone-producing cells. Reduced expression of Wnt5a is observed in mutant pancreatic mesenchyme, leading to subsequent loss of expression of the crucial Wnt inhibitors Sfrp3 and Dkk1 in endocrine progenitor cells. These results reveal a key role for Hox6 genes in establishing Wnt mesenchymal-epithelial crosstalk in pancreatic development.

Wolffian duct development

The Wolffian ducts (WDs) are the progenitors of the epididymis, vas deferens and seminal vesicles. They form initially as nephric ducts that acquire connection to the developing testis as the mesonephros regresses. The development of the WDs is dependent on androgens. Conventionally, the active androgen is believed to be testosterone delivered locally rather than via the systemic circulation. However, recent studies in marsupials show that 5α-reduced steroids are essential and that these can induce virilisation even when they are delivered via the systemic circulation. The development of the WDs involves an interplay between the duct epithelium and underlying mesenchyme; androgen receptors in both the epithelium and mesenchyme are needed. The epidermal growth factor and epidermal growth factor receptor may play a role, possibly via activation of androgen receptor. The formation of the epididymis involves a complex morphogenetic program to achieve the normal pattern of coiling, formation of septae, and regional functional differentiation. In part, this process may be mediated by inhibin beta A as well as by genes from the HOX cluster. Whilst the development of the WD is androgen dependent, it is clear that there is a complex interplay between androgens, genes and growth factors in the tissues that leads to the formation of the complex anatomy of the male reproductive duct system in the adult.

Human HOX gene disorders

The Hox genes are an evolutionarily conserved family of genes, which encode a class of important transcription factors that function in numerous developmental processes. Following their initial discovery, a substantial amount of information has been gained regarding the roles Hox genes play in various physiologic and pathologic processes. These processes range from a central role in anterior-posterior patterning of the developing embryo to roles in oncogenesis that are yet to be fully elucidated. In vertebrates there are a total of 39 Hox genes divided into 4 separate clusters. Of these, mutations in 10 Hox genes have been found to cause human disorders with significant variation in their inheritance patterns, penetrance, expressivity and mechanism of pathogenesis. This review aims to describe the various phenotypes caused by germline mutation in these 10 Hox genes that cause a human phenotype, with specific emphasis paid to the genotypic and phenotypic differences between allelic disorders. As clinical whole exome and genome sequencing is increasingly utilized in the future, we predict that additional Hox gene mutations will likely be identified to cause distinct human phenotypes. As the known human phenotypes closely resemble gene-specific murine models, we also review the homozygous loss-of-function mouse phenotypes for the 29 Hox genes without a known human disease. This review will aid clinicians in identifying and caring for patients affected with a known Hox gene disorder and help recognize the potential for novel mutations in patients with phenotypes informed by mouse knockout studies.

Recombineering-based dissection of flanking and paralogous Hox gene functions in mouse reproductive tracts

Hox genes are key regulators of development. In mammals, the study of these genes is greatly confounded by their large number, overlapping functions and interspersed shared enhancers. Here, we describe the use of a novel recombineering strategy to introduce simultaneous frameshift mutations into the flanking Hoxa9, Hoxa10 and Hoxa11 genes, as well as their paralogs on the HoxD cluster. The resulting Hoxa9,10,11 mutant mice displayed dramatic synergistic homeotic transformations of the reproductive tracts, with the uterus anteriorized towards oviduct and the vas deferens anteriorized towards epididymis. The Hoxa9,10,11 mutant mice also provided a genetic setting that allowed the discovery of Hoxd9,10,11 redundant reproductive tract patterning function. Both shared and distinct Hox functions were defined. Hoxd9,10,11 play a crucial role in the regulation of uterine immune function. Non-coding non-polyadenylated RNAs were among the key Hox targets, with dramatic downregulation in mutants. We observed Hox cross-regulation of transcription and splicing. In addition, we observed a surprising anti-dogmatic apparent posteriorization of the uterine epithelium. In caudal regions of the uterus, the normal simple columnar epithelium flanking the lumen was replaced by a pseudostratified transitional epithelium, normally found near the more posterior cervix. These results identify novel molecular functions of Hox genes in the development of the male and female reproductive tracts.

Segment- and cell-specific expression of D-type cyclins in the postnatal mouse epididymis

Sperm transport, maturation and storage are the essential functions of the epididymis. The epididymis in the mouse is structurally characterized by regional and segmental organization including caput, corpus and cauda epididymis that are comprised of 10 segments. Although several growth factor signaling pathways have been discovered in the epididymis, how these converge onto the cell cycle components is unknown. To begin to elucidate the growth factor control of cell cycle events in the epididymis, we analyzed the expression of D-type cyclins at different postnatal ages. At 7d, cyclin D1 was mainly expressed in the cauda epithelium, by 14d its expression occurred in the epithelium of caput, corpus and cauda that persisted up to 21d. By 42d, cyclin D1 was mostly detectable in the principal cells of the caput and corpus (segments 1-7) but not in the cauda epididymis. Expression of cyclin D2, unlike that of cyclin D1, was evident only at 42d but not earlier, and was mostly confined to corpus and cauda epithelium. In contrast to both cyclins D1 and D2, cyclin D3 was expressed primarily in the interstitium at 7d and by 21d its expression was localized to the epithelium of the corpus and cauda epididymis. By 42d, expression of cyclin D3 peaked in segments 6-10 and confined to basal and principal cells of the corpus and apical cells of the cauda epithelium. Ki67 immunoreactivity confirmed absence of cell proliferation despite continued expression of D-type cyclins in the adult epididymis. Collectively, on the basis of our immunophenotyping and protein expression data, we conclude that the D-type cyclins are expressed in a development-, segment-, and cell-specific manner in the postnatal mouse epididymis.

Mll5 is required for normal spermatogenesis

Background

Mll5 is currently a member of the Mll family of SET domain histone methyltransferase proteins but studies have also showed that it could be part of the SET3 branch of proteins. Recently, constitutive knock out animal studies have shown that Mll5 is required for proper haematopoietic stem cell differentiation, and loss of Mll5 results in synthetic lethality for genome de-methylation. Mll5 deficient male mice are infertile and here we analyse the consequences of Mll5 deficiency for spermatogenesis.

Methodology/Principal Findings

Mll5 deficient male mice, but not female mice, are infertile. Here we show using RNA in-situ hybridization that Mll5 is expressed in the germ cells of the testes of wild type mice. Consistent with the expression of Mll5, we demonstrate by electron microscopy, video microscopy and in vitro fertilisation techniques that Mll5 deficient mice have defects in terminal maturation and packaging of sperm. The defects seen include detachment of the acrosomal cap and impaired excess cytoplasm removal. Functional tests of sperm motility show a lack of progressive motility of spermatozoa from Mll5 deficient animals. None of these defects could be rescued by in vitro fertilization. Using microarray analysis we show that transcripts implicated in spermatogenesis are dysregulated.

Conclusions/Significance

Our data demonstrate a clear role of Mll5 in mammalian spermatogenesis at the level of terminal differentiation providing further support for its classification in the SET3 branch of proteins. Moreover, this study identifies Tlk2, Utx, Gpr64, Sult4a1, Rap2ip, Vstm2 and HoxA10 as possible Mll5 targets that together may account for the observed spermatozoa maturation defects.

Gene expression in the efferent ducts, epididymis, and vas deferens during embryonic development of the mouse

The tissues of the male reproductive tract are characterized by distinct morphologies, from highly coiled to un-coiled. Global gene expression profiles of efferent ducts, epididymis, and vas deferens were generated from embryonic day 14.5 to postnatal day 1 as tissue-specific morphologies emerge. Expression of homeobox genes, potential mediators of tissue-specific morphological development, was assessed. Twenty homeobox genes were identified as either tissue-enriched, developmentally regulated, or both. Additionally, ontology analysis demonstrated cell adhesion to be highly regulated along the length of the reproductive tract. Regulators of cell adhesion with variable expression between the three tissues were identified including Alcam, various cadherins, and multiple integrins. Immunofluorescence localization of the cell adhesion regulators POSTN and CDH2 demonstrated cell adhesion in the epithelium and mesenchyme of the epididymis may change throughout development. These results suggest cell adhesion may be modulated in a tissue-specific manner, playing an important role in establishing each tissue's final morphology.

HOXB13 is co-localized with androgen receptor to suppress androgen-stimulated prostate-specific antigen expression

During the prostate cancer (PCa) development and its progression into hormone independency, androgen receptor (AR) signals play a central role by triggering the regulation of target genes, including prostate-specific antigen. However, the regulation of these AR-mediated target genes is not fully understood. We have previously demonstrated a unique role of HOXB13 homeodomain protein as an AR repressor. Expression of HOXB13 was highly restricted to the prostate and its suppression dramatically increased hormone-activated AR transactivation, suggesting that prostate-specific HOXB13 was a highly potent transcriptional regulator. In this report, we demonstrated the action mechanism of HOXB13 as an AR repressor. HOXB13 suppressed androgen-stimulated AR activity by interacting with AR. HOXB13 did neither bind to AR responsive elements nor disturb nuclear translocation of AR in response to androgen. In PCa specimen, we also observed mutual expression pattern of HOXB13 and AR. These results suggest that HOXB13 not only serve as a DNA-bound transcription factor but play an important role as an AR-interacting repressor to modulate hormone-activated androgen receptor signals. Further extensive studies will uncover a novel mechanism for regulating AR-signaling pathway to lead to expose new role of HOXB13 as a non-DNA-binding transcriptional repressor.

HOXB13 promotes androgen independent growth of LNCaP prostate cancer cells by the activation of E2F signaling

BACKGROUND

Androgen signaling plays a critical role in the development of prostate cancer and its progression. However, androgen-independent prostate cancer cells emerge after hormone ablation therapy, resulting in significant clinical problems. We have previously demonstrated that the HOXB13 homeodomain protein functions as a prostate cancer cell growth suppressor by inhibiting androgen-mediated signals. However, the role of the HOXB13 in androgen-independent growth of prostate cancer cells remains unexplained.

RESULTS

In this report, we first demonstrated that HOXB13 was highly overexpressed in hormone-refractory tumors compared to tumors without prostate-specific antigen after initial treatment. Functionally, in an androgen-free environment minimal induction of HOXB13 in LNCaP prostate cancer cells, to the level of the normal prostate, markedly promoted cell proliferation while suppression inhibited cell proliferation. The HOXB13-mediated cell growth promotion in the absence of androgen, appears to be mainly accomplished through the activation of RB-E2F signaling by inhibiting the expression of the p21waf tumor suppressor. Indeed, forced expression of HOXB13 dramatically decreased expression of p21waf; this inhibition largely affected HOXB13-mediated promotion of E2F signaling.

CONCLUSIONS

Taken together, the results of this study demonstrated the presence of a novel pathway that helps understand androgen-independent survival of prostate cancer cells. These findings suggest that upregulation of HOXB13 is associated with an additive growth advantage of prostate cancer cells in the absence of or low androgen concentrations, by the regulation of p21-mediated E2F signaling.

Functional remodeling of benign human prostatic tissues in vivo by spontaneously immortalized progenitor and intermediate cells

Tissue remodeling or regeneration is believed to initiate from multipotent stem and progenitor cells. We report here the establishment of two spontaneously immortalized adult non-tumorigenic human prostate epithelial cell lines, NHPrE1 and BHPrE1. NHPrE1 (CD133(high)/CD44(high)/OCT4(high)/PTEN(high)) was characterized as a putative progenitor cell, and BHPrE1 (p63(high)/p53(high)/p21(WAF1)(high)/RB(high)) was characterized as a putative epithelial intermediate cell. Genomic analysis demonstrated an abnormal karyotype with genomic rearrangements including PTEN amplification in NHPrE1 and CTNNB1 (beta-catenin) amplification in BHPrE1 cells. Embedded three-dimensional culture of NHPrE1 showed greater branching than BHPrE1. A tissue recombination-xenografting model was utilized to compare remodeling of human prostatic tissues in vivo. A series of tissue recombinants, made by mixing different ratios of human prostatic epithelial cells and inductive rat urogenital sinus mesenchyme, were grafted to the renal capsule of severe combined immunodeficient mice. Both cell lines were able to regenerate benign secretory ductal-acinar architecture in vivo, containing intact basal and luminal epithelial layers confirmed by the expression of appropriate CK profiles. Prostate-specific antigen, 15-lipoxygenase-2, androgen receptor, and NKX3.1 proteins were appropriately expressed in the regenerated epithelia. Regeneration of benign prostatic glandular structures could be achieved using as few as 10 NHPrE1 cells, whereas 200,000 BHPrE1 cells were required to achieve prostatic architecture. This suggests a greater proportion of progenitor/stem cells in NHPrE1 than in BHPrE1. These cell lines provide important data on progenitor and intermediate cell phenotypes and represent significant new tools for the elucidation of molecular mechanisms of human prostatic regeneration, pathogenesis, and carcinogenesis.

A FOXA1-binding enhancer regulates Hoxb13 expression in the prostate gland

Hoxb13 is robustly transcribed in derivatives of posterior endoderm including the colon, rectum, and the prostate gland. Transcriptional activity in the prostate persists unabated under conditions of androgen deprivation and throughout the course of disease progression in a mouse prostate cancer model. To elucidate the molecular basis of prostate-restricted transcriptional activation of Hoxb13, a bacterial artificial chromosome (BAC)-based reporter gene deletion analysis was performed in transgenic mice. Two regions downstream of the Hoxb13 coding region were found to be required to support transcriptional activity in the prostate but were completely dispensable for expression in the colon and rectum. Bioinformatic analyses of one region identified a 37-bp element conserved in mammals. This element, which bears two potential binding sites for Forkhead class transcription factors, is occupied by FOXA1 in a human prostate cancer cell line. Precise replacement of this enhancer with an extended LoxP site in the context of a 218,555-bp BAC reporter nearly extinguished Hoxb13-mediated transcriptional activity in the mouse prostate. These data demonstrate that FOXA1 directly regulates HOXB13 in human prostate epithelial cells, and show that this prostate-specific regulatory mechanism is conserved in mice.

Epithelial-mesenchymal crosstalk in Wolffian duct and fetal testis cord development

Interactions between adjacent epithelial and mesenchymal tissues represent a highly conserved mechanism in embryonic organogenesis. In particular, the ability of the mesenchyme to instruct cellular differentiation of the epithelium is a fundamental requirement for the morphogenesis of tubular structures such as those found in the kidneys, lungs, and the developing male reproductive system. Once the tubular structure has formed, it receives signals from the mesenchyme, which can control proliferation, patterning, and differentiation of the epithelium inside the tube. However, the epithelium is not a "silent partner" in this process, and epithelium-derived factors are often required for proper maintenance of the mesenchymal compartment. Although much emphasis has been placed on the characterization of mesenchymally-derived signals required for epithelial differentiation, it is important to note that epithelial-mesenchymal interactions are a two-way street wherein each compartment requires the presence of the other for proper tubule morphogenesis and function. In this review, we discuss epithelial-mesenchymal interactions in the processes of Wolffian duct and fetal testis cord development using the mouse as a model organism and propose inhibin beta A as a conserved mesenchyme-derived regulator in these two male-specific tubular structures.

Development and morphogenesis of the Wolffian/epididymal duct, more twists and turns

The epididymis serves a critical function of preparing the male germ cells for fertilization. In order for the epididymis to carry out this role it must undergo a highly coordinated succession of molecular and morphogenic events during development. These events begin with the formation of the Wolffian or nephric duct, the embryonic precursor of the male reproductive system, and end with the three-dimensional coiled postnatal epididymis that is comprised of several distinctly functional segments. How the duct changes from a simple straight tube to a highly convoluted structure will be the focus of this article. In reviewing the literature's current understanding of epididymal morphogenesis, we will highlight some of the classic morphological studies and discuss some of the more recent genetic models that have all served to contribute to our understanding of this system. Where published information is scarce we will provide potential hypotheses that warrant further investigation and may open up new directions of exploration using the epididymis as a model for tubular morphogenesis.

Expression of the Ladybird-like homeobox 2 transcription factor in the developing mouse testis and epididymis

BACKGROUND

Homeoproteins are a class of transcription factors that are well-known regulators of organogenesis and cell differentiation in numerous tissues, including the male reproductive system. Indeed, a handful of homeoproteins have so far been identified in the testis and epididymis where a few were shown to play important developmental roles. Through a degenerate PCR approach aimed at identifying novel homeoproteins expressed in the male reproductive system, we have detected several homeoproteins most of which had never been described before in this tissue. One of these homeoproteins is Ladybird-like homeobox 2 (Lbx2), a homeobox factor mostly known to be expressed in the nervous system.

RESULTS

To better define the expression profile of Lbx2 in the male reproductive system, we have performed in situ hybridization throughout testicular and epididymal development and into adulthood. Lbx2 expression was also confirmed by real time RT-PCR in those tissues and in several testicular and epididymal cell lines. In the epididymis, a highly segmented tissue, Lbx2 shows a regionalized expression profile, being more expressed in proximal segments of the caput epididymis than any other segment. In the testis, we found that Lbx2 is constitutively expressed at high levels in Sertoli cells. In interstitial cells, Lbx2 is weakly expressed during fetal and early postnatal life, highly expressed around P32-P36, and absent in adult animals. Finally, Lbx2 can also be detected in a population of germ cells in adults.

CONCLUSION

Altogether, our data suggest that the homeoprotein Lbx2 might be involved in the regulation of male reproductive system development and cell differentiation as well as in male epididymal segmentation.

Noggin is required for normal lobe patterning and ductal budding in the mouse prostate

Mesenchymal expression of the BMP antagonist NOGGIN during prostate development plays a critical role in pre-natal ventral prostate development and opposes BMP4-mediated inhibition of cell proliferation during postnatal ductal development. Morphologic examination of newborn Noggin-/- male fetuses revealed genitourinary anomalies including cryptorchidism, incomplete separation of the hindgut from the urogenital sinus (UGS), absence of the ventral mesenchymal pad, and a complete loss of ventral prostate (VP) budding. Examination of lobe-specific marker expression in the E14 Noggin-/- UGS rescued by transplantation under the renal capsule of a male nude mouse confirmed a complete loss of VP determination. More modest effects were observed in the other lobes, including decreased number of ductal buds in the dorsal and lateral prostates of newborn Noggin-/- males. BMP4 and BMP7 have been shown to inhibit ductal budding and outgrowth by negatively regulating epithelial cell proliferation. We show here that NOGGIN can neutralize budding inhibition by BMP4 and rescues branching morphogenesis of BMP4-exposed UGS in organ culture and show that the effects of BMP4 and NOGGIN activities converge on P63+ epithelial cells located at nascent duct tips. Together, these studies show that the BMP-NOGGIN axis regulates patterning of the ventral prostate, regulates ductal budding, and controls proliferation of P63+ epithelial cells in the nascent ducts of developing mouse prostate.

Identification of a transcription factor, BHLHB8, involved in mouse seminal vesicle epithelium differentiation and function

The seminal vesicle is a male accessory sex organ that develops from segments of the Wolffian duct adjacent to the urogenital sinus. It produces most of the seminal plasma in both humans and rodents. To date, very few transcription factors have been linked to the development and differentiation of seminal vesicles. In this study, we have examined the role of basic helix-loop-helix (BHLH) B8 transcription factor expressed at high levels in the adult seminal vesicle and during seminal gland differentiation. Immunofluorescent studies indicate that BHLHB8 is expressed within the epithelial layer of the seminal layer of the seminal vesicle following branching morphogenesis but prior to full maturation of cell morphology and function. Analysis of mice that do not express BHLHB8 (Bhlhb8(-/-)) indicates no deficiency in the initial development of the seminal vesicle. However, morphological and ultrastructural analysis indicates disruption of the epithelial cellular architecture. The seminal vesicle epithelial layer of 2-mo-old Bhlhb8(-/-) mice shows extensive cellular degeneration based on the appearance of reduced microvilli, altered granule size, and dilated endoplasmic reticulum and Golgi apparatus. The seminal vesicle epithelial cells also degenerate prematurely, as evidenced by disruption of nuclear architecture and significant accumulations of autophagic bodies. These results identify BHLHB8 as a regulator in establishing and stabilizing the secreting epithelial cells of the seminal vesicle.

Posterior Hox gene expression and differential androgen regulation in the developing and adult rat prostate lobes

Axis positioning and tissue determination during development involve coordinated expression of Hox genes throughout the body. The most posterior Hox gene clusters are involved in prostate organogenesis. In the present study, we characterized and compared the expression profiles of posterior (5') Hox genes in the separate lobes of the adult rat prostate gland, the coagulating gland, seminal vesicles, and epididymis using quantitative real-time RT-PCR. These genes include Hoxa9-11, Hoxa13, Hoxd13, and Hoxb13. We identified a unique Hox code for each of these organs and propose that this contributes to the organ-specific and prostate lobe-specific identities in the adult rat. Using the ventral prostate (VP) as a model, we characterized the Hox genes expression patterns over time from birth through adulthood. Expression levels of the three Hox13 genes and Hoxa10 were significantly higher in the adult VP compared with the neonatal developing VP suggesting an important role during adult homeostasis. In contrast, Hoxa9 and Hoxa11 levels declined after morphogenesis suggesting a specific developmental role. Overall, the Hoxb13 gene exhibited the most striking temporal and organ-specific differences. Using in situ hybridization and immunohistochemistry, a distinct Hoxb13 anterior-to-posterior expression gradient was observed with the highest expression levels in the VP luminal epithelial cells, moderate levels in the lateral prostate, and low expression in the dorsal prostate. An expression gradient was also observed along the ductal length in all three prostate lobes with strongest expression at the distal tips and limited expression in the proximal ducts. After infection with a lentivirus expressing the Hoxb13 gene, NRP-152 cells cultured under nondifferentiating conditions exhibited robust cytokeratin 8 immunostain indicating that Hoxb13 expression drives luminal cell differentiation in the rat epithelium. Androgen regulation of prostatic Hox gene expression was examined during development in vitro and after castration in the adult rat. In the neonatal VP, all six Hox genes were significantly up-regulated by androgens, whereas none of the genes were affected by testosterone in the lateral prostate. In the adult rat, castration resulted in up-regulation of Hoxa9 and Hoxa13 in the VP and down-regulation of Hoxb13 in the dorsal prostate and lateral prostate. Taken together, we conclude that the prostatic Hox genes reach a destined expression level at specific developmental time points in the prostate gland and possess differential androgenic regulation in a temporal and lobe-specific manner. We suggest that this timely Hox code participates in determining lobe-specific prostatic identity and cellular differentiation.

Fibroblast growth factor receptor 2 tyrosine kinase is required for prostatic morphogenesis and the acquisition of strict androgen dependency for adult tissue homeostasis

The fibroblast growth factor (FGF) family consists of 22 members and regulates a broad spectrum of biological activities by activating diverse isotypes of FGF receptor tyrosine kinases (FGFRs). Among the FGFs, FGF7 and FGF10 have been implicated in the regulation of prostate development and prostate tissue homeostasis by signaling through the FGFR2 isoform. Using conditional gene ablation with the Cre-LoxP system in mice, we demonstrate a tissue-specific requirement for FGFR2 in urogenital epithelial cells--the precursors of prostatic epithelial cells--for prostatic branching morphogenesis and prostatic growth. Most Fgfr2 conditional null (Fgfr2(cn)) embryos developed only two dorsal prostatic (dp) and two lateral prostatic (lp) lobes. This contrasts to wild-type prostate, which has two anterior prostatic (ap), two dp, two lp and two ventral prostatic (vp) lobes. Unlike wild-type prostates, which are composed of well developed epithelial ductal networks, the Fgfr2(cn) prostates, despite retaining a compartmented tissue structure, exhibited a primitive epithelial architecture. Moreover, although Fgfr2(cn) prostates continued to produce secretory proteins in an androgen-dependent manner, they responded poorly to androgen with respect to tissue homeostasis. The results demonstrate that FGFR2 is important for prostate organogenesis and for the prostate to develop into a strictly androgen-dependent organ with respect to tissue homeostasis but not to the secretory function, implying that androgens may regulate tissue homeostasis and tissue function differently. Therefore, Fgfr2(cn) prostates provide a useful animal model for scrutinizing molecular mechanisms by which androgens regulate prostate growth, homeostasis and function, and may yield clues as to how advanced-tumor prostate cells escape strict androgen regulations.

Regulation of Wolffian Duct Development

Wolffian ducts (WDs) are the embryonic structures that form the male internal genitalia. These ducts develop in both the male and female embryo. However, in the female they subsequently regress, whereas in the male they are stabilised by testosterone. The WDs then develop into separate but contiguous organs, the epididymis, vas deferens and seminal vesicles. Recently, considerable progress has been made in identifying genes that are involved in these different stages of development which is described in this review. In addition, WD development in (atypical forms of) cystic fibrosis and intersex disorders, such as the complete androgen insensitivity syndrome, 17beta-hydroxysteroid dehydrogenase deficiency and LH-receptor defects, is discussed. The apparent increase in male reproductive tract disorders is briefly discussed from the perspective of the potential endocrine-disrupting effects of the numerous chemicals in the environment to which the developing male foetus can be exposed.

Branching morphogenesis in the prostate gland and seminal vesicles

The prostate gland and seminal vesicles are the major exocrine glands in the male reproductive tracts of mammals. Although the morphology of these organs varies widely among species, epithelial branching morphogenesis is a key feature of organ development in most mammals including rodents and humans. Insight into the mechanisms that control prostatic and seminal vesicle branching morphogenesis has come from experimental embryological work as well as from the study of mice and humans harboring mutations that alter branching morphogenesis. These studies have demonstrated a requirement for androgens to initiate branching morphogenesis as well as a role for androgens in sustaining the normal rate and extent of branching. In addition, these studies have revealed a series of reciprocal paracrine signals between the developing prostatic epithelium and prostatic mesenchyme that are essential for regulating branching morphogenesis. Key growth factors that participate in these signaling events include members of the fibroblast growth factor, Hedgehog, and transforming growth factor-beta families. Additional genes including several homeobox-containing transcription factors have also been implicated as key regulators of prostatic and seminal vesicle branching morphogenesis. While research in recent years has greatly enhanced our understanding of the molecular control of prostatic and seminal vesicle development, known genes cannot yet explain in molecular terms the complex biological interactions that descriptive and experimental embryological studies have elucidated in the control of branching morphogenesis in these organs.

Disrupted sex differentiation and feminization of man and domestic animals

Genital malformations constitute the most common birth defects in man and domestic animals and occur frequently in males since the participation of many genes is required for sex differentiation to proceed in the male direction. The precise dose, timing, and coordination needed for their expression add to the proneness of various stages in male sex differentiation to external influences. The emerging insight, through the identification of genes involved in the sex differentiation cascade, is that over 85% of sex anomalies in human and domestic animal populations are not attributable to chromosome aberrations or to mutations in a known gene. Since a majority of severely malformed individuals are incapable of reproduction, the high rates of these defects have to be results either of new mutations or of collaboration of environmental factors with genes. Increase in specific malformations in domestic animals often indicates increased concentration of liability genes brought together in the conceptus by inbreeding. However, in human populations where inbreeding is not the norm such increases may reflect environment-induced new mutations or interaction of environmental agents with hormone-sensitive genes. This review summarizes the information currently available on the genetics of major events in male sex differentiation and briefly discusses the collaborative role that environment may play in disrupting different components of this process.

Hormonal, cellular, and molecular regulation of normal and neoplastic prostatic development

This review on normal and neoplastic growth of the prostate emphasizes the importance of epithelial-mesenchymal/stromal interactions. Accordingly, during prostatic development urogenital sinus mesenchyme (a) specifies prostatic epithelial identity, (b) induces epithelial bud formation, (c) elicits prostatic bud growth and regulates ductal branching, (d) promotes differentiation of a secretory epithelium, and (e) specifies the types of secretory proteins expressed. In reciprocal fashion, prostatic epithelium induces smooth muscle differentiation in the mesenchyme. Epithelial-mesenchymal interactions during development continue postnatally into adulthood as stromal-epithelial interactions which play a homeostatic role and in so doing reciprocally maintain epithelial and stromal differentiation and growth-quiescence. Prostatic carcinogenesis involves perturbation of these reciprocal homeostatic cell-cell interactions. The central role of mesenchyme in prostatic epithelial development has been firmly established through analysis of tissue recombinants composed of androgen-receptor-positive wild-type mesenchyme and androgen-receptor-negative epithelium. These studies revealed that at the very least ductal morphogenesis, epithelial cytodifferentiation, epithelial apoptosis and epithelial proliferation are regulated by stromal and not epithelial androgen receptors. Likewise, progression from non-tumorigenesis to tumorigenesis elicited by testosterone plus estradiol proceeds via paracrine mechanisms. Thus, stromal-epithelial interactions play critical roles in the hormonal, cellular, and molecular regulation of normal and neoplastic prostatic development.

HOXB13 homeodomain protein suppresses the growth of prostate cancer cells by the negative regulation of T-cell factor 4

In prostate gland, HOXB13 is highly expressed from the embryonic stages to adulthood. However, the function of HOXB13 in normal cell growth and tumorigenesis is not yet known. We investigated the role of HOXB13 and mechanism by which it functions in HOXB13-negative cells. Expression of HOXB13 was forced in HOXB13-negative PC3 prostate cancer cells using a liposome-mediated gene transfer approach. Compared with the control clones, HOXB13-expressing PC3 cells exhibited significant inhibition of in vitro and in vivo cell growth with G1 cell cycle arrest mediated by the suppression of cyclin D1 expression. Because cyclin D1 is mainly regulated by beta-catenin/T-cell factor (TCF), TCF-4 response element was used in a reporter gene transcription assay, demonstrating that HOXB13 significantly inhibits TCF-4-mediated transcriptional activity in both prostate and nonprostate cells. This inhibition occurred in a dose-responsive manner and was specific to TCF-4 response element. Western blot analysis demonstrated that HOXB13 down-regulates the expression of TCF-4 and its responsive genes, c-myc and cyclin D1. HOXB13 also suppressed the activity of natural c-myc promoter. This study suggests that HOXB13, a transcription factor, functions as a cell growth suppressor by negatively regulating the expression of TCF-4, which eventually provides negative signals for cell proliferation. This observation will provide valuable insight into the molecular basis of prostate tumorigenesis.

Altered Sonic hedgehog signaling is associated with morphological abnormalities in the penis of the BB/WOR diabetic rat

Erectile dysfunction (ED) is a common and debilitating pathological development that affects up to 75% of diabetic males. Neural stimulation is a crucial aspect of the normal erection process. Nerve injury causes ED and disrupts signaling of the Sonic hedgehog (Shh) cascade in the smooth muscle of the corpora cavernosa. Shh and targets of its signaling establish normal corpora cavernosal morphology during postnatal differentiation of the penis and regulate homeostasis in the adult. Interruption of the Shh cascade in the smooth muscle of the corpora cavernosa results in extensive changes in corpora cavernosal morphology that lead to ED. Our hypothesis is that the neuropathy observed in diabetics causes morphological changes in the corpora cavernosa of the penis that result in ED. Disruption of the Shh cascade may be involved in this process. We tested this hypothesis by examining morphological changes in the penis, altered gene and protein expression, apoptosis, and bromodeoxyuridine incorporation in the BB/WOR rat model of diabetes. Extensive smooth muscle and endothelial degradation was observed in the corpora cavernosa of diabetic penes. This degradation accompanied profound ED, significantly decreased Shh protein in the smooth muscle of the corpora cavernosa, and increased penile Shh RNA expression in the intact penis (nerves, corpora, and urethra). Localization and expression of Shh targets were also disrupted in the corpora cavernosa. Increasing our understanding of the molecular mechanisms that regulate Shh signaling may provide valuable insight into improving treatment options for diabetic impotence.

Modelling genitourinary defects in mice: an emerging genetic and developmental system

The rising incidence of genitourinary (GU) defects among newborns establishes the need and opportunity to focus research efforts on the amelioration of this growing public-health concern. Sadly, our inability to explain the causes of GU defects can be directly attributed to our lack of understanding of GU gene function. Recently, mouse models have been used to provide new insights into the mechanisms that underlie congenital GU malformations.

Sonic hedgehog cascade is required for penile postnatal morphogenesis, differentiation, and adult homeostasis

The penis is unique in that it undergoes morphogenesis and differentiation primarily in the postnatal period. For complex structures such as the penis to be made from undifferentiated precursor cells, proliferation, differentiation, and patterning are required. This process involves coordinated activity of multiple signals. Sonic hedgehog (Shh) forms part of a regulatory cascade that is essential for growth and morphogenesis of many tissues. It is hypothesized that the penis utilizes regulatory mechanisms similar to those of the limb and accessory sex organs to pattern penile postnatal morphogenesis and differentiation and that the Shh cascade is critical to this process. To test this hypothesis, Shh, BMP-4, Ptc, and Hoxa-10 localization and function were examined in Sprague-Dawley rat penes by means of quantitative reverse transcription polymerase chain reaction, in situ hybridization, immunohistochemistry, and Western blotting. These genes were expressed in the penis during postnatal morphogenesis in a spatially and temporally restricted manner in adjacent layers of the corpora cavernosal sinusoids. The function of Shh and BMP-4 is to establish and maintain corpora cavernosal sinusoids. The data suggest that Ptc and Hoxa-10 are also important in penile morphogenesis. The continuing function of Shh and targets of its signaling in maintaining penile homeostasis in the adult is significant because disruption of Shh signaling affects erectile function. This is the first report that demonstrates the significant role that Shh plays in establishing and maintaining penile homeostasis and how this relates to erectile function. These studies provide valuable insight that may be applied to improve treatment options for erectile dysfunction.