Pkd1-targeted mutation reveals a role for the Wolffian duct in autosomal dominant polycystic kidney disease.

Several life-threatening diseases of the kidney have their origins in mutational events that occur during embryonic development. In this study, we investigate the role of the Wolffian duct (WD), the earliest embryonic epithelial progenitor of renal tubules, in the etiology of autosomal dominant polycystic kidney disease (ADPKD). ADPKD is associated with a germline mutation of one of the two Pkd1 alleles. For the disease to occur, a second event that disrupts the expression of the other inherited Pkd1 allele must occur. We postulated that this secondary event can occur in the pronephric WD. Using Cre-Lox recombination, mice with WD-specific deletion of one or both Pkd1 alleles were generated. Homozygous Pkd1-targeted deletion in WD-derived tissues resulted in mice with large cystic kidneys and serologic evidence of renal failure. In contrast, heterozygous deletion of Pkd1 in the WD led to kidneys that were phenotypically indistinguishable from control in the early postnatal period. High-throughput sequencing, however, revealed underlying gene and microRNA (miRNA) changes in these heterozygous mutant kidneys that suggest a strong predisposition toward developing ADPKD. Bioinformatic analysis of this data demonstrated an upregulation of several miRNAs that have been previously associated with PKD; pathway analysis further demonstrated that the differentially expressed genes in the heterozygous mutant kidneys were overrepresented in signaling pathways associated with maintenance and function of the renal tubular epithelium. These results suggest that the WD may be an early epithelial target for the genetic or molecular signals that can lead to cyst formation in ADPKD.

We, the developing rete testis, efferent ducts, and Wolffian duct, all hereby agree that we need to connect.

BACKGROUND: The mechanisms by which the rete testis joins the efferent ducts, which joins the Wolffian duct during development, are not known. Mouse and chick models have been helpful in identifying genes that are important for the development of each part, but genes have not been identified as to those that play a role in the joining of each part. Clinical implications of the failure of the male reproductive tract to form a fully functional conduit for spermatozoa are not trivial. Epididymal disjunction, the failure of the efferent ducts to join the testis, is one of several epididymal anomalies that have been observed in some boys who were cryptorchid at birth. OBJECTIVE: A systematic review of studies focusing on the morphogenesis of the mesonephric duct and mesonephric tubules in different species, and identification of clinical issues should there be failure of these tissues to develop. DESIGN: PubMed and GUDMAP databases, and review of books on kidney development were searched for studies reporting on the mechanisms of morphogenesis of the kidney and epididymis. MAIN OUTCOMES MEASURE(S): Gaps in our knowledge were identified, and hypotheses coupled with suggestions for future experiments were presented. RESULTS: A total of 64 papers were identified as relevant, of which 53 were original research articles and 11 were book chapters and reviews covering morphogenesis and clinical issues. Investigators utilized multiple species including, human, mouse, chick, Xenopus, bovine, and sheep. CONCLUSION: Fundamental understanding of the morphogenesis of the male reproductive tract is limited, especially the morphogenesis of the rete testis and efferent ducts. Therefore, it is not surprising that we do not understand how each part unites to form a whole. Only one mechanism of joining of one part of the tract to another was identified: the joining of the Wolffian duct to the cloaca via controlled apoptosis.

Coordination between body growth and tissue growth: Wolffian duct elongation and somitogenesis proceed in harmony with axial growth.

During embryogenesis, different tissues develop coordinately, and this coordination is often in harmony with body growth. Recent studies allow us to understand how this harmonious regulation is achieved at the levels of inter-cellular, inter-tissue, and tissue-body relationships. Here, we present an overview of recently revealed mechanisms by which axial growth (tail growth) drives a variety of morphogenetic events, with a focus on the coordinated progression between Wolffian (nephric) duct elongation and somitogenesis. We also discuss how we can relate this coordination to the events occurring during limb bud outgrowth, since the limb buds and tail bud are appendage anlagen acquired during vertebrate evolution, both of which undergo massive elongation/outgrowth.

Protein tyrosine kinase 7 regulates extracellular matrix integrity and mesenchymal intracellular RAC1 and myosin II activities during Wolffian duct morphogenesis.

Wolffian duct morphogenesis must be highly coordinated with its specialized function of providing an optimal microenvironment for sperm maturation. Without normal Wolffian duct morphogenesis, male infertility will result. Our previous study showed that mediolateral and radial intercalation of epithelial and mesenchymal cells respectively, were major drivers of ductal elongation and were regulated by protein tyrosine kinase 7 (PTK7), a member of the planar cell polarity (PCP) non-canonical Wnt pathway. To understand the mechanism by which PTK7 regulates cell rearrangement/intercalation, we investigated the integrity of the extracellular matrix (ECM) and the activity of intracellular cytoskeleton mediators following loss of Ptk7. Abnormal assembly of nephronectin, laminin, and collagen IV at the basement membrane and fibrosis-like deposition of fibrilla collagen in the interstitium were observed in Ptk7 knockout Wolffian ducts. Further, the activity levels of RAC1 and myosin II, two cytoskeleton mediators, decreased in the Ptk7 knockout mesenchyme compared to controls. In addition, in-vitro experiments suggested that alterations of ECM and cytoskeleton mediators resulted in changes in Wolffian duct morphogenesis. When in-vitro-cultured Wolffian ducts were treated with collagenase IV, the degree of cross-linked fibrilla collagen was reduced, Wolffian duct elongation and coiling were significantly reduced, and an expanded cyst-like duct was observed. When Wolffian ducts were treated with RAC1 inhibitor NSC23766, mesenchymal fibrilla collagen was disassembled, and Wolffian duct elongation was significantly reduced. Our findings provide evidence that PTK7 regulates ECM integrity and the activity levels of RAC1 and myosin II, which in turn regulates Wolffian duct morphogenesis and therefore, epididymal function.

Reciprocal Spatiotemporally Controlled Apoptosis Regulates Wolffian Duct Cloaca Fusion.

The epithelial Wolffian duct (WD) inserts into the cloaca (primitive bladder) before metanephric kidney development, thereby establishing the initial plumbing for eventual joining of the ureters and bladder. Defects in this process cause common anomalies in the spectrum of congenital anomalies of the kidney and urinary tract (CAKUT). However, developmental, cellular, and molecular mechanisms of WD-cloaca fusion are poorly understood. Through systematic analysis of early WD tip development in mice, we discovered that a novel process of spatiotemporally regulated apoptosis in WD and cloaca was necessary for WD-cloaca fusion. Aberrant RET tyrosine kinase signaling through tyrosine (Y) 1062, to which PI3K- or ERK-activating proteins dock, or Y1015, to which PLCγ docks, has been shown to cause CAKUT-like defects. Cloacal apoptosis did not occur in RetY1062F mutants, in which WDs did not reach the cloaca, or in RetY1015F mutants, in which WD tips reached the cloaca but did not fuse. Moreover, inhibition of ERK or apoptosis prevented WD-cloaca fusion in cultures, and WD-specific genetic deletion of YAP attenuated cloacal apoptosis and WD-cloacal fusion in vivo Thus, cloacal apoptosis requires direct contact and signals from the WD tip and is necessary for WD-cloacal fusion. These findings may explain the mechanisms of many CAKUT.

Mesonephric proliferations of the female genital tract.

The mesonephric (Wolffian) duct regresses in females during embryological development. Remnants of this duct may persist typically along the lateral walls of the cervix, vagina, adnexa, and uterine corpus. These mesonephric epithelia may expand into hyperplastic proliferations and rarely form neoplasms. The spectrum of morphology, immunophenotype, clinical presentation, and molecular characteristics of mesonephric lesions is reviewed, with attention to distinction from entities in the differential diagnosis.

Elimination of the male reproductive tract in the female embryo is promoted by COUP-TFII in mice.

The sexual differentiation paradigm contends that the female pattern of the reproductive system is established by default because the male reproductive tracts (Wolffian ducts) in the female degenerate owing to a lack of androgen. Here, we discovered that female mouse embryos lacking Coup-tfII (chicken ovalbumin upstream promoter transcription factor II) in the Wolffian duct mesenchyme became intersex-possessing both female and male reproductive tracts. Retention of Wolffian ducts was not caused by ectopic androgen production or action. Instead, enhanced phosphorylated extracellular signal-regulated kinase signaling in Wolffian duct epithelium was responsible for the retention of male structures in an androgen-independent manner. We thus suggest that elimination of Wolffian ducts in female embryos is actively promoted by COUP-TFII, which suppresses a mesenchyme-epithelium cross-talk responsible for Wolffian duct maintenance.

Epithelial Wnt/ßcatenin signalling is essential for epididymal coiling.

Organ shape and size are important determinants of their physiological functions. Epithelial tubes are anlagen of many complex organs. How these tubes acquire their complex shape and size is a fundamental question in biology. In male mice, the Wolffian duct (WD; postnatally known as epididymis) undergoes an astonishing transformation, where a straight tube only a few millimetres long elongates to over 1000 times its original length and fits into a very small space, due to extensive coiling of epithelium, to perform the highly specialized function of sperm maturation. Defective coiling disrupts sperm maturation and leads to male infertility. Recent work has shown that epithelial cell proliferation is a major driver of WD coiling. Still, very little is known about the molecular signals involved in this process. Testicular androgens are known regulators of WD development. However, epithelial androgen receptor signalling is dispensable for WD coiling. In this study, we have shown that Wnt signalling is highly active in the entire WD epithelium during its coiling, and is limited to only a few segments of the epididymis in later life. Pharmacological and genetic suppression of Wnt signalling inhibited WD coiling by decreasing cell proliferation and promoting apoptosis. Comparative gene expression analysis identified Fibroblast growth factor 7 (Fgf7) as a prime Wnt target gene involved in WD coiling and in vitro treatment with Fgf7 protein increased coiling of WDs. In summary, our work has established that epithelial canonical Wnt signalling is a critical regulator of WD coiling and its precise regulation is essential for WD/epididymal differentiation.

Protein tyrosine kinase 7 is essential for tubular morphogenesis of the Wolffian duct.

The Wolffian duct, the proximal end of the mesonephric duct, undergoes non-branching morphogenesis to achieve an optimal length and size for sperm maturation. It is important to examine the mechanisms by which the developing mouse Wolffian duct elongates and coils for without proper morphogenesis, male infertility will result. Here we show that highly proliferative epithelial cells divide in a random orientation relative to the elongation axis in the developing Wolffian duct. Convergent extension (CE)-like of cell rearrangements is required for elongating the duct while maintaining a relatively unchanged duct diameter. The Wolffian duct epithelium is planar polarized, which is characterized by oriented cell elongation, oriented cell rearrangements, and polarized activity of regulatory light chain of myosin II. Conditional deletion of protein tyrosine kinase 7 (PTK7), a regulator of planar cell polarity (PCP), from mesoderm results in loss of the PCP characteristics in the Wolffian duct epithelium. Although loss of Ptk7 does not alter cell proliferation or division orientation, it affects CE and leads to the duct with significantly shortened length, increased diameter, and reduced coiling, which eventually results in loss of sperm motility, a key component of sperm maturation. In vitro experiments utilizing inhibitors of myosin II results in reduced elongation and coiling, similar to the phenotype of Ptk7 knockout. This data suggest that PTK7 signaling through myosin II regulates PCP, which in turn ensures CE-like of cell rearrangements to drive elongation and coiling of the Wolffian duct. Therefore, PTK7 is essential for Wolffian duct morphogenesis and male fertility.

FGF8 coordinates tissue elongation and cell epithelialization during early kidney tubulogenesis.

When a tubular structure forms during early embryogenesis, tubular elongation and lumen formation (epithelialization) proceed simultaneously in a spatiotemporally coordinated manner. We here demonstrate, using the Wolffian duct (WD) of early chicken embryos, that this coordination is regulated by the expression of FGF8, which shifts posteriorly during body axis elongation. FGF8 acts as a chemoattractant on the leader cells of the elongating WD and prevents them from epithelialization, whereas static ('rear') cells that receive progressively less FGF8 undergo epithelialization to form a lumen. Thus, FGF8 acts as a binary switch that distinguishes tubular elongation from lumen formation. The posteriorly shifting FGF8 is also known to regulate somite segmentation, suggesting that multiple types of tissue morphogenesis are coordinately regulated by macroscopic changes in body growth.

ROBO2 restricts the nephrogenic field and regulates Wolffian duct-nephrogenic cord separation.

ROBO2 plays a key role in regulating ureteric bud (UB) formation in the embryo, with mutations in humans and mice leading to supernumerary kidneys. Previous studies have established that the number and position of UB outgrowths is determined by the domain of metanephric mesenchymal Gdnf expression, which is expanded anteriorly in Robo2 mouse mutants. To clarify how this phenotype arises, we used high-resolution 3D imaging to reveal an increase in the number of nephrogenic cord cells, leading to extension of the metanephric mesenchyme field in Robo2-null mouse embryos. Ex vivo experiments suggested a dependence of this effect on proliferative signals from the Wolffian duct. Loss of Robo2 resulted in a failure of the normal separation of the mesenchyme from the Wolffian duct/ureteric epithelium, suggesting that aberrant juxtaposition of these two compartments in Robo2-null mice exposes the mesenchyme to abnormally high levels of proliferative stimuli. Our data suggest a new model in which SLIT-ROBO signalling acts not by attenuating Gdnf expression or activity, but instead by limiting epithelial/mesenchymal interactions in the nascent metanephros and restricting the extent of the nephrogenic field. These insights illuminate the aetiology of multiplex kidney formation in human individuals with ROBO2 mutations.

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).

Region-specific regulation of cell proliferation by FGF receptor signaling during the Wolffian duct development.

The Wolffian duct (WD) is a primordium of the male reproductive tract and kidney collecting duct system. Fibroblast growth factor receptors (FGFRs), members of the receptor tyrosine kinase (RTK) family, are essential for kidney development. Although the functions of FGFR signaling in kidney morphogenesis have been analyzed, their function in WD development has not been comprehensively investigated. Here, we demonstrate that Fgfr2 is the major Fgfr gene expressed throughout the WD epithelia and that it is essential for the maintenance of the WD, specifically in the caudal part of the WD. Hoxb7-Cre mediated inactivation of Fgfr2 in the mouse WD epithelia resulted in the regression of the caudal part of the WD and abnormal male reproductive tract development. Cell proliferation and expression of the downstream target genes of RTK signaling (Etv4 and Etv5) were decreased in the caudal part of the WD epithelia in the mutant embryos. Cranial (rostral) WD formation and ureteric budding were not affected. Ret, Etv4, and Etv5 expression were sustained in the ureteric bud of the mutant embryos. Taken together, these data suggest region-specific requirements for FGFR2 signaling in the developing caudal WD epithelia.

Absorption of the Wolffian duct and duplicated ureter by the urogenital sinus: morphological study using human fetuses and embryos.

OBJECTIVES: To describe the embryological origin of the duplicated ureter and to investigate whether the urogenital sinus absorbs not only the Wolffian duct (WD) but also the ureter. MATERIALS AND METHODS: During studies using sections of human fetuses (45 specimens), we incidentally found a specific type of ureteric duplication (at ~7 weeks) in which two unilateral ureters joined at the vesico-ureteric junction, apparently representing a morphology arising at an intermediate stage between complete and partial ureteric duplication. The existing literature lacks any photographic representation of early development of the vesico-ureteric junction, and we therefore studied horizontal sections of 10 human embryos (at ~5-6 weeks' gestation) in which the ureter did not join the urogenital sinus (future bladder) but instead joined the WD (future vas deferens). RESULTS: The sinus consistently showed a reversed Y-shape, the arms of which extended posteriorly to receive the WD. When absorption of the duct into the sinus wall reached the distal end of the ureter, the arm-like parts appeared to enlarge posteriorly for further involvement of the duct, with little or no incorporation of the ureter; therefore, the future trigone of the bladder might develop from these arm-like parts of the sinus posterior wall. Consequently, in the case of ureteric duplication included in the present study, it is considered that the ureters would probably have merged with the WD at closely adjacent sites. CONCLUSION: The present study represents the first photographic illustration of the early development of the human vesico-ureteric junction.

[Müllerian anomalies. Obstructed hemivagina and ipsilateral renal anomaly syndrome (OHVIRA)]. / Malformaciones müllerianas. Síndrome de hemivagina obstruida y anomalía renal ipsilateral (OHVIRA).

Müllerian duct anomalies are a group of uncommon and underdiagnosed entities, which cause specific symptoms in adolescent females and may be associated with infertility as well as adverse pregnancy outcomes. These malformations occur as a result of an arrest or abnormal development of the Müllerian ducts in different stages of the female reproductive tract during gestation. Obstructed hemivagina and ipsilateral renal anomaly syndrome (OHVIRA), formerly known as the Herlyn-Werner-Wunderlich syndrome, is a rare entity characterized by the presence of a uterus didelphys with an obstructed hemivagina cause by a vaginal septum and the association of a renal anomaly (most commonly renal agenesis) ipsilateral to the obstruction. This syndrome may remain undiagnosed during childhood and usually becomes symptomatic after menarche, causing obstructive symptoms. Occasionally it may be identified after the evaluation of a patient with infertility or recurrent pregnancy loss. The clinical diagnosis is very challenging and requires imaging studies in which ultrasound and MRI play an essential role in the diagnosis, classification and treatment plan. Opportune diagnosis and treatment achieve complete improvement of symptoms, adequate reproductive prognosis and avoid major complications such as endometriosis, pelvic adhesions and infertility. The purpose of this review is to demonstrate the pathophysiology, clinical manifestations, diagnostic methods and treatment of the obstructed hemivagina and ipsilateral renal anomaly syndrome.

Las malformaciones de los conductos de Müller son un grupo de entidades raras y poco diagnosticadas que ocasionan síntomas inespecíficos en adolescentes y pueden acompañarse de problemas de infertilidad y RESULTADOS obstétricos adversos. Estas malformaciones ocurren durante la gestación como consecuencia del desarrollo anormal de los conductos de Müller en diferentes etapas del proceso de formación del aparato reproductor femenino. El síndrome de hemivagina obstruida y anomalía renal ipsilateral, antes conocido como el síndrome de Herlyn-Werner-Wünderlich, es un padecimiento poco común, caracterizado por útero didelfo con una hemivagina obstruida por un tabique vaginal, y la asociación de una anomalía renal (agenesia renal principalmente) ipsilateral a la obstrucción. Este síndrome rara vez se identifica durante la niñez y se vuelve sintomático posterior a la menarquia, ocasionado por los síntomas obstructivos. A veces se identifica posterior a la evaluación de una paciente con problemas de infertilidad o pérdidas gestacionales recurrentes. El diagnóstico clínico es difícil, por eso se requieren estudios de imagen en los que el ultrasonido y la resonancia magnética desempeñan un papel decisivo para el diagnóstico, clasificación y plan terapéutico. El diagnóstico y tratamiento oportunos logran la desaparición de los síntomas, con pronóstico reproductivo adecuado, y se evitan las principales complicaciones: endometriosis, adherencias pélvicas e infertilidad. OBJETIVO: mostrar la fisiopatología, las manifestaciones clínicas, los métodos diagnósticos y terapéuticos del síndrome de hemivagina obstruida y anomalía renal ipsilateral.

Role of Wnt5a-Ror2 signaling in morphogenesis of the metanephric mesenchyme during ureteric budding.

Development of the metanephric kidney begins with the induction of a single ureteric bud (UB) on the caudal Wolffian duct (WD) in response to GDNF (glial cell line-derived neurotrophic factor) produced by the adjacent metanephric mesenchyme (MM). Mutual interaction between the UB and MM maintains expression of GDNF in the MM, thereby supporting further outgrowth and branching morphogenesis of the UB, while the MM also grows and aggregates around the branched tips of the UB. Ror2, a member of the Ror family of receptor tyrosine kinases, has been shown to act as a receptor for Wnt5a to mediate noncanonical Wnt signaling. We show that Ror2 is predominantly expressed in the MM during UB induction and that Ror2- and Wnt5a-deficient mice exhibit duplicated ureters and kidneys due to ectopic UB induction. During initial UB formation, these mutant embryos show dysregulated positioning of the MM, resulting in spatiotemporally aberrant interaction between the MM and WD, which provides the WD with inappropriate GDNF signaling. Furthermore, the numbers of proliferating cells in the mutant MM are markedly reduced compared to the wild-type MM. These results indicate an important role of Wnt5a-Ror2 signaling in morphogenesis of the MM to ensure proper epithelial tubular formation of the UB required for kidney development.

Novel roles of Pkd2 in male reproductive system development.

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited genetic diseases, caused by mutations in PKD1 and/ or PKD2. Infertility and reproductive tract abnormalities in male ADPKD patients are very common and have higher incidence than in the general population. In this work, we reveal novel roles of Pkd2 for male reproductive system development. Disruption of Pkd2 caused dilation of mesonephric tubules/efferent ducts, failure of epididymal coiling, and defective testicular development. Deletion of Pkd2 in the epithelia alone was sufficient to cause reproductive tract defects seen in Pkd2(-/-) mice, suggesting that epithelial Pkd2 plays a pivotal role for development and maintenance of the male reproductive tract. In the testis, Pkd2 also plays a role in interstitial tissue and testicular cord development. In-depth analysis of epithelial-specific knockout mice revealed that Pkd2 is critical to maintain cellular phenotype and developmental signaling in the male reproductive system. Taken together, our data for the first time reveal novel roles for Pkd2 in male reproductive system development and provide new insights in male reproductive system abnormality and infertility in ADPKD patients.

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.

Interepithelial signaling with nephric duct is required for the formation of overlying coelomic epithelial cell sheet.

In most organs of the body, epithelial tissues are supported by their own basement membrane and underlying stroma, the latter being regarded as a complex of amorphous cells, extracellular matrices, and soluble factors. We demonstrate here that an epithelial tube can serve as a component of stroma that supports the formation of epithelial cell sheet derived from a different origin. During development of the mesonephros in chicken embryos, the intermediate mesoderm (IMM), which contains the Wolffian duct (WD) and its associated tubules, is overlain by a sheet of epithelial cells derived from lateral plate (coelomic) mesoderm. We describe that in normal embryos, epitheliogenesis of IMM tubes and the adjacent coelomic cell sheet proceed in a coordinated manner. When the WD was surgically ablated, the overlying coelomic epithelium exhibited aberrant morphology accompanied by a punctated basement membrane. Furthermore, the WD-ablated coelomic epithelium became susceptible to latent external stress; electroporation of Rac1 resulted in epithelial-to-mesenchymal transitions (EMTs) within the coelomic epithelium. The distorted coelomic epithelium was rescued by implanting fibronectin-producing cells in place of the WD, suggesting that fibronectin provided by WD has an important role acting interepithelially. This notion was corroborated further by directly visualizing a translocation of EGFP-tagged fibronectin from fibronectin-producing to -receiving epithelia in vivo. Our findings provide a novel insight into interepithelial signaling that also might occur in adult tissues to protect against EMT and suggest a possible new target for anticancer therapeutic strategy.

Preformed Wolffian duct regulates Müllerian duct elongation independently of canonical Wnt signaling or Lhx1 expression.

The Müllerian duct gives rise to female reproductive organs, such as the oviduct and uterus. During gestation, the Wolffian duct, which generates male reproductive organs and the kidney, is formed, and the Müllerian duct then elongates caudally along the preformed Wolffian duct. Anatomical separation of these two ducts in chick embryos demonstrated that the Wolffian duct is required for Müllerian duct formation. Likewise, a few reports supported this notion in mice, including studies on Wnt9b mutant mice and Wolffian duct-specific Lhx1 deletion. However, anatomical ablation of the Wolffian duct has not been established in mice. In this study, we addressed the importance of the interaction between these two reproductive ducts, by generating mice that specifically expressed a diphtheria toxin subunit in the Wolffian duct. While this genetic ablation of the Wolffian duct resulted in kidney hypoplasia/agenesis in both male and female mutant mice, the female mutant mice lacked the uterus, which is derived from the Müllerian duct. At mid-gestation, the Müllerian duct was truncated at the level where the mutant Wolffian duct was prematurely terminated, meaning that Müllerian duct elongation was dependent on the preformed Wolffian duct. However, Wnt9b expression in the Wolffian duct and the resultant canonical Wnt activity, as well as Lhx1 expression, were not affected in the mutant mice. These results suggest that the Wolffian duct regulates Müllerian duct elongation by currently unidentified mechanisms that are independent of canonical Wnt signaling or Lhx1 expression.