Development Of Urogenital Tract Research Articles

O-116 Genetic association analyses identify links between pelvic prolapse (PP) and connective tissue biology, cardiovascular and reproductive health

Abstract Study question Can genome-wide association analysis unravel the biological underpinnings of PP and facilitate personalized risk assessment via genetic risk scores construction? Summary answer We unravel novel links with urogenital development and vascular health in PP and present polygenic risk score as a tool to stratify PP risk. What is known already Prolapse is characterized by a descent of the pelvic organs into the vaginal cavity. PP affects around 40% of women after menopause and is the main indication for major gynecological surgery, having an important health, social and economic burden. Although the etiology and biological mechanisms underlying PP remain poorly understood, prior studies suggest genetic factors might play a role. Recently, a genome-wide association study (GWAS) identified seven genome-wide significant loci, located in or near genes involved in connective tissue metabolism and estrogen exposure in the etiology of PP. Study design, size, duration We conducted a three-stage case-control genome-wide association study. Firstly, in the discovery phase, we meta-analyzed Icelandic, UK Biobank and the FinnGen R3 datasets, comprising a total of 20118 cases and 427426 controls of European ancestry. For replication we used an independent dataset from Estonian Biobank (7968 cases and 118895 controls). Finally, we conducted a joint meta-analysis, containing 28086 cases and 546321 controls, which is the largest GWAS of PP to date. Participants/materials, setting, methods We performed functional annotation on genetic variants unraveled by GWAS and integrated these with expression quantitative trait loci and chromatin interaction data. In addition, we looked at enrichment of association signal on gene-set, tissue and cell type level and analyzed associations with other phenotypes both on genetic and phenotypic level. Colocalisation analyses were conducted to help pinpoint causal genes. We further constructed polygenic risk scores to explore options for personalized risk assessment and prevention. Main results and the role of chance In the discovery phase, we identified 18 genetic loci and 20 genetic variants significantly associated with POP (p < 5 × 10−8) and 75% of the variants show nominal significance association (p < 0.05) in the replication. Notably, the joint meta-analyses detected 20 genetic loci significantly associated with POP, from which 13 loci were novel. Novel genetic variants are located in or near genes involved in gestational duration and preterm birth (rs2687728 p = 2.19x10-9, EEFSEC), cardiovascular health and pregnancy success (rs1247943 p = 5.83x10-18, KLF13), endometriosis (rs12325192 p = 3.72x10-18, CRISPLD2), urogenital tract development (rs7126322, p = 4.35x10-15, WT1 and rs42400, p = 4.8x10-10, ADAMTS16) and regulation of the oxytocin receptor (rs2267372, p = 4.49x10-13, MAFF). Further analyses demonstrated that POP GWAS signals colocalise with several eQTLS (including EEFSEC, MAFF, KLF13, etc.), providing further evidence for mapping associated genes. Tissue and cell enrichment analyses underlined the role of the urogenital system, muscle cells, myocytes and adipocytes (p < 0.00001, FDR<0.05). Furthermore, genetic correlation analyses supported a shared genetic background with gastrointestinal disorders, joint and musculoskeletal disorders and cardiovascular disease. Polygenic risk scores analyses included a total of 125551 people in the target dataset, with 5379 prevalent patients and 2517 incident patients. Analyzing the best GRS as a quintile showed association with incident disease (Harrell c-statistic= 0.603, SD = 0.006). Limitations, reasons for caution This GWAS meta-analyses focused on European ancestry populations, which challenges the generalizability of GWAS findings to non-European populations. Moreover, this study included women with PP from population-based biobanks identified using the ICD-10 code N81, which limits analyses considering different disease stages and severity. Wider implications of the findings Our study provides genetic evidence to improve the current understanding of PP pathogenesis and serves as basis for further functional studies. Moreover, we provide a genetic tool for personalized risk stratification, which could help prevent PP development and improve the quality of a vast quantity of women. Trial registration number not applicable

Evaluation of Mayer-Rokitansky-Kuster-Hauser (MRKH) Patient Families by Whole Genome Sequencing

Introduction: MRKH is a characterized by the congenital absence of the uterus and vagina in 46,XX individuals. A subset of these patients also has associated renal, skeletal, cardiac and/or auditory defects. Familial cases suggest a genetic component, but to date only pathogenic variants in WNT4 and HNF1B have been confirmed. We hypothesize that de novo heterozygous variants in candidate genes will be present in some patients with MRKH. Methods: DNAs from 30 quads (an MRKH proband and three relatives) were subjected to whole genome sequencing (WGS), and heterozygous variants in coding regions with < 0.02 frequency were filtered by two different methods. In the first approach, variants were filtered by 1) top consequence variant (splice site, stop-gain, frameshift, and missense, respectively); 2) impact score; 3) mapping quality; 4) cytobands; 5) intolerance; 6) de novo variants; and 7) plausibility based on familial genotype. The second approach considered only heterozygous variants found in the proband and absent in all other family members, which were then filtered by top consequence (splice donor and acceptor sites, stop-gain, frameshift). Results: Five pedigrees were excluded for inadequate sequence in one or more individuals. 55,033 variants in coding regions with < 2% frequency were identified in the 25 remaining quads for analysis. Using the first approach, 42 candidate gene variants in 32 genes were identified - 12 splice variants, 10 stop-gains, 15 frameshift variants and 5 missense variants. Of these, MUC22 contained 2 missense variants from different families. Additionally, DICER1 had multiple splice variants and is essential for mouse urogenital tract development. In the second approach, 39 candidate genes were identified—6 splice variants in 6 genes, 18 stop-gains in 17 genes, and 17 frameshift variants in 16 genes. Zinc finger genes (ZNF418, ZNF646, ZNF135, and ZNF772) comprised the most frequent class of the 39 genes. Two genes (MIR4436A and ZNF418) contained attractive variants in two different families. Conclusion: WGS has been shown to improve detection of gene variants in coding regions, more so than whole exome sequencing (WES). We previously performed WES on 111 MRKH probands without family members and analyzed variants in candidate genes suggested by mouse and preliminary human studies. Interestingly, in this study, only three genes overlapped with previously suspected candidate genes. Here, we identified new candidates based upon potential deleteriousness. These candidate genes will be studied further in our families to determine their role in Mullerian development.

Embryology of the urogenital tract; a practical overview for urogynecologic surgeons.

Urinary tract anomalies are one of the most common birth defects. Nevertheless, they prove challenging to diagnose as a result of variable presenting symptoms. We aimed to perform a review of urogenital tract development, highlight common congenital upper urinary tract anomalies encountered by urogynecologists and tools to facilitate diagnosis. Multiple searches were performed utilizing resources such as PubMed and the TriHealth library database to access publications related to embryology of the urinary tract and urinary tract anomalies. Each citation was reviewed. Congenital urinary tract anomalies account for up to 20% of all birth defects and occur more often in females. The true incidence of these malformations is unknown as some can remain clinically insignificant throughout life. In addition, patients may present with non-specific complaints such as urinary tract infections, nephrolithiasis or urinary incontinence. Therefore, unsuspected anomalies pose a risk of delayed diagnosis and potential injury during urogynecologic surgery. Imaging modalities such as computed tomography or magnetic resonance imaging are the most common diagnostic tests. Management and treatment options range from observation to surgical resection with the goal of optimizing long-term functionality and prevention of chronic sequelae. Patients with urinary tract anomalies can present with vague complaints often encountered by urogynecologists. It is crucial to understand the embryologic development of urinary tract anomalies to help facilitate diagnosis and guide care within the office and operating room setting.

Interactive Effects of Perinatal BPA or DES and Adult Testosterone and Estradiol Exposure on Adult Urethral Obstruction and Bladder, Kidney, and Prostate Pathology in Male Mice.

Obstructive voiding disorder (OVD) occurs during aging in men and is often, but not always, associated with increased prostate size, due to benign prostatic hyperplasia (BPH), prostatitis, or prostate cancer. Estrogens are known to impact the development of both OVD and prostate diseases, either during early urogenital tract development in fetal–neonatal life or later in adulthood. To examine the potential interaction between developmental and adult estrogen exposure on the adult urogenital tract, male CD-1 mice were perinatally exposed to bisphenol A (BPA), diethylstilbestrol (DES) as a positive control, or vehicle negative control, and in adulthood were treated for 4 months with Silastic capsules containing testosterone and estradiol (T+E2) or empty capsules. Animals exposed to BPA or DES during perinatal development were more likely than negative controls to have urine flow/kidney problems and enlarged bladders, as well as enlarged prostates. OVD in adult T+E2-treated perinatal BPA and DES animals was associated with dorsal prostate hyperplasia and prostatitis. The results demonstrate a relationship between elevated exogenous estrogen levels during urogenital system development and elevated estradiol in adulthood and OVD in male mice. These findings support the two-hit hypothesis for the development of OVD and prostate diseases.

Identification of gene variants in 130 Han Chinese patients with hypospadias by targeted next-generation sequencing.

BackgroundHypospadias is a common congenital malformation of male external genitalia, which mainly manifests as an abnormal urethral opening on the ventral side of the penis. The etiology and clinical phenotype of hypospadias is highly heterogeneous, and its clinical diagnosis is challenging. Currently, over 70% of patients have an unknown etiology. Here, we performed a targeted analysis of gene mutations in 130 patients with hypospadias of unknown etiology to find the precise genetic cause.MethodsWe developed a targeted next‐generation sequencing (NGS) panel, encompassing the exon coding regions of 105 genes involved in external genitalia and urogenital tract development and performed sequencing analysis on 130 children with hypospadias of unknown etiology.ResultsIn total, 25 patients with hypospadias (19.2%) were found to have 20 mutations among the nine genes involved in external genitalia and urogenital tract development, including 16 reported and four novel mutation sites. Twenty‐two patients (16.9%) had diagnostic variants. Multiple genetic mutations were identified in three of the 25 patients. Hypospadias combined with micropenis was the most common phenotype (68%) in 25 patients.ConclusionsHigher frequency mutations were identified in SRD5A2 (52%) and AR (24%) in our patient cohort. Middle or posterior hypospadias with micropenis may be significant indicators of genetic variations. Polygenic inheritance may be a rare genetic cause of hypospadias.

Uterine differentiation as a foundation for subsequent fertility

Uterine differentiation in cattle and sheep begins prenatally, but is completed postnatally. Mechanisms regulating this process are not well defined. However, studies of urogenital tract development in murine systems, particularly those involving tissue recombination and targeted gene mutation, indicate that the ideal uterine organizational programme evolves epigenetically through dynamic cell-cell and cell-matrix interactions that define the microenvironmental context within which gene expression occurs and may ensure adult tissue stability. In the cow and ewe, transient postnatal exposure of the developing uterus to steroids can produce immutable changes in adult uterine tissues that may alter the embryotrophic potential of the uterine environment. Thus, success of steroid-sensitive postnatal events supporting uterine growth and development can dictate the functional potential of the adult uterus. Studies to determine effects of specific steroidal agents on patterns of uterine development during defined neonatal periods, as well as the functional consequences of targeted neonatal steroid exposure in the adult uterus, should enable identification of critical developmental mechanisms and determinants of uterine integrity and function. Extreme adult uterine phenotypes (lesion models) created in cattle and sheep by strategic postnatal steroid exposure hold promise as powerful tools for the study of factors affecting uterine function and the rapid identification of novel uterine genes.

Expression of androgen, estrogen, and progesterone hormone receptors in the penile tissues of children with different types of hypospadias.

OBJECTIVE:Androgen (AR), Estrogen (ER) and Progesterone (PR) hormones play an important role in the prenatal and postnatal development of urogenital tract and especially the penis. The expressions of AR, ER and PR receptors in penile tissues in children with hypospadiases had also been shown previously. In this leading study, to demonstrate of the sex hormone receptor expression in cases with different types of hypospadias were aimed.METHODS:This study was designed in children operated due to hypospadiases without DSD. Biopsy samples of 3 mm’s were obtained from three different sytes as the lateral parameatal tissue and the anterior corner of the prepuce, and inner layer of posterior prepuce. The presence of AR, ER and PR receptors was investigated immunehistochemically.RESULTS:Mean age was 5.4 years in 18 children with hypospadiases; in totally 33 specimens were taken in 5 subcoronal as 5 specimens, and 7 penile as 15 specimens, and 6 penoscrotal as 13 specimens. According to sytes of samples; 13 samples were from lateral para-meatal tissues, and 13 were from anterior corners of prepuces, and 7 were from inner layers of posterior prepuces. In regard to receptor expression; ER and AR receptors were positive in 29 (87.8%) and 12 (36.4%) respectively; PR receptors were negative.CONCLUSION:This study emphasized the dominant expression of estrogen receptors in penile tissues of children with hypospadias. Although there was not a manifest correlation of androgen receptors absence in regard to the severity of hypospadias patients, there was a marked estrogen receptors presence in penile tissues. These findings suggest that the disrupted androgen and estrogen receptor interaction and/or balance could play a role during the development of external genitalia in hypospadias patients. Progesterone receptor was not present and therefore the active role in the postnatal development of hypospadias is still debatable.

Genome-wide linkage and association study implicates the 10q26 region as a major genetic contributor to primary nonsyndromic vesicoureteric reflux

Vesicoureteric reflux (VUR) is the commonest urological anomaly in children. Despite treatment improvements, associated renal lesions – congenital dysplasia, acquired scarring or both – are a common cause of childhood hypertension and renal failure. Primary VUR is familial, with transmission rate and sibling risk both approaching 50%, and appears highly genetically heterogeneous. It is often associated with other developmental anomalies of the urinary tract, emphasising its etiology as a disorder of urogenital tract development. We conducted a genome-wide linkage and association study in three European populations to search for loci predisposing to VUR. Family-based association analysis of 1098 parent-affected-child trios and case/control association analysis of 1147 cases and 3789 controls did not reveal any compelling associations, but parametric linkage analysis of 460 families (1062 affected individuals) under a dominant model identified a single region, on 10q26, that showed strong linkage (HLOD = 4.90; ZLRLOD = 4.39) to VUR. The ~9Mb region contains 69 genes, including some good biological candidates. Resequencing this region in selected individuals did not clearly implicate any gene but FOXI2, FANK1 and GLRX3 remain candidates for further investigation. This, the largest genetic study of VUR to date, highlights the 10q26 region as a major genetic contributor to VUR in European populations.

Expression profiles of human epididymis epithelial cells reveal the functional diversity of caput, corpus and cauda regions.

Region-specific transcriptional profiling of tissues and cultured epithelial cells from the human epididymis will predict functional specialization along the duct. We identified the molecular signature driving functions of the caput, corpus and cauda epithelium, and determined how these differ to establish the regional differentiation of the organ. The epithelium lining the human male genital ducts has a critical role in fertility. In particular, it controls the luminal environment in the epididymis, which is required for normal sperm maturation and reproductive competence. Studies in many animal species have largely informed our understanding of the molecular basis of epididymis function. However, there are substantial differences between species. Using RNA sequencing on biological replicates, we described gene expression profiles for tissue from each region of the epididymis and cultured epithelial cells derived from these regions. Bioinformatic tools were then utilized to identify differentially expressed genes (DEGs) between tissues and cells from the caput, corpus and cauda. The data showed that the caput is functionally divergent from the corpus and cauda, which have very similar transcriptomes. Interrogation of DEGs using gene ontology process enrichment analyses showed that processes of ion transport, response to hormone stimulus and urogenital tract development are more evident in the caput, while defense response processes are more important in the corpus/cauda. Consistent with these regional differences in epididymis function, we observed differential expression of transcription factors in the caput and corpus/cauda. Cultured caput, corpus and cauda cells may not faithfully represent the same cells in the intact organ, due to loss of hormonal signals from the testis and communication from other cell types. Our data provide a molecular characterization that will facilitate advances in understanding human epididymis epithelium biology in health and disease. They may also reveal the mechanisms coordinating epididymis luminal environment and sperm maturation. Data deposited at http://www.ncbi.nlm.nih.gov/geo/GSE72986. This work was supported by the National Institutes of Health: R01HD068901 (PI: A.H.). The authors declare no conflict of interest.

Open chromatin mapping identifies transcriptional networks regulating human epididymis epithelial function

The epithelium lining the epididymis in the male reproductive tract maintains a luminal environment that promotes sperm cell maturation. This process is dependent on the coordinated expression of many genes that encode proteins with a role in epithelial transport. We previously generated genome-wide maps of open chromatin in primary human epididymis epithelial (HEE) cells to identify potential regulatory elements controlling coordinated gene expression in the epididymis epithelium. Subsequent in silico analysis identified transcription factor-binding sites (TFBS) that were over-represented in the HEE open chromatin, including the motif for paired box 2 (PAX2). PAX2 is a critical transcriptional regulator of urogenital tract development, which has been well studied in the kidney but is unexplored in the epididymis. Due to the limited lifespan of primary HEE cells in culture, we investigated the role of PAX2 in an immortalized HEE cell line (REP). First, REP cells were evaluated by DNase I digestion followed by high-throughput sequencing and the PAX2-binding motif was again identified as an over-represented TFBS within intergenic open chromatin, though on fewer chromosomes than in the primary HEE cells. To identify PAX2-target genes in REP cells, RNA-seq analysis was performed after siRNA-mediated depletion of PAX2 and compared with that with a non-targeting siRNA. In response to PAX2-repression, 3135 transcripts were differentially expressed (1333 up-regulated and 1802 down-regulated). Novel PAX2 targets included multiple genes encoding proteins with predicted functions in the epididymis epithelium.

Genetic analyses reveal a requirement for Dicer1 in the mouse urogenital tract

Despite the increasing interest in other classes of small RNAs, microRNAs (miRNAs) remain the most widely investigated and have been shown to play a role in a number of different processes in mammals. Many studies investigating miRNA function focus on the processing enzyme Dicer1, which is an RNAseIII protein essential for the biogenesis of active miRNAs through its cleavage of precursor RNA molecules. General deletion of Dicer1 in the mouse confirms that miRNAs are essential for development because embryos lacking Dicer1 fail to reach the end of gastrulation. Here we investigate the role of Dicer1 in urogenital tract development. We utilised a conditional allele of the Dicer1 gene and two Cre-expressing lines, driven by HoxB7 and Amhr2, to investigate the effect of Dicer1 deletion on both male and female reproductive tract development. Data presented here highlight an essential role for Dicer1 in the correct morphogenesis and function of the female reproductive tract and confirm recent findings that suggest Dicer1 is required for female fertility. In addition, HoxB7:Cre-mediated deletion in ureteric bud derivatives leads to a spectrum of anomalies in both males and females, including hydronephrotic kidneys and kidney parenchymal cysts. Male reproductive tract development, however, remains largely unaffected in the absence of Dicer1. Thus, Dicer1 is required for development of the female reproductive tract and also normal kidney morphogenesis.

Using mouse models to understand normal and abnormal urogenital tract development

Removal of toxic substances from the blood depends on patent connections between the kidneys, ureters and bladder that are established when the ureter is transposed from its original insertion site in the Wolffian duct, to the bladder trigone, its final insertion site. According to the Ureteric Bud Theory of Mackie and Stephens, this repositioning of the ureter orifice occurs as the trigone forms from the common nephric duct, the caudal-most Wolffian duct segment. The availability of mouse models has enabled us to re-examine this hypothesis in the context of normal and abnormal development. We find than in contrast to what has been previously thought, the common nephric duct does not differentiate into the bladder trigone but instead undergoes apoptosis, a crucial step in ureter transposition. Interestingly, apoptosis only occurs in close proximity with the sinus ridge, a raised epithelial structure located at the dorsal aspect of the urogenital sinus, suggesting that signals from this site may be important for normal ureter insertion. These studies provide new insights into the normal process of ureter maturation, and shed light on possible causes of obstruction and reflux, ureteral abnormalities that affect 1–2% of the human population.

GUDMAP

In late 2004, an International Consortium of research groups were charged with the task of producing a high-quality molecular anatomy of the developing mammalian urogenital tract (UGT). Given the importance of these organ systems for human health and reproduction, the need for a systematic molecular and cellular description of their developmental programs was deemed a high priority. The information obtained through this initiative is anticipated to enable the highest level of basic and clinical research grounded on a 21st-century view of the developing anatomy. There are three components to the Genitourinary Developmental Molecular Anatomy Project GUDMAP; all of these are intended to provide resources that support research on the kidney and UGT. The first provides ontology of the cell types during UGT development and the molecular hallmarks of those cells as discerned by a variety of procedures, including in situ hybridization, transcriptional profiling, and immunostaining. The second generates novel mouse strains. In these strains, cell types of particular interest within an organ are labeled through the introduction of a specific marker into the context of a gene that exhibits appropriate cell type or structure-specific expression. In addition, the targeting construct enables genetic manipulation within the cell of interest in many of the strains. Finally, the information is annotated, collated, and promptly released at regular intervals, before publication, through a database that is accessed through a Web portal. Presented here is a brief overview of the Genitourinary Developmental Molecular Anatomy Project effort.

Lack of TCF2/vHNF1 in mice leads to pancreas agenesis

Heterozygous mutations in the human POU-homeobox TCF2 (vHNF1, HNF1beta) gene are associated with maturity-onset diabetes of the young, type 5, and abnormal urogenital tract development. Recently, pancreas atrophies have been reported in several maturity-onset diabetes of the young type 5 patients, suggesting that TCF2 is required not only for adult pancreas function but also for its normal development. Tcf2-deficient mice die before gastrulation because of defective visceral endoderm formation. To investigate the role of this factor in pancreas development, we rescued this early lethality by tetraploid aggregation. We show that TCF2 has an essential function in the first steps of pancreas development, correlated with its expression domain that demarcates the entire pancreatic buds from the earliest stages. Lack of TCF2 results in pancreas agenesis by embryonic day 13.5. At earlier stages, only a dorsal bud rudiment forms transiently and expresses the transcription factors Ipf1 and Hlxb9 but lacks the key transcription factor involved in the acquisition of a pancreatic fate, Ptf1a, as well as all endocrine precursor cells. Regional specification of the gut also is perturbed in Tcf2-/- embryos as manifested by ectopic expression of Shh and lack of Ihh and Ipf1 in the posterior stomach and duodenum. Our results highlight the requirement of Tcf2 for ensuring both accurate expression of key regulator molecules in the stomach-duodenal epithelium and proper acquisition of the pancreatic fate. This study provides further insights into early molecular events controlling pancreas development and may contribute to the development of cell-replacement strategies for diabetes.

Urogenital Tract Expression of Enhanced Green Fluorescent Protein in Transgenic Mice Driven by a Smooth Muscle γ-Actin Promoter

Our understanding of urogenital tract development and its response to disease or injury is hindered by complex interactions between epithelial and mesenchymal cells, and the difficulties in studying either component in isolation. We investigated whether transgenic mice could be generated to express enhanced green fluorescent protein (EGFP) in smooth muscle cells (SMCs) and whether such cells could then be purified using flow cytometric sorting to isolate RNA to be used in future gene expression assays. A 13.7 kb mouse smooth muscle gamma-actin promoter fragment was ligated to an EGFP reporter gene and microinjected into male mouse pronuclei. Adult transgenic mice were sacrificed and urogenital tissues were removed for histological and immunohistochemical studies. In other animals conditions were determined for dissociating bladder cells and the subsequent purification of bladder SMCs by sorting. Six lines of transgenic mice were generated (transgene copy numbers 1 to 30). EGFP was expressed in all smooth muscle beds examined except those associated with small blood vessels. EGFP levels appeared to correlate with transgene copy number. Histological and immunohistochemical analysis confirmed that reporter gene expression was restricted to SMCs of all tissues examined. Parameters for generating bladder cell suspensions were established and EGFP labeled bladder SMCs were identified by flow cytometric analysis. Several lines of transgenic mice have been generated in which SMCs of urogenital tissues have been labeled with EGFP and pure populations of SMCs have been obtained. The methods established for the rapid dissociation and purification of bladder SMCs should minimize degradative changes. These approaches may enable us to address issues involving bladder SMC development and differentiation as well as the response to injury and disease by performing transcriptome wide analyses on purified SMC populations.

Transcriptional repression of peri-implantation EMX2 expression in mammalian reproduction by HOXA10.

HOXA10 is necessary for mammalian reproduction; however, its transcriptional targets are not completely defined. EMX2, a divergent homeobox gene, is necessary for urogenital tract development. In these studies we identify and characterize the regulation of EMX2 by HOXA10. By using Northern analysis and in situ hybridization, we found that EMX2 is expressed in the adult urogenital tract in an inverse temporal pattern from HOXA10, suggestive of a negative regulatory relationship. Constitutive expression of HOXA10 diminished EMX2 mRNA, whereas blocking HOXA10 through the use of antisense resulted in high EMX2 mRNA expression. Deletional analysis of the EMX2 5' regulatory region revealed that a 150-bp element mediated transcriptional repression when cotransfected with pcDNA3.1/HOXA10 in transient-transfection assays. Binding of HOXA10 protein to this element was demonstrated by electrophoretic mobility shift assay and further localized to a consensus HOXA10 binding site within this element by DNase I footprinting. Site-directed mutagenesis abolished binding, as well as the negative transcriptional regulation. Transcriptional activation of empty spiracles, the Drosophila ortholog of EMX2, by Abdominal-B (HOXA10 ortholog) has been previously demonstrated. These findings demonstrate conservation of the transcription factor-target gene relationship, although the direction of regulation is reversed with possible evolutionary implications.

PAX genes in development and disease: the role of PAX2 in urogenital tract development.

PAX genes play an important role in fetal development. Moreover, heterozygous mutations in several PAX genes cause human disease. Here we review the role of PAX2 in kidney development, focusing on the morphological effects of PAX2 mutations. We discuss the role of PAX2 in the context of an inhibitory field model of kidney branching morphogenesis and summarize recent progress in this area.