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

The genetics and pathogenesis of CAKUT

Congenital anomalies of the kidney and urinary tract (CAKUT) comprise a large variety of malformations that arise from defective kidney or urinary tract development and frequently lead to kidney failure. The clinical spectrum ranges from severe malformations, such as renal agenesis, to potentially milder manifestations, such as vesicoureteral reflux. Almost 50% of cases of chronic kidney disease that manifest within the first three decades of life are caused by CAKUT. Evidence suggests that a large number of CAKUT are genetic in origin. To date, mutations in ~54 genes have been identified as monogenic causes of CAKUT, contributing to 12-20% of the aetiology of the disease. Pathogenic copy number variants have also been shown to cause CAKUT and can be detected in 4-11% of patients. Furthermore, environmental and epigenetic factors can increase the risk of CAKUT. The discovery of novel CAKUT-causing genes is challenging owing to variable expressivity, incomplete penetrance and variable genotype-phenotype correlation. However, such a discovery could ultimately lead to improvements in the accurate molecular genetic diagnosis, assessment of prognosis and multidisciplinary clinical management of patients with CAKUT, potentially including personalized therapeutic approaches.

MicroRNAs in kidney development and disease

MicroRNAs (miRNAs) belong to a class of endogenous small noncoding RNAs that regulate gene expression at the posttranscriptional level, through both translational repression and mRNA destabilization. They are key regulators of kidney morphogenesis, modulating diverse biological processes in different renal cell lineages. Dysregulation of miRNA expression disrupts early kidney development and has been implicated in the pathogenesis of developmental kidney diseases. In this Review, we summarize current knowledge of miRNA biogenesis and function and discuss in detail the role of miRNAs in kidney morphogenesis and developmental kidney diseases, including congenital anomalies of the kidney and urinary tract and Wilms tumor. We conclude by discussing the utility of miRNAs as potentially novel biomarkers and therapeutic agents.

DICER1 tumor predisposition syndrome: an evolving story initiated with the pleuropulmonary blastoma

DICER1 syndrome (OMIM 606241, 601200) is a rare autosomal dominant familial tumor predisposition disorder with a heterozygous DICER1 germline mutation. The most common tumor seen clinically is the pleuropulmonary blastoma (PPB), a lung neoplasm of early childhood which is classified on its morphologic features into four types (IR, I, II and III) with tumor progression over time within the first 4-5 years of life from the prognostically favorable cystic type I to the unfavorable solid type III. Following the initial report of PPB, its association with other cystic neoplasms was demonstrated in family studies. The detection of the germline mutation in DICER1 provided the opportunity to identify and continue to recognize a number seemingly unrelated extrapulmonary neoplasms: Sertoli-Leydig cell tumor, gynandroblastoma, embryonal rhabdomyosarcomas of the cervix and other sites, multinodular goiter, differentiated and poorly differentiated thyroid carcinoma, cervical-thyroid teratoma, cystic nephroma-anaplastic sarcoma of kidney, nasal chondromesenchymal hamartoma, intestinal juvenile-like hamartomatous polyp, ciliary body medulloepithelioma, pituitary blastoma, pineoblastoma, primary central nervous system sarcoma, embryonal tumor with multilayered rosettes-like cerebellar tumor, PPB-like peritoneal sarcoma, DICER1-associated presacral malignant teratoid neoplasm and other non-neoplastic associations. Each of these neoplasms is characterized by a second somatic mutation in DICER1. In this review, we have summarized the salient clinicopathologic aspects of these tumors whose histopathologic features have several overlapping morphologic attributes particularly the primitive mesenchyme often with rhabdomyoblastic and chondroid differentiation and an uncommitted spindle cell pattern. Several of these tumors have an initial cystic stage from which there is progression to a high grade, complex patterned neoplasm. These pathologic findings in the appropriate clinical setting should serve to alert the pathologist to the possibility of a DICER1-associated neoplasm and initiate appropriate testing on the neoplasm and to alert the clinician about the concern for a DICER1 mutation.

Dysregulation of Principal Cell miRNAs Facilitates Epigenetic Regulation of AQP2 and Results in Nephrogenic Diabetes Insipidus

BACKGROUND

MicroRNAs (miRNAs), formed by cleavage of pre-microRNA by the endoribonuclease Dicer, are critical modulators of cell function by post-transcriptionally regulating gene expression.

METHODS

Selective ablation of Dicer in AQP2-expressing cells (Dicer^AQP2Cre+ mice) was used to investigate the role of miRNAs in the kidney collecting duct of mice.

RESULTS

The mice had severe polyuria and nephrogenic diabetes insipidus, potentially due to greatly reduced AQP2 and AQP4 levels. Although epithelial sodium channel levels were decreased in cortex and increased in inner medulla, amiloride-sensitive sodium reabsorption was equivalent in Dicer^AQP2Cre+ mice and controls. Small-RNA sequencing and proteomic analysis revealed 31 and 178 significantly regulated miRNAs and proteins, respectively. Integrated bioinformatic analysis of the miRNAome and proteome suggested alterations in the epigenetic machinery and various transcription factors regulating AQP2 expression in Dicer^AQP2Cre+ mice. The expression profile and function of three miRNAs (miR-7688-5p, miR-8114, and miR-409-3p) whose predicted targets were involved in epigenetic control (Phf2, Kdm5c, and Kdm4a) or transcriptional regulation (GATA3, GATA2, and ELF3) of AQP2 were validated. Luciferase assays could not demonstrate direct interaction of AQP2 or the three potential transcription factors with miR-7688-5p, miR-8114, and miR-409-3p. However, transfection of respective miRNA mimics reduced AQP2 expression. Chromatin immunoprecipitation assays demonstrated decreased Phf2 and significantly increased Kdm5c interactions at the Aqp2 gene promoter in Dicer^AQP2Cre+ mice, resulting in decreased RNA Pol II association.

CONCLUSIONS

Novel evidence indicates miRNA-mediated epigenetic regulation of AQP2 expression.

The role of microRNAs in ovarian function and the transition toward novel therapeutic strategies in fertility preservation: from bench to future clinical application

BACKGROUND

New therapeutic approaches in oncology have converted cancer from a certain death sentence to a chronic disease. However, there are still challenges to be overcome regarding the off-target toxicity of many of these treatments. Oncological therapies can lead to future infertility in women. Given this negative impact on long-term quality of life, fertility preservation is highly recommended. While gamete and ovarian tissue cryopreservation are the usual methods offered, new pharmacological-based options aiming to reduce ovarian damage during oncological treatment are very attractive. In this vein, advances in the field of transcriptomics and epigenomics have brought small noncoding RNAs, called microRNAs (miRNAs), into the spotlight in oncology. MicroRNAs also play a key role in follicle development as regulators of follicular growth, atresia and steroidogenesis. They are also involved in DNA damage repair responses and they can themselves be modulated during chemotherapy. For these reasons, miRNAs may be an interesting target to develop new protective therapies during oncological treatment. This review summarizes the physiological role of miRNAs in reproduction. Considering recently developed strategies based on miRNA therapy in oncology, we highlight their potential interest as a target in fertility preservation and propose future strategies to make the transition from bench to clinic.

OBJECTIVE AND RATIONALE

How can miRNA therapeutic approaches be used to develop new adjuvant protective therapies to reduce the ovarian damage caused by cytotoxic oncological treatments?

SEARCH METHODS

A systematic search of English language literature using PubMed and Google Scholar databases was performed through to 2019 describing the role of miRNAs in the ovary and their use for diagnosis and targeted therapy in oncology. Personal data illustrate miRNA therapeutic strategies to target the gonads and reduce chemotherapy-induced follicular damage.

OUTCOMES

This review outlines the importance of miRNAs as gene regulators and emphasizes the fact that insights in oncology can inspire new adjuvant strategies in the field of onco-fertility. Recent improvements in nanotechnology offer the opportunity for drug development using next-generation miRNA-nanocarriers.

WIDER IMPLICATIONS

Although there are still some barriers regarding the immunogenicity and toxicity of these treatments and there is still room for improvement concerning the specific delivery of miRNAs into the ovaries, we believe that, in the future, miRNAs can be developed as powerful and non-invasive tools for fertility preservation.

Dicing the Disease with Dicer: The Implications of Dicer Ribonuclease in Human Pathologies

Gene expression dictates fundamental cellular processes and its de-regulation leads to pathological conditions. A key contributor to the fine-tuning of gene expression is Dicer, an RNA-binding protein (RBPs) that forms complexes and affects transcription by acting at the post-transcriptional level via the targeting of mRNAs by Dicer-produced small non-coding RNAs. This review aims to present the contribution of Dicer protein in a wide spectrum of human pathological conditions, including cancer, neurological, autoimmune, reproductive and cardiovascular diseases, as well as viral infections. Germline mutations of Dicer have been linked to Dicer1 syndrome, a rare genetic disorder that predisposes to the development of both benign and malignant tumors, but the exact correlation of Dicer protein expression within the different cancer types is unclear, and there are contradictions in the data. Downregulation of Dicer is related to Geographic atrophy (GA), a severe eye-disease that is a leading cause of blindness in industrialized countries, as well as to psychiatric and neurological diseases such as depression and Parkinson's disease, respectively. Both loss and upregulation of Dicer protein expression is implicated in severe autoimmune disorders, including psoriasis, ankylosing spondylitis, rheumatoid arthritis, multiple sclerosis and autoimmune thyroid diseases. Loss of Dicer contributes to cardiovascular diseases and causes defective germ cell differentiation and reproductive system abnormalities in both sexes. Dicer can also act as a strong antiviral with a crucial role in RNA-based antiviral immunity. In conclusion, Dicer is an essential enzyme for the maintenance of physiology due to its pivotal role in several cellular processes, and its loss or aberrant expression contributes to the development of severe human diseases. Further exploitation is required for the development of novel, more effective Dicer-based diagnostic and therapeutic strategies, with the goal of new clinical benefits and better quality of life for patients.

Increased rates of vesicoureteral reflux in mice from deletion of Dicer in the peri-Wolffian duct stroma

BACKGROUND

Vesicoureteral reflux (VUR), backflow of urine into the kidney, is associated with urinary tract infections and chronic kidney disease. Integrity of the vesicoureteral junction (VUJ), where reflux occurs, is determined largely by proper induction of the ureteric bud from the Wolffian duct. Induction is modulated by signals from the surrounding peri-Wolffian duct stroma. We evaluated whether miRNAs in the peri-Wolffian duct stroma are necessary for proper ureteric induction, VUJ formation, and suppression of VUR.

METHODS

We generated a mouse with loss of miRNAs in the peri-Wolffian duct stroma. We evaluated embryos for ureteric bud induction defects and expression of genes that regulate induction. We performed cystograms to assess for reflux and assessed VUJs in postnatal mice.

RESULTS

Mutant embryos had cranially displaced ureteric bud induction sites vs. controls. We observed no changes in expression of genes known to regulate induction. While mutants were early postnatal lethal, they had high rates of VUR vs. controls. Mutant VUJs that refluxed had low inserting ureters and shortened intravesicular tunnels vs. non-refluxing mice.

CONCLUSIONS

We found that miRNAs in the peri-Wolffian duct stroma are required for normal ureteric bud induction, VUJ formation, and prevention of VUR.

The Pathogenesis of Endometriosis: Molecular and Cell Biology Insights

The etiopathogenesis of endometriosis is a multifactorial process resulting in a heterogeneous disease. Considering that endometriosis etiology and pathogenesis are still far from being fully elucidated, the current review aims to offer a comprehensive summary of the available evidence. We performed a narrative review synthesizing the findings of the English literature retrieved from computerized databases from inception to June 2019, using the Medical Subject Headings (MeSH) unique ID term “Endometriosis” (ID:D004715) with “Etiology” (ID:Q000209), “Immunology” (ID:Q000276), “Genetics” (ID:D005823) and “Epigenesis, Genetic” (ID:D044127). Endometriosis may origin from Müllerian or non-Müllerian stem cells including those from the endometrial basal layer, Müllerian remnants, bone marrow, or the peritoneum. The innate ability of endometrial stem cells to regenerate cyclically seems to play a key role, as well as the dysregulated hormonal pathways. The presence of such cells in the peritoneal cavity and what leads to the development of endometriosis is a complex process with a large number of interconnected factors, potentially both inherited and acquired. Genetic predisposition is complex and related to the combined action of several genes with limited influence. The epigenetic mechanisms control many of the processes involved in the immunologic, immunohistochemical, histological, and biological aberrations that characterize the eutopic and ectopic endometrium in affected patients. However, what triggers such alterations is not clear and may be both genetically and epigenetically inherited, or it may be acquired by the particular combination of several elements such as the persistent peritoneal menstrual reflux as well as exogenous factors. The heterogeneity of endometriosis and the different contexts in which it develops suggest that a single etiopathogenetic model is not sufficient to explain its complex pathobiology.

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.

Sertoli-Leydig cell tumor of the ovary: Analysis of a single institution database and review of the literature

AIM

To evaluate the clinical characteristics and outcome of ovarian Sertoli-Leydig cell tumors (SLCTs) managed at a single institution.

METHODS

The hospital records of 17 patients with the diagnosis of ovarian SLCT between 1994 and 2018 were reviewed retrospectively.

RESULTS

The median age of the patients was 30 years (range, 18-67 years). All the patients had unilateral tumors. All of the 17 were stage 1 tumors. Two (11.8%) patients were stage 1C1 and two (11.8%) patients were stage 1C2. Thirteen (76.5%) patients were stage 1A. Three (17.6%) of the tumors were well differentiated, 11 (64.7%) were intermediately differentiated, 1 (5.9%) was poorly differentiated, and the degree of the differentiation was not identified for 2 (11.8%) patients. One showed retiform pattern and one had heterologous elements at the histopathologic evaluation. Among the 17 patients, we identified structural/vascular renal and ureteral anomalies in 3 (17.6%) patients. Eight patients underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy, seven underwent unilateral salpingo-oophorectomy or oophorectomy and two underwent cystectomy with or without additional surgical staging procedures. Four patients received adjuvant chemotherapy. All the 17 patients were alive and free of disease for 1-287 months after the diagnosis. Median follow-up time was 78 months. None of the patients recurred.

CONCLUSION

Sertoli-Leydig cell tumors are rare ovarian malignancies with low recurrence rates and have a favorable outcome compared to malignant epithelial tumors of the ovary. Main treatment is surgical resection and it is appropriate to prefer fertility sparing conservative surgeries for young patients.

Safe Nanocomposite-Mediated Efficient Delivery of MicroRNA Plasmids for Autosomal Dominant Polycystic Kidney Disease (ADPKD) Therapy

There is currently no cure for gene mutation-caused autosomal dominant polycystic kidney disease (ADPKD). Over half of patients with ADPKD eventually develop kidney failure, requiring dialysis or kidney transplantation. Current treatment modalities for ADPKD focus on reducing morbidity and mortality from renal and extrarenal complications of the disease. MicroRNA has been shown to be useful in treating ADPKD. This study combines anti-miRNA plasmids and iron oxide/alginate nanoparticles for conjugation with antikidney antibodies. These nanocomposites can specifically target renal tubular cells, providing a potential treatment for ADPKD. Magnetic resonance imaging and in vivo imaging system results show effective targeting of renal cells. Anti-miRNA plasmids released from the nanocomposites inhibit cell proliferation and cyst formation in the PKD cellular and animal models. The results suggest the novel combination of the anti-miRNA plasmids and nanomaterials provides potential clinical implications for ADPKD treatment.

Oxidative stress modulates the expression of apoptosis-associated microRNAs in bovine granulosa cells in vitro

Despite its essential role in ovulation, oxidative stress (OS) has been found to be cytotoxic to cells, while microRNAs (miRNAs) are known as a major regulator of genes involved in cellular defense against cytotoxicity. However, a functional link between OS and miRNA expression changes in granulosa cells (GCs) remains to be investigated. Here, we investigate the OS modulation of apoptosis-associated miRNAs and their biological relevance in bovine GCs. Following the evaluation of cell viability, accumulation of reactive oxygen species (ROS), cytotoxicity and mitochondrial activity, we used a ready-to-use miRNA PCR array to identify differentially regulated miRNAs. The results showed that exposure to 150 μM H₂O₂ for 4 h creates remarkable signs of OS in GCs characterized by more than 50% loss of cell viability, higher nuclear factor erythroid 2-related factor 2 (NRF2) nuclear translocation, significantly (p < 0.05) higher abundance of antioxidant genes, significantly (p < 0.001) higher accumulation of ROS, lower mitochondrial activity and a higher (p < 0.001) number of apoptotic nuclei compared to that of the control group. miRNA expression analysis revealed that a total of 69 miRNAs were differentially regulated in which 47 and 22 miRNAs were up- and downregulated, respectively, in stressed GCs. By applying the 2-fold and p < 0.05 criteria, we found 16 miRNAs were upregulated and 10 miRNAs were downregulated. Target prediction revealed that up- and downregulated miRNAs potentially targeted a total of 6210 and 3575 genes, respectively. Pathway analysis showed that upregulated miRNAs are targeting the genes involved mostly in cell survival, intracellular communication and homeostasis, cellular migration and growth control and disease pathways. Our results showed that OS modulates the expression of apoptosis-associated miRNAs that might have effects on cellular or molecular damages.

Structural renal abnormalities in the DICER1 syndrome: a family-based cohort study

BACKGROUND

The DICER1 syndrome is a tumor-predisposition disorder caused by germline pathogenic variation in DICER1 and is associated with cystic nephroma and other renal neoplasms. Dicer1 mouse and rare human DICER1 syndrome case reports describe structural kidney and collecting system anomalies. We investigated renal function and the frequency of structural abnormalities of the kidney and collecting system in individuals with germline loss-of-function variants in DICER1.

METHODS

In this family-based cohort study, prospectively ascertained germline DICER1-mutation carriers (DICER1-carriers) and unaffected family controls were evaluated at the National Institutes of Health Clinical Center with renal ultrasound and comprehensive laboratory testing. Two radiologists reviewed the imaging studies from all participants for structural abnormalities, cysts, and tumors.

RESULTS

Eighty-nine DICER1-carriers and 61 family controls were studied. Renal cysts were detected in 1/33 DICER1-carrier children without history of cystic nephroma. Similar proportions of adult DICER1-carriers (8/48; 17%) and controls (11/50; 22%) had ultrasound-detected renal cysts (P = 0.504). 8/89 (9%) DICER1-carriers harbored ultrasound-detected structural abnormalities of varying severity within the collecting system or kidney, nephrolithiasis, or nephrocalcinosis. None of the family controls (0/61) had similar findings on ultrasound (P = 0.02). No meaningful differences in renal laboratory values between DICER1-carriers and unaffected family controls were observed.

CONCLUSIONS

Our report is the first to systematically characterize renal function and anatomy in a large prospective cohort of DICER1-carriers and DICER1-negative family controls. DICER1-carriers may be at increased risk of structural anomalies of the kidney or collecting system. The role for DICER1 in renal morphogenesis merits additional investigation.

Modeling epigenetic modifications in renal development and disease with organoids and genome editing

Understanding epigenetic mechanisms is crucial to our comprehension of gene regulation in development and disease. In the past decades, different studies have shown the role of epigenetic modifications and modifiers in renal disease, especially during its progression towards chronic and end-stage renal disease. Thus, the identification of genetic variation associated with chronic kidney disease has resulted in better clinical management of patients. Despite the importance of these findings, the translation of genotype-phenotype data into gene-based medicine in chronic kidney disease populations still lacks faithful cellular or animal models that recapitulate the key aspects of the human kidney. The latest advances in the field of stem cells have shown that it is possible to emulate kidney development and function with organoids derived from human pluripotent stem cells. These have successfully recapitulated not only kidney differentiation, but also the specific phenotypical traits related to kidney function. The combination of this methodology with CRISPR/Cas9 genome editing has already helped researchers to model different genetic kidney disorders. Nowadays, CRISPR/Cas9-based approaches also allow epigenetic modifications, and thus represent an unprecedented tool for the screening of genetic variants, epigenetic modifications or even changes in chromatin structure that are altered in renal disease. In this Review, we discuss these technical advances in kidney modeling, and offer an overview of the role of epigenetic regulation in kidney development and disease.

Unraveling the Mechanistic Complexity of the Glomerulocystic Phenotype in Dicer Conditional KO Mice by 2D Gel Electrophoresis Coupled Mass Spectrometry

PURPOSE

Dicer, an RNase III type endonuclease, is a key enzyme involved in miRNA biogenesis. It has been shown that this enzyme is essential for several aspects of postnatal kidney functions and homeostasis. In this study, we have examined conditional knockout (cKO) mice for Dicer in Pax8 (Paired-box gene 8) expressing cells to investigate the kidney protein profile. This specific model develops a glomerulocystic phenotype coupled with urinary concentration impairment, proteinuria, and severe renal failure.

EXPERIMENTAL DESIGN

Proteomic analysis was performed on kidney tissue extracts from cKO and control (Ctr) mice by 2D Gel Electrophoresis coupled with mass spectrometry.

RESULTS

The analysis highlighted 120 protein spots differentially expressed in Dicer cKO tissue compared with control; some of these proteins were validated by Western blotting. Ingenuity Pathway Analysis led to the identification of some interesting networks; among them, the one having ERK as a central hub may explain, through the modulation of the expression of a number of identified protein targets, the metabolic and structural alterations occurring during kidney cyst development in Dicer cKO mouse model.

CONCLUSIONS AND CLINICAL RELEVANCE

Our results contribute to gain new insights into molecular mechanisms through which Dicer endonuclease controls kidney development and physiological functions.

New roles for Dicer in the nucleolus and its relevance to cancer

The nucleolus is a distinct compartment of the nucleus responsible for ribosome biogenesis. Mis-regulation of nucleolar functions and of the cellular translation machinery has been associated with disease, in particular with many types of cancer. Indeed, many tumor suppressors (p53, Rb, PTEN, PICT1, BRCA1) and proto-oncogenes (MYC, NPM) play a direct role in the nucleolus, and interact with the RNA polymerase I transcription machinery and the nucleolar stress response. We have identified Dicer and the RNA interference pathway as having an essential role in the nucleolus of quiescent Schizosaccharomyces pombe cells, distinct from pericentromeric silencing, by controlling RNA polymerase I release. We propose that this novel function is evolutionarily conserved and may contribute to the tumorigenic pre-disposition of DICER1 mutations in mammals.

Noncoding RNA and epigenetic gene regulation in renal diseases

Kidneys have a major role in normal physiology and metabolic homeostasis. Loss or impairment of kidney function is a common occurrence in several metabolic disorders, including hypertension and diabetes. Chronic kidney disease (CKD) affect nearly 10% of the population worldwide; ranks 18th in the list of causes of death; and contributes to a significant proportion of healthcare costs. The tissue repair and regenerative potential of kidneys are limited and they decline during aging. Recent studies have demonstrated a key role for epigenetic processes and players, such as DNA methylation, histone modifications, noncoding (nc)RNA, and so on, in both kidney development and disease. In this review, we highlight these recent findings with an emphasis on aberrant epigenetic changes that accompany renal diseases, key targets, and their therapeutic value.

A MicroRNA Cluster miR-23-24-27 Is Upregulated by Aldosterone in the Distal Kidney Nephron Where it Alters Sodium Transport

The epithelial sodium channel (ENaC) is expressed in the epithelial cells of the distal convoluted tubules, connecting tubules, and cortical collecting duct (CCD) in the kidney nephron. Under the regulation of the steroid hormone aldosterone, ENaC is a major determinant of sodium (Na⁺ ) and water balance. The ability of aldosterone to regulate microRNAs (miRs) in the kidney has recently been realized, but the role of miRs in Na⁺ regulation has not been well established. Here we demonstrate that expression of a miR cluster mmu-miR-23-24-27, is upregulated in the CCD by aldosterone stimulation both in vitro and in vivo. Increasing the expression of these miRs increased Na⁺ transport in the absence of aldosterone stimulation. Potential miR targets were evaluated and miR-27a/b was verified to bind to the 3'-untranslated region of intersectin-2, a multi-domain protein expressed in the distal kidney nephron and involved in the regulation of membrane trafficking. Expression of Itsn2 mRNA and protein was decreased after aldosterone stimulation. Depletion of Itsn2 expression, mimicking aldosterone regulation, increased ENaC-mediated Na⁺ transport, while Itsn2 overexpression reduced ENaC's function. These findings reinforce a role for miRs in aldosterone regulation of Na⁺ transport, and implicate miR-27 in aldosterone's action via a novel target. J. Cell. Physiol. 232: 1306-1317, 2017. © 2016 Wiley Periodicals, Inc.

The role of Dicer1 in the male reproductive tract

Dicer1 is an RNase III enzyme necessary for microRNA (miRNA) biogenesis, as it cleaves pre-miRNAs into mature miRNAs. miRNAs are important regulators of gene expression. In recent years, several miRNA-independent roles of Dicer1 have been identified. They include the production of endogenous small interfering RNAs, detoxifying retrotransposon-derived transcripts, and binding to new targets; messenger RNAs and long noncoding RNAs. Further, in this review, the functional significance of Dicer1 in the male reproductive tract is discussed. Conditional Dicer1 knock-out mouse models have demonstrated a requisite role for Dicer in male fertility. Deletion of Dicer1 from somatic or germ cells in the testis cause spermatogenic problems rendering male mice infertile. The lack of Dicer1 in the proximal epididymis causes dedifferentiation of the epithelium, with unbalanced sex steroid receptor expression, defects in epithelial lipid homeostasis, and subsequent male infertility. In addition, Dicer1 ablation from the prostate leads to increased apoptosis of the differentiated luminal cells, followed by epithelial hypotrophy of the ventral prostate. However, further studies are needed to clarify which functions of Dicer1 are responsible for the observed phenotypes in the male reproductive tract.

Mice lacking microRNAs in Pax8-expressing cells develop hypothyroidism and end-stage renal failure

BACKGROUND

Non-coding RNAs have gained increasing attention during the last decade. The first large group of non-coding RNAs to be characterized systematically starting at the beginning of the 21st century were small oligonucleotides--the so-called microRNAs (miRNAs). By now we have learnt that microRNAs are indispensable for most biological processes including organogenesis and maintenance of organ structure and function. The role of microRNAs has been studied extensively in the development of a number of organs, so far most studies focussed on e.g. the heart or the brain whilst the role of microRNAs in the development and maintenance of complex epithelial organs is less well understood. Furthermore most analyses regarding microRNA function in epithelial organs employed conditional knockout mouse models of the RNAse III Dicer to abrogate microRNA biogenesis. However, there is increasing evidence for Dicer to have multiple functions independent from microRNA maturation. Therefore Dicer independent models are needed to gain further insight into the complex biology of miRNA dependent processes.

RESULTS

Here we analyze the contribution of microRNA-dependent transcriptional control in Pax8-expressing epithelial cells. Pax8 is a transcription factor that is crucial to the development of epithelial organs. The miRNA machinery was disrupted by crossing conditional DiGeorge syndrome critical region 8 (Dgcr8) fl/fl mice to Pax8Cre mice. The Dgcr8/Drosha complex processes pri-miRNAs in the nucleus before they are exported as pre-miRNAs for further maturation by Dicer in the cytoplasm. Dgcr8 fl/fl; Pax8Cre+ knockout mice died prematurely, developed massive hypothyroidism and end stage renal disease due to a loss of miRNAs in Pax8 expressing tissue.

CONCLUSION

Pax8Cre-mediated conditional loss of DiGeorge syndrome critical region 8 (Dgcr8), an essential component of the nuclear machinery that is required for microRNA biogenesis, resulted in severe hypothyroidism, massively reduced body weight and ultimately led to renal failure and death of the animals. These data provide further insight into the importance of miRNAs in organ homeostasis using a Dicer independent model.

Targeted sequencing of 96 renal developmental microRNAs in 1213 individuals from 980 families with congenital anomalies of the kidney and urinary tract

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of chronic kidney diseases in children and young adults, accounting for ∼50% of cases. These anomalies represent maldevelopment of the genitourinary system and can be genetically explained in only 10-16% of cases by mutations or by copy number variations in protein coding sequences. Knock-out mouse models, lacking components of the microRNA (miRNA) processing machinery (i.e. Dicer, Drosha, Dgcr8), exhibit kidney malformations resembling human CAKUT.

METHODS

Given the Dicer-null mouse phenotype, which implicates a central role for miRNAs gene regulation during kidney development, we hypothesized that miRNAs expressed during kidney development may cause CAKUT in humans if mutated. To evaluate this possibility we carried out Next-Generation sequencing of 96 stem-loop regions of 73 renal developmental miRNA genes in 1248 individuals with non-syndromic CAKUT from 980 families.

RESULTS

We sequenced 96 stem-loop regions encoded by 73 miRNA genes that are expressed during kidney development in humans, mice and rats. Overall, we identified in 31/1213 individuals from 26 families with 17 different single nucleotide variants. Two variants did not segregate with the disease and hence were not causative. Thirteen variants were likely benign variants because they occurred in control populations and/or they affected nucleotides of weak evolutionary conservation. Two out of 1213 unrelated individuals had potentially pathogenic variants with unknown biologic relevance affecting miRNAs MIR19B1 and MIR99A.

CONCLUSIONS

Our results indicate that mutations affecting mature microRNAs in individuals with CAKUT are rare and thus most likely not a common cause of CAKUT in humans.

Epigenetic Regulation in Cystogenesis

Epigenetic regulation refers to heritable changes in gene expression that do not involve any alteration of the DNA sequence. DNA methylation, histone modification, and gene regulation by microRNAs are well-known epigenetic modulations that are closely associated with several cellular processes and diverse disease states, such as cancers, even under precancerous conditions. More recently, several studies have indicated that epigenetic changes may be associated with renal cystic diseases, including autosomal dominant polycystic kidney disease, and the restoration of altered epigenetic factors may become a therapeutic target of renal cystic disease and would be expected to have minimal side effects. This review focuses on recently reported findings on epigenetic and considers the potential of targeting epigenetic regulation as a novel therapeutic approach to control cystogenesis.

Non-coding RNA in Ovarian Development and Disease

The ovary's primary function is to produce the mature female gamete, the oocyte that, following fertilization, can develop into an embryo, implant within the uterus and ultimately allow the mother's genetic material to be passed along to subsequent generations. In addition to supporting the generation of the oocyte, the ovary and specific ephemeral tissues within it, follicles and corpora lutea, produce steroids that regulate all aspects of the reproductive system, including the hypothalamic/pituitary axis, the reproductive tract (uterus, oviduct, cervix), secondary sex characteristics all of which are also essential for pregnancy and subsequent nurturing of the offspring. To accomplish these critical roles, ovarian development and function are tightly regulated by a number of exogenous (hypothalamic/pituitary) and endogenous (intraovarian) hormones. Within ovarian cells, intricate signalling cascades and transcriptional and post-transcriptional gene regulatory networks respond to these hormonal influences to provide the exquisite control over all of the temporal and spatial events that must be synchronized to allow this organ to successfully complete its function. This book chapter will focus specifically on the role of non-coding RNAs, their identification and described functional roles within the ovary with respect to normal function and their possible involvement in diseases, which involve the ovary.

Pediatric cystic nephromas: distinctive features and frequent DICER1 mutations

Cystic nephromas (CNs) are uncommon benign renal neoplasms that present with a bimodal age distribution, affecting either infants/young children or adult females. Although differences between these age groups have been suggested, large studies of pediatric CN have not been conducted. As a result, the nomenclature and diagnostic criteria for these lesions remain controversial. In addition, the morphological overlap seen between CN and cystic partially differentiated nephroblastoma (CPDN) can result in diagnostic dilemmas. This study reviews the morphologic and radiographic features of 44 pediatric CN prospectively enrolled on a Children's Oncology Group protocol from 2007 to 2013. Although the typical multicystic architecture with thin septa described in adult CN was present in all of our pediatric cases, differences were also identified. We report distinctive features that add to the morphological spectrum of CN in children. Of the 44 cases, 16 had been previously analyzed and reported for DICER1 mutation, and either loss of function or missense mutations or both were identified in 15 of 16. In contrast, we analyzed 10 cases of adult CN, and all were negative for DICER1 mutations; similarly, 6 CPDNs previously analyzed and reported were negative for DICER1 mutations. Therefore, the clinical, morphological, and genetic differences between pediatric and adult CN, as well as between CN and CPDN, suggest that these 3 lesions represent distinct entities.

MicroRNA in Ovarian Biology and Disease

MicroRNAs (miRNAs) are posttranscriptional gene regulatory molecules that show regulated expression within ovarian tissue. Most research investigating miRNAs in the ovary has relied exclusively on in vitro analyses. In this review, we highlight those few studies in which investigators have illustrated an in vivo effect of miRNAs on ovarian function. We also provide a synopsis of how these small noncoding RNAs can impact ovarian disease. miRNAs have great potential as novel diagnostic biomarkers for the detection of ovarian disease and in the assisted reproductive technologies (ART) for selection of healthy viable oocytes and embryos.

Loss of Dgcr8-mediated microRNA expression in the kidney results in hydronephrosis and renal malformation

Background

Small non-coding RNA molecules (miRNAs) play a pivotal role in regulating gene expression in development. miRNAs regulate key processes at the cellular level and thereby influence organismal and tissue development including kidney morphogenesis. A miRNA molecule is initially synthesized as a longer hairneedle-shaped RNA transcript and then processed through an enzymatic complex that contains the RNA-processing enzyme Drosha and its essential interactor Dgcr8. Resulting pre-miRNAs are then cleaved by Dicer. Recent data showed that loss of Dicer resulted in severe developmental kidney phenotypes. However, as Dicer has multiple miRNA-independent functions, it was not entirely clear whether the observed renal phenotypes could be exclusively attributed to a lack of miRNA expression.

Methods

We analyzed the role of miRNAs in kidney development by conditional gene deletion of Dgcr8 in the developing kidney using a transgenic mouse line that expresses Cre recombinase in the distal nephron and derivatives of the ureteric bud in kidney development.

Results

Animals with a gene deletion of Dgcr8 in these tissues developed severe hydronephrosis, kidney cysts, progressive renal failure and premature death within the first two months after birth, a phenotype strongly resembling Dicer deletion.

Conclusions

Here we show that conditional gene deletion of the essential miRNA-processing enzyme Dgcr8 in the developing renal tubular system results in severe developmental defects and kidney failure. These data confirm earlier findings obtained in Dicer knock-out animals and clearly illustrate the essential role of miRNAs in kidney development. The data suggests that miRNA dysregulation may play an important, yet ill-defined role in the pathogenesis of inborn defects of the genitourinary system and indicate that miRNA defects may be causative in the development of human disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0053-1) contains supplementary material, which is available to authorized users.

MicroRNAs in the pathogenesis of cystic kidney disease

PURPOSE OF REVIEW

Cystic kidney diseases are common renal disorders characterized by the formation of fluid-filled epithelial cysts in the kidneys. The progressive growth and expansion of the renal cysts replace existing renal tissue within the renal parenchyma, leading to reduced renal function. While several genes have been identified in association with inherited causes of cystic kidney disease, the molecular mechanisms that regulate these genes in the context of post-transcriptional regulation are still poorly understood. There is increasing evidence that microRNA (miRNA) dysregulation is associated with the pathogenesis of cystic kidney disease.

RECENT FINDINGS

In this review, recent studies that implicate dysregulation of miRNA expression in cystogenesis will be discussed. The relationship of specific miRNAs, such as the miR-17∼92 cluster and cystic kidney disease, miR-92a and von Hippel-Lindau syndrome, and alterations in LIN28-LET7 expression in Wilms tumor will be explored.

SUMMARY

At present, there are no specific treatments available for patients with cystic kidney disease. Understanding and identifying specific miRNAs involved in the pathogenesis of these disorders may have the potential to lead to the development of novel therapies and biomarkers.

Selective dicer suppression in the kidney alters GSK3β/β-catenin pathways promoting a glomerulocystic disease

Dicer is a crucial enzyme for the maturation of miRNAs. Mutations in the Dicer gene are highly associated with Pleuro Pulmonary Blastoma-Family Dysplasia Syndrome (PPB-FDS, OMIM 601200), recently proposed to be renamed Dicer syndrome. Aside from the pulmonary phenotype (blastoma), renal nephroma and thyroid goiter are frequently part of Dicer syndrome. To investigate the renal phenotype, conditional knockout (cKO) mice for Dicer in Pax8 expressing cells were generated. Dicer cKO mice progressively develop a glomerulocystic phenotype coupled with urinary concentration impairment, proteinuria and severe renal failure. Higher cellular turnover of the parietal cells of Bowman's capsule precedes the development of the cysts and the primary cilium progressively disappears with cyst-enlargement. Upregulation of GSK3β precedes the development of the glomerulocystic phenotype. Downregulation of β-catenin in the renal cortex and its cytosolic removal in the cells lining the cysts may be associated with observed accumulation of GSK3β. Alterations of β-catenin regulating pathways could promote cystic degeneration as in other models. Thus, miRNAs are fundamental in preserving renal morphology and function. Alteration of the GSK3β/β-catenin pathway could be a crucial mechanism linking miRNA dysregulation and the development of a glomerulocystic disease.

The ureteric bud epithelium: morphogenesis and roles in metanephric kidney patterning

The mammalian metanephric kidney is composed of two epithelial components, the collecting duct system and the nephron epithelium, that differentiate from two different tissues -the ureteric bud epithelium and the nephron progenitors, respectively-of intermediate mesoderm origin. The collecting duct system is generated through reiterative ureteric bud branching morphogenesis, whereas the nephron epithelium is formed in a process termed nephrogenesis, which is initiated with the mesenchymal-epithelial transition of the nephron progenitors. Ureteric bud branching morphogenesis is regulated by nephron progenitors, and in return, the ureteric bud epithelium regulates nephrogenesis. The metanephric kidney is physiologically divided along the corticomedullary axis into subcompartments that are enriched with specific segments of these two epithelial structures. Here, we provide an overview of the major molecular and cellular processes underlying the morphogenesis and patterning of the ureteric bud epithelium and its roles in the cortico-medullary patterning of the metanephric kidney.

Understanding the role of maternal diet on kidney development; an opportunity to improve cardiovascular and renal health for future generations

The leading causes of mortality and morbidity worldwide are cardiovascular disease (high blood pressure, high cholesterol and renal disease), cancer and diabetes. It is increasingly obvious that the development of these diseases encompasses complex interactions between adult lifestyle and genetic predisposition. Maternal malnutrition can influence the fetal and early life environment and pose a risk factor for the future development of adult diseases, most likely due to impaired organogenesis in the developing offspring. This then predisposes these offspring to cardiovascular disease and renal dysfunction in adulthood. Studies in experimental animals have further illustrated the significant impact maternal diet has on offspring health. Many studies report changes in kidney structure (a reduction in the number of nephrons in the kidney) in offspring of protein-deprived dams. Although the early studies suggested that increased blood pressure was also present in offspring of protein-restricted dams, this is not a universal finding and requires clarification. Importantly, to date, the literature offers little to no understanding of when in development these changes in kidney development occur, nor are the cellular and molecular mechanisms that drive these changes well characterised. Moreover, the mechanisms linking maternal nutrition and a suboptimal renal phenotype in offspring are yet to be discerned—one potential mechanism involves epigenetics. This review will focus on recent information on potential mechanisms by which maternal nutrition (focusing on malnutrition due to protein restriction, micronutrient restriction and excessive fat intake) influences kidney development and thereby function in later life.

Cell- and developmental stage-specific Dicer1 ablation in the lung epithelium models cystic pleuropulmonary blastoma

Inherited syndromes provide unique opportunities to identify key regulatory mechanisms governing human disease. We previously identified germline loss-of-function DICER1 mutations in a human syndrome defined by the childhood lung neoplasm pleuropulmonary blastoma (PPB), which arises during lung development. DICER1 regulates many biological processes critical in development and disease pathogenesis. Significant challenges in defining the role of DICER1 in human disease are identifying cause-effect relationships and generating manipulatable systems that model the complexity of organ development and disease pathogenesis. Here we report the generation of a murine model for PPB and demonstrate that precise temporal and cell type-specific Dicer1 ablation is necessary and sufficient for the development of cystic lungs that histologically and phenotypically model PPB. Dicer1 ablation in the distal airway epithelium during early stages of lung development resulted in a cystic lung phenotype indistinguishable from PPB, whereas DICER1 function was not required for development of the proximal airway epithelium or during later stages of organogenesis. Mechanistic studies demonstrate that Dicer1 loss results in epithelial cell death, followed by cystic airway dilatation accompanied by epithelial and mesenchymal proliferation. These studies define precise temporal and epithelial cell type-specific DICER1 functions in the developing lung and demonstrate that loss of these DICER1 functions is sufficient for the development of cystic PPB. These results also provide evidence that PPB arise through a novel mechanism of non-cell-autonomous tumour initiation, in which the genetic abnormality initiating the neoplasm does not occur in the cells that ultimately transform, but rather occurs in a benign-appearing epithelial cell component that predisposes underlying mesenchymal cells to malignant transformation.

microRNA in Human Reproduction

microRNAs constitute a large family of approximately 21-nucleotide-long, noncoding RNAs. They emerged more than 20 years ago as key posttranscriptional regulators of gene expression. The regulatory role of these small RNA molecules has recently begun to be explored in the human reproductive system. microRNAs have been shown to play an important role in control of reproductive functions, especially in the processes of oocyte maturation, folliculogenesis, corpus luteum function, implantation, and early embryonic development. Knockout of Dicer, the cytoplasmic enzyme that cleaves the pre-miRNA to its mature form, results in postimplantation embryonic lethality in several animal models, attributing to these small RNA vital functions in reproduction and development. Another intriguing characteristic of microRNAs is their presence in body fluids in a remarkably stable form that is protected from endogenous RNase activity. In this chapter we will describe the current knowledge on microRNAs, specifically relating to human gonadal cells. We will focus on their role in the ovarian physiologic process and ovulation dysfunction, regulation of spermatogenesis and male fertility, and putative involvement in human normal and aberrant trophoblast differentiation and invasion through the process of placentation.

microRNA-dependent temporal gene expression in the ureteric bud epithelium during mammalian kidney development

BACKGROUND

Our previous study on mouse mutants with the ureteric bud (UB) epithelium-specific Dicer deletion (Dicer UB mutants) demonstrated the significance of UB epithelium-derived miRNAs in UB development.

RESULTS

Our whole-genome transcriptional profiling showed that the Dicer mutant UB epithelium abnormally retained transcriptional features of the early UB epithelium and failed to express many genes associated with collecting duct differentiation. Furthermore, we identified a temporal expression pattern of early UB genes during UB epithelium development in which gene expression was detected at early developmental stages and became undetectable by embryonic day 14.5. In contrast, expression of early UB genes persisted at later stages in the Dicer mutant UB epithelium and increased at early stages. Our bioinformatic analysis of the abnormally persistently expressed early genes in the Dicer mutant UB epithelium showed significant enrichment of the let-7 family miRNA targets. We further identified a temporal expression pattern of let-7 miRNAs in the UB epithelium that is anti-parallel to that of some early UB genes during kidney development.

CONCLUSIONS

We propose a model in which the let-7 family miRNAs silence the expression of a subset of early genes in the UB epithelium at later developmental stages to promote collecting duct differentiation. Developmental Dynamics 244:444-456, 2015. © 2014 Wiley Periodicals, Inc.

Research resources: comparative microRNA profiles in human corona radiata cells and cumulus oophorus cells detected by next-generation small RNA sequencing

During folliculogenesis, cumulus cells surrounding the oocyte differentiate into corona radiata cells (CRCs) and cumulus oophorus cells (COCs), which are involved in gonadal steroidogenesis and the development of germ cells. Several studies suggested that microRNAs (miRNAs) play an important regulatory role at the post-transcriptional level in cumulus cells. However, comparative miRNA profiles and associated processes in human CRCs and COCs have not been reported before. In this study, miRNA profiles were obtained from CRCs and COCs using next generation sequencing in women undergoing controlled ovarian stimulation for IVF. A total of 785 and 799 annotated miRNAs were identified in CRCs and COCs, while high expression levels of six novel miRNAs were detected both in CRCs and in COCs. In addition, different expression patterns in CRCs and COCs were detected in 72 annotated miRNAs. To confirm the miRNA profile in COCs and CRCs, quantitative real-time PCR was used to validate the expression of annotated miRNAs, differentially expressed miRNAs, and novel miRNAs. The miRNAs in the let-7 family were found to be involved in the regulation of a broad range of biological processes in both cumulus cell populations, which was accompanied by a large amount of miRNA editing. Bioinformatics analysis showed that amino acid and energy metabolism were targeted significantly by miRNAs that were differentially expressed between CRCs and COCs. Our work extends the current knowledge of the regulatory role of miRNAs and their targeted pathways in folliculogenesis, and provides novel candidates for molecular biomarkers in the research of female infertility.

DICER1 mutations in childhood cystic nephroma and its relationship to DICER1-renal sarcoma

The pathogenesis of cystic nephroma of the kidney has interested pathologists for over 50 years. Emerging from its initial designation as a type of unilateral multilocular cyst, cystic nephroma has been considered as either a developmental abnormality or a neoplasm or both. Many have viewed cystic nephroma as the benign end of the pathologic spectrum with cystic partially differentiated nephroblastoma and Wilms tumor, whereas others have considered it a mixed epithelial and stromal tumor. We hypothesize that cystic nephroma, like the pleuropulmonary blastoma in the lung, represents a spectrum of abnormal renal organogenesis with risk for malignant transformation. Here we studied DICER1 mutations in a cohort of 20 cystic nephromas and 6 cystic partially differentiated nephroblastomas, selected independently of a familial association with pleuropulmonary blastoma and describe four cases of sarcoma arising in cystic nephroma, which have a similarity to the solid areas of type II or III pleuropulmonary blastoma. The genetic analyses presented here confirm that DICER1 mutations are the major genetic event in the development of cystic nephroma. Further, cystic nephroma and pleuropulmonary blastoma have similar DICER1 loss of function and 'hotspot' missense mutation rates, which involve specific amino acids in the RNase IIIb domain. We propose an alternative pathway with the genetic pathogenesis of cystic nephroma and DICER1-renal sarcoma paralleling that of type I to type II/III malignant progression of pleuropulmonary blastoma.

Cell-free nucleic acids as non-invasive biomarkers of gynecological cancers, ovarian, endometrial and obstetric disorders and fetal aneuploidy

BACKGROUND

Proper folliculogenesis is fundamental to obtain a competent oocyte that, once fertilized, can support the acquisition of embryo developmental competence and pregnancy. MicroRNAs (miRNAs) are crucial regulators of folliculogenesis, which are expressed in the cumulus-oocyte complex and in granulosa cells and some can also be found in the bloodstream. These circulating miRNAs are intensively studied and used as diagnostic/prognostic markers of many diseases, including gynecological and pregnancy disorders. In addition, serum contains small amounts of cell-free DNA (cfDNA), presumably resulting from the release of genetic material from apoptotic/necrotic cells. The quantification of nucleic acids in serum samples could be used as a diagnostic tool for female infertility.

METHODS

An overview of the published literature on miRNAs, and particularly on the use of circulating miRNAs and cfDNA as non-invasive biomarkers of gynecological diseases, was performed (up to January 2014).

RESULTS

In the past decade, cell-free nucleic acids have been studied for potential use as biomarkers in many diseases, particularly in gynecological cancers, ovarian and endometrial disorders, as well as in pregnancy-related pathologies and fetal aneuploidy. The data strongly suggest that the concentration of cell-free nucleic acids in serum from IVF patients or in embryo culture medium could be related to the ovarian hormone status and embryo quality, respectively, and be used as a non-invasive biomarker of IVF outcome.

CONCLUSIONS

The profiling of circulating nucleic acids, such as miRNAs and cfDNA, opens new perspectives for the diagnosis/prognosis of ovarian disorders and for the prediction of IVF outcomes, namely (embryo quality and pregnancy).

miRNAs in mammalian ureteric bud development

The collecting duct network and the urothelium of the ureter of the metanephric kidney are derived from the ureteric bud epithelium, initially an outgrowth from the caudal end of the Wolffian duct at the onset of the metanephric kidney development. The tips of the ureteric bud epithelium undergo reiterative branching morphogenesis, which generates more tips and trunks, whereas the ureteric trunks grow and differentiate into principal cells and intercalated cells of the collecting ducts that regulate body water and acid-base homeostasis. microRNAs (miRNAs) are a family of small non-coding RNAs that regulate a diversity of biological processes including organogenesis, mostly by negatively regulating their target gene expression. In this review, I will summarize the current knowledge on the critical roles of miRNAs expressed in the ureteric bud epithelium in ureteric bud morphogenesis and differentiation, including ureteric bud branching morphogenesis, collecting duct terminal differentiation, cystogenesis of the collecting ducts, and ureter development.

The regulation and function of microRNAs in kidney diseases

MicroRNAs (miRNA) are endogenous short noncoding RNAs, which regulate virtually all major cellular processes by inhibiting target gene expression. In kidneys, miRNAs have been implicated in renal development, homeostasis, and physiological functions. In addition, miRNAs play important roles in the pathogenesis of various renal diseases, including renal carcinoma, diabetic nephropathy, acute kidney injury, hypertensive nephropathy, polycystic kidney disease, and others. Furthermore, miRNAs may have great values as biomarkers in different kidney diseases.

microRNA biomarkers in cystic diseases

microRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by targeting the 3’-untranslated region of multiple target genes. Pathogenesis results from defects in several gene sets; therefore, disease progression could be prevented using miRNAs targeting multiple genes. Moreover, recent studies suggest that miRNAs reflect the stage of the specific disease, such as carcinogenesis. Cystic diseases, including polycystic kidney disease, polycystic liver disease, pancreatic cystic disease, and ovarian cystic disease, have common processes of cyst formation in the specific organ. Specifically, epithelial cells initiate abnormal cell proliferation and apoptosis as a result of alterations to key genes. Cysts are caused by fluid accumulation in the lumen. However, the molecular mechanisms underlying cyst formation and progression remain unclear. This review aims to introduce the key miRNAs related to cyst formation, and we suggest that miRNAs could be useful biomarkers and potential therapeutic targets in several cystic diseases. [BMB Reports 2013; 46(7):338-345]

MiR-181b targets Six2 and inhibits the proliferation of metanephric mesenchymal cells in vitro

MicroRNAs (miRNAs) are small non-coding RNAs that down-regulate gene expression by binding to target mRNA for cleavage or translational repression, and play important regulatory roles in renal development. Despite increasing genes have been predicted to be miRNA targets by bioinformatic analysis during kidney development, few of them have been verified by experiment. The objective of our study is to identify the miRNAs targeting Six2, a critical transcription factor that maintains the mesenchymal progenitor pool via self-renewal (proliferation) during renal development. We initially analyzed the 3'UTR of Six2 and found 37 binding sites targeted by 50 putative miRNAs in the 3'UTR of Six2. Among the 50 miRNAs, miR-181b is the miRNAs predicted by the three used websites. In our study, the results of luciferase reporter assay, realtime-PCR and Western blot demonstrated that miR-181b directly targeted on the 3'UTR of Six2 and down-regulate the expression of Six2 at mRNA and protein levels. Furthermore, EdU proliferation assay along with the Six2 rescue strategy showed that miR-181b suppresses the proliferation of metanephric mesenchymal by targeting Six2 in part. In our research, we concluded that by targeting the transcription factor gene Six2, miR-181b inhibits the proliferation of metanephric mesenchymal cells in vitro and might play an important role in the formation of nephrons.

A dosage-dependent pleiotropic role of Dicer in prostate cancer growth and metastasis

Dicer is as an RNase III enzyme essential for the maturation of the majority of microRNAs. Recent studies have revealed down-regulation or hemizygous loss of Dicer in many tumor models and demonstrated that suppressing Dicer activity enhances tumorigenic activities of lung and breast cancer cells, which support Dicer as a haploinsufficient tumor suppressor in these cancer models. Surprisingly, we found that knocking down Dicer expression suppresses the growth and tumorigenic capacity of human prostate cancer cell lines, but enhances migratory capacities of some prostate cancer cell lines. Dicer is up-regulated in human prostate cancer specimens, but lower Dicer expression portends a shorter time to recurrence. Complete ablation of Dicer activity in a Pten null mouse model for prostate cancer significantly halts tumor growth and progression, demonstrating that microRNAs play a critical role in maintaining cancer cell fitness. In comparison, hemizygous loss of Dicer in the same model also reduces primary tumor burden, but induces a more locally invasive phenotype and causes seminal vesicle obstruction at high penetrance. Disrupting Dicer activity leads to an increase in apoptosis and senescence in these models, presumably through up-regulation of P16/INK4a and P27/Kip1. Collectively, these results highlight a pleotropic role of Dicer in tumorigenesis that is not only dosage-dependent but also tissue context-dependent.

An emerging role for microRNA in the regulation of endothelin-1

Endothelin-1 (ET-1) is a peptide signaling molecule serving diverse functions in many different tissues such as the vasculature and the kidney. The primary mechanism thought to control ET-1 bioavailability is the rate of transcription from the ET-1 gene (EDN1), but recent research suggests that EDN1 expression is attenuated by microRNA (miRNA)—mediated regulation. The action of specific miRNAs on EDN1 mRNA appears to vary greatly in a tissue specific manner. This review provides a summary of our current understanding of miRNA-EDN1 interaction.

MicroRNAs in renal development

The discovery of microRNAs (miRNAs) as novel regulators of gene expression has led to a marked change in how gene regulation is viewed, with important implications for development and disease. MiRNAs are endogenous, small, noncoding RNAs that largely repress their target mRNAs post-transcriptionally. The regulation of gene expression by miRNAs represents an evolutionarily conserved mechanism that is broadly applicable to most biological processes. Recent studies have begun to define the role of miRNAs in different cell lineages during kidney development, and to implicate specific miRNAs in developmental and pathophysiological processes in the kidney. This review will focus on novel insights into the role(s) of miRNAs in kidney development, and discuss the implications for pediatric renal disease.

Conditional loss of kidney microRNAs results in congenital anomalies of the kidney and urinary tract (CAKUT)

MicroRNAs have emerged as essential regulators of gene expression and may play important roles in a variety of human disorders. To understand the role of microRNA-mediated gene regulation in the kidney, we deleted the microRNA-processing enzyme Dicer in developing renal tubules and parts of the ureteric bud in mice. Genetic deletion of Dicer resulted in renal failure and death of the animals at 4-6 weeks of age. Interestingly, the kidneys of microRNA-deficient animals were small due to a reduced number of nephrons and showed massive hydronephrosis due to ureteropelvic junction obstruction. This phenotype is reminiscent of congenital anomalies of the kidney and urinary tract (CAKUT), an important group of human disorders characterized by a combination of renal hypoplasia with congenital abnormalities of the urinary tract. We used metanephric kidney cultures to examine the developmental defects underlying these pathologies. Dicer knockout kidneys showed a significant reduction of tubular branching explaining renal hypoplasia. Moreover, the ureters of these kidneys showed an altered morphology and impaired motility. These functional changes went along with altered expression of smooth muscle actin implying a defect in the differentiation of ureteric smooth muscle cells. In addition, we show the polycystic kidney disease gene Pkd1 to be a target of miR-20 implying that this interaction may contribute to the molecular basis for the cystogenesis in our model. In conclusion, these data demonstrate an essential role for microRNA-dependent gene regulation in mammalian kidney development and suggest that deregulation of microRNAs may underlie CAKUT, the most important group of renal disorders in humans.

MicroRNAs in kidney disease: an emerging understanding

MicroRNAs (miRNAs) are short noncoding RNA molecules that function by negatively regulating the expression of their target genes in a tightly controlled manner. Accumulating evidence, based in part on effects seen after miRNA overexpression and/or knockdown, points to the critical involvement of miRNAs in kidney function in health and disease. In this review, we provide a quick overview of the biogenesis of miRNAs and their potential involvement in kidney development and normal function. We also discuss the current literature that has begun to uncover the role of miRNAs in the pathogenesis of kidney diseases, including diabetic nephropathy, hypertension, glomerulonephritis, and cancer. As such, miRNAs have potential utility in the clinical realm as disease biomarkers. Moreover, miRNAs represent an attractive therapeutic target for a number of kidney diseases. We close by discussing a number of potential challenges that face the field of miRNA research and clinical use.

Network analysis of a Pkd1-mouse model of autosomal dominant polycystic kidney disease identifies HNF4α as a disease modifier

Autosomal Dominant Polycystic Kidney Disease (ADPKD; MIM ID's 173900, 601313, 613095) leads to end-stage kidney disease, caused by mutations in PKD1 or PKD2. Inactivation of Pkd1 before or after P13 in mice results in distinct early- or late-onset disease. Using a mouse model of ADPKD carrying floxed Pkd1 alleles and an inducible Cre recombinase, we intensively analyzed the relationship between renal maturation and cyst formation by applying transcriptomics and metabolomics to follow disease progression in a large number of animals induced before P10. Weighted gene co-expression network analysis suggests that Pkd1-cystogenesis does not cause developmental arrest and occurs in the context of gene networks similar to those that regulate/maintain normal kidney morphology/function. Knowledge-based Ingenuity Pathway Analysis (IPA) software identifies HNF4α as a likely network node. These results are further supported by a meta-analysis of 1,114 published gene expression arrays in Pkd1 wild-type tissues. These analyses also predict that metabolic pathways are key elements in postnatal kidney maturation and early steps of cyst formation. Consistent with these findings, urinary metabolomic studies show that Pkd1 cystic mutants have a distinct profile of excreted metabolites, with pathway analysis suggesting altered activity in several metabolic pathways. To evaluate their role in disease, metabolic networks were perturbed by inactivating Hnf4α and Pkd1. The Pkd1/Hnf4α double mutants have significantly more cystic kidneys, thus indicating that metabolic pathways could play a role in Pkd1-cystogenesis.

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most common genetic cause of polycystic kidney disease and is responsible for 4.6% of the end-stage renal disease (ESRD) cases in the United States. It is most often caused by mutation in the PKD1 gene. To understand this disease, we made a mouse model in which we could delete the Pkd1 gene and study the animal as its kidney becomes cystic. Using this model, we had previously found that the maturation status of the animal determines whether cysts form within days or within months, and we had narrowed down this switch to a two-day interval. In the current study, we used the rapid cyst-forming model to analyze the expression pattern of thousands of genes in mutant and control kidneys, and metabolites excreted in the urine. Our results identify a number of genes that may be involved in cyst formation and suggest that metabolic changes may play a role in ADPKD and could alter disease progression. These analyses also predict that metabolic pathways are key elements in normal postnatal kidney maturation.

Developmental programming of hypertension and kidney disease

A growing body of evidence supports the concept that changes in the intrauterine milieu during "sensitive" periods of embryonic development or in infant diet after birth affect the developing individual, resulting in general health alterations later in life. This phenomenon is referred to as "developmental programming" or "developmental origins of health and disease." The risk of developing late-onset diseases such as hypertension, chronic kidney disease (CKD), obesity or type 2 diabetes is increased in infants born prematurely at <37 weeks of gestation or in low birth weight (LBW) infants weighing <2,500 g at birth. Both genetic and environmental events contribute to the programming of subsequent risks of CKD and hypertension in premature or LBW individuals. A number of observations suggest that susceptibility to subsequent CKD and hypertension in premature or LBW infants is mediated, at least in part, by reduced nephron endowment. The major factors influencing in utero environment that are associated with a low final nephron number include uteroplacental insufficiency, maternal low-protein diet, hyperglycemia, vitamin A deficiency, exposure to or interruption of endogenous glucocorticoids, and ethanol exposure. This paper discusses the effect of premature birth, LBW, intrauterine milieu, and infant feeding on the development of hypertension and renal disease in later life as well as examines the role of the kidney in developmental programming of hypertension and CKD.