Prenatal genetic considerations of congenital anomalies of the kidney and urinary tract (CAKUT)

Matching clinical and genetic data in pediatric patients at risk of developing cystic kidney disease

BACKGROUND

Cystic kidney disease is a heterogeneous group of hereditary and non-hereditary pathologic conditions, associated with the development of renal cysts. These conditions may be present both in children and adults. Cysts can even be observed already during the prenatal age, and pediatric patients with cysts need to be clinically monitored. An early clinical and genetic diagnosis is therefore mandatory for optimal patient management. The aim of this study was to perform genetic analyses in patients with echographic evidence of kidney cysts to provide an early molecular diagnosis.

METHODS

A cohort of 70 pediatric patients was enrolled and clinically studied at the time of first recruitment and at follow-up. Genetic testing by clinical exome sequencing was performed and a panel of genes responsible for "cystic kidneys" was analyzed to identify causative variants. Sanger validation and segregation studies were exploited for the final classification of the variants and accurate genetic counseling.

RESULTS

Data showed that 53/70 of pediatric patients referred with a clinical suspicion of cystic kidney disease presented a causative genetic variant. In a significant proportion of the cohort (24/70), evidence of hyper-echogenic/cystic kidneys was already present in the prenatal period, even in the absence of a positive family history.

CONCLUSIONS

This study suggests that cystic kidney disease may develop since the very early stages of life and that screening programs based on ultrasound scans and genetic testing play a critical role in diagnosis, allowing for better clinical management and tailored genetic counseling to the family.

Genetics of anomalies of the kidney and urinary tract with congenital heart disease: A review

Congenital anomalies of the kidney and urinary tract (CAKUT) and congenital heart disease (CHD) are the most common congenital defects and constitute a major cause of morbidity in children. Anomalies of both systems may be isolated or associated with congenital anomalies of other organ systems. Various reports support the co-occurrence of CAKUT and CHD, although the prevalence can vary. Cardiovascular anomalies occur in 11.2% to 34% of patients with CAKUT, and CAKUT occur in 5.3% to 35.8% of those with CHD. The co-occurrence of genetic factors in both CAKUT and CHD would raise common etiologies including genetics, genetic-environmental interactions, or shared molecular mechanisms and pathways such as NODAL, NOTCH, BMP, WNT, and VEGF. Studies in animal models and humans have indicated a genetic etiology for CHD and CAKUT with hundreds of genes recognized and thousands of entries, found in a catalog of human genetic disorders. There are over 80 CAKUT genes and over 100 CHD genes available for clinical testing. For example, the HNFIB gene accounts for 5% to 31% of reported cases of CAKUT. In view of the association between CAKUT and CHD, a thorough cardiac examination should be performed in patients with CAKUT, and a similar evaluation for CAKUT in the presence of CHD. This will allow early diagnosis and therapeutic intervention to improve the long- term outcome of patients affected, and test for at-risk family members. We present here evidence for an association of anomalies involving the two organ systems, and discuss possible etiologies of targeted genes, their functions, biological processes and interactions on embryogenesis.

Practical Approach to Congenital Anomalies of the Kidneys: Focus on Anomalies With Insufficient or Abnormal Nephron Development: Renal Dysplasia, Renal Hypoplasia, and Renal Tubular Dysgenesis

Congenital anomalies of the kidney and urinary tract (CAKUT) accounts for up to 30% of antenatal congenital anomalies and is the main cause of kidney failure in children worldwide. This review focuses on practical approaches to CAKUT, particularly those with insufficient or abnormal nephron development, such as renal dysplasia, renal hypoplasia, and renal tubular dysgenesis. The review provides insights into the histological features, pathogenesis, mechanisms, etiologies, antenatal and postnatal presentation, management, and prognosis of these anomalies. Differential diagnoses are discussed as several syndromes may include CAKUT as a phenotypic component and renal dysplasia may occur in some ciliopathies, tumor predisposition syndromes, and inborn errors of metabolism. Diagnosis and genetic counseling for CAKUT are challenging, due to the extensive variability in presentation, genetic and phenotypic heterogeneity, and difficulties to assess postnatal lung and renal function on prenatal imaging. The review highlights the importance of perinatal autopsy and pathological findings in surgical specimens to establish the diagnosis and prognosis of CAKUT. The indications and the type of genetic testing are discussed. The aim is to provide essential insights into the practical approaches, diagnostic processes, and genetic considerations offering valuable guidance for pediatric and perinatal pathologists.

Congenital anomalies of the kidney and urinary tract

Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) refer to a range of conditions that affect the kidney and urinary tract. These anomalies can be severe, such as kidney agenesis, or milder, such as vesicoureteral reflux. CAKUT affects over 1% of live births and accounts for 40-50% of cases of chronic kidney failure in children. The pathogenesis of CAKUT is caused by various environmental, genetic, and epigenetic factors that disrupt normal nephrogenesis. Environmental factors that can lead to CAKUT include maternal diabetes, obesity, malnutrition, alcohol consumption, or medications affecting kidneys development. Genetic factors can cause an imbalance in the metanephros and the ureteric bud interaction. Defects in specific genes such as PAX2, TBX18, NRIP1, REX, SIX2, BMP4, and chromosome 17 cause CAKUT. Over 50 genes have been identified as the root cause of this condition, with monogenetic variants causing up to 20% of all cases. CAKUTs can be diagnosed through fetal ultrasonography, but some anomalies may remain undetected. GWASs, Next Generation Sequencing for targeted and whole exome DNA sequencing may provide additional diagnostic methods. This review article highlights some the leading factors that cause CAKUT, which adversely affects kidney development and urinary tract function.

Expression Profiles of ITGA8 and VANGL2 Are Altered in Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)

Kidney failures in infants are mostly caused by congenital anomalies of the kidney and urinary tract (CAKUT), which are among the most common congenital birth disorders worldwide when paired with cardiac abnormalities. People with CAKUT often have severe kidney failure as a result of a wide range of abnormalities that can occur alone or in conjunction with other syndromic disorders. In this study, we aimed to investigate the expression pattern of CAKUT candidate genes alpha-8 integrin (ITGA8) and Van Gogh-like 2 (VANGL2) in fetal tissues of healthy and CAKUT-affected kidneys using immunohistochemistry and immunofluorescence. We found that under CAKUT circumstances, the expressions of ITGA8 and VANGL2 are changed. Additionally, we showed that VANGL2 expression is constant during fetal aging, but ITGA8 expression varies. Moreover, compared to normal healthy kidneys (CTRL), ITGA8 is poorly expressed in duplex kidneys (DKs) and dysplastic kidneys (DYS), whereas VANGL2 is substantially expressed in dysplastic kidneys (DYS) and poorly expressed in hypoplastic kidneys (HYP). These results point to VANGL2 and ITGA8 as potential prognostic indicators for CAKUT malformations. Further research is necessary to explore the molecular mechanisms underlying this differential expression of ITGA8 and VANGL2.

Palliative Care for Pediatric Urology

Palliative care in the field of urology has largely been limited to adult oncologic conditions. Although there is a plethora of established literature suggesting the advantageous impact of palliative care, there is limited integration of palliative care in adult urology. This underutilization is further exacerbated in pediatric urology, and palliative care in pediatric urology remains an underexplored area despite the prevalence of several life-limiting conditions in this patient population. This paper highlights the potential need for palliative care intervention in a variety of urologic conditions in the pediatric population, including congenital lower urinary tract obstruction, neurogenic bladder dysfunction, exstrophy-epispadias complex, and congenital bilateral renal agenesis. Each condition poses unique challenges that can be addressed with the inclusion of a palliative care team, including decision-making spanning prenatal-neonatal-pediatric periods, acute and chronic symptom management, family relations, body image issues, risk of recurrent hospitalizations and surgeries, and potentially fatal complications. Alongside standard urologic interventions, palliative care can serve as an additional means of addressing physical and psychosocial symptoms experienced by pediatric urology patients to enhance the quality of life of patients and their families.

Spectrum of congenital anomalies of the kidney and urinary tract (CAKUT) including renal parenchymal malformations during fetal life and the implementation of prenatal exome sequencing (WES)

OBJECTIVES AND BACKGROUND

Congenital malformations of the kidney and urinary tract (CAKUT) have a prevalence of 4-60 in 10,000 livebirths and constitute for 40-50% of all end stage pediatric kidney disease. CAKUT can have a genetic background due to monogenetic inherited disease, such as PKD or ciliopathies. They can also be found in combination with extra-renal findings as part of a syndrome. Upon detection of genitourinary malformations during the fetal anomaly scan the question arises if further genetic testing is required. The purpose of this study was to determine the phenotypic presentation of CAKUT cases and the results of exome analysis (WES).

METHODS

This is a retrospective analysis of 63 fetal cases with a diagnosis of CAKUT or DSD at a single center between August 2018 and December 2022.

RESULTS

A total of 63 cases (5.6%) out of 1123 matched CAKUT phenotypes including renal parenchyma malformations. In 15 out of 63 WES analysis a pathogenic variant was detected (23.8%). In fetuses with isolated CAKUT the rate of detecting a pathogenic variant on exome sequencing was five out of 44 (11.4%). Ten out of 19 fetuses (52.6%) that displayed extra-renal findings in combination with CAKUT were diagnosed with a pathogenic variant.

CONCLUSIONS

WES provides an increase in diagnosing pathogenic variants in cases of prenatally detected CAKUT. Especially in fetuses with extra-renal malformations, WES facilitates a gain in information on the fetal genotype to enhance prenatal counselling and management.

Expression of Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) Candidate Genes EDA2R, PCDH9, and TRAF7 in Normal Human Kidney Development and CAKUT

Approximately half of the cases of chronic kidney disease (CKD) in childhood are caused by congenital anomalies of the kidney and urinary tract (CAKUT). Specific genes were identified as having significant importance in regard to the underlying genetic factors responsible for the CAKUT phenotype, and in our research, we focused on analyzing and comparing the expression levels of ectodysplasin A2 receptor (EDA2R), protocadherin9 (PCDH9), and TNF receptor-associated factor 7 (TRAF7) proteins in the cortex and medulla of healthy control kidneys during developmental phases 2, 3, and 4. We also performed an analysis of the area percentages of the mentioned proteins in the cortical and medullary sections of healthy embryonic and fetal kidneys compared to those affected by CAKUT, including duplex kidneys (DK), horseshoe kidneys (HK), hypoplastic kidneys (HYP), and dysplastic kidneys (DYS). We found that the CAKUT candidate gene proteins EDA2R, PCDH9, and TRAF7 are all expressed during normal human kidney development stages. In DYS, the expression of EDA2R was higher than in normal kidneys, likely due to EDA2R's role in apoptosis, which was upregulated in specific cases and could possibly contribute to the formation of DYS. The expression of PCDH9 was lower in HK, which can be attributed to the possible role of PCDH9 in cell migration suppression. Decreased PCDH9 expression is linked to increased cell migration, potentially contributing to the development of HK. The level of TRAF7 expression was reduced in all examined kidney disorders compared to normal kidneys, suggesting that this reduction might be attributed to the crucial role of TRAF7 in the formation of endothelium and ciliogenesis, both of which are essential for normal kidney development. Further research is required to ascertain the function of these proteins in both the typical development of the kidney and in CAKUT.

Severe Fetal CAKUT (Congenital Anomalies of the Kidneys and Urinary Tract), Prenatal Consultations, and Initiation of Neonatal Dialysis

INTRODUCTION

Pediatric nephrology prenatal consultations for congenital anomalies of the kidney and urinary tract (CAKUT) and criteria for kidney replacement therapy initiation in neonatal end-stage kidney disease (ESKD) are not well described. We evaluated pediatric nephrology approaches to prenatal CAKUT counseling and neonatal dialysis initiation.

METHODS

A 35-question Qualtrics survey was distributed via the North American Pediatric Renal Trials and Collaborative Studies email list between January and March 2021. Thirty-nine pediatric nephrology centers completed the survey.

RESULTS

All but one responding center (n = 38) provide prenatal CAKUT consultations and neonatal dialysis, with wide variability in reported multispecialty involvement. Nearly half (47%) of centers utilize written/unwritten criteria for offering neonatal dialysis. The most common contraindications to neonatal dialysis were parental refusal (61%), contraindication to access placement by surgeons (55%), and birth weight (BW) contraindication (55%, with < 1,500 g being the most common BW contraindication). Overall, 79% of centers reported caring for < 5 neonates with ESKD in the past year, 61% use hemodialysis therapies prior to peritoneal dialysis in neonates requiring dialysis, and 100% transition to peritoneal dialysis by hospital discharge.

CONCLUSION

Many pediatric nephrology programs provide prenatal CAKUT consultations and neonatal dialysis, but with variability in practice approach. Further multicenter research regarding prenatal consultations and neonatal dialysis outcomes is necessary to further improve care delivery to this population.

Congenital anomalies of kidney and urinary tract (CAKUT) and associated extra-renal anomalies in fetal autopsies

OBJECTIVES AND BACKGROUND

According to studies, 1% of all pregnancies have an abnormality, with 20-30% of those affecting the genitourinary system. Congenital abnormalities of the kidney and urinary tract (CAKUT) is one of the primary causes of perinatal and neonatal mortality in children. Many extra-renal congenital illnesses accompany these defects, affecting the patient's prognosis. This study aims to determine the subtypes, frequency, and extra-renal defects associated with congenital anomalies of the urinary system, which is the major cause of mortality in fetal and infant autopsies throughout the perinatal and neonatal eras. We believe that our study will contribute to the literature because few autopsy investigations can give this data.

MATERIALS AND METHODS

The study included 110 fetal autopsies between January 1997 and May 2019. 10% were newborns under the age of one year, and 90% were fetus autopsies.

RESULTS

Males accounted for 67.3% of the cases, while females accounted for 35 (31.8%) (the gender of one case could not be determined). Renal dysplasia was the most frequent CAKUT, with a rate of 22.73%, followed by renal agenesis, with a rate of 20.0%. Eighty-four cases (76.3%) showed disease in at least one other organ system. Musculoskeletal system (MSS) abnormalities were the most common associated system anomaly, with one or more MSS anomalies (34.55%) detected in 38 cases.

CONCLUSION

Finally, we want to underline that CAKUT and its associated anomalies are not uncommon. Prenatal imaging, genetic investigation, and/or postmortem examination should all be used to screen for CAKUT. This information is helpful for the mother's future pregnancy management and parental genetic counseling.

Renal Hypodysplasia/Aplasia 3 Caused by a Rare Variant of GREB1L With Incomplete Penetrance in a Chinese Family

Renal agenesis represents the most severe form of congenital anomalies of the kidney and urinary tract. Bilateral renal agenesis is almost invariably fatal at birth and has high genetic heterogeneity. Here we report on a Chinese family with two pregnancies affected by a prenatal form of bilateral renal agenesis. Trio-WES was conducted to explore the underlying genetic cause and identified a novel nonsense variant (c .2621G>A: p. Trp874Ter) in the GREB1L gene. Based on previous research, pathogenic mutations in GREB1L can cause renal hypodysplasia/aplasia-3 (RHDA3) with autosomal dominant inheritance. Sanger sequencing performed on the family members revealed that the variant was vertically transmitted from the maternal grandfather through the unaffected mother to the two affected fetuses, fully demonstrating the incomplete dominance of the disease. Our study extends the mutational spectrum associated with RHDA3 and contributes to a more general understanding for the complex genetic inheritance of GREB1L.

When should we offer antenatal sequencing for urinary tract malformations? A systematic review, cohort study and meta-analysis

OBJECTIVE

Determine the incremental yield of prenatal exome sequencing (PES) over chromosome microarray (CMA) and/or karyotype for urinary tract malformations (UTMs).

METHOD

A prospective cohort study encompassing data from the English Genomic Medicine Service North Thames Laboratory Hub for fetuses with bilateral echogenic kidneys (BEKs) was combined with data from a systematic review. MEDLINE, EMBASE, Web of Science, MedRxiv and GreyLit were searched from 01/2010-02/2023 for studies reporting on the yield of PES over CMA or karyotype in fetuses with UTMs. Pooled incremental yield was determined using a random effects model. PROSPERO CRD42023364544.

RESULTS

Fourteen studies (410 cases) were included. The incremental yield for multisystem UTMs, any isolated UTMs, and BEKs was 31% [95% CI, 18%-46%; I2  = 78%], 16% [95% CI, 6%-26%; I2  = 80%] and 51% [95% CI, 27%-75%; I2  = 34%]. The most common clinical diseases and syndromes identified, based on the variant genes detected, were Bardet-Biedl syndrome (BBS genes), dominant and recessive polycystic kidney diseases (PKD1, PKD2 and PKHD1) and renal cysts and diabetes syndrome (HNF1B).

CONCLUSION

There was a notable incremental genetic diagnostic yield when PES was applied to multisystem UTMs and BEKs. There was a modest incremental yield when this technique was used for UTMs other than BEKs.

The genetic etiologies of bilateral renal agenesis

OBJECTIVE

The goal of this study was to review and analyze the medical literature for cases of prenatal and/or postnatally diagnosed bilateral renal agenesis (BRA) and create a comprehensive summary of the genetic etiologies known to be associated with this condition.

METHODS

A literature search was conducted as a scoping review employing Online Mendeliain Inheritance in Man, PubMed, and Cochrane to identify cases of BRA with known underlying genetic (chromosomal vs. single gene) etiologies and those described in syndromes without any known genetic etiology. The cases were further categorized as isolated versus non-isolated, describing additional findings reported prenatally, postnatally, and postmortem. Inheritance pattern was also documented when appropriate in addition to the reported timing of diagnosis and sex.

RESULTS

We identified six cytogenetic abnormalities and 21 genes responsible for 20 single gene disorders associated with BRA. Five genes have been reported to associate with BRA without other renal anomalies; sixteen others associate with both BRA as well as unilateral renal agenesis. Six clinically recognized syndromes/associations were identified with an unknown underlying genetic etiology. Genetic etiologies of BRA are often phenotypically expressed as other urogenital anomalies as well as complex multi-system syndromes.

CONCLUSION

Multiple genetic etiologies of BRA have been described, including cytogenetic abnormalities and monogenic syndromes. The current era of the utilization of exome and genome-wide sequencing is likely to significantly expand our understanding of the underlying genetic architecture of BRA.

Critical diseases in neonates after discharge home from birth hospital: A retrospective study from a tertiary hospital in Japan

INTRODUCTION

To establish actionable neonatal screening during the first month of life, we investigated critical diseases in seemingly healthy newborns discharged from birth hospitals.

METHODS

This retrospective study enrolled previously healthy full-term infants who visited our hospital, a tertiary hospital in Japan, from home between 5 and 28 days after birth from 2009 to 2018. Infants with known perinatal or congenital diseases, positive newborn screening results, or accidental injuries were excluded. Data were collected from electronic medical records, including principal diagnosis, clinical details, and prognosis at 18 months of age.

RESULTS

Ninety-seven (58 %) of 168 eligible neonates were admitted to the hospital, and 71 (42 %) were not. The median admission rate in patients with disease onset at ≤14 days after birth (80 %) was significantly higher than that in patients with disease onset at ≥15 days (42 %). Among 45 patients who received intensive medical care, 5 died and 10 developed neurodevelopmental sequelae. Four of 5 patients died by 100 days. Among 25 diseases treated in intensive care unit, 17 (68 %) diseases had a prevalence of <1 per 2000 live births. The commonly used diagnostic methods were imaging (n = 58, 35 %) and physical examination (n = 34, 20 %).

CONCLUSION

Critical diseases due to rare and heterogeneous causes in ostensibly healthy newborns occurred predominantly in the first two weeks of life. Optimal newborn screening and health check-up protocols may benefit from the wide spectrum of life-threatening diseases occurring in home after birth.

Cystic Kidney Diseases in Children and Adults: Differences and Gaps in Clinical Management

Cystic kidney diseases, when broadly defined, have a wide differential diagnosis extending from recessive diseases with a prenatal or pediatric diagnosis, to the most common autosomal-dominant polycystic kidney disease primarily affecting adults, and several other genetic or acquired etiologies that can manifest with kidney cysts. The most likely diagnoses to consider when assessing a patient with cystic kidney disease differ depending on family history, age stratum, radiologic characteristics, and extrarenal features. Accurate identification of the underlying condition is crucial to estimate the prognosis and initiate the appropriate management, identification of extrarenal manifestations, and counseling on recurrence risk in future pregnancies. There are significant differences in the clinical approach to investigating and managing kidney cysts in children compared with adults. Next-generation sequencing has revolutionized the diagnosis of inherited disorders of the kidney, despite limitations in access and challenges in interpreting the data. Disease-modifying treatments are lacking in the majority of kidney cystic diseases. For adults with rapid progressive autosomal-dominant polycystic kidney disease, tolvaptan (V2-receptor antagonist) has been approved to slow the rate of decline in kidney function. In this article, we examine the differences in the differential diagnosis and clinical management of cystic kidney disease in children versus adults, and we highlight the progress in molecular diagnostics and therapeutics, as well as some of the gaps meriting further attention.

Hedgehog-GLI mediated control of renal formation and malformation

CAKUT is the leading cause of end-stage kidney disease in children and comprises a broad spectrum of phenotypic abnormalities in kidney and ureter development. Molecular mechanisms underlying the pathogenesis of CAKUT have been elucidated in genetic models, predominantly in the mouse, a paradigm for human renal development. Hedgehog (Hh) signaling is critical to normal embryogenesis, including kidney development. Hh signaling mediates the physiological development of the ureter and stroma and has adverse pathophysiological effects on the metanephric mesenchyme, ureteric, and nephrogenic lineages. Further, disruption of Hh signaling is causative of numerous human developmental disorders associated with renal malformation; Pallister-Hall Syndrome (PHS) is characterized by a diverse spectrum of malformations including CAKUT and caused by truncating variants in the middle-third of the Hh signaling effector GLI3. Here, we outline the roles of Hh signaling in regulating murine kidney development, and review human variants in Hh signaling genes in patients with renal malformation.

Immunoexpression Pattern of Autophagy Markers in Developing and Postnatal Kidneys of Dab1−/−(yotari) Mice

The purpose of this study was to compare the immunofluorescence patterns of autophagic markers: Light chain 3 beta (LC3B), Glucose regulating protein 78 (GRP78), Heat shock cognate 71 (HSC70) and Lysosomal-associated membrane protein 2A (LAMP2A) in the developing and postnatal kidneys of Dab1−/− (yotari) mice to those of wild-type samples. Embryos were obtained on gestation days 13.5 and 15.5 (E13.5 and E15.5), and adult animals were sacrificed at postnatal days 4, 11 and 14 (P4, P11, and P14). After fixation and dehydration, paraffin-embedded kidney tissues were sectioned and incubated with specific antibodies. Using an immunofluorescence microscope, sections were analyzed. For statistical analysis, a two-way ANOVA test and a Tukey’s multiple comparison test were performed with a probability level of p < 0.05. A significant increase in GRP78 and LAMP2A expression was observed in the renal vesicles and convoluted tubules of yotari in embryonic stages. In postnatal kidneys, all observed proteins showed higher signal intensities in proximal and distal convoluted tubules of yotari, while a higher percentage of LC3B-positive cells was also observed in glomeruli. Our findings suggest that all of the examined autophagic markers play an important role in normal kidney development, as well as the potential importance of these proteins in renal pathology, where they primarily serve a protective function and thus may be used as diagnostic and therapeutic targets.

Renal-hepatic-pancreatic dysplasia type 2: Perinatal lethal condition or a multisystemic disorder with variable expressivity

BACKGROUND

Renal-hepatic-pancreatic dysplasia type 2 (RHPD2) is a rare condition that has been described in the literature disproportionately in perinatal losses. The main features of liver and kidney involvement are well described, with cardiac malformations and cardiomyopathy adding additional variation to the phenotype. Many patients reported are within larger cohorts of congenital anomalies of kidney and urinary tract (CAKUT) or liver failure, and with minimal phenotypic and clinical course data.

METHODS

An independent series of phenotypes and prognosis was aggregated from the literature. In this literature review, we describe an additional patient with RHPD2, provide a clinical update on the oldest known living patient, and report the cumulative phenotypes from the existing published patients.

RESULTS

With now examining the 17 known patients in the literature, 13 died within the perinatal period-pregnancy to one year of life. Of the four cases living past the first year of life, one case died at 5 years secondary to renal failure, the other at 30 months secondary to liver and kidney failure. Two are currently alive and well at one year and 13 years. Two cases have had transplantation with one resulting in long-term survival.

CONCLUSIONS

These patients serve to expand the existing phenotype of RHPD2 as a perinatal lethal condition into a pediatric disorder with variable expressivity. Additionally, we introduce the consideration of transplantation and outcomes within this cohort and future patients.

Disease mechanisms of monogenic congenital anomalies of the kidney and urinary tract American Journal of Medical Genetics Part C

Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) is a developmental disorder of the kidney and/or genito-urinary tract that results in end stage kidney disease (ESKD) in up to 50% of children. Despite the congenital nature of the disease, CAKUT accounts for almost 10% of adult onset ESKD. Multiple lines of evidence suggest that CAKUT is a Mendelian disorder, including the observation of familial clustering of CAKUT. Pathogenesis in CAKUT is embryonic in origin, with disturbances of kidney and urinary tract development resulting in a heterogeneous range of disease phenotypes. Despite polygenic and environmental factors being implicated, a significant proportion of CAKUT is monogenic in origin, with studies demonstrating single gene defects in 10%-20% of patients with CAKUT. Here, we review monogenic disease causation with emphasis on the etiological role of gene developmental pathways in CAKUT.

Birth defects data from hospital-based birth defect surveillance in Guilin, China, 2018-2020

Objectives

Birth defects (BDs) are a major contributor to perinatal and infant mortality, morbidity and lifelong disability worldwide. A hospital-based study on birth defects was designed in Guilin city in the Guangxi province of Southwestern China aiming to determine the prevalence of BDs in the studied region, and the classify the BDs based on clinical presentation and causation.

Methods

The study involved BDs among all pregnancy outcomes (live births, stillbirths, death within 7 days, and pregnancy terminations) born in the 42 registered hospitals of Guilin between 2018 and 2020. The epidemiological characteristics of BDs and the etiologic profile of BDs were evaluated in this study.

Results

Of the total 147,817 births recorded during the study period, 2,003 infants with BDs were detected, giving a total prevalence rate of 13.55 per 1,000 births. The top five BD types were congenital heart defects, polydactyly, syndactyly, malformations of the external ear, and talipes equinovarus, whereas, neural tube defects, congential esophageal atresia, gastroschisis, extrophy of urinary bladder, were the least common BD types in these 3 years. Only 8.84% of cases were assigned a known etiology, while most cases (91.16%) could not be conclusively assigned a specific cause.

Conclusion

This study provides an epidemiological description of BDs in Guilin, which may be helpful for understanding the overall situation in Southwest China of BDs and aid in more comprehensive studies of BDs in future healthcare systems, including funding investment, policy-making, monitor, prevention. Strong prevention strategies should be the priority to reduce BDs and improve the birth quality.

Disparate phenotypes in two unfavorable pregnancies due to maternal mosaicism of a novel RET gene mutation

Mutations in RET have been found in multiple diseases including isolated and associated congenital anomalies. Here, we report a case presented with disparate phenotypes in each pregnancy but caused by the same novel mutation. Whole-exome sequencing (WES) was performed on the proband/abortion product-parental trio and a novel missense variant in RET (chr10:43615610C>G; c.2689C>G; p.Arg897Gly) was identified. The mother was a low-level somatic carrier of this new mutation, with 17.3% in blood, 19.1% in oralmucous membrane, and 15.7% in urine by droplet digital polymerase chain reaction (dd PCR). Our finding not only broadens the mutation spectrum of RET but also gives supportive genetic counseling and timely guidance on fertility choices.

Genetic Etiologies, Diagnosis, and Management of Neonatal Cystic Kidney Disease

Fetal kidney development is a complex and carefully orchestrated process. The proper formation of kidney tissue involves many transcription factors and signaling pathways. Pathogenic variants in the genes that encodethese factors and proteins can result in neonatal cystic kidney disease. Advancements in genomic sequencing have allowed us to identify many of these variants and better understand the genetic underpinnings for an increasing number of presentations of childhood kidney disorders. This review discusses the genes essential in kidney development, particularly those involved in the structure and function of primary cilia, and implications of gene identification for prognostication and management of cystic kidney disorders.

Gene Ontology Enrichment Analysis of Renal Agenesis: Improving Prenatal Molecular Diagnosis

Uni- or bilateral renal agenesis (RA) is a commonly occurring major congenital anomaly impacting fetal and neonatal outcomes. Since the etiology is highly heterogeneous, our aim was to provide a logically structured approach by highlighting the genes in which variants have been identified to be associated with RA and to define the pathways involved in this type of abnormal kidney development. We used Phenolyzer to collect a list of all the genes known as causative for RA. Using ClueGO gene enrichment analysis, we classified the relationship between these genes and the biological processes defined by gene ontology. We identified 287 genes and 69 groups of enriched biological processes. About 50% included pathways directly related to the development of urogenital organ tissues. Several ciliary, axis specification, hindgut development, and endocrine pathways were enriched, which may relate to different clinical presentations of RA. Our gene ontology enrichment analysis shows that genes representing distinct biological pathways are significantly enriched. This knowledge will lead to an improved molecular diagnosis in clinical care when applying genome-wide sequencing approaches. The findings will also allow to further study the biological pathways involved in RA and to identify novel candidate genes and pathways.

Long-term follow-up of congenital anomalies of the kidney and urinary tract diagnosed in utero: a longitudinal study

BACKGROUND

Congenital-anomalies of the kidney-and-urinary-tract (CAKUT) are diagnosed in 3-6 per 1000 live-births. The objective of the current study was to examine the short and long-term outcomes of children diagnosed prenatally with CAKUT.

METHODS

A retrospective study was performed in 2018 on all pregnancies diagnosed with CAKUT between 2004 and 2008 at our hospital. Pregnancy outcomes and long-term morbidity were evaluated. Comparison was made between mild and severe forms of CAKUT and between unilateral and bilateral anomalies.

RESULTS

Ninety-eight children were included in the study. Most of them were born with an adequate weight for gestational-age, and were born at term by vaginal-deliveries. Children with major renal anomalies suffered significantly more frequently from recurrent UTIs (33.3% vs. 8.4%), needed more preventive antibiotics (50% vs. 20.5%), and had more renal surgeries (75% vs. 28%) than those with milder forms of CAKUT. Significantly more children with polycystic/multicystic kidney disease had recurrent UTIs (50% compared to 25% of the children with renal agenesis, and 5.6% of the children with hydronephrosis/hydroureter). There were no significant differences in the need for neurodevelopmental follow-up between the different groups of severity. Unilateral CAKUT patients required longer periods of nephrologist follow-up and repeated sonographic exams compared to bilateral CAKUT patients. Children with bilateral CAKUT more often needed special educational support than peers with unilateral disease (29.4% vs. 11.1%, P = 0.03).

CONCLUSIONS

Pregnancies whose children are diagnosed with CAKUT in utero usually deliver at term, with adequate-weight for gestational-age. The most common long-term comorbidities in children were recurrent UTIs and the use of preventive antibiotics was often needed. Expecting couples can be reassured of a generally good outcome of their children, at least during the first decade of life.

Mapping of the amniotic fluid proteome of fetuses with congenital anomalies of the kidney and urinary tract identifies plastin 3 as a protein involved in glomerular integrity

Congenital anomalies of the kidney and the urinary tract (CAKUT) are the first cause of chronic kidney disease in childhood. Several genetic and environmental origins are associated with CAKUT, but most pathogenic pathways remain elusive. Considering the amniotic fluid (AF) composition as a proxy for fetal kidney development, we analyzed the AF proteome from non-severe CAKUT (n = 19), severe CAKUT (n = 14), and healthy control (n = 22) fetuses using LC-MS/MS. We identified 471 significant proteins that discriminated the three AF groups with 81% precision. Among them, eight proteins independent of gestational age (CSPG4, LMAN2, ENDOD1, ANGPTL2, PRSS8, NGFR, ROBO4, PLS3) were associated with both the presence and the severity of CAKUT. Among those, five were part of a protein-protein interaction network involving proteins previously identified as being potentially associated with CAKUT. The actin-bundling protein PLS3 (plastin 3) was the only protein displaying a gradually increased AF abundance from control, via non-severe, to severe CAKUT. Immunohistochemistry experiments showed that PLS3 was expressed in the human fetal as well as in both the fetal and the postnatal mouse kidney. In zebrafish embryos, depletion of PLS3 led to a general disruption of embryonic growth including reduced pronephros development. In postnatal Pls3-knockout mice, kidneys were macroscopically normal, but the glomerular ultrastructure showed thickening of the basement membrane and fusion of podocyte foot processes. These structural changes were associated with albuminuria and decreased expression of podocyte markers including Wilms' tumor-1 protein, nephrin, and podocalyxin. In conclusion, we provide the first map of the CAKUT AF proteome that will serve as a reference for future studies. Among the proteins strongly associated with CAKUT, PLS3 did surprisingly not specifically affect nephrogenesis but was found as a new contributor in the maintenance of normal kidney function, at least in part through the control of glomerular integrity. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Etiology and management of early pregnancy renal anhydramnios: Is there a place for serial amnioinfusions?

Early pregnancy renal anhydramios (EPRA) comprises congenital renal disease that results in fetal anhydramnios by 22 weeks of gestation. It occurs in over 1 in 2000 pregnancies and affects 1500 families in the US annually. EPRA was historically considered universally fatal due to associated pulmonary hypoplasia and neonatal respiratory failure. There are several etiologies of fetal renal failure that result in EPRA including bilateral renal agenesis, cystic kidney disease, and lower urinary tract obstruction. Appropriate sonographic evaluation is required to arrive at the appropriate urogenital diagnosis and to identify additional anomalies that allude to a specific genetic diagnosis. Genetic evaluation variably includes karyotype, microarray, targeted gene testing, panels, or whole exome sequencing depending on presentation. Patients receiving a fetal diagnosis of EPRA should be offered management options of pregnancy termination or perinatal palliative care, with the option of serial amnioinfusion therapy offered on a research basis. Preliminary data from case reports demonstrate an association between serial amnioinfusion therapy and short-term postnatal survival of EPRA, with excellent respiratory function in the neonatal period. A multicenter trial, the renal anhydramnios fetal therapy (RAFT) trial, is underway. We sought to review the initial diagnosis ultrasound findings, genetic etiologies, and current management options for EPRA.