Evidence for genetic heterogeneity in hereditary hydronephrosis caused by pelvi-ureteric junction obstruction, with one locus assigned to chromosome 6p

Novel perspectives for investigating congenital anomalies of the kidney and urinary tract (CAKUT)

Congenital anomalies of the kidney and urinary tract (CAKUT) are the commonest cause of chronic kidney disease in children. Structural anomalies within the CAKUT spectrum include renal agenesis, kidney hypo-/dysplasia, multicystic kidney dysplasia, duplex collecting system, posterior urethral valves and ureter abnormalities. While most CAKUT cases are sporadic, familial clustering of CAKUT is common, emphasizing a strong genetic contribution to CAKUT origin. Animal experiments demonstrate that alterations in genes crucial for kidney development can cause experimental CAKUT, while expression studies implicate mislocalization and/or aberrant levels of the encoded proteins in human CAKUT. Further insight into the pathogenesis of CAKUT will improve strategies for early diagnosis, follow-up and treatment. Here, we outline a collaborative approach to identify and characterize novel factors underlying human CAKUT. This European consortium will share the largest collection of CAKUT patients available worldwide and undertake multidisciplinary research into molecular and genetic pathogenesis, with extension into translational studies to improve long-term patient outcomes.

Pelvi-ureteric junction obstruction in autosomal-dominant polycystic kidney disease: an association yet to be reported

Autosomal-dominant polycystic kidney disease (ADPKD) is the most common inherited renal cystic disease. It is characterised by the development of renal parenchymal cysts and a variety of other extrarenal manifestations. Pelvi-ureteric junction (PUJ) obstruction has not been described in association with ADPKD in the literature. We present a case of a 23-year-old man presenting with bilateral flank pain. On evaluation he was diagnosed to have ADPKD with bilateral renal calculi and left-sided PUJ obstruction. He underwent successful right percutaneous nephrolithotomy and left laparoscopic dismembered pyeloplasty with simultaneous stone removal.

The Society for Fetal Urology consensus statement on the evaluation and management of antenatal hydronephrosis

The evaluation and management of fetuses/children with antenatal hydronephrosis (ANH) poses a significant dilemma for the practitioner. Which patients require evaluation, intervention or observation? Though the literature is quite extensive, it is plagued with bias and conflicting data, creating much confusion as to the optimal care of patients with ANH. In this article, we summarized the literature and proposed recommendations for the evaluation and management of ANH.

Analysis of TSHZ2 and TSHZ3 genes in congenital pelvi-ureteric junction obstruction

BACKGROUND

Congenital pelvi-ureteric junction obstruction (PUJO) affects 0.3% of human births. It may result from aberrant smooth muscle development in the renal pelvis, resulting in hydronephrosis. Mice that are null mutant for the Teashirt3 (Tshz3) gene exhibit congenital PUJO with defective smooth muscle differentiation and absent peristalsis in the proximal ureter.

METHODS

Given the phenotype of Tshz3 mutant mice, we considered that Teashirt genes, which code for a family of transcription factors, might represent candidate genes for human PUJO. To evaluate this possibility, we used in situ hydridization to analyse the three mammalian Tshz genes in mouse embryonic ureters and determined whether TSHZ3 was expressed in the human embryonic ureter. TSHZ2 and TSHZ3 were sequenced in index cases with non-syndromic PUJO.

RESULTS

Tshz2 and Tshz3 genes were detected in mouse ureters and TSHZ3 was expressed in the human embryonic renal pelvis. Direct sequencing of TSHZ2 and TSHZ3 did not identify any mutations in an initial cohort of 48 PUJO index cases, excluding these genes as a major cause of this condition. A polymorphic missense change (E469G) in TSHZ3 was identified at a residue highly conserved throughout evolution in all Teashirt proteins, although subsequently no significant difference between the E469G allele frequency in Albanian and Macedonian PUJO index cases (3.2%) versus 633 control individuals (1.7%) was found (P = 0.18).

CONCLUSIONS

Mutations in TSHZ2 and TSHZ3 are not a major cause of PUJO, at least in Albanian and Macedonian populations. Expression of these genes in the human fetal ureter emphasizes the importance of analysing these genes in other groups of patients with renal tract malformations.

Mapping of a new locus for congenital anomalies of the kidney and urinary tract on chromosome 8q24

BACKGROUND

Congenital anomalies of the kidney and urinary tract (CAKUT) account for the majority of end-stage renal disease in children (50%). Previous studies have mapped autosomal dominant loci for CAKUT. We here report a genome-wide search for linkage in a large pedigree of Somalian descent containing eight affected individuals with a non-syndromic form of CAKUT.

METHODS

Clinical data and blood samples were obtained from a Somalian family with eight individuals with CAKUT including high-grade vesicoureteral reflux and unilateral renal agenesis. Total genome search for linkage was performed using a 50K SNP Affymetric DNA microarray. As neither parent is affected, the results of the SNP array were analysed under recessive models of inheritance, with and without the assumption of consanguinity.

RESULTS

Using the non-consanguineous recessive model, a new gene locus (CAKUT1) for CAKUT was mapped to chromosome 8q24 with a significant maximum parametric Logarithm of the ODDs (LOD) score (LOD(max)) of 4.2. Recombinations were observed in two patients defining a critical genetic interval of 2.5 Mb physical distance flanked by markers SNP_A-1740062 and SNP_A-1653225.

CONCLUSION

We have thus identified a new non-syndromic recessive gene locus for CAKUT (CAKUT1) on chromosome 8q24. The identification of the disease-causing gene will provide further insights into the pathogenesis of urinary tract malformations and mechanisms of renal development.

Genetic and developmental basis for urinary tract obstruction

Urinary tract obstruction results in obstructive nephropathy and uropathy. It is the most frequent cause of renal failure in infants and children. In the past two decades studies of transgenic models and humans have greatly enhanced our understanding of the genetic factors and developmental processes important in urinary tract obstruction. The emerging picture is that development of the urinary tract requires precise integration of a variety of progenitor cell populations of different embryonic origins. Such integration is controlled by an intricate signaling network that undergoes dynamic changes as the embryo develops. Most congenital forms of urinary tract obstruction result from the disruption of diverse factors and genetic pathways involved in these processes, especially in the morphogenesis of the urinary conduit or the functional aspects of the pyeloureteral peristaltic machinery.

Hypercalciuria in pediatric patients with ureteropelvic junction obstruction is of genetic origin

OBJECTIVE

Genitourinary tract malformations are associated with urolithiasis. Hypercalciuria has been described in children with ureteropelvic junction obstruction (UPJO), although the etiology of this metabolic abnormality remains unknown. This study was conducted to find out whether children with UPJO have a higher prevalence of hypercalciuria and whether their family members are affected by hypercalciuria and/or urolithiasis.

MATERIAL AND METHODS

We studied the prevalence of hypercalciuria and urolithiasis in 27 children (14 males, 13 females) with UPJO and their parents.

RESULTS

One patient had a history of renal colic, whereas imaging studies showed macroscopic renal lithiasis in two patients and calyceal microlithiasis in four. Hypercalciuria was found in 17/27 children (63%), 15 of whom (88%) had a familial history of urolithiasis: seven families in first-degree relatives, six in second-degree relatives and two in other relatives. Concerning the 10 children without hypercalciuria, seven of them (70%) had a family history of urolithiasis: four in first-degree relatives and three in second-degree relatives. The prevalences of both urolithiasis and hypercalciuria were not influenced by gender.

CONCLUSIONS

Urolithiasis is associated with hypercalciuria in patients with UPJO. In accordance with previous data, our results show that the prevalence of hypercalciuria is greater in pediatric patients with UPJO than in the general population. Likewise, the prevalence of urolithiasis in the families of these children is also higher than that in the general population. Hypercalciuria was inherited as an autosomal dominant trait.

A genome search for primary vesicoureteral reflux shows further evidence for genetic heterogeneity

Vesicoureteral reflux (VUR) is the most common disease of the urinary tract in children. In order to identify gene(s) involved in this complex disorder, we performed a genome-wide search in a selected sample of 31 patients with primary VUR from eight families originating from southern Italy. Sixteen additional families with 41 patients were included in a second stage. Nonparametric, affected-only linkage analysis identified four genomic areas on chromosomes 1, 3, and 4 (p < 0.05); the best result corresponded to the D3S3681-D3S1569 interval on chromosome 3 (nonparametric linkage score, NPL = 2.75, p = 0.008). This region was then saturated with 26 additional markers, tested in the complete group of 72 patients from 24 families (NPL = 2.01, p = 0.01). We identified a genomic area on 3q22.2-23, where 26 patients from six multiplex families shared overlapping haplotypes. However, we did not find evidence for a common ancestral haplotype. The region on chromosome 1 was delimited to 1p36.2-34.3 (D1S228-D1S255, max. NPL = 1.70, p = 0.03), after additional fine typing. Furthermore, on chromosome 22q11.22-12.3, patients from a single family showed excess allele sharing (NPL = 3.35, p = 0.015). Only the chromosome 3q region has been previously reported in the single genome-wide screening available for primary VUR. Our results suggest the presence of several novel loci for primary VUR, giving further evidence for the genetic heterogeneity of this disorder.

Inheritance of pericentric inversion in chromosome 7 through the three progenies and a newborn with congenital hydronephrosis diagnosed prenatally by fetal urine sampling

OBJECTIVE

To report the inheritance of a pericentric inversion in chromosome 7 through the three progenies, congenital hydronephrosis, and recurrent miscarriages in an extended family.

DESIGN

Case report.

SETTING

Medical Faculty of Cukurova University in Turkey.

PATIENT(S)

Referred by obstetrics and gynecology clinic.

INTERVENTION(S)

Fetal urine and lymphocytic karyotype.

MAIN OUTCOME MEASURE(S)

Chromosomal analysis from fetal urine and peripheral blood lymphocytes were performed according to standard cytogenetic methods.

RESULT(S)

We assessed an extended family in which a large pericentric inversion in chromosome 7 is segregating; one of the three progenies with the karyotype 46,XY,inv(7)(p22;q22) was heterozygote for the inversion and presented with congenital hydronephrosis. His mother, mother's brother, grandfather, grandfather's brother, and his daughter were similar for the inversion.

CONCLUSION(S)

This case describes the further molecular characterization of these breakpoints on the short or long arm of chromosome 7(p22-q22). The inv(7) is also associated with fetal wastage and may be playing a role in the etiology of the family's miscarriages. These findings can be used in clinical genetics and may be an effective tool for reproductive guidance and genetic counseling.

Angiotensin-converting enzyme and angiotensin type 2 receptor gene genotype distributions in Italian children with congenital uropathies

Angiotensin I-converting enzyme (ACE) and angiotensin type 2 receptor (AT2R) gene polymorphisms have been associated with an increased incidence of congenital anomalies of the kidney and urinary tract (CAKUT). We investigated the genotype distribution of these polymorphisms in Italian children with CAKUT. We also evaluated the association between the ACE insertion/deletion and the AT2R gene polymorphisms with the progression of renal damage in subgroups of CAKUT patients. We recruited 102 Italian children with CAKUT; 27 with vesicoureteral reflux; 12 with hypoplastic kidneys; 20 with multicystic dysplastic kidneys; 13 with ureteropelvic junctions stenosis/atresia; 18 with nonobstructed, nonrefluxing primary megaureters; and 12 with posterior urethral valves and compared them with 92 healthy control subjects. ACE and AT2R gene polymorphisms were analyzed by PCR. The identification of AT2R gene polymorphisms in intron 1 and in exon 3 was revealed by enzymatic digestion. ACE genotype distribution in children with CAKUT was no different from that of the control subjects, but the subgroup of patients with radiographic renal parenchymal abnormalities showed an increased occurrence of the D/D genotype. The frequency of the G allele of AT2R gene in children with CAKUT was increased in respect to that of the control subjects. By contrast, no significant difference in the frequency of the C and A alleles of the AT2R gene was found. Our findings indicate that the ACE gene can be a risk factor in the progression of renal parenchymal damage in CAKUT patients. Moreover, a major role of the AT2R gene in the development of CAKUT has been found, at least in Italian children.

Developmental renal pathology: its past, present, and future

Congenital anomalies of the kidney and urinary tract are responsible for approximately 40% of cases of childhood end-stage renal failure in the United States. This article describes the spectrum of developmental renal lesions in children (including renal agenesis, dysplasias, hereditary hydronephrosis, autosomal recessive and dominant polycystic kidneys, vesicoureteral reflux, diabetic embryopathy, some teratogenic drugs affecting renal development, and syndromes associated with renal dysplasias). The article quotes some historic references that established the foundation for further studies; reviews the embryology, pathology, postnatal renal development, and its possible consequences of renal function; as well as recent advances in fetal ultrasonography and molecular biology with some novel treatment and diagnostic modalities. Finally, an attempt is made to predict several future avenues in pharmacogenetics that are being built currently and that will allow a better prognosis for many children with congenital renal conditions.

Steroid-resistant nephrotic syndrome and congenital anomalies of kidneys: evidence of locus on chromosome 13q

BACKGROUND

Steroid-resistant nephrotic syndrome (SRNS) and congenital anomalies of kidney and urinary tract (CAKUT) are major causes of renal dysfunction in children. Although a few patients with 13q deletion have been previously reported with renal anomalies, the association of SRNS with 13q has not been reported and critical regions associated with CAKUT have not been identified. We present the results of deletion mapping studies to identify the critical regions.

METHODS

Cytogenetic and deletion mapping studies were performed on DNA obtained from peripheral blood of two children with renal anomalies and interstitial deletion of 13q as well as their parents. Twenty eight microsatellite markers with a spacing of 1-8 Mb (1-3 cM) were utilized.

RESULTS

The patients (both males, 5 and 10 years old) had varying severity of developmental delay and other neurologic disorders. The renal involvement included hydronephrosis, ureterocele, renal dysplasia, and mesangioproliferative SRNS. Our studies imply existence of at least two critical regions in the 13q area that are linked to CAKUT. The first is a 7 Mb region defined by markers D13S776 and D13S891 shared by both patients. The second is a much larger region extending at least 33 Mb above D13S776 seen in one patient with severe renal malformations and SRNS.

CONCLUSION

We report an association of chromosome 13q with CAKUT as well as SRNS. Our studies suggest the presence of more than one gene in this region that is likely to be involved in renal development and function.

No evidence for AT2R gene derangement in human urinary tract anomalies

BACKGROUND

It has been recently found that mice, especially males, with a disrupted angiotensin type 2 receptor (AT2R) gene, which is located on the X-chromosome, often have a range of congenital anomalies of the kidney and urinary tract (CAKUT), including renal hypoplasia, and that Caucasian male patients with ureteropelvic junction stenosis (UPJ) and multicystic dysplastic kidneys frequently have A-G transition in intron 1 of the AT2R gene. We have previously found that renal hypoplasia is remarkably predominant in Japanese boys.

METHODS

We investigated sex ratios for the frequency of each CAKUT. The frequency of the A-G transition between the controls and 66 Japanese boys with CAKUT were compared. There was renal hypoplasia in 16, UPJ in 17, vesicoureteral in 20, and other anomalies in 13. We also investigated whether any mutations in AT2R genes were detectable in patients with renal hypoplasia.

RESULTS

In contrast to mice with a disruption of the AT2R gene, the male-to-female ratios in human patients proved to be considerably variable: 16 for renal hypoplasia, 2.1 for UPJ, 0.8 for vesicoureteral, and 1.2 for others. The frequency of the A-G transition was not different between the control population and the patients with CAKUT [31 of 102 (30%) vs. 23 of 66 (35%), respectively]. A sequencing study disclosed no mutations in nine boys with renal hypoplasia.

CONCLUSIONS

These findings indicate that the AT2R gene may not play a major role in the development of renal hypoplasia and other CAKUT in humans, at least in the Japanese population.

A molecular and genetic view of human renal and urinary tract malformations

Malformations of the kidney and lower urinary tract are common causes of chronic renal failure in infants and young children, but little is known about the molecular pathogenesis of these disorders. In animal experiments, the main causes of malformation are mutations, chemical and pharmaceutical teratogens, obstruction of fetal urinary flow, and alterations of maternal nutrition. The focus of this review is to consider how mutations and other alterations of gene expression during development cause human urinary tract malformations. Some of these disorders are associated with congenital anomalies in multiple organ systems, and two such syndromes are considered in detail: first, the renal-coloboma syndrome, in which mutations of the PAX2 transcription factor cause partial failure of urinary tract growth; second, Kallmann's syndrome, in which mutations of a cell-signaling molecule are associated with the absence of the urinary tract. In patients seen by nephrologists and urologists, however, most urinary tract malformations occur in isolation, and in some of these individuals, a genetic pathogenesis is strongly suggested by a positive family history and genetic linkage studies. One common example is primary vesicoureteric reflux. Furthermore, sporadic malformations have been shown to be associated with polymorphisms of genes expressed during construction of the urinary tract. In the long term, an understanding of the genetic aspects of human urinary tract malformations will help to unravel the pathogenesis of these disorders and may facilitate the design of genetic screening tests with a view to early diagnosis.

Primary, nonsyndromic vesicoureteric reflux and its nephropathy is genetically heterogeneous, with a locus on chromosome 1

Primary vesicoureteric reflux (VUR) affects 1%-2% of whites, and reflux nephropathy (RN) causes up to 15% of end-stage renal failure in children and adults. There is a 30-50-fold increased incidence of VUR in first-degree relatives of probands, compared with the general population. We report the results of the first genomewide search of VUR and RN; we studied seven European families whose members exhibit apparently dominant inheritance. We initially typed 387 polymorphic markers spaced, on average, at 10 cM throughout the genome; we used the GENEHUNTER program to provide parametric and nonparametric linkage analyses of affected individuals. The most positive locus spanned 20 cM on 1p13 between GATA176C01 and D1S1653 and had a nonparametric LOD score (NPL) of 5.76 (P=.0002) and a parametric LOD score of 3.16. Saturation with markers at 1-cM intervals increased the NPL to 5.94 (P=.00009). Hence, VUR maps to a locus on chromosome 1. There was evidence of genetic heterogeneity at the chromosome 1 locus, and 12 additional loci were identified genomewide, with P<.05. No significant linkage was found to 6p, where a renal and ureteric malformation locus has been reported, or to PAX2, mutations of which cause VUR in renal-coloboma syndrome. Our results support the hypothesis that VUR is a genetic disorder.

Rearrangement of the human CDC5L gene by a t(6;19)(p21;q13.1) in a patient with multicystic renal dysplasia

Genetic studies have implicated the short arm of chromosome 6 in congenital hydronephrosis. In previous studies, we described a fetus carrying a t(6;19)(p21;q13.1) as the sole cytogenetic anomaly and suffering from bilateral multicystic renal dysplasia caused by a bilateral complete pelviureteric junction obstruction, resulting in a massive hydronephrosis. Characterization of the chromosome 19 breakpoint region revealed that the transcription factor-encoding USF2 gene is affected. In this report, we show that the CDC5L gene on chromosome 6p is rearranged in the cells of the fetus. CDC5L encodes a protein that is related to the product of the Schizosaccharomyces pombe Cdc5 gene, which exerts its effects at the G2/M transition during cell cycle progression. We have established the genomic organization of the CDC5L gene and found that it consists of at least 16 exons spanning approximately 50 kb of chromosome segment 6p21. Northern blot analysis indicated that the gene is ubiquitously expressed as a single mRNA of about 3.4 kb in both fetal and adult tissues. The translation product of the CDC5L gene has an electrophoretic mobility of about 100 kDa and is predicted to be a nuclear protein, since it contains a Myb-related DNA binding domain and potential nuclear localization signals in its aminoterminal region. Immunocytochemical analysis confirmed the nuclear localization of the CDC5L protein. CDC5L was also predicted to contain a hydrophilic, proline-rich region in its central part, which might function as a transcriptional activating domain. The chromosome 6 breakpoint was found in the intron between exons 9 and 10, indicating that, as a direct result of the 6;19 translocation, the Myb-related DNA binding domains and the nuclear localization signals are separated from the putative transactivating domain. Northern blot and RT-PCR experiments revealed that the other CDC5L allele is unaffected, and in Western blot experiments, expression of the 100-kDa protein was detected in fibroblasts of the fetus. Expression of a truncated or hybrid CDC5L transcript resulting from the CDC5L rearrangement could not be demonstrated.

Familial hydronephrosis unlinked to the HLA complex

Clinical findings, management, and possible linkage of congenital hydronephrosis caused by ureteropelvic junction stenosis to the HLA complex were studied in four families. These families provide evidence of possible autosomal dominant inheritance. HLA class I antigen studies in all four and class II (HLA-DR) in three families were performed. These studies failed to show close linkage to the chromosome 6 markers in two families but there was consistent inheritance in the other two. Although formal linkage calculations are not presented, it is apparent that in some families HLA haplotyping is not useful in predicting prevence of renal obstruction.

Hereditary renal adysplasia: new observations and hypotheses

Renal agenesis and dysplasia are frequently regarded by pathologists, even pediatric pathologists, as sporadic malformations. We report six fetal autopsy cases of hereditary renal adysplasia (HRA): two pairs of siblings, one case with paternal unilateral renal agenesis, and one case with an autosomal balanced 6p/19q translocation. The main purpose of this paper is to emphasize that nonsyndromal renal agenesis and dysplasia are pathogenetically related and often inherited as an autosomal dominant trait with incomplete penetrance and variable expression. A subsidiary purpose is to present a case of bilateral multicystic dysplasia with a balanced 6p/19q translocation. This observation further supports the assignment of one of the loci for HRA to chromosome 6p.