Classifying and evaluating fetuses with multicystic dysplastic kidney in etiologic studies

Multicystic dysplastic kidney (MCDK) is one of the most common fetal malformations, but its etiology remains unclear. Identification of the molecular etiology could provide a basis for prenatal diagnosis, consultation, and prognosis evaluation for MCDK fetuses. We used chromosome microarray analysis (CMA) and whole-exome sequencing (WES) to conduct genetic tests on MCDK fetuses and explore their genetic etiology. A total of 108 MCDK fetuses with or without other extrarenal abnormalities were selected. Karyotype analysis of 108 MCDK fetuses showed an abnormal karyotype in 4 (3.7%, 4/108) of the fetuses. However, CMA detected 15 abnormal copy number variations (CNVs) (14 pathogenic CNVs, and one variant of unknown significance [VUS] CNVs), in addition to four cases that were consistent with the results of karyotype analysis. Out of the 14 pathogenic CNVs cases, three were of 17q12 microdeletion, two of 22q11.21 microdeletion, 22q11.21 microduplication uniparental disomy (UPD), and one case of 4q31.3q32.2 microdeletion, 7q11.23 microduplication, 15q11.2 microdeletion, 16p11.2 microdeletion, and 17p12 microdeletion. Of the 89 MCDK fetuses with normal karyotype analysis and CMA, 15 were tested by WES. Two (13.3%, 2/15) fetuses were identified by WES as Bardet-Biedl syndrome (BBS) 1 and BBS2. Combined application of CMA-WES to detect MCDK fetuses can significantly improve the detection rate of genetic etiology, providing a basis for consultation, and prognosis evaluation.

[Enlarged multicystic dysplastic kidneys with oligohydramnios during infancy caused by NPHP3 gene mutation]

OBJECTIVE

To explore the clinical features and genomic abnorm ality of a fetus enlarged multicystic dysplastic kidneys with oligohydramnios caused by NPHP3 gene mutation.

METHODS

The fetuse was found to have multicystic dysplastic kidneys with oligohydramnios upon ultrasonography during the second trimester. Following induced abortion, fetal tissue was collected for the extraction of DNA, chromosomal microarray analysis (CMA) and whole exome sequencing (WES). Sanger sequencing was used to verify the suspected variants in the family.

RESULTS

Antenatal ultrasound examination at 19 weeks showed "polycystic" kidneys with Oligohydramnios. Delivery was by induced labour because of the critically low amniotic fluid volume. Testing of CMA was normal. WES showed a compound heterozygous mutation of c.1817G>A, p.W606X; c.432dupA, p.E145Rfs*18 mutations are novel mutations in this study.

CONCLUSION

The research may further expand the NPHP3 gene mutation spectrum. Enlarged multicystic dysplastic kidneys with oligohydramnios caused by NPHP3 gene mutation at least include one or two splice site mutation, frameshift mutation or nonsense mutation foetal poor prognosis.

Multicystic Dysplastic Kidney and Incontinentia Pigmenti: Coexistence of 2 Rare Diseases

Multicystic dysplastic kidney is a congenital kidney malformation consisting of multiple cysts of various sizes without a normal kidney morphology. Incontinentia pigmenti is a rare X-linked dominant genodermatosis, which is usually lethal in males, that presents clinically in 4 stages. Here, we report a case of multicystic dysplastic kidney with ureterovesical junction obstruction and incontinentia pigmenti. Coexistence of these two rare diseases may be a coincidental phenomenon or an association between the two may exist.

Prospective Evaluation of Kidney Disease in Joubert Syndrome

BACKGROUND AND OBJECTIVES

Joubert syndrome is a genetically heterogeneous ciliopathy associated with >30 genes. The characteristics of kidney disease and genotype-phenotype correlations have not been evaluated in a large cohort at a single center.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We evaluated 97 individuals with Joubert syndrome at the National Institutes of Health Clinical Center using abdominal ultrasonography, blood and urine chemistries, and DNA sequencing.

RESULTS

Patients were ages 0.6-36 years old (mean of 9.0±7.6 years old); 41 were female. Mutations were identified in 19 genes in 92 patients; two thirds of the mutations resided in six genes: TMEM67, C5orf42, CC2D2A, CEP290, AHI1, and KIAA0586. Kidney disease was detected in 30%, most commonly in association with the following genes: CEP290 (six of six), TMEM67 (11 of 22), and AHI1 (three of six). No kidney disease was identified in patients with mutations in C5orf42 (zero of 15) or KIAA0586 (zero of six). Prenatal ultrasonography of kidneys was normal in 72% of patients with kidney disease. Specific types of kidney disease included nephronophthisis (31%), an overlap phenotype of autosomal recessive polycystic kidney disease/nephronophthisis (35%), unilateral multicystic dysplastic kidney (10%), and indeterminate-type cystic kidney disease (24%). Early-onset hypertension occurred in 24% of patients with kidney disease. Age at ESRD (n=13) ranged from 6 to 24 years old (mean of 11.3±4.8 years old).

CONCLUSIONS

Kidney disease occurs in up to one third of patients with Joubert syndrome, most commonly in those with mutations in CEP290, TMEM67, and AHI1. Patients with mutations in C5orf42 or KIAA0586 are less likely to develop kidney disease. Prenatal ultrasonography is a poor predictor of kidney involvement in Joubert syndrome. Unilateral multicystic dysplastic kidney and autosomal recessive polycystic kidney disease-like enlarged kidneys with early-onset hypertension can be part of the Joubert syndrome kidney phenotype.

Detection of recurrent transmission of 17q12 microdeletion by array comparative genomic hybridization in a fetus with prenatally diagnosed hydronephrosis, hydroureter, and multicystic kidney, and variable clinical spectrum in the family

OBJECTIVE

This study was aimed at detection of recurrent transmission of the 17q12 microdeletion in a fetus with congenital anomalies of the kidney and urinary tract.

MATERIALS AND METHODS

A 35-year-old woman was referred to the hospital at 20 weeks' gestation because of hydronephrosis in the fetus. The mother was normal and healthy. Her second child was a girl who had bilateral dysplastic kidneys that required hemodialysis, and died at the age of 5 years. During this pregnancy, the woman underwent amniocentesis at 18 weeks' gestation because of advanced maternal age. Cytogenetic analysis revealed a karyotype of 46,XY. Prenatal ultrasound showed left hydronephrosis with a tortuous ureter, right hydronephrosis, and increased echogenicity of the kidneys. Fetal magnetic resonance imaging showed right dilated renal calyces, left hydronephrosis, hydroureter, and multicystic kidney. The pregnancy was subsequently terminated. Array comparative genomic hybridization (aCGH) and fluorescence in situ hybridization were applied for genetic analysis using umbilical cord, maternal blood, and cultured amniocytes.

RESULTS

aCGH analysis on umbilical cord detected a 1.75-Mb deletion at 17q12 including haploinsufficiency of LHX1 and HNF1B. aCGH analysis on maternal blood detected a 1.54-Mb deletion at 17q12 including haploinsufficiency of LHX1 and HNF1B. Metaphase fluorescence in situ hybridization analysis on cultured amniocytes and maternal blood lymphocytes using 17q12-specific bacterial artificial chromosome probe showed 17q12 microdeletion in the fetus and the mother.

CONCLUSION

Prenatal diagnosis of recurrent renal and urinary tract abnormalities in the fetus should include a differential diagnosis of familial 17q12 microdeletion.

GATA3 mutation in a family with hypoparathyroidism, deafness and renal dysplasia syndrome

BACKGROUND

The hypoparathyroidism, deafness and renal dysplasia (HDR) syndrome is an autosomal dominant disorder primarily caused by GATA3 gene mutation. We report here a case that both of a Chinese boy and his father had HDR syndrome which caused by a novel mutation of GATA3.

METHODS

Polymerase chain reaction and DNA sequencing was performed to detect the exons of the GATA3 gene for mutation analysis.

RESULTS

Sequence analysis of GATA3 revealed a heterozygous nonsense mutation in this family: a mutation of GATA3 at exon 2 (c.515C >A) that resulted in a premature stop at codon 172 (p.S172X) with a loss of two zinc finger domains.

CONCLUSION

We identified a novel nonsense mutation which will expand the spectrum of HDR-associated GATA3 mutations.

Ultrasound diagnosis of central nervous system anomalies (bifid choroid plexus, ventriculomegaly, Dandy-Walker malformation) associated with multicystic dysplastic kidney disease in a trisomy 9 fetus: case report with literature review

Trisomy 9 is a lethal chromosomal abnormality that rarely progresses beyond the second trimester of pregnancy. Multiple central nervous system anomalies, including bifid choroid plexus, ventriculomegaly, and Dandy-Walker malformation, associated with multicystic dysplastic kidney disease in a trisomy 9 fetus are reported. The prenatal ultrasound diagnosis has been aided by novel three-dimensional ultrasound software.

Pleiotropic effects of CEP290 (NPHP6) mutations extend to Meckel syndrome

Meckel syndrome (MKS) is a rare autosomal recessive lethal condition characterized by central nervous system malformations, polydactyly, multicystic kidney dysplasia, and ductal changes of the liver. Three loci have been mapped (MKS1-MKS3), and two genes have been identified (MKS1/FLJ20345 and MKS3/TMEM67), whereas the gene at the MKS2 locus remains unknown. To identify new MKS loci, a genomewide linkage scan was performed using 10-cM-resolution microsatellite markers in eight families. The highest heterogeneity LOD score was obtained for chromosome 12, in an interval containing CEP290, a gene recently identified as causative of Joubert syndrome (JS) and isolated Leber congenital amaurosis. In view of our recent findings of allelism, at the MKS3 locus, between these two disorders, CEP290 was considered a candidate, and homozygous or compound heterozygous truncating mutations were identified in four families. Sequencing of additional cases identified CEP290 mutations in two fetuses with MKS and in four families presenting a cerebro-reno-digital syndrome, with a phenotype overlapping MKS and JS, further demonstrating that MKS and JS can be variable expressions of the same ciliopathy. These data identify a fourth locus for MKS (MKS4) and the CEP290 gene as responsible for MKS.

Renal dysplasia unrelated to claudin-16 deficiency in Japanese Black cattle

Renal lesions of the type usually found in claudin-16 (CL-16) defective Japanese Black cattle (homozygous for CL-16 deficiency) were identified in six animals of this breed, aged 28-59 months, which were either heterozygous for CL-16 deficiency (type 1) or normal, as judged by a DNA-based test associated with the CL-16 gene. Histopathologically, all six cases showed elongated focal lesions which ran through the cortex to terminate in the outer zone of the medulla. The lesions contained components that included: (1) immature tubules, (2) small irregularly shaped tubules with thickening of the basement membrane, (3) mesenchymal cells in an increased interstitium, (4) small atrophic glomeruli, and (5) immature glomeruli. The glomeruli were noticeably reduced in number, and large glomeruli with an increased number of mesangial cells were observed throughout the entire cortical area. Cystic dilation of tubules and flattening of the epithelium were noted in all areas of the kidney. Histopathologically, the renal lesions in the six cases were indistinguishable from those reported previously in cattle homozygous for CL-16 deficiency. These findings demonstrate that such renal lesions in Japanese Black cattle are not necessarily associated with homozygous deletion of the CL-16 gene.

Embryology and genetics of primary vesico-ureteric reflux and associated renal dysplasia

Congenital anomalies of the kidney and urinary tract, as well as primary vesico-ureteric reflux (VUR) and associated renal dysplasia, are the most relevant causes of end-stage renal failure in the pediatric population. In vivo and in vitro experimental studies have allowed the identification of several genes involved both in ureteric bud branching, ureteric elongation and insertion into the bladder, and in nephrogenesis. It has been proposed that both renal and ureteral abnormalities, as well as the associated renal hypo-dysplasia, may derive from a common mechanism as the result of a dysregulation of the normal developmental program. The large homologies between mice and the human genome suggest that the same genes could be involved both in rodent and human VUR. Furthermore, epidemiological observations suggest that not only syndromic but also isolated VUR is an inherited trait. Linkage analysis for homologous mouse genes in humans, genome-wide linkage studies in multigenerational families and association studies by polymorphisms support the hypothesis that VUR is genetically heterogeneous and is caused by a number of different genes acting with random environmental effects. The present teaching paper is an overview of the embryology and genetics of primary VUR and associated congenital reflux nephropathy.

Characteristics of Hearing Loss in HDR (Hypoparathyroidism, Sensorineural Deafness, Renal Dysplasia) Syndrome

Haploinsufficiency of the zinc finger transcription factor GATA3 causes the triad of hypoparathyroidism, deafness and renal dysplasia, known by its acronym HDR syndrome. The purpose of the current study was to describe in detail the auditory phenotype in human HDR patients and compare these to audiometrical and histological data previously described in a mouse model of this disease. Pure tone audiometry, speech audiometry, speech in noise, auditory brainstem responses and transiently evoked otoacoustic emissions were measured in 2 patients affected by HDR syndrome. Both patients were affected by a moderate-to-severe sensorineural hearing loss. Speech reception thresholds were shifted and speech recognition in noise was disturbed. No otoacoustic emissions could be generated in either patient. Auditory brainstem response interpeak intervals were normal. The human and murine audiological phenotypes seem to correspond well. Hearing loss in HDR syndrome is moderate to severe, seems to be slightly worse at the higher end of the frequency spectrum and may be progressive with age. The absence of otoacoustic emissions and the loss of frequency selectivity suggest an important role for outer hair cells in causing the hearing loss.

Prevalence of mutations in renal developmental genes in children with renal hypodysplasia: results of the ESCAPE study

Renal hypodysplasia (RHD) is characterized by a reduced nephron number, small kidney size, and disorganized renal tissue. A hereditary basis has been established for a subset of affected patients, suggesting a major role of developmental genes that are involved in early kidney organogenesis. Gene mutations that have dominant inheritance and cause RHD, urinary tract anomalies, and defined extrarenal symptoms have been identified in TCF2 (renal cysts and diabetes syndrome), PAX2 (renal-coloboma syndrome), EYA1 and SIX1 (branchio-oto-renal syndrome), and SALL1 (Townes-Brocks syndrome). For estimation of the prevalence of these events, an unselected cohort of 99 unrelated patients with RHD that was associated with chronic renal insufficiency were screened for mutations in TCF2, PAX2, EYA1, SIX1, and SALL1. Mutations or variants in the genes of interest were detected in 17 (17%) unrelated families: One mutation, two variants, and four deletions of TCF2 in eight unrelated patients; four different PAX2 mutations in six families; one EYA1 mutation and one deletion in two patients with branchio-oto-renal syndrome; and one SALL1 mutation in a patient with isolated RHD. Of a total of 27 patients with renal cysts, six (22%) carried a mutation in TCF2. It is interesting that a SIX1 sequence variant was identified in two siblings with renal-coloboma syndrome as a result of a PAX2 mutation, suggesting an oligogenic inheritance. Careful clinical reevaluation that focused on discrete extrarenal symptoms and thorough family analysis revealed syndrome-specific features in nine of the 17 patients. In conclusion, 15% of patients with RHD show mutations in TCF2 or PAX2, whereas abnormalities in EYA1, SALL1, and SIX1 are less frequent.

Severe pancreas hypoplasia and multicystic renal dysplasia in two human fetuses carrying novel HNF1beta/MODY5 mutations

Heterozygous mutations in the HNF1beta/vHNF1/TCF2 gene cause maturity-onset diabetes of the young (MODY5), associated with severe renal disease and abnormal genital tract. Here, we characterize two fetuses, a 27-week male and a 31.5-week female, carrying novel mutations in exons 2 and 7 of HNF1beta, respectively. Although these mutations were predicted to have different functional consequences, both fetuses displayed highly similar phenotypes. They presented one of the most severe phenotypes described in HNF1beta carriers: bilateral enlarged polycystic kidneys, severe pancreas hypoplasia and abnormal genital tract. Consistent with this, we detected high levels of HNF1beta transcripts in 8-week human embryos in the mesonephros and metanephric kidney and in the epithelium of pancreas. Renal histology and immunohistochemistry analyses of mutant fetuses revealed cysts derived from all nephron segments with multilayered epithelia and dysplastic regions, accompanied by a marked increase in the expression of beta-catenin and E-cadherin. A significant proportion of cysts still expressed the cystic renal disease proteins, polycystin-1, polycystin-2, fibrocystin and uromodulin, implying that cyst formation may result from a deregulation of cell-cell adhesion and/or the Wnt/beta-catenin signaling pathway. Both fetuses exhibited a severe pancreatic hypoplasia with underdeveloped and disorganized acini, together with an absence of ventral pancreatic-derived tissue. beta-catenin and E-cadherin were strongly downregulated in the exocrine and endocrine compartments, and the islets lacked the transporter essential for glucose-sensing GLUT2, indicating a beta-cell maturation defect. This study provides evidence of differential gene-dosage requirements for HNF1beta in normal human kidney and pancreas differentiation and increases our understanding of the etiology of MODY5 disorder.

Mutations in Uroplakin IIIA are a rare cause of renal hypodysplasia in humans

BACKGROUND

Renal hypodysplasia, characterized by a decrease in nephron number, small overall kidney size, and maldeveloped renal tissue, is a leading cause of chronic renal failure in young children. Familial clustering and renal hypodysplasia phenotypes observed in transgenic animal models suggest a genetic contribution. Uroplakin IIIa (encoded by UPIIIA) is an integral membrane protein present in urothelial plaques, and the murine UPIIIa knockout is associated with urothelial anomalies and vesicoureteral reflux. De novo UPIIIA mutations recently were identified in 4 of 17 patients with severe bilateral renal adysplasia.

METHODS

To evaluate the overall role of UPIIIA in human renal hypodysplasia pathogenesis, we performed UPIIIA mutation analysis in a cohort of 170 pediatric patients affected by severe unilateral or bilateral renal hypodysplasia. Eighty-one patients were affected by bilateral nonobstructive renal hypodysplasia; of these, 61 were without vesicoureteral reflux. Eighty-four patients presented with unilateral nonobstructive renal hypodysplasia, including 24 patients with unilateral multicystic dysplastic kidneys. Family history was positive in 11%.

RESULTS

Mutation analysis showed 2 heterozygous mutations not observed in 200 race-matched control chromosomes. In only 1 family was distribution of the UPIIIA mutation consistent with a disease-causing effect. This de novo missense mutation (Gly202Asp) was identified in a patient with unilateral multicystic dysplastic kidneys. The second (intronically located) mutation appeared unlikely to be disease causing because it did not segregate with an obvious disease phenotype in the affected family.

CONCLUSION

Our results indicate that de novo mutations in UPIIIA can be involved in defective early kidney development, but probably constitute only a rare cause of human renal hypodysplasia in a minor subset of individuals.

Spectrum of pediatric developmental and genetic renal lesions and associated congenital malformations--an autopsy study from north India

Pediatric developmental and genetic renal lesions are a known cause of mortality in the perinatal/neonatal period. These lesions are associated with a wide range of extrarenal congenital malformations that influence the outcome of the patients. In this autopsy study, we have analyzed the spectrum of pediatric developmental and genetic renal lesions and their associated congenital malformations. A total of 4,099 autopsies (20 weeks of gestation to 1 year of life) were reviewed, of which 158 cases (3.85%) of pediatric developmental (143 cases) and genetic renal lesions (15 cases) were found. Autosomal recessive polycystic kidney disease was the commonest genetic lesion. Primitive ducts with cuffing of immature mesenchyme--the sine qua non of renal dysplasia--was found in all cases of dysplasia. Associated congenital malformations were seen in all cases and thus a thorough search for them is mandatory. Ductal plate malformation was found in all cases of autosomal recessive polycystic kidney disease and in 1 case of bilateral multicystic dysplasia.

FGFR3 mutation in thanatophoric dysplasia type 1 with bilateral cystic renal dysplasia: coincidence or a new association?

Thanatophoric dysplasia (TD) is a lethal dwarfism condition due to missense mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. Examination of TD patients reveals mainly the involvement of the skeletal system and the brain, but also renal and cardiovascular anomalies have been described. We report the prenatal detection of TD type 1 (TD1) associated with bilateral cystic renal dysplasia (CRD) Potter's type II, in which the molecular analysis reveals the typical Arg248Cys substitution in the FGFR3 gene. CRD has not been previously described in TD or other conditions due to FGFR3 mutations, but occurs in Apert syndrome (due to FGFR2 mutations). The possible involvement of renal developmental defect in FGFR3 mutations is discussed.

Implication of genetic variations in congenital obstructive nephropathy

The renin-angiotensin system (RAS) has long been implicated in kidney development, and it has been reported that disruption of angiotensin type 2 receptor (AGTR2) results in a wide range of congenital anomalies of the kidney and urinary tract. We investigated the allele frequencies of the AGTR2 and other RAS genes in Korean patients with ureteropelvic junction obstruction, multicystic dysplastic kidney (MCDK), and unilateral renal agenesis (RA). Fifty-three Korean children were enrolled: 37 boys and 16 girls, 27 with hydronephrosis, 23 with MCDK, and 3 with RA. Among 100 healthy Koreans, the frequencies of A and G alleles at the A-G transition site of intron 1 of the AGTR2 gene were 70% (140/200) and 30% (60/200), respectively. In the patient group, the A allele frequency was 57% (60/106) and the G allele frequency was 43% (46/106), significantly higher than in the general population (P=0.024). There was no significant difference of allele frequency between boys and girls. Angiotensin-converting enzyme insertion/deletion, angiotensinogen M235T, and the angiotensin 2 type 1 receptor A1166C genotype distribution showed no difference from those of the control subjects. These findings indicate that the AGTR2 gene may play a major role in the development of congenital obstructive nephropathy.

A familial case of multicystic dysplastic kidney

A familial case of multicystic dysplastic kidney (MCDK) is described. The proband is a one-year-old boy with left MCDK, and his father was also revealed to have unilateral MCDK. The mother had two abortions; the second pregnancy was terminated because of bilateral MCDK of the fetus (Potter anomaly). The two patients and the aborted male fetus did not have any malformations except for MCDK. Thus in this family MCDK occurs as an isolated phenomenon in three individuals within two generations, presumably as a result of autosomal dominant inheritance.

GATA3 haploinsufficiency causes a rapid deterioration of distortion product otoacoustic emissions (DPOAEs) in mice

Human HDR (hypoparathyroidism, deafness and renal dysplasia)-syndrome is caused by haploinsufficiency of zinc-finger transcription factor GATA3. The hearing loss due to GATA3 haploinsufficiency has been shown to be peripheral in origin, but it is unclear to what extent potential aberrations in the outer hair cells (OHCs) contribute to this disorder. To further elucidate the pathophysiological mechanism underlying the hearing defect in HDR-syndrome, we investigated the OHCs in heterozygous Gata3-knockout mice at both the functional and morphological level. While the signal-to-noise ratios of distortion product otoacoustic emissions (DPOAE) in wild type mice did not change significantly during the first half-year of live, those in the heterozygous Gata3 mice decreased dramatically. In addition, both light microscopic and transmission electron microscopic analyses showed that the number of OHCs containing vacuoles was increased in the mutants. Together, these findings indicate that outer hair cell malfunctioning plays a major role in the hearing loss in HDR-syndrome.

Refinement of the critical region for MCKD1 by detection of transcontinental haplotype sharing

BACKGROUND

Autosomal-dominant medullary cystic kidney disease type 1 (MCKD1) [OMIM 174000] is a hereditary nephropathy that leads to renal salt wasting and end-stage renal failure at a median age of 62 years. In a Welsh MCKD1 kindred we have recently demonstrated linkage to the MCKD1 locus on chromosome 1q23.1 and refined the critical MCKD1 region to <3.3 Mb.

METHODS

In order to refine the candidate gene region for MCKD1, high-resolution haplotype analysis in three large kindreds with MCKD1 was performed.

RESULTS

We report here on high-resolution haplotype analysis in this Welsh kindred, as well as in the Arizona kindred, which was used for the first definition of MCKD as a disease entity, and in a kindred from the Dutch/German border. We detected extensive haplotype sharing among all affected individuals of all three kindreds. Scrutinization of the genealogy of the Arizona kindred revealed an origin from Germany in the 17th century, thereby providing historical data for haplotype sharing by descent at the MCKD1 locus.

CONCLUSION

Under the hypothesis of haplotype sharing by descent, we refined the critical genetic interval to <650 kb, thus enabling candidate gene analysis.

Reduced renin expression and altered gene transcript profiles in multicystic dysplastic kidneys

PURPOSE

Some patients with multicystic dysplasia experience hypertension in infancy which can be clinically improved with simple nephrectomy. Little is known of the role of renin in multicystic dysplasia and therefore, we studied renin expression in nonhypertensive multicystic dysplasia and compared it with hypertensive multicystic dysplasia. Additionally, global gene transcript profiles were studied in nonhypertensive multicystic dysplasia.

MATERIALS AND METHODS

Tissue from 12 patients with multicystic dysplasia without hypertension and 2 patients with hypertensive multicystic dysplasia were compared to normal metanephric mid-term and neonatal kidneys. Renin expression was studied by immunohistochemistry. CD-68, a marker for macrophages, was applied to slides previously stained with renin. GeneChip (Affymetrix, Southern Oaks, California) microarray analysis was performed using total RNA from 2 nonhypertensive multicystic dysplastic kidneys and normal newborn kidney as control.

RESULTS

Strong renin staining was present in arteries and arterioles in normal early metanephric kidneys and concentrated in juxtaglomerular cells in neonatal kidneys. Renin was variably decreased in arterioles in multicystic dysplasia and was ectopically expressed in interstitial cells. Renin positive interstitial cells co-expressed CD-68 antigen identifying these cells as macrophages. Ectopic renin production was more pronounced in hypertensive multicystic dysplasia. GeneChip hybridization showed a 60 to 200-fold decrease in expression of renin transcript in multicystic dysplasia relative to normal kidney, concordant with immunohistochemical results. Altered expression of several other candidate transcripts was also identified.

CONCLUSIONS

Dramatic renin decrease in multicystic dysplasia suggests that it may participate in the development of dysplastic vessels. Pronounced ectopic renin expression by macrophages in multicystic dysplasia associated with hypertension may be linked to hypertension in multicystic dysplasia. Several other candidate genes whose altered expression may be associated with the pathophysiology of multicystic dysplasia provide intriguing molecular targets for future study.

A family study and the natural history of prenatally detected unilateral multicystic dysplastic kidney

PURPOSE

We document the inheritance pattern of multicystic dysplastic kidney in 3 affected families and screen first-degree relatives of a cohort of children with prenatally detected multicystic dysplastic kidney for renal anomalies. The study also afforded an opportunity to document the natural history of prenatally detected multicystic dysplastic kidney.

MATERIALS AND METHODS

We identified 3 families during clinical treatment of children with prenatally detected multicystic dysplastic kidneys. Other members of these families were evaluated with renal ultrasonography. For the family screening study index cases were identified from a fetal uropathy database. A total of 94 first-degree relatives (52 parents, 35 full siblings and 7 half siblings) of 29 children with prenatally detected multicystic dysplastic kidneys were studied with urinary tract ultrasonography, blood pressure measurement, urinalysis and plasma biochemistry.

RESULTS

Two families had affected sibling pairs, 1 of which also had a half sibling with vesicoureteral reflux. The third family included 3 individuals with multicystic dysplastic kidney and 1 with renal agenesis thought to have resulted from involution of multicystic dysplastic kidney. This family is consistent with autosomal dominant inheritance with variable expressivity and reduced penetrance. In the screening study ultrasonography did not demonstrate significant renal anomalies in any of the 94 first-degree relatives of the multicystic dysplastic kidney index cases. Followup assessment of prenatally detected multicystic dysplastic kidneys in index cases demonstrated total involution in 52% at a median age of 6.5 years with no multicystic dysplastic kidney related morbidity.

CONCLUSIONS

Multicystic dysplastic kidney can be familial but is most commonly a sporadic anomaly. Formal screening of relatives is not recommended. Followup data on a cohort of children with prenatally detected multicystic dysplastic kidney add further support to conservative management.

Deficiency of phospholipase C-γ1 impairs renal development and hematopoiesis

Phospholipase C-γ1 (PLC-γ1) is involved in a variety of intracellular signaling via many growth factor receptors and T-cell receptor. To explore the role of PLC-γ1 in vivo, we generated the PLC-γ1-deficient (plc-γ1–/–) mice, which died of growth retardation at embryonic day 8.5-9.5 in utero. Therefore, we examined plc-γ1–/– chimeric mice generated with plc-γ1–/– embryonic stem (ES) cells for further study. Pathologically, plc-γ1–/– chimeras showed multicystic kidney due to severe renal dysplasia and renal tube dilation. Flow cytometric analysis and glucose phosphate isomerase assay revealed very few hematopoietic cells derived from the plc-γ1–/– ES cells in the mutant chimeras. However, differentiation of plc-γ1–/– ES cells into erythrocytes and monocytes/macrophages in vitro was observed to a lesser extent compared with control wild-type ES cells. These data suggest that PLC-γ1 plays an essential role in the renal development and hematopoiesis in vivo.

[Potter sequence in a neonate with bilateral renal dysplasia with genetic aspects]

The authors describe a neonate with Potter sequence due to bilateral renal dysplasia and discuss its genetic implications. Although this congenital anomaly of the kidneys may occur sporadically, it is now accepted that this condition has an autosomal dominant inheritance pattern with a penetrance of 50-90% and variable expression. Potter sequence is not compatible with extrauterine life; therefore, in case of maternal oligohydramnios, ultrasound should be performed in the second trimester in order to make a prenatal diagnosis, as well as to permit genetic counseling. As Potter sequence is frequently associated with clinically silent anomalies of the kidneys, ultrasound examination of the kidneys and urinary tract should also be performed in all family members.

Multicystic dysplastic kidney and Kallmann's syndrome: a new association?

BACKGROUND

Kallmann's syndrome is characterized by anosmia and hypogonadotrophic hypogonadism. Radiographic studies of teenagers and older subjects with the X-linked form of the syndrome have shown that up to 40% have an absent kidney unilaterally. Although this has been attributed to renal "agenesis", a condition in which the kidney fails to form, little is known about the appearance of the developing urinary tract either pre- or post-natally in individuals with Kallmann's syndrome.

METHODS

We describe two brothers who had features of Kallmann's syndrome, most probably of the X-linked variety, who both had a major urinary-tract malformation detected before birth.

RESULTS

The brothers were found to have unilateral multicystic dysplastic kidneys on routine antenatal ultrasound scanning and both underwent surgical nephrectomy of these organs post-natally. Immunohistochemical studies on the younger sibling revealed hyperproliferative dysplastic kidney tubules which overexpressed PAX2, a potentially oncogenic transcription factor, and BCL2, a cell-survival factor, surrounded by metaplastic, alpha smooth-muscle actin-positive stroma: similar patterns have been observed in patients with non-syndromic multicystic dysplastic kidneys.

CONCLUSIONS

Our results describe a new type of urinary-tract malformation associated with Kallmann's syndrome. However, since multicystic kidneys tend to involute, only when more Kallmann's syndrome patients are screened in utero or in early childhood using structural renal scans, will it be possible to establish whether multicystic kidney disease is a bona-fide part of the syndrome.

Postnatal development and progression of renal dysplasia in cyclooxygenase-2 null mice

BACKGROUND

Genetic ablation of cyclooxygenase-2 (COX-2) resulted in cystic renal dysplasia and early death in adult mice. The ontologic development of the renal pathology and the biochemical and physiological abnormalities associated with the dysplasia are unknown.

METHODS

Mice homozygous for a targeted deletion of COX-2 (-/-) were compared with wild-type littermates (+/+). Somatic and kidney growth and renal histology were studied at the day of birth and at a number of postnatal ages. Systolic blood pressure, urinalysis, urine osmolality, serum and urine chemistries, and inulin clearance were evaluated in adult animals.

RESULTS

Beginning at postnatal day 10 (PN10), kidney growth was suppressed in -/- animals, while somatic growth and heart growth were unaffected. By PN10, -/- kidneys had thin nephrogenic cortexes and crowded, small, subcapsular glomeruli. The pathology increased with age with progressive outer cortical dysplasia, cystic subcapsular glomeruli, loss of proximal tubular mass, and tubular atrophy and cyst formation. Adult -/- kidneys had profound diffuse tubular cyst formation, outer cortical glomerular hypoplasia and periglomerular fibrosis, inner cortical nephron hypertrophy, and diffuse interstitial fibrosis. The glomerular filtration rate was reduced by more than 50% in -/- animals (6.82 +/- 0.65 mL/min/kg) compared with wild-type controls (14.7 +/- 1.01 mL/min/kg, P < 0. 001). Plasma blood urea nitrogen and creatinine were elevated in null animals compared with controls. Blood pressure, urinalysis, urine osmolality, and other plasma chemistries were unaffected by the deletion of COX-2.

CONCLUSIONS

Deficiency of COX-2 results in progressive and specific renal architectural disruption and functional deterioration beginning in the final phases of nephrogenesis. Tissue-specific and time-dependent expression of COX-2 appears necessary for normal postnatal renal development and the maintenance of normal renal architecture and function.

Renal dysplasia in boxers and Finnish harriers

Puppies from two litters of dogs were found to have severe polyuria and polydipsia. Four of the dogs were investigated by means of clinical examination, haematological and biochemical analysis, and urinalysis. A modified water deprivation response test was also performed in two of the dogs. Renal changes on postmortem examination in three of the dogs were found to be consistent with renal dysplasia. A possible explanation for the finding of hyposthenuria and the extreme polyuria and polydipsia in association with renal dysplasia may be lack of response to antidiuretic hormone owing to anomalous maturation of the renal tubules. Six other puppies from the two litters of dogs did not show any clinical signs of polyuria and polydipsia, although postmortem examination in one of them also revealed renal dysplasia. The clinical features of renal dysplasia may therefore vary greatly between individuals.