Genome-wide association study in patients with posterior urethral valves

Congenital lower urinary tract obstructions (LUTO) are most often caused by posterior urethral valves (PUV), a male limited anatomical obstruction of the urethra affecting 1 in 4,000 male live births. Little is known about the genetic background of PUV. Here, we report the largest genome-wide association study (GWAS) for PUV in 4 cohorts of patients and controls. The final meta-analysis included 756 patients and 4,823 ethnicity matched controls and comprised 5,754,208 variants that were genotyped or imputed and passed quality control in all 4 cohorts. No genome-wide significant locus was identified, but 33 variants showed suggestive significance (P < 1 × 10−5). When considering only loci with multiple variants residing within < 10 kB of each other showing suggestive significance and with the same effect direction in all 4 cohorts, 3 loci comprising a total of 9 variants remained. These loci resided on chromosomes 13, 16, and 20. The present GWAS and meta-analysis is the largest genetic study on PUV performed to date. The fact that no genome-wide significant locus was identified, can be explained by lack of power or may indicate that common variants do not play a major role in the etiology of PUV. Nevertheless, future studies are warranted to replicate and validate the 3 loci that yielded suggestive associations

Long-term renal outcome in children with OCRL mutations: retrospective analysis of a large international cohort

BACKGROUND: Lowe syndrome (LS) and Dent-2 disease (DD2) are disorders associated with mutations in the OCRL gene and characterized by progressive chronic kidney disease (CKD). Here, we aimed to investigate the long-term renal outcome and identify potential determinants of CKD and its progression in children with these tubulopathies. METHODS: Retrospective analyses were conducted of clinical and genetic data in a cohort of 106 boys (LS: 88 and DD2: 18). For genotype-phenotype analysis, we grouped mutations according to their type and localization. To investigate progression of CKD we used survival analysis by Kaplan-Meier method using stage 3 CKD as the end-point. RESULTS: Median estimated glomerular filtration rate (eGFR) was lower in the LS group compared with DD2 (58.8 versus 87.4 mL/min/1.73 m(2), P < 0.01). CKD stage II-V was found in 82% of patients, of these 58% and 28% had moderate-to-severe CKD in LS and DD2, respectively. Three patients (3%), all with LS, developed stage 5 of CKD. Survival analysis showed that LS was also associated with a faster CKD progression than DD2 (P < 0.01). On multivariate analysis, eGFR was dependent only on age (b = -0.46, P < 0.001). Localization, but not type of mutations, tended to correlate with eGFR. There was also no significant association between presence of nephrocalcinosis, hypercalciuria, proteinuria and number of adverse clinical events and CKD. CONCLUSIONS: CKD is commonly found in children with OCRL mutations. CKD progression was strongly related to the underlying diagnosis but did not associate with clinical parameters, such as nephrocalcinosis or proteinuria

Genetic drivers of kidney defects in the digeorge syndrome

BACKGROUND The DiGeorge syndrome, the most common of the microdeletion syndromes, affects multiple organs, including the heart, the nervous system, and the kidney. It is caused by deletions on chromosome 22q11.2; the genetic driver of the kidney defects is unknown. METHODS We conducted a genomewide search for structural variants in two cohorts: 2080 patients with congenital kidney and urinary tract anomalies and 22,094 controls. We performed exome and targeted resequencing in samples obtained from 586 additional patients with congenital kidney anomalies. We also carried out functional studies using zebrafish and mice. RESULTS We identified heterozygous deletions of 22q11.2 in 1.1% of the patients with congenital kidney anomalies and in 0.01% of population controls (odds ratio, 81.5; P = 4.5×1014). We localized the main drivers of renal disease in the DiGeorge syndrome to a 370-kb region containing nine genes. In zebrafish embryos, an induced loss of function in snap29, aifm3, and crkl resulted in renal defects; the loss of crkl alone was sufficient to induce defects. Five of 586 patients with congenital urinary anomalies had newly identified, heterozygous protein-Altering variants, including a premature termination codon, in CRKL. The inactivation of Crkl in the mouse model induced developmental defects similar to those observed in patients with congenital urinary anomalies. CONCLUSIONS We identified a recurrent 370-kb deletion at the 22q11.2 locus as a driver of kidney defects in the DiGeorge syndrome and in sporadic congenital kidney and urinary tract anomalies. Of the nine genes at this locus, SNAP29, AIFM3, and CRKL appear to be critical to the phenotype, with haploinsufficiency of CRKL emerging as the main genetic driver

Genetic Drivers of Kidney Defects in the DiGeorge Syndrome

Background The DiGeorge syndrome, the most common of the microdeletion syndromes, affects multiple organs, including the heart, the nervous system, and the kidney. It is caused by deletions on chromosome 22q11.2; the genetic driver of the kidney defects is unknown. Methods We conducted a genomewide search for structural variants in two cohorts: 2080 patients with congenital kidney and urinary tract anomalies and 22,094 controls. We performed exome and targeted resequencing in samples obtained from 586 additional patients with congenital kidney anomalies. We also carried out functional studies using zebrafish and mice. Results We identified heterozygous deletions of 22q11.2 in 1.1% of the patients with congenital kidney anomalies and in 0.01% of population controls (odds ratio, 81.5; P=4.5×10(-14)). We localized the main drivers of renal disease in the DiGeorge syndrome to a 370-kb region containing nine genes. In zebrafish embryos, an induced loss of function in snap29, aifm3, and crkl resulted in renal defects; the loss of crkl alone was sufficient to induce defects. Five of 586 patients with congenital urinary anomalies had newly identified, heterozygous protein-altering variants, including a premature termination codon, in CRKL. The inactivation of Crkl in the mouse model induced developmental defects similar to those observed in patients with congenital urinary anomalies. Conclusions We identified a recurrent 370-kb deletion at the 22q11.2 locus as a driver of kidney defects in the DiGeorge syndrome and in sporadic congenital kidney and urinary tract anomalies. Of the nine genes at this locus, SNAP29, AIFM3, and CRKL appear to be critical to the phenotype, with haploinsufficiency of CRKL emerging as the main genetic driver. (Funded by the National Institutes of Health and others.)

Rare variants in BNC2 are implicated in autosomal-dominant congenital lower urinary-tract obstruction

Congenital lower urinary-tract obstruction (LUTO) is caused by anatomical blockage of the bladder outflow tract or by functional impairment of urinary voiding. About three out of 10,000 pregnancies are affected. Although several monogenic causes of functional obstruction have been defined, it is unknown whether congenital LUTO caused by anatomical blockage has a monogenic cause. Exome sequencing in a family with four affected individuals with anatomical blockage of the urethra identified a rare nonsense variant (c.2557C>T [p.Arg853(∗)]) in BNC2, encoding basonuclin 2, tracking with LUTO over three generations. Re-sequencing BNC2 in 697 individuals with LUTO revealed three further independent missense variants in three unrelated families. In human and mouse embryogenesis, basonuclin 2 was detected in lower urinary-tract rudiments. In zebrafish embryos, bnc2 was expressed in the pronephric duct and cloaca, analogs of the mammalian lower urinary tract. Experimental knockdown of Bnc2 in zebrafish caused pronephric-outlet obstruction and cloacal dilatation, phenocopying human congenital LUTO. Collectively, these results support the conclusion that variants in BNC2 are strongly implicated in LUTO etiology as a result of anatomical blockage

Ramipril and Risk of Hyperkalemia in Chronic Hemodialysis Patients

Angiotensin converting enzyme (ACE) inhibitors provide well known cardiorenal-protective benefits added to antihypertensive effects in chronic renal disease. These agents are underused in management of patients receiving hemodialysis (HD) because of common concern of hyperkalemia. However, few studies have investigated effect of renin angiotensin aldosterone system (RAAS) blockade on serum potassium in hemodialysis patients. We assessed the safety of ramipril in patients on maintenance HD. We enrolled 28 adult end stage renal disease (ESRD) patients treated by maintenance HD and prescribed them ramipril in doses of 1.25 to 5 mg per day. They underwent serum potassium concentration measurements before ramipril introduction and in 1 to 3 months afterwards. No significant increase in kalemia was found. Results of our study encourage the use of ACE inhibitors in chronically hemodialyzed patients, but close potassium monitoring is mandatory

The oculocerebrorenal syndrome of Lowe – diagnostic and therapeutic problems in Polish health care system

Zespół oczno-mózgowo-nerkowy, opisany po raz pierwszy przez Lowe’a w 1952 roku, jest rzadkim defektem genetycznym (częstość 1 : 500 000), wywołanym mutacją w genie OCRL kodującym enzym 5-fosfatazę 4,5-dwufosfo-fosfatydyloinozytolu. Jest on zlokalizowany na chromosomie X (Xq25-26), a choroba dziedziczy się w sposób recesywny sprzężony z płcią. Typowymi objawami są: wrodzona zaćma, upośledzenie rozwoju umysłowego i tubulopatia proksymalna (wtórny zespół Fanconiego bez glukozurii) z wolno postępującym upośledzeniem czynności nerek, aż do schyłkowej ich niewydolności w 2–4 dekadzie życia. Inne objawy to: zaburzenia wzrastania, jaskra, woloocze, hipotonia mięśniowa, opóźnienie rozwoju motorycznego, dziwne zachowania (napady agresji i złości, ruchy mimowolne), wentrykulomegalia, przykurcze, artropatie, osteopenia, wnętrostwo, dysplazja zębów, torbiele skórne i skaza krwotoczna. Rozpoznanie wstępne można postawić na podstawie obrazu klinicznego z typową sekwencją pojawiania się objawów, z których początkowymi są zaćma, hipotonia z brakiem odruchów głębokich i białkomocz cewkowy. Potwierdzenie diagnozy stanowi badanie genetyczne, w którym stwierdza się jeden z ponad 200 znanych wariantów genu OCRL lub mutację de novo. Przedstawiono przypadek 2-letniego chłopca z obrazem klinicznym zespołu Lowe’a (wrodzona zaćma, hipotonia, opóźnienie rozwoju psychofizycznego i tubulopatia), diagnozowanego i leczonego w wielu ośrodkach. Po przekazaniu chorego pod opiekę powiatowego oddziału pediatrycznego w Międzyrzeczu rozpoznanie potwierdzono badaniem genetycznym, w którym wykazano hemizygotyczną punktową mutację w eksonie 13 OCRL (c.1351G > A); badanie wykonano dzięki uprzejmości prof. Michaela Ludwiga w Laboratorium Biologii Molekularnej Uniwersytetu w Bonn. Zwrócono uwagę na celowość wczesnego zgłaszania chorych z podejrzeniem zespołu Lowe’a do krajowego rejestru POLtube, co ułatwia dostęp do diagnostyki molekularnej.The oculocerebrorenal syndrome described by C.U. Lowe in 1952 is a rare genetic defect (prevalence 1:500 000) caused by mutation of the OCRL gene which encodes phosphatidylinositol 4,5-bisphosphate 5-phosphatase. Its location on chromosome X (Xq25-26) leads to an X-linked recessive mode of inheritance. A typical clinical triad characterizing the disease consists of congenital cataract, mental retardation and proximal tubulopathy (secondary Fanconi syndrome without glycosuria) with slow progression to end stage kidney disease in the 2nd–4th decade. There are many other symptoms reported like: growth retardation, glaucoma, buphthalmos, muscle hypotonia, neuromotor retardation, behavioral abnormalities (aggression, temper tantrums, repetitive purposeless movements), ventriculomegaly, contractures, arthropathy, osteopenia, cryptorchidism, dental anomalies, skin cysts and bleeding disorders. Preliminary diagnosis may be based on the clinical picture with a typical sequence of symptoms starting from cataracts, hypotonia with a lack of deep tendon reflexes and tubular proteinuria. Final identification of the disease is confirmed by molecular testing with one out of more than 200 known mutations (or de novo variant) found. Here we reported a 2-year-old boy with the clinical picture of Lowe syndrome (congenital cataract, hypotonia, psychomotor development retardation and tubulopathy), examined and treated in many medical centers. The final diagnosis was confirmed by genetic testing planned in the regional hospital in Międzyrzecz and performed by prof. Michael Ludwig from the Laboratory of Molecular Biology at University of Bonn, Germany. A single hemizygous deviation in exon 13 (c.1351G > A) was found. Attention was paid to the purpose of early notification of such patients to the national registry POLtube which facilitates molecular diagnosis

The oculocerebrorenal syndrome of Lowe – diagnostic and therapeutic problems in Polish health care system

Zespół oczno-mózgowo-nerkowy, opisany po raz pierwszy przez Lowe’a w 1952 roku, jest rzadkim defektem genetycznym (częstość 1 : 500 000), wywołanym mutacją w genie OCRL kodującym enzym 5-fosfatazę 4,5-dwufosfo-fosfatydyloinozytolu. Jest on zlokalizowany na chromosomie X (Xq25-26), a choroba dziedziczy się w sposób recesywny sprzężony z płcią. Typowymi objawami są: wrodzona zaćma, upośledzenie rozwoju umysłowego i tubulopatia proksymalna (wtórny zespół Fanconiego bez glukozurii) z wolno postępującym upośledzeniem czynności nerek, aż do schyłkowej ich niewydolności w 2–4 dekadzie życia. Inne objawy to: zaburzenia wzrastania, jaskra, woloocze, hipotonia mięśniowa, opóźnienie rozwoju motorycznego, dziwne zachowania (napady agresji i złości, ruchy mimowolne), wentrykulomegalia, przykurcze, artropatie, osteopenia, wnętrostwo, dysplazja zębów, torbiele skórne i skaza krwotoczna. Rozpoznanie wstępne można postawić na podstawie obrazu klinicznego z typową sekwencją pojawiania się objawów, z których początkowymi są zaćma, hipotonia z brakiem odruchów głębokich i białkomocz cewkowy. Potwierdzenie diagnozy stanowi badanie genetyczne, w którym stwierdza się jeden z ponad 200 znanych wariantów genu OCRL lub mutację de novo. Przedstawiono przypadek 2-letniego chłopca z obrazem klinicznym zespołu Lowe’a (wrodzona zaćma, hipotonia, opóźnienie rozwoju psychofizycznego i tubulopatia), diagnozowanego i leczonego w wielu ośrodkach. Po przekazaniu chorego pod opiekę powiatowego oddziału pediatrycznego w Międzyrzeczu rozpoznanie potwierdzono badaniem genetycznym, w którym wykazano hemizygotyczną punktową mutację w eksonie 13 OCRL (c.1351G > A); badanie wykonano dzięki uprzejmości prof. Michaela Ludwiga w Laboratorium Biologii Molekularnej Uniwersytetu w Bonn. Zwrócono uwagę na celowość wczesnego zgłaszania chorych z podejrzeniem zespołu Lowe’a do krajowego rejestru POLtube, co ułatwia dostęp do diagnostyki molekularnej.The oculocerebrorenal syndrome described by C.U. Lowe in 1952 is a rare genetic defect (prevalence 1:500 000) caused by mutation of the OCRL gene which encodes phosphatidylinositol 4,5-bisphosphate 5-phosphatase. Its location on chromosome X (Xq25-26) leads to an X-linked recessive mode of inheritance. A typical clinical triad characterizing the disease consists of congenital cataract, mental retardation and proximal tubulopathy (secondary Fanconi syndrome without glycosuria) with slow progression to end stage kidney disease in the 2nd–4th decade. There are many other symptoms reported like: growth retardation, glaucoma, buphthalmos, muscle hypotonia, neuromotor retardation, behavioral abnormalities (aggression, temper tantrums, repetitive purposeless movements), ventriculomegaly, contractures, arthropathy, osteopenia, cryptorchidism, dental anomalies, skin cysts and bleeding disorders. Preliminary diagnosis may be based on the clinical picture with a typical sequence of symptoms starting from cataracts, hypotonia with a lack of deep tendon reflexes and tubular proteinuria. Final identification of the disease is confirmed by molecular testing with one out of more than 200 known mutations (or de novo variant) found. Here we reported a 2-year-old boy with the clinical picture of Lowe syndrome (congenital cataract, hypotonia, psychomotor development retardation and tubulopathy), examined and treated in many medical centers. The final diagnosis was confirmed by genetic testing planned in the regional hospital in Międzyrzecz and performed by prof. Michael Ludwig from the Laboratory of Molecular Biology at University of Bonn, Germany. A single hemizygous deviation in exon 13 (c.1351G > A) was found. Attention was paid to the purpose of early notification of such patients to the national registry POLtube which facilitates molecular diagnosis

Characterization of 28 novel patients expands the mutational and phenotypic spectrum of Lowe syndrome

BACKGROUND The oculocerebrorenal syndrome of Lowe (OCRL) is a rare X-linked multi-systemic disorder, almost always characterized by the triad of congenital cataract, cognitive and behavioral impairment and a proximal tubulopathy. METHODS Twenty-eight novel patients with suspected Lowe syndrome were studied. RESULTS All patients carried OCRL gene defects with mutational hot spots at CpG dinucleotides. Mutations previously unknown in Lowe syndrome were observed in ten of the 28 patients, and carriership was identified in 30.4 % of the mothers investigated. Mapping the exact breakpoints of a complete OCRL gene deletion revealed involvement of several flanking repeat elements. We noted a similar pattern of documented clinically relevant symptoms, and even though the patient cohort comprised relatively young patients, 32 % of these patients already showed advanced chronic kidney disease. Thrombocytopenia was seen in several patients, and hyperosmia and/or hyperacusis were reported recurrently. A p.Asp523Asn mutation in a Polish patient, associated with the typical cerebrorenal spectrum but with late cataract (10 year), was also evident in two milder affected Italian brothers with ocular involvement of similar progression. CONCLUSIONS We have identified clinical features in 28 patients with suspected Lowe syndrome that had not been recognized in Lowe syndrome prior to our study. We also provide further evidence that OCRL mutations cause a phenotypic continuum with selective and/or time-dependent organ involvement. At least some of these mutants might exhibit a genotype-phenotype correlation