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Altres ajuts: Fundación Renal Íñigo Álvarez de Toledo (FRIAT) A significant percentage of adults (10%) and children (20%) on renal replacement therapy have an inherited kidney disease (IKD). The new genomic era, ushered in by the next generation sequencing techniques, has contributed to the identification of new genes and facilitated the genetic diagnosis of the highly heterogeneous IKDs. Consequently, it has also allowed the reclassification of diseases and has broadened the phenotypic spectrum of many classical IKDs. Various genetic, epigenetic and environmental factors may explain 'atypical' phenotypes. In this article, we examine different mechanisms that may contribute to phenotypic variability and also provide case examples that illustrate them. The aim of the article is to raise awareness, among nephrologists and geneticists, of rare presentations that IKDs may show, to facilitate diagnosis.

Background Galloway-Mowat syndrome (GAMOS) is a rare autosomal recessive disorder characterized by early-onset nephrotic syndrome and microcephaly with brain anomalies. WDR73 pathogenic variants were described as the first genetic cause of GAMOS and, very recently, four novel causative genes, OSGEP, LAGE3, TP53RK, and TPRKB, have been identified. Case presentation We present the clinical and genetic characteristics of two unrelated infants with clinical suspicion of GAMOS who were born from consanguineous parents. Both patients showed a similar clinical presentation, with early-onset nephrotic syndrome, microcephaly, brain atrophy, developmental delay, axial hypotonia, and early fatality. We identified two novel likely disease-causing variants in the OSGEP gene. These two cases, in conjunction with the findings of a literature review, indicate that OSGEP pathogenic variants are associated with an earlier onset of nephrotic syndrome and shorter life expectancy than WDR73 pathogenic variants. Conclusions Our findings expand the spectrum of pathogenic variants in the OSGEP gene and, taken in conjunction with the results of the literature review, suggest that the OSGEP gene should be considered the main known monogenic cause of GAMOS. Early genetic diagnosis of GAMOS is of paramount importance for genetic counseling and family planning.

Resumen Presentamos el caso de un varón de 32 años, con síndrome de genes contiguos TSC2/PKD1, que le ocasiona esclerosis tuberosa (ET) y poliquistosis renal autosómica dominante simultáneamente. Evolucionó a enfermedad renal terminal y se realizó trasplante renal a los 12 años. Los riñones presentaban angiomiolipomas (AML), que son tumores benignos frecuentes en pacientes con ET. A los 17 años postrasplante, presentó un cuadro de dolor abdominal, anemización y hematoma retroperitoneal. Dicho hematoma se produjo por el sangrado de los AML. Como tratamiento se realizó embolización selectiva. Nuestro paciente podría haberse beneficiado en el momento del trasplante renal del tratamiento con inhibidores de mTOR. Este fármaco actúa como inmunosupresor y reductor tumoral en la ET, al disminuir el riesgo de rotura y hemorragia. En este paciente no se administró porque cuando se trasplantó no se conocía la relación de los inhibidores de mTOR con la ET. Este caso confirma que, a pesar de tratarse de pacientes trasplantados o en diálisis, el riesgo de sangrado por los AML persiste, por lo cual se propone realizar controles periódicos de los riñones propios y valorar la nefrectomía. Abstract We report the case of a 32-year-old male diagnosed with TSC2/PKD1 contiguous gene syndrome, presenting with tuberous sclerosis (TS) and autosomal dominant polycystic kidney disease simultaneously. He progressed to end-stage renal disease and received a kidney transplant at the age of 12. The native kidneys presented angiomyolipomas (AML), which are common benign tumours in patients with TS. Seventeen years after transplantation, he presented with abdominal pain, anaemia and a retroperitoneal haematoma, the latter caused by renal AML bleeding. Selective embolisation was performed. Our patient could have benefited from the administration of mTOR inhibitors at transplant. This therapy is immunosuppressive and reduces the size of benign tumours in TS as well as the risk of rupture and bleeding. This patient did not receive mTOR inhibitors at the time of the transplant because the relationship between mTOR inhibitors and TS was unknown at that time. This case confirms the persistent risk of renal AML bleeding for both transplanted patients and patients on dialysis. As a result, we would recommend routine check-ups of native kidneys and nephrectomy assessment.

Alport syndrome results from mutations in the COL4A5 (X-linked) or COL4A3/COL4A4 (recessive) genes. This study examined 754 previously- unpublished variants in these genes from individuals referred for genetic testing in 12 accredited diagnostic laboratories worldwide, in addition to all published COL4A5, COL4A3 and COL4A4 variants in the LOVD databases. It also determined genotype-phenotype correlations for variants where clinical data were available. Individuals were referred for genetic testing where Alport syndrome was suspected clinically or on biopsy (renal failure, hearing loss, retinopathy, lamellated glomerular basement membrane), variant pathogenicity was assessed using currently-accepted criteria, and variants were examined for gene location, and age at renal failure onset. Results were compared using Fisher's exact test (DNA Stata). Altogether 754 new DNA variants were identified, an increase of 25%, predominantly in people of European background. Of the 1168 COL4A5 variants, 504 (43%) were missense mutations, 273 (23%) splicing variants, 73 (6%) nonsense mutations, 169 (14%) short deletions and 76 (7%) complex or large deletions. Only 135 of the 432 Gly residues in the collagenous sequence were substituted (31%), which means that fewer than 10% of all possible variants have been identified. Both missense and nonsense mutations in COL4A5 were not randomly distributed but more common at the 70 CpG sequences (pAla substitutions were underrepresented in all three genes (p< 0.0001) probably because of an association with a milder phenotype. The average age at end-stage renal failure was the same for all mutations in COL4A5 (24.4 ±7.8 years), COL4A3 (23.3 ± 9.3) and COL4A4 (25.4 ± 10.3) (COL4A5 and COL4A3, p = 0.45; COL4A5 and COL4A4, p = 0.55; COL4A3 and COL4A4, p = 0.41). For COL4A5, renal failure occurred sooner with non-missense than missense variants (p

Background: Mutations in TSC1 or TSC2 cause the tuberous sclerosis complex (TSC), while mutations in PKD1 or PKD2 cause autosomal dominant polycystic kidney disease (ADPKD). PKD1 lays immediately adjacent to TSC2 and deletions involving both genes, the PKD1/TSC2 contiguous gene syndrome (CGS), are characterized by severe ADPKD, plus TSC. mTOR inhibitors have proven effective in reducing angiomyolipoma (AML) in TSC and total kidney volume in ADPKD but without a positive effect on renal function. Methods and results: We describe a patient with independent truncating PKD1 and TSC2 mutations who has the expected phenotype for both diseases independently instead of the severe one described in PKD1/TSC2-CGS. Treatment with mTOR inhibitors reduced the AML and kidney volume for 2 years but thereafter they resumed growth; no positive effect on renal function was seen throughout. This is the first case addressing the response to mTOR treatment when independent truncating mutations in PKD1 and TSC2 are present. Conclusions: This case reveals that although PKD1 and TSC2 are adjacent genes and there is likely cross-talk between the PKD1 and TSC2 signalling pathways regulating mTOR, having independent TSC2 and PKD1 mutations can give rise to a milder kidney phenotype than is typical in PKD1/TSC2-CGS cases. A short-term beneficial effect of mTOR inhibition on AML and total kidney volume was not reflected in improved renal function.

Altres ajuts: Fundación Renal Iñigo Álvarez de Toledo (FRIAT) Genetic diagnosis of steroid-resistant nephrotic syndrome (SRNS) using Sanger sequencing is complicated by the high genetic heterogeneity and phenotypic variability of this disease. We aimed to improve the genetic diagnosis of SRNS by simultaneously sequencing 26 glomerular genes using massive parallel sequencing and to study whether mutations in multiple genes increase disease severity. High-throughput mutation analysis was performed in 50 SRNS and/or focal segmental glomerulosclerosis (FSGS) patients, a validation cohort of 25 patients with known pathogenic mutations, and a discovery cohort of 25 uncharacterized patients with probable genetic etiology. In the validation cohort, we identified the 42 previously known pathogenic mutations across NPHS1, NPHS2, WT1, TRPC6, and INF2 genes. In the discovery cohort, disease-causing mutations in SRNS/FSGS genes were found in nine patients. We detected three patients with mutations in an SRNS/FSGS gene and COL4A3. Two of them were familial cases and presented a more severe phenotype than family members with mutation in only one gene. In conclusion, our results show that massive parallel sequencing is feasible and robust for genetic diagnosis of SRNS/FSGS. Our results indicate that patients carrying mutations in an SRNS/FSGS gene and also in COL4A3 gene have increased disease severity.

Molecular diagnostics of autosomal dominant polycystic kidney disease (ADPKD) relies on mutation screening of PKD1 and PKD2, which is complicated by extensive allelic heterogeneity and the presence of six highly homologous sequences of PKD1. To date, specific sequencing of PKD1 requires laborious long-range amplifications. The high cost and long turnaround time of PKD1 and PKD2 mutation analysis using conventional techniques limits its widespread application in clinical settings. We performed targeted next-generation sequencing (NGS) of PKD1 and PKD2. Pooled barcoded DNA patient libraries were enriched by in-solution hybridization with PKD1 and PKD2 capture probes. Bioinformatics analysis was performed using an in-house developed pipeline. We validated the assay in a cohort of 36 patients with previously known PKD1 and PKD2 mutations and five control individuals. Then, we used the same assay and bioinformatics analysis in a discovery cohort of 12 uncharacterized patients. We detected 35 out of 36 known definitely, highly likely, and likely pathogenic mutations in the validation cohort, including two large deletions. In the discovery cohort, we detected 11 different pathogenic mutations in 10 out of 12 patients. This study demonstrates that laborious long-range PCRs of the repeated PKD1 region can be avoided by in-solution enrichment of PKD1 and PKD2 and NGS. This strategy significantly reduces the cost and time for simultaneous PKD1 and PKD2 sequence analysis, facilitating routine genetic diagnostics of ADPKD. This project was funded by the Spanish Plan Nacional SAF2008-00357 (NOVADIS); the Instituto de Salud Carlos III (FIS/FEDER PI11/00733; PI12/01523 and PI13/01731); the European Commission/n7th Framework Program, Project N. 261123 (GEUVADIS), and Project N. 262055 (ESGI); Spanish Renal Network for Research 16/06, RETICS, Instituto de Investigación Carlos III: REDinREN/RD06/0016 and RD012/0021 FEDER funds; the Catalan Government (AGAUR/n2009/SGR-1116); and the Fundación Renal Iñigo Álvarez de Toledo in Spain. D. T. is a PhD student supported by the Spanish Ministry of Economy and Competiveness. R. T. is supported by Intensification Programm of Research Activity ISCIII/Generalitat de Catalunya (programm I3SN). We acknowledge support of the Spanish Ministry of Economy and Competitiveness, ‘Centro de/nExcelencia Severo Ochoa 2013-2017’, SEV-2012-0208.

Introduction: Spermatogenesis is a highly complex process involving several thousand genes, only a minority of which have been studied in infertile men. In a previous study, we identified a number of Copy Number Variants (CNVs) by high-resolution array-Comparative Genomic Hybridization (a-CGH) analysis of the X chromosome, including 16 patient-specific X chromosome-linked gains. Of these, five gains (DUP1A, DUP5, DUP20, DUP26 and DUP40) were selected for further analysis to evaluate their clinical significance. Materials and Methods: The copy number state of the five selected loci was analyzed by quantitative-PCR on a total of 276 idiopathic infertile patients and 327 controls in a conventional case-control setting (199 subjects belonged to the previous a-CGH study). For one interesting locus (intersecting DUP1A) additional 338 subjects were analyzed. Results and Discussion: All gains were confirmed as patient-specific and the difference in duplication load between patients and controls is significant (p = 1.65 x 10(-4)). Two of the CNVs are private variants, whereas 3 are found recurrently in patients and none of the controls. These CNVs include, or are in close proximity to, genes with testis-specific expression. DUP1A, mapping to the PAR1, is found at the highest frequency (1.4%) that was significantly different from controls (0%) (p = 0.047 after Bonferroni correction). Two mechanisms are proposed by which DUP1A may cause spermatogenic failure: i) by affecting the correct regulation of a gene with potential role in spermatogenesis; ii) by disturbing recombination between PAR1 regions during meiosis. This study allowed the identification of novel spermatogenesis candidate genes linked to the 5 CNVs and the discovery of the first recurrent, X-linked gain with potential clinical relevance.

INTRODUCTION AND AIMS: Focal segmental glomerulosclerosis (FSGS) is a common cause of steroid resistant nephrotic syndrome where injury of podocytes plays a central role in pathogenesis. In recent years, many inheritable forms of FSGS caused by mutations in proteins important for podocyte function have been reported. We are presenting two patients (mother and son) with familial FSGS caused by INF2 mutation as the first case detected in Croatia. METHODS: Clinical case: RESULTS: A 19-year-old patient was admitted to our Department for evaluation of 24h-proteinuria 2.2 g/dU and slightly decreased eGFR (75 ml/min). At admission he had normal serum creatinine (sCr) (108 µmol/l), urine sediment was unremarkable and blood pressure was normal. A renal biopsy revealed FSGS. He was treated with ACE inhibitor. After one year of follow-up sCr increased to 144 µmol/l and 24h-proteinuria to 3.9 g/dU. Moreover, he had remarkable family history. At age of 20 yrs. patient' s mother was also diagnosed with FSGS and had similar clinical course - from non- nephrotic to nephrotic proteinuria, gradually progressing over 10 years to ESRD. She was transplanted and until now no relapse in transplanted kidney was observed. Interestingly, she was also resistant to immunosuppressive treatment (steroids, cyclosporine).Clinical course and positive family history were indicative for inherited FSGS (particularly the INF2 gene mutation). Analysis of the INF2 gene was performed in the Molecular Biology Laboratory of Fundacio Puigvert in Barcelona, Spain. Genetic analysis revealed that the proband carried the sequence variant c.658G>A>C (p.E220K) in heterozygosity in exon 4 of the INF2 gene. The identified mutation was found in his affected mother but not in his father, who had normal renal function without proteinuria. Two years after kidney biopsy progression of kidney disease was observed (sCr 166 µmol/l, eGFR 61 ml/min, 24- h proteinuria 4.93 g/dU). Although data from the literature are scarce and sometimes contradictory, we introduced a trial of cyclosporine 5 mg/kg and after 6 months observed moderate decline in proteinuria to 3.0 g/dU however accompanied with further deterioration of kidney function (SC 181 µmol/l , eGFR 54.9 ml/min). CONCLUSIONS: This case report emphasized again the importance of family history in renal disorders especially in young patients. Genetic screening is justified in particular group of patients where it might have crucial role in making treatment decision and avoiding of prolonged unhelpful exposure to corticosteroids or cyclophosphamide. Finally, this case report adds evidence for potential antiproteinuric effect of cyclosporine treatment.