MO046NGS PANEL PERFORMANCE IN THE DIAGNOSIS OF HEREDITARY RENAL DISEASE IN SOUTHERN SPAIN

Background and Aims Hereditary renal disease (HRD) is still underdiagnosed: although we know aspects related to autosomal dominant polycystic kidney disease (ADPKD), we know little about the incidence and prevalence of other entities such as Alport syndrome. Altogether, HRD can represent 15% of individuals undergoing renal replacement therapy (RRT) or could even be higher. The advancement of genetics at the healthcare level let to achieve accurate and early renal diagnoses, as well as the incorporation of genetic counseling to families, all of which will result in better management of the disease in its initial stages and the possibility of offering reproductive options that avoid transmission to offspring. Our objective is to know the performance offered by the implementation of the ERH panel through Next Generation Sequencing (NGS) in our healthcare area. Method Observational-descriptive study of 259 probands (141 men / 118 women), mean age of 46 years (30 pediatric / 123 over 50 years), with chronic kidney disease and suspected hereditary cause attended in the specialized consultation of our centers from October 2018 to October 2020. The DNA extracted from leukocytes obtained by venipuncture was processed with Nephropathies Solution version 3 panel (SOPHiA Genetics) according to the manufacturer's protocol. This panel covers the coding regions and splicing junctions of 44 HRD-related genes such as nephrotic syndromes, polycystic kidney diseases, Bartter syndromes, Alport syndrome, CAKUT or tubulopathies (table 1). The sequencing of the libraries was done in a MiSeq (Illumina Inc), the bioinformatic analysis of the data and annotation of variants was performed using the SOPHiA DDM 5.8.0.3 software, and the revision of variants by consulting the main databases (ClinVar, Exac, HGMD, NCBI, PKD Foundation, LOVD). Results The panel was informative (pathogenic or probably pathogenic) in 80/259 patients (31%) and 56/259 cases (21.66%) of variants of uncertain significance (VSI) were detected. Autosomal dominant polycystic kidney disease accounted for 76.2% of the variants identified (56.2% PKD1, 20% PKD2), following Alport syndrome with 15% and the alterations in the PKHD1 gene associated with renal polycystic disease in its recessive form with about 4% (Figure 1). We have also identified a case of autosomal dominant tubulointerstitial kidney disease associated with the UMOD gene that was not suspected until the genetic study was performed. We highlight that 45% (36/80) of the variants identified as responsible for the renal disease are not yet described. Overall, the most prevalent type of mutation is that which produces displacement in the reading frame or frameshift (Figure 2). Individually, frameshift is the most frequent alteration in PKD1, PKD2 and COL4A5, while for PKHD1, COL4A3 and COL4A4 it is missense. Conclusion Our NGS HRD panel a) offers an adequate diagnostic performance at the healthcare level, with definitive results in 1 out of 3 cases and has also allowed the performance of many carrier studies among family members b) is able of diagnosing the most frequent disease, ADPKD and Alport syndrome, as well as unresolved or poorly characterized cases, and c) opens the horizon for new diagnoses, all without increasing costs by outsourcing services. All this makes the genetic study of renal pathology a useful and efficient strategy. These results encourage us to enhance the resources in this area that we consider to be of strategic value.

The consequences of increased 4E-BP1 in polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease, characterized by cyst formation and growth. Hyperproliferation is a major contributor to cyst growth. At the nexus of regulating proliferation, is 4E-BP1. We demonstrate that ADPKD mouse and rat models, ADPKD patient renal biopsies and PKD1−/− cells exhibited hyperphosphorylated 4E-BP1, a biomarker of increased translation and proliferation. We hypothesized that expression of constitutively active 4E-BP1 constructs (4E-BP1F113A and 4E-BP1R13AF113A) would decrease proliferation and reduce cyst expansion. Utilizing the Pkd1RC/RC mouse, we determined the effect of 4E-BP1F113A on PKD. Unexpectedly, 4E-BP1F113A resulted in increased cyst burden and suppressed apoptosis markers, increased anti-apoptotic Bcl-2 protein and increased mitochondrial proteins. Exogenous 4E-BP1 enhanced proliferation, decreased apoptosis, increased anti-apoptotic Bcl-2 protein, impaired NADPH oxidoreductase activity, increased mitochondrial proteins and increased superoxide production in PKD patient-derived renal epithelial cells. Reduced 4E-BP1 expression suppressed proliferation, restored apoptosis and improved cellular metabolism. These findings provide insight into how cyst-lining cells respond to 4E-BP1.

Cerebrovascular Diseases

Acute and chronic interstitial inflammation can result in injury to renal tubules, leading to tubular dysfunction and, chronically, tubular atrophy. Causes of chronic tubulointerstitial damage include autoimmune and hereditary causes, analgesic nephropathy, uric acid, lithium, heavy metals, mercury, lead, and oxalate. Autosomal dominant polycystic kidney disease is the most common hereditary renal disease. It occurs in both males and females and is characterized by multiple bilateral renal cysts and cysts in other organs (eg, liver, spleen, and pancreas).