Biology subjects

Stranecky, V.

Publications and source records attributed to Stranecky, V..

3 recordsLinked to original sources

bioRxiv2025

Long-Read Sequencing of the MUC1 VNTR: Genomic Variation, Mutational Landscape, and Its Impact on ADTKD Diagnosis and Progression

BackgroundADTKD-MUC1 is caused by frameshift mutations in MUC1 gene that produce a frameshifted protein (MUC1fs) toxic to kidney cells. The genes variable number of tandem repeats (VNTR), with high GC content, makes it largely inaccessible to standard sequencing. As a result, both the reference sequence and natural variation in this region remain poorly defined, complicating mutation detection and data interpretation. Standard methods also fail to pinpoint the exact VNTR unit affected, limiting insight into mutation mechanisms and genotype-phenotype correlations. MethodsWe employed Single Molecule, Real-Time (SMRT) sequencing and characterized the genomic sequence of MUC1 in 300 individuals including 279 individuals from 143 families suspected of having ADTKD-MUC1. We compared these results to those obtained using the CLIA-approved mass spectrometry-based probe extension (PE) assay, which specifically detect the most prevalent 59dupC mutation. We correlated the structural features of the MUC1 VNTR with the rate of kidney function decline in affected individuals. ResultsWe identified MUC1 consensus sequences for 205 unique VNTR alleles, with 9 distinct types of frameshift mutations present on 52 distinct mutated VNTR alleles. MUC1 frameshift mutations were identified in 71 of 143 families (50%) with suspected ADTKD, comprising 135 genetically affected individuals (48%). The SMRT assay exhibited complete concordance and revealed that the PE assay is capable of detecting frameshift mutations in approximately 85% of affected families. The constellation of VNTR structures supports a genotype-progression model, in which fast progressors exhibit a significantly lower number of repeat units on the wild-type allele and a higher number of repeats on the mutation-bearing allele, including an increased number of frameshifted repeat units. ConclusionsSMRT sequencing outperforms current diagnostic methods for ADTKD-MUC1 and reveals the prognostic value of VNTR structures. Although their contribution to disease progression is modest ([~]6% variance explained), it remains biologically and clinically meaningful. Key Points 3O_LISingle Molecule, Real-Time (SMRT) sequencing of MUC1 outperforms existing genetic and immunohistochemical methods for ADTKD-MUC1 diagnosis. C_LIO_LICLIA-approved mass spectrometry-based genotyping assay, complemented by SMRT sequencing, can detect nearly all ADTKD-MUC1 patients. C_LIO_LIDisease progression correlates with VNTR pattern: fast progressors have fewer WT repeats and more mutant/frameshifted repeats C_LI

genetics↗

bioRxiv2022

AGAL misprocessing-induced ER stress and the unfolded protein response: lysosomal storage-independent mechanism of Fabry disease pathogenesis?

BackgroundClassic Fabry disease (FD) is caused by GLA mutations that result in enzymatic deficiency of alpha-galactosidase A (AGAL), lysosomal storage of globotriaosylceramide, and a resulting multisystemic disease. In non-classic later-onset FD, patients have some preserved AGAL activity and a milder disease course, though female carriers may also be affected. While FD pathogenesis has been mostly attributed to catalytic deficiency of mutated AGAL, lysosomal storage and impairment of lysosomal functions, other pathogenic factors may be important, especially in non-classic later-onset FD. MethodsWe characterized the clinical, biochemical, genetic, molecular, cellular and organ pathology correlates of the p.L394P AGAL variant that was identified in six individuals with end-stage kidney disease by the Czech national screening program for FD and by further screening of 25 family members. ResultsClinical findings revealed a milder clinical course with ~15% residual AGAL activity. Laboratory investigations documented intracellular retention of mutated AGAL with resulting ER stress and the unfolded protein response (UPR). Kidney biopsies did not show lysosomal storage. We observed similar findings of ER stress and UPR with several other classic and non-classic FD missense GLA variants. ConclusionsWe identified defective proteostasis of mutated AGAL resulting in chronic ER stress and UPR of AGAL expressing cells (hereafter referred to as AGALopathy) as an important contributor to FD pathogenesis. These findings provide insight into non-classic later-onset FD and may better explain clinical manifestations with implications for pathogenesis, clinical characterization and treatment of all FD forms. Significance statementCatalytic deficiency of mutated AGAL is responsible for classicFabry disease (FD) pathogenesis but does not fully explain the findings in non-classic later-onset FD, in which affected individuals and female carriers develop clinical manifestations despite some AGAL activity and variably mitigated lysosomal storage. In this investigation of individuals with the p.L394P AGAL variant, we identified defective proteostasis of mutated AGAL resulting in chronic endoplasmic reticulum stress and the unfolded protein response as significant contributors to pathogenesis of non-classic later-onset FD. Similar effects were documented also in other AGAL variants identified in classic and non-classicFD. Endoplasmic reticulum stress and the unfolded protein response therefore play an important role in FD.

molecular biology↗

bioRxiv2018

De novo mutations in the GTP/GDP-binding region of RALA, a RAS-like small GTPase, cause intellectual disability and developmental delay

Mutations that alter signaling of RAS/MAPK-family proteins give rise to a group of Mendelian diseases known as RASopathies, but the matrix of genotype-phenotype relationships is still incomplete, in part because there are many RAS-related proteins, and in part because the phenotypic consequences may be variable and/or pleiotropic. Here, we describe a cohort of ten cases, drawn from six clinical sites and over 16,000 sequenced probands, with de novo protein-altering variation in RALA, a RAS-like small GTPase. All probands present with speech and motor delays, and most have intellectual disability, low weight, short stature, and facial dysmorphism. The observed rate of de novo RALA variants in affected probands is significantly higher (p=4.93 x 10-11) than expected from the estimated mutation rate. Further, all de novo variants described here affect conserved residues within the GTP/GDP-binding region of RALA; in fact, six alleles arose at only two codons, Val25 and Lys128. We directly assayed GTP hydrolysis and RALA effector-protein binding, and all but one tested variant significantly reduced both activities. The one exception, S157A, reduced GTP hydrolysis but significantly increased RALA-effector binding, an observation similar to that seen for oncogenic RAS variants. These results show the power of data sharing for the interpretation and analysis of rare variation, expand the spectrum of molecular causes of developmental disability to include RALA, and provide additional insight into the pathogenesis of human disease caused by mutations in small GTPases.\n\nAuthor SummaryWhile many causes of developmental disabilities have been identified, a large number of affected children cannot be diagnosed despite extensive medical testing. Previously unknown genetic factors are likely to be the culprits in many of these cases. Using DNA sequencing, and by sharing information among many doctors and researchers, we have identified a set of individuals with developmental problems who all have changes to the same gene, RALA. The affected individuals all have similar symptoms, including intellectual disability, speech delay (or no speech), and problems with motor skills like walking. In nearly all of these cases (10 of 11), the genetic change found in the child was not inherited from either parent. The locations and biological properties of these changes suggest that they are likely to disrupt the normal functions of RALA and cause significant health problems. We also performed experiments to show that the genetic changes found in these individuals alter two key functions of RALA. Together, we have provided evidence that genetic changes in RALA can cause DD/ID. These results will allow doctors and researchers to identify additional children with the same condition, providing a clinical diagnosis to these families and leading to new research opportunities.

genetics↗