Novel missense mutation in the GALNS gene in an affected patient with severe form of mucopolysaccharidosis type IVA

Lysosomal Dysfunction: Connecting the Dots in the Landscape of Human Diseases

Lysosomes are the main organelles responsible for the degradation of macromolecules in eukaryotic cells. Beyond their fundamental role in degradation, lysosomes are involved in different physiological processes such as autophagy, nutrient sensing, and intracellular signaling. In some circumstances, lysosomal abnormalities underlie several human pathologies with different etiologies known as known as lysosomal storage disorders (LSDs). These disorders can result from deficiencies in primary lysosomal enzymes, dysfunction of lysosomal enzyme activators, alterations in modifiers that impact lysosomal function, or changes in membrane-associated proteins, among other factors. The clinical phenotype observed in affected patients hinges on the type and location of the accumulating substrate, influenced by genetic mutations and residual enzyme activity. In this context, the scientific community is dedicated to exploring potential therapeutic approaches, striving not only to extend lifespan but also to enhance the overall quality of life for individuals afflicted with LSDs. This review provides insights into lysosomal dysfunction from a molecular perspective, particularly in the context of human diseases, and highlights recent advancements and breakthroughs in this field.

Molecular characterization of a large cohort of Mucopolysaccharidosis patients: Iran Mucopolysaccharidosis RE-diagnosis Study (IMPRESsion)

Mucopolysaccharidoses (MPSs) are rare, heterogeneous inborn errors of metabolism (IEM) diagnosed through a combination of clinical, biochemical, and genetic investigations. The aim of this study was molecular characterization of the largest cohort of Iranian MPS patients (302 patients from 289 unrelated families), along with tracking their ethnicity and geographical origins. 185/289 patients were studied using an IEM-targeted NGS panel followed by complementary Sanger sequencing, which led to the diagnosis of 154 MPS patients and 5 non-MPS IEMs (diagnostic yield: 85.9%). Furthermore, 106/289 patients who were referred with positive findings went through re-analysis and confirmatory tests which confirmed MPS diagnosis in 104. Among the total of 258 MPS patients, 225 were homozygous, 90 harbored novel variants, and 9 had copy number variations. MPS IV was the most common type (34.8%) followed by MPS I (22.7%) and MPS VI (22.5%). Geographical origin analysis unveiled a pattern of distribution for frequent variants in ARSB (c.430G>A, c.962T>C [p.Leu321Pro], c.281C>A [p.Ser94*]), GALNS (c.319G>A [p.Ala107Thr], c.860C>T [p.Ser287Leu], c.1042A>G [p.Thr348Ala]), and IDUA (c.1A>C [p.Met1Leu], c.1598C>G [p.Pro533Arg], c.1562_1563insC [p.Gly522Argfs*50]). Our extensive patient cohort reveals the genetic and geographic landscape of MPS in Iran, which provides insight into genetic epidemiology of MPS and can facilitate a more cost-effective, time-efficient diagnostic approach based on the region-specific variants. This article is protected by copyright. All rights reserved.

Clinical, biochemical and molecular features of Iranian families with mucopolysaccharidosis: A case series

This study aims to ascertain the genetic variants which contribute to the most common types of MPS in eleven Iranian families. Clinical and biochemical features were obtained during initial examination and patients were further investigated for genetic defects in the MPS genes. Peripheral blood samples were obtained from all family members after obtaining written informed consent. Based on the patient's clinical diagnosis, three different genetic tests including Sanger sequencing of four genes (IDUA, IDS, SGSH, and GALNS), targeted panel (10 genes) and Whole Exome Sequencing (WES) techniques were applied to identify the causative variants. A total of 12 different mutations were identified in five genes, including nine novel mutations and three previously reported missense mutations. Sanger sequencing confirmation of the identified mutations determined one case of compound heterozygous in the NAGLU gene. In this study, novel mutations in MPS related genes were identified attempting to characterize the type and subtype of the disease using molecular approaches. Results of the study positively contribute to mutation spectrum of IDUA, IDS, SGSH, NAGLU, and GALNS genes in the Iranian cohort. It may also enrich genetic counseling for rapid risk assessment and disease management.