Cervical pachymeningeal hypertrophy as the initial and cardinal manifestation of mucopolysaccharidosis type I in monozygotic twins with a novel mutation in the alpha-L-iduronidase gene

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

Intrathecal gene therapy corrects CNS pathology in a feline model of mucopolysaccharidosis I

Enzyme replacement therapy has revolutionized the treatment of the somatic manifestations of lysosomal storage diseases (LSD), although it has been ineffective in treating central nervous system (CNS) manifestations of these disorders. The development of neurotrophic vectors based on novel serotypes of adeno-associated viruses (AAV) such as AAV9 provides a potential platform for stable and efficient delivery of enzymes to the CNS. We evaluated the safety and efficacy of intrathecal delivery of AAV9 expressing α-l-iduronidase (IDUA) in a previously described feline model of mucopolysaccharidosis I (MPS I). A neurological phenotype has not been defined in these animals, so our analysis focused on the biochemical and histological CNS abnormalities characteristic of MPS I. Five MPS I cats were dosed with AAV9 vector at 4-7 months of age and followed for 6 months. Treated animals demonstrated virtually complete correction of biochemical and histological manifestations of the disease throughout the CNS. There was a range of antibody responses against IDUA in this cohort which reduced detectable enzyme without substantially reducing efficacy; there was no evidence of toxicity. This first demonstration of the efficacy of intrathecal gene therapy in a large animal model of a LSD should pave the way for translation into the clinic.

Structural and clinical implications of amino acid substitutions in α-L-iduronidase: insight into the basis of mucopolysaccharidosis type I

Allelic mutations, predominantly missense ones, of the α-l-iduronidase (IDUA) gene cause mucopolysaccharidosis type I (MPS I), which exhibits heterogeneous phenotypes. These phenotypes are basically classified into severe, intermediate, and attenuated types. We previously examined the structural changes in IDUA due to MPS I by homology modeling, but the reliability was limited because of the low sequence identity. In this study, we built new structural models of mutant IDUAs due to 57 amino acid substitutions that had been identified in 27 severe, 1 severe-intermediate, 13 intermediate, 1 attenuated-intermediate and 15 attenuated type MPS I patients based on the crystal structure of human IDUA, which was recently determined by us. The structural changes were examined by calculating the root-mean-square distances (RMSD) and the number of atoms influenced by the amino acid replacements. The results revealed that the structural changes of the enzyme protein tended to be correlated with the severity of the disease. Then we focused on the structural changes resulting from amino acid replacements in the immunoglobulin-like domain and adjacent region, of which the structure had been missing in the IDUA model previously built. Coloring of atoms influenced by an amino acid substitution was performed in each case and the results revealed that the structural changes occurred in a region far from the active site of IDUA, suggesting that they affected protein folding. Structural analysis is thus useful for elucidation of the basis of MPS I.