A novel spot mutation leading to sialidosis type 1-myoclonus syndrome and optical coherence tomography findings.

This report presents the optical coherence tomography findings and a new NEU1 mutation in bilateral macular cherry-red spot syndrome associated with sialidosis type 1. A 19-year-old patient with a macular cherry-red spot underwent metabolic and genetic analyses supported by spectral-domain optical coherence tomography. Fundus examination revealed bilateral macular cherry-red spot. Spectral-domain optical coherence tomography revealed increased hyperreflectivity in the retinal inner layers and the photoreceptor layer in the foveal region. The genetic analysis detected a new NEU1 mutation, which caused type I sialidosis. In cases with a macular cherry-red spot, sialidosis should be included in the differential diagnosis, and NEU1 mutation should be screened. Spectral-domain optical coherence tomography alone is not sufficient in the differential diagnosis because childhood metabolic diseases may exhibit similar signs.

Genome editing in mucopolysaccharidoses and mucolipidoses.

Mucopolysaccharidoses (MPS) and mucolipidoses (ML) are disorders that alter lysosome function. While MPS are caused by mutation in enzymes that degrade glycosaminoglycans, the ML are disorders characterized by reduced function in the phosphotransferase enzyme. Multiple clinical features are associated with these diseases and the exact mechanisms that could explain such different clinical manifestations in patients are still unknown. Furthermore, there are no curative treatment for any of MPS and ML conditions so far. Gene editing holds promise as a tool for the creation of cell and animal models to help explain disease pathogenesis, as well as a platform for gene therapy. In this chapter, we discuss the main studies involving genome editing for MPS and the prospect applications for ML.

GNPTAB missense mutations cause loss of GlcNAc-1-phosphotransferase activity in mucolipidosis type II through distinct mechanisms.

Mucolipidoses (ML) II and III alpha/beta are lysosomal storage diseases caused by pathogenic mutations in GNPTAB encoding the α/ß-subunit precursor of GlcNAc-1-phosphotransferase. To determine genotype-phenotype correlation and functional analysis of mutant GlcNAc-1-phosphotransferase, 13 Brazilian patients clinically and biochemical diagnosed for MLII or III alpha/beta were studied. By sequencing of genomic GNPTAB of the MLII and MLIII alpha/beta patients we identified six novel mutations: p.D76G, p.S385L, p.Q278Kfs*3, p.H588Qfs*27, p.N642Lfs*10 and p.Y1111*. Expression analysis by western blotting and immunofluorescence microscopy revealed that the mutant α/ß-subunit precursor p.D76G is retained in the endoplasmic reticulum whereas the mutant p.S385L is correctly transported to the cis-Golgi apparatus and proteolytically processed. Both mutations lead to complete loss of GlcNAc-1-phosphotransferase activity, consistent with the severe clinical MLII phenotype of the patients. Our study expands the genotypic spectrum of MLII and provides novel insights into structural requirements to ensure GlcNAc-1-phosphotransferase activity.

Enigmatic in vivo GlcNAc-1-phosphotransferase (GNPTG) transcript correction to wild type in two mucolipidosis III gamma siblings homozygous for nonsense mutations.

Mucolipidosis (ML) III gamma is a rare autosomal-recessive disorder caused by pathogenic mutations in the GNPTG gene. GNPTG encodes the γ-subunit of GlcNAc-1-phosphotransferase that catalyzes mannose 6-phosphate targeting signal synthesis on soluble lysosomal enzymes. ML III gamma patients are characterized by missorting of lysosomal enzymes. In this report, we describe the probable occurrence of mRNA editing in two ML III gamma patients. Patients A and B (siblings) presented at the adult age with a typical clinical picture of ML III gamma, mainly compromising bone and joints, and high levels of lysosomal enzymes in plasma and low levels in fibroblasts. Both were found to be homozygous for c.-112C>G and c.328G>T (p.Glu110Ter) mutations in genomic DNA (gDNA) analysis of GNPTG. Analysis of complementary DNA (cDNA), however, showed normal genotypes for both patients. Low GNPTG mRNA expression was observed in both patients. The mRNA editing can explain the differences found in patients A and B regarding gDNA and cDNA analysis, and the mild clinical phenotype associated with homozygosity for a nonsense mutation. Our results suggest that mRNA editing can be more frequent than expected in monogenic disorders and that GNPTG analysis should be performed on gDNA.

Variable phenotype and severity of sialidosis expressed in two siblings presenting with ataxia and macular cherry-red spots.

Sialidosis is a rare lysosomal storage disease with a wide clinical spectrum ranging from nearly asymptomatic to severe presentations. We present two Brazilian siblings with sialidosis, the first patient with sialidosis type I, and the second with sialidosis type II. Our report reinforces the relevance of ophthalmologic evaluation in patients with early and late-onset ataxias, if an association with myoclonus or dysmorphic features is present or not. Also, we demonstrate that sialidosis might represent a single genetic entity with variable clinical expression through these two siblings.

Mucolipidosis II and III alpha/beta in Brazil: analysis of the GNPTAB gene.

UNLABELLED: Mucolipidosis II and III (MLII and MLIII) alpha/beta are rare autosomal recessive lysosomal storage diseases (LSDs) caused by pathogenic variations in the GNPTAB gene. GNPTAB gene codes for the α and ß subunits of phosphotransferase, the enzyme responsible for synthesis of the mannose-6-phosphate (M6P) marker that directs lysosomal enzymes to the lysosome. OBJECTIVES: The objective of this study is to identify sequence variations of the GNPTAB gene in Brazilian patients with MLII and MLIII alpha/beta. METHOD: Sequencing of the GNPTAB gene was performed in samples of gDNA extracted from the peripheral blood of patients with MLII/III diagnosed at a national reference center for LSDs. RESULTS: Twelve unrelated patients, from several regions of Brazil, were included in this study. Only one was born of consanguineous parents. All patients were found to carry at least one nonpathogenic variation. Nine causal sequence variations were found: c.242G>T (p.W81L); c.1123C>T (p.R375X); c.1196C>T (p.S399F); c.1208T>C (p.I403T); c.1514G>A (p.C505Y); c.1759C>T (p.R587X); c.2808A>G (p.Y937_M972del, novel mutation); c. 2269_2273delGAAAC (p.E757KfsX2, novel mutation); and c.3503_3504delTC (p.L1168QfsX5). Both pathogenic variations were identified in 8 of 12 patients; in four patients, only one pathogenic variation was identified. Mutation c.3503_3504delTC, located in exon 19, was the most frequent pathogenic variation found (n=11/24 alleles). The deleterious effect of the c.2808A>C mutation on splicing was confirmed by cDNA analysis. DISCUSSION/CONCLUSIONS: Our findings confirm that the GNPTAB gene presents broad allelic heterogeneity and suggests that, in Brazilian ML II and III patients, screening for mutations should begin at exon 19 of the GNPTAB gene. Further analyses will be conducted on patients in whom both pathogenic mutations have not been found in this study.

Mucolipidosis III / Mucolipidosis III

Se describe, en 4 hermanos (3M y 1F), adultos, una enfermedad metabólica del tipo mucolipidosis III. Clínica y radiológicamente presentaron síntomas típicos de mucopolisacaridosis (facies tosca y disostosis múltiple) de las cuales se pudieron diferenciar, fundamentalmente, por la ausencia de mucopolisacariduria. El curso lentamente progresivo, los hallazgos estructurales característicos en la biopsia de piel y el comportamiento típico de las enzimas lisosomales elevadas en suero confirman el diagnóstico. Estas constituyen la primera comunicación de la enfermedad en Cuba y se debe a la introducción de nuevastécnicas para el diagnóstico bioquímico y ultraestructural de las enfermedades metabólicas en nuestro medio (AU)

Mucolipidosis III / Mucolipidosis III

Se describe, en 4 hermanos (3M y 1F), adultos, una enfermedad metabolica del tipo mucolipidosis III. Clinica y radiologicamente presentaron sintomas tipicos de mucopolisacaridosis (facies tosca y disostosis multiple) de las cuales se pudieron diferenciar, fundamentalmente, por la ausencia de mucopolisacariduria. El curso lentamente progresivo, los hallazgos estructurales caracteristicos en la biopsia de piel y el comportamiento tipico de las enzimas lisosomales elevadas en suero confirman el diagnostico. Estas constituyen la primera comunicacion de la enfermedad en Cuba y se debe a la introduccion de nuevastecnicas para el diagnostico bioquimico y ultraestructural de las enfermedades metabolicas en nuestro medio

[Mucolipidosis type II. Report of 2 suggestive cases]. / Mucolipidose do tipo II. Registro de dois casos sugestivos.

The clinical and laboratorial study of two brothers with gargoylism is reported. The examination of the urine showed normal findings of mucopolysaccharides. The authors made differential diagnoses with others mucolipidoses and concluded that mucolipidose type II should be considered in any patient with gargoylism.