Imbalanced cellular metabolism compromises cartilage homeostasis and joint function in a mouse model of mucolipidosis type III gamma.

Mucolipidosis type III (MLIII) gamma is a rare inherited lysosomal storage disorder caused by mutations in GNPTG encoding the γ-subunit of GlcNAc-1-phosphotransferase, the key enzyme ensuring proper intracellular location of multiple lysosomal enzymes. Patients with MLIII gamma typically present with osteoarthritis and joint stiffness, suggesting cartilage involvement. Using Gnptg knockout (Gnptgko ) mice as a model of the human disease, we showed that missorting of a number of lysosomal enzymes is associated with intracellular accumulation of chondroitin sulfate in Gnptgko chondrocytes and their impaired differentiation, as well as with altered microstructure of the cartilage extracellular matrix (ECM). We also demonstrated distinct functional and structural properties of the Achilles tendons isolated from Gnptgko and Gnptab knock-in (Gnptabki ) mice, the latter displaying a more severe phenotype resembling mucolipidosis type II (MLII) in humans. Together with comparative analyses of joint mobility in MLII and MLIII patients, these findings provide a basis for better understanding of the molecular reasons leading to joint pathology in these patients. Our data suggest that lack of GlcNAc-1-phosphotransferase activity due to defects in the γ-subunit causes structural changes within the ECM of connective and mechanosensitive tissues, such as cartilage and tendon, and eventually results in functional joint abnormalities typically observed in MLIII gamma patients. This idea was supported by a deficit of the limb motor function in Gnptgko mice challenged on a rotarod under fatigue-associated conditions, suggesting that the impaired motor performance of Gnptgko mice was caused by fatigue and/or pain at the joint.This article has an associated First Person interview with the first author of the paper.

Clinical Characterization of Mucolipidoses II and III: A Multicenter Study.

Mucolipidoses (MLs) II and III are rare lysosomal diseases caused by deficiency of GlcNAc-1-phosphotransferase, and clinical manifestations are multisystemic. Clinical and demographic data from 1983 to 2013 were obtained retrospectively. Twenty-seven patients were included (ML II = 15, ML III α/beta = 9, ML III gamma = 3). The median age at diagnosis was 2.7 years. The predominant clinical presentations were skeletal symptoms. The ML II patients showed physical and cognitive impairment, while the ML III α/beta patients have more somatic abnormalities and usually were delayed in early development as compared with ML III gamma patients. This is the most comprehensive study exploring characteristics of Brazilian patients with MLs II and III.

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.

Mucopolysaccharidosis: Caregiver Quality of Life

Abstract The mucopolysaccharidoses (MPSs) are a group of rare genetic diseases caused by a deficiency of specific enzymes involved in catabolism of glycosaminoglycans, which causes multisystem abnormalities. Quality of life (QoL) is directly associated with physical, mental, and psychological well-being and with social relationships, including family and friends. Aims: To evaluate the QoL of caregivers of patients with MPS. Methods: Cross-sectional study using a convenience sampling strategy. The sample comprised mothers of patients with MPS seen at the Medical Genetics Service, Hospital de Clínicas de Porto Alegre, Brazil. The World Health Organization Quality of Life Assessment (WHOQOL-BREF) was used to assess QoL. Results: Eleven mothers of 12 patients with MPS (MPS-I = 1; MPS-II = 3; MPS-III = 3; MPS-IV = 4; and MPS-VI = 1) were included. The average WHOQOL-BREF score was 46.59, with the physical health domain scoring highest and the environmental domain scoring lowest. The lower QoL of mothers of children with MPS-II seems to be related to the worse clinical condition of these children, with more severe symptoms and greater need for help with daily activities as well as with a feeling of responsibility due to the inheritance pattern of the disease.

A double-blind, randomised, crossover trial of two botulinum toxin type a in patients with spasticity.

BACKGROUND: Botulinum toxin type A (btxA) is one of the main treatment choices for patients with spasticity. Prosigne® a new released botulinum toxin serotype A may have the same effectiveness as Botox® in focal dystonia. However, there are no randomized clinical trials comparing these formulations in spasticity treatment. The aim of our study was to compare the efficacy and safety of Prosigne® with Botox® in the treatment of spasticity. METHODOLOGY/PRINCIPAL FINDINGS: We performed a double-blind, randomized, crossover study consisting of 57 patients with clinically meaningful spasticity. The patients were assessed at baseline, 4 and 12 weeks after Prosigne® or Botox® administration. The main outcomes were changes in the patients' Modified Ashworth Scale (MAS), Functional Independence Measure (FIM) and Pediatric Evaluation of Disability Inventory (PEDI) scores and adverse effects related to the botulinum toxin. Both of the toxins were significantly effective in relieving the level of spasticity in adults and children. There were no significant differences found between the Prosigne® and Botox® treatments regarding their MAS, FIM and PEDI scores. Likewise, the incidence of adverse effects was similar between the two groups. CONCLUSION: Our results suggest that Prosigne® and Botox® are both efficient and comparable with respect to their efficacy and safety for the three month treatment of spasticity. TRIAL REGISTRATION: ClinicalTrials.gov NCT00819065.

Functional capacity evaluation of patients with mucopolysaccharidosis.

INTRODUCTION: The mucopolysaccharidoses (MPS) are rare genetic disorders caused by a deficiency in lysosomal enzymes that affect the catabolism of glycosaminoglycans and cause their accumulation, resulting in a multisystemic clinical picture. Their clinical manifestations result in limited ability to perform daily life tasks. OBJECTIVES: To evaluate functional capacity and joint range of motion (ROM) in patients with MPS followed at the reference center for lysosomal disorders at Hospital de Clínicas de Porto Alegre, Brazil. METHODS: This was a prospective longitudinal study with a convenience sample. The Pediatric Evaluation of Disability Inventory (PEDI) and the Functional Independence Measure (FIM) were used to evaluate functionality and goniometry was used to evaluate ROM at three times (baseline, 6 months, and 12 months after study inclusion). An exploratory analysis was done of the effect of enzyme replacement therapy (ERT) in both variables; thus, patients were divided into Group 1 (patients without ERT), Group 2 (patients on ERT before and after study inclusion), and Group 3 (patients who started ERT after study inclusion). RESULTS: 21 patients were included: 7 in Group 1 (MPS II: 3, MPS III-B: 2, MPS IV-A: 2), 6 in Group 2 (MPS I: 3; MPS VI: 3), and 8 in Group 3 (MPS I: 3, MPS II: 4, MPS VI: 1). A limitation in the mobility of all joints studied was found especially in MPS I, II, and VI. Functionality compromise was also frequent (PEDI=5/7 patients; MIF=9/14 patients), even in individuals with preserved cognition. No correlation was found between the findings of goniometry and the PEDI domains (self-care, mobility, social function). ERT did not seem to significantly change the parameters analyzed. DISCUSSION/CONCLUSION: The compromise of joint mobility and functionality seems to be common in MPS I, II, III-B, IV-A, and VI. This finding is in line with the fact that, although these types of MPS are caused by different genetic defects, they share metabolic routes and physiopathogenic processes and present similar clinical manifestations. The preservation of functionality is an increasing challenge in the treatment of MPS patients, and maintenance of occupational performance should be defined as an objective to be reached by therapies used. Further studies with a greater sample size are necessary in order to verify the effect of ERT in these variables.