Molecular characterization of CTNS mutations in Tunisian patients with ocular cystinosis.

BACKGROUND: Ocular cystinosis is a rare autosomal recessive disorder characterized by intralysosomal cystine accumulation in renal, ophthalmic (cornea, conjunctiva), and other organ abnormalities. Patients with ocular cystinosis are mostly asymptomatic and typically experience mild photophobia due to cystine crystals in the cornea observed accidently during a routine ocular examination. The ocular cystinosis is associated with different mutations in CTNS gene. Cysteamine therapy mostly corrects the organ abnormalities. METHODS: This study was performed in collaboration with the department of ophthalmology of Farhat Hached Hospital. The Optical Coherence Tomography (OCT) of the cornea and retinal photography were used to search cystine crystals within the corneas and conjunctiva in eight Tunisian patients. Screening for the common 57-kb deletion was performed by standard multiplex PCR, followed by direct sequencing of the entire CTNS gene. RESULTS: The studied patients were found to have cystine crystal limited anterior corneal stroma and the conjunctiva associated with retinal crystals accumulation. CTNS gene sequencing disclosed 7 mutations: three missense mutations (G308R, p.Q88K, and p.S139Y); one duplication (C.829dup), one framshift mutation (p.G258f), one splice site mutation (c.681 + 7delC) and a large deletion (20,327-bp deletion). Crystallographic structure analysis suggests that the novel mutation p.S139Y is buried in a first transmembrane helix closed to the lipid bilayer polar region, introducing a difference in hydrophobicity which could affect the hydrophobic interactions with the membrane lipids. The second novel mutation p.Q88K which is located in the lysosomal lumen close to the lipid membrane polar head region, introduced a basic amino acid in a region which tolerate only uncharged residue. The third missense mutation introduces a positive change in nonpolar tail region of the phospholipid bilayer membrane affecting the folding and stability of the protein in the lipid bilayer. CONCLUSIONS: Our data demonstrate that impaired transport of cystine out of lysosomes is the most common, which is obviously associated with the mutations of transmembrane domains of cystinosine resulting from a total loss of its activity.

Novel splice site IDUA gene mutation in Tunisian pedigrees with hurler syndrome.

BACKGROUND: The mucopolysaccharidosis type I (MPS I) is a lysosomal storage disease resulting from the defective activity of the enzyme α-L-iduronidase (IDUA). The disease has three major clinical subtypes (severe Hurler syndrome, intermediate Hurler-Scheie syndrome and attenuated Scheie syndrome). We aim to identify the genetic variants in MPS I patients and to investigate the effect of the novel splice site mutation on splicing of IDUA- mRNA variability using bioinformatics tools. METHODS: The IDUA mutations were determined in four MPS I patients from four families from Northern Tunisia, by amplifying and sequencing each of the IDUA exons and intron-exon junctions. RESULTS: One novel splice site IDUA mutation, c.1650 + 1G > T in intron 11 and two previously reported mutations, p.A75T and p.R555H, were detected. The patients in families 1 and 2 who have the Hurler phenotype were homozygotes for the novel splice site mutation c.1650 + 1G > T. The patient in family 3, who also had the Hurler phenotype, was a compound heterozygote for the novel splice site mutation c.1650 + 1G > T and for the previously reported missense mutation p.A75T. The patient in family 4 who had the Hurler-Scheie phenotype was a compound heterozygote for the novel splice site mutation c.1650 + 1G > T and for the previously reported missense mutation p.R555H. In addition, four known IDUA polymorphisms were identified. Bioinformatics tools allowed us to associate the variant c.1650 + 1G > T with the severe clinical phenotype of MPS I. This variant affects the essential nucleotide + 1 (G to T) of the donor splice site of IDUA intron 11. The G > T in intron 11 leads to wild type donor site broken with minus 19.97% value compared to normal value with 0%, hence the new splice site acceptor has plus 5.59%. CONCLUSIONS: The present findings indicate that the identified mutations facilitate the accurate carrier detection (genetic counseling of at-risk relatives) and the molecular prenatal diagnosis in Tunisia.

Treatment-naïve Gaucher disease patients achieve therapeutic goals and normalization with velaglucerase alfa by 4years in phase 3 trials.

Gaucher disease is an inherited metabolic disease characterized by ß-glucocerebrosidase deficiency and commonly treated with enzyme replacement therapy (ERT). The efficacy of ERT with velaglucerase alfa was assessed based on the achievement of published therapeutic goals and the normalization of disease parameters in 39 treatment-naïve patients with type 1 Gaucher disease, 6 to 62years of age, enrolled in phase 3 clinical trials. After 4years of ERT, therapeutic goals for thrombocytopenia and splenomegaly had been achieved in 100% of patients; goals for anemia and hepatomegaly had been achieved in 95% and 94% of patients, respectively. Consistent with the goal for bone mineral density, lumbar spine bone density improved in 87% of patients ≥18years of age. At year 4, compared with clinical ranges for healthy individuals, 86% of patients with a low baseline hemoglobin concentration had normalized, 60% with a low baseline platelet count had normalized, 67% with baseline splenomegaly had normalized, 58% with hepatomegaly had normalized, and lumbar spine bone density had normalized in 53% of adults. The decade-old therapeutic goals do not reflect the potential for normalization of clinical parameters in ERT-treated patients. Goals consistent with normalization or near-normalization should be considered. ClinicalTrials.gov identifiers: NCT00430625, NCT00553631, NCT00635427.

Results From a 12-Month Open-Label Phase 1/2 Study of Velaglucerase Alfa in Children and Adolescents With Type 3 Gaucher Disease

Abstract Gaucher disease (GD) is an autosomal recessive lipid storage disorder, caused by deficient activity of the lysosomal enzyme b-glucocerebrosidase, resulting in accumulation of glucocerebroside in tissue macrophages. HGT-GCB-068 was an open-label study designed to explore the efficacy and safety of velaglucerase alfa in children and adolescents with type 3 GD, a neuronopathic form of the disease. Six treatment-naive patients received infusions of velaglucerase alfa every other week at 60 U/kg over 12 months. Velaglucerase alfa demonstrated a favorable tolerability profile, and 1 infusion-related reaction (headache) was the only drug-related adverse event reported. Numerical increases from baseline in hematological parameters and decreases in visceral parameters were seen at 12 months. http://ClinicalTrials.gov identifier NCT01685216.

Development of anti-velaglucerase alfa antibodies in clinical trial-treated patients with Gaucher disease.

Anti-drug antibodies may develop with biological therapies, possibly leading to a reduction of treatment efficacy and to allergic and other adverse reactions. Patients with Gaucher disease were tested for anti-drug antibodies every 6 or 12weeks in clinical studies of velaglucerase alfa enzyme replacement therapy, as part of a range of safety endpoints. In 10 studies between April 2004 and March 2015, 289 patients aged 2-84years (median 43years) were assessed for the development of anti-velaglucerase alfa antibodies. Sixty-four patients were treatment-naïve at baseline and 225 patients were switched to velaglucerase alfa from imiglucerase treatment. They received velaglucerase alfa treatment for a median of 36.4weeks (interquartile range 26.4-155.4weeks). Four patients (1.4%) became positive for anti-velaglucerase alfa IgG antibodies, two of whom had antibodies that were neutralizing in vitro, but there were no apparent changes in patients' platelet counts, hemoglobin levels or levels of CCL18 and chitotriosidase, suggestive of clinical deterioration after anti-velaglucerase alfa antibodies were detected, and no infusion-related adverse events were reported. Less than 2% of patients exposed to velaglucerase alfa tested positive for antibodies and there was no apparent correlation between anti-velaglucerase alfa antibodies and adverse events or pharmacodynamic or clinical responses.

Cause of death in patients with chronic visceral and chronic neurovisceral acid sphingomyelinase deficiency (Niemann-Pick disease type B and B variant): Literature review and report of new cases.

BACKGROUND: Acid sphingomyelinase deficiency (ASMD), [Niemann-Pick Disease Types A and B (NPD A and B)], is an inherited metabolic disorder resulting from deficiency of the lysosomal enzyme acid sphingomyelinase. Accumulation of sphingomyelin in hepatocytes, reticuloendothelial cells, and in some cases neurons, results in a progressive multisystem disease that encompasses a broad clinical spectrum of neurological and visceral involvement, including: infantile neurovisceral ASMD (NPD A) that is uniformly fatal by 3years of age; chronic neurovisceral ASMD (intermediate NPD A/B; NPD B variant) that has later symptom onset and slower neurological and visceral disease progression; and chronic visceral ASMD (NPD B) that lacks neurological symptoms but has significant disease-related morbidities in multiple organ systems. The purpose of this study was to characterize disease-related morbidities and causes of death in patients with the chronic visceral and chronic neurovisceral forms of ASMD. METHODS: Data for 85 patients who had died or received liver transplant were collected by treating physicians (n=27), or abstracted from previously published case studies (n=58). Ages at symptom onset, diagnosis, and death; cause of death; organ involvement, and morbidity were analyzed. RESULTS: Common disease-related morbidities included splenomegaly (96.6%), hepatomegaly (91.4%), liver dysfunction (82.6%), and pulmonary disease (75.0%). The overall leading causes of death were respiratory failure and liver failure (27.7% each) irrespective of age. For patients with chronic neurovisceral ASMD (31.8%), progression of neurodegenerative disease was a leading cause of death along with respiratory disease (both 23.1%) and liver disease (19.2%). Patients with chronic neurovisceral disease died at younger ages than those with chronic visceral disease (median age at death 8 vs. 23.5years). CONCLUSIONS: The analysis emphasizes that treatment goals for patients with chronic visceral and chronic neurovisceral ASMD should include reducing splenomegaly and improving liver function and respiratory status, with the ultimate goal of decreasing serious morbidity and mortality.

Genetic basis of cystinosis in Tunisian patients: Identification of novel mutation in CTNS gene.

Nephropathic cystinosis (NC) is an autosomal recessive disorder characterized by defective transport of cystine across the lysosomal membrane and resulting in renal, ophthalmic, and other organ abnormalities. Mutations in the CTNS gene cause a deficiency of the transport protein, cystinosin. This study was performed to investigate mutations of the CTNS gene in three Tunisian families with NC. Polymerase chain reaction (PCR), ARMS multiplex PCR and direct sequencing were performed for molecular characterization of the CTNS gene in 3 unrelated Tunisian patients and their parents. Based on family history, prenatal diagnosis (PND) was performed in fetal DNA isolated from chorionic villi obtained at 10-12  weeks of gestation. None of the patients showed the most common 57-kb deletion in heterozygous or homozygous status. One patient was homozygous for the previously reported mutation c.1515G > A (p.G308R). One patient presented the novel gross deletion of 20,327 bp. One was homozygote for the previously reported mutation c.771_793del (p.Gly258Serfs*30). In addition, eight polymorphisms were identified in the 3 patients and their parents. The prenatal diagnosis in one family showed that the fetus DNA was heterozygous for the c.771_793del (p.Gly258Serfs*30) mutation. This study expands the mutational and population spectrum of NC, representing the first molecular diagnosis of NC in Tunisian population. The mutation screening of the CTNS gene was used for prenatal diagnosis to prevent and/or limit this inheritable disease in our country where the families are particularly large and have a high rate of consanguinity.

Enzyme replacement therapy with velaglucerase alfa in Gaucher disease: Results from a randomized, double-blind, multinational, Phase 3 study.

Type 1 Gaucher disease (GD1), resulting from glucocerebrosidase deficiency, leads to splenomegaly, hepatomegaly, anemia, thrombocytopenia, and bone involvement. Current standard treatment is enzyme replacement therapy. Velaglucerase alfa is an enzyme replacement product for GD1, with the same amino acid sequence as naturally occurring human glucocerebrosidase. This multinational, Phase 3 trial evaluated the efficacy and safety of two doses of velaglucerase alfa in 25 treatment-naïve, anemic patients with GD1 (4-62 years of age), randomized to intravenous velaglucerase alfa 60 U/kg (n=12) or 45 U/kg body weight (n=13) every other week for 12 months. The primary endpoint was change from baseline in hemoglobin concentration in the 60 U/kg arm. At 12 months, mean hemoglobin concentrations increased from baseline [60 U/kg: +23.3%; +2.43 g/dL (P<0.001); 45 U/kg: +23.8%; +2.44 g/dL (P<0.001)], as did mean platelet counts [60 U/kg: +65.9%; +50.9 × 10(9) /L (P=0.002); 45 U/kg: +66.4%; +40.9 × 10(9) /L(P=0.01)]. Mean splenic volume decreased from baseline [60 U/kg: -50.4%, from 14.0 to 5.8 multiples of normal (MN) (P=0.003); 45 U/kg: -39.9%, from 14.5 to 9.5 MN (P=0.009)]. No drug-related serious adverse events or withdrawals were observed. One patient developed antibodies. Velaglucerase alfa was generally well tolerated and effective for adults and children with GD1 in this study. All disease-specific parameters measured demonstrated clinically meaningful improvements after 12 months.

Mucopolysaccharidosis type I: molecular characteristics of two novel alpha-L-iduronidase mutations in Tunisian patients.

BACKGROUND: Mucopolysaccharidosis type I (MPS I) is an autosomal storage disease resulting from defective activity of the enzyme α-L-iduronidase (IDUA). This glycosidase is involved in the degradation of heparan sulfate and dermatan sulfate. MPS I has severe and milder phenotypic subtypes. AIM OF STUDY: This study was carried out on six newly collected MPS I patients recruited from many regions of Tunisia. PATIENTS AND METHODS: Mutational analysis of the IDUA gene in unrelated MPS I families was performed by sequencing the exons and intron-exon junctions of IDUA gene. RESULTS: Two novel IDUA mutations, p.L530fs (1587_1588 insGC) in exon 11 and p.F177S in exon 5 and two previously reported mutations p.P533R and p.Y581X were detected. The patient in family 1 who has the Hurler phenotype was homozygous for the previously described nonsense mutation p.Y581X.The patient in family 2 who also has the Hurler phenotype was homozygous for the novel missense mutation p.F177S. The three patients in families 3, 5 and 6 were homozygous for the p.P533R mutation. The patient in family 4 was homozygous for the novel small insertion 1587_1588 insGC. In addition, eighteen known and one unknown IDUA polymorphisms were identified. CONCLUSION: The identification of these mutations should facilitate prenatal diagnosis and counseling for MPS I in Tunisia.