Marina Siebert

Identification of miRNAs that modulate glucocerebrosidase activity in Gaucher disease cells

Gaucher disease is an autosomal recessive disorder caused by deficiency of the enzyme glucocerebrosidase. Although it is a monogenic disease, there is vast phenotypic heterogeneity, even among patients with the same genotype. MicroRNAs (miRNAs) are small non-coding RNAs involved in many biological processes and diseases. To determine whether miRNAs can affect glucocerebrosidase activity, we performed a screen of 875 different miRNA mimics. The screen was performed using Gaucher fibroblasts, and glucocerebrosidase activity was used as the initial outcome parameter. We found several miRNAs that either up- or down-regulated glucocerebrosidase activity. In follow-up assays, we confirmed that one specific miRNA (miR-127–5p) down-regulated both glucocerebrosidase activity and protein levels by down-regulation of LIMP-2, the receptor involved in proper trafficking of glucocerebrosidase from the endoplasmic reticulum to the lysosome. A conditioned media assay demonstrated that cells treated with this miRNA secreted glucocerebrosidase into the extracellular environment, supporting impaired LIMP-2 function. Two other miRNAs, miR-16–5p and miR-195–5p, were found to up-regulate glucocerebrosidase activity by greater than 40% and to enhance expression and protein levels of the enzyme. In conclusion, we show that miRNAs can alter glucocerebrosidase activity in patient cells, indicating that miRNAs can potentially act as modifiers in Gaucher disease.

Novel Mutations in the Glucocerebrosidase Gene of Brazilian Patients with Gaucher Disease

Gaucher disease (GD) is an autosomal recessive disorder resulting from glucocerebrosidase (GC) deficiency due to mutations in the gene (GBA) coding for this enzyme. We have developed a strategy for analyzing the entire GBA coding region and applied this strategy to 48 unrelated Brazilian patients with GD. We used long-range PCR, genotyping based on the Taqman® assay, nested PCR, and direct DNA sequencing to define changes in the gene. We report here seven novel mutations that are likely to be harmful: S125N (c.491G>A), F213L (c.756T>G), P245T (c.850C>A), W378C (c.1251G>C), D399H (c.1312G>C), 982-983insTGC (c.980_982dupTGC), and IVS10+1G>T (c.1505+1G>T). The last alteration was found as a complex allele together with a L461P mutation. We also identified 24 different mutations previously reported by others. G377S was the third most frequent mutation among the patients included in this study, after N370S and L444P. Therefore, this mutation needs be included in preliminary screens of Brazilian GD patients. The identification of mutant GBA alleles is crucial for increasing knowledge of the GBA mutation spectrum and for better understanding of the molecular basis of GD.

Genotypic characterization of Brazilian patients with infantile and juvenile forms of metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder inherited as an autosomal recessive trait. MLD is caused by the deficiency of arylsulfatase A (ARSA), a lysosomal enzyme that catalyzes the first step in the degradation of sulfated glycolipids, which are essential components of the myelin sheet. Notably, between 7% and 15% of healthy individuals show in vitro deficiency of ARSA, a condition called ARSA pseudodeficiency (ARSA-PD). To date, 151 ARSA-MLD mutations have been reported in the gene encoding ARSA (ARSA), among which IVS2+1G>A and P426L occur at high frequencies in most of the studied populations. The aim of this work was to identify ARSA mutant alleles in a cohort of 27 unrelated Brazilian MLD patients. The most frequent ARSA-MLD mutation, IVS2+1G>A, and the ARSA-PD polymorphisms, N350S and 1524+95A>G, were detected using real-time PCR, while the remaining mutations were detected using direct sequencing of ARSA. In concordance with previous reports, IVS2+1G>A and P426L were the most common ARSA-MLD mutations in our cohort of MLD patients, found at frequencies of 0.05 and 0.08, respectively. Interestingly, two mutations previously reported as rare, 103_110del8 and 1190_1191insC, were found at higher frequencies in our cohort of MLD patients, 0.08 and 0.06, respectively. Additionally, 11 other rare ARSA-MLD mutations were found at lower frequencies in our cohort of MLD patients. To our knowledge, this is the first systematic genotypic characterization of MLD patients from Latin America. This work highlights the genetic heterogeneity of MLD, and supports genotype-phenotype associations, which become more important as specific treatments are being developed for this devastating disorder.

Glycosylation is crucial for a proper catalytic site organization in human glucocerebrosidase

Gaucher disease, an autosomal recessive disorder, is caused by a deficiency of glucocerebrosidase (GCase) enzyme, a peripheral membrane-associated glycoprotein that hydrolyses glucosylceramide in lysosomes. Glycosylation is essential for the development of a catalytically active enzyme, specifically in the first site, located at Asn19. However, both the molecular basis of the relevance of N-glycosylation over GCase activity and the effects of glycosylation over its structure and dynamics are still not fully understood. Thus, the present work evaluated GCase enzyme in increasing glycosylation content using triplicate unbiased molecular dynamics simulations. Accordingly, the N-linked glycan chains caused local conformational stabilization effects over the protein, as well as in regions flanking the enzyme catalytic dyad. In the case of the Asn19-linked glycan, it also occurred around region 438–444, where one of the most prevalent GCase mutations is found. Markedly, an increasing catalytic dyad organization was related to increasing glycosylation contents, offering the first atomic-level explanation for the experimental observation that GCase activity is controlled by glycosylation, especially at Asn19.

The prognostic value of the serum ferritin in a southern Brazilian cohort of patients with Gaucher disease

Abstract The clinical utility of serum ferritin as a biomarker of disease severity and prognosis in Gaucher disease (GD) is still debated. Here, we aimed to evaluate ferritin and its relation to clinicolaboratory parameters of GD patients seen at the Reference Center for Gaucher Disease of Rio Grande do Sul, Brazil, so as to gather evidence on the utility of ferritin as a biomarker of this condition. A retrospective chart review was performed collecting pre-and posttreatment data from GD patients. Eighteen patients with ferritin levels available before and after treatment were included in the study. Nine of these participants were males, and seventeen had type I GD. All patients were given either enzyme replacement (n = 16) or substrate reduction therapy (n = 2), and ferritin was found to decrease from 756 [318-1441] ng/mL at baseline to 521 [227-626] ng/mL (p=0.025) after 28.8 month soft treatment. Serum ferritin levels did not correlate with measures of disease severity, but showed an association with age at onset of treatment (ρ= 0.880; n = 18; p < 0.001). In conclusion, although serum ferritin did not correlate with disease severity, after a median 28.8 months of treatment, clinical outcomes had clearly improved, and ferritin levels had decreased.

Genetic profile of Brazilian patients with dystrophinopathies

Different types of mutations in the DMD gene underlie Duchenne muscular dystrophies (DMD) and Becker muscular dystrophies (BMD). Large deletions and duplications are the most frequent causative genetic alterations worldwide, but little is known about DMD/BMD genetic profile in Brazil. Hence, we recruited patients with DMD and BMD from 8 neuromuscular reference centers along the country, and performed a comprehensive molecular investigation that included Multiplex Ligation‐dependent Probe Amplification and Next generation sequencing (NGS) analyses. We evaluated 199 patients from 177 unrelated families: 166 with DMD, 32 with BMD and 1 1.5u2009years old asymptomatic patient with persistent hiperCKemia. Overall, large deletions (58.2%) followed by nonsense mutations (12.4%) and large duplications (11.3%) were the most frequent variants in Brazilian families. Large deletions were less frequent in BMD than in DMD (44.8% vs 60.8%). We identified 19 new DMD variants. Nonsense mutations were significantly more frequent in patients from northeastern region than from southern/southeastern regions of Brazil (27.7% vs 8.5%, Pu2009<u2009.05). Genetic profile of Brazilian patients with DMD/BMD is similar to previously reported cohorts, but it is not uniform across the country. This information is important to plan rational clinical care for patients in face of the new coming mutation‐specific therapies.

Contribuição da análise molecular do gene regulador da condutância transmembrana na fibrose cística na investigação diagnóstica de pacientes com suspeita de fibrose cística leve ou doença atípica

OBJECTIVE: To evaluate the diagnostic contribution of molecular analysis of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in patients suspected of having mild or atypical cystic fibrosis (CF). METHODS: This was a cross-sectional study involving adolescents and adults aged ≥ 14 years. Volunteers underwent clinical, laboratory, and radiological evaluation, as well as spirometry, sputum microbiology, liver ultrasound, sweat tests, and molecular analysis of the CFTR gene. We then divided the patients into three groups by the number of mutations identified (none, one, and two or more) and compared those groups in terms of their characteristics. RESULTS: We evaluated 37 patients with phenotypic findings of CF, with or without sweat test confirmation. The mean age of the patients was 32.5 ± 13.6 years, and females predominated (75.7%). The molecular analysis contributed to the definitive diagnosis of CF in 3 patients (8.1%), all of whom had at least two mutations. There were 7 patients (18.9%) with only one mutation and 26 patients (70.3%) with no mutations. None of the clinical characteristics evaluated was found to be associated with the genetic diagnosis. The most common mutation was p.F508del, which was found in 5 patients. The combination of p.V232D and p.F508del was found in 2 patients. Other mutations identified were p.A559T, p.D1152H, p.T1057A, p.I148T, p.V754M, p.P1290P, p.R1066H, and p.T351S. CONCLUSIONS: The molecular analysis of the CFTR gene coding region showed a limited contribution to the diagnostic investigation of patients suspected of having mild or atypical CF. In addition, there were no associations between the clinical characteristics and the genetic diagnosis.

Use of a multiplex ligation-dependent probe amplification method for the detection of deletions/duplications in the GBA1 gene in Gaucher disease patients

Gaucher disease (GD) is caused by the deficient activity of β-glucocerebrosidase due to pathogenic mutations in the GBA1. This gene has a pseudogene (GBAP) with 96% of sequence homology. Recombination (Rec) events in the GBA1 seem to be facilitated by an increased degree of homology and proximity to the GBAP. The objectives of this study were to validate the P338-X1 GBA kit (MRC-Holland) for Multiplex Ligation-dependent Probe Amplification (MLPA) and to detect larger deletions/duplications present in GBA1 in GD patients from Brazil. Thirty-three unrelated Brazilian GD patients, previously genotyped by the Sanger method (both pathogenic alleles identified=29 patients, only one allele identified=3 patients, no pathogenic alleles identified=1 patient), were evaluated by the MLPA assay. MLPA was compatible with the previous results obtained by Sanger sequencing and identified an additional allele (a heterozygous deletion in intron 7 in one patient with only one mutation identified by Sanger). Our data suggest that, although larger deletions/duplications do not appear to be frequent in GD, the P338-X1 GBA kit for MLPA appears to be a good method for GBA1 analysis. Additional investigations should be performed in order to characterize the remaining four uncharacterized alleles of our sample.

Clinical and molecular characterization of hereditary spastic paraplegias: A next-generation sequencing panel approach

BACKGROUNDnMolecular diagnosis of hereditary spastic paraplegias (HSP) is a difficult task due to great clinical and genetic heterogeneity. We aimed to characterize clinical and molecular findings of HSP families from Rio Grande do Sul, Brazil; and to evaluate the diagnostic yield of a next-generation sequencing (NGS) panel with twelve HSP-related genes.nnnMETHODSnA consecutive series of HSP index cases with familial recurrence of spasticity, consanguinity or thin corpus callosum (TCC) were included in this cross-sectional study.nnnRESULTSnAmong the 29 index cases, 51.7% (15/29) received at least a likely molecular diagnosis, and 48.3% (14/29) a defined diagnosis. NGS panel diagnostic yield was 60% for autosomal dominant HSP (6/10, all SPG4), 47.4% for autosomal recessive HSP (9/19: 5 SPG11, 2 SPG7, 1 SPG5 and 1 cerebrotendinous xanthomatosis), and 50% for patients with TCC (3/6, all SPG11). Remarkably, 2/6 SPG11 patients presented keratoconus, and tendon xanthomas were absent in the patient with cerebrotendinous xanthomatosis.nnnCONCLUSIONnA likely molecular diagnosis was obtained for more than half of families with the NGS panel, indicating that this approach could be employed as a first-line investigation for HSP. SPG4 is the most frequent form of autosomal dominant and SPG11 of autosomal recessive HSP in Southern Brazil.

Draft genome sequence of a GES-5-producing Serratia marcescens isolated in southern Brazil

Serratia marcescens is a Gram-negative rod intrinsically resistant to polymyxins and usually associated with wound, respiratory and urinary tract infections. The whole genome of the first GES-5-producing S. marcescens isolated from a Brazilian patient was sequenced using Ion Torrent PGM System. Besides blaGES-5, we were able to identify genes encoding for other β-lactamases, for aminoglycoside modifying enzymes and for an efflux pump to tetracyclines.