Percorrer por autor "Santos, J.I."
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- An Antisense Oligonucletide based therapy for a rare disease: in vitro and in vivo studiesPublication . Gonçalves, M.; Matos, L.; Santos, J.I.; Coutinho, M.F.; Prata, M.J.; Pires, M.J.; Oliveira, P.A.; Alves, SandraMucolipidosis type II (ML II) is a Lysosomal Storage Disorder caused by the deficiency of the enzyme GlcNAc-1-phosphotransferase. This enzyme is responsible for the addition of the mannose-6-phosphate marker to lysosomal enzymes allowing their targeting to lysosomes. From the several ML II mutations, the deletion of two nucleotides from GNPTAB exon 19 (c.3503_3504del) is the most frequent, making it a good target for a mutation specific therapy. In this study, we explored an innovative therapeutic strategy based on the use of antisense oligonucleotides (ASOs) for ML II. In a previous study1 on fibroblasts from ML II patients, ASOs were used to skip exon 19 of the GNPTAB pre-mRNA, successfully resulting in the production of an in-frame mRNA. Currently, our objective is to evaluate the therapeutic potential of this approach, both in vitro in C57BL/6 fibroblasts and in vivo in C57BL/6 mice.
- Can an Antisense Oligonucleotide Exon Skipping Rewrite the Story of N-Acetylglucosamine-1-Phosphotransferase Deficiency?Publication . Gonçalves, M.; Moreira, L.; Encarnação, M.; Gaspar, P.; Duarte, A.J.; Santos, J.I.; Coutinho, M.F.; Prata, M.J.; Omidi, M.; Pohl, S.; Silva, F.; Oliveira, P.; Matos, L.; Alves, S.Mucolipidosis II (ML II) is a Lysosomal Storage Disorder caused by N-acetylglucosamine-1-phosphotransferase (GlcNAc-PT) deficiency, which impairs the trafficking of lysosomal hydrolases. Of all ML II mutations, c.3503_3504delTC in GNPTAB exon 19 is the most frequent, making it a good target for a personalized therapy. Here, we explored an innovative therapeutic strategy based on the use of antisense oligonucleotides (ASOs). Previously, in ML II patients’ fibroblasts, we tested ASOs to induce exon 19 skipping in pre-mRNA, successfully generating an in-frame mRNA (Matos et al., 2020). Now, our aim is to determine whether this in-frame transcript leads to increased GlcNAc-PT levels improving ML II cellular phenotype.
- Development of RNA based approaches to exploit alternative therapies for Lysosomal Storage DiseasesPublication . Matos, L.; Santos, J.I.; Rocha, M.; Coutinho, M.F.; Gaspar, P.; Voltolini Velho, R.; Braulke, T.; Prata, M.J.; Alves, S.Treatment strategies such enzyme-replacement therapy and substrate reduction, among others, are available for some Lysosomal Storage Diseases, yet still with some limitations. In recent years, the RNA molecule became one of the most promising targets for therapeutic intervention and currently, a large number of RNA-based therapies are being investigated at the basic research level and in late-stage clinical trials. Actually, some of them are already approved for medical use (e.g. Spinal muscular atrophy and Duchenne muscular dystrophy). RNA-based approaches can act at pre-mRNA level (by splicing modulation/correction using antisense oligonucleotides or U1snRNA vectors), at mRNA level (inhibiting gene expression by siRNAs and antisense oligonucleotides) or at DNA level (by editing mutated sequences through the use of CRISPR/Cas). Currently, we are developing some of these therapeutic approaches for LSDs. Two main research lines are ongoing: one involves the use of antisense U1 snRNAs to overcome the effect of a splice site mutation causing Mucopolysaccharidosis type IIIC and the other is based on the use of splice switching oligonucleotides to induce the skipping and consequently circumvent the effects of the most common causal mutation in Mucolipidosis type II.
- An engineered U1 snRNA-based therapeutic approach can efficiently rescue a 5’ splice site mutation causing Mucolipidosis type IIIPublication . Peretto, L.; Gonçalves, M.; Santos, J.I.; Duarte, A.J.; Moreira, L.; Encarnação, M; Coutinho, M.F.; Pinotti, M.; Balestra, D.; Alves, S.; Matos. L.A significant number of splicing mutations have been identified in Lysosomal Storage Disorders (LSDs). Mucolipidosis III (ML III) is a LSD caused by GlcNAc-1-phosphotransferase deficiency, which impairs the trafficking of lysosomal hydrolases. 10% of the genetic defects in ML III are splicing mutations, and around 45% affect 5' splice-sites (ss) thus constituting a good target for mutation specific therapies. The use of engineered U1 snRNA (either modified U1 snRNAs or exon-specific U1s - ExSpeU1s) has been applied as a potential therapeutic strategy to correct 5’ss defects. Here we used engineered U1 snRNAs to correct the GNPTAB exon 17 skipping caused by the 5’ss mutation (c.3335+6T>G) found in a ML III patient. First, we performed transfection of exon-trapping minigenes expressing exon 17 surrounded by a portion of introns - pGNPTAB_WT and pGNPTAB_+6, in HEK293T cells to analyze if they reproduce the WT and mutant splicing patterns. Then, to evaluate the potential of 2 modified U1’s, 3 ExSpeU1s and 2 modified U6’s to restore mRNA splicing, these vectors were cotransfected into HEK293T cells along with the mutant +6 minigene as well as electroporated in patient’s fibroblasts. Then, cells were harvested, and RT-PCR analysis was performed. Both minigenes reproduced the control or ML III patient cDNA’s splicing patterns, thus, different concentrations of the modified U1’s and ExSpeU1s were tested together with the mutant minigene. The cDNA analysis showed almost 100% of exon 17 inclusion when one of the ExSpeU1s, was overexpressed in HEK293T cells. The combination of the 2 modified U6’s with the modified U1’s or the ExSpeU1s allowed exon 17 inclusion at some extent, but not as effectively as with the best ExSpeU1 alone. The electroporation of the 2 modified U1’s and of the 3 ExSpeU1s was done, and the cDNA analysis of patient’s fibroblasts treated with 2 ExSpeU1s (ExSpeU1 int17-1 or int17-2) showed around 35% and 15% of exon 17-including transcripts, respectively. To confirm these results, given that the lentiviral transduction is a more efficient delivery technique than electroporation, the gene cassettes of the 2 most promising ExSpeU1s were cloned in a lentivirus vector and after obtaining the viral mediums, their transduction in patient’s fibroblasts is being optimized. The cDNA analysis of preliminary experiments is still ongoing. In conclusion, we have developed an RNA therapy based on engineered U1 snRNAs for a ML III 5’ss mutation. We showed that an ExSpeU1 (binding downstream of the mutated 5´ss) can restore proper exon 17 definition in vitro, opening the opportunity for a personalized therapeutic intervention.
- An engineered U1 snRNA-based therapeutic approach can efficiently rescue a 5’ splice site mutation causing Mucolipidosis type IIIPublication . Peretto, L.; Gonçalves, M.; Santos, J.I.; Duarte, A.J.; Moreira, L.; Encarnação, M.; Coutinho, M.F.; Pinotti, M.; Balestra, D.; Alves, S.; Matos, L.A significant number of splicing mutations have been identified in Lysosomal Storage Disorders (LSDs). Mucolipidosis III (ML III) is a LSD caused by GlcNAc-1-phosphotransferase deficiency, which impairs the trafficking of lysosomal hydrolases. 10% of the genetic defects in ML III are splicing mutations, and around 45% affect 5' splice-sites (ss) thus constituting a good target for mutation specific therapies. The use of engineered U1 snRNA (either modified U1 snRNAs or exon-specific U1s - ExSpeU1s) has been applied as a potential therapeutic strategy to correct 5’ss defects. Here we used engineered U1 snRNAs to correct the GNPTAB exon 17 skipping caused by the 5’ss mutation (c.3335+6T>G) found in a ML III patient.
- Genetically Modulated Substrate Reduction Therapy for Sanfilippo syndrome – proof of principlePublication . Santos, J.I.; Coutinho, Maria Francisca; Gaspar, P.; Alves, S.Introduction: Mucopolysaccharidosis type III (MPS III) refers to a group of five autosomal recessive neurodegenerative lysosomal storage disorders caused by the incomplete lysosomal degradation of the heparan sulphate (HS) that accumulates in patient cells and triggers disease. The main characteristic of this disease is the degeneration of the central nervous system, resulting in mental retardation and hyperactivity. Currently, there is no effective therapy available, with treatment limited to clinical management of neurological symptoms. Methods: Taking advantage of the RNA interference (RNAi) technology potential, we have designed and assayed a specific siRNA targeting an early stage of the HS biosynthetic cascade (XYLT1) in order to promote an effective reduction of the accumulating substrate. Fibroblasts from MPS III patients were transfected with the designed siRNA. Total RNA was extracted and target mRNA levels evaluated through real-time PCR. The effect on GAGs accumulation was quantified over time using a modified 1,9-dimethylmethylene blue assay. Results: Proof of principle on the effect of siRNA targeting XYLT1 was achieved for two independent control cell lines, with 8-12 fold decreases on the target mRNA levels, after 24h of incubation with concentrations of 20nM of each siRNA. Subsequent analysis on the effect of the same siRNA on MPS III cell lines resulted in significant lower expression of XYLT1 in types A, B and C, after 24-48h of siRNA incubation. Studies on type B are also ongoing. For types C and D, we have already assessed the treatment effect on storage and observed a significant reduction (50-70%) on the total GAGs levels. Conclusions: The effect of siRNA targeting XYLT1 was achieved, resulting in significant lower levels of XYLT1 mRNA. Studies on MPS IIIB are ongoing. Moreover, a significant reduction on GAGs’ accumulation was observed, and we are currently addressing this storage in the remaining MPS III cell lines.
- Less is More: Substrate Reduction Therapy for Lysosomal Storage DisordersPublication . Coutinho, Maria Francisca; Santos, J.I.; Alves, SandraThe concept of enzyme replacement as a potential therapeutic approach to ameliorate lysosomal storage disorders (LSDs) is virtually as old as the concept of LSD itself. In fact, both concepts were established right after the first enzymatic deficiency underlying an LSD was described, and enzyme replacement therapy (ERT) remained the golden standard for LSD treatment for years. Nevertheless, its ineffectiveness to correct brain pathology, together with its high cost and lifelong dependence prompted the search for additional therapeutic approaches, which are currently being investigated: chaperone therapy; gene enhancement and gene therapy. Still, no matter how effective the treatment or cutting-edge the technology used in any of these cases, the underlying rationale is virtually the same: an attempt to provide or enhance the activity of the missing enzyme. Yet, 20 years now, an alternative approach arose. Its theoretical basis was established in 1996, when Norman Radin came up with an academic prediction that Gaucher disease (GD) patients could also be treated with a drug able to slow the synthesis of glucosylceramide, the lipid that accumulates in this disorder. Unfortunately, the lack of suitable GD animal models made it difficult to adequately test his hypothesis by the time it was published. Still, the grounds were seeded for the appearance of a second line of work on the LSDs therapeutics field, whose aim was to prevent storage not by correcting the original enzymatic defect but, instead, by decreasing the biosynthesis of the substrate that is accumulated. This approach was called substrate reduction therapy (SRT) and will be the major focus of this talk. Special attention will be given to the most recent advances in the field, introducing the concept of genetic SRT (gSRT), which is based on the use of RNA-degrading technologies (RNA interference and single-stranded antisense oligonucleotides) to efficiently promote substrate reduction by decreasing its synthesis rate. In summary, we will review and compare the results from different teams on the use of gene suppression technologies as tools to achieve substrate reduction.
- Molecular Characterization of a Novel Mucopolysaccharidosis (MPS) type VI-causing Mutation – Indirect Proof of Principle on its PathogenicityPublication . Coutinho, Maria Francisca; Encarnação, M.; Santos, J.I.; Alves, S.Introduction: With its unprecedented throughput, scalability and speed, next-generation sequencing (NGS) is revolutionizing clinical research. Targeted sequencing in particular is now available in many labs. Still, whenever a novel variant is detected, its pathogenicity must be carefully assessed and every now and again, a case pops up to highlight how tricky and delicate this process can be. Here we present a case of a molecular diagnosis of a patient with a clinical suspicion of MPS type VI, where even though the causal mutation was easy to detect by both Sanger and NGS, only through indirect studies could we present proof of principle on its pathogenicity.
- Mucopolysaccharidoses type III: toward a siRNA-containing nanoparticle targeted to brain cellsPublication . Coutinho, M.F.; Santos, J.I.; Gaspar, P.; Alves, S.The classical therapeutic approach for LSD, enzyme replacement therapy, would hardly rise as a potentially successful tool to reduce the disease burden in MPS III patients, as it is long known to have no impact on neuropathology. A tempting alternative, however, would be to block substrate accumulation upstream, by decreasing its synthesis. That concept is known as substrate reduction therapy (SRT). Having this in mind, we designed an RNA-based strategy based upon the selective downregulation of one gene involved in the very early stages of the glycosaminoglycans’ (GAG) biosynthethic cascade. Our goal is to promote an effective reduction of the accumulating substrate, ultimately decreasing or delaying MPS’ symptoms. As tools to achieve substrate reduction, we are evaluating a specific type of antisense oligonucleotides, able to trigger a naturally-occurring post-transcriptional gene silencing process called RNA interference: the small interfering RNAs (siRNAs). So far, the obtained results are quite promising with marked decreases of the target mRNA levels in all tested cell lines (MPS IIIA, IIIC and IIID patients’ fibroblasts). Currently, we are evaluating the effect of that decrease on the overall storage of GAGs 7 days post-transfection, also with promising results. Here we present an overview on the current results of this project, while discussing its next steps, namely the development and evaluation of vectors for in vivo delivery. Our goal is to develop targeted stable nucleic acid lipid particles (t-SNALPs) coupled with different ligands, which promote cell uptake of the ‘anti-GAG’ siRNAs in a variety of cells, including neurons.
- The disease modelling value of a folklore FAIRYtale: SHEDing light over a special group of genetic disordersPublication . Carvalho, S.; Santos, J.I.; Moreira, L.; Gaspar, P.; Gonçalves, M.; Encarnação, M.; Ribeiro, D.; Duarte, A.; Prata, M.J.; Coutinho, M.F.; Alves, SandraThe problem we are addressing: Despite extensive research, the links between accumulation of glycosaminoglycans (GAGs) and the clinical features seen in patients suffering from various forms of Mucopolysaccharidoses (MPSs) have yet to be further elucidated. These Lysosomal Storage Diseases (LSDs) present symptoms, which may (or may not) include critical musculoskeletal and cardiovascular alterations, respiratory problems, and serious neurological dysfunctions. The skeletal and brain systems are the hardest ones to access and, consequently, those in greatest need of additional knowledge and novel therapeutic solutions.