DGH - Posters/abstracts em congressos nacionais
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- 3-Methylcrotonyl CoA Carboxylase Deficiency: Disorder or Just a Biochemical Phenotype?Publication . Fonseca, Helena; Bueno, Maria; Sousa, Carmen; Marcão, Ana; Lopes, Lurdes; Rocha, Hugo; Vilarinho, LauraIntroduction: 3-methylcrotonyl-CoA carboxylase deficiency (MCCD) was considered extremely rare before newborn screening (NBS) was undertaken but is now found in a number of asymptomatic babies or sometimes their mothers. This disorder of leucine metabolism, is the commonest organic aciduria found by screening, with a incidence of about 1:32 392 in our country. The clinical phenotype has been shown to vary considerably, ranging from entirely asymptomatic to death in infancy. A review of the literature on 37 individuals indicates that only 27% developed normally and stayed completely asymptomatic. Approximately 30% were reported to suffer from muscular hypotonia and psychomotor retardation, and almost half suffer from various other neurological symptoms. Even a lethality of 11% was observed. The metabolic phenotype characterizing MCCD is the elevated excretion of the diagnostic compounds 3-methylcrotonylglycine and 3-hydroxyisovaleric acid, and the presence of abnormally elevated blood levels of 3-hydroxyisovalerylcarnitine (C5-OH), as determined by tandem mass spectrometry (MS/MS). Patient and methods: The authors present a symptomatic case with an increase of C5-OH in the acylcarnitine profile who have a developmental delay. Blood spot samples from newborns are collected between day 3 and 6 in Watman 903 filter paper. Acylcarnitines in samples are analysed by MS/MS. Genes MCCA and MCCB that encodes the enzyme 3-MCC were studied by reported methods. Results: The molecular study has allowed the identification of the compound heterozygous in this patient: the frameshift mutation p.S173FfsX25 and the missense mutation p.V339M. Both mutations are described in the literature. Discussion: The newborn screening identification of a patient which developed symptoms seems to indicate that this disease should be included in NBS programs. More studies are needed to find genetic and/or biochemical markers that explain why a relatively small number of individuals are at risk of developing a severe disease phenotype. Another important reason to include MCCD in our panel is that other disorders are also detected by the marker C5OH; for example deficiencies of holocarboxylase synthetase, and 3-hydroxy- 3-methylglutaryl-CoA lyase.
- 6q terminal deletion: a new contribution to genotype-phenotype correlationPublication . Simão, Laurentino; Marques, Bárbara; Sónia, Pedro; Antunes, Diana; Brito, Filomena; Silva, Neuza; Nunes, Luis; Correia, HildebertoDeletion of chromosome 6q is a relatively rare clinical entity associated to a considerable variability of the phenotypic spectrum. Mental retardation, facial dimorphisms, seizures, and brain abnormalities are typical features of this syndrome but until recently genotype-phenotype correlations have been scarce. We report a 15-year-old boy with slight developmental delay, intellectual disability, hypotonia, bilateral eye cataracts, mycrocephaly, agenesis of the corpus callosum, ventriculomegaly, paroxysmal attacks, kyphoscoliosis and trigonocephaly. Cytogenetic analysis revealed a de novo karyotype 46,XY,del(6)(q25.3). Microarrays genomic analysis with Cytoscan 750K allowed the refinement of the breakpoint region to 6q26q27, spanning approximately 7.76 Mb. The variation of the features attributed to 6q deletion syndrome is due primarily to differences in size and location of the segmental aneuploidy. Several studies suggest that deletions of 6q25 region can cause more severe anomalies that those including 6q26-27. Absence of IUGR, ear anomalies, ear loss, cleft palate, cardiac defects and genital hypoplasia in our patient are compatible with studies that generally correlate those features with deletions of 6q25 region. In addition, our patient presents retinal abnormalities, which has been associated to 6q26-q27 deletion. Some new candidate genes, localized at 6qter, have recently been described as being associated with some clinical features; an example is the candidate gene DLL1 and holoprosencephaly. Analysis of the breakpoints in most cases revealed a potential common breakpoint region at 8.0-9.0Mb from the chromosome 6q terminus where a fragile site exists (FRA6E). This suggests the breakage at the FRA6E may be the mechanism behind chromosome 6q subtelomeric deletions in some of the cases.Once the genotype-phenotype correlations have been scarce until now, with this study we aim to contribute to a better knowledge of the genotype-phenotype correlation of 6q terminal deletion and help to identify critical regions for several clinical features and developmental relevant genes.
- Accreditation under the International Standard ISO 15189: Experience of a Genetics Laboratory in DNA SequencingPublication . Silva, Catarina; Cardoso, Ana; A Sampaio, Daniel; Carpinteiro, Dina; Mendonça, Joana; Duarte, Sílvia; Barreiro, Paula; Torgal, Helena; Isidro, Glória; Vieira, LuísIntroduction: Health care is to some extent influenced by the results of laboratory tests. In order to provide the best care for the patient, laboratories must seek to achieve high levels of quality and competence. International Standard ISO 15189 specifies these requirements and may be used by laboratories to perform accredited genetic tests of materials derived from the human body. Here we describe the procedures to establish Accreditation of DNA sequencing in our laboratory and the first Accreditation of its kind in Portugal. Methods: Our laboratory started to prepare to comply with ISO 15189 Accreditation requirements for DNA sequencing in 2010. Documents describing administrative and technical procedures of the sequencing workflow including sample registries, laboratory protocols, operation and maintenance of equipments, as well as preparation and use of reagents were produced. Regular examination of laboratory equipments by an external entity was implemented to confirm compliance with working requirements. Requisites for personnel training and demonstration of competence were also implemented. The laboratory participated regularly in the DNA sequencing scheme organized by the European Molecular Genetics Quality Network (EMQN). Results: The laboratory obtained formal recognition by Instituto Português de Acreditação (IPAC) in May 2014. A maximum genotyping score for DNA sequencing has been obtained in the external quality assessment scheme since 2010. Sequencing quality measured in terms of the quality read overlap metrics is currently of approximately 96% according to the EMQN scheme. The laboratory processes and analyzes an average of 28.750 samples per year. Discussion: Accreditation of a genetic test under ISO 15189 is a highly demanding and laborious task for a genetic laboratory. However, it is an important step in order to guarantee the highest quality and reproducibility of genetic test results.
- Alpha-thalassemia due to novel deletions and complex rearrangements in the subtelomeric region of chromosome 16pPublication . Ferrão, José; Silva, Marisa; Gonçalves, Lúcia; Gomes, Susana; Loureiro, Pedro; Coelho, Andreia; Miranda, Armandina; Seuanes, Filomena; Batalha Reis, Ana; Pina, Francisca; Maia, Raquel; Kjollerstrom, Paula; Monteiro, Estela; F. Lacerda, João; Lavinha, João; Gonçalves, João; Faustino, PaulaIntroduction: Inherited deletions removing the α-globin genes and/or their upstream regulatory elements (MCSs) give rise to alpha-thalassemia, one of the most common genetic recessive disorders worldwide. The pathology is characterized by microcytic hypochromic anemia due to reduction of the α-globin chain synthesis, which are essential for hemoglobin tetramerization. Material and Methods: In order to clarify the suggestive α-thalassemia phenotype in eleven patients, we performed Multiplex Ligation-dependent Probe Amplification with commercial and synthetic engineered probes, gap-PCR, and Sanger sequencing to search for deletions in the subtelomeric region of chromosome 16p. Results: We have identified five distinct large deletions, two of them novel, and one indel. The deletions range from approximately 3.3 to 323 kb, and i) remove the whole α-globin cluster; or ii) remove exclusively the upstream regulatory elements leaving the α-globin genes structurally intact. The indel consists in the loss of MCS-R2 (HS-40), which is the most important distal regulatory element for the α-globin gene expression, and the insertion of 39 bp, seemingly resulting from a complex rearrangement involving two DNA segments (probably from chromosome 3q) bridging the deletion breakpoints with a CC-bp orphan sequence in between. Finally, in one patient no α-globin deletion or point mutation were found. This patient revealed to be a very unusual case of acquired alpha-thalassemia associated with a myelodysplastic syndrome. Conclusions: Our study widens the spectrum of molecular lesions by which α-thalassemia may occur and emphasizes the importance of diagnosing large α-zero-deletions to provide patients with appropriate genetic counseling.
- Alternative splicing of tumour-related rac1b is regulated by upstream signalling pathwaysPublication . Gonçalves, Vânia; Matos, Paulo; Jordan, PeterThe small GTPase Rac1 regulates signalling pathways controlling actin-dependent cell motility as well as gene transcription. Analternative splicing variant Rac1b is overexpressed in a subset of colorectal tumours and cooperates with mutant B-Raf to sustain tumour cellviability. The alternative splicing mechanism regulating Rac1b expression involves two antagonistic splicing factors, ASF/SF2 and SRp20. Using aRac1 minigene approach and siRNA-mediated depletion, we identified ASF/SF2 as an enhancer of endogenous Rac1b splicing whereas SRp20 actsas a silencer. Inhibition of the PI3-kinase pathway increased protein levels of ASF/SF2 and promoted Rac1b generation. By contrast, depletion ofendogenous protein kinase SRPK1 led to decreased Rac1b expression. Together, these data indicate that altered upstream signaling pathways incolorectal cancer cells will target splicing factors that regulate alternative splicing of the small GTPase Rac1.
- An Alu-mediated 1Mb deletion removes Wilms’ tumor 1 (WT1) but not PAX6 in a patient with isolated cryptorchidismPublication . Seabra, Catarina; Quental, Sofia; Neto, Ana; Carvalho, Filipa; Gonçalves, João; Fernandes, Susana; Sousa, Mário; Barros, Alberto; Amorim, António; Lopes, Alexandra MObjective: We have recently performed an array-based genome-wide analysis of structural variants in a cohort of patients with non-obstructive azoospermia (NOA) and found a cryptic deletion of approximately 1Mb in 11p13, spanning the WT1 gene but not PAX6, in a Portuguese patient with clinical history of cryptorchidism during childhood?. Here we performed the molecular characterization of this novel deletion, to precisely map the breakpoints of this deletion, and evaluated the prevalence of focal WT1 genetic alterations in infertile Portuguese patients with cryptorchidism. Design: Fine molecular characterization of a heterozygous large deletion in 11p13 in one azoospermic patient (with clinical history of cryptorchidism) and screening for WT1 exonic microdeletions and mutations in a group of 31 Portuguese patients with uni- or bi-lateral cryptorchidism. Materials and Methods: Multiplex ligation-dependent probe amplification (MLPA), Long Range PCR; PCR amplification of the WT1 exons and proximal flanking sequences followed by Sanger sequencing. Results: We confirmed by MLPA the ~1Mb deletions at 11p13 spanning six genes - WT1, PRRG4, QSER1, TCP11L1, CSTF3 and HIPK3. Examination of the deletion breakpoint showed that it lies within highly homologous Alu Y sequences. Therefore the likely mechanism for this deletion was Alu-mediated non-allelic homologous recombination (NAHR). No mutations were found in the single allele present in this patient suggesting that the phenotype probably results from WT1 haploinsufficiency. We found no additional WT1 alterations in our group of patients with cryptorchidism. Conclusions: To our knowledge this is the smallest as yet described deletion encompassing the WT1 gene, which results in a non-syndromic clinical presentation of infertility. Repeat-mediated non-allelic recombination is an alternative mechanism for 11p13 deletions spanning WT1. Based on our results WT1 genetic defects are not frequently involved in isolated cryptorchidism, even though more patients should be analyzed. Support: This work was partially funded by the Portuguese Foundation for Science and Technology FCT/MCTES (PIDDAC) and co-financed by European funds (FEDER) through the COMPETE program, research grant PTDC/SAU-GMG/101229/2008 to AML. IPATIMUP is an Associate Laboratory of the Portuguese Ministry of Science, Technology, and Higher Education and is partially supported by FCT. AML is the recipient of a postdoctoral fellowship from FCT (SFRH/BPD/73366/2010).
- An unexpected role for DIS3L2 over human NMD targetsPublication . Costa, Paulo; Saramago, Margarida; Viegas, Sandra; Arraiano, Cecília; Santos, Hugo; Gama-Carvalho, Margarida; Romão, LuísaThe final step of cytoplasmic mRNA degradation proceeds in either a 5’-3’ direction, catalyzed by XRN1, or in a 3’-5’ direction catalyzed by the exosome and DIS3L2. In yeast, DIS3/Rrp44 protein is the catalytic subunit of the exosome. In humans, there are three known paralogues of this enzyme: DIS3, DIS3L1, and DIS3L2. Important findings over the last years have shed a new light onto the mechanistic details of RNA degradation by these exoribonucleases. In addition, it has been shown that they are involved in growth, mitotic control and important human diseases, including cancer. For example, DIS3L2 inactivation was associated with mitotic abnormalities and altered expression of mitotic checkpoint proteins. In another study, DIS3 was found to be highly expressed in colorectal cancer (CRC), suggesting an oncogenic function. A major challenge in systems biology is to reveal the cellular networks that give rise to specific phenotypes. In this project, we aim to analyze how DIS3, DIS3L1 and DIS3L2 regulate the human transcriptome, and how their functional interactions modulate the transcriptional reprogramming of colorectal cancer cells. In order to unveil the role of these exoribonucleases in general mRNA decay, and/or in cytoplasmic mRNA surveillance mechanisms, such as nonstop- and nonsense-mediated decay (NSD and NMD), we performed their knockdown and measured the mRNA levels of various reporter transcripts (endogenous and exogenous), with emphasis in natural NMD targets. Our results show that DIS3 and DIS3L1 seem to be involved in the normal mRNA turnover, as well as in the NSD and NMD mechanisms. However, some natural NMD targets are resistant to these nucleases. On the other hand, DIS3L2 is not involved in the normal mRNA turnover or in NSD, being specifically involved in the degradation of some NMD targets. Presently, we are interested in identifying the transcript features implicated in the decision-making process of DIS3L2-mediated decay of natural NMD targets, as well as the corresponding mechanism. With this purpose, we performed a bioinformatics analysis of available transcriptomic data from DIS3, DIS3L1, DIS3L2+XRN1, XRN1, or UPF1 (a central player in NMD) knockdown experiments and identified transcripts differentially expressed in each condition. Results show some, but not total, redundancy between the upregulated transcripts, and this supports our experimental data.
- An upstream open reading frame regulates the human erythropoietin gene expressionPublication . Barbosa, Cristina; Romão, Luísa
- Análise citogenética num grupo de doentes com Síndrome Mielodisplásico (estudo retrospetivo)Publication . Silva, Maria; Ambrósio, Ana; Silva, Neuza; Ventura, Catarina; Furtado, José; Correia, HildebertoOs Síndromes Mileodisplásicos (SMD) constituem um grupo de patologias clonais heterogéneas, caraterizadas por citopénias; displasia de uma ou mais linhas celulares mieloides e uma hematopoiese ineficaz. A idade média dos pacientes ao diagnóstico é de 70 anos, com uma predominância de ocorrência do sexo masculino e incidência anual de 3-5/100 000 indivíduos. O objetivo deste estudo é realizar uma avaliação retrospetiva dos resultados citogenéticos obtidos em 440 amostras de medula óssea de pacientes com diagnóstico inicial de SMD e tentar obter uma correlação entre os achados citogenéticos e a patologia em estudo. A população estudada por citogenética convencional é constituída por 218 indivíduos do sexo feminino e 222 indivíduos do sexo masculino, com uma idade média de 66 anos. Das 440 amostras analisadas, 104 (23,6% da população total) apresentavam cariotipos anormais. Os cariotipos que apresentavam anomalias foram divididos em: − População A - Cariotipos com uma só anomalia cromossómica (72 amostras) − População B - Cariotipos com duas anomalias cromossómicas (9 amostras) − População C - Cariotipos complexos com três ou mais anomalias cromossómicas (23 amostras) Na população A, a anomalia observada com maior frequência foi a trissomia 8 (25%), seguida da deleção do cromossoma 5 (16,7%), perda do cromossoma Y (15,3%) e deleção do cromossoma 20 (8,3%), estes resultados não se encontram de acordo com os descritos na literatura. Contudo quando se juntam as três populações, verifica-se que a anomalia observada com maior frequência é a deleção do cromossoma 5 (28,8%) o que já se encontra de acordo com o descrito. A perda do cromossoma Y observada nos indivíduos do sexo masculino, não parece estar correlacionada apenas com a idade, mas parece ser um dos fatores que carateriza este grupo de patologias. As anomalias observadas por análise citogenética convencional (uma técnica de baixo custo) permitiram ao clínico uma melhor avaliação de prognóstico e uma decisão terapêutica mais adequada.
- Análise de proteínas musculares por Western blot em doentes com Distrofia Muscular das Cinturas tipo 2A (LGMD2A)Publication . Maia, Nuno; Vieira, Emília; Santos, Rosário; Oliveira, Marcia E.Introdução: As Distrofias Musculares são um grupo de doenças musculares hereditárias, genotipicamente e fenotipicamente heterogéneo, envolvendo normalmente o músculo esquelético (1). Actualmente, estão identificados 18 genes associados a um subgrupo específico denominado Distrofias Musculares das Cinturas (LGMDs, limb-girdle muscular dystrophies), caracterizadas por fraqueza inicial da musculatura pélvica e escapular (2). Alterações no gene CAPN3 são responsáveis pelo fenótipo LGMD tipo 2A (LGMD2A), de transmissão autossómica recessiva (3), sendo esta uma das formas mais comuns (4). Este gene codifica a enzima citosólica calpaína 3 (CAPN3), expressa predominantemente no músculo esquelético e que pertence a uma família de proteases de cisteína não lissossomais dependentes de cálcio (5). Vários estudos demonstraram que a capacidade autolítica da CAPN3 é essencial para a activação e regulação da sua actividade proteolítica (6). A análise das proteínas musculares da maioria dos doentes com LGMD2A revela uma diminuição da expressão da CAPN3 comparativamente a músculos controlo. No entanto, um pequeno grupo desses doentes apresenta expressão normal da enzima, mas função autolítica deficiente (7). Objectivo: Dado o largo espectro de mutações detectadas nos doentes com diagnóstico molecular de LGMD2A realizado na UMOP, este trabalho visa complementar o estudo molecular, através da análise por Western blot das proteínas musculares, e tentar estabelecer uma relação fenótipo/genótipo. Material e Métodos: Foram utilizadas biópsias musculares de 9 doentes LGMD2A diagnosticados molecularmente na UMOP em estudos de expressão/ funcionais da CAPN3 e de outras proteínas musculares, por Western blot e densitometria. Resultados e Discussão: Não foi detectada expressão da CAPN3 em 5 amostras analisadas, sugerindo alterações ao nível da tradução da proteína. Foi verificada perda da função autolítica da CAPN3 em 2 doentes com expressão muscular da proteína. Devido à degradação generalizada do conteúdo proteico muscular verificado em algumas das biópsias estudadas, como resultado do acondicionamento inapropriado, não foi possível avaliar quantitativamente a expressão da CAPN3 e de outras proteínas musculares em todas as amostras. Por este facto, vão ainda ser realizados estudos de expressão do gene CAPN3, por PCR de tempo real, na tentativa de correlacionar todas as alterações observadas ao nível de DNA, RNA e proteína nos doentes estudados. Referências bibliográficas 1. Gaina G, Manole E, Bordea C, Ionica E. Analysis of calpain-3 in LGMD2A. Seria Stiintele Vietii (Life Sciences Series) 2008, 18:181-186. 2. Zatz M, Paula F, Starling A. The 10 autosomal recessive limb-girdle muscular dystrophies. Neuromuscular Disord 2003, 13:532-544. 3. Richard I, Broux O, Allamand V, Fougerousse F, Chiannilkulchai N, Bourg N, Brenguier L, Devaud C, Pasturaud P, Roudaut C, Hillaire D, Passos-Bueno MR, Zatz M, Tischfield JA, Fardeau M, Jackson CE, Cohen D, Beckmann JS. Mutations in the proteolytic enzyme calpain 3 cause limb-girdle muscular dystrophy type 2A. Cell, 1995, 81:27-40. 4. Fanin M, Nascimbeni AC, Fulizio L, Angelini C. The frequency of limb girdle muscular dystrophy 2A in northeastern Italy. Neuromuscular Disord 2005, 15(3):218-224. 5. Kramerova I, Beckmann JS, Spencer MJ. Molecular and cellular basis of calpainopathy (limb girdle muscular dystrophy type 2A). Biochimica et Biophysica Acta 2007, 128-144. 6. Groen EJ, Charlton R, Barresi R, Anderson LV, Eagle M, Hudson J, Koref MS, Straub V, Bushby KMD. Analysis of the UK diagnostic strategy for limb girdle muscular dystrophy 2A. Brain 2007, 130:3237-3249. 7. Fanin M, Nascimbeni AC, Tasca E, Angelini C. How to tackle the diagnosis of limb-girdle muscular dystrophy 2A. Eur J Hum Genet 2009, 17(5):598-603.