Giovanna Cotugno

Bio: Giovanna Cotugno is an academic researcher. The author has contributed to research in topics: Terminator (genetics) & Stop codon. The author has an hindex of 1, co-authored 1 publications receiving 32 citations.

Does the nonsense-mediated mRNA decay mechanism prevent the synthesis of truncated BRCA1, CHK2, and p53 proteins?

Abstract: The nonsense-mediated mRNA decay (NMD) mechanism is an evolutionarily conserved process ensuring the degradation of transcripts carrying premature termination codon(s). NMD is believed to prevent the synthesis of truncated proteins that could be detrimental to the cell. However, although numerous studies have assessed the efficiency of this mechanism at the mRNA level, data are lacking in regard to whether NMD fulfills its expected goal at the protein level. In this study, we have investigated whether endogenous alleles of breast cancer predisposing genes carrying nonsense codons were able to produce detectable amounts of truncated proteins in lymphoblastoid cell lines. A total of 20 truncating BRCA1 mutations were analyzed, along with the 1100delC CHEK2 and the 770delT TP53 mutations. All the studied alleles triggered NMD, the amount of mutant transcript ranging from 16 to 63% of that of the wild-type species. We found that BRCA1 and CHK2 truncated proteins could not be detected, even when NMD was inhibited. This suggests that BRCA1 and CHK2 truncated proteins are highly unstable. Conversely, the p53 protein encoded by the 770delT allele is as abundant as the wild-type protein, as removal of the C-terminal p53 domain leads to a stabilized mutant protein, whose abundance is markedly increased when NMD is inhibited. Therefore, our results show that it is not possible to infer the presence of truncated proteins in cells from carriers of a truncated mutation without experimental verification, as each case is expected to be different.

Mucopolysaccharidosis type II: an update on mutation spectrum.

Abstract: UNLABELLED Mucopolysaccharidosis type II (MPS II; Hunter disease) is caused by deficiency of the enzyme iduronate-2-sulphatase (IDS) and patients present with a wide range of clinical signs and symptoms. The level of activity of IDS, however, does not allow prediction of phenotype. In our study of unrelated individuals with MPS II, alterations in the IDS gene could be identified in all 155 patients. Investigations in families in which the occurrence of MPS II was sporadic revealed mosaicism in the mothers of a small number of patients and a high frequency of de novo mutations occurring preferentially during male meiosis. Mutations identified in our patients include 27 large alterations and 128 small gene alterations (96 different alterations). These data further confirm the extreme heterogeneity of IDS gene alterations, as more than 330 have been reported to date. This genetic heterogeneity may explain the high degree of clinical heterogeneity in MPS II. Therefore, attempts have been made to establish genotype-phenotype correlations in order to provide an indication of the likely prognosis and a basis on which to evaluate treatment. To date, some progress has been made in predicting the clinical phenotype from the genotype although it remains difficult in a few individual cases. However, as the crystallographic 3D structure of IDS is yet to be determined, evaluation of the impact of mutations on IDS activity is often time consuming. Furthermore, if a given mutation is recurrent, some patients carrying the same change may present with different phenotypes, suggesting that factors other than the IDS gene (e.g. other genes, environmental factors) can modulate the clinical phenotype. CONCLUSION Although genotype-phenotype correlations may be difficult to establish, they will be of increasing importance for choosing the most appropriate therapy for an individual patient, as new therapeutic strategies may be targeted according to phenotype.

Expression of the muscle glycogen phosphorylase gene in patients with McArdle disease: the role of nonsense-mediated mRNA decay.

Abstract: Nearly 35% of all mutations identified in the muscle glycogen phosphorylase gene (PYGM) in patients with McArdle disease result in premature termination codons (PTCs), particularly the pR50X mutation The latter accounts for more than 50% of the mutated alleles in most Caucasian patient populations Mutations resulting in PTC could trigger the degradation of mRNA through a mechanism known as nonsense mediated decay (NMD) To investigate if NMD affects the levels of transcripts containing PYGM mutations, 28 Spanish patients with McArdle disease, harboring 17 different mutations with PTCs in 77% of their alleles, were studied Transcripts levels of PYGM were measured and sequenced We assessed that 92% of patients showed NMD The most frequent mutation (pR50X) elicited decay in all the genotypes tested Other PTC producing mutations resulting in NMD were: pL5VfsX22, pQ73HfsX7, pE125X, pN134KfsX161, pW388SfsX34, pR491AfsX7, and pD534VfsX5 Located in the last exon, the mutation pE797VfsX19 was not affected by NMD Missense mutations did not appear to be affected by NMD In the cDNA sequences they appeared as homozygous, despite being heterozygous in the genomic DNA sequences Exceptions to the rules governing NMD were found in the mutations pA704 V and pK754NfsX49

Messenger RNA surveillance systems monitoring proper translation termination.

Abstract: Organisms have evolved an elaborate set of quality control systems to ensure the fidelity of the genetic information flow. The mRNA surveillance systems work in this context by monitoring the quality of mRNAs to ensure that they are suitable for translation. In this review, recent achievements in the investigation of mRNA surveillance pathways, including nonsense-mediated mRNA decay and nonstop-mediated mRNA surveillance pathway, will be discussed.

Mucopolysaccharidosis type IIID: 12 new patients and 15 novel mutations

Abstract: Mucopolysaccharidosis III D (Sanfilippo disease type D, MPS IIID) is a rare autosomal recessive lysosomal storage disorder previously described in only 20 patients. MPS IIID is caused by a deficiency of N-acetylglucosamine-6-sulphate sulphatase (GNS), one of the enzymes required for the degradation of heparan sulphate. So far only seven mutations in the GNS gene have been reported. The clinical phenotype of 12 new MPS IIID patients from 10 families was studied. Mutation analysis of GNS was performed in 16 patients (14 index cases). Clinical signs and symptoms of the MPS IIID patients appeared to be similar to previously described patients with MPS III. Early development was normal with onset of behavioral problems around the age of 4 years, followed by developmental stagnation, deterioration of verbal communication and subsequent deterioration of motor functions. Sequence analysis of the coding regions of the gene encoding GNS (GNS) resulted in the identification of 15 novel mutations: 3 missense mutations, 1 nonsense mutation, 4 splice site mutations, 3 frame shift mutations, 3 large deletions and 1 in-frame small deletion. They include the first missense mutations and a relatively high proportion of large rearrangements, which warrants the inclusion of quantitative techniques in routine mutation screening of the GNS gene.