Leonor Osorio | Universidade Nova de Lisboa (original) (raw)
Papers by Leonor Osorio
Human Genetics, 1993
The WT1 gene was analysed using DNA from a Wilms' tumour derived from a patient with the WAGR syn... more The WT1 gene was analysed using DNA from a Wilms' tumour derived from a patient with the WAGR syndrome using single strand conformation polymorphism analysis and polymerase chain reaction sequencing. A 14-bp insertion was found in the intron part of the splice donor site of exon 7 and was a tandem duplication of an upstream exon sequence. This mutation would be expected to disrupt the correct processing of the WT1 mRNA and is predicted to result in a non-functional protein. This observation further supports the role of WT1 in Wilms' tumorigenesis in patients with constitutional 11p13 deletions.
Human Genetics, 1992
In order to delineate the spectrum and the relative abundance of β-globin gene defects causing th... more In order to delineate the spectrum and the relative abundance of β-globin gene defects causing thalassaemia in the Portuguese population, a representative sample was analysed including 51 β-thalassaemia carriers along with 26 patients representing different clinical phenotypes. Seven mutations were identified, four of which [codon 39 (C→T), 39%; intervening sequence (IVS)1 nucleotide (nt) 1 (G→A), 26%; IVS1 nt 110 (G→A), 17%; IVS1 nt6 (T→C), 15%] account for 97% of 93 β-thalassaemia chromosomes. Two previously undescribed mutations, namely a C→T substitution at position — 90 in the proximal CACCC box, and the deletion of nucleotides 4 and 5 (AG) in IVS 2 were identified. The uncommon, though ubiquitous, G→T transversion at codon 121 was found once upon haplotype V. Direct prenatal diagnosis can be offered to 95% of couples at risk of bearing a thalassaemic child.
Human Genetics, 1994
In a survey of the chromosomal backgrounds associated with the sickle cell gene in Portuguese-spe... more In a survey of the chromosomal backgrounds associated with the sickle cell gene in Portuguese-speaking populations from Europe and Africa, a discordance between the classical haplotype and the predicted allele at theRsaI polymorphism 5′ to the β globin gene was observed in four patients. Extensive typing of the corresponding βs chromosomes at simple polymorphic repeat motifs revealed a novel “extended” haplotype that appeared to be a mosaic of (1) a Bantu-type DNase I hypersensitive site 2 within the β globin gene cluster locus control region, (2) a Benin 5′ subhaplotype, and (3) a Bantu 3′ subhaplotype. We propose two alternative schedules for the generation of yet another chromosomal background of the sickle cell gene.
American Journal of Hematology, 1998
British Journal of Haematology, 2002
Haematological as well as gene mapping data are reported for three members of a Portuguese Caucas... more Haematological as well as gene mapping data are reported for three members of a Portuguese Caucasian family with high G c-globin levels. A gamma-globin gene sextuplication of the G c AG c AG c AG c AG c A c type was present in the proband and her father. Comparison of gene mapping data with quantitative results of fetal haemoglobin (HbF) analysis provided an explanation for the extremely high G c-globin levels (> 90%) in the HbF from the two mentioned individuals. This rearrangement, for which a generation mechanism is proposed, is the ®rst gamma-globin gene sextuplication described in the literature.
European Journal of Biochemistry, 1987
Phenobarbital evokes a pleiotypic response in the liver characterized by cell hypertrophy and mon... more Phenobarbital evokes a pleiotypic response in the liver characterized by cell hypertrophy and mono-oxygenase induction. These phenomena arise through complex modulation mechanisms changing the pattern of protein synthesis, distinct from those triggered by other well known inducers, like steroid hormones or polycyclic hydrocarbons. To investigate the mechanisms involved in regulating the expression of the phenobarbital-inducible tissue-specific genes, we constructed two libraries of recombinant bacterial plasmids pBR322 in Escherichia coli. Each library contains cDNA copies of polysomal poly(A)-rich RNA obtained from control and 16-h phenobarbital-induced rat liver. A thousand cloned sequences from each library were screened by double-cross colony hybridization using [32P]cDNA prepared from homologous and heterologous poly(A)-rich RNAs as the probes. The statistical analysis of the results revealed that phenobarbital treatment significantly changes the relative abundance of different polysomal mRNA classes in rat liver. Clones corresponding to mRNAs clearly induced following phenobarbital treatment have been further selected by plasmid DNA dot hybridization, and used as probes for measuring the changes in each mRNA concentration in the whole cell and in the polysomal RNAs from rat livers, at different times after phenobarbital treatment. The fact that changes in the concentration of each specific mRNA in the polysomes does not parallel the variation of its total concentration in the cell indicates that the induced modulation of protein synthesis in the liver is brought about by mechanisms involving both transcriptional and translational regulation, since besides the increases in whole cellular mRNA concentration a marked mobilization of mRNA into active polysomes could be demonstrated during the onset of the adaptive response to phenobarbital.
Biochimica Et Biophysica Acta-molecular Basis of Disease, 1998
A new mutation in WT1 is described in a sporadic unilateral Wilms' tumour consisting of a 17 bp d... more A new mutation in WT1 is described in a sporadic unilateral Wilms' tumour consisting of a 17 bp duplication in exon 7 generating a stop codon. The second allele is either partially deleted or presents the same alteration. LOH analysis at 11p15.5 and at the 16q13-16q24.3 regions indicated retention of heterozygosity in the tumour DNA for the markers analysed. The results are consistent with Knudson's hypothesis and confirm that loss of function of WT1 contributes to the development of at least some Wilms' tumours. ß 1998 Elsevier Science B.V. All rights reserved.
Human Genetics, 1993
The WT1 gene was analysed using DNA from a Wilms' tumour derived from a patient with the WAGR syn... more The WT1 gene was analysed using DNA from a Wilms' tumour derived from a patient with the WAGR syndrome using single strand conformation polymorphism analysis and polymerase chain reaction sequencing. A 14-bp insertion was found in the intron part of the splice donor site of exon 7 and was a tandem duplication of an upstream exon sequence. This mutation would be expected to disrupt the correct processing of the WT1 mRNA and is predicted to result in a non-functional protein. This observation further supports the role of WT1 in Wilms' tumorigenesis in patients with constitutional 11p13 deletions.
Human Genetics, 1992
In order to delineate the spectrum and the relative abundance of β-globin gene defects causing th... more In order to delineate the spectrum and the relative abundance of β-globin gene defects causing thalassaemia in the Portuguese population, a representative sample was analysed including 51 β-thalassaemia carriers along with 26 patients representing different clinical phenotypes. Seven mutations were identified, four of which [codon 39 (C→T), 39%; intervening sequence (IVS)1 nucleotide (nt) 1 (G→A), 26%; IVS1 nt 110 (G→A), 17%; IVS1 nt6 (T→C), 15%] account for 97% of 93 β-thalassaemia chromosomes. Two previously undescribed mutations, namely a C→T substitution at position — 90 in the proximal CACCC box, and the deletion of nucleotides 4 and 5 (AG) in IVS 2 were identified. The uncommon, though ubiquitous, G→T transversion at codon 121 was found once upon haplotype V. Direct prenatal diagnosis can be offered to 95% of couples at risk of bearing a thalassaemic child.
Human Genetics, 1994
In a survey of the chromosomal backgrounds associated with the sickle cell gene in Portuguese-spe... more In a survey of the chromosomal backgrounds associated with the sickle cell gene in Portuguese-speaking populations from Europe and Africa, a discordance between the classical haplotype and the predicted allele at theRsaI polymorphism 5′ to the β globin gene was observed in four patients. Extensive typing of the corresponding βs chromosomes at simple polymorphic repeat motifs revealed a novel “extended” haplotype that appeared to be a mosaic of (1) a Bantu-type DNase I hypersensitive site 2 within the β globin gene cluster locus control region, (2) a Benin 5′ subhaplotype, and (3) a Bantu 3′ subhaplotype. We propose two alternative schedules for the generation of yet another chromosomal background of the sickle cell gene.
American Journal of Hematology, 1998
British Journal of Haematology, 2002
Haematological as well as gene mapping data are reported for three members of a Portuguese Caucas... more Haematological as well as gene mapping data are reported for three members of a Portuguese Caucasian family with high G c-globin levels. A gamma-globin gene sextuplication of the G c AG c AG c AG c AG c A c type was present in the proband and her father. Comparison of gene mapping data with quantitative results of fetal haemoglobin (HbF) analysis provided an explanation for the extremely high G c-globin levels (> 90%) in the HbF from the two mentioned individuals. This rearrangement, for which a generation mechanism is proposed, is the ®rst gamma-globin gene sextuplication described in the literature.
European Journal of Biochemistry, 1987
Phenobarbital evokes a pleiotypic response in the liver characterized by cell hypertrophy and mon... more Phenobarbital evokes a pleiotypic response in the liver characterized by cell hypertrophy and mono-oxygenase induction. These phenomena arise through complex modulation mechanisms changing the pattern of protein synthesis, distinct from those triggered by other well known inducers, like steroid hormones or polycyclic hydrocarbons. To investigate the mechanisms involved in regulating the expression of the phenobarbital-inducible tissue-specific genes, we constructed two libraries of recombinant bacterial plasmids pBR322 in Escherichia coli. Each library contains cDNA copies of polysomal poly(A)-rich RNA obtained from control and 16-h phenobarbital-induced rat liver. A thousand cloned sequences from each library were screened by double-cross colony hybridization using [32P]cDNA prepared from homologous and heterologous poly(A)-rich RNAs as the probes. The statistical analysis of the results revealed that phenobarbital treatment significantly changes the relative abundance of different polysomal mRNA classes in rat liver. Clones corresponding to mRNAs clearly induced following phenobarbital treatment have been further selected by plasmid DNA dot hybridization, and used as probes for measuring the changes in each mRNA concentration in the whole cell and in the polysomal RNAs from rat livers, at different times after phenobarbital treatment. The fact that changes in the concentration of each specific mRNA in the polysomes does not parallel the variation of its total concentration in the cell indicates that the induced modulation of protein synthesis in the liver is brought about by mechanisms involving both transcriptional and translational regulation, since besides the increases in whole cellular mRNA concentration a marked mobilization of mRNA into active polysomes could be demonstrated during the onset of the adaptive response to phenobarbital.
Biochimica Et Biophysica Acta-molecular Basis of Disease, 1998
A new mutation in WT1 is described in a sporadic unilateral Wilms' tumour consisting of a 17 bp d... more A new mutation in WT1 is described in a sporadic unilateral Wilms' tumour consisting of a 17 bp duplication in exon 7 generating a stop codon. The second allele is either partially deleted or presents the same alteration. LOH analysis at 11p15.5 and at the 16q13-16q24.3 regions indicated retention of heterozygosity in the tumour DNA for the markers analysed. The results are consistent with Knudson's hypothesis and confirm that loss of function of WT1 contributes to the development of at least some Wilms' tumours. ß 1998 Elsevier Science B.V. All rights reserved.