José Barbot

FAS-L, IL-10, and double-negative CD4- CD8- TCR alpha/beta+ T cells are reliable markers of autoimmune lymphoproliferative syndrome (ALPS) associated with FAS loss of function.

Autoimmune lymphoproliferative syndrome (ALPS) is characterized by splenomegaly, lymphadenopathy, hypergammaglobulinemia, accumulation of double-negative TCRalphabeta(+) CD4(-)CD8(-) T cells (DNT cells), and autoimmunity. Previously, DNT cell detection and a functional defect of T cells in a FAS-induced apoptosis test in vitro had been used for ALPS diagnosis. However, a functional defect can also be detected in mutation-positive relatives (MPRs) who remain free of any ALPS-related disease. In contrast, lymphocytes from patients carrying a somatic mutation of FAS exhibit normal sensitivity to FAS-induced apoptosis in vitro. We assessed the soluble FAS-L concentration in the plasma of ALPS patients carrying FAS mutations. Overall, we showed that determination of the FAS-L represents, together with the IL-10 concentration and the DNT cell percentage, a reliable tool for the diagnosis of ALPS.

Inherited and acquired risk factors and their combined effects in pediatric stroke

The aim of this study was to identify hereditary and acquired risk-factors as they are related to the occurrence of stroke in children. We identified 21 children with stroke. A search of the Factor V Leiden mutation, the Factor II G20210A variant, and the thermolabile variant of methylenetetrahydrofolate reductase was performed in patients and in a control group (n = 115). We identified risk factors of acquired and/or hereditary nature for stroke in 19 of 21 children. Eleven children had three or more risk factors, seven had two risk factors, and one child had only one risk factor. We found three carriers (14.3%) of the Factor V Leiden mutation, two carriers (9.5%) of the Factor II G20210A variant, eleven (52.4%) thermolabile variant of methylenetetrahydrofolate reductase heterozygote carriers, and one (4.8%) homozygotes for this variant. Frequencies of the Factor V Leiden mutation and the Factor II variant were higher in patients than in controls, suggesting that these variants are associated with an increased risk of stroke in childhood. Homozygosity for the thermolabile variant of methylenetetrahydrofolate reductase was equally frequent amongst patients and controls. Our study confirms that stroke in children is commonly associated with a combination of multiple risk factors, both genetic and acquired, and that the Factor V Leiden mutation and the Factor II G20210A variant are predisposing factors for this situation.

Novel promoter and splice junction defects add to the genetic, clinical or geographic heterogeneity of β-thalassaemia in the Portuguese population

SummaryIn 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.

Hydrops fetalis associated with erythrocyte pyruvate kinase deficiency

Abstract The authors report a case of hydrops fetalis due to severe pyruvate kinase deficiency, the most unusual clinical manifestation of this disease. Conclusion Pyruvate kinase deficiency, as other erythrocyte enzymopathies, must be considered in the differential diagnosis of non-immune hydrops fetalis. This has important implications for clinical investigations, therapy and genetic counselling.

Presence of cytosolic peroxiredoxin 2 in the erythrocyte membrane of patients with hereditary spherocytosis.

We studied 82 Portuguese individuals, 57 with hereditary spherocytosis (HS) and 25 unaffected controls. We performed standardized diagnosis tests, including electrophoretic membrane protein analysis to identify and quantify protein deficiencies underlying HS. Membrane bound hemoglobin (MBH) and band 3 profiles were determined as oxidative stress and aging markers. A protein of about 22 kDa, present in 21 of 57 HS patients, but not in controls, was identified as peroxiredoxin 2 (Prx2), by mass-spectroscopy and by immunoblotting. Human erythrocyte Prx2 is a peroxiredoxin with thiol-specific antioxidant activity. The presence of Prx2 in erythrocyte membranes was linked to higher levels of oxidative stress, as reflected by significantly increased MBH in those HS patients. No relation with HS clinical severity was observed and Prx2 was detected in all types of membrane protein abnormalities. Prx2 membrane linkage is associated with a higher oxidative stress susceptibility of HS erythrocytes.

Protein deficiency balance as a predictor of clinical outcome in hereditary spherocytosis

Abstract:  Vertical and horizontal interactions between membrane constituents account for integrity, strength and deformability of the erythrocyte. Disruption of vertical interactions caused by membrane protein deficiencies in hereditary spherocytosis (HS), favor membrane vesiculation with development of spherocytic cells. Our aim was to evaluate the hematological and clinical presentation of HS according to the type and amount of protein deficiency. We studied 81 Portuguese individuals, 71 belonging to 21 families plus 10 unrelated subjects, and found that 51 of them were HS patients. Patients were classified as presenting mild, typical or severe HS, according to laboratory results and clinical follow‐up. We performed screening tests and the standardized electrophoretic membrane protein analysis to identify and quantify protein deficiencies. We found band 3 and ankyrin deficiencies as the major causes for HS. The ratios between the value of the primary and/or secondary protein deficiencies showed significantly different values according to the severity of HS, and a significant inverse correlation with the severity of HS was observed. In mild HS, the ratios between protein deficiencies reflected equivalent protein deficiencies, while an unbalance was observed in typical HS, which was enhanced in severe HS. Our data suggest that the relative quantification of each major membrane protein and of the ratios between the values of protein deficiencies may be helpful in providing additional data about the clinical outcome of HS.

Erythrocyte membrane protein destabilization versus clinical outcome in 160 Portuguese Hereditary Spherocytosis patients.

Hereditary Spherocytosis (HS) is a haemolytic anaemia caused by erythrocyte protein membrane defects – spectrin, ankyrin, band 3 or protein 4·2 – that lead to membrane destabilization. This study aimed to evaluate the prevalence of protein deficiencies and the role of membrane proteins or membrane‐linked proteins in membrane disturbance and in HS clinical outcome. A total of 215 Portuguese individuals were studied – 203 from 71 families plus 12 individual unrelated subjects; 160 of them were diagnosed with HS. They were classified as presenting mild, moderate or severe forms of HS according to the degree of haemolytic anaemia. Standardized electrophoretic erythrocyte membrane protein analysis was used to identify and quantify protein deficiencies. Band 3 and ankyrin were found to account for the majority of the erythrocyte protein defects underlying HS. Increasing isolated protein deficiency or increasing imbalance between combined protein deficiencies seemed to underlie HS severity, by increasing membrane destabilization. There was an increased membrane linkage of the cytosolic proteins, glyceraldehyde‐3‐phosphate dehydrogenase and peroxiredoxin 2, and of denatured haemoglobin, suggesting that this linkage could interfere with membrane structure. Our data suggest that the quantification and the analysis of RBC membrane proteins may be helpful in predicting the clinical outcome of HS.

Improvement of genetic stability in lymphocytes from Fanconi anemia patients through the combined effect of α-lipoic acid and N-acetylcysteine

Fanconi Anemia (FA) is a rare genetic disorder, characterized by progressive bone marrow failure and increased predisposition to cancer. Despite being highly heterogeneous, all FA patients are hypersensitive to alkylating agents, in particular to 1,2:3,4-diepoxybutane (DEB), and to oxidative damage. Recent studies point to defective mitochondria in FA cells, which is closely related with increased production of reactive oxygen species (ROS) and concomitant depletion of antioxidant defenses, of which glutathione is a well-known biomarker.The objective of the present work is to evaluate the putative protective effect of α-lipoic acid (α-LA), a mitochondrial protective agent, and N-acetylcysteine (NAC), a direct antioxidant and a known precursor for glutathione synthesis, in spontaneous and DEB-induced chromosome instability (CI) in lymphocyte cultures from FA patients.For that purpose, lymphocyte cultures from 15 FA patients and 24 healthy controls were pre-treated with 20 μM α-LA, 500 μM NAC and α-LA plus NAC at the same concentrations, and some of them were exposed to DEB (0.05 μg/ml). A hundred metaphases per treatment were scored to estimate the relative frequency of spontaneous and DEB-induced chromosome breakage.The obtained results revealed that a cocktail of α-LA and NAC can drastically improve the genetic stability in FA lymphocytes in vitro, decreasing CI by 60% and 80% in cultures from FA patients and FA mosaic/chimera patients, respectively. These results suggest that the studied cocktail can be used as a prophylactic approach to delay progressive clinical symptoms in FA patients caused by CI, which can culminate in the delay of the progressive bone marrow failure and early cancer development.

Two novel mutations in the tmprss6 gene associated with iron‐refractory iron‐deficiency anaemia (irida) and partial expression in the heterozygous form

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Erythropoietin levels in the different clinical forms of hereditary spherocytosis

Erythropoietin (EPO), the main growth factor responsible for the regulation of red blood cell production, may be overproduced when blood loss or haemolysis occurs. Patients with mild hereditary spherocytosis (HS) are able to maintain normal haemoglobin concentration, whereas typical and severe HS patients develop an anaemic state. Splenectomy usually reverses anaemia. We aimed to clarify the role of EPO in the response to enhanced spherocyte destruction, and to look for a linkage with the broad clinical spectra of HS. EPO levels, reticulocyte count and production index (RPI), other parameters used to classify HS and the protein deficiencies underlying HS were evaluated in previously diagnosed unsplenectomised (n = 24) and splenectomised (n = 10) patients presenting mild, typical or severe HS. A significant increase in EPO was observed in all unsplenectomised HS patients. In the mild form, a significant correlation of EPO with reticulocyte count and RPI was observed; however, this correlation disappeared in typical HS patients. Splenectomised HS patients presented a correction in EPO levels in all forms of HS, although the reticulocyte count and RPI sustained slightly higher values. Our data show HS as a disease linked to an overproduction of EPO, according to the severity of the disease; however, a disturbance in erythropoiesis seems to occur in typical HS. Moreover, splenectomy leads to a correction in the EPO levels.