[Molecular bases of α-thalassemia in Argentina]. / Bases moleculares de alfa-talasemia en la Argentina.

The α-thalassemia is one of the most common hereditary disorders worldwide. Currently, molecular diagnostics is the only available tool to achieve an accurate diagnosis. The purpose of this study was to characterize the molecular bases of these syndromes in our environment and to establish genotype-phenotype associations. Through a combination of different molecular techniques and fluorescent in situ hybridization (FISH),we were able to find α-thalassemic mutations in 145 of the 184 patients (78.8%) studied with hematological parameters compatible with α-thalassemia. Deletions of the α-globin genes resulted the major molecular cause of the disease, and the most frequent mutation was -α(3.7), found in homozygous and heterozygous genotypes. In patients with α° phenotypes, other prevalent mutations were( _MED) and (_CAL/CAMP). The description of a sub-telomeric deletion in a patient with α-thalassemia and mental retardation was also achieved. ß-thalassemic mutations in heterozygous state were found in 7.6% of the patients, who presented α-thalassemic clinical features (microcytosis and Hb A2levels below 3.5%). Hematologic profiles for the α+ and α° genotypes were established for adult and pediatric patients. Hopefully, this work will provide guidelines for the detection of possible α-thalassemic carriers. It also highlights the collaborative work of hematologists, the biochemical and molecular biology laboratory and genetists, in order to provide appropriate genetic counseling.

Bases moleculares de alfa-talasemia en la Argentina

La α-talasemia, es uno de los desórdenes hereditarios más frecuentes mundialmente. Al presente, el diagnóstico molecular es la única herramienta que permite el diagnóstico certero. El propósito de este trabajo fue caracterizar las bases moleculares de estos síndromes en nuestro medio, y establecer relaciones genotipo-fenotipo. Mediante la complementación de distintas técnicas de biología molecular e hibridación fluorescente in situ (FISH), se logró poner en evidencia la presencia de mutaciones α-talasémicas en 145 de 184 (78.8%) pacientes estudiados con perfil hematológico compatible con α-talasemia. Dentro de este grupo, las deleciones correspondieron al defecto genético más frecuente, prevaleciendo la mutación -α3.7 en genotipos heterocigotas y homocigotas. Asimismo, en pacientes con fenotipo α0 las deleciones prevalentes fueron -MED y -CAL/CAMP. Este estudio permitió también describir una deleción de la región sub-telomérica en un paciente con α-talasemia y retraso mental. En el 7.6% de los pacientes caracterizados clínicamente como posibles α-talasémicos (microcitosis con valores de Hb A2 inferiores al 3.5%), se hallaron mutaciones β-talasémicas en estado heterocigota. Se lograron establecer perfiles hematológicos asociados a los genotipos α+ y α0 para pacientes adultos y niños. Esperamos que este trabajo pueda servir como guía para reconocer posibles portadores α-talasémicos. También permite destacar el trabajo en conjunto de médicos hematólogos, el laboratorio (bioquímico y de biología molecular) y de los médicos genetistas, con el fin de proporcionar adecuado consejo genético.

The α-thalassemia is one of the most common hereditary disorders worldwide. Currently, molecular diagnostics is the only available tool to achieve an accurate diagnosis. The purpose of this study was to characterize the molecular bases of these syndromes in our environment and to establish genotype-phenotype associations. Through a combination of different molecular techniques and fluorescent in situ hybridization (FISH),we were able to find α-thalassemic mutations in 145 of the 184 patients (78.8%) studied with hematological parameters compatible with α-thalassemia. Deletions of the a-globin genes resulted the major molecular cause of the disease, and the most frequent mutation was -α3.7, found in homozygous and heterozygous genotypes. In patients with α0 phenotypes, other prevalent mutations were -MED and -CAL/CAMP. The description of a sub-telomeric deletion in a patient with α-thalassemia and mental retardation was also achieved. β-thalassemic mutations in heterozygous state were found in 7.6% of the patients, who presented α-thalassemic clinical features (microcytosis and Hb A2 levels below 3.5%). Hematologic profiles for the α+ and α0 genotypes were established for adult and pediatric patients. Hopefully, this work will provide guidelines for the detection of possible α-thalassemic carriers. It also highlights the collaborative work of hematologists, the biochemical and molecular biology laboratory and genetists, in order to provide appropriate genetic counseling.

Molecular characterization of a novel splice site mutation within the CYBB gene leading to X-linked chronic granulomatous disease.

Chronic granulomatous disease (CGD) is a primary immunodeficiency that affects the oxidative mechanism of microbial killing of phagocytic cells. The defect is characterized by a lack or severely reduced superoxide anion (O2-) production by phagocytes. Seventy percent of CGD cases are X-linked (X-CGD) and they are caused by mutations in the gene encoding for gp91(phox), one of the two subunits of the flavocytochrome b558 of the NADPH oxidase. We identified an abnormal transcript arising from a novel splice site mutation within the gene encoding gp91(phox), which suggested that the mutation affected normal mRNA splicing. Thus, the effect of this mutation leads to the complete absence of the flavocytochrome b558 in neutrophil membranes, which caused the biochemical phenotype X91 degrees-CGD in this family. These molecular findings help to explain the early onset and severe phenotype in this X-CGD kindred.

[Molecular pathogenesis of carcinoma of the esophagus]. / Patogénesis molecular del carcinoma de esófago.

Carcinoma of the esophagus is present in two distinct morphological cell types: squamous or pavimentous cell carcinoma and adenocarcinoma. In this article, the main genetic alterations found in both types of carcinomas and their implications are described. The sequence of these alterations is related to histogenesis, making it possible to understand tumor progression from normal epithelium to invasive carcinoma. A comparison is attempted between the molecular development of esophagus carcinomas and that of colorectal carcinoma.

Patogenesis molecular del carcinoma de esofago / Molecular pathogenesis of carcinoma of the esophagus

El carcinoma de esófago existe en dos formas principales: el carcinoma de células escamosas o pavimentoso y el adenocarcinoma. En este artículo se describen las principales alteraciones genéticas halladas en ambos tipos de carcinomas y la implicancia de éstas en la patogénesis de los mismos. La secuencia de estas alteraciones se correlaciona con la histogénesis, lo que permite comprender la progresión tumoral desde el epitelio normal al carcinoma invasor. Se establece también una comparación entre la patogénesis molecular delcáncer de esófago y del desarrollo de estos carcinomas con el modelo de la patogénesis molecular del cáncer colorrectal.

Absence of mutations in the P53 tumor suppressor gene in non-invasive Cushing adenomas

A lot of evidence supports the existence of a monoclonal origin for pituitary tumors, and several genetic alterations have already been confirmed as necessary or sufficient for unrestrained cellular growth and pituitary function. The p53 gene, a known tumor-suppressor gene (TSG), encodes a protein that exerts antiproliferative effects such as cell-growth arrest and apoptosis in response to several types of stimuli. In fact, several human cancers are believed to be caused by p53 mutations. In the case of pituitary tumors, p53 protein accumulation has been described in ACTH-secreting pituitary adenomas. Since increased amounts of the p53 protein are often related to mutations of its gene, we decided to explore the existence of p53 mutations in the tumor tissues of 9 patients bearing non-invasive corticotropinomas, excised by the transphenoidal route. We screened mutations in exons 5 to 8 of the p53 gene by the PCR-SSCP analysis. We were not able to find any mutation in the exons investigated. Our results are in close accordance with those obtained previously for other types of pituitary tumors.