RESUMEN
Hereditary persistence of fetal hemoglobin deletion type-2 (HPFH-2) and Sicilian-δß-thalassemia are conditions described as large deletions of the human ß-like globin cluster, with absent ß-globin chains and a compensatory variable increase in γ-globin. HPFH, in general, may be distinguished from DB-Thalassemia by higher fetal hemoglobin (HbF) levels, absence of anemia and hypochromic and microcytic erythrocytes. MicroRNAs (miRNAs) regulate a range of cellular processes including erythropoiesis and regulation of transcription factors such as the BCL11A and SOX6 genes, which are related to the regulation of γ-globin expression. In this report, a possible association among the overexpression of miRNAs and the expression of the γ-globin gene was analyzed in these two conditions. Forty-nine differentially expressed miRNAs were identified by microarrays in CD34+-derived erythroid cells of two subjects heterozygous for Sicilian-δß-thalassemia, 2 for HPFH-2 and 3 for controls after 13 days of culture. Some of these miRNAs may participate in γ-globin gene regulation and red blood cell function. The BCL11A gene was found to be potentially targeted by 12 miRNAs that were up-regulated in HPFH-2 or in DB-Thal. A down-regulation of BCL11A gene expression in HPFH-2 was verified by quantitative polymerase chain reaction. These data suggest an important action for miRNA that may partially explain the phenotypic differences between HPFH-2 and Sicilian δß-thalassemia and the increased expression of γ-globin in these conditions.
Asunto(s)
Proteínas Portadoras/genética , Hemoglobina Fetal/genética , MicroARNs/genética , Proteínas Nucleares/genética , Factores de Transcripción SOXD/genética , Globinas beta/genética , Talasemia beta/genética , Talasemia delta/genética , gamma-Globinas/genética , Antígenos CD34/metabolismo , Secuencia de Bases , Regulación hacia Abajo/genética , Femenino , Humanos , Masculino , MicroARNs/biosíntesis , Reacción en Cadena en Tiempo Real de la Polimerasa , Proteínas Represoras , Análisis de Secuencia de ADN , Eliminación de Secuencia/genética , gamma-Globinas/metabolismoRESUMEN
Fetal hemoglobin (Hb F) is characteristic of the fetal development period. However, in some genetic conditions, such as hereditary persistence of fetal hemoglobin (HPFH) and delta-beta thalassemia (뫧-thalassemia), Hb F continues to be produced in adulthood. We evaluated the frequency of two mutations of HPFH, HPFH-1 and HPFH-2 African, and two mutations in 뫧-thalassemia, Sicilian and Spanish, in a Brazilian population. Peripheral blood samples were collected from adults from hospitals and blood centers in southeast and northeast Brazil. These individuals were healthy and without complaints of anemia, but had increased Hb F. Samples were submitted to electrophoretic and chromatographic analyses to quantify Hb F values and, subsequently, to molecular analyses to verify the mutations. In the molecular analysis, 16 of the 60 samples showed a heterozygous profile for the HPFH mutations, two for HPFH-1 and 14 for HPFH-2. In the same sample set, three were heterozygous for Spanish 뫧-thalassemia and none were heterozygous for Sicilian 뫧- thalassemia. The Hb F values in the HPFH-2 heterozygotes differed from those previously reported for this mutation. In this group, the HPFH mutations were more frequent than the 뫧-thalassemia mutations. The finding of these mutations in this Brazilian population reflects the mixing process that occurred during its formation.