Expressão genica diferencial em reticulocitos de pacientes com doença da hemoglobina H / Differential gene expression in reticulocytes of Hemoglobin H disease patients

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Hb H disease results from the inactivation of three of the four alfa -globin genes normally present on diploid genome and it is characterized by a moderate to severe chronic hemolytic anemia. Patients usually present microcytosis, hypochromia and poikilocytosis, with 25 to 30% of Hb Bart?s (?4) at birth and 5 to 30% of Hb H (?4) in adult life. Although the molecular base of this disease influences the Hb H levels produced, some heterogeneity has been observed in relation to this aspect, even in patients with identical ? genotypes, thus suggesting that other factors contribute to this diversity besides ?-thalassemic determinants. The aim of the present study was to identify differentially expressed transcripts in the reticulocytes from two patients with Hb H disease, siblings, from Chinese and African origins, a 21-year- old male (MKS) with 18% of Hb H and a 19-year-old female (FKS) with 5% of Hb H, both with genotype -?3.7/--SEA. The methodology involved two techniques: the Differential Display Reverse Transcription-Polymerase Chain Reaction (DDRT-PCR) and the Suppression Subtractive Hybridization (SSH). Quantitative real time PCR (qRT-PCR) experiments were used to confirm some results. Four differentially expressed profiles were obtained, all of them better represented in the subject with the highest Hb H level. Two transcripts were detected by both methodological approaches, one being highly similar to PIP5KIIA gene (Phosphatidylinositol ? 4 phosphate 5-kinase, type II ?) and the other one similar to human ?-globin gene. Two others transcripts were selected only by SSH and they showed to be to FAM 46C (Family with sequence similarity 46, member C) and EIF4E-BP1 (eukariotic translation initiation factor 4E-binding protein 1) gene homologues. In order to identify the mechanisms that are responsible for the transcripts PIP5KIIA and ?- globin increase in the reticulocytes from MKS patient, some other genes related to the transcriptional process also had its expression evaluated by qRT-PCR. Although not conclusive, our results suggest that the difference between the Hb H levels, showed by the subjects here studied, is correlated with ?-globin synthesis rate and that PIP5KIIA may participate of its regulation, probably by cell signalizing through Phosphatidylinositol. Studies, particularly involving a higher number of patients, and experiments aimed at elucidating the PIP5KIIA function in erythroid cells, should help to understand this process. The initiation factor -4E binding protein (EIF4E-BP1) and its capacity to bind to eIF4E, acts as negative regulator of cell growth. Its overexpression was detected in the patient with the highest HbH level. The significance of these findings and the role of the FAM46C and EIF4E-BP1 gene transcripts should be further investigated so that the regulating of the beta -globin gene expression in alfa -thalassemic patients can be better understood.

ASSUNTO(S)

alpha-thalassemia doença da hemoglobina h talassemia alfa phosphafidylinositol 4-phosphate-5-kinase hemoglobulin h disease globina alfa alpha globin fosfafidilinositol 4-fosfato-5-quinase

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