Mecanismos reguladores da sintese de globinas : avaliação funcional da região R/PYR e analise da expressão genica diferencial na persistencia hereditaria de hemoglobina fetal e na delta-beta talassemia / Regulatory mechanisms of globin syntheis : functional evaluation of R/PYR region and differential gene expression analysis in hereditary persistence of etal hemoglobin and delta-beta thalassemia

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The genetic mechanisms underlying the continued expression of the ?-globin genes during the adult stage in deletional hereditary persistence of fetal hemoglobin (HPFH) and ??-thalassemias are not completely understood. For deletional HPFH, three main hypotheses were proposed to explain the relationship between these deletions and the non-suppression of ? -genes in the adult; 1- the removal of competitive regions that interact with the LCR; 2- the juxtaposition of enhancer elements located downstream from the breakpoint region; and 3- the removal of gene silencer elements. Herein, we studied a region, called R/PYR, that lies 1-3 Kb upstream from the ? gene. This region has been implicated in ? globin repression and globin gene switching. Stable transfections in MEL cells suggest a possible involvement of R/PYR in globin regulation. We also investigated the possible involvement of transcription factors, using the SSH method to identify differentially expressed transcripts in reticulocytes from a normal and a HPFH-2 subject. Some of the detectable transcripts may participate in globin gene regulation. Quantitative RT-PCR experiments confirmed the downregulation of ZHX2, a transcriptional repressor, in two HPFH-2 subjects and in a carrier of the Sicilian ??-thalassemia trait. The chromatin remodeling factors ARID1B and TSPYL1 had a very similar pattern of expression with an incremental increase in HPFH and decreased expression in ??-thalassemia. These differences suggest a mechanism to explain the heterocellular and pancellular distribution of F cells in ??-thalassemia and deletional HPFH, respectively. Interestingly, ??globin mRNA levels were decreased, similar to ?-globin in all reticulocyte samples analyzed, which may be the result of a common regulatory process affecting ?-like and ?-like globin synthesis. Part of the altered gene expression detected within the subtracted libraries may be an indirect effect due to the increased concentration of HbF in the cells. However, genetic alterations similar to those presented in this work may be implicated in the perturbation of chromosome interactions and/or disruption of the expression of regulatory non-coding transcripts with functional consequences for cellular gene expression. Additionally, other genes may have modifications of their expression, but were not detected in our experiments. To our knowledge, this is the first description of wide-ranging gene expression alterations in cells containing deletional HPFH and thalassemia. Finally, the dissection of the differential expression data presented in this study may help elucidate important pathways of erythroid differentiation and maintenance of red cells in peripheral circulation, as well as aid in the understanding of genetic mechanisms involved in erythrocyte pathologies such as sickle cell disease and thalassemias

ASSUNTO(S)

dna globinas thalassemias dna talassemia expressão genica gene expression globin

ACESSO AO ARTIGO

Documentos Relacionados