Proteomic analysis of hemoglobin H-constant spring (Hb H-CS) erythroblasts.

Hemoglobin H disease (Hb H) arises through the loss or dysfunction of three of the four alpha globin genes through the co-inheritance of either gross gene deletions or an abnormal hemoglobin which causes a non-deletional loss of α-globin expression. This study sought to investigate erythropoiesis in Hb H-Constant Spring (Hb H-CS) disease, a common form of Hb H disease in Southeast Asia, caused by the inheritance of the Constant Spring variant hemoglobin together with deletion of two of the alpha globin genes. In comparison to normal erythroblasts, Hb H-CS erythroblasts showed reduced cell expansion although no difference in differentiation was observed.

Increased oxidative metabolism is associated with erythroid precursor expansion in β0-thalassaemia/Hb E disease.

Erythropoiesis in β0-thalassaemia/Hb E patients, the most common variant form of β-thalassaemia in Southeast Asia, is characterized by accelerated differentiation and over-expansion of erythroid precursor cells. The mechanism driving this accelerated expansion and differentiation remain unknown. To address this issue a proteomic analysis was undertaken to firstly identify proteins differentially expressed during erythroblast differentiation and a second analysis was undertaken to identify proteins differentially expressed between β0-thalassaemia/Hb E erythroblasts and control erythroblasts.

Enhanced activation of autophagy in β-thalassemia/Hb E erythroblasts during erythropoiesis.

Erythropoiesis in β-thalassemia patients is ineffective, primarily because of death of the erythroid progenitor cells at the polychromatic normoblast stage. While it is known that autophagy plays a critical role during erythropoiesis by removing organelles from erythroid cells during terminal differentiation, its role in erythroid cells whose function is impaired remains to be explored. To investigate this, CD34+ erythroid progenitor cells from normal controls and β-thalassemia/Hb E patients were isolated from peripheral blood and cultured under conditions driving differentiation into an erythroid lineage, and levels of autophagy and apoptosis were analyzed both directly and after biochemical manipulation with L: -asparagine.

A mechanism of ineffective erythropoiesis in β-thalassemia/Hb E disease.

Background: Cells respond to stress stimuli through a number of response pathways, of which one of the most important and well characterized is the unfolded protein response. Despite a large body of work which suggests that stress in erythroblasts may play a pivotal role in the pathogenesis of beta-thalassemia/Hb E disease, this pathway remains uninvestigated.

Design And Methods: Day 10 erythroblasts from normal controls and beta-thalassemia/Hb E patients were subjected to internal (treatment with tunicamycin) and external (serum and growth factor withdrawal) stress stimuli and the activation of the unfolded protein response pathway was investigated.

Increased erythropoiesis of beta-thalassaemia/Hb E proerythroblasts is mediated by high basal levels of ERK1/2 activation.

Beta-thalassaemia is one of the most common inherited anaemias, arising from a partial or complete loss of beta-globin chain synthesis. In severe cases, marked bone marrow erythroid hyperplasia, believed to result from erythropoietin (EPO)-mediated feedback from the anaemic condition is common, however, as yet, no study has investigated EPO-mediated signal transduction in thalassaemic erythroid cells. Using proerythroblasts generated from peripheral blood circulating CD34+ haematopoietic progenitor cells, the activation of the mitogen-activated protein kinase/extracellular signal-regulated kinases (MAPK/ERKs) pathway was examined under conditions of steady state growth, cytokine deprivation and post-EPO stimulation.