Global Gene Expression Revealed a Set of Genes Involved in the Modification of Cells during Erythropoiesis.

Erythroid differentiation is a dynamic and complex process in which a pluripotent stem cell undergoes a series of developmental changes that commit it to a specific lineage. These alterations involve changes in gene expression profiles. Extensive studies have led to a considerable understanding of the cellular and molecular control of hemoglobin production during red blood cell differentiation, however, a complete understanding of human erythropoiesis will require a robust description of the entire transcriptome of these cells during differentiation. From a global point of view of cell metabolic regulation, where genomic information could be complemented with gene expression, the use of methods that enable quantification of the entire transcriptome of the red blood cell during differentiation is of great importance. In this study, the gene expression profiles during differentiation of Human erythroid cells of a normal blood donor in a two-phase liquid culture (Fibach & Rachmilewitz, 1993) were evaluated using Serial analysis of gene expression (SAGE). Global gene expression was evaluated in cells collected immediately before the addition of erythropoeitin (0 hour) and 192 and 336 hours after the addition of this hormone. We generated a total of 30512 tags at 0h, 30117 tags at 192h and 30189 tags at 336h, representing 12026, 11709 and 11337 unique tags, respectively. In the 0h library, a high expression of ferritin genes and CD74 antigen gene was observed. As expected, the expression of globin genes started during intermediate stages of differentiation (predominantly basophilic erythroblasts) and were the most expressed genes at the end of the culture (predominantly orthocromatic erythroblasts). Ribosomal genes were the most expressed genes at 192 hours, indicating an increase in protein synthesis. To identify the genes that were differentially expressed between the libraries, a P value < 0.01 and fold ≥ 5 were considered as statistically significant. In the comparison of the 0h and 192h libraries, 179 differentially expressed transcripts were identified. From these genes, in addition to the globin genes, we found an up-regulation of several genes related to protein binding (LXN, GSTM3, and TRIP6), transcription factor (GATA-1), hydrolase activity (TPSAB1), ion transport (SLC12A9) and regulation of apoptosis (PRDX2). Comparing the 192h and 336h libraries, 103 differentially expressed transcripts were identified. The up-regulated genes were generally related to hemoglobin synthesis, such as ALAS2, involved in the biosynthesis of the heme group or related to intracellular transport such as MSCP and NUDT4 and cell differentiation such as GDF15. The transcription of some of these genes, such as SLC12A9, TRB3, EYA3 and TWIST2 are described for the first time during erythroid differentiation. The results indicated that the global aspects of the transcriptome were similar during differentiation for the majority of the genes and that probably a relative small set of genes is involved in the modification of erythroid cells during differentiation. The results of this study amplify the previous published data (Komor et al, 2005) and may contribute to the comprehension of erythroid differentiation and identification of new target genes involved in some erythroid diseases.