The human reticulocyte transcriptome

RNA from circulating blood reticulocytes was utilized to provide a robust description of genes transcribed at the final stages of erythroblast maturation. After depletion of leukocytes and platelets, Affymetrix HG- U133 arrays were hybridized with probe generated from the reticulocyte total RNA ( blood obtained from 14 umbilical cords and 14 healthy adult humans). Among the cord and adult reticulocyte profiles, 698 probe sets ( 488 named genes) were detected in each of the 28 samples. Among the highly expressed genes, promoter analyses revealed a subset of transcription factor binding motifs encoded at higher than expected frequencies including the hypoxia- related arylhydrocarbon receptor repressor family. Over 100 probe sets demonstrated differential expression between the cord and adult reticulocyte samples. For verification, the array expression patterns for 21 genes were confirmed by real-time PCR ( correlation coefficient 0.98). Only four transcripts ( MAP17, FLJ32009, ARRB2, and FLJ27365) were identified as being upregulated in the adult blood transcriptome. Further analysis revealed that the lipid-regulating protein MAP17 was present in the membrane fraction of adult erythrocytes, but not detected in cord blood erythrocytes. Combined with other clinical and experimental data, these reticulocyte transcriptome profiles should be useful to better understand the molecular bases of terminal erythroid differentiation, hemoglobin switching, iron metabolism and malarial patho-genesis.