Abstract
BackgroundMicroRNAs are ~22nt-long small non-coding RNAs that negatively regulate protein expression through mRNA degradation or translational repression in eukaryotic cells. Based upon their importance in regulating development and terminal differentiation in model systems, erythrocyte microRNA profiles were examined at birth and in adults to determine if changes in their abundance coincide with the developmental phenomenon of hemoglobin switching.MethodsExpression profiling of microRNA was performed using total RNA from four adult peripheral blood samples compared to four cord blood samples after depletion of plasma, platelets, and nucleated cells. Labeled RNAs were hybridized to custom spotted arrays containing 474 human microRNA species (miRBase release 9.1). Total RNA from Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines provided a hybridization reference for all samples to generate microRNA abundance profile for each sample.ResultsAmong 206 detected miRNAs, 79% of the microRNAs were present at equivalent levels in both cord and adult cells. By comparison, 37 microRNAs were up-regulated and 4 microRNAs were down-regulated in adult erythroid cells (fold change > 2; p < 0.01). Among the up-regulated subset, the let-7 miRNA family consistently demonstrated increased abundance in the adult samples by array-based analyses that were confirmed by quantitative PCR (4.5 to 18.4 fold increases in 6 of 8 let-7 miRNA). Profiling studies of messenger RNA (mRNA) in these cells additionally demonstrated down-regulation of ten let-7 target genes in the adult cells.ConclusionThese data suggest that a consistent pattern of up-regulation among let-7 miRNA in circulating erythroid cells occurs in association with hemoglobin switching during the fetal-to-adult developmental transition in humans.
Highlights
MicroRNAs are ~22nt-long small non-coding RNAs that negatively regulate protein expression through messenger RNA (mRNA) degradation or translational repression in eukaryotic cells
The fetal erythroid cells were identified as having increased abundance in 103 of 107 differentially regulated mRNAs
In addition to globin and other protein-encoding mRNA transcripts [12], miRNA species in circulating erythroid cells are differentially expressed in association with hemoglobin switching
Summary
MicroRNAs are ~22nt-long small non-coding RNAs that negatively regulate protein expression through mRNA degradation or translational repression in eukaryotic cells. Based upon their importance in regulating development and terminal differentiation in model systems, erythrocyte microRNA profiles were examined at birth and in adults to determine if changes in their abundance coincide with the developmental phenomenon of hemoglobin switching. MicroRNA (miRNA) is approximately 22 nucleotide long single-stranded RNA which regulates gene expression through either post-transcriptional gene silencing by pairing to target mRNA to trigger mRNA cleavage, trafficking of mRNA for degradation, or translational repression [1]. Based upon involvement of let-7 miRNA in the larval-to-adult transition in C. elegans and the juvenile-toadult transition in Drosophila, a similar function for let-7 miRNA in mammalian development is being explored [8]
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