ABSTRACT: MicroRNAs (miRNAs) are small non-coding RNAs (sncRNAs) crucial for post-transcriptional and translational regulation of cellular and developmental pathways. Study of miRNAs in erythropoiesis thus elucidates the process and facilitates diagnosis and therapy development for related disorders. Here, we used high-throughput DNA Nanoball small RNA sequencing to characterise sncRNAs, and in particular miRNAs, comprehensively in human erythroid cell cultures. Based on primary human peripheral-blood-derived CD34+ (hCD34+) cells and on two influential erythroid cell lines with adult and fetal expression patterns, HUDEP-2 and HUDEP-1, respectively, our study links differential expression (DE) to erythroid differentiation, cell type, and fetal and adult hemoglobin expression patterns. Sequencing results were validated by reverse-transcription quantitative PCR (RT-qPCR) of selected DE miRNAs (miR-451a, miR-182-5p, miR-146a-5p, miR-221-3p, miR-222-3p) and indicated overall common erythroid differentiation signatures in primary cells and cell lines, in terminal stages of erythropoiesis characterized by decreased complexity of global miRNA expression and reciprocally increased expression of individual lineage-specific miRNAs. Interestingly, against a backdrop of evident clustering and thus similarity of same-stage hCD34+ and HUDEP-2 cells, differential expression of several miRNAs highlighted readily interpretable discrepancies between both cell types. Moreover, differential expression analysis between the closely related HUDEP-2 and HUDEP-1 cells provided pointers to miRNAs, transcription factors (TFs), target genes, and pathways mechanistically linked to globin switching. In resulting TF-miRNA co-regulatory networks, TFs known to be implicated in hemoglobin switching, including the major γ-globin repressors BCL11A and ZBTB7A, were targeted by many co-regulated miRNAs, outlining intricate combinatorial miRNA regulation of globin expression in erythroid cells.
