Orchestrated intron retention regulates normal granulocyte differentiation [Affymetrix arrays]

Using mRNA-seq, we determined intron retaining genes that were differentially regulated in FACS purified cells at three progressive stages of mouse granulopoiesis; CD34+Kit+Gr-1low promyelocytes, CD34-Kit-Gr-1mid myelocytes and CD34-Kit-Gr-1high granulocytes. We found that IR affects 86 genes, including those specific to granulocyte (Lyz2 and MMP8) and nuclear architecture (Lmnb1 and Lbr). IR was associated with the decrease in protein levels measured by mass spectrometry (P=0.0015, binomial test). Inhibition of NMD in granulocytes resulted in marked accumulation of 39/86 intron retaining mRNAs (P<0.05, RUV procedure with Holm-Bonferroni correction), indicating that IR triggers NMD to downregulate mRNA and protein expression. We used Affymetrix's Mouse Gene 1.0 ST array to determine accumulation of RNA-transcripts following inhibition of nonsense-mediated decay in primary mouse granulocytes using caffeine.