Figure 4. miR-219, -138, and -338 are most highly expressed by OLs in the CNS and are induced specifically by mitogen withdrawal.

A. miRNA expression was compared between OPCs and OLs. Averaged results from 4x two-color microarrays are shown. “Cand” = candidate miRNAs at the time of microarray printing. Hsa, mmu, and dre = human, mouse, and zebrafish annotated miRNAs. B. qRT-PCR to determine relative OL/OPC expression level of individual miRNAs. Error bars ±S.E.M.; n=3 samples, 4x independent qRT-PCR runs per sample. C. qRT-PCR to determine expression levels of miR-219, -138, and -338 in acutely purified P5 or P17 neurons and astrocytes, P7 OPCs, P14 GC⁺ MOG⁻ immature OLs, and P14 MOG⁺ mature OLs (left), or in OPCs cultured for 7 DIV in indicated media: ±PDGF±T3 (right). Error bars ±S.E.M., n=2–8 samples. D. Northern blot showing mature miR-219 expression in acutely purified P23 Olig2^Cre/+;Dicer1^f/+ OLs (+/−), which is strongly reduced in Olig2^Cre/+;Dicer1^f/f OLs (−/−). Blots were stripped and re-probed for U6 snRNA as loading control. E–G. In situ hybridizations showing expression of PLP (E) and miR-219 (F) in sagital sections of a wt P17 mouse brain, compared to short LNA negative control probe (G). Boxed regions in E1–G1 shown at higher magnification in E2–G2, corpus callosum outlined by dashed lines. See also Fig. S5, Table S1.