Examples of miRNAs expressed in the retina and the retinal pigment epithelium. (A): Representative examples of possible amacrine-expressed (top bracket) and photoreceptor-expressed (lower bracket) miRNAs. Most of the retinal patterns are already detectable at E16.5 and P0, often with a specificity that is maintained throughout life. For miR-409-5p, miR-433, miR-541 and miR-742 (top bracket; panel A) a weak staining is detectable in the inner neuroblastic layer (INBL; blue arrowheads) at P0. At P8 and P60, these miRNAs are expressed in the ganglion cell layer (GCL; red arrows) and the inner nuclear layer (INL; blue arrows), with stronger expression in the vitreal part of the latter where amacrine cells reside. The retinal distribution of the above miRNAs had not been previously described. miR-96 and miR-184 (lower bracket; panel A) are examples of miRNAs that stain the outer nuclear layer (ONL; green arrows) and/or the photoreceptors at P8 and P60 while at P0 they are detected in the outer neuroblastic layer (ONBL; green arrowheads). (B): miR-542-3p shows an apparent low-dorsal to high-ventral gradient expression in the developing retina at E16.5 and P0. (C): Representative examples of miRNAs expressed in the retinal pigment epithelium (RPE). Red arrowheads indicate the RPE monolayer.