miR-927 Regulates Photoreceptor Subtype Specification Through Yorkie and Sensory Opsins in Drosophila.

Binary cell fate decisions in the Drosophila retina generate R8 photoreceptor subtypes that express either blue-sensitive Rh5 or green-sensitive Rh6 opsins. These choices are governed by a Hippo pathway-dependent bistable switch, yet the mechanisms that couple pathway output to terminal opsin expression remain unclear. Here, we identify miR-927 as a regulator that biases R8 subtype fate. Loss of miR-927 increases Rh5-positive pR8 cells, whereas its overexpression promotes Rh6-positive yR8 identity. Mechanistically, miR-927 directly represses the terminal differentiation gene Rh5 and is capable of repressing the Hippo pathway effector yki through its 3'UTR. This dual targeting couples pathway output to terminal gene expression, providing a mechanism to bias and stabilize subtype identity. More broadly, our findings illustrate how microRNAs can be integrated into bistable signaling networks to modulate binary cell fate decisions.