Abstract
Purpose :
Even though rods outnumber cones by orders of magnitude, primate vision has evolved to mainly depend on cone pathways and most of our vision relies on the ~200,000 cones of the fovea. During development, all the different cell types of the retina are generated from a common population of multipotent progenitor cells in a stereotyped sequence but the molecular mechanism(s) that dictate why the progenitors of this region differentiate into cones exclusively and not into rods is not understood. Our previous studies have revealed that microRNAs (miRNAs) are key regulators of the progenitor competence to differentiate into specific subsets of cell types. miRNAs also regulate the progression of the developmental timing in the retina. Because the fovea is the region of the primate retina that develops first, we hypothesize that miRNAs and/or miRNA target molecules differentially expressed in the foveal progenitors could be playing key roles during foveal development.
Methods :
Retinal punches were obtained from embryonic retinas of Rhesus monkeys (Macaca mulatta) at the presumptive fovea (temporal) and in the equivalent region at the other side of the optic nerve head (nasal). We characterized the transcriptomic landscape of these tissues by RNAseq and microRNA-seq. The expression patterns of the top miRNAs enriched in the temporal samples were then analyzed by in situ hybridization using mouse, avian and human retinas. The top candidates were further tested by their ability to promote cone photoreceptor differentiation in primary cultures, and we also tested whether these miRNAs elicit changes in the cell cycle dynamics of retinal progenitor cells, using 5-ethynyl-2'deoxyuridine (EdU) cumulative labeling.
Results :
We have identified several miRNAs differentially expressed in the temporal vs nasal developing primate eye. Interestingly, some of these miRNAs showed central-to-periphery expression gradient by in situ hybridization. In particular, miR-15b was highly enriched in the central retina in embryonic day 13 mouse samples, and in HH26 chicken retinas. Interestingly, the overexpression of foveal miRNAs also promoted cone differentiation/maturation and changed cell cycle progression in retinal progenitors.
Conclusions :
Our data indicates that miRNAs may be playing essential roles during foveal development and further suggests that miRNAs coordinate retinal progenitor competence withcell cycle length.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.