Purchase this article with an account.
Brian G Ballios, Justin Belair-Hickey, Saeed Khalili, Kenneth Grise, Brenda BLK Coles, Jeff Liu, Gilbert Bernier, Valerie Wallace, Gary Bader, Molly S Shoichet, Derek van der Kooy; Lineage specification and molecular characterization of cone photoreceptor progenitors in the developing mammalian retina. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2932.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Adult retinal stem cells (RSCs) give rise to all retinal cell types. Clonal RSC progeny treated with taurine/retinoic acid (T+RA) produce 95% rod progeny, while coco (BMP/Wnt/TGFβ triple-inhibitor) induces 60% cones. We hypothesized that cone lineage-specific progenitors, specified using exogenous factors, display unique transcriptome signatures that can identify stage-specific molecular markers. No markers exist for these lineage-specific progenitors and literature is divided on their existence in vivo.
Adult RSCs were isolated from mouse and human donor eyes, while neural retinal progenitor cells (RPCs) were isolated from the embryonic mouse retina. We used single cell/well sorting to isolate individual progenitor clones.
Embryonic RPCs (E14) show similar rod differentiation in T+RA (>95%) compared to adult RSCs and increased cone differentiation in coco (>90%). Coco permitted differentiation from single non-pigmented RSC progeny to >95% cone-only clones, while single pigmented RSC progeny were unable to produce any cones. Constant coco exposure causes E12, E14 and E19 RPCs to adopt a cone-restricted fate. We compared gene expression between RSC-derived and endogenous cones with RNAseq, and profiled the transcriptome throughout rod and cone differentiation from embryonic RPCs. Principal component analysis showed a distinct progression of rod and cone lineages. Pathway analysis showed clustering of stem cell-derived and endogenous cones, as well as candidate progenitor markers. SOX15 may be a unique marker of a cone restricted progenitor; its expression follows other factors that bias photoreceptor differentiation, including OTX2 and OLIG2. SOX15 is expressed in early proliferating RPCs in vivo, and persists in some early-born post-mitotic cells, but not photoreceptors. SOX15 knockdown reduced colony formation from E14 RPCs, but not E19 RPCs or adult RSCs. After 4-6 weeks of coco, 60% of human RSC progeny differentiated into cones; both the time-course and efficiency is similar to mouse RSC progeny.
Exogenous signals instruct early lineage decisions in fate-restricted retinal progenitors, and we identify potentially new markers. SOX15 may promote cone differentiation by prolonging or promoting proliferation of early RPCs, or by inhibiting factors that specify alternative, late-born, cell fates and promoting a default cone differentiation.
This is a 2021 ARVO Annual Meeting abstract.
This PDF is available to Subscribers Only