Emergence of dorsal-ventral polarity in ES cell-derived retinal tissue

Abstract

We previously demonstrated that mouse embryonic stem cell (mESC)-derived retinal epithelium self-forms an optic cup-like structure. In the developing retina, the dorsal and ventral sides differ in terms of local gene expression and morphological features. This aspect has not yet been shown in vitro. Here, we demonstrate that mESC-derived retinal tissue spontaneously acquires polarity reminiscent of the dorsal-ventral (D-V) patterning of the embryonic retina. Tbx5 and Vax2 were expressed in a mutually exclusive manner, as seen in vivo. Three-dimensional morphometric analysis showed that the in vitro-formed optic cup often contains cleft structures resembling the embryonic optic fissure. To elucidate the mechanisms underlying the spontaneous D-V polarization of mESCderived retina, we examined the effects of patterning factors, and found that endogenous BMP signaling plays a predominant role in the dorsal specification. Further analysis revealed that canonical Wnt signaling, which was spontaneously activated at the proximal region, acts upstream of BMP signaling for dorsal specification. These observations suggest that D-V polarity could be established within the self-formed retinal neuroepithelium by intrinsic mechanisms involving the spatiotemporal regulation of canonical Wnt and BMP signals.

Spatio-temporal relays control layer identity of direction-selective neuron subtypes inDrosophila

“…Interestingly, the progressive refinement of NE patterning by the induction of secondary signaling centers plays a central role in vertebrate brain development 47 . Furthermore, similar signaling cascades have been recently identified in mammalian 3D optic tissue cultures where sequential Wnt and Bmp signaling induces the expression of the Omb-related T-box transcription factor Tbx5 to specify dorsal identity of retinal NE cells 50 . Hence, such cascades could represent conserved regulatory modules that are employed repeatedly during invertebrate and vertebrate nervous system development.…”

“…The vertebrate roof plate and the cortical hem, for instance, both release Wnts and Bmps to pattern NE cells in the developing dorsal spinal cord and in the surrounding forebrain, respectively [47][48][49] . In the Drosophila visual system, the GPC areas express wg and pattern the OPC by inducing dpp expression in adjacent dorsal and ventral OPC subdomains 26 50 . Hence, such cascades could represent conserved regulatory modules that are employed repeatedly during invertebrate and vertebrate nervous system development.…”

Concerted action of neuroepithelial basal shrinkage and active epithelial migration ensures efficient optic cup morphogenesis

“…Consequently, this could help the cells to attain the RNE fate in a stepwise manner to prepare for the later retinal developmental programs. As it has been recently suggested that such patterning could be conserved during in vitro optic cup formation in organoid cultures (Hasegawa et al, 2016) it will in the future be very exciting to assess how far developmental and cell-behavioral patterning in retinal organoids recapitulates the in vivo scenario at different developmental stages.…”

An Eye Organoid Approach Identifies Six3 Suppression of R-spondin 2 as a Critical Step in Mouse Neuroretina Differentiation

“…Besides, global gene analysis using ESCs-derived neuroretina and RPE showed that maintenance (or transition) of these cell types largely relies on canonical Wnt/β-catenin signaling (Andrabi et al, 2015). Wnt/β-catenin signaling is also required to maintain dorsal retinal identity (Hagglund et al, 2013; Hasegawa et al, 2016), and we previously showed that Wnt inhibition is required for neuroretina fate specification (Liu et al, 2010). Haploinsufficiency in the major extracellular Wnt antagonist, dickkopf-1 ( Dkk1 ), results in coloboma and anterior eye defects, implying that at least certain aspects of eye development are Wnt-dosage dependent (Lieven and Ruther, 2011).…”