The human retinal pigment epithelium (RPE) and choroid are complex tissues that provide crucial support to the retina. Disease affecting either of these supportive tissues can lead to irreversible blindness in the setting of age-related macular degeneration. In this study, single-cell RNA sequencing was performed on macular and peripheral regions of RPE-choroid from 7 human donor eyes in 2 independent experiments. In the first experiment, total RPE/choroid preparations were evaluated and expression profiles specific to RPE and major choroidal cell populations were identified. As choroidal endothelial cells represent a minority of the total RPE/choroidal cell population but are strongly implicated in age-related macular degeneration (AMD) pathogenesis, a second single-cell RNA-sequencing experiment was performed using endothelial cells enriched by magnetic separation. In this second study, we identified gene expression signatures along the choroidal vascular tree, classifying the transcriptome of human choriocapillaris, arterial, and venous endothelial cells. We found that the choriocapillaris highly and specifically expresses the regulator of cell cycle gene ( RGCC ), a gene that responds to complement activation and induces apoptosis in endothelial cells. In addition, RGCC was the most up-regulated choriocapillaris gene in a donor diagnosed with AMD. These results provide a characterization of the human RPE and choriocapillaris transcriptome, offering potential insight into the mechanisms of choriocapillaris response to complement injury and choroidal vascular disease in age-related macular degeneration.

The human choroid is a heterogeneous, highly vascular connective tissue that dysfunctions in age-related macular degeneration (AMD). In this study, we performed single-cell RNA sequencing on 21 human choroids, 11 of which were derived from donors with early atrophic or neovascular AMD. Using this large donor cohort, we identified new gene expression signatures and immunohistochemically characterized discrete populations of resident macrophages, monocytes/inflammatory macrophages and dendritic cells. These three immune populations demonstrated unique expression patterns for AMD genetic risk factors, with dendritic cells possessing the highest expression of the neovascular AMD-associated MMP9 gene. Additionally, we performed trajectory analysis to model transcriptomic changes across the choroidal vasculature, and we identified expression signatures for endothelial cells from choroidal arterioles and venules. Finally, we performed differential expression analysis between control, early atrophic AMD, and neovascular AMD samples, and we observed that early atrophic AMD samples had high expression of SPARCL1, a gene that has been shown to increase in response to endothelial damage. Likewise, neovascular endothelial cells harbored gene expression changes consistent with endothelial cell damage and demonstrated increased expression of the sialomucins CD34 and ENCM, which were also observed at the protein level within neovascular membranes. Overall, this study characterizes the molecular features of new populations of choroidal endothelial cells and mononuclear phagocytes in a large cohort of AMD and control human donors. Choroidal endothelial and immune cells are implicated in the pathogenesis of age-related macular degeneration (AMD). In a cohort of 11 AMD and 10 control human donors, Voigt et al. used single-cell RNA sequencing to identify gene expression changes across the choroidal endothelial cell and immune subpopulations. The background depicts a whole mount of human choroidal endothelial cells (red) and IBA1-expressing immune cells (green).

Wnt/β-catenin signaling is required for embryonic dermal fibroblast cell fate, and dysregulation of this pathway is sufficient to promote fibrosis in adult tissue. The downstream modulators of Wnt/β-catenin signaling required for controlling cell fate and dermal fibrosis remain poorly understood. The discovery of regulatory long non-coding RNAs (lncRNAs) and their pivotal roles as key modulators of gene expression downstream of signaling cascades in various contexts prompted us to investigate their roles in Wnt/β-catenin signaling. Here, we have identified lncRNAs and protein-coding RNAs that are induced by β-catenin activity in mouse dermal fibroblasts using next generation RNA-sequencing. The differentially expressed protein-coding mRNAs are enriched for extracellular matrix proteins, glycoproteins, and cell adhesion, and many are also dysregulated in human fibrotic tissues. We identified 111 lncRNAs that are differentially expressed in response to activation of Wnt/β-catenin signaling. To further characterize the role of mouse lncRNAs in this pathway, we validated two novel Wnt signaling- Induced Non-Coding RNA (Wincr) transcripts referred to as Wincr1 and Wincr2. These two lncRNAs are highly expressed in mouse embryonic skin and perinatal dermal fibroblasts. Furthermore, we found that Wincr1 expression levels in perinatal dermal fibroblasts affects the expression of key markers of fibrosis (e.g., Col1a1 and Mmp10), enhances collagen contraction, and attenuates collective cell migration. Our results show that β-catenin signaling-responsive lncRNAs may modulate dermal fibroblast behavior and collagen accumulation in dermal fibrosis, providing new mechanistic insights and nodes for therapeutic intervention.

While dysfunction and death of light-detecting photoreceptor cells underlie most inherited retinal dystrophies, knowledge of the species-specific details of human rod and cone photoreceptor cell development remains limited. Here, we generated retinal organoids carrying retinal disease–causing variants in NR2E3 , as well as isogenic and unrelated controls. Organoids were sampled using single-cell RNA sequencing (scRNA-Seq) across the developmental window encompassing photoreceptor specification, emergence, and maturation. Using scRNA-Seq data, we reconstruct the rod photoreceptor developmental lineage and identify a branch point unique to the disease state. We show that the rod-specific transcription factor NR2E3 is required for the proper expression of genes involved in phototransduction, including rhodopsin, which is absent in divergent rods. NR2E3-null rods additionally misexpress several cone-specific phototransduction genes. Using joint multimodal single-cell sequencing, we further identify putative regulatory sites where rod-specific factors act to steer photoreceptor cell development. Finally, we show that rod-committed photoreceptor cells form and persist throughout life in a patient with NR2E3-associated disease. Importantly, these findings are strikingly different from those observed in Nr2e3 rodent models. Together, these data provide a road map of human photoreceptor development and leverage patient induced pluripotent stem cells to define the specific roles of rod transcription factors in photoreceptor cell emergence and maturation in health and disease.