Biology subjects

Tangeman, J.

Publications and source records attributed to Tangeman, J..

6 recordsLinked to original sources

bioRxiv2026

The extreme diversity of retinal amacrine cells has deep evolutionary roots

Amacrine cells (ACs) comprise a heterogeneous class of inhibitory neurons in the vertebrate retina, exhibiting morphological and functional complexity rivaling that of cortical interneurons. Here, we integrate single-cell and single-nucleus transcriptomic atlases from 24 vertebrate species to reconstruct the evolutionary origins of this extreme diversity. We identify 42 orthologous AC types (oACs), most of which exhibit a one-to-one correspondence across amniotes and, in many cases, across vertebrates. While core molecular identities are conserved, AC types vary in abundance and gene expression across species, likely reflecting adaptations to distinct visual ecologies. AC diversity scales with that of retinal ganglion cells (RGCs), indicative of co-evolution. Finally, we suggest that ACs arose from an AC-RGC hybrid precursor, with glycinergic ACs diverging early in vertebrate evolution, followed by a bifurcation between RGCs and GABAergic ACs. Together, these findings establish a unified evolutionary framework for understanding the diversity, development, and function of a class of inhibitory neurons across vertebrates.

neuroscience↗

bioRxiv2026

Sox8 and Sox9 regulate differentiation and nuclear positioning of retinal Muller glia.

Temporal patterning of retinal progenitor cells governs the sequential generation of retinal cell types, with gliogenesis occurring late in development. Sox8 and Sox9, members of the SoxE transcription factor family, are highly expressed in late-stage retinal progenitor cells and mature Muller glia, yet their functional roles remain incompletely defined. Here we employed gain- and loss-of-function approaches, single-cell multiomic profiling, and injury models to investigate Sox8/9 function. Overexpression of SOX8 and/or SOX9 in early-stage retinal progenitor cells suppressed early-born cell fates and promoted photoreceptor generation, consistent with a role in late-stage temporal identity. Conversely, conditional deletion of Sox8 and/or Sox9 in late-stage progenitors did not impair Muller glia specification, but caused radial displacement of Muller glia nuclei into the outer retina and modest changes in glial gene expression. Loss of Sox8/9 in mature Muller glia modestly increased proliferation post-injury without inducing neurogenic competence. These findings suggest that Sox8/9 are dispensable for gliogenesis and repression of neurogenic competence, but are essential for proper laminar positioning and maturation of retinal Muller glia.

neuroscience↗

bioRxiv2025

Comparative single-cell multiomic analysis reveals evolutionarily conserved and species-specific cellular mechanisms mediating natural retinal aging.

Biological age is a major risk factor in the development of common degenerative retinal diseases such as age-related macular degeneration and glaucoma. To systematically characterize molecular mechanisms underlying retinal aging, we performed integrated single- cell RNA- and ATAC-Seq analyses of the retina and retinal pigment epithelium (RPE) across the natural lifespan in zebrafish, mice, and humans. By profiling gene expression and chromatin accessibility, we identified extensive cell type- and species-specific aging-dependent changes, with a much smaller number of broadly expressed and conserved genes that include regulators of inflammation and autophagy. We constructed predictive aging clocks for retinal cell types and observed dynamic, reversible shifts in cellular age following acute injury. Spatial transcriptomic analysis revealed region-specific aging signatures and proximity effects, with Muller glia exhibiting pro-rejuvenating influences on neighboring neurons. Targeted Muller glia-specific induction of Yamanaka factors reduced molecular age in rod photoreceptors and bipolar cells without altering glial age. Our findings define conserved and divergent regulatory and signaling pathways mediating retinal aging, highlighting Muller glia as potential therapeutic targets for combating age-associated retinal dystrophies.

neuroscience↗

bioRxiv2025

Heterochronic transcription factor expression drives cone-dominant retina development in 13-lined ground squirrels.

Evolutionary adaptation to diurnal vision in ground squirrels has led to the development of a cone-dominant retina, in stark contrast to the rod-dominant retinas of most mammals. The molecular mechanisms driving this shift remain largely unexplored. Here, we perform single-cell RNA sequencing (scRNA-Seq) and chromatin accessibility profiling (scATAC-Seq) across developmental retinal neurogenesis in the 13-lined ground squirrel (13LGS) to uncover the regulatory basis of this adaptation. We find that 13LGS cone photoreceptors arise not only from early-stage neurogenic progenitors, as seen in rod-dominant species like mice, but also from late-stage neurogenic progenitors. This extended period of cone generation is driven by a heterochronic shift in transcription factor expression, with cone-promoting factors such as Onecut2, Pou2f1, and Zic3 remaining active in late-stage progenitors, and factors that promote cone differentiation such as Thrb, Rxrg, and Mef2c expressed precociously in late-stage neurogenic progenitors. Functional analyses reveal that Zic3 and Mef2c are sufficient to promote cone and repress rod photoreceptor-specific gene expression, and act through species-specific regulatory elements that drive their expression in late-stage progenitors. These results demonstrate that modifications to gene regulatory networks underlie the development of cone-dominant retinas, and provide insight into mechanisms of sensory adaptation and potential strategies for cone photoreceptor regeneration in vision disorders.

neuroscience↗

bioRxiv2023

Macrophages modulate fibrosis during newt lens regeneration

Previous studies indicated that macrophages play a role during lens regeneration in newts, but their function has not been tested experimentally. Here we generated a transgenic newt reporter line in which macrophages can be visualized in vivo. Using this new tool, we analyzed the location of macrophages during lens regeneration. We uncovered early gene expression changes using bulk RNAseq in two newt species, Notophthalmus viridescens and Pleurodeles waltl. Next, we used clodronate liposomes to deplete macrophages, which inhibited lens regeneration in both newt species. Macrophage depletion induced the formation of scar-like tissue, an increased and sustained inflammatory response, an early decrease in iris pigment epithelial cell (iPEC) proliferation and a late increase in apoptosis. Some of these phenotypes persisted for at least 100 days and could be rescued by exogenous FGF2. Re-injury alleviated the effects of macrophage depletion and re-started the regeneration process. Together, our findings highlight the importance of macrophages in facilitating a pro-regenerative environment in the newt eye, helping to resolve fibrosis, modulating the overall inflammatory landscape and maintaining the proper balance of early proliferation and late apoptosis.

developmental biology↗

bioRxiv2019

DNA demethylation is a driver for chick retina regeneration

BackgroundA promising avenue toward human retina regeneration lies in identifying the factors that promote cellular reprogramming to retinal neurons in organisms able to undergo retina regeneration. The embryonic chick can regenerate a complete neural retina, after retinectomy, via retinal pigment epithelium (RPE) reprogramming in the presence of FGF2. Cellular reprogramming resets the epigenetic landscape to drive shifts in transcriptional programs and cell identity. Here, we systematically analyzed the reprogramming competent chick RPE prior to injury, and during different stages of reprogramming. We examined the dynamic changes in the levels and distribution of histone marks and DNA modifications, as well as conducted a comprehensive analysis of the DNA methylome during this process.\n\nResultsIn addition to changes in the expression of genes associated with epigenetic modifications during RPE reprogramming, we observed dynamic changes in histone marks and intermediates of the process of DNA demethylation. At early times after injury, H3K27me3 and 5mC repression marks decreased while 5caC and the H3K4me3 activation mark increased, suggesting genome-wide changes in the bivalent chromatin, impaired DNA methylation, and active DNA demethylation in the chromatin reconfiguration of reprogramming RPE. Comprehensive analysis of the methylome by whole-genome bisulfite sequencing (WGBS) confirmed extensive rearrangements of DNA methylation patterns including differentially methylated regions (DMRs) found at promoters of genes associated with chromatin organization and fibroblast growth factor production. In contrast, genes associated with early RPE reprogramming are hypomethylated in the intact RPE and remain hypomethylated during the process. During the generation of a neuroepithelium (NE) at later stages of reprogramming, decreased levels of H3K27me3, 5mC, and 5hmC coincide with elevated levels of H3K27Ac and 5caC, indicating an active demethylation process and genome-wide changes in the active regulatory landscape. Finally, we identify Tet methylcytosine dioxygenase 3 (TET3) as an important factor for DNA demethylation and retina regeneration in the embryonic chick, capable of reprogramming RPE in the absence of exogenous FGF2.\n\nConclusionOur results demonstrated that injury signals early in RPE reprogramming trigger genome-wide dynamic changes in chromatin, including bivalent chromatin and DNA methylation. In the presence of FGF2 these dynamic modifications are further sustained in the commitment to form a new retina. We identify DNA demethylation as a key process driving the process of RPE reprogramming and identified TET3 as a factor able to reprogram RPE in absence of FGF2. Our findings reveal active DNA demethylation as an important process that may be applied to remove the epigenetic barriers in order to regenerate retina in mammals.

developmental biology↗