Biology subjects

Martins, R. A. P.

Publications and source records attributed to Martins, R. A. P..

4 recordsLinked to original sources

bioRxiv2024

Pou4f2/Brn3b Overexpression Promotes The Genesis Of Retinal Ganglion Cell-Like Projection Neurons From Late Progenitors

Retinal ganglion cells (RGCs) are the projection neurons of the retina. In early retinal progenitor cells (RPCs), Atoh7 orchestrates the developmental RGC program and regulates the expression of critical downstream targets, including Pou4f factors. The absence of Pou4f2 or more POU4F family genes results in defects in RGC differentiation, aberrant axonal elaboration and ultimately RGC death, confirming the requirement of POU4F factors for RGC development and survival, with a critical role in regulating RGC axon outgrowth and pathfinding. Here, we investigated in vivo whether ectopic Pou4f2 expression in late retinal progenitor cells (late RPCs) is sufficient to induce the generation of cells with RGC properties, including projecting axons to the brain. Using a strong ubiquitous promoter to induce Pou4f2 overexpression in neonates, we observed a change in targeted cell distribution in the retinal tissue, including the presence of cells in the ganglion cell layer and inner plexiform layer with high density of GFP+ processes along the retina. Similar results on the induction of neuron processes were obtained when we overexpressed Pou4f2 in Atoh7 knockout mice, suggesting that POU4F2 is sufficient to induce them. Single-cell RNA sequencing (scRNA-seq) analysis shows that several RGC-genes (such as Rbpms, Gap-43, Hs6st3, and Foxp2) are upregulated after Pou4f2 overexpression. Additionally, gene ontology analysis indicates the induction of genes related to axonogenesis and neuronal differentiation. Imaging throughout the visual pathway revealed high density of axons projecting toward the optic nerve head and extending to brain regions, such as the superior colliculus and geniculate nucleus. Thus, Pou4f2 induced neurons with specific RGC characteristics that share similarities with resident RGCs and notably project axons that reach brain targets. In conclusion, these results showed that POU4F2 alone was sufficient to promote critical properties of projection neurons from retinal progenitors outside their developmental window.

neuroscience↗

bioRxiv2024

Dissecting the ocular impact of SARS-CoV-2 variants: Analysis of eye globe and retina in animal models

Neurological and ocular manifestations were reported in COVID-19 patients and in SARS-CoV-2 infected animal models. However, the effects of SARS-CoV-2 variants of concern (VoC) on the eyes and the retina remain unclear. Here, we investigate the cellular and molecular consequences of SARS-CoV-2 VoC infection on the eye and retina in mice and hamsters. Infection with the ancestral SARS-CoV-2 and the Gamma VoC induced a subtle increase in the eye volume of K18-hAce2 mice, but no morphological alteration was observed in hamsters eyes. Evaluation of the ocular tropism revealed that distinct SARS-CoV-2 VoC reached the eye globe, but not the retina of K18-hAce2 mice. In contrast, SARS-CoV-2 variants are detected in the hamsters retina during both acute infection and after disease recovery. Despite the presence of viral RNA, no inflammation was observed in the hamster retina, as evidenced by unchanged microglial cell density and unaltered gene expression of several immune mediators. Altogether, these findings indicate a limited impact of SARS-CoV-2 variants on the eye and retina.

neuroscience↗

bioRxiv2020

ATRIP protects progenitor cells against DNA damage in vivo

The maintenance of genomic stability during the cell cycle of progenitor cells is essential for the faithful transmission of genetic information. Mutations in genes that ensure genome stability lead to human developmental syndromes. Mutations in Ataxia Telangiectasia and Rad3-related (ATR) or in ATR-interacting protein (ATRIP) lead to Seckel syndrome, which is characterized by developmental malformations and short life expectancy. While the roles of ATR in replicative stress response and chromosomal segregation are well established, it is unknown how ATRIP contributes to maintaining genomic stability in progenitor cells in vivo. Here, we generated the first mouse model to investigate ATRIP function. Conditional inactivation of Atrip in progenitor cells of the CNS and eye led to microcephaly, microphthalmia and postnatal lethality. To understand the mechanisms underlying these malformations, we used lens progenitor cells as a model and found that ATRIP loss promotes replicative stress and TP53-dependent cell death. Trp53 inactivation in Atrip-deficient progenitor cells rescued apoptosis but increased mitotic DNA damage and mitotic defects. Our findings demonstrate an essential role of ATRIP in preventing DNA damage accumulation during unchallenged replication.

cell biology↗

bioRxiv2018

De novo genesis of retinal ganglion cells by targeted expression of KLF4 in vivo

Retinal ganglion cell (RGC) degeneration is a hallmark of glaucoma, the most prevalent cause of irreversible blindness. Thus, innovative therapeutic strategies are needed to protect and replace these projection neurons. It has been shown that endogenous glial cells of the retina, Muller cells, can be directly reprogrammed into late-born retinal interneurons. However, since RGCs are the first neurons born during development, the replacement of damaged RGCs requires the reprograming to an early neurogenic state. Here, we demonstrate that the pluripotency regulator Klf4 is sufficient to reprogram the potency of lineage-restricted retinal progenitor cells (RPCs) to generate RGCs in vivo. Transcriptome analysis disclosed that the overexpression of Klf4 induces crucial regulators of RGC competence and specification, including Atoh7 and Eya2. In contrast, loss-of-function studies in mice and zebrafish demonstrated that Klf4 is not essential for generation or differentiation of RGCs during retinogenesis. Nevertheless, induced RGCs (iRGCs) generated upon Klf4 overexpression migrate to the proper layer and project axons aligned with endogenous fascicles that reach the optic nerve head. Notably, iRGCs survive for up to 30 days after in vivo reprogramming. Finally, we demonstrate that Klf4 converts Muller cells into neurons that express markers of RGCs. Altogether, we identified Klf4 as a promising tool to reprogram retinal cells and regenerate RGCs in the mature retina.\n\nSignificance StatementCell fate determination is a key process for development, regeneration and for the design of therapeutic strategies that involve cellular reprogramming. This work shows that the manipulation of a single pluripotency regulator (Klf4) is sufficient to reprogram restricted progenitor cells in vivo. These reprogrammed progenitors reacquire the potency to generate retinal ganglion cells. Ganglion cell degeneration is the leading cause of irreversible blindness; therefore, manipulation of ganglion cell competence is of relevance for human health. Our findings point to Klf4 as a promising tool to develop therapeutic strategies for the replacement of damaged ganglion cells.

developmental biology↗