Protocadherin 19 regulates axon guidance in the developing Xenopus retinotectal pathway.

Protocadherin 19 (Pcdh19) is a homophilic cell adhesion molecule and is involved in a variety of neuronal functions. Here, we tested whether Pcdh19 has a regulatory role in axon guidance using the developing Xenopus retinotectal system. We performed targeted microinjections of a translation blocking antisense morpholino oligonucleotide to knock down the expression of Pcdh19 selectively in the central nervous system. Knocking down Pcdh19 expression resulted in navigational errors of retinal ganglion cell (RGC) axons specifically at the optic chiasm. Instead of projecting to the contralateral optic tectum, RGC axons in the Pcdh19-depleted embryo misprojected ipsilaterally. Although incorrectly delivered into the ipsilateral brain hemisphere, these axons correctly reached the optic tectum. These data suggest that Pcdh19 has a critical role in preventing mixing of RGC axons originating from the opposite eyes at the optic chiasm, highlighting the importance of cell adhesion in bundling of RGC axons.

Single cell dual-omic atlas of the human developing retina.

The development of the retina is under tight temporal and spatial control. To gain insights into the molecular basis of this process, we generate a single-nuclei dual-omic atlas of the human developing retina with approximately 220,000 nuclei from 14 human embryos and fetuses aged between 8 and 23-weeks post-conception with matched macular and peripheral tissues. This atlas captures all major cell classes in the retina, along with a large proportion of progenitors and cell-type-specific precursors. Cell trajectory analysis reveals a transition from continuous progression in early progenitors to a hierarchical development during the later stages of cell type specification. Both known and unrecorded candidate transcription factors, along with gene regulatory networks that drive the transitions of various cell fates, are identified. Comparisons between the macular and peripheral retinae indicate a largely consistent yet distinct developmental pattern. This atlas offers unparalleled resolution into the transcriptional and chromatin accessibility landscapes during development, providing an invaluable resource for deeper insights into retinal development and associated diseases.

Temporal landscape and translational regulation of A-to-I RNA editing in mouse retina development.

BACKGROUND: The significance of A-to-I RNA editing in nervous system development is widely recognized; however, its influence on retina development remains to be thoroughly understood. RESULTS: In this study, we performed RNA sequencing and ribosome profiling experiments on developing mouse retinas to characterize the temporal landscape of A-to-I editing. Our findings revealed temporal changes in A-to-I editing, with distinct editing patterns observed across different developmental stages. Further analysis showed the interplay between A-to-I editing and alternative splicing, with A-to-I editing influencing splicing efficiency and the quantity of splicing events. A-to-I editing held the potential to enhance translation diversity, but this came at the expense of reduced translational efficiency. When coupled with splicing, it could produce a coordinated effect on gene translation. CONCLUSIONS: Overall, this study presents a temporally resolved atlas of A-to-I editing, connecting its changes with the impact on alternative splicing and gene translation in retina development.

Histological and scanning electron microscope observations on the developing retina of the cuttlefish (Sepia officinalis Linnaeus, 1758).

In this work we present a detailed study of the major events during retinal histogenesis of the cuttlefish Sepia officinalis from early embryos to newly hatched animals and juveniles. For this purpose, we carried out morphometric and histological analyses using light and scanning electron microscopy. From St19, the first embryonic stage analysed, to St23/24 the embryonic retina is composed of a pseudostratified epithelium showing abundant mitotic figures in the more internal surface. At St24 the first photoreceptor nuclei appear in the presumptive inner segment layer, while an incipient layer of apical processes of the future rhabdomeric layer become visible at St25. From this stage onwards, both the rhabdomeric layer and the inner segment layer increase in size until postnatal ages. In contrast, the width of the supporting cell layer progressively decreases from St25/26 until postnatal ages. S. officinalis embryos hatched in a morphologically advanced state, showing a differentiated retina even in the last stages of the embryonic period. However, features of immaturity are still observable in the retinal tissue during the first postnatal weeks of life, such as the existence of mitotic figures in the apical region of the supporting cell layer and migrating nuclei of differentiating photoreceptors crossing the basal membrane to reach their final location in the inner segment layer. Therefore, postnatal retinal neurogenesis is present in juvenile specimens of S. officinalis.

Non-canonical Wnt pathway expression in the developing mouse and human retina.

The non-canonical Wnt pathway is an evolutionarily conserved pathway essential for tissue patterning and development across species and tissues. In mammals, this pathway plays a role in neuronal migration, dendritogenesis, axon growth, and synapse formation. However, its role in development and synaptogenesis of the human retina remains less established. In order to address this knowledge gap, we analyzed publicly available single-cell RNA sequencing (scRNAseq) datasets for mouse retina, human retina, and human retinal organoids over multiple developmental time points during outer retinal maturation. We identified ligands, receptors, and mediator genes with a putative role in retinal development, including those with novel or species-specific expression, and validated this expression using fluorescence in situ hybridization (FISH). By quantifying outer nuclear layer (ONL) versus inner nuclear layer (INL) expression, we provide evidence for the differential expression of certain non-canonical Wnt signaling components in the developing mouse and human retina during outer plexiform layer (OPL) development. Importantly, we identified distinct expression patterns of mouse and human FZD3 and WNT10A, as well as previously undescribed expression, such as for mouse Wnt2b in Chat+ starburst amacrine cells. Human retinal organoids largely recapitulated the human non-canonical Wnt pathway expression. Together, this work provides the basis for further study of non-canonical Wnt signaling in mouse and human retinal development and synaptogenesis.

Characterization of the development of the high-acuity area of the chick retina.

The fovea is a small region within the central retina that is responsible for our high acuity daylight vision. Chickens also have a high acuity area (HAA), and are one of the few species that enables studies of the mechanisms of HAA development, due to accessible embryonic tissue and methods to readily perturb gene expression. To enable such studies, we characterized the development of the chick HAA using single molecule fluorescent in situ hybridization (smFISH), along with more classical methods. We found that Fgf8 provides a molecular marker for the HAA throughout development and into adult stages, allowing studies of the cellular composition of this area over time. The radial dimension of the ganglion cell layer (GCL) was seen to be the greatest at the HAA throughout development, beginning during the period of neurogenesis, suggesting that genesis, rather than cell death, creates a higher level of retinal ganglion cells (RGCs) in this area. In contrast, the HAA acquired its characteristic high density of cone photoreceptors post-hatching, which is well after the period of neurogenesis. We also confirmed that rod photoreceptors are not present in the HAA. Analyses of cell death in the developing photoreceptor layer, where rods would reside, did not show apoptotic cells, suggesting that lack of genesis, rather than death, created the "rod-free zone" (RFZ). Quantification of each cone photoreceptor subtype showed an ordered mosaic of most cone subtypes. The changes in cellular densities and cell subtypes between the developing and mature HAA provide some answers to the overarching strategy used by the retina to create this area and provide a framework for future studies of the mechanisms underlying its formation.

A single-cell time-lapse of mouse prenatal development from gastrula to birth.

The house mouse (Mus musculus) is an exceptional model system, combining genetic tractability with close evolutionary affinity to humans1,2. Mouse gestation lasts only 3 weeks, during which the genome orchestrates the astonishing transformation of a single-cell zygote into a free-living pup composed of more than 500 million cells. Here, to establish a global framework for exploring mammalian development, we applied optimized single-cell combinatorial indexing3 to profile the transcriptional states of 12.4 million nuclei from 83 embryos, precisely staged at 2- to 6-hour intervals spanning late gastrulation (embryonic day 8) to birth (postnatal day 0). From these data, we annotate hundreds of cell types and explore the ontogenesis of the posterior embryo during somitogenesis and of kidney, mesenchyme, retina and early neurons. We leverage the temporal resolution and sampling depth of these whole-embryo snapshots, together with published data4-8 from earlier timepoints, to construct a rooted tree of cell-type relationships that spans the entirety of prenatal development, from zygote to birth. Throughout this tree, we systematically nominate genes encoding transcription factors and other proteins as candidate drivers of the in vivo differentiation of hundreds of cell types. Remarkably, the most marked temporal shifts in cell states are observed within one hour of birth and presumably underlie the massive physiological adaptations that must accompany the successful transition of a mammalian fetus to life outside the womb.

Requirement of a novel gene, drish, in the zebrafish retinal ganglion cell and primary motor axon development.

BACKGROUND: During neurogenesis, growing axons must navigate through the complex extracellular environment and make correct synaptic connections for the proper functioning of neural circuits. The mechanisms underlying the formation of functional neural networks are still only partially understood. RESULTS: Here we analyzed the role of a novel gene si:ch73-364h19.1/drish in the neural and vascular development of zebrafish embryos. We show that drish mRNA is expressed broadly and dynamically in multiple cell types including neural, glial, retinal progenitor and vascular endothelial cells throughout the early stages of embryonic development. To study Drish function during embryogenesis, we generated drish genetic mutant using CRISPR/Cas9 genome editing. drish loss-of-function mutant larvae displayed defects in early retinal ganglion cell, optic nerve and the retinal inner nuclear layer formation, as well as ectopic motor axon branching. In addition, drish mutant adults exhibited deficient retinal outer nuclear layer and showed defective light response and locomotory behavior. However, vascular patterning and blood circulation were not significantly affected. CONCLUSIONS: Together, these data demonstrate important roles of zebrafish drish in the retinal ganglion cell, optic nerve and interneuron development and in spinal motor axon branching.

Spatio-temporal expression profile of Mettl3/Mettl14 during mouse retina development / Perfil de expresión espacio-temporal de Mettl3 / Mettl14 durante el desarrollo de la retina del ratón

SUMMARY: The Mettl3/Mettl14 methyltransferase complex installs the most ubiquitous internal mRNA modification- N6-methyladenosine (m6A). The vertebrate retina development is a multi-step process that requires fine-tuning of multiple cellular events, but very little is known about the potential function of Mettl3 and Mettl14 in this process. In this study, we demonstrated the spatio-temporal expression of Mettl3 and Mettl14 during retina development in mouse by quantitative PCR and immunofluorescence staining. We found that these two components of methyltransferase complex could be detected from the beginning of retina development; and the expression of Mettl3 and Mettl14 were gradually restricted to inner nuclear layer (INL) and ganglion cell layer (GCL); Double labeling showed that Mettl3 and Mettl14 had similar expression patterns in mature retinal INL and GCL. Overall, our spatio-temporal expression data provided the foundation for future research on the function of m6A modification in the retina development.

RESUMEN: El complejo Mettl3 / Mettl14 metiltransferasa establece la modificación interna más significativa de ARNm: N6- metiladenosina (m6A). El desarrollo de la retina de los vertebrados es un proceso de varios pasos que requiere múltiples eventos celulares; existe muy poca información sobre la función potencial de Mettl3 y Mettl14 en este proceso. En este estudio, demostramos la expresión espacio-temporal de Mettl3 y Mettl14 durante el desarrollo de la retina en ratón mediante PCR cuantitativa y tinción de inmunofluorescencia. Descubrimos que estos dos componentes del complejo de metiltransferasa podían ser detectados desde el comienzo del desarrollo de la retina; la expresión de Mettl3 y Mettl14 se restringió gradualmente a la capa nuclear interna (INL) y la capa de células ganglionares (GCL); se observó que Mettl3 y Mettl14 tenían patrones de expresión similares en INL y GCL retinianos maduros. En general, nuestros datos de expresión espacio-temporal proporcionan información para futuras investigaciones sobre la función de la modificación de m6A en el desarrollo de la retina.

Apoptosis durante el desarrollo embrionario de la retina de tortuga (Trachemys scripta elegans) / Apoptosis in turtle embryonic retina (Trachemys scripta elegans)

La apoptosis o muerte celular programada es un proceso que ocurre durante el desarrollo del sistema nervioso. El objetivo de este estudio fue observar los patrones de apoptosis que se producen durante el desarrollo embrionario de la retina, desde el estadio S16 al momento del nacimiento, mediante miscoscopía óptica y electrónica. Se utilizaron retinas de embriones de tortuga. Nuestros datos muestran que los primeros signos de apoptosis comienzan en el estadio S16, en la capa nuclear interna y alcanzan su máxima densidad tanto en la capa nuclear interna como en la capa de células ganglionares en S20, para extinguirse, prácticamente, en el momento del nacimiento. Por otra parte, la apoptosis sigue un gradiente centro-periferia.

Apoptosis or programmed cell death is a process that occurs during development of the nervous system. The aim of this study was to observe the patterns of apoptosis that occur during embryonic development of the retina from the stage S16 at birth, by light and electron miscoscopia. Turtle embryonic retinas were used for the study. Our data show that the first signs of apoptosis begins at stage S16 in the inner nuclear layer and reaches maximum density both in the inner nuclear layer and the ganglion cell layer in S20 until they practically disappear at the time of birth. Furthermore, apoptosis follows a gradient center-periphery.

Neurochemical phenotype and birthdating of specific cell populations in the chick retina

The chick embryo is one of the most traditional models in developing neuroscience and its visual system has been one of the most exhaustively studied. The retina has been used as a model for studying the development of the nervous system. Here, we describe the morphological features that characterize each stage of the retina development and studies of the neurogenesis period of some specific neurochemical subpopulations of retinal cells by using a combination of immunohistochemistry and autoradiography of tritiated-thymidine. It could be concluded that the proliferation period of dopaminergic, GABAergic, cholinoceptive and GABAceptive cells does not follow a common rule of the neurogenesis. In addition, some specific neurochemical cell groups can have a restrict proliferation period when compared to the total cell population.

O embrião de galinha é um dos mais tradicionais modelosde estudos da neurociência do desenvolvimento e seu sistema visual tem sido um dos mais exaustivamente estudado. Aretina tem sido utilizada como modelo para estudar o desenvolvimento do sistema nervoso. Aqui, nós descrevemos as características morfológicas que caracterizam cada estádio da retina em desenvolvimento e os estudos do período de neurogênese de algumas subpopulações de células neuroquímicamente específicas da retina usando uma combinação de imunohistoquímica e autoradiografia de timidina-tritiada. Conclui-se que o período de proliferação das células dopaminérgicas, GABAérgicas, colinoceptivas e GABAceptivas não segue uma regra comum. Além disso, alguns grupos celulares neuroquimicamente distintos podem ter um período de proliferaçãomais restrito quando comparado ao da população total destas células.

Disfuncionalidad neuronal y psicomotora como resultado del retraso del tratamiento de la ambliopía / Neuronal and psychomotor malfunction secondary to delayed amblyopia treatment

BACKGROUND: A review of neuronal and psychomotor alterations related to delay of amblyopia treatment was carried out. METHODS: We reviewed various studies to explain the anomalies of visual cortex because of the prevalence of anomalous stimulus in patients with amblyopia. RESULTS: Visual pathways are developed embryologically. The newborn has ocular dominance columns ready to be stimulated, but visual alterations present at this time will generate neuronal changes in visual cortex. CONCLUSIONS: Delay of amblyopia treatment with anomalous visual stimulus will provoke organic changes in visual cortex, inducing alterations of brain functions depending on binocularity. Memory and learning have also been related to this condition.

Neuropatía óptica inducida por exposición prenatal a drogas o alcohol / Optic neuropathy induced by prenatal drug or alcohol exposure

Objetivo: Nos proponemos analizar los mecanismos celulares y moleculares implicados en el desarrollo de la retina y el nervio óptico, y las consecuencias de un consumo abusivo de metanfetamina (MA) o alcohol (EtOH) durante la gestación sobre el sistema visual en desarrollo. Material y métodos: Ratas Wistar fueron expuestas a MA o EtOH durante la gestación y lactancia para obtener su descendencia. Los globos oculares y nervios ópticos de neonatos (días 7, 14, 21 postnatales) fueron procesados para técnicas morfológicas, morfométricas y Western Blot, utilizando anticuerpos frente a la proteína fibrilar ácida de la glía (GFAP) y proteína básica de la mielina (MBP) y proteína de los neurofilamentos (NFP). Resultados: Observamos diferencias estadísticamente significativas entre el grupo expuesto a MA y expuesto a EtOH frente a los controles. El tamaño de la sección transversal del nervio óptico fue inferior en relación a la exposición a drogas o alcohol. La expresión de GFAP y MBP está alterada en los animales expuestos a drogas o alcohol, respecto a los controles. Conclusiones: La exposición prenatal a psicoestimulantes o alcohol altera el desarrollo de la retina y nervio óptico

Purpose: The main aim of this work was to analyse the cellular and molecular mechanisms involved in retinal and optic nerve development, and the consequences of methamphetamine "ice" (MA) or alcohol (EtOH) abuse during pregnancy on the developing visual system. Material and methods: Wistar rats were exposed to MA or EtOH during gestation and lactation and their offspring studied. Control isocaloric rats were maintained in parallel. The eyes and optic nerves from pups (at 7, 14 and 21 postnatal days) were processed using morphologic, morphometric and western blot approaches using antibodies against glial fibrillary acidic protein (GFAP), myelin basic protein (MBP) and neurofilament protein (NFP). Results: Statistically significant differences were observed between the methamphetamine-exposed and the alcohol-exposed rats, as compared to the controls. The optic nerve cross-sectional area was smaller in the drug or alcohol-exposed animals. The expression of developmental protein markers (GFAP and MBP) in the retina and optic nerve displayed striking alterations related to drug or alcohol abuse during gestation and lactation. Conclusions: Psychostimulant and alcohol exposure alters the development of the retina and optic nerve

Immunoreactivity of Constitutive and Inducible Heat Shock Protein 70 in Human Fetal Retina

The purpose of this study was to measure the level of expression of the inducible heat shock protein70 (Hsp70), the constitutive heat shock protein70 (Hsc70) in the outer nuclear layer and the photoreceptors in the human fetal retina. Fetal eyeballs were selected from fetal autopsy specimens of 12 and 17 to 40 week old fetuses, with no history of congenital anomalies. The retinas had differentiated from neuroblastic cells, into matured sensory retinas, from a gestational age (GA) from 12 to 36 weeks. The Hsp70 and Hsc70 were prominently expressed in the nuclear layers. The Hsc70 was expressed at all GAs and the Hsp70 was expressed from 20 to 33 weeks GA. This period is in accordance with the maturation of the sensory retina. The expression of heat shock protein may be regulated by the development of the fetus, and play an important role in the ocular development.

Retinal glial cells in alcohol-treated chick embryos / Células gliales retinianas en embriones de pollo tratados con alcohol

In the present study we used electron microscope techniques to analyze the effect of ethanol on the inner layers of chick embryo retinas. We show that these layers are very strongly affected by alcohol during development, with a delay in differentiation, a considerable degree of destructuring of the inner layers, accompanied by a loss of the inner prolongations of Müller cells, and the glial cells' location at the retinal inner layers (inner plexiform layer and optic nerve fiber layer) replacing these degenerated inner prolongations. We performed a count and statistical study of the axonal loss from the optic nerve fiber layer of the retinas of ethanol-treated embryos and observed a loss of total axons, mostly of myelinic axons (AU)

En este estudio, empleamos técnicas de microscopía electrónica para analizar el efecto del etanol sobre las capas internas de las retinas de embriones de pollo. Demostramos que estas capas son fuertemente afectadas por el alcohol durante el desarrollo, con un retraso en la diferenciación, una desestructuración considerable de las capas internas, acompañada de una pérdida de las prolongaciones internas de las células de Müller y la localización de las células gliales en las capas internas de la retina (capa plexiforme interna y capa de fibras del nervio óptico) reemplazando a estas prolongaciones internas degeneradas. Llevamos a cabo un conteo y un estudio estadístico de la pérdida de axones de la capa de fibras del nervio óptico de las retinas de los embriones tratados con alcohol y observamos una pérdida de axones totales, principalmente de axones mielínicos (AU)

Inhibition of carbachol-induced inositol phosphate accumulation in the embryonic retina promoted by kainate and veratridine

In the present study, we report that low concentrations of the glutamate ionotropic agonist kainate decreased the turnover of [3H]-phosphoinositides ([3H]-InsPs) induced by muscarinic receptors in the chick embryonic retina. When 100 muM carbachol was used, the estimated IC50 value for kainate was 0.2 muM and the maximal inhibition of ~50 percent was obtained with 1 muM or higher concentrations of the glutamatergic agonist. Our data also show that veratridine, a neurotoxin that increases the permeability of voltage-sensitive sodium channels, had no effect on [3H]-InsPs levels of the embryonic retina. However, 50 muM veratridine, but not 50 mM KCl, inhibited ~65 percent of the retinal response to carbachol. While carbachol increased [3H]-InsPs levels from 241.2 + 38.0 to 2044.5 + 299.9 cpm/mg protein, retinal response decreased to 861.6 + 113.9 cpm/mg protein when tissues were incubated with carbachol plus veratridine. These results suggest that the accumulation of phosphoinositides induced by activation of muscarinic receptors can be inhibited by the influx of Na+ ions triggered by activation of kainate receptors or opening of voltage-sensitive sodium channels in the chick embryonic retina.

Doenças do corpo vítreo, retina e uveíte / Vitreous, retina and uveites

Este capítulo trata de problemas do corpo vítreo, problemas da retina e de uveítes, iniciando com noçöes de Embriologia e com a descriçäo do fundo de olho normal.

A Histochemical Study of Cholinesterase Activity in Rabbit's Retinae

In the present study the specific and nonspecific cholinesterase activities of the rabbit's retinae in the fetus, the neonatal, the light-isolated, and the reopened group, which consisted of 65 healthy young rabbits, weighing about 300 to 500 gm, 33 rabbit's fetuses, and neonatal rabbits, were histochemically ovserved by means of the cholinesterase method recommended by Gerebtzoff (1953) and the embedding and sectioning method pesented by Koelle and Friedenwald (1950). Cholinesterase activity of the retinae in the 15 days fetuses was not present but began to develop in the 20 days fetuses. In the 1 week group after suturing the eyelids, the most remarkable activity of specific and nonspecific cholinesterase was observed in the posterior polar area. The nearer to the peripheral area of the retina the weaker the enzymetic activities became. In the 2 weeks group after suturing eyelids, the enzymatic activity was reduced. In the 4, and 8weeks groups after suturing the eyelides, the enzymatic activities were remarkably reduced. In the l4 days after reopening eyelide, which group has previously been kept under the condition of light isolation for 4 weeks, enzymatic activities were fairly recovered and compared with the normal control group. Consequently it is histochemically deduced that the gradual change of specific cholinesterase activities in the rabbit's retinae was closely related to the visual function.