Eye Development Research Articles

The Relationship Between Systemic Immune Inflammatory Level and Dry Eye in Patients with Sjögren’s Syndrome

Background and objectives: Sjögren Syndrome (SS) is a chronic, systemic, and progressive autoimmune disease in which inflammatory processes play a role. Dry eyes or mouth are present in approximately 95–98% of patients with pSS. This study aimed to evaluate the relationship between SII level and disease activity as well as dry eye involvement in patients with pSS. Materials and methods: A cross-sectional design was employed, and a total of 28 female patients who were aged 18–65 years and were diagnosed with pSS were involved. The Sjögren Syndrome Disease Activity Index (ESSDAI) was calculated in patients. The Schirmer test was applied to all patients. The relationship between SII level and disease activity as well as dry eye involvement in pSS patients was evaluated. Results: In our study, a strong positive correlation was found between the SII value and pSS disease activity, while a negative correlation was found between the Schirmer test, which shows dry eye findings, and eye drying time, and a positive correlation was found with the OSDI. Conclusions: this study reported a correlation between hematological parameters and the development of dry eye in pSS. NLR, PLR, and SII showed statistically significant changes in pSS patients.

The role of erythropoietin in the treatment of ocular disorders: A literature review

Erythropoietin (EPO), traditionally known for its role in hematopoiesis, has garnered increasing attention for its neuroprotective properties, particularly in ocular disorders. This literature review explores the diverse roles of EPO in ocular health and its potential therapeutic applications. EPO’s involvement in ocular organogenesis and maintenance is highlighted, with evidence suggesting its correlation with gestational age and expression alongside crucial regulatory genes during eye development. Pre-clinical studies demonstrate EPO’s efficacy in preserving retinal integrity and mitigating neuronal damage in animal models of glaucoma, methanol optic neuropathy, and optic neuritis. Clinical investigations further support these findings, showing improvements in visual acuity and retinal nerve fiber layer thickness in patients treated with EPO. However, challenges such as optimizing dosage regimens and determining the most effective route of administration remain. Despite these challenges, EPO presents a promising avenue for vision preservation and the management of ocular disorders. Further research, including large-scale clinical trials and mechanistic studies, is warranted to solidify EPO’s role as a safe and effective therapeutic option in ocular diseases.

Homozygosity for a hypomorphic mutation in frizzled class receptor 5 causes syndromic ocular coloboma with microcornea in humans.

Ocular coloboma (OC) is a congenital disorder caused by the incomplete closure of the embryonic ocular fissure. OC can present as a simple anomaly or, in more complex forms, be associated with additional ocular abnormalities. It can occur in isolation or as part of a broader syndrome, exhibiting considerable genetic heterogeneity. Diagnostic yield for OC remains below 30%, indicating the need for further genetic exploration. Mutations in the Wnt receptor FZD5, which is expressed throughout eye development, have been linked to both isolated and complex forms of coloboma. These mutations often result in a dominant-negative effect, where the mutated FZD5 protein disrupts WNT signaling by sequestering WNT ligands. Here, we describe a case of syndromic bilateral OC with additional features such as microcornea, bone developmental anomalies, and mild intellectual disability. Whole exome sequencing revealed a homozygous rare missense variant in FZD5. Consistent with a loss-of-function effect, overexpressing of fzd5 mRNA harboring the missense variant in zebrafish embryos does not influence embryonic development, whereas overexpression of wild-type fzd5 mRNA results in body axis duplications. However, in vitro TOPFlash assays revealed that the missense variant only caused partial loss-of-function, behaving as a hypomorphic mutation. We further showed that the mutant protein still localized to the cell membrane and maintained proper conformation when modeled in silico, suggesting that the impairment lies in signal transduction. This hypothesis is further supported by the fact that the variant affects a highly conserved amino acid known to be crucial for protein-protein interactions.

RNA-Seq Reveals Transcriptome Changes Following Zika Virus Infection in Fetal Brains in c-Flip Knockdown Mice

The FADD-like interleukin-1β converting enzyme (FLICE)-inhibitory protein (c-FLIP) plays a crucial role in various biological processes, including apoptosis and inflammation. However, the complete transcriptional profile altered by the c-FLIP is not fully understood. Furthermore, the impact of the c-FLIP deficiency on the transcriptome during a Zika virus (ZIKV) infection, which induces apoptosis and inflammation in the central nervous system (CNS), has not yet been elucidated. In this study, we compared transcriptome profiles between wild-type (WT) and the c-Flip heterozygous knockout mice (c-Flip+/−) fetal heads at embryonic day 13.5 from control and PBS-infected WT dams mated with c-Flip+/− sires. In the non-infected group, we observed differentially expressed genes (DEGs) mainly involved in embryonic development and neuron development. However, the ZIKV infection significantly altered the transcriptional profile between WT and the c-Flip+/− fetal heads. DEGs in pattern recognition receptor (PRR)-related signaling pathways, such as the RIG-I-like receptor signaling pathway and Toll-like receptor signaling pathway, were enriched. Moreover, the DEGs were also enriched in T cells, indicating that the c-FLIP participates in both innate and adaptive immune responses upon viral infection. Furthermore, our observations indicate that DEGs are associated with sensory organ development and eye development, suggesting a potential role for the c-FLIP in ZIKV-induced organ development defects. Overall, we have provided a comprehensive transcriptional profile for the c-FLIP and its modulation during a ZIKV infection.

A novel GFAP frameshift variant identified in a family with optico-retinal dysplasia and vision impairment.

Gain-of-function variants in GFAP leads to protein aggregation and is the cause of the severe neurodegenerative disorder Alexander Disease (AxD), while loss of GFAP function has been considered benign. Here, we investigated a six-generation family, where multiple individuals presented with gliosis of the optic nerve head and visual impairment. Whole genome sequencing (WGS) revealed a frameshift variant in GFAP (c.928dup, p.(Met310Asnfs*113)) segregating with disease. Analysis of human embryonic tissues revealed strong expression of GFAP in retinal neural progenitors. A zebrafish model verified that c.928dup does not result in extensive GFAP protein aggregation and zebrafish gfap loss-of-function mutants showed vision impairment and retinal dysplasia, characterized by a significant loss of Müller glia cells and photoreceptor cells. Our findings show how different mutational mechanisms can cause diverging phenotypes and reveal a novel function of GFAP in vertebrate eye development.

Deletion upstream of MAB21L2 highlights the importance of evolutionarily conserved non-coding sequences for eye development

Anophthalmia, microphthalmia and coloboma (AMC) comprise a spectrum of developmental eye disorders, accounting for approximately 20% of childhood visual impairment. While non-coding regulatory sequences are increasingly recognised as contributing to disease burden, characterising their impact on gene function and phenotype remains challenging. Furthermore, little is known of the nature and extent of their contribution to AMC phenotypes. We report two families with variants in or near MAB21L2, a gene where genetic variants are known to cause AMC in humans and animal models. The first proband, presenting with microphthalmia and coloboma, has a likely pathogenic missense variant (c.338 G > C; p.[Trp113Ser]), segregating within the family. The second individual, presenting with microphthalmia, carries an ~ 113.5 kb homozygous deletion 19.38 kb upstream of MAB21L2. Modelling of the deletion results in transient small lens and coloboma as well as midbrain anomalies in zebrafish, and microphthalmia and coloboma in Xenopus tropicalis. Using conservation analysis, we identify 15 non-coding conserved elements (CEs) within the deleted region, while ChIP-seq data from mouse embryonic stem cells demonstrates that two of these (CE13 and 14) bind Otx2, a protein with an established role in eye development. Targeted disruption of CE14 in Xenopus tropicalis recapitulates an ocular coloboma phenotype, supporting its role in eye development. Together, our data provides insights into regulatory mechanisms underlying eye development and highlights the importance of non-coding sequences as a source of genetic diagnoses in AMC.

The dual Ras Association (RA) Domains of Drosophila Canoe have differential roles in linking cell junctions to the cytoskeleton during morphogenesis.

During development cells must change shape and move without disrupting dynamic tissue architecture. This requires robust linkage of cell-cell adherens junctions to the force-generating actomyosin cytoskeleton. Drosophila Canoe and mammalian Afadin play key roles. One central task for the field is defining mechanisms by which upstream inputs from Ras-family GTPases regulate Canoe/Afadin. They are unusual in sharing two tandem Ras-association (RA) domains, which, when deleted, virtually eliminate Canoe function. Work in vitro suggested RA1 and RA2 differ in GTPase affinity, but their individual functions in vivo remain unknown. Combining bioinformatic and biochemical approaches, we find that both RA1 and RA2 bind to active Rap1 with similar affinities, and their conserved N-terminal extensions enhance binding. We created Drosophila canoe mutants to test RA1 and RA2 function in vivo. Despite their similar affinities for Rap1, RA1 and RA2 play strikingly different roles. Deleting RA1 virtually eliminates Canoe function, while mutants lacking RA2 are viable and fertile but have defects in junctional reinforcement in embryos and during pupal eye development. These data significantly expand our understanding of regulation of adherens junction:cytoskeletal linkage.

Loss of Cdc42 causes abnormal optic cup morphogenesis and microphthalmia in mouse.

Congenital ocular malformations originate from defective morphogenesis during early eye development and cause 25% of childhood blindness. Formation of the eye is a multi-step, dynamic process; it involves evagination of the optic vesicle, followed by distal and ventral invagination, leading to the formation of a two-layered optic cup with a transient optic fissure. These tissue folding events require extensive changes in cell shape and tissue growth mediated by cytoskeleton mechanics and intercellular adhesion. We hypothesized that the Rho GTPase Cdc42 may be an essential, convergent effector downstream of key regulatory factors required for ocular morphogenesis. CDC42 controls actin remodeling, apicobasal polarity, and junction assembly. Here we identify a novel essential function for Cdc42 during eye morphogenesis in mouse; in Cdc42 mutant eyes expansion of the ventral optic cup is arrested, resulting in microphthalmia and a wide coloboma. Our analyses show that Cdc42 is required for expression of the polarity effector proteins PRKCZ and PARD6, intercellular junction protein tight junction protein 1, β-catenin, actin cytoskeleton F-actin, and contractile protein phospho myosin light chain 2. Expression of RPE fate determinants OTX2 and MITF, and formation of the RPE layer are severely affected in the temporal domain of the proximal optic cup. EdU incorporation is significantly downregulated. In addition, mitotic retinal progenitor cells mis-localized deeper, basal regions, likely contributing to decreased proliferation. We propose that morphogenesis of the ventral optic cup requires Cdc42 function for coordinated optic cup expansion and establishment of subretinal space, tissue tension, and differentiation of the ventral RPE layer.

Targeting Nrf2 signaling in dry eye.

Dry eye, the most common ocular surface disease, can cause ocular surface tissue damage and discomfort symptoms and seriously affect people's quality of life. The etiology of dry eye is diverse, and its pathogenesis is complex. The oxidative stress reaction is considered to be among the important factors in the pathogenesis of dry eye. Therefore, activating the antioxidant system has a potential therapeutic effect on dry eye. Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway is considered the most important antioxidant pathway in the body. The activation of the Nrf2 signaling pathway and its interaction with other pathways are important mechanisms to prevent the occurrence and development of dry eye. This review describes the structure and function of Nrf2, summarizes the changes in the oxidative stress response in dry eye, focuses on the potential mechanism of the Nrf2 signaling pathway in the treatment of dry eye, and, finally, summarizes the drugs that activate the Nrf2 signaling pathway in the treatment of dry eye.

Quantum Dots-caused Retinal Degeneration in Zebrafish Regulated by Ferroptosis and Mitophagy in Retinal Pigment Epithelial Cells through Inhibiting Spliceosome.

Quantum dots (QDs) are widely used, but their health impact on the visual system is little known. This study aims to elucidate the effects and mechanisms of typical metallic QDs on retinas using zebrafish. Comprehensive histology, imaging, and bulk RNA sequencing reveal that InP/ZnS QDs cause retinal degeneration. Furthermore, single-cell RNA-seq reveals a reduction in the number of retinal pigment epithelial cells (RPE) and short-wave cone UV photoreceptor cells (PR(UV)), accompanied by an increase in middle- and long-wave cone red, green, and blue photoreceptor cells [PR(RGB)]. Mechanistically, after endocytosis by RPE, InP/ZnS QDs inhibit the expression of splicing factor prpf8, resulting in gpx4b mRNA unsplicing, which finally decrease glutathione and induce ferroptosis and mitophagy. The decrease of RPE fails to engulf the damaged outer segments of PR, possibly promoting the differentiation of PR(UV) to PR(RGB). Knockout prpf8 or gpx4b with CRISPR/Cas9 system, the retinal damage is also observed. Whereas, overexpression of prpf8 or gpx4b, or supplement of glutathione can rescue the retinal degenerative damage caused by InP/ZnS QDs. In conclusion, this study illustrates the potential health risks of InP/ZnS QDs on eye development and provides valuable insights into the underlying mechanisms of InP/ZnS QDs-caused retinal degeneration.

Knockout of a single Pax6 gene (toy but not ey) leads to compound eye deficiency and small head in honeybees

The compound eyes are crucial to honeybees, playing pivotal roles in color recognition, orientation, localization, and navigation processes. The development of compound eyes is primarily mastered by an evolutionarily conserved transcription factor Pax6. In honeybees, there are two Pax6 homologs: ey and toy. To gain a deeper understanding of their functions, we knock out both homologs using CRISPR/Cas9 technology. Intriguingly, we observe that toy knockout mutants have smaller heads without compound eyes and exhibit brain atrophy, while ey knockout mutants develop normal compound eyes, most of which die before/during their metamorphosis from pupa to adult. By comparing the head transcriptomes of four stages (larva, prepupa, pupa, and adult) in toy-knockout mutants versus normal controls, we identify significantly perturbed genes related to DNA binding transcription factors, neuron differentiation, and insect visual primordium development. Additionally, we find the interaction network of toy in honeybees differs obviously from that of D. melanogaster. Our findings suggest the two Pax6 genes serve distinct functions in honeybees and toy takes over the central function of ey in master-regulating the development of honeybee compound eyes. This adds new evidence for breaking the simplified view that some of conservative developmental toolkit genes function as all-or-nothing master regulators.

Inspiration from Visual Ecology for Advancing Multifunctional Robotic Vision Systems: Bio-inspired Electronic Eyes and Neuromorphic Image Sensors.

In robotics, particularly for autonomous navigation and human-robot collaboration, the significance of unconventional imaging techniques and efficient data processing capabilities is paramount. The unstructured environments encountered by robots, coupled with complex missions assigned to them, present numerous challenges necessitating diverse visual functionalities, and consequently, the development of multifunctional robotic vision systems has become indispensable. Meanwhile, rich diversity inherent in animal vision systems, honed over evolutionary epochs to meet their survival demands across varied habitats, serves as a profound source of inspirations. Here, recent advancements in multifunctional robotic vision systems drawing inspiration from natural ocular structures and their visual perception mechanisms are delineated. First, unique imaging functionalities of natural eyes across terrestrial, aerial, and aquatic habitats and visual signal processing mechanism of humans are explored. Then, designs and functionalities of bio-inspired electronic eyes are explored, engineered to mimic key components and underlying optical principles of natural eyes. Furthermore, neuromorphic image sensors are discussed, emulating functional properties of synapses, neurons, and retinas and thereby enhancing accuracy and efficiency of robotic vision tasks. Next, integration examples of electronic eyes with mobile robotic/biological systems are introduced. Finally, a forward-looking outlook on the development of bio-inspired electronic eyes and neuromorphic image sensors is provided.

Genome-wide identification and expression profiling of the Wnt gene family in three abalone species.

The Wnt gene family plays pivotal roles in a variety of biological processes including cell proliferation and differentiation, apoptosis, and embryonic development. Identifying the Wnt signaling pathway in abalone could provide a basis for elucidating growth and development mechanisms and improving quality. To identify the number, protein physicochemical properties, gene structure, phylogenetic analysis, and expression profiles of the Wnt gene family in abalone. A comprehensive genome-wide analysis was performed to identify the Wnt gene family in the genomes of three abalone species (Haliotis discus hannai, H. rubra, and H. rufescens). Ten single-copy Wnt genes were identified in each abalone species, suggesting that the number of Wnt genes was relatively conserved in Haliotis. Eight Wnt gene subfamilies, including Wnt1, Wnt4, Wnt5, Wnt6, Wnt7, Wnt10, Wnt16, and WntA, are present in all three species. Each abalone species contains two species-specific subfamilies (Wnt9 and Wnt11 in H. discus hannai, Wnt2 and Wnt11 in H. rubra, and Wnt2 and Wnt9 in H. rufescens), reflecting polymorphisms of the Wnt genes in Haliotis. Interestingly, gastropods are characterised by the loss of Wnt8, suggesting a potential evolutionary specificity in gastropods. As expected, Wnt3 is absent in all protostomes, including the abalone. In addition, spatio-temporal expression profiling revealed differential expression levels of the Wnt genes at different developmental stages and in different tissues of H. discus hannai. HdWnt5 and HdWntA might participate in several processes during larval development stages, including germ layer formation and body axis elongation. HdWnt5 may be involved in eye and tentacle development. HdWnt10 may be related to muscle development, and HdWnt6 may be involved in shell formation in abalone. To our knowledge, the results of this study, which is the first genome-wide investigation of the Wnt gene family in abalone, lay the groundwork for future research on the evolution and function of the Wnt gene family in Gastropoda.

A Deep Feature Driven Expert System to Estimate the Postmortem Interval From Corneal Opacity Development

ABSTRACTPostmortem interval (PMI) estimation remains an unresolved challenge in forensic science, necessitating practical, reliable and more accurate tools. This study aimed to develop a quantitative PMI estimation tool that effectively meets these needs. Focusing on the postmortem opacity development of the eye as a key marker for determining time since death, we propose an artificial intelligence‐based clinical PMI prediction system utilising computer vision, deep learning and machine learning methods. The AlexNet algorithm was utilised to extract deep features from the postmortem eye images. Extracted features were then processed by machine learning algorithms. For feature selection, Lasso and Relief techniques were employed, while SVM and KNN were applied for classifications. The results were validated using the leave‐one‐subject‐out method. The system was tested across different postmortem ranges, providing multi‐label predictions. The performance was evaluated using various metrics. The deep features exhibited effective performance in grading postmortem opacity development, achieving state‐of‐the‐art results. The accuracy scores were 0.96 and 0.97 for 3‐h intervals (i.e., 5‐class) and 5‐h intervals (i.e., 3‐class) experiments, respectively. The experimental results indicate that the proposed system represents a promising tool for PMI estimation.

New insights into transcriptional and metabolic differences between pregnant males and embryos in seahorses

Seahorses exhibit a unique reproduction mode of male pregnancy. Successful gestation plays a crucial role in the seahorse reproduction process and the aquaculture industry. However, the substantial paternal-embryo differences in seahorses remain largely unexplored. In the present study, transcriptomic and metabolic differences between pregnant males and embryos during gestation were explored to investigate the roles of key genes and metabolites in pregnant males and embryos in seahorses. Higher levels of essential amino acids and polyunsaturated fatty acids in embryos compared to fathers may indicate their vital role in embryonic development. The high expression of immune-related genes (CCLs and CCRs) and downregulation of antioxidants in fathers may provide immune protection and reduce the immunological rejection of embryos during gestation. The transcript-metabolite correlation network during pregnancy further indicated the role of key genes and metabolites during embryonic eye (N-acetyl-L-histidine, PAX6, and FZT4) and tail (WNT5 and WNT8) development. The findings of the present study not only provide valuable data on differences between pregnant males and embryos in seahorse, but also lay foundation for future research on seahorse aquaculture.

A mechanistic study on the interaction effects between legacy and pollutants of emerging concern: A case study with B[a]P and diclofenac

To study the intricate toxicological mechanisms triggered by exposure to mixed pollutants, we exposed zebrafish embryos to legacy and emerging pollutants through binary mixtures of benzo[a]pyrene (B[a]P) and diclofenac (DFC). The combination of next-generation transcriptomics and toxicopathology disclosed instances where exposure to mixtures did not attain the expected sum of acute effects of individual toxicants, indicating potential antagonism. Despite overall higher mortality in DFC treatments, the same antagonistic trend was noted in genotoxicity and molecular pathways related to RNA turnover, cell proliferation, apoptosis and cell-cycle control. The formation of oedemas in the heart cavity and yolk sac can be an adverse outcome (AO) resulting from exposure to DFC isolated or combined, whose potential key events (KEs) may involve cell cycle arrest and apoptosis via p53 and MAPK pathways. From the findings it can be hypothesised that, rather than genotoxicity, the molecular initiating event (MIE) maybe inflammation triggered by oxidative stress. Nonetheless, the exact role of ROS in the process needs further clarification. Impaired eye function by action of DFC and B[a]P combined may be another AO, in the case caused by ocular degeneration following the suppression of biologic processes and molecular functions involved in eye development and its functionalities, possibly linked to hindered regulation of the expression of hsf4 and cryaa. Altogether, toxicopathology suggests predominance of antagonistic effects, but its integration with mechanism suggests that interactions between DFC and B[a]P in environmentally-relevant concentrations that may lead to hindrance of key functions such as the control of inflammation and cell cycle. These outcomes suggest potentially severe implications for health and survival, in case of prolonged chronic exposure to combined toxicants.

Fetal eye ultrasound: Normal anatomy, abnormal findings, and clinical impact.

Until now, ultrasound examination of the fetal eyes has not played an important role in prenatal diagnosis. National and international guidelines are generally confined to documentation of the presence of the orbits and the lenses. However, in recent years, with the advent of high-resolution ultrasound technology and increasing knowledge of prenatal medicine and genetics, careful examination of the fetal eye has enabled the detection of many ocular malformations before birth. This article provides an overview of the anatomy related to the development of the fetal eye and covers the following conditions: hypertelorism, hypotelorism, exophthalmos, microphthalmos, coloboma, cataract, persistent hyperplastic primary vitreous, retinal detachment, dacryocystocele, and septooptic dysplasia, etc. It is designed to illustrate the spectrum of ocular malformations and their appearance on prenatal ultrasound and to discuss their clinical impact and association with various syndromes.

Enhancing lutein stability and bioaccessibility with high internal phase emulsions stabilized by octenylsuccinylated starch

AbstractLutein possesses antioxidant properties and is a main component of the macular pigment, vital for infant eye and brain development. However, its use is constrained by its poor aqueous solubility and low stability. High internal phase emulsions (HIPEs) are valued in food development for encapsulating and protecting hydrophobic nutraceuticals. The objective of this study is to improve lutein's stability and bioaccessibility using HIPEs stabilized by biopolymer octenylsuccinylated starch (OSS). Three types of commercial OSS, including CAPSUL TA (CTA), HI‐CAP 100 (HC), and Purity Gum 2000, were tested for their emulsification properties in forming lutein HIPEs. Lutein HIPEs stabilized by 15%–25% CTA and 15%–30% HC had no phase separation and were selected for subsequent testing. After 21 days of storage at room temperature, lutein HIPEs showed higher lutein retention compared to free lutein. Lutein HIPEs stabilized with higher emulsifier concentrations (25% CTA and 30% HC) exhibited greater droplet diameter stability than those with lower concentrations. Additionally, lutein HIPEs significantly enhanced lutein retention under UV exposure and thermal stress. The in vitro bioaccessibility of lutein was highest in the HIPE stabilized by 20% CTA, reaching 54.36%. In conclusion, lutein HIPEs stabilized by 20% CTA demonstrated superior lutein stability and bioaccessibility, showing significant potential as an effective lutein delivery system.

The Microphthalmia-Associated Transcription Factor (MITF) and Its Role in the Structure and Function of the Eye.

The microphthalmia-associated transcription factor (Mitf) has been found to play an important role in eye development, structure, and function. The Mitf gene is responsible for controlling cellular processes in a range of cell types, contributing to multiple eye development processes. In this review, we survey what is now known about the impact of Mitf on eye structure and function in retinal disorders. Several mutations in the human and mouse Mitf gene are now known, and the effects of these on eye phenotype are addressed. We discuss the importance of Mitf in regulating ion transport across the retinal pigment epithelium (RPE) and the vasculature of the eye. The literature was searched using the PubMed, Scopus, and Google Scholar databases. Fundus and Optical Coherence Tomography (OCT) images from mice were obtained with a Micron IV rodent imaging system. Defects in neural-crest-derived melanocytes resulting from any Mitf mutations lead to hypopigmentation in the eye, coat, and inner functioning of the animals. While many Mitf mutations target RPE cells in the eye, fewer impact osteoclasts at the same time. Some of the mutations in mice lead to microphthalmia, and ultimately vision loss, while other mice show a normal eye size; however, the latter, in some cases, show hypopigmentation in the fundus and the choroid is depigmented and thickened, and in rare cases Mitf mutations lead to progressive retinal degeneration. The Mitf gene has an impact on the structure and function of the retina and its vasculature, the RPE, and the choroid in the adult eye.

Single-cell sequencing suggests a conserved function of Hedgehog-signalling in spider eye development

BackgroundSpiders evolved different types of eyes, a pair of primary eyes that are usually forward pointing, and three pairs of secondary eyes that are typically situated more posterior and lateral on the spider’s head. The best understanding of arthropod eye development comes from the vinegar fly Drosophila melanogaster, the main arthropod model organism, that also evolved different types of eyes, the larval eyes and the ocelli and compound eyes of the imago. The gene regulatory networks that underlie eye development in this species are well investigated revealing a conserved core network, but also show several differences between the different types of eyes. Recent candidate gene approaches identified a number of conserved genes in arthropod eye development, but also revealed crucial differences including the apparent lack of some key factors in some groups of arthropods, including spiders.ResultsHere, we re-analysed our published scRNA sequencing data and found potential key regulators of spider eye development that were previously overlooked. Unlike earlier research on this topic, our new data suggest that Hedgehog (Hh)-signalling is involved in eye development in the spider Parasteatoda tepidariorum. By investigating embryonic gene expression in representatives of all main groups of spiders, we demonstrate that this involvement is conserved in spiders. Additionally, we identified genes that are expressed in the developing eyes of spiders, but that have not been studied in this context before.ConclusionOur data show that single-cell sequencing represents a powerful method to gain deeper insight into gene regulatory networks that underlie the development of lineage-specific organs such as the derived set of eyes in spiders. Overall, we gained deeper insight into spider eye development, as well as the evolution of arthropod visual system formation.