Early Eye Research Articles

The graded predictive pre-activation in Chinese sentence reading: evidence from eye movements.

Previous research has revealed that graded pre-activation rather than specific lexical prediction is more likely to be the mechanism for the word predictability effect in English. However, whether graded pre-activation underlies the predictability effect in Chinese reading is unknown. Accordingly, the present study tested the generality of the graded pre-activation account in Chinese reading. We manipulated the contextual constraint of sentences and the predictability of target words as independent variables. Readers' eye movement behaviors were recorded via an eye tracker. We examined whether processing an unpredictable word in a solid constraining context incurs a prediction error cost when this unpredictable word has a predictable alternative. The results showed no cues of prediction error cost on the early eye movement measures, supported by the Bayes Factor analyses. The current research indicates that graded predictive pre-activation underlies the predictability effect in Chinese reading.

Generation of iPSC-derived human forebrain organoids assembling bilateral eye primordia.

Induced pluripotent stem cell-derived brain organoids enable the developmental complexities of the human brain to be deconstructed. During embryogenesis, optic vesicles (OVs), the eye primordium attached to the forebrain, develop from diencephalon. However, most 3D culturing methods generate either brain or retinal organoids individually. Here we describe a protocol to generate organoids with both forebrain entities, which we call OV-containing brain organoids (OVB organoids). In this protocol, we first induce neural differentiation (days 0-5) and collect neurospheres, which we culture in a neurosphere medium to initiate their patterning and further self-assembly (days 5-10). Then, upon transfer to spinner flasks containing OVB medium (days 10-30), neurospheres develop into forebrain organoids with one or two pigmented dots restricted to one pole, displaying forebrain entities of ventral and dorsal cortical progenitors and preoptic areas. Further long-term culture results in photosensitive OVB organoids constituting complementary cell types of OVs, including primitive corneal epithelial and lens-like cells, retinal pigment epithelia, retinal progenitor cells, axon-like projections and electrically active neuronal networks. OVB organoids provide a system to help dissect interorgan interactions between the OVs as sensory organs and the brain as a processing unit, and can help model early eye patterning defects, including congenital retinal dystrophy. To conduct the protocol, experience in sterile cell culture and maintenance of human induced pluripotent stem cells is essential; theoretical knowledge of brain development is advantageous. Furthermore, specialized expertise in 3D organoid culture and imaging for the analysis is needed.

Prevalence and Associated Factors of Ocular Manifestations of Acquired Immune Deficiency Syndrome Among Adults at University of Gondar Hospital, North West Ethiopia, 2021.

Acquired immune deficiency syndrome is a disease with common clinical ocular manifestations. Ocular manifestations lead to blindness, which has a common social and economic impact. This study aimed to assess the prevalence and associated factors of ocular manifestations of acquired immune deficiency syndrome among adults at the University of Gondar Hospital, North West Ethiopia, 2021. A cross-sectional study was conducted on 401 patients from June to August 2021. Samples were selected based on a systematic random sampling technique. Data collection was done using structured questionnaires. Data extraction format was used to collect the clinical characteristics of patients including ocular manifestations. Data entry was done by EpiData version 4.6.0.6 and exported to the Statistical Package for the Social Sciences version 26 for data analysis. Associated factors were analyzed by binary logistic regression. P-value <0.05 with a 95% confidence level was used to declare a significant association. A total of 401 patients were involved with a response rate of 91.5%. The overall prevalence of ocular manifestations of acquired immune deficiency syndrome was 28.9%. The common ocular manifestations were seborrheic blepharitis at 16.4% and squamoid conjunctival growth at 4.5%. Age >35 years (AOR=2.52, 95% CI: 1.19, 5.35), Clusters of differentiation 4 count <200 cells/µL (AOR=4.76, 95% CI:2.50, 9.09), World Health Organization stage II (AOR=2.60, 95% CI: 1.23, 5.50), history of eye disease (AOR=3.05, 95% CI: 1.38, 6.72), and duration of Human Immunodeficiency Virus >5 years (AOR=2.79, 95% CI: 1.29, 6.05) were statistically associated with the ocular manifestation of acquired immune deficiency syndrome. In this study, the prevalence of ocular manifestation of acquired immune deficiency syndrome was high. Age, CD4 count, duration of HIV, eye disease history, and WHO clinical staging were the significant factors. Early eye checkups and regular ocular examinations of HIV patients would be helpful.

Holoprosencephaly with a Special Form of Anophthalmia Result from Experimental Induction of bmp4, Oversaturating BMP Antagonists in Zebrafish.

Vision is likely our most prominent sense and a correct development of the eye is at its basis. Early eye development is tightly connected to the development of the forebrain. A single eye field and the prospective telencephalon are situated within the anterior neural plate (ANP). During normal development, both domains are split and consecutively, two optic vesicles and two telencephalic lobes emerge. If this process is hampered, the domains remain condensed at the midline. The resulting developmental disorder is termed holoprosencephaly (HPE). The typical ocular finding associated with intense forms of HPE is cyclopia. However, also anophthalmia and coloboma can be associated with HPE. Here, we report that a correct balance of Bone morphogenetic proteins (BMPs) and their antagonists are important for forebrain and eye field cleavage. Experimental induction of a BMP ligand results in a severe form of HPE showing anophthalmia. We identified a dysmorphic forebrain containing retinal progenitors, which we termed crypt-oculoid. Optic vesicle evagination is impaired due to a loss of rx3 and, consecutively, of cxcr4a. Our data further suggest that the subduction of prospective hypothalamic cells during neurulation and neural keel formation is affected by the induction of a BMP ligand.

Community based cross-sectional survey to assess the conditions of refractive error by eye-screening program in remote area of Saifai, Etawah

Background: Refractive error is a state where an optical system of the eye fails to bring parallel light rays on a point focus at the fovea, due to increase or decrease of the size of the eyeball through any reasons, changes in the refractive index of the component of the eyes or the age related factors. Methods: A community-based cross-sectional survey was conducted in the systemic random sampling without repetitions (SRSWOR) method at the circumference area of 5 km of the Saifai Medical University UPUMS Saifai, Etawah (Uttar Pradesh). The data was collected through the rural program for the control of blindness. Among 1032 samples, for the refractive error, total 237 individuals were registered for the study through the screening programme. Results: The age group 0-19 years concludes 22 (9.28%), for 20-39 concludes 71 (22.95%), for 40-59 years concludes 101 (18.14%) and for the age group above 60, it was 43(48.94%) respectively. Among all the age groups a total of 22.96% responders were diagnosed for the prevalence of refractive error and it was observed more for females 50.63% as compared to males 49.36%. Conclusions: The prevalence of refractive errors refers to the age group of 40-59 years, so for early diagnosis eye care must be included at a particular time difference at a community level through an eye screening program for all the age groups with the main intention to give special cover to the age group of 40-59 years.

Model long-range dependencies for multi-modality and multi-view retinopathy diagnosis through transformers

Early eye examination based on fundus images effectively prevents visual impairment caused by retinopathy. The laborious and error-prone process of interpreting fundus images and the lack of ophthalmologists have driven research toward automated retinopathy diagnosis. However, most previous studies have focused on single-modality fundus images, disregarding the integration of information from multiple views, rendering the results unsatisfactory and inconsistent with clinical practice due to the incomprehensive lesion features and incomplete fundus fields. To address this issue, we introduce multi-modality and multi-view fundus images into the automated retinopathy diagnosis pipeline. In contrast to single fundus images, sequential relationships in multi-modality and multi-view fundus images contain essential long-range dependency information, which is vital for retinopathy diagnosis. Inspired by the recent success of transformers for excavating long-range dependencies in sequence data, in this paper, we propose a transformer-based automated retinopathy diagnosis framework for pathology classification and symptom report generation by integrating multi-modality and multi-view fundus images. Specifically, we present two transformer-based networks to construct long-range dependencies in different fundus images. Moreover, we adopt two novel modules to aggregate features of different modalities and views by modeling long-range dependencies among different fundus image sequences. Experiments are conducted on two in-house datasets, in which each subject provides one color fundus photography image and four-view fundus fluorescein angiography images. The experimental results of retinopathy classification and report generation tasks indicate that our proposed method is superior to other benchmarking methods, achieving a classification accuracy of 85.49% and a report generation BlEU-1 of 0.422.

Group early intervention eye movement desensitization and reprocessing therapy as a video-conference psychotherapy with frontline/emergency workers in response to the COVID-19 pandemic in the treatment of post-traumatic stress disorder and moral injury-An RCT study.

Frontline mental health, emergency, law enforcement, and social workers have faced unprecedented psychological distress in responding to the COVID-19 pandemic. The purpose of the RCT (Randomized Controls Trial) study was to investigate the effectiveness of a Group EMDR (Eye Movement Desensitization and Reprocessing) therapy (Group Traumatic Episode Protocol-GTEP) in the treatment of Post-Traumatic Stress Disorder (PTSD) and Moral Injury. The treatment focus is an early intervention, group trauma treatment, delivered remotely as video-conference psychotherapy (VCP). This early intervention used an intensive treatment delivery of 4x2h sessions over 1-week. Additionally, the group EMDR intervention utilized therapist rotation in treatment delivery. The study's design comprised a delayed (1-month) treatment intervention (control) versus an active group. Measurements included the International Trauma Questionnaire (ITQ), Generalized Anxiety Disorder Assessment (GAD-7), Patient Health Questionnaire (PHQ-9), Moral Injury Events Scale (MIES), and a Quality-of-Life psychometric (EQ-5D), tested at T0, T1: pre-treatment, T2: post-treatment, T3: 1-month follow-up (FU), T4: 3-month FU, and T5: 6-month FU. The Adverse Childhood Experiences - International version (ACEs), Benevolent Childhood Experience (BCEs) was ascertained at pre-treatment only. N = 85 completed the study. Results highlight a significant treatment effect within both active and control groups. Post Hoc comparisons of the ITQ demonstrated a significant difference between T1 pre (mean 36.8, SD 14.8) and T2 post (21.2, 15.1) (t11.58) = 15.68, p < 0.001). Further changes were also seen related to co-morbid factors. Post Hoc comparisons of the GAD-7 demonstrated significant difference between T1 pre (11.2, 4.91) and T2 post (6.49, 4.73) (t = 6.22) = 4.41, p < 0.001; with significant difference also with the PHQ-9 between T1 pre (11.7, 5.68) and T2 post (6.64, 5.79) (t = 6.30) = 3.95, p < 0.001, d = 0.71. The treatment effect occurred irrespective of either ACEs/BCEs during childhood. However, regarding Moral Injury, the MIES demonstrated no treatment effect between T1 pre and T5 6-month FU. The study's findings discuss the impact of Group EMDR therapy delivered remotely as video-conference psychotherapy (VCP) and the benefits of including a therapist/rotation model as a means of treatment delivery. However, despite promising results suggesting a large treatment effect in the treatment of trauma and adverse memories, including co-morbid symptoms, research results yielded no treatment effect in frontline/emergency workers in addressing moral injury related to the COVID-19 pandemic. The NICE (2018) guidance on PTSD highlighted the paucity of EMDR therapy research used as an early intervention. The primary rationale for this study was to address this critical issue. In summary, treatment results for group EMDR, delivered virtually, intensively, using therapist rotation are tentatively promising, however, the moral dimensions of trauma need consideration for future research, intervention development, and potential for further scalability. The data contributes to the emerging literature on early trauma interventions.Clinical Trial Registration:Clinicaltrials.gov, ISRCTN16933691.

Genome-wide screening reveals the genetic basis of mammalian embryonic eye development

BackgroundMicrophthalmia, anophthalmia, and coloboma (MAC) spectrum disease encompasses a group of eye malformations which play a role in childhood visual impairment. Although the predominant cause of eye malformations is known to be heritable in nature, with 80% of cases displaying loss-of-function mutations in the ocular developmental genes OTX2 or SOX2, the genetic abnormalities underlying the remaining cases of MAC are incompletely understood. This study intended to identify the novel genes and pathways required for early eye development. Additionally, pathways involved in eye formation during embryogenesis are also incompletely understood. This study aims to identify the novel genes and pathways required for early eye development through systematic forward screening of the mammalian genome.ResultsQuery of the International Mouse Phenotyping Consortium (IMPC) database (data release 17.0, August 01, 2022) identified 74 unique knockout lines (genes) with genetically associated eye defects in mouse embryos. The vast majority of eye abnormalities were small or absent eyes, findings most relevant to MAC spectrum disease in humans. A literature search showed that 27 of the 74 lines had previously published knockout mouse models, of which only 15 had ocular defects identified in the original publications. These 12 previously published gene knockouts with no reported ocular abnormalities and the 47 unpublished knockouts with ocular abnormalities identified by the IMPC represent 59 genes not previously associated with early eye development in mice. Of these 59, we identified 19 genes with a reported human eye phenotype. Overall, mining of the IMPC data yielded 40 previously unimplicated genes linked to mammalian eye development. Bioinformatic analysis showed that several of the IMPC genes colocalized to several protein anabolic and pluripotency pathways in early eye development. Of note, our analysis suggests that the serine-glycine pathway producing glycine, a mitochondrial one-carbon donator to folate one-carbon metabolism (FOCM), is essential for eye formation.ConclusionsUsing genome-wide phenotype screening of single-gene knockout mouse lines, STRING analysis, and bioinformatic methods, this study identified genes heretofore unassociated with MAC phenotypes providing models to research novel molecular and cellular mechanisms involved in eye development. These findings have the potential to hasten the diagnosis and treatment of this congenital blinding disease.

Assessment of Murine Retinal Acuity Ex Vivo Using Multielectrode Array Recordings.

Visual acuity, measured by resolution of optotypes on a standard eye chart, is a critical clinical test for function of the visual system in humans. Behavioral tests in animals can be used to estimate visual acuity. However, such tests may be limited in the study of mutants or after synthetic vision restoration techniques. Because the total response of the retina to a visual scene is encoded in spiking patterns of retinal ganglion cells, it should be possible to estimate visual acuity in vitro from the retina by analyzing retinal ganglion cell output in response to test stimuli. We created a method, EyeCandy, that combines a visual stimulus-generating engine with analysis of multielectrode array retinal recordings via a machine learning approach to measure murine retinal acuity in vitro. Visual stimuli included static checkerboards, drifting gratings, and letter optotypes. In retinas from wild-type C57Bl/6 mice, retinal acuity measurement for a drifting grating was 0.4 cycles per degree. In contrast, retinas from adult rd1 mice with outer retinal degeneration showed no detectable acuity. A comparison of acuities among different regions of the retina revealed substantial variation, with the inferior-nasal quadrant having highest RA. Letter classification accuracy of a projected Early Treatment Diabetic Retinopathy eye chart reached 99% accuracy for logMAR 3.0 letters. EyeCandy measured a restored RA of 0.05 and 0.08 cycles per degree for static and dynamic stimuli respectively from the retina of the rd1 mouse treated with the azobenzene photoswitch BENAQ. Machine learning may be used to estimate retinal acuity. The use of ex vivo retinal acuity measurement may allow determination of effects of mutations, drugs, injury, or other manipulations on retinal visual function.

The Impact of Family Medicine on Diabetic Eye Care, Screening Programs, Referral Patterns, and Outcomes

Diabetes mellitus is a long-lasting metabolic disease with a complex etiology. It is characterized by elevated blood sugar levels, which are marked by anomalies in insulin secretion, action, or both. Long-term hyperglycemia causes diverse microvascular and macrovascular diabetic complications, which are primarily responsible for the high morbidity and mortality associated with diabetes. Diabetes leads to significant ophthalmological complications among which diabetic retinopathy is thought to be the most frequent cause of blindness in people of working age, with diabetic macular oedema being the most frequent cause of impaired visual acuity among diabetics. The findings of several research studies suggest that the best way to prevent diabetic retinopathy from leading to blindness is through regular assessment and screening so any complications can be addressed as soon as possible. Furthermore, since early diabetic eye disease stages are asymptomatic, screening people with diabetes is essential. As a result, the primary care physician's involvement is essential for enabling an early diagnosis of this condition. Family physicians play an essential role in the early identification and prevention of diabetic retinopathy. They serve as the initial line of contact for managing diabetes and as referral sources when complications arise. The purpose of this research is to review the impact of family medicine on diabetic eye care, screening programs, referral patterns, and outcomes.

Optic nerve infiltration and combined vascular occlusion as a sign of relapse in acute myeloid leukemia

Leukemic infiltration of the optic nerve is considered as a neuro-ophthalmic emergency and may be indicative of systemic and/or central nervous system relapse of the disease. These patients have hyperleukocytosis characterized by increased viscosity of blood causing leukostatic retinopathy and retinal vascular occlusions. In this case report, we describe a young male with simultaneous infiltrative and leukostatic manifestations in the posterior segment of the eye, which was the initial sign of relapse of leukemia. The case highlights the importance of meticulous and early eye examinations in patients with hematological malignancies, as it may impact the long-term survival of the patient.

The influence of predictability, visual contrast, and preview validity on eye movements and N400 amplitude: co-registration evidence that the N400 reflects late processes

ABSTRACT Two eye movement/EEG co-registration experiments investigated effects of predictability, visual contrast, and parafoveal preview in normal reading. Replicating previous studies, in Experiment 1 contrast and predictability additively influenced fixation durations, and in Experiment 2 invalid preview eliminated the predictability effect on early eye movement measures. In both experiments, predictability influenced the amplitude of the N400 component of the fixation-related potential. In Experiment 1, visual contrast did not influence the N400, and in Experiment 2, the effect of predictability on the N400 was larger with invalid preview, in opposition to the eye movement pattern. The N400 may reflect a late process of accessing conceptual representations while the duration of the eyes’ fixation on a word is sensitive to the difficulty of perceptual encoding and early stages of word recognition. The effects of predictability on both fixation duration and the N400 suggest an influence of this variable at two distinct processing stages.

Association of Maternal and Paternal Astigmatism With Child Astigmatism in the Hong Kong Children Eye Study

Parental astigmatism is a factor associated with risk for development of child astigmatism; however, the magnitude of the association has not been determined. To determine the association between parental and child astigmatism. This population-based, cross-sectional study included participants from familial trios, each comprising a child aged 6 to 8 years and both parents, recruited from the Hong Kong Children Eye Study. No restriction criteria were set on the children in terms of refractive status. Data were analyzed from February to June 2022. Cycloplegic autorefraction and autokeratometry were conducted on the children, whereas noncycloplegic autorefraction and autokeratometry were conducted on their parents. The children were categorized into 6 groups on the basis of the severity of astigmatism of both parents. Information on parental education, family income, and children's outdoor and near work time were obtained by questionnaires. The primary outcome was the odds of child astigmatism among the 6 categories of children. Associations of factors with child astigmatism were evaluated by logistic regression analyses. A total of 17 124 participants from 5708 trios (2964 boys and 2754 girls) at a mean (SD) age of 7.32 (0.87) years, and 11 416 parents were examined. Astigmatism of 1.0 D or greater in both parents was associated with greater odds of refractive astigmatism (RA) (odds ratio [OR], 1.62; 95% CI, 1.15-2.26) and corneal astigmatism (CA) (OR, 1.94; 95% CI, 1.50-2.50) in the child. The respective ORs increased to 3.10 (95% CI, 1.34-7.21) and 4.31 (95% CI, 1.76-10.55) when both parents had astigmatism 2.0 D or greater. Higher parental astigmatism conferred higher risks for both RA and CA in children (P for trend <.001). Parental astigmatism was significantly associated with greater odds of corresponding child astigmatism (maternal RA: OR, 0.76; 95% CI, 0.68-0.84; paternal RA: OR, 0.82; 95% CI, 0.74-0.91; maternal CA: OR, 1.70; 95% CI, 1.51-1.93; paternal CA: OR, 1.33; 95% CI, 1.19-1.49). The findings of this cross-sectional study suggest that parental astigmatism may confer an independent and dose-dependent association with child astigmatism. Children with parents with astigmatism should have early eye examinations for timely detection of astigmatism to facilitate age-appropriate vision correction and visual development.

PAX6 disease models for aniridia.

Aniridia is a pan-ocular genetic developmental eye disorder characterized by complete or partial iris and foveal hypoplasia, for which there is no treatment currently. Progressive sight loss can arise from cataracts, glaucoma, and aniridia-related keratopathy, which can be managed conservatively or through surgical intervention. The vast majority of patients harbor heterozygous mutations involving the PAX6 gene, which is considered the master transcription factor of early eye development. Over the past decades, several disease models have been investigated to gain a better understanding of the molecular pathophysiology, including several mouse and zebrafish strains and, more recently, human-induced pluripotent stem cells (hiPSCs) derived from aniridia patients. The latter provides a more faithful cellular system to study early human eye development. This review outlines the main aniridia-related animal and cellular models used to study aniridia and highlights the key discoveries that are bringing us closer to a therapy for patients.

Retinochoroidal microvascular changes in newly developed obese children: an optical coherence tomography angiography study

BackgroundChildhood obesity was associated with retinochoroidal microvascular changes using optical coherence tomography angiography (OCTA), but obesity duration was neglected. Obesity is chronic and progressive and obesity duration is related to microvascular function. Thus, it is important to identify microvascular changes in obese children timely to allow possible interventions with the increase in the number of obese children. This pilot study aimed to characterize retinochoroidal microvascular changes in newly developed obese children compared to age- and sex-matched controls.MethodsForty newly developed obese children and 40 age- and sex-matched controls were recruited. All subjects completed comprehensive eye examinations, including axial length, cycloplegic refraction, optical coherence tomography angiography scans (AngioVue; Optovue Inc), etc.ResultsThere were no statistically significant differences between groups in terms of month age (P = 0.927), spherical equivalent refraction (P = 0.753) and axial length (P = 0.196). Newly developed obese children had lower vessel density (VD) in the inferior parafovea (P = 0.026), nasal parafovea (P = 0.038) and temporal perifovea (P = 0.026) of deep vascular complex (DVC), higher VD in the fovea of superficial vascular complex (P = 0.021) and the fovea of DVC (P = 0.016), and smaller foveal avascular zone (P = 0.003) when compared to controls. Also, no apparent differences in any quadrant of total retinal thickness, subfoveal choroidal thickness (SFCT), and choriocapillaries fow voids were detected (all P > 0.05).ConclusionRetinochoroidal microvascular changes had already occurred in newly developed obese children, so early screening and close follow-up eye examinations were recommended; Retinal microvascular insult may precede its structural change and that retina may be a better candidate to predict the onset of retinochoroidal microvascular changes than choroid in obese children.

Cell fate decisions, transcription factors and signaling during early retinal development.

The development of the vertebrate eyes is a complex process starting from anterior-posterior and dorso-ventral patterning of the anterior neural tube, resulting in the formation of the eye field. Symmetrical separation of the eye field at the anterior neural plate is followed by two symmetrical evaginations to generate a pair of optic vesicles. Next, reciprocal invagination of the optic vesicles with surface ectoderm-derived lens placodes generates double-layered optic cups. The inner and outer layers of the optic cups develop into the neural retina and retinal pigment epithelium (RPE), respectively. In vitro produced retinal tissues, called retinal organoids, are formed from human pluripotent stem cells, mimicking major steps of retinal differentiation in vivo. This review article summarizes recent progress in our understanding of early eye development, focusing on the formation the eye field, optic vesicles, and early optic cups. Recent single-cell transcriptomic studies are integrated with classical in vivo genetic and functional studies to uncover a range of cellular mechanisms underlying early eye development. The functions of signal transduction pathways and lineage-specific DNA-binding transcription factors are dissected to explain cell-specific regulatory mechanisms underlying cell fate determination during early eye development. The functions of homeodomain (HD) transcription factors Otx2, Pax6, Lhx2, Six3 and Six6, which are required for early eye development, are discussed in detail. Comprehensive understanding of the mechanisms of early eye development provides insight into the molecular and cellular basis of developmental ocular anomalies, such as optic cup coloboma. Lastly, modeling human development and inherited retinal diseases using stem cell-derived retinal organoids generates opportunities to discover novel therapies for retinal diseases.

Porcn is essential for growth and invagination of the mammalian optic cup.

Microphthalmia, anophthalmia, and coloboma (MAC) are congenital ocular malformations causing 25% of childhood blindness. The X-linked disorder Focal Dermal Hypoplasia (FDH) is frequently associated with MAC and results from mutations in Porcn, a membrane bound O-acyl transferase required for palmitoylation of Wnts to activate multiple Wnt-dependent pathways. Wnt/β-catenin signaling is suppressed in the anterior neural plate for initiation of eye formation and is subsequently required during differentiation of the retinal pigment epithelium (RPE). Non-canonical Wnts are critical for early eye formation in frog and zebrafish. However, it is unclear whether this also applies to mammals. We performed ubiquitous conditional inactivation of Porcn in mouse around the eye field stage. In Porcn CKO , optic vesicles (OV) arrest in growth and fail to form an optic cup. Ventral proliferation is significantly decreased in the mutant OV, with a concomitant increase in apoptotic cell death. While pan-ocular transcription factors such as PAX6, SIX3, LHX2, and PAX2 are present, indicative of maintenance of OV identity, regional expression of VSX2, MITF, OTX2, and NR2F2 is downregulated. Failure of RPE differentiation in Porcn CKO is consistent with downregulation of the Wnt/β-catenin effector LEF1, starting around 2.5days after inactivation. This suggests that Porcn inactivation affects signaling later than a potential requirement for Wnts to promote eye field formation. Altogether, our data shows a novel requirement for Porcn in regulating growth and morphogenesis of the OV, likely by controlling proliferation and survival. In FDH patients with ocular manifestations, growth deficiency during early ocular morphogenesis may be the underlying cause for microphthalmia.

Chromatin Accessibility and Transcriptional Differences in Human Stem Cell-Derived Early-Stage Retinal Organoids.

Retinogenesis involves the specification of retinal cell types during early vertebrate development. While model organisms have been critical for determining the role of dynamic chromatin and cell-type specific transcriptional networks during this process, an enhanced understanding of the developing human retina has been more elusive due to the requirement for human fetal tissue. Pluripotent stem cell (PSC) derived retinal organoids offer an experimentally accessible solution for investigating the developing human retina. To investigate cellular and molecular changes in developing early retinal organoids, we developed SIX6-GFP and VSX2-tdTomato (or VSX2-h2b-mRuby3) dual fluorescent reporters. When differentiated as 3D organoids these expressed GFP at day 15 and tdTomato (or mRuby3) at day 25, respectively. This enabled us to explore transcriptional and chromatin related changes using RNA-seq and ATAC-seq from pluripotency through early retina specification. Pathway analysis of developing organoids revealed a stepwise loss of pluripotency, while optic vesicle and retina pathways became progressively more prevalent. Correlating gene transcription with chromatin accessibility in early eye field development showed that retinal cells underwent a clear change in chromatin landscape, as well as gene expression profiles. While each dataset alone provided valuable information, considering both in parallel provided an informative glimpse into the molecular nature eye development.

Zebrafish Model of Stickler Syndrome Suggests a Role for Col2a1a in the Neural Crest during Early Eye Development.

Most cases of Stickler syndrome are due to autosomal-dominant COL2A1 gene mutations leading to abnormal type II collagen. Ocular findings include axial eye lengthening with vitreal degeneration and early-onset glaucoma, which can result in vision loss. Although COL2A1 is a major player in cartilage and bone formation, its specific role in eye development remains elusive. We investigated the role of Col2a1a in neural crest migration and differentiation during early zebrafish eye development. In situ hybridization, immunofluorescence, live imaging, exogenous treatments [10 μM diethylaminobenzaldehyde (DEAB), 100 nM all-trans retinoic acid (RA) and 1–3% ethanol (ETOH)] and morpholino oligonucleotide (MO) injections were used to analyze wildtype Casper (roy−/−;nacre−/−), TgBAC(col2a1a::EGFP), Tg(sox10::EGFP) and Tg(foxd3::EGFP) embryos. Col2a1a colocalized with Foxd3- and Sox10-positive cells in the anterior segment and neural crest-derived jaw. Col2a1a expression was regulated by RA and inhibited by 3% ETOH. Furthermore, MO knockdown of Col2a1a delayed jaw formation and disrupted the ocular anterior segment neural crest migration of Sox10-positive cells. Interestingly, human COL2A1 protein rescued the MO effects. Altogether, these results suggest that Col2a1a is a downstream target of RA in the cranial neural crest and is required for both craniofacial and eye development.

EyeVolve, a modular PYTHON based model for simulating developmental eye type diversification.

Vision is among the oldest and arguably most important sensory modalities for animals to interact with their external environment. Although many different eye types exist within the animal kingdom, mounting evidence indicates that the genetic networks required for visual system formation and function are relatively well conserved between species. This raises the question as to how common developmental programs are modified in functionally different eye types. Here, we approached this issue through EyeVolve, an open-source PYTHON-based model that recapitulates eye development based on developmental principles originally identified in Drosophila melanogaster. Proof-of-principle experiments showed that this program’s animated timeline successfully simulates early eye tissue expansion, neurogenesis, and pigment cell formation, sequentially transitioning from a disorganized pool of progenitor cells to a highly organized lattice of photoreceptor clusters wrapped with support cells. Further, tweaking just five parameters (precursor pool size, founder cell distance and placement from edge, photoreceptor subtype number, and cell death decisions) predicted a multitude of visual system layouts, reminiscent of the varied eye types found in larval and adult arthropods. This suggests that there are universal underlying mechanisms that can explain much of the existing arthropod eye diversity. Thus, EyeVolve sheds light on common principles of eye development and provides a new computational system for generating specific testable predictions about how development gives rise to diverse visual systems from a commonly specified neuroepithelial ground plan.