Differences in inhibitory control in two species of Tanganyikan bower-building cichlids contrasting in building flexibility.

A central challenge in understanding the evolution of cognition is the ability to compare a set of species differing in a trait of interest while being ecologically and phylogenetically close. Here, we examine whether differences in bower-building flexibility are related to differences in cognitive flexibility between two Tanganyikan cichlids. Cognitive flexibility enables animals to modify their decision rules when faced with new situations, and inhibitory control, the ability to inhibit a normally favoured response, is an essential component of this capacity. We tested male Aulonocranus dewindti and Cyathopharynx furcifer in a choice-against-preference paradigm. Both species clean their bowers of foreign objects and we found that both preferred to remove a snail shell over a stone. We tested their ability to modify this preference and learned to preferably select the stone instead of the shell. Although neither species showed clear learning of the new preference rule, both demonstrated inhibitory control through increased decision times and manipulations of the objects when selecting the stone. Specifically, A. dewindti, the species exhibiting greater behavioural flexibility in the construction of their bowers, selected the stone in fewer trials than C. furcifer, providing support for a link between behavioural flexibility in bower construction and cognitive flexibility.

Retinal response to light exposure in BEST1-mutant dogs evaluated with ultra-high resolution OCT.

Mutations in BEST1 cause an autosomal recessive disease in dogs where the earliest changes localize to the photoreceptor-RPE interface and show a retina-wide micro-detachment that is modulated by light exposure. The purpose of this study was to define the spatial and temporal details of the outer retina and its response to light with ultra-high resolution OCT across a range of ages and with different BEST1 mutations. Three retinal regions were selected in each eye: near the fovea-like area, near the optic nerve, both in the tapetal area, and inferior to the optic nerve in the non-tapetal area. The OS+ slab thickness was defined between the peak near the junction of inner and outer segments (IS/OS) and the transition between basal RPE, Bruch membrane, choriocapillaris and proximal tapetum (RPE/T). In wildtype (WT) dogs, two tapetal regions showed additional hyperscattering OCT peaks within the OS+ slab likely representing cone and rod outer segment tips (COST and ROST). The inferior non-tapetal region of WT dogs had only one of these peaks, likely ROST. In dogs with BEST1 mutations, all three locations showed a single peak, likely suggesting optical silence of COST. Light-dependent expansion of the micro-detachment by about 10 um was detectable in both tapetal and non-tapetal retina across all ages and BEST1 mutations.

Vocal complexity in a socially complex corvid: gradation, diversity and lack of common call repertoire in male rooks.

Vocal communication is widespread in animals, with vocal repertoires of varying complexity. The social complexity hypothesis predicts that species may need high vocal complexity to deal with complex social organization (e.g. have a variety of different interindividual relations). We quantified the vocal complexity of two geographically distant captive colonies of rooks, a corvid species with complex social organization and cognitive performances, but understudied vocal abilities. We quantified the diversity and gradation of their repertoire, as well as the inter-individual similarity at the vocal unit level. We found that males produced call units with lower diversity and gradation than females, while song units did not differ between sexes. Surprisingly, while females produced highly similar call repertoires, even between colonies, each individual male produced almost completely different call repertoires from any other individual. These findings question the way male rooks communicate with their social partners. We suggest that each male may actively seek to remain vocally distinct, which could be an asset in their frequently changing social environment. We conclude that inter-individual similarity, an understudied aspect of vocal repertoires, should also be considered as a measure of vocal complexity.

Cognitive flexibility in a Tanganyikan bower-building cichlid, Aulonocranus dewindti.

Cognitive flexibility, the ability to modify one's decision rules to adapt to a new situation, has been extensively studied in many species. In fish, though, data on cognitive flexibility are scarce, especially in the wild. We studied a lekking species of cichlid fish in Lake Tanganyika, Aulonocranus dewindti. Males create sand bowers as spawning sites and maintain them by removing any objects falling into it. In the first part of our experiment, we investigated the existence of spontaneous decision rules for the maintenance of the bowers. We showed that if a snail shell and a stone are placed in their bower, fish prefer to remove the shell first. In the second phase of our experiment, we took advantage of this spontaneous decision rule to investigate whether this rule was flexible. We tested five individuals in a choice against preference task, in which the fish had to modify their preference rule and remove the stone first to be allowed to then remove the shell and have a clean bower. While there was no overall trend towards flexibility in this task, there was variation at an individual level. Some individuals increased their preference for removing the shell first, deciding quickly and with little exploration of the objects. Others were more successful at choosing against preference and showed behaviours suggesting self-regulatory inhibition abilities. Bower-building cichlids could therefore be a promising model to study cognitive flexibility, and other aspects of animal cognition in the wild.

Spontaneous vocal coordination of vocalizations to water noise in rooks (Corvus frugilegus): An exploratory study.

The ability to control one's vocal production is a major advantage in acoustic communication. Yet, not all species have the same level of control over their vocal output. Several bird species can interrupt their song upon hearing an external stimulus, but there is no evidence how flexible this behavior is. Most research on corvids focuses on their cognitive abilities, but few studies explore their vocal aptitudes. Recent research shows that crows can be experimentally trained to vocalize in response to a brief visual stimulus. Our study investigated vocal control abilities with a more ecologically embedded approach in rooks. We show that two rooks could spontaneously coordinate their vocalizations to a long-lasting stimulus (the sound of their small bathing pool being filled with a water hose), one of them adjusting roughly (in the second range) its vocalizations as the stimuli began and stopped. This exploratory study adds to the literature showing that corvids, a group of species capable of cognitive prowess, are indeed able to display good vocal control abilities.

Both sheep and goats can solve inferential by exclusion tasks.

Despite the domestication of sheep and goats by humans for several millennia, we still lack comparative data on their cognitive capacity. Comparing the cognitive skills of farm animals can help understand the evolution of cognition. In this study, we compared the performances of sheep and goats in inference by exclusion tasks. We implemented two tasks, namely a cup task and a tube task, to identify whether success in solving the task could be attributed to either low-level mechanisms (avoiding the empty location strategy) or to deductive reasoning (if two possibilities A and B, but not A, then it must be B). In contrast to a previous study comparing goats and sheep in a cup task, we showed that both species solved the inferential condition with high success rates. In the tube task, performances could not be explained by alternative strategies such as avoiding the empty tube or preferring the bent tube. When applying a strict set of criteria concerning responses in all conditions and controlling for the potential effects of experience, we demonstrate that two individuals, a goat and a sheep, fulfil these criteria. This suggests that sheep and goats are able to make inferences based on deductive reasoning.

Targeting ON-bipolar cells by AAV gene therapy stably reverses LRIT3-congenital stationary night blindness.

SignificanceCanine models of inherited retinal diseases have helped advance adeno-associated virus (AAV)-based gene therapies targeting specific cells in the outer retina for treating blinding diseases in patients. However, therapeutic targeting of diseases such as congenital stationary night blindness (CSNB) that exhibit defects in ON-bipolar cells (ON-BCs) of the midretina remains underdeveloped. Using a leucine-rich repeat, immunoglobulin-like and transmembrane domain 3 (LRIT3) mutant canine model of CSNB exhibiting ON-BC dysfunction, we tested the ability of cell-specific AAV capsids and promotors to specifically target ON-BCs for gene delivery. Subretinal injection of one vector demonstrated safety and efficacy with robust and stable rescue of electroretinography signals and night vision up to 1 y, paving the way for clinical trials in patients.

Monocular retinopathy of prematurity-like retinal vasculopathy in a dog.

PURPOSE: To describe a case of monocular retinopathy of prematurity (ROP)-like vasculopathy without oxygen supplementation in the dog. METHODS: Fundus photographs (RetCam), spectral-domain optical coherence tomography (sdOCT), confocal scanning laser ophthalmoscopy (cSLO), and fluorescein angiography (FA), as well as postmortem histology and immunohistochemistry (Collagen IV and anti-vWF antibodies), were carried out to characterize the vascular abnormalities. RESULTS: Ophthalmic examination showed peripheral and mid-temporal avascular areas in the tapetal region, neovascularization and abnormally dilated and tortuous retinal vessels in the left eye. sdOCT demonstrated not only cross-sectional views of preretinal fibrovascular proliferation but also extensive proliferation extraretinally into the vitreous. FA emphasized demarcation of vascular and avascular zones with neovascular tufts "popcorns." Histology and immunohistochemistry confirmed presence of abnormally dilated vessels and the intravitreal blood vessels. CONCLUSIONS: ROP is a disease of abnormally developed retinal vascularization associated with oxygen supplementation therapy, potentially causing blindness in premature infants. Although the mechanism of ROP-like vasculopathy in our case is unclear, it is important to appreciate that the abnormal vascular pattern seen in ROP in premature infants can occur in canines without oxygen administration.

scAAVengr, a transcriptome-based pipeline for quantitative ranking of engineered AAVs with single-cell resolution.

Background: Adeno-associated virus (AAV)-mediated gene therapies are rapidly advancing to the clinic, and AAV engineering has resulted in vectors with increased ability to deliver therapeutic genes. Although the choice of vector is critical, quantitative comparison of AAVs, especially in large animals, remains challenging. Methods: Here, we developed an efficient single-cell AAV engineering pipeline (scAAVengr) to simultaneously quantify and rank efficiency of competing AAV vectors across all cell types in the same animal. Results: To demonstrate proof-of-concept for the scAAVengr workflow, we quantified - with cell-type resolution - the abilities of naturally occurring and newly engineered AAVs to mediate gene expression in primate retina following intravitreal injection. A top performing variant identified using this pipeline, K912, was used to deliver SaCas9 and edit the rhodopsin gene in macaque retina, resulting in editing efficiency similar to infection rates detected by the scAAVengr workflow. scAAVengr was then used to identify top-performing AAV variants in mouse brain, heart, and liver following systemic injection. Conclusions: These results validate scAAVengr as a powerful method for development of AAV vectors. Funding: This work was supported by funding from the Ford Foundation, NEI/NIH, Research to Prevent Blindness, Foundation Fighting Blindness, UPMC Immune Transplant and Therapy Center, and the Van Sloun fund for canine genetic research.

Gene therapy is an experimental approach to treating disease that involves altering faulty genes or replacing them with new, working copies. Most often, the new genetic material is delivered into cells using a modified virus that no longer causes disease, called a viral vector. Virus-mediated gene therapies are currently being explored for degenerative eye diseases, such as retinitis pigmentosa, and neurological disorders, like Alzheimer's and Parkinson's disease. A number of gene therapies have also been approved for treating some rare cancers, blood disorders and a childhood form of motor neuron disease. Despite the promise of virus-mediated gene therapy, there are significant hurdles to its widespread success. Viral vectors need to deliver enough genetic material to the right cells without triggering an immune response or causing serious side effects. Selecting an optimal vector is key to achieving this. A type of viruses called adeno-associated viruses (AAV) are prime candidates, partly because they can be easily engineered. However, accurately comparing the safety and efficacy of newly engineered AAVs is difficult, due to variation between test subjects and the labor and cost involved in careful testing. Öztürk et al. addressed this issue by developing an experimental pipeline called scAAVengr for comparing gene therapy vectors head-to-head. The process involves tagging potential AAV vectors with unique genetic barcodes, which can then be detected and quantified in individual cells using a technique called single-cell RNA sequencing. This means that when several vectors are used to infect lab-grown cells or a test animal at the same time, they can be tracked. The vectors can then be ranked on their ability to infect specific cell types and deliver useful genetic material. Using scAAVengr, Öztürk et al. compared viral vectors designed to target the light-sensitive cells of the retina, which allow animals to see. First, a set of promising viral vectors were evaluated using the scAAVengr pipeline in the eyes of marmosets and macaques, two small primates. Precise levels and locations of gene delivery were quantified. The top-performing vector was then identified and used to deliver Cas9, a genome editing tool, to primate retinas. Öztürk et al. also used scAAVengr to compare viral vectors in mice, analysing the vectors' ability to deliver their genetic cargo to the brain, heart, and liver. These experiments demonstrated that scAAVengr can be used to evaluate vectors in multiple tissues and in different organisms. In summary, this work outlines a method for identifying and precisely quantifying the performance of top-performing viral vectors for gene therapy. By aiding the selection of optimal viral vectors, the scAAVengr pipeline could help to improve the success of preclinical studies and early clinical trials testing gene therapies.

Optic nerve colobomas associated with unilateral focal serous retinal detachment in a dog - In-vivo imaging and outcome following laser retinopexy.

PURPOSE: To describe the ophthalmoscopic, in-vivo imaging, fluorescein angiography, and therapeutic photocoagulation outcome in a case of bilateral optic nerve colobomas associated with focal unilateral retinal detachment in a dog. METHODS: Pretraining eye examination of a 1.6-year-old female German shepherd service dog showed a focal juxta-papillary bullous retinal separation in the right eye. In vivo imaging and angiography were performed under general anesthesia using optical coherence tomography. Nonoverlapping diode laser burns were applied through an operating microscope adapter to selected areas along the leading margins of the detachment. RESULTS: The funduscopic examination and in-vivo imaging revealed bilateral optic nerve colobomas associated with a focal bullous detachment in the right eye. Fluorescein angiography showed absence of blood vessel leakage and absence of staining inside of the retinal elevation. Photocoagulation induced immediate changes in retinal layer reflectivity. Three months post-photocoagulation, the retinal detachment had improved and scarring of the burns was visible. One and two years post-procedure, the retinal detachment resolved. CONCLUSIONS: Optical coherence tomography (OCT) imaging provides a detailed analysis of the retinal abnormalities associated with the clinical lesion. Laser retinopexy is a valid therapeutic option to limit the extension of the detachment.

Gene therapy reforms photoreceptor structure and restores vision in NPHP5-associated Leber congenital amaurosis.

The inherited childhood blindness caused by mutations in NPHP5, a form of Leber congenital amaurosis, results in abnormal development, dysfunction, and degeneration of photoreceptors. A naturally occurring NPHP5 mutation in dogs leads to a phenotype that very nearly duplicates the human retinopathy in terms of the photoreceptors involved, spatial distribution of degeneration, and the natural history of vision loss. We show that adeno-associated virus (AAV)-mediated NPHP5 gene augmentation of mutant canine retinas at the time of active degeneration and peak cell death stably restores photoreceptor structure, function, and vision with either the canine or human NPHP5 transgenes. Mutant cone photoreceptors, which failed to form outer segments during development, reform this structure after treatment. Degenerating rod photoreceptor outer segments are stabilized and develop normal structure. This process begins within 8 weeks after treatment and remains stable throughout the 6-month posttreatment period. In both photoreceptor cell classes mislocalization of rod and cone opsins is minimized or reversed. Retinal function and functional vision are restored. Efficacy of gene therapy in this large animal ciliopathy model of Leber congenital amaurosis provides a path for translation to human treatment.

Conflict management in rooks (Corvus frugilegus): Victims do not display post-conflict affiliation but avoid their former aggressor.

Many social species use post-conflict behaviors to mitigate the consequences of conflicts. One of these behaviors is the victim's affiliation with its former opponent following conflict in an attempt to restore the damaged relationship. The victim can also affiliate with a third party. Affiliation with former opponents and third parties also alleviates stress. Studies of conflict management strategies in birds mostly concern corvids, and more specifically rooks (Corvus frugilegus). In this colonial pair-bonded species, the most valuable relationship is with the mate. It is rarely conflictual, meaning that there is generally no need for any post-conflict affiliation. However, conflicts occur with other social partners, and victims may primarily use third-party affiliation to avoid renewed aggression after conflicts. Previous studies of rooks failed to show a protective role of third-party affiliations for rook victims. The present study seeks to further investigate the use and efficiency of these conflict management strategies from the victim's perspective. We recorded conflicts and post-conflict behaviors in captive rooks using the standard post-conflict matched control comparison method. Victims did not affiliate with their former opponent or with third parties after conflict, but rather avoided their former aggressor, thus successfully limiting the risk of renewed aggression. Post-conflict affiliations are not observed in all rook colonies, suggesting that avoidance of the former aggressor may be a more commonly used strategy than previously thought.

Dose Range Finding Studies with Two RPGR Transgenes in a Canine Model of X-Linked Retinitis Pigmentosa Treated with Subretinal Gene Therapy.

Recombinant adeno-associated viral (rAAV) vector-mediated gene therapy is being developed to treat X-linked retinitis pigmentosa (XLRP) in patients with mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene. In preparation for a clinical gene therapy trial, we conducted dose range finding (DRF) studies with an AAV2 capsid with three surface tyrosine residues changed to phenylalanine (AAV2tYF) vector administered by subretinal injection in a naturally occurring RPGR-mutant canine model (XLPRA2) to compare two different human RPGR (hRPGR) transgenes and to establish a reasonable starting dose for a clinical trial. Different dose levels of two candidate vectors (0.15 mL at 1.2 × 1010-3.0 × 1012 vg/mL of rAAV2tYF-GRK1-hRPGRco or 4 × 1010-3.0 × 1012 vg/mL of rAAV2tYF-GRK1-hRPGRstb), 6.0 × 1011 vg/mL rAAV5-GRK1-hRPGRco reference vector or Vehicle were subretinally administered, and the dogs were followed for 8 weeks postdose. Ophthalmic examinations, analyses of retinal structure by in vivo imaging using confocal scanning laser ophthalmoscopy (cSLO)/optical coherence tomography (OCT) in the Lower (4.0 × 1010 vg/mL) and Lowest (1.2 × 1010 vg/mL) Doses, immunological responses by cell based assays or enzyme-linked immunosorbent assay, RPGR transgene expression, and reversal of opsin mislocalization by immunohistochemistry were performed. No sustained signs of ocular discomfort or ophthalmic complications were noted in any of the injected eyes except some in the High Dose group (3.0 × 1012 vg/mL), which showed signs of retinal detachment and inflammation. A change in fundus reflectivity suggestive of a rescue effect was seen in the High, Mid (6.0 × 1011 vg/mL), and Low (1.2 × 1011 vg/mL) Dose groups. cSLO/OCT demonstrated qualitative and quantitative evidence of rescue effect in eyes treated with the Lower Dose. Anti-hRPGR antibodies were absent, but neutralizing antibody titers against AAV2 were detected in all animals dosed with rAAV2tYF in an apparent dose-related pattern. RPGR expression was stronger for rAAV2tYF-GRK1-hRPGRco compared to rAAV2tYF-GRK1-hRPGRstb at all dose levels. Subretinal administration of rAAV2tYF-GRK1-hRPGRco and rAAV2tYF-GRK1-hRPGRstb both corrected rod and cone opsin mislocalization, two early markers of disease in the XLPRA2 canine model of RPGR-XLRP. These results support the selection and use of rAAV2tYF-GRK1-hRPGRco (AGTC-501) and guided the initial doses in clinical studies in patients with XLRP caused by RPGR mutations.

Social learning in great white pelicans (Pelecanus onocrotalus): A preliminary study.

Great white pelicans (Pelecanus onocrotalus) exhibit life-history parameters and ecological traits thought to be associated with social learning, and advanced cognitive processing more generally. In this study we investigated whether this species can acquire novel behavior socially in a foraging context. Birds from the test group watched a trained conspecific opening an opaque box containing a food reward by using its beak, whereas the control group had no demonstrator but saw the box for an equivalent time span. Individuals from both groups were subsequently allowed access to the box. Subjects of the test group performed significantly better than the control group. This is the first experimental evidence of social learning in a cooperatively hunting bird. Further studies are needed in order to shed light on the factors favoring the evolution of this capacity, by testing different pelican species that vary in their ecology.

In-vivo longitudinal changes in thickness of the postnatal canine retina.

The objectives of the present work were to assess by spectral domain optical coherence tomography (OCT) the changes in thickness of the outer nuclear layer (ONL), the ONL + photoreceptor inner segment (IS), and the retinal thickness, as a function of age in the normal canine retina. OCT retinal scans extending from the edge of the optic nerve head (ONH) along the superior and inferior meridians were captured in both eyes of 17 normal dogs at age ranging from 4 to 119 weeks. The different parameters along the superior and the inferior regions were determined following manual segmentation using the Heidelberg Eye Explorer software. Changes in thickness with age were modeled using one-phase exponential decay models. In vivo OCT imaging results showed no interocular statistically significant differences in ONL, ONL + IS, and retinal thickness at any age. All three parameters were however found to be statistically significantly thicker in the superior vs inferior retina. A rapid thinning of the three layers occurs in both the superior and inferior retina between 4 and 12 weeks of age, before reaching a plateau at around 20 weeks of age. In conclusion, the ONL, ONL + IS, and retinal thickness of the normal canine retina decrease significantly during the first three postnatal months, and is likely attributed to an overall increase in the eye volume and tangential dispersion of the photoreceptor since early photoreceptor developmental cell death is very limited at that age. Establishment of the natural history of ONL, ONL + IS, and retinal thinning will allow a more accurate assessment of the progression of a retinal degenerative condition as well as facilitate the detection of positive rescue effect of novel retinal therapies evaluated in this large animal model.

Toxicity and Efficacy Evaluation of an Adeno-Associated Virus Vector Expressing Codon-Optimized RPGR Delivered by Subretinal Injection in a Canine Model of X-linked Retinitis Pigmentosa.

Applied Genetic Technologies Corporation (AGTC) is developing a recombinant adeno-associated virus (rAAV) vector AGTC-501, also designated rAAV2tYF-GRK1-hRPGRco, to treat X-linked retinitis pigmentosa (XLRP) in patients with mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene. The vector contains a codon-optimized human RPGR cDNA (hRPGRco) driven by a photoreceptor-specific promoter (G protein-coupled receptor kinase 1 [GRK1]), and is packaged in an AAV2 capsid variant with three surface tyrosine residues changed to phenylalanine (AAV2tYF). We conducted a toxicity and efficacy study of this vector administered by subretinal injection in the naturally occurring RPGR mutant (X-linked progressive retinal atrophy 2 [XLPRA2]) dog model. Sixteen RPGR mutant dogs divided into four groups of three to five animals each received either a subretinal injection of 0.07 mL of AGTC-501 at low (1.2 × 1011 vector genome [vg]/mL), mid (6 × 1011 vg/mL), or high dose (3 × 1012 vg/mL), or of vehicle control in the right eye at early-stage disease. The left eye remained untreated. Subretinal injections were well tolerated and were not associated with systemic toxicity. Electroretinography, in vivo retinal imaging, and histological analysis showed rescue of photoreceptor function and structure in the absence of ocular toxicity in the low- and mid-dose treatment groups when compared with the vehicle-treated group. The high-dose group showed evidence of both photoreceptor rescue and posterior segment toxicity. These results support the use of AGTC-501 in clinical studies with patients affected with XLRP caused by RPGR mutations and define the no-observed-adverse-effect level at 6 × 1011 vg/mL.

Long-Term Structural Outcomes of Late-Stage RPE65 Gene Therapy.

The form of hereditary childhood blindness Leber congenital amaurosis (LCA) caused by biallelic RPE65 mutations is considered treatable with a gene therapy product approved in the US and Europe. The resulting vision improvement is well accepted, but long-term outcomes on the natural history of retinal degeneration are controversial. We treated four RPE65-mutant dogs in mid-life (age = 5-6 years) and followed them long-term (4-5 years). At the time of the intervention at mid-life, there were intra-ocular and inter-animal differences in local photoreceptor layer health ranging from near normal to complete degeneration. Treated locations having more than 63% of normal photoreceptors showed robust treatment-related retention of photoreceptors in the long term. Treated regions with less retained photoreceptors at the time of the intervention showed progressive degeneration similar to untreated regions with matched initial stage of disease. Unexpectedly, both treated and untreated regions in study eyes tended to show less degeneration compared to matched locations in untreated control eyes. These results support the hypothesis that successful long-term arrest of progression with RPE65 gene therapy may only occur in retinal regions with relatively retained photoreceptors at the time of the intervention, and there may be heretofore unknown mechanisms causing long-distance partial treatment effects beyond the region of subretinal injection.

Focal/multifocal and geographic retinal dysplasia in the dog-In vivo retinal microanatomy analyses.

PURPOSE: To examine the in vivo microanatomy of retinal folds and geographic lesions in dogs with acquired or inherited retinal dysplasia. MATERIAL AND METHODS: Thirteen dogs had retinal microanatomy evaluation under general anesthesia using cSLO/sdOCT; two eyes had noninherited multifocal retinal folds, five had inherited multifocal retinal folds (drd1 or drd2), and 10 geographic retinal dysplasia. Retinas from two drd2 carrier dogs were examined by histology and immunohistochemistry (IHC) after in vivo imaging. RESULTS: Retinal folds are the common feature of acquired focal/multifocal or geographic retinal dysplasia, are indistinguishable structurally from those associated with syndromic oculoskeletal dysplasia, and represent outer nuclear layer invaginations and rosettes visible by sdOCT. In dogs heterozygous for oculoskeletal dysplasia, the folds form clusters in a perivascular distribution along superior central vessels. IHC confirmed photoreceptor identity in the retinal folds. The geographic dysplasia plaques are not focally detached, but have inner retinal disorganization and intense autofluorescence in cSLO autofluorescence mode that is mainly limited to the geographic lesion, but is not uniform and in some extends beyond the plaques. CONCLUSION: We propose that the autofluorescent characteristic of the geographic lesions is associated with an inner retinal disruption associated with perivascular or infiltrating macrophages and phagocytosis of cellular debris. As well, we suggest restructuring the examination forms to distinguish the folds that are sporadically distributed from those that have a perivascular distribution as the latter likely represent carriers for drd. In this latter group, DNA testing would be a helpful tool to provide specific breeding advice.