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Purpose: To correlate clinical features, molecular genetic findings, and visual acuity in a cohort of patients clinically diagnosed with oculocutaneous albinism.Design: Retrospective chart reviewMethods: 58 charts met the inclusion criteria. Clinical examination, ancillary testing, and molecular genetic diagnoses were extracted. A novel clinical albinism score (CAS) was developed.Results: A least one likely pathogenic mutation was found in 44/58 (75.9%) patients. Mutations in the OCA1 gene were the most common (52.3%), followed by OCA2 (34%), OCA4 (2.3%), OA1 (6.8%), and HPS (4.5%). Thirty-four percentage of patients had a complete genotype, 41% had one mutation found and 24% had negative genetic testing. CAS was statistically significantly higher in patients with complete genotype, versus patients with one or no mutations found (p < .01). Better visual acuity was associated with lower CAS and fewer disease-causing mutations (p < .01). Foveal defects and iris transillumination were associated with a higher number of mutations (p < .01). Patients with nystagmus or anomalous optic nerves had worse visual acuity than those who did not (p < .01, p < .05).Conclusions: Patients with a complete genotype were more likely to have higher CAS. Vision loss correlated with complete phenotype and higher CAS, the presence of nystagmus and anomalous optic nerves. Patients with features of albinism in whom an incomplete genotype was found had better vision than those with complete genotype, suggesting a mild occult mutation or modifier variant. Genetic diagnosis is vital for complete diagnosis, counseling, and family planning.

Aniridia patients have poor visual acuity and iris malformation. The fovea in these patients is underdeveloped, but the relationship between structure and electrophysiologic function remains incompletely understood. This study correlates electrophysiology, visual acuity and optical coherence tomography (OCT) in patients with aniridia secondary to mutations in the PAX6 gene and compares with age-similar controls. Patients were recruited from clinical practice. The mfERG protocol was a 4-min 103-hexagon protocol covering approximately 40° in diameter of central retina. Diagnosys full-field ERG (ffERG) and VERIS multifocal ERG (mfERG) were obtained using standard International Society for Clinical Electrophysiology of Vision protocols. OCT central thickness was recorded, and an OCT foveal score was calculated. Nonparametric permutation testing was utilized to determine the statistical significance. A total of 6 aniridia patients and 25 control patients were recruited. On mfERG, aniridia patients had significantly lower amplitudes in rings 1–3 (p = 0.0006, 0.0013, 0.0132), shorter latencies in ring 1 (p = 0.0312) and longer latencies in rings 5 and 6 (p = 0.0026, p = 0.0042) than controls. There was a significantly positive relationship in aniridia patients between logMAR visual acuity and mfERG amplitude in ring 4 (p = 0.0392) and ring 5 (p = 0.0489). On ffERG, there was no difference in amplitudes, though photopic 3.0 a- and b-wave latency, 30 Hz flicker latency and scotopic 0.01 b-wave latency were significantly longer in aniridia patients versus control (p = 0.0018, 0.0.0005, 1.00 x $$10^{{ - 4}}$$ , 0.0198). Thicker central macula on OCT correlated with lower mfERG amplitudes in rings 4–6 (p = 0.0369, 0.0292, 0.0255). There was no correlation between visual acuity and central macular thickness or foveal hypoplasia score as determined by OCT. Higher amplitude on mfERG correlated with poorer visual acuity in rings 4 and 5 in patients with PAX6 mutations. The slope of the change in amplitude from central to peripheral rings on the mfERG is significantly different in aniridia patients compared to controls, with a slower drop-off of amplitude from center to periphery. Additionally, mfERG in aniridia showed lower amplitudes than controls in rings 1–3. These changes along with the lack of correlation between visual acuity and central macular thickness/OCT score suggest that changes in electrical topography may be important to visual deficits in patients with PAX6 gene mutations.

Bardet Biedl Syndrome (BBS) is an autosomal recessive disorder caused by mutations in at least 22 different genes. A constant feature is early onset retinal degeneration leading to blindness, with variable central obesity, polydactyly, renal failure, and developmental anomalies. BBS type 10 (BBS10) is a common form caused by mutations in the BBS10 gene encoding a chaperonin-like protein. There are currently no treatments for the progressive vision loss. To aid in treatment development, a BBS10 mouse model was developed by knocking out the Bbs10 gene. Using optical coherence tomography (OCT), electroretinography (ERG), and a visually guided swim assay (VGSA), we demonstrate that Bbs10-/- mice have progressive retinal degeneration. Cone electrical function was absent although cones were anatomically present on histology and retained partial function based on VGSA. The retinal outer nuclear layer (photoreceptor nuclei) progressively thinned as demonstrated on OCT and histology, and rod electrical activity decreased over time on ERG. These phenotypes are more rapidly progressive than retinal degeneration in the Bbs1M390R/M390R knock-in mouse. They are consistent with a cone-rod dystrophy distinct from typical rod-cone degeneration in retinitis pigmentosa and recapitulate aspects of retinal degeneration observed in humans with BBS10. This study has implications for BBS10 gene therapy.

Aniridia patients have poor visual acuity and iris malformation. The fovea in these patients is underdeveloped, but the relationship between structure and electrophysiologic function remains incompletely understood. This study correlates electrophysiology, visual acuity and optical coherence tomography (OCT) in patients with aniridia secondary to mutations in the PAX6 gene and compares with age-similar controls.Patients were recruited from clinical practice. The mfERG protocol was a 4-min 103-hexagon protocol covering approximately 40° in diameter of central retina. Diagnosys full-field ERG (ffERG) and VERIS multifocal ERG (mfERG) were obtained using standard International Society for Clinical Electrophysiology of Vision protocols. OCT central thickness was recorded, and an OCT foveal score was calculated. Nonparametric permutation testing was utilized to determine the statistical significance.A total of 6 aniridia patients and 25 control patients were recruited. On mfERG, aniridia patients had significantly lower amplitudes in rings 1-3 (p = 0.0006, 0.0013, 0.0132), shorter latencies in ring 1 (p = 0.0312) and longer latencies in rings 5 and 6 (p = 0.0026, p = 0.0042) than controls. There was a significantly positive relationship in aniridia patients between logMAR visual acuity and mfERG amplitude in ring 4 (p = 0.0392) and ring 5 (p = 0.0489). On ffERG, there was no difference in amplitudes, though photopic 3.0 a- and b-wave latency, 30 Hz flicker latency and scotopic 0.01 b-wave latency were significantly longer in aniridia patients versus control (p = 0.0018, 0.0.0005, 1.00 x [Formula: see text], 0.0198). Thicker central macula on OCT correlated with lower mfERG amplitudes in rings 4-6 (p = 0.0369, 0.0292, 0.0255). There was no correlation between visual acuity and central macular thickness or foveal hypoplasia score as determined by OCT.Higher amplitude on mfERG correlated with poorer visual acuity in rings 4 and 5 in patients with PAX6 mutations. The slope of the change in amplitude from central to peripheral rings on the mfERG is significantly different in aniridia patients compared to controls, with a slower drop-off of amplitude from center to periphery. Additionally, mfERG in aniridia showed lower amplitudes than controls in rings 1-3. These changes along with the lack of correlation between visual acuity and central macular thickness/OCT score suggest that changes in electrical topography may be important to visual deficits in patients with PAX6 gene mutations.

α2δ-4 is an auxiliary subunit of voltage-gated Cav1.4 L-type channels that regulate the development and mature exocytotic function of the photoreceptor ribbon synapse. In humans, mutations in the CACNA2D4 gene encoding α2δ-4 cause heterogeneous forms of vision impairment in humans, the underlying pathogenic mechanisms of which remain unclear. To investigate the retinal function of α2δ-4, we used genome editing to generate an α2δ-4 knock-out (α2δ-4 KO) mouse. In male and female α2δ-4 KO mice, rod spherules lack ribbons and other synaptic hallmarks early in development. Although the molecular organization of cone synapses is less affected than rod synapses, horizontal and cone bipolar processes extend abnormally in the outer nuclear layer in α2δ-4 KO retina. In reconstructions of α2δ-4 KO cone pedicles by serial block face scanning electron microscopy, ribbons appear normal, except that less than one-third show the expected triadic organization of processes at ribbon sites. The severity of the synaptic defects in α2δ-4 KO mice correlates with a progressive loss of Cav1.4 channels, first in terminals of rods and later cones. Despite the absence of b-waves in electroretinograms, visually guided behavior is evident in α2δ-4 KO mice and better under photopic than scotopic conditions. We conclude that α2δ-4 plays an essential role in maintaining the structural and functional integrity of rod and cone synapses, the disruption of which may contribute to visual impairment in humans with CACNA2D4 mutations.SIGNIFICANCE STATEMENT In the retina, visual information is first communicated by the synapse formed between photoreceptors and second-order neurons. The mechanisms that regulate the structural integrity of this synapse are poorly understood. Here we demonstrate a role for α2δ-4, a subunit of voltage-gated Ca2+ channels, in organizing the structure and function of photoreceptor synapses. We find that presynaptic Ca2+ channels are progressively lost and that rod and cone synapses are disrupted in mice that lack α2δ-4. Our results suggest that alterations in presynaptic Ca2+ signaling and photoreceptor synapse structure may contribute to vision impairment in humans with mutations in the CACNA2D4 gene encoding α2δ-4.

BACKGROUND: Albinism patients have poor visual acuity in addition to hypopigmentation. Their foveal anatomy is abnormal, but correlation with function is incompletely understood. This study correlates retinal electrophysiology, visual acuity and optical coherence tomography (OCT) anatomy in albinism patients and compares with age similar controls. METHODS: Institutional Review Board approval was obtained (IRB# 201408782). Patients were recruited from clinical practice. Inclusion criteria were at least three clinical features of albinism including iris transillumination, nystagmus, fundus hypopigmentation, or foveal hypoplasia on OCT and/or molecular genetic confirmation. Diagnosys (Lowell, Mass) full field ERG (ffERG) and VERIS multifocal ERG (mfERG; Electro-Diagnostic Imaging, Milpitas, California) were obtained using standard International Society for Clinical Electrophysiology of Vision (ISCEV) protocols. The mfERG protocol was a 4 minute 103 hexagon protocol covering approximately 40 degrees in diameter of central retina. Control subjects without albinism were recruited by in-hospital notices and invitations in clinic. OCT central thickness was recorded and an OCT foveal score was calculated. Nonparametric permutation testing was utilized to determine the statistical significance. RESULTS: 16 albinism patients and 19 age-similar controls were recruited. 4 of 16 albinism patients had no nystagmus. 17 non-albinism controls had no ocular disorder other than refractive error. Two controls had infantile nystagmus with normal maculas on OCT. There was no statistically significant difference in mfERG amplitude or latency between albinism patients with or without nystagmus (lowest p=0.68; 0.54 respectively). MFERG: 12 of 16 (75%) albinism patients had average Ring 1 amplitudes within one standard deviation of controls despite having abnormal foveal anatomy on OCT. Patients averaged shorter latencies in Rings 1 and 2 than controls (p = 0.005, p=0.02). Patients averaged higher amplitudes than controls in Rings 4, 5, and 6 (p = 0.03, p = 0.006, p = 0.004). There was no significant correlation between visual acuity (VA) and mfERG amplitudes in any Ring (smallest p = 0.15). FFERG: Patients averaged higher amplitudes on 30 Hz flicker (p = 0.008). In all conditions, albinism patients had higher amplitude a-waves (p ≤ 0.03). B-waves were higher amplitude than controls in light adapted 3.0 (p = 0.03). There was no statistical correlation between ffERG amplitudes and visual acuity (smallest p = 0.45). OCT: In albinism patients, thicker central macula on OCT correlated with lower mfERG amplitudes in all rings except for ring 1 (p < 0.05) and lower ffERG a-wave amplitudes on dark adapted 0.01 (p = 0.003). Macular thickness on OCT did not correlate with visual acuity (p = 0.51); OCT foveal score did (p=0.0004). CONCLUSIONS: Amplitude of mfERG does not correlate with visual acuity in any ring in patients with albinism. The slope of the change in amplitude from central to peripheral rings on the mferg is significantly different in albinism patients versus controls whether or not nystagmus is present. The decreased slope of change in amplitudes from center to periphery of the macula in albinism patients indicates changes in macular topography that are more important to visual deficits than the foveal depression

α2δ-4 is an auxiliary subunit of voltage-gated Cav1.4 L-type channels that regulate the development and mature exocytotic function of the photoreceptor ribbon synapse. In humans, mutations in the CACNA2D4 gene encoding α2δ-4 cause heterogeneous forms of vision impairment in humans, the underlying pathogenic mechanisms of which remain unclear. To investigate the retinal function of α2δ-4, we used genome editing to generate an α2δ-4 knock-out (α2δ-4 KO) mouse. In male and female α2δ-4 KO mice, rod spherules lack ribbons and other synaptic hallmarks early in development. Although the molecular organization of cone synapses is less affected than rod synapses, horizontal and cone bipolar processes extend abnormally in the outer nuclear layer in α2δ-4 KO retina. In reconstructions of α2δ-4 KO cone pedicles by serial block face scanning electron microscopy, ribbons appear normal, except that less than one-third show the expected triadic organization of processes at ribbon sites. The severity of the synaptic defects in α2δ-4 KO mice correlates with a progressive loss of Cav1.4 channels, first in terminals of rods and later cones. Despite the absence of b-waves in electroretinograms, visually guided behavior is evident in α2δ-4 KO mice and better under photopic than scotopic conditions. We conclude that α2δ-4 plays an essential role in maintaining the structural and functional integrity of rod and cone synapses, the disruption of which may contribute to visual impairment in humans with CACNA2D4 mutations.

CLN3-Batten disease is an autosomal-recessive disorder that results from mutations in CLN3. In the vast majority of cases, disease onset occurs in early childhood, is characterized by progressive loss of vision, seizures and a failure in psychomotor development and is universally fatal by the third decade of life. Several mouse models of CLN3 have been developed that have provided insight into the pathological progression of this disease including early glial activation followed by neuronal loss, however, many aspects of the disease are not recapitulated in these mouse models. Porcine models hold the promise of a more accurate disease model given the similarities that pigs and humans share in terms of development, anatomy, and physiology, and in particular, similarities in brain development such as perinatal growth spurt and brain structure. Furthermore, the shared characteristics of the human and porcine visual system make the pig a useful resource for studying macular-associated retinal diseases that are not possible in mice. Additionally, the size of the pig would allow for the use advanced neuroimaging techniques such as MRI, CT and/or PET to model in vivo changes within the CNS longitudinally and track the success of potential therapeutics. Recently, we have developed a novel CLN3∆ex7-8/∆ex7-8 porcine model of CLN3-Batten disease. Here we present initial characterization results showing behavioral, pathological, and visual deficits that mirror changes seen in human patients.

Compartmentalization and polarized protein trafficking are essential for many cellular functions. The photoreceptor outer segment (OS) is a sensory compartment specialized for phototransduction, and it shares many features with primary cilia. As expected, mutations disrupting protein trafficking to cilia often disrupt protein trafficking to the OS and cause photoreceptor degeneration. Bardet-Biedl syndrome (BBS) is one of the ciliopathies associated with defective ciliary trafficking and photoreceptor degeneration. However, precise roles of BBS proteins in photoreceptor cells and the underlying mechanisms of photoreceptor degeneration in BBS are not well understood. Here, we show that accumulation of non-OS proteins in the OS underlies photoreceptor degeneration in BBS. Using a newly developed BBS mouse model [Leucine zipper transcription factor-like 1 (Lztfl1)/Bbs17 mutant], isolated OSs, and quantitative proteomics, we determined 138 proteins that are enriched more than threefold in BBS mutant OS. In contrast, only eight proteins showed a more than threefold reduction. We found striking accumulation of Stx3 and Stxbp1/Munc18-1 and loss of polarized localization of Prom1 within the Lztfl1 and Bbs1 mutant OS. Ultrastructural analysis revealed that large vesicles are formed in the BBS OS, disrupting the lamellar structure of the OS. Our findings suggest that accumulation (and consequent sequestration) of non-OS proteins in the OS is likely the primary cause of photoreceptor degeneration in BBS. Our data also suggest that a major function of BBS proteins in photoreceptors is to transport proteins from the OS to the cell body or to prevent entry of non-OS proteins into the OS.

Purpose To determine which types of pediatric retinal degeneration are associated with inflammatory cells in the anterior vitreous. Design Retrospective, observational study in humans. Methods Retrospective chart review was performed for pediatric patients with suspected retinal degeneration presenting to a single examiner from 2008 to 2013. Age, visual acuity (VA), slit-lamp examination of anterior vitreous (SLAV), and clinical and molecular genetic diagnoses were documented. Anterior vitreous cells were graded clinically with SLAV from rare cells (1–4) to 1+ (5–9), 2+ (10–30), or 3+ (>30). Cells were also counted in magnified slit beam photographs masked to molecular diagnosis when obtainable. Main Outcome Measures Cell counts in SLAV, best-corrected VA, and molecular and clinical diagnoses. Results We evaluated 105 charts, 68 of which (64.8%) included SLAV data. Numerous (1+ or greater) cells were present in 22 of 68 patients (32.4%), whereas 4 of 68 (5.9%) had rare cells and 42 of 68 (61.8%) had no cells. The average age between patients with cells, no cells, and rare cells did not differ significantly ( P = 0.25). The VA averaged 20/124 in patients with cells, 20/143 in patients with no cells, and 20/68 in patients with rare cells ( P = 0.70). The most frequent diagnoses with cells included Bardet Biedl syndrome (BBS), Leber congenital amaurosis (LCA), and retinitis pigmentosa. The most frequent diagnoses without cells included congenital stationary night blindness (CSNB), LCA, Stargardt disease, and blue cone monochromacy. Discussion A nonrandom subset of pediatric retinal degenerations exhibit vitritis. Cells were present in 5 of 5 BBS patients (a progressive degeneration), whereas cells were not detected in any of the 12 patients with CSNB (a stable dysfunction). Conclusions Studying vitritis in pediatric retinal degenerations may reveal whether inflammation accompanies progressive vision loss in certain subtypes. Potentially, inflammation could be treated. In addition, SLAV may aid in clinical diagnosis.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are cation-selective channels present in retina, brain and heart. The activity of HCN channels contributes to signal integration, cell excitability and pacemaker activity. HCN1 channels expressed in photoreceptors participate in keeping light responses transient and are required for normal mesopic vision. The subcellular localization of HCN1 varies among cell types. In photoreceptors HCN1 is concentrated in the inner segments while in other retinal neurons, HCN1 is evenly distributed though the cell. This is in contrast to hippocampal neurons where HCN1 is concentrated in a subset of dendrites. A key regulator of HCN1 trafficking and activity is tetratricopeptide repeat-containing Rab8b interacting protein (TRIP8b). Multiple splice isoforms of TRIP8b are expressed throughout the brain and can differentially regulate the surface expression and activity of HCN1. The purpose of the present study was to determine which isoforms of TRIP8b are expressed in the retina and to test if loss of TRIP8b alters HCN1 expression or trafficking. We found that TRIP8b colocalizes with HCN1 in multiple retina neurons and all major splice isoforms of TRIP8b are expressed in the retina. Photoreceptors express three different isoforms. In TRIP8b knockout mice, the ability of HCN1 to traffic to the surface of retinal neurons is unaffected. However, there is a large decrease in the total amount of HCN1. We conclude that TRIP8b in the retina is needed to achieve maximal expression of HCN1.

Ciliopathies are a group of heterogeneous disorders associated with ciliary dysfunction. Diseases in this group display considerable phenotypic variation within individual syndromes and overlapping phenotypes among clinically distinct disorders. Particularly, mutations in CEP290 cause phenotypically diverse ciliopathies ranging from isolated retinal degeneration, nephronophthisis and Joubert syndrome, to the neonatal lethal Meckel-Gruber syndrome. However, the underlying mechanisms of the variable expressivity in ciliopathies are not well understood. Here, we show that components of the BBSome, a protein complex composed of seven Bardet-Biedl syndrome (BBS) proteins, physically and genetically interact with CEP290 and modulate the expression of disease phenotypes caused by CEP290 mutations. The BBSome binds to the N-terminal region of CEP290 through BBS4 and co-localizes with CEP290 to the transition zone (TZ) of primary cilia and centriolar satellites in ciliated cells, as well as to the connecting cilium in photoreceptor cells. Although CEP290 still localizes to the TZ and connecting cilium in BBSome-depleted cells, its localization to centriolar satellites is disrupted and CEP290 appears to disperse throughout the cytoplasm in BBSome-depleted cells. Genetic interactions were tested using Cep290(rd16)- and Bbs4-null mutant mouse lines. Additional loss of Bbs4 alleles in Cep290(rd16/rd16) mice results in increased body weight and accelerated photoreceptor degeneration compared with mice without Bbs4 mutations. Furthermore, double-heterozygous mice (Cep290(+/rd16);Bbs4(+/-)) have increased body weight compared with single-heterozygous animals. Our data indicate that genetic interactions between BBSome components and CEP290 could underlie the variable expression and overlapping phenotypes of ciliopathies caused by CEP290 mutations.

Gene replacement therapy is currently the best hope for patients with progressive retinal degenerations due to genetic defects; however, at present only one subtype, RPE65-related Leber congenital amaurosis (LCA), has clinical gene therapy results reported.1–3 For patients who may benefit from gene therapy in the future or who exhibit only the earliest signs of retinal degeneration, there is a real need for treatments to slow or stop the progress of disease. In the absence of specific genetic information for a given patient, this could also be a temporizing measure until a genetic diagnosis can be found and a specific therapy devised and administered. An ideal treatment would ameliorate retinal degeneration from several different genetic causes. One group of agents that may have this property is antiapoptotic molecules. Apoptosis is the final pathway in programmed cell death. If this pathway can be aborted or delayed, photoreceptor cells may live and function longer. Tauroursodeoxycholic acid (TUDCA) is the active component in bear bile, which has been used in traditional Chinese medicine for thousands of years. In 2006, Boatright et al.4 showed that systemic TUDCA decreased apoptosis and retinal degeneration in mice with either light-induced retinal damage or genetic retinal degeneration (RP due to a mutation in the Pde6beta gene in the rd10 mouse) at P18 and P30.5,6 TUDCA has also been found to disrupt apoptosis in animal models of neurodegenerative diseases, such as Alzheimer7,8 and Huntington Disease,9,10 and recently was reported to slow retinal degeneration in the Pro23His rat, a model of human autosomal dominant RP.11 We hypothesized that the antiapoptotic effect of TUDCA is also beneficial in treating ciliopathies, a different class of retinal degenerative disorder. Ciliopathies are characterized by having a primary dysfunction of the cilia, usually in several organ systems, including the connecting cilium of the photoreceptor cell. Disease may result from abnormal formation of the cilium, or abnormal transport within it. To test our hypothesis, we treated a mouse model of Bardet-Biedl syndrome (BBS) type 1, an autosomal recessive ciliopathy that causes severe retinal degeneration in humans. This retinal degeneration, which is caused by the most common BBS1 mutation in humans.12 is replicated in homozygous Bbs1M390R/M390R mice. BBS was first described in the 1920s by George Bardet, reporting two French girls with the triad of obesity, polydactyly, and RP.13 In 1922, Arthur Biedl reported similar cases.14 Because the syndrome was reminiscent of earlier cases described in 1866 by Laurence and Moon, in 1925 Solis-Cohen and Weiss coined the term Laurence-Moon-Bardet-Biedl syndrome. Later, Laurence and Moon were removed from the name, as their patients eventually developed paraplegia. To date at least 15 BBS genes have been identified. The protein products of seven of these genes associate in vivo to create the BBSome, a protein complex important to intracellular transport and intraflagellar trafficking.15,16 Three other known BBS proteins associate to form the BBS chaperone complex.17,18 Inactivation of any one of these BBS genes may adversely affect the BBSome and/or chaperone complex and therefore affect transport within the cell, explaining how mutations of many different genes can cause the same unusual findings as those in BBS—postaxial polydactyly, obesity, RP, renal and gonadal anomalies, and, in some cases, developmental delay. How this mistrafficking induces dysfunction and apoptosis of photoreceptor cells in the retina is not known. Since the retinal degeneration in rd10 mice has been reported to be ameliorated by TUDCA,4,5 we replicated the published protocol in this model as a positive control for our intervention, and in addition we observed the rd10 mice longer than previously reported. We also tested the same treatment protocol on rd1 and rd16 mice, which are models of very rapid retinal degeneration analogous to that in autosomal recessive (ar)RP and CEP290-related LCA, respectively, in humans. The purpose of this study was to evaluate the effects of systemic TUDCA on the course of retinal degeneration in Bbs1M390R/M390R, rd10, rd1, and rd16 models by electroretinography (ERG), optical coherence tomography (OCT), and histology. We found that, compared to untreated controls and vehicle injected controls, the severity of retinal degeneration is lessened in two of the models tested. Treatment with TUDCA also attenuated the severity of obesity in Bbs1M390R/M390R mice.

Purpose To study safety and efficacy of subretinal adeno-associated virus (AAV) vector AAV-Bbs1 injection for treatment of a mouse model of Bardet-Biedl syndrome type 1 (BBS1). Methods Constructs containing a wild-type (WT) Bbs1 gene with and without a FLAG tag in AAV2/5 vectors were generated. Viral genomes were delivered by subretinal injection to right eyes and sham injections to left eyes at postnatal day 30 (P30) to P60. Transgene expression and BBSome reconstitution were evaluated by immunohistochemistry and Western blotting following sucrose gradient ultracentrifugation. Retinal function was analyzed by electroretinogram (ERG) and structure by optical coherence tomography (OCT). Histology and immunohistochemistry were performed on selected eyes. Results Expression of FLAG-tagged Bbs1 was demonstrated in photoreceptor cells using antibody directed against the FLAG tag. Coinjection of AAV-GFP demonstrated transduction of 24% to 32% of the retina. Western blotting demonstrated BBS1 protein expression and reconstitution of the BBSome. ERG dark-adapted bright flash b-wave amplitudes were higher in AAV-Bbs1-injected eyes than in sham-injected fellow eyes in more than 50% of 19 animals. Anti-rhodopsin staining demonstrated improved localization of rhodopsin in AAV-Bbs1-treated eyes. WT retinas injected with AAV-Bbs1 with or without a FLAG tag showed outer retinal degeneration on ERG, OCT, and histology. Conclusions In a knock-in model of BBS1, subretinal delivery of AAV-Bbs1 rescues BBSome formation and rhodopsin localization, and shows a trend toward improved ERG. BBS is challenging to treat with gene therapy due to the stoichiometry of the BBSome protein complex and overexpression toxicity.