IMPORTANCE Mutations in genes traditionally associated with syndromic retinal disease are increasingly found to cause nonsyndromic inherited retinal degenerations. Mutations in CLN3 are classically associated with juvenile neuronal ceroid lipofuscinosis, a rare neurodegenerative disease with early retinal degeneration and progressive neurologic deterioration, but have recently also been identified in patients with nonsyndromic inherited retinal degenerations. To our knowledge, detailed clinical characterization of such cases has yet to be reported.OBJECTIVE To provide detailed clinical, electrophysiologic, structural, and molecular genetic findings in nonsyndromic inherited retinal degenerations associated with CLN3 mutations. DESIGN, SETTING, AND PARTICIPANTSA multi-institutional case series of 10 patients who presented with isolated nonsyndromic retinal disease and mutations in CLN3. Patient ages ranged from 16 to 70 years; duration of follow-up ranged from 3 to 29 years. MAIN OUTCOMES AND MEASURESLongitudinal clinical evaluation, including full ophthalmic examination, multimodal retinal imaging, perimetry, and electrophysiology. Molecular analyses were performed using whole-genome sequencing or whole-exome sequencing. Electron microscopy studies of peripheral lymphocytes and CLN3 transcript analysis with polymerase chain reaction amplification were performed in a subset of patients.RESULTS There were 7 females and 3 males in this case series, with a mean (range) age at last review of 37.1 (16-70) years. Of the 10 patients, 4 had a progressive late-onset rod-cone dystrophy, with a mean (range) age at onset of 29.7 (20-40) years, and 6 had an earlier onset rod-cone dystrophy, with a mean (range) age at onset of 12.1 (7-17) years. Ophthalmoscopic examination features included macular edema, mild intraretinal pigment migration, and widespread atrophy in advanced disease. Optical coherence tomography imaging demonstrated significant photoreceptor loss except in patients with late-onset disease who had a focal preservation of the ellipsoid zone and outer nuclear layer in the fovea. Electroretinography revealed a rod-cone pattern of dysfunction in 6 patients and were completely undetectable in 2 patients. Six novel CLN3 variants were identified in molecular analyses.CONCLUSIONS AND RELEVANCE This report describes detailed clinical, imaging, and genetic features of CLN3-associated nonsyndromic retinal degeneration. The age at onset and natural progression of retinal disease differs greatly between syndromic and nonsyndromic CLN3 disease, which may be associated with genotypic differences.

IMPORTANCE Knobloch syndrome is a rare, recessively inherited disorder classically characterized by high myopia, retinal detachment, and occipital encephalocele, but it is now known to have an increasingly variable phenotype. There is a lack of reported electrophysiologic data, and some key clinical features have yet to be described.OBJECTIVE To expand on current clinical, electrophysiologic, and molecular genetic findings in Knobloch syndrome. DESIGN, SETTING, AND PARTICIPANTSTwelve patients from 7 families underwent full ophthalmic examination and retinal imaging. Further investigations included electroretinography and neuroradiologic imaging. Bidirectional Sanger sequencing of COL18A1 was performed with segregation on available relatives. The study was conducted from July 4, 2013, to October 5, 2015. Data analysis was performed from May 20, 2014, to November 3, 2015. MAIN OUTCOMES AND MEASURESResults of ophthalmic and neuroradiologic assessment and sequence analysis of COL18A1. RESULTSOf the 12 patients (6 males; mean age at last review, 16 years [range, 2-38 years]), all had high myopia in at least 1 eye and severely reduced vision. A sibling pair had unilateral high myopia in their right eyes and near emmetropia in their left eyes from infancy. Anterior segment abnormalities included absent iris crypts, iris transillumination, lens subluxation, and cataract. Two patients with iris transillumination had glaucoma. Fundus characteristics included abnormal collapsed vitreous, macular atrophy, and a tesselated fundus. Five patients had previous retinal detachment. Electroretinography revealed a cone-rod pattern of dysfunction in 8 patients, was severely reduced or undetectable in 2 patients, and demonstrated cone-rod dysfunction in 1 eye with undetectable responses in the other eye in 2 patients. Radiologic imaging demonstrated occipital encephalocele or meningocele in 3 patients, occipital skull defects in 4 patients, minor occipital changes in 2 patients, and no abnormalities in 2 patients. Cutaneous scalp changes were present in 5 patients. Systemic associations were identified in 8 patients, including learning difficulties, epilepsy, and congenital renal abnormalities. Biallelic mutations including 2 likely novel mutations in COL18A1, were identified in 6 families that were consistent with autosomal recessive inheritance with a single mutation identified in a family with 2 affected children. CONCLUSIONS AND RELEVANCEThis report describes new features in patients with Knobloch syndrome, including pigment dispersion syndrome and glaucoma as well as cone-rod dysfunction on electroretinography. Two patients had normal neuroradiologic findings, emphasizing that some affected individuals have isolated ocular disease. Awareness of the ocular phenotype may aid early diagnosis, appropriate genetic counseling, and monitoring for potential complications.

Citation: Khan KN, El-Asrag ME, Ku CA, et al.; for NIHR BioResource-Rare Diseases and UK Inherited Retinal Disease Consortium. Specific alleles of CLN7/ MFSD8, a protein that localizes to photoreceptor synaptic terminals, cause a spectrum of nonsyndromic retinal dystrophy. Invest Ophthalmol Vis Sci. 2017;58:290658: -291458: . DOI:10.1167 PURPOSE. Recessive mutations in CLN7/MFSD8 usually cause variant late-infantile onset neuronal ceroid lipofuscinosis (vLINCL), a poorly understood neurodegenerative condition, though mutations may also cause nonsyndromic maculopathy. A series of 12 patients with nonsyndromic retinopathy due to novel CLN7/MFSD8 mutation combinations were investigated in this study. METHODS.Affected patients and their family members were recruited in ophthalmic clinics at each center where they were examined by retinal imaging and detailed electrophysiology. Whole exome or genome next generation sequencing was performed on genomic DNA from at least one affected family member. Immunofluorescence confocal microscopy of murine retina cross-sections were used to localize the protein. RESULTS.Compound heterozygous alleles were identified in six cases, one of which was always p.Glu336Gln. Such combinations resulted in isolated macular disease. Six further cases were homozygous for the variant p.Met454Thr, identified as a founder mutation of South Asian origin. Those patients had widespread generalized retinal disease, characterized by electroretinography as a rod-cone dystrophy with severe macular involvement. In addition, the photopic single flash electroretinograms demonstrated a reduced b-to a-wave amplitude ratio, suggesting dysfunction occurring after phototransduction. Immunohistology identified MFSD8 in the outer plexiform layer of the retina, a site rich in photoreceptor synapses.CONCLUSIONS. This study highlights a hierarchy of MFSD8 variant severity, predicting three consequences of mutation: (1) nonsyndromic localized maculopathy, (2) nonsyndromic widespread retinopathy, or (3) syndromic neurological disease. The data also shed light on the underlying pathogenesis by implicating the photoreceptor synaptic terminals as the major site of retinal disease.

A 5- or 1-day treatment with 50 mg/kg sarpogrelate can completely protect the retina of BALB/c mice from light-induced retinopathy. Partial protection can be achieved with lower doses starting at 15 mg/kg and protection increases in a dose-dependent manner. Treatment with low doses of sarpogrelate and 8-OH-DPAT elicits an additive effect that results in full protection of retinal morphology.

Defects in the photoreceptor-specific gene aryl hydrocarbon receptor interacting protein-like 1 (Aipl1) are associated with Leber congenital amaurosis (LCA), a childhood blinding disease with early-onset retinal degeneration and vision loss. Furthermore, Aipl1 defects are characterized at the most severe end of the LCA spectrum. The rapid photoreceptor degeneration and vision loss observed in the LCA patient population are mimicked in a mouse model lacking AIPL1. Using this model, we evaluated if gene replacement therapy using recent advancements in adeno-associated viral vectors (AAV) provides advantages in preventing rapid retinal degeneration. Specifically, we demonstrated that the novel self-complementary Y733F capsid mutant AAV2/8 (sc-Y733F-AAV) provided greater preservation of photoreceptors and functional vision in Aipl1 null mice compared with single-stranded AAV2/8. The benefits of sc-Y733F-AAV were evident following viral administration during the active phase of retinal degeneration, where only sc-Y733F-AAV treatment achieved functional vision rescue. This result was likely due to higher and earlier onset of Aipl1 expression. Based on our studies, we conclude that the sc-Y733F-AAV2/8 viral vector, to date, achieves the best rescue for rapid retinal degeneration in Aipl1 null mice. Our results provide important considerations for viral vectors to be used in future gene therapy clinical trials targeting a wider severity spectrum of inherited retinal dystrophies.