Absent meibomian glands and cone dystrophy in ADULT syndrome: identification by whole exome sequencing of pathogenic variants in two causal genes TP63 and CNGB3.

BACKGROUND: Ectrodactyly is a rare congenital limb malformation characterized by a deep median cleft of the hand and/or foot due to the absence of central rays. It could be isolated or depicts a part of diverse syndromic forms. Heterozygous pathogenic variants in the TP63 gene are responsible for at least four rare syndromic human disorders associated with ectrodactyly. Among them, ADULT (Acro-Dermato-Ungual-Lacrimal-Tooth) syndrome is characterized by ectodermal dysplasia, excessive freckling, nail dysplasia, and lacrimal duct obstruction, in addition to ectrodactyly and/or syndactyly. Ophthalmic findings are very common in TP63-related disorders, consisting mainly of lacrimal duct hypoplasia. Absent meibomian glands have also been well documented in EEC3 (Ectrodactyly Ectodermal dysplasia Cleft lip/palate) syndrome but not in ADULT syndrome. METHODS: We report a case of syndromic ectrodactyly consistent with ADULT syndrome, with an additional ophthalmic manifestation of agenesis of meibomian glands. The proband, as well as her elder sister, presented with congenital cone dystrophy.The molecular investigation was performed in the proband using Whole Exome Sequencing. Family segregation of the identified variants was confirmed by Sanger sequencing. RESULTS: Two clinically relevant variants were found in the proband: the novel de novo heterozygous missense c.931A > G (p.Ser311Gly) in the TP63 gene classified as pathogenic, and the homozygous nonsense pathogenic c.1810C > T (p.Arg604Ter) in the CNGB3 gene. The same homozygous CNGB3 variation was also found in the sister, explaining the cone dystrophy in both cases. CONCLUSIONS: Whole Exome Sequencing allowed dual molecular diagnoses: de novo TP63-related syndromic ectrodactyly and familial CNGB3-related congenital cone dystrophy.

Seroreactivity against retinal proteins in a case of POC1B gene associated cone dystrophy with normal funduscopic appearance: a systematic approach to diagnosis.

PURPOSE: To report a case of cone dystrophy, associated with autosomal recessive homozygote POC1B gene variant, mimicking autoimmune retinopathy. CASE: A 45-year-old female presented with a complaint of decreased vision in both eyes. Her best corrected visual acuity was 20/32 in the right eye and 20/50 in the left eye. Anterior segment and dilated fundus examinations were unremarkable. Spectral domain optical coherence tomography showed a subfoveal blurred dome-shaped ellipsoid zone and an extinguished interdigitation zone affecting the entire macula. Full field electroretinography revealed reduced cone responses. The differential diagnosis included inflammatory chorioretinopathies, autoimmune retinopathies (paraneoplastic or nonparaneoplastic), and hereditary retinal dystrophies. No remarkable finding was observed on combined fluorescein and indocyanine green angiographies. Paraneoplastic autoimmune antibody panel revealed nothing; however, aldolase, enolase, pyruvate kinase M2, and glyceraldehyde-3-phosphate dehydrogenase antibodies were positive on autoimmune retinopathy panel. To exclude hereditary retinal dystrophies, whole-exome sequencing (WES) was applied. WES identified an autosomal recessive homozygote POC1B gene variant (c.680A>G, p.His227Arg). Cone dystrophy diagnosis was given. CONCLUSION: Cone dystrophy associated with POC1B gene variant may present without visible fundus abnormalities. It should be kept in mind that retinal autoantibodies may be positive in such a hereditary dystrophy case due to long-term exposure of the immune system to self-antigens. Therefore, autoimmune retinopathy is a diagnosis of exclusion and should not be diagnosed until all other causes, including hereditary dystrophies, have been ruled out.

Characterization of a novel non-canonical splice site variant (c.886-5T>A) in NBAS and description of the associated phenotype.

BACKGROUND: Biallelic pathogenic variants in the neuroblastoma-amplified sequence (NBAS) gene manifest in a broad spectrum of disorders, including, but not limited to recurrent acute liver failure, skeletal dysmorphism, susceptibility to infections, and SOPH syndrome with its cardinal symptoms of short stature, optic atrophy, and Pelger-Huët anomaly. We aimed to present clinical and genetic characteristics of two sisters (20 and 15 years old) who were diagnosed with optic atrophy and cone dystrophy in childhood. Genome sequencing revealed two novel variants in NBAS in compound heterozygous state in both sisters, namely a 1-bp deletion predicted to result in a premature termination codon (c.5104del; p.(Met1702*)), and a non-canonical splice site variant of unclear significance (c.886-5T>A; p.?). RESULTS: Clinical examination and history revealed cone dystrophy, optic atrophy, and Pelger-Huët anomaly, but no short stature, recurrent acute liver failure, or susceptibility to infections. RNA analysis revealed that the c.886-5T>A variant results in two aberrant transcripts that are predicted to lead to in frame amino acid changes in the ß-propeller region of the protein. CONCLUSION: We hypothesize that the phenotype of our subjects, which appears to be at the end of the spectrum of NBAS-related disorders, could be explained by residual protein function mediated by the non-canonical splice site variant c.886-5T>A. Our study contributes to the existing knowledge on the genotypic and phenotypic spectrum of NBAS-related disorders.

Yap haploinsufficiency leads to Müller cell dysfunction and late-onset cone dystrophy.

Hippo signalling regulates eye growth during embryogenesis through its effectors YAP and TAZ. Taking advantage of a Yap heterozygous mouse line, we here sought to examine its function in adult neural retina, where YAP expression is restricted to Müller glia. We first discovered an unexpected temporal dynamic of gene compensation. At postnatal stages, Taz upregulation occurs, leading to a gain of function-like phenotype characterised by EGFR signalling potentiation and delayed cell-cycle exit of retinal progenitors. In contrast, Yap+/- adult retinas no longer exhibit TAZ-dependent dosage compensation. In this context, Yap haploinsufficiency in aged individuals results in Müller glia dysfunction, late-onset cone degeneration, and reduced cone-mediated visual response. Alteration of glial homeostasis and altered patterns of cone opsins were also observed in Müller cell-specific conditional Yap-knockout aged mice. Together, this study highlights a novel YAP function in Müller cells for the maintenance of retinal tissue homeostasis and the preservation of cone integrity. It also suggests that YAP haploinsufficiency should be considered and explored as a cause of cone dystrophies in human.

[Progressive loss of vision in cone dystrophy. Search for evidence with macular OCT and multifocal ERG]. / Progressive Visusminderung bei Zapfendystrophie. Spurensuche im Makula-OCT und Multifokal-ERG.

A 53-year-old patient consulted our practice clinic complaining of progressive visual loss, increased glare sensitivity and color sense disorder. Extensive diagnostic investigation, including multifocal ERG (mfERG) and macular thickness map with the help of optical coherence tomography (OCT), supported the suspected diagnosis of a cone dystrophy. There are, however, no established therapeutic options. A diagnostic confirmation by means of molecular genetics was not successful.

Morphological and functional findings in Alström syndrome: a study of two families / Achados morfológicos e funcionais na síndrome de Alström: um estudo de duas famílias

ABSTRACT Alström syndrome is a rare disorder characterized by mutations to the ALMS1 gene and clinical findings of childhood obesity, diabetes mellitus, dilated cardiomyopathy, sensorineural hearing loss, and progressive cone-rod dystrophy, which may result in blindness. Ocular manifestations occur in the first decade of life with nystagmus, blepharospasm, and photophobia leading to progressive and severe reductions in visual acuity. This study describes the retinal structure and functional aspects of four patients (8 eyes) from two different families as determined by optical coherence tomography (OCT), fundus autofluorescence, and full-field electroretinography. There was a correlation between morphological and functional findings, evidenced by typical funduscopic changes of retinal dystrophy in spectral domain-OCT and electrophysiological analyses. Foveal characteristics include a single layer of undifferentiated photoreceptors with retinal disorganization mainly from external segments, in agreement with previous reports in the literature. Fundus autofluorescence showed areas of hyperautofluorescence interspersed by hypoautofluorescence dots suggesting, respectively, involvement and atrophy of retinal pigmented epithelial cells in the macular zone. Electroretinographic analyses showed early dysfunction of the cones followed by rapid rod deterioration.

RESUMO A síndrome de Alström é uma doença rara caracterizada por mutações no gene AMLS 1 e achados clínicos de obesidade infantil, diabetes mellitus, cardiomiopatia dilatada, surdez neurossensorial e distrofia de cones e bastonetes progressiva, que podem resultar em cegueira. Manifestações oftalmológicas ocorrem na primeira década de vida com nistagmo, blefaroespasmo e fotofobia, levando a reduções progressivas e graves na acuidade visual. Este estudo descreve a estrutura da retina e os aspectos funcionais de quatro pacientes (oito olhos) de duas famílias dis tintas, conforme determinado por tomografia de coerência óptica, autoflourescência de fundo de olho e eletrorretinograma de campo total. Houve correlação entre os achados morfológicos e funcionais evidenciados por alterações fundoscópicas típicas da distrofia retiniana no domínio espectral-OCT e análises eletrofisiológicas. As características foveais incluem uma única camada de fotorreceptores indiferenciados com desorganização retiniana principalmente nos segmentos externos, de acordo com relatos prévios da literatura. A autofluorescência de fundo mostrou áreas de hiperautofluorescência, sugerindo, respectivamente, envolvimento e atrofia das células do epitélio pigmentar da retina na região macular. Análises eletrorretinográficas mostram disfunção precoce de cones, seguida de rápida deteriorização da haste.