-
Investigative Ophthalmology & Visual... May 2020To investigate the association between PAX6 genotype and macular morphology in congenital aniridia.
PURPOSE
To investigate the association between PAX6 genotype and macular morphology in congenital aniridia.
METHODS
The study included 37 participants (15 males) with congenital aniridia (aged 10-72 years) and 58 age-matched normal controls (18 males). DNA was isolated from saliva samples. PAX6 exons, intron/exon junctions, and known regulatory regions were amplified in PCR and sequenced. Multiplex ligation-dependent probe amplification (MLPA) was performed to detect larger deletions or duplications in PAX6 or known cis-regulatory regions. Spectral-domain optical coherence tomography images were acquired and segmented semiautomatically. Mean thicknesses were calculated for inner and outer retinal layers within the macula along nasal and temporal meridians.
RESULTS
Mutations in PAX6 or regulatory regions were found in 97% of the participants with aniridia. Foveal hypoplasia was observed in all who had a mutation within the PAX6 gene. Aniridic eyes had thinner outer retinal layers than controls, but with large between-individual variation (mean ± SD, 156.3 ± 32.3 µm vs 210.8 ± 12.3 µm, P < 0.001). Parafoveal and perifoveal inner and outer retinal layers were thinner in aniridia. Participants with mutations in noncoding PAX6 regions had thicker foveal outer retinal layers than those with mutations in the PAX6 coding regions (P = 0.04) and showed signs of postnatal development and maturation. Mutations outside the PAX6 gene were associated with the mildest retinal phenotypes.
CONCLUSIONS
PAX6 mutations are associated with significant thinning of macular inner and outer retinal layers, consistent with misdirected retinal development resulting in abnormal foveal formation and reduced number of neurons in the macula, with mutations in PAX6 coding regions giving the worst outcome.
Topics: Adolescent; Adult; Aged; Aniridia; Case-Control Studies; Child; Female; Fovea Centralis; Genotype; Humans; Male; Middle Aged; Mutation; Open Reading Frames; PAX6 Transcription Factor; Phenotype; Retina; Tomography, Optical Coherence; Young Adult
PubMed: 32396632
DOI: 10.1167/iovs.61.5.14 -
Biology Dec 2023Limbal stem cell deficiency (LSCD) is a pathologic condition caused by the dysfunction and destruction of stem cells, stem cell precursors and limbal cell niche in the... (Review)
Review
Limbal stem cell deficiency (LSCD) is a pathologic condition caused by the dysfunction and destruction of stem cells, stem cell precursors and limbal cell niche in the corneal epithelium, leading to severe conjunctivalization of the cornea. Etiologies for LSCD span from congenital (aniridia), traumatic (chemical or thermal injuries), autoimmune (Stevens-Johnson syndrome) and iatrogenic disease to contact lens (CL) wear. Of these, CL wear is the least understood and is often a subclinical cause of LSCD. Even with recent advances in LSCD research, limitations persist in establishing the pathogenesis and treatment guidelines for CL-induced LSCD. A literature search was conducted to include original articles containing patients with CL-induced LSCD. This review will critically discuss the complex pathophysiology behind CL-induced LSCD, the underlying risk factors and epidemiology of the disease as well as methods to obtain a diagnosis. Various treatment options will be reviewed based on proposed treatment strategies.
PubMed: 38132316
DOI: 10.3390/biology12121490 -
Case Reports in Ophthalmology 2021We report a novel approach for managing traumatic total aniridia associated with secondary glaucoma. A 65-year-old male with symptoms of blurred vision, glare, and...
We report a novel approach for managing traumatic total aniridia associated with secondary glaucoma. A 65-year-old male with symptoms of blurred vision, glare, and photophobia was managed in a district general hospital for post-traumatic aniridia associated with secondary glaucoma affecting the right eye. The patient previously suffered blunt ocular injury associated with rhegmatogenous retinal detachment, which was treated with pars plana vitrectomy and silicone oil (SO) tamponade and subsequent removal of SO (ROSO). Combined trabeculectomy and implantation of a foldable prosthetic iris (Reper NN Ltd) successfully addressed the dual pathology of aniridia and secondary glaucoma. In summary, the utilization of the trabeculectomy fistula can serve as the implant insertion site, which minimizes the requirement for additional incisions.
PubMed: 33976683
DOI: 10.1159/000511099 -
Genes Sep 2021Monogenic syndromic disorders frequently feature ocular manifestations, one of which is glaucoma. In many cases, glaucoma in children may go undetected, especially in... (Review)
Review
Monogenic syndromic disorders frequently feature ocular manifestations, one of which is glaucoma. In many cases, glaucoma in children may go undetected, especially in those that have other severe systemic conditions that affect other parts of the eye and the body. Similarly, glaucoma may be the first presenting sign of a systemic syndrome. Awareness of syndromes associated with glaucoma is thus critical both for medical geneticists and ophthalmologists. In this review, we highlight six categories of disorders that feature glaucoma and other ocular or systemic manifestations: anterior segment dysgenesis syndromes, aniridia, metabolic disorders, collagen/vascular disorders, immunogenetic disorders, and nanophthalmos. The genetics, ocular and systemic features, and current and future treatment strategies are discussed. Findings from rare diseases also uncover important genes and pathways that may be involved in more common forms of glaucoma, and potential novel therapeutic strategies to target these pathways.
Topics: Aniridia; Collagen Diseases; Eye Abnormalities; Eye Diseases, Hereditary; Glaucoma; Glaucoma, Angle-Closure; Humans; Hyperopia; Immune System Diseases; Metabolic Diseases; Microphthalmos; Syndrome; Vascular Diseases
PubMed: 34573386
DOI: 10.3390/genes12091403 -
Molecular Vision 2018Aniridia is a congenital disorder caused by variants in the gene. In this study, we assessed the involvement of in patients with aniridia from Australasia and...
PURPOSE
Aniridia is a congenital disorder caused by variants in the gene. In this study, we assessed the involvement of in patients with aniridia from Australasia and Southeast Asia.
METHODS
Twenty-nine individuals with aniridia from 18 families originating from Australia, New Caledonia, Cambodia, Sri Lanka, and Bhutan were included. The gene was investigated for sequence variants and analyzed for deletions with multiplex ligation-dependent probe amplification.
RESULTS
We identified 11 sequence variants and six chromosomal deletions, including one in mosaic. Four deleterious sequence variants were novel: p.(Pro81HisfsTer12), p.(Gln274Ter), p.(Ile29Thr), and p.(Met1?). Ocular complications were associated with a progressive loss of visual function as shown by a visual acuity ≤ 1.00 logMAR reported in 65% of eyes. The prevalence of keratopathy was statistically significantly higher in the Australasian cohort (78.6%) compared with the Southeast Asian cohort (9.1%, p=0.002). Variants resulting in protein truncating codons displayed limited genotype-phenotype correlations compared with other variants.
CONCLUSIONS
variants and deletions were identified in 94% of patients with aniridia from Australasia and Southeast Asia. This study is the first report of aniridia and variations in in individuals from Cambodia, Sri Lanka, Bhutan, and New Caledonia, and the largest cohort from Australia.
Topics: Adolescent; Adult; Aniridia; Asia, Southeastern; Australasia; Base Sequence; Child; Chromosome Deletion; Cohort Studies; Exons; Female; Gene Expression; Genetic Association Studies; Genotype; Humans; Inheritance Patterns; Introns; Male; Middle Aged; Mosaicism; PAX6 Transcription Factor; Pedigree; Phenotype
PubMed: 29618921
DOI: No ID Found -
Investigative Ophthalmology & Visual... Oct 2019To investigate fundus autofluorescence (FAF) and other fundus manifestations in congenital aniridia.
PURPOSE
To investigate fundus autofluorescence (FAF) and other fundus manifestations in congenital aniridia.
METHODS
Fourteen patients with congenital aniridia and 14 age- and sex-matched healthy controls were examined. FAF images were obtained with an ultra-widefield scanning laser ophthalmoscope. FAF intensity was quantified in the macular fovea and in a macular ring surrounding fovea and related to an internal reference within each image. All aniridia patients underwent an ophthalmologic examination, including optical coherence tomography and slit-lamp biomicroscopy.
RESULTS
Mean age was 28.4 ± 15.0 years in both the aniridia and control groups. Fovea could be defined by subjective assessment of FAF images in three aniridia patients (21.4%) and in all controls (P = 0.001). Mean ratio between FAF intensity in the macular ring and fovea was 1.01 ± 0.15 in aniridia versus 1.18 ± 0.09 in controls (P = 0.034). In aniridia, presence of foveal hypoplasia evaluated by biomicroscopy correlated with lack of foveal appearance by subjective analyses of FAF images (P = 0.031) and observation of nystagmus (P = 0.009).
CONCLUSIONS
Aniridia patients present a lower ratio between FAF intensity in the peripheral and central macula than do healthy individuals. Both subjective and objective analyses of FAF images are useful tools in evaluation of foveal hypoplasia in aniridia.
Topics: Adolescent; Adult; Aniridia; Case-Control Studies; Child; Female; Fluorescein Angiography; Humans; Male; Middle Aged; Ophthalmoscopy; Prospective Studies; Tomography, Optical Coherence; Young Adult
PubMed: 31574536
DOI: 10.1167/iovs.19-26994 -
Human Mutation Jul 2021Microphthalmia, coloboma, and aniridia are congenital ocular phenotypes with a strong genetic component but often unknown cause. We present a likely causative novel...
Microphthalmia, coloboma, and aniridia are congenital ocular phenotypes with a strong genetic component but often unknown cause. We present a likely causative novel variant in MAB21L1, c.152G>T p.(Arg51Leu), in two family members with microphthalmia and aniridia, as well as novel or rare compound heterozygous variants of uncertain significance, c.184C>T p.(Arg62Cys)/c.-68T>C, and c.658G>C p.(Gly220Arg)/c.*529A>G, in two additional probands with microphthalmia, coloboma and/or cataracts. All variants were predicted as damaging by in silico programs. In vitro studies of coding variants revealed normal subcellular localization but variable stability for the corresponding mutant proteins. In vivo complementation assays using the zebrafish mab21l2 loss-of-function line demonstrated that though overexpression of wild-type MAB21L1 messenger RNA (mRNA) compensated for the loss of mab21l2, none of the coding variant mRNAs produced a statistically significant rescue, with p.(Arg51Leu) showing the highest degree of functional deficiency. Dominant variants in a close homolog of MAB21L1, MAB21L2, have been associated with microphthalmia and/or coloboma and repeatedly involved the same Arg51 residue, further supporting its pathogenicity. The possible role of p.(Arg62Cys) and p.(Gly220Arg) in microphthalmia is similarly supported by the observed functional defects, with or without an additional impact from noncoding MAB21L1 variants identified in each patient. This study suggests a broader spectrum of MAB21L1-associated disease.
Topics: Animals; Aniridia; Coloboma; Eye Proteins; Homeodomain Proteins; Humans; Intracellular Signaling Peptides and Proteins; Microphthalmos; Zebrafish; Zebrafish Proteins
PubMed: 33973683
DOI: 10.1002/humu.24218 -
PloS One 2018To study structural changes in naïve and surgically treated corneas of aniridia patients with advanced aniridia-related keratopathy (ARK).
BACKGROUND
To study structural changes in naïve and surgically treated corneas of aniridia patients with advanced aniridia-related keratopathy (ARK).
METHODS AND FINDINGS
Two naïve corneal buttons from patients with advanced ARK submitted to penetrating keratoplasty for the first time, one corneal button from an ARK patient that had undergone a keratolimbal allograft (KLAL), two corneal buttons from ARK patients who had previously undergone centered or decentered transplantation and were now retransplanted and two adult healthy donor control corneas were processed for immunohistochemistry. Antibodies against extracellular matrix components in the stroma and in the epithelial basement membrane (collagen I and IV, collagen receptor α11 integrin and laminin α3 chain), markers of fibrosis, wound healing and vascularization (fibronectin, tenascin-C, vimentin, α-SMA and caveolin-1), cell division (Ki-67) and macrophages (CD68) were used. Naïve ARK, KLAL ARK corneas and transplanted corneal buttons presented similar histopathological changes with irregular epithelium and disruption or absence of epithelial basal membrane. There was a loss of the orderly pattern of collagen lamellae and absence of collagen I in all ARK corneas. Vascularization was revealed by the presence of caveolin-1 and collagen IV in the pannus of all ARK aniridia corneas. The changes observed in decentered and centered transplants were analogous.
CONCLUSIONS
Given the similar pathological features of all cases, conditions inherent to the host seem to play an important role on the pathophysiology of the ARK in the long run.
Topics: Adult; Aged; Aniridia; Basement Membrane; Collagen Type I; Collagen Type IV; Cornea; Corneal Transplantation; Female; Fibronectins; Humans; Ki-67 Antigen; Laminin; Male; Tenascin; Transplantation, Homologous
PubMed: 29889891
DOI: 10.1371/journal.pone.0198822 -
Ophthalmology and Therapy Aug 2023Aniridia is a rare congenital vision-loss disease caused by heterozygous variants in the PAX6 gene. There is no vision-saving therapy, but one exciting approach is to...
INTRODUCTION
Aniridia is a rare congenital vision-loss disease caused by heterozygous variants in the PAX6 gene. There is no vision-saving therapy, but one exciting approach is to use CRISPR/Cas9 to permanently correct the causal genomic variants. Preclinical studies to develop such a therapy in animal models face the challenge of showing efficacy when binding human DNA. Thus, we hypothesized that a CRISPR gene therapy can be developed and optimized in humanized mouse embryonic stem cells (ESCs) that will be able to distinguish between an aniridia patient variant and nonvariant chromosome and lay the foundation for human therapy.
METHODS
To answer the challenge of binding human DNA, we proposed the "CRISPR Humanized Minimally Mouse Models" (CHuMMMs) strategy. Thus, we minimally humanized Pax6 exon 9, the location of the most common aniridia variant c.718C > T. We generated and characterized a nonvariant CHuMMMs mouse, and a CHuMMMs cell-based disease model, in which we tested five CRISPR enzymes for therapeutic efficacy. We then delivered the therapy via lipid nanoparticles (LNPs) to alter a second variant in ex vivo cortical primary neurons.
RESULTS
We successfully established a nonvariant CHuMMMs mouse and three novel CHuMMMs aniridia cell lines. We showed that humanization did not disrupt Pax6 function in vivo, as the mouse showed no ocular phenotype. We developed and optimized a CRISPR therapeutic strategy for aniridia in the in vitro system, and found that the base editor, ABE8e, had the highest correction of the patient variant at 76.8%. In the ex vivo system, the LNP-encapsulated ABE8e ribonucleoprotein (RNP) complex altered the second patient variant and rescued 24.8% Pax6 protein expression.
CONCLUSION
We demonstrated the usefulness of the CHuMMMs approach, and showed the first genomic editing by ABE8e encapsulated as an LNP-RNP. Furthermore, we laid the foundation for translation of the proposed CRISPR therapy to preclinical mouse studies and eventually patients with aniridia.
PubMed: 37210469
DOI: 10.1007/s40123-023-00729-6 -
Human Genomics Jun 2023Haploinsufficiency of the transcription factor PAX6 is the main cause of congenital aniridia, a genetic disorder characterized by iris and foveal hypoplasia. 11p13...
BACKGROUND
Haploinsufficiency of the transcription factor PAX6 is the main cause of congenital aniridia, a genetic disorder characterized by iris and foveal hypoplasia. 11p13 microdeletions altering PAX6 or its downstream regulatory region (DRR) are present in about 25% of patients; however, only a few complex rearrangements have been described to date. Here, we performed nanopore-based whole-genome sequencing to assess the presence of cryptic structural variants (SVs) on the only two unsolved "PAX6-negative" cases from a cohort of 110 patients with congenital aniridia after unsuccessfully short-read sequencing approaches.
RESULTS
Long-read sequencing (LRS) unveiled balanced chromosomal rearrangements affecting the PAX6 locus at 11p13 in these two patients and allowed nucleotide-level breakpoint analysis. First, we identified a cryptic 4.9 Mb de novo inversion disrupting intron 7 of PAX6, further verified by targeted polymerase chain reaction amplification and sequencing and FISH-based cytogenetic analysis. Furthermore, LRS was decisive in correctly mapping a t(6;11) balanced translocation cytogenetically detected in a second proband with congenital aniridia and considered non-causal 15 years ago. LRS resolved that the breakpoint on chromosome 11 was indeed located at 11p13, disrupting the DNase I hypersensitive site 2 enhancer within the DRR of PAX6, 161 Kb from the causal gene. Patient-derived RNA expression analysis demonstrated PAX6 haploinsufficiency, thus supporting that the 11p13 breakpoint led to a positional effect by cleaving crucial enhancers for PAX6 transactivation. LRS analysis was also critical for mapping the exact breakpoint on chromosome 6 to the highly repetitive centromeric region at 6p11.1.
CONCLUSIONS
In both cases, the LRS-based identified SVs have been deemed the hidden pathogenic cause of congenital aniridia. Our study underscores the limitations of traditional short-read sequencing in uncovering pathogenic SVs affecting low-complexity regions of the genome and the value of LRS in providing insight into hidden sources of variation in rare genetic diseases.
Topics: Humans; Paired Box Transcription Factors; Homeodomain Proteins; Repressor Proteins; Aniridia; Chromosome Inversion; Mutation
PubMed: 37269011
DOI: 10.1186/s40246-023-00490-8