BACKGROUND: According to previous reports, PAX6-associated foveal hypoplasia (FH) could usually be accompanied by various anterior segment anomalies including variable iris changes. This study aims to exhibit unusual phenotypes of a novel missense variant of PAX6 from a Chinese pedigree.
METHODS: Ophthalmic examinations including slit-lamp biomicroscopy, gonioscopy, ophthalmic ultrasound, ultrasonic biomicroscopy, optical coherence tomography, wide-field fundus imaging, and visual field test were performed to evaluate the clinical manifestations. Whole-exome sequencing (WES) and bioinformatics analysis were conducted in eight members from this pedigree to identify the causative mutation.
RESULTS: WES revealed a novel heterozygous substitution of PAX6 (NM_000280.5:c.157G > A, p.(Val53Met) (chr11:31823309 C > T, hg19)), which cosegregated with the phenotype of this pedigree. All the three patients (a pair of fraternal twins and their mother) exhibited bilateral FH and anterior segment dysgenesis (ASD) including microcornea, sclerocornea, obvious symmetrical corectopia, iris stromal dysplasia, goniodysgenesis, and abnormal distribution of fundus blood vessels. The girl of the fraternal twins also demonstrated bilateral temporal deviation of lenses and abnormal tissue membrane connecting anterior chamber angle and lens anterior capsule in the right eye. The mother additionally showed apparent cataract bilaterally and cupping of the optic disc in her left eye.
CONCLUSIONS: A novel missense variant in PAX6 gene was detected in a Chinese pedigree demonstrating bilateral FH and ASD. It is really distinctive that the ASD involves almost all parts of the anterior segment, and bilateral symmetrical corectopia is the most perceptible sign. This study expands the phenotypic and genotypic spectrum of PAX6-associated ocular diseases, and facilitates the understanding of the crucial role that PAX6 plays in the development of the eye. Meanwhile, PAX6 could be considered as a candidate pathogenic gene of bilateral symmetrical corectopia.

Anterior segment dysgenesis is a severe developmental eye disorder that leads to blindness in children. The exact mechanisms underlying this condition remain elusive. Recently, an increasing amount of studies have focused on genes and signal transduction pathways that affect anterior segment dysgenesis;these factors include transcription factors, developmental regulators, extracellular matrix genes, membrane-related proteins, cytoskeleton proteins and other associated genes. To date, dozens of gene variants have been found to cause anterior segment dysgenesis. However, there is still a lack of effective treatments. With a broader and deeper understanding of the molecular mechanisms underlying anterior segment development in the future, gene editing technology and stem cell technology may be new treatments for anterior segment dysgenesis. Further studies on the mechanisms of how different genes influence the onset and progression of anterior segment dysgenesis are still needed.

BACKGROUND: To report a family with severe ocular disorder caused by double gene variants in causative genes of autosomal dominant cataracts, GJA8 and CRYGC.
METHODS: A 5-month-old boy with poor vision and enophthalmos was referred to our hospital. Further ocular examination showed horizontal nystagmus, iris abnormalities with pinpoint pupils, and extreme microphthalmia with axial right and left eye lengths of 13.48 mm and 13.75 mm, respectively. Digenic heterozygous variants (c.269T > G, p.Leu90Arg in CRYGC and c.151G > A, p.Asp51Asn in GJA8) have been detected based on the whole exome sequencing. His mother, who carried variant in CRYGC (c.269T > G, p.Leu90Arg), had nuclear cataract, microcornea and nystagmus, while his father, who carried variant in GJA8 (c.151G > A, p.Asp51Asn), showed bilateral membranous cataract, microphthalmia, sclerocornea, glaucoma, and nystagmus.
CONCLUSIONS: To our knowledge, this is the first report of a patient with variants in two cataract-related genes. Importantly, patient with double heterozygous variants in two dominantly inherited genes may suffer more serious phenotypes than those with heterozygous variant in a single dominantly inherited gene. Whole exome or genome sequencing is necessary for a genetic diagnosis in case of multiple gene variants.

OBJECTIVE: To describe a new strategy to manage ectopia lentis in ASD patients assessing the visual outcomes and safety of supracapsular scleral sutured intraocular lens implantation and analyzing the accuracy of different intraocular lens (IOL) power calculation formulae.
METHODS: Eight patients with ASD (13 eyes) were underwent supracapsular scleral suture fixation of posterior chamber (PC) IOL without capsular extirpation. The preoperative and postoperative clinical features were compared. The prediction error values from four formulae (SRK/T, Holladay 1, Hoffer Q, Haigis), with or without Wang-Koch (WK) adjustment, were calculated for the cases.
RESULTS: Zonulodialysis and premature cataracts could be the main reason for the decreased vision in patients with ASD. There was a significant improvement in best corrected visual acuity on 3-month follow-up after applying supracapsular scleral suture fixation of PC IOL. The prediction errors of the different formulae showed a slight tendency towards postoperative myopia. The Haigis formula with WK adjustment showed the best performance.
CONCLUSIONS: Supracapsular scleral suture fixation of IOLs for retaining the capsule-zonule barrier is a good option for ASD patients. The Haigis formula is recommended for ASD patients treated with supracapsular scleral suture fixation of IOLs. The predicted IOL power should be reduced based on the effect of the new anatomic position of the IOL to achieve a satisfactory visual outcome.

Peters\' anomaly (PA) is a rare form of anterior segment dysgenesis characterized by central corneal opacity accompanied by iridocorneal or lenticulo-corneal adhesions. Although genetic mutations, particularly those affecting transcription factors that function in eye development, are known to cause PA, the etiology of this disease remains poorly understood. In this study, 23 patients with PA were recruited for panel sequencing. Four out of 23 patients were found to carry variants in known PA causal genes, PITX2 and PITX3. More importantly, two homozygous mutations (NM_057164: p.Val86Ala and p.Arg689Cys) in the COL6A3 gene (collagen type VI alpha-3 chain) that correlated with the phenotype of type I PA were identified, and then validated by following whole-exome sequencing. The expression profile of the COL6A3 gene in the cornea and the impact of the mutations on protein physiological processing and cellular function were further explored. It was shown that COL6A3 presented relatively high expression in the cornea. The mutant COL6A3 protein was relatively retained intracellularly, and its expression reduced cellular resistance to oxidative stress through an enhanced endoplasmic reticulum stress response. Taken together, our findings expanded the known genetic spectrum of PA, and provided evidence for the involvement of COL6A3 or collagen VI in ocular anterior segment development, thereby offering new insight for future investigations targeting PA.

OBJECTIVE: To explore the molecular mechanisms in lens development and the pathogenesis of Peters anomaly in Smad4 defective mice.
METHODS: Le-Cre transgenic mouse line was employed to inactivate Smad4 in the surface ectoderm selectively. Pathological techniques were used to reveal the morphological changes of the anterior segment in Smad4 defective eye. Immunohistochemical staining was employed to observe the expression of E-cadherin, N-cadherin and α-SMA in anterior segment of Smad4 defective mice and control mice at embryonic (E) day 16.5. Real-time quantitative polymerase chain reaction (qPCR) was performed to detect the expression of Snail, Zeb1, Zeb2 and Twist2 in lens of Smad4 defective mice and control mice at E16.5. Statistical evaluations were performed using the unpaired Student\'s t-test (two-tailed) by SPSS 11.0 software.
RESULTS: Conditional deletion of Smad4 on eye surface ectoderm resulted in corneal dysplasia, iridocorneal angle closure, corneolenticular adhesions and cataract resembling Peters anomaly. Loss of Smad4 function inhibited E-cadherin expression in the lens epithelium cells and corneal epithelium cells in Smad4 defective eye. Expression of N-cadherin was up-regulated in corneal epithelium and corneal stroma. Both E-cadherin and N-cadherin were down-regulated at the future trabecular meshwork region in mutant eye. The qPCR results showed that the expression of Twist2 was increased significantly in the mutant lens (P<0.01).
CONCLUSIONS: Smad4 is essential to eye development and likely a candidate pathogenic gene to Peters anomaly by regulating epithelial-mesenchymal transition. Twist2 can be regulated by Smad4 and plays an essential role in lens development.