ITPR1: The missing gene in miosis-ataxia syndrome?

The association of early-onset non-progressive ataxia and miosis is an extremely rare phenotypic entity occasionally reported in the literature. To date, only one family (two siblings and their mother) has benefited from a genetic diagnosis by the identification of a missense heterozygous variant (p.Arg36Cys) in the ITPR1 gene. This gene encodes the inositol 1,4,5-trisphosphate receptor type 1, an intracellular channel that mediates calcium release from the endoplasmic reticulum. Deleterious variants in this gene are known to be associated with two types of spinocerebellar ataxia, SCA15 and SCA29, and with Gillespie syndrome that is associated with ataxia, partial iris hypoplasia, and intellectual disability. In this work, we describe a novel individual carrying a heterozygous missense variant (p.Arg36Pro) at the same position in the N-terminal suppressor domain of ITPR1 as the family previously reported, with the same phenotype associating early-onset non-progressive ataxia and miosis. This second report confirms the implication of ITPR1 in the miosis-ataxia syndrome and therefore broadens the clinical spectrum of the gene. Moreover, the high specificity of the phenotype makes it a recognizable syndrome of genetic origin.

Microphthalmia and anterior segment dysgenesis due to a double gene variant in GJA8 and CRYGC

INTRODUCTION

To report a family with severe ocular disorder caused by double gene variants in causative genes of autosomal dominant cataracts, GJA8 and CRYGC.

CASE PRESENTATION

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.

Risk and Prognostic Factors for Glaucoma Associated with Peters Anomaly

Glaucoma secondary to Peters anomaly is an important factor affecting visual prognosis, but there are few reports on the condition. This study aimed to investigate the characteristics of glaucoma associated with Peters anomaly and glaucoma surgery outcomes. This retrospective study included 31 eyes of 20 patients with Peters anomaly. Peters anomaly was classified into three stages: Stage 1, with a posterior corneal defect only; Stage 2, a corneal defect with iridocorneal adhesion; and Stage 3, a corneal defect with lens abnormalities. The associations between glaucoma and anterior segment dysgenesis severity, visual prognosis, and glaucoma surgery outcomes were analyzed. Sixteen eyes of ten patients developed glaucoma. Stage 1 Peters anomaly had no glaucoma, 52% of Stage 2 had glaucoma, and 75% of Stage 3 had glaucoma. Of the 16 eyes with glaucoma, 11 underwent surgery. Eight of these eleven eyes achieved intraocular pressure (IOP) control. Five of the nine eyes that underwent trabeculotomy (TLO) succeeded, and none had corneal staphyloma. Three of the four eyes for which TLO was ineffective had corneal staphyloma (p = 0.0331). Patients with Peters anomaly are more likely to develop glaucoma as anterior segment dysgenesis progresses, and the effect of TLO is limited if corneal staphyloma is present.

Chromosome 6p25 deletion syndrome: A case report and review of ophthalmic features

The 6p25 deletion syndrome is a rare genetic disorder characterized by a wide spectrum of congenital anomalies. Ophthalmic abnormalities appear to be highly associated with the syndrome, although this relationship has not been well characterized to date. We conducted a systematic literature review to highlight the ocular features in patients with this deletion syndrome and describe a 7-month-old female who has a 6.07 MB 6p25.1p25.3 deletion and a 4.25 MB 17q25.3 duplication. Our patient presented with multiple congenital anomalies, including macrocephaly, frontal bossing, low set ears, tent-shaped mouth, saddle nose, flat midface, and hearing impairment. Her ophthalmic features included proptosis, down-slanting palpebral fissures, hypertelorism, nystagmus, bilateral posterior embryotoxon, and decentered and abnormally shaped pupils. A systematic review of the published cases with sufficient clinical eye descriptions included 63 cases with a confirmed 6p25 deletion. The most common eye findings observed were posterior embryotoxon, iris hypoplasia, corectopia, cornea opacity, and glaucoma.

Design and Outcomes of a Novel Multidisciplinary Ophthalmic Genetics Clinic

The Multidisciplinary Ophthalmic Genetics Clinic (MOGC) at the University of Michigan Kellogg Eye Center aims to provide medical and ophthalmic genetics care to patients with inherited ocular conditions. We have developed a clinical and referral workflow where each patient undergoes coordinated evaluation by our multidisciplinary team followed by discussions on diagnosis, prognosis, and genetic testing. Testing approaches are specific to each patient and can be targeted (single-gene, gene panel), broad (chromosomal microarray, whole-exome sequencing), or a combination. We hypothesize that this clinic model improves patient outcomes and quality of care. A retrospective chart review of patients in the MOGC from July 2020 to October 2022 revealed that the most common referral diagnoses were congenital cataracts, optic neuropathy, and microphthalmia, with 52% syndromic cases. Within this patient cohort, we saw a 76% uptake for genetic testing, among which 33% received a diagnostic test result. Our results support a tailored approach to genetic testing for specific conditions. Through case examples, we highlight the power and impact of our clinic. By integrating ophthalmic care with medical genetics and counseling, the MOGC has not only helped solve individual patient diagnostic challenges but has aided the greater population in novel genetic discoveries and research towards targeted therapeutics.

Comparison of Anterior Segment Abnormalities in Individuals With FOXC1 and PITX2 Variants

PURPOSE

Axenfeld-Rieger syndrome encompasses a group of developmental disorders affecting the anterior chamber structures of the eye, with associated systemic features in some cases. This study aims to compare the difference in anterior segment phenotypes such as those involving the cornea, iris, lens, and anterior chamber angle between cases with disease-causing sequence variations in FOXC1 and PITX2 .

METHODS

This cross-sectional study involved 61 individuals, from 32 families with pathogenic FOXC1 or PITX2 variants, who were registered with the Australian and New Zealand Registry of Advanced Glaucoma.

RESULTS

The median age of the cohort was 39 years at the time of last assessment (range 3-85 years; females, 54%). Thirty-two patients had pathogenic variants in the FOXC1 gene, and 29 patients had pathogenic variants in the PITX2 gene. Corneal abnormalities were more common in individuals with FOXC1 variants (18/36, 50%) than those with PITX2 variants (4/25, 16%; P = 0.007). Iris abnormalities such as hypoplasia ( P = 0.008) and pseudopolycoria ( P = 0.001) were more common in individuals with PITX2 variants than those with FOXC1 variants. Glaucoma was present in 72% of participants. Corneal decompensation was positively associated with corneal abnormalities ( P < 0.001), glaucoma surgery ( P = 0.025), and cataract surgery ( P = 0.002).

CONCLUSIONS

Corneal abnormalities were more common in individuals with FOXC1 than in those with PITX2 variants and were often associated with early onset glaucoma. These findings highlight that patients with FOXC1 variations require close follow-up and monitoring throughout infancy and into adulthood.

Update on Pediatric Corneal Diseases and Keratoplasty

Managing pediatric corneal disorders is challenging as the prognosis of pediatric keratoplasty depends on several factors. Advancements in the genetic basis of congenital corneal diseases and investigations in congenital corneal conditions provide a better understanding of pediatric corneal conditions. Surgeons performing keratoplasty in children now have a choice of various techniques. Evolving surgical techniques of anterior lamellar and endothelial keratoplasties has expanded the management interventions in these pediatric corneal morbidity conditions; however, considerable concerns still exist in association with corneal transplantation in infants and children. Outcomes in pediatric keratoplasty depend upon the preoperative indications, the timing of surgical intervention, intraoperative and postoperative factors including the patient/care givers' compliance. Factors such as low scleral rigidity, higher rate of graft failure, need for frequent examinations under anesthesia, and difficulty in optimal visual acuity assessment still remain a considerable challenge in pediatric scenarios. In children, deprivation amblyopia as a result of the corneal opacification can adversely affect visual development, causing dense amblyopia. Outcomes to surgical interventions for management of corneal opacification in children is further compromised by the pre-existing amblyopia apart from the concerns of refractive outcome of the graft. Graft rejection, graft infection, amblyopia, and glaucoma continue to be serious concerns. In recent years both anterior and posterior lamellar keratoplasty techniques are being increasingly performed in pediatric eyes, which offer advantages in the form of lower risk of graft rejection. The timing of surgery, careful case selection, cautious intraoperative approach, and optimal postoperative management can improve the anatomical and functional outcome in difficult cases.

Case report of the rare Peters' anomaly complicated with Axenfeld-Rieger syndrome: A case report and brief review of the literature

INTRODUCTION

Peters' anomaly (PA) and Axenfeld-Rieger syndrome (ARS) are typical classifications of anterior segment dysgenesis (ASD) and ascribed to congenital eye diseases that encompass developmental defects in anterior segment structures. The aim of this study is to discuss the unusual association between PA and ARS and to determine the results of penetrating keratoplasty combined with extracapsular cataract extraction and anterior vitrectomy for this unusual ophthalmic phenotype.

PATIENT CONCERNS

A 72-year-old female was referred to Changzhou No. 2 People's Hospital for a progressive decrease in visual acuity in both eyes in the past few decades.

DIAGNOSES

The patient was diagnosed with PA with cone-shaped polar cataracts in the left eye based on a series of ophthalmic examinations. ARS with retinal detachment was diagnosed in the right eye 2 years prior.

INTERVENTIONS

Penetrating keratoplasty combined with extracapsular cataract extraction and anterior vitrectomy were performed to manage PA with cataracts in the left eye.

OUTCOMES

Her best corrected visual acuity did not improve significantly after the operation. Patients with ARS and PA should be treated cautiously because of fundus lesions.

CONCLUSION

This study revealed that cases with PA accompanied by iridocorneal adhesions, or other ocular anomalies, need to be treated cautiously for a very low success rate. It is of reference value for the evaluation of treatment prognosis for this joint occurrence of ophthalmic phenotypes.

Long-term outcomes in Primary congenital glaucoma, aniridia and anterior segment dysgenesis

Aim

To determine the long-term outcomes of a cohort of complex patients with primary congenital glaucoma, aniridia and anterior segment dysgenesis.

Methods

Retrospective consecutive series between 1990–2021 in two UK tertiary centres: Guy's and St Thomas’ NHS Foundation Trust and King's College Hospital NHS Foundation Trust. We recorded the number and types of surgical and laser treatments along with preoperative and postoperative data, including intraocular pressures (IOP) and anti-glaucoma medications.

Results

A total of 41 eyes of 21 patients were included. Primary diagnoses were primary congenital glaucoma in 16 eyes (39.0%), aniridia in 14 eyes (34.2%), and anterior segment dysgenesis in 8 eyes (19.5%). Sixteen eyes (39.0%) had one or more glaucoma surgery or laser procedures for advanced glaucoma, and the long-term follow-up was 12.8 ± 3.6 years. There was a significant decrease in postoperative IOP (mmHg) at 3 months (16.5 ± 1.6; p = 0.0067), 6 months (18.7 ± 2.1; p = 0.0386), 12 months (18.6 ± 1.7; p = 0.0229), 3 years (14.7 ± 1.2; p = 0.0126), 5 years (15.5 ± 1.8; p = 0.0330) and 10 years (15.4 ± 2.3; p = 0.7780), compared to preoperatively (24.1 ± 2.6). Surgical success (complete and qualified) was 62.5%, 50.0%, 43.8%, 46.2%, 45.5% and 28.6% at 3 months, 6 months, 12 months, 3 years, 5 years and 10 years, respectively. There was no significant change in the number of anti-glaucoma drugs postoperatively (p > 0.05). Four eyes (25.0%) had postoperative complications (hyphaema, hypotony) that resolved after conservative management.

Conclusions

Surgical management of these complex eyes with advanced glaucoma is challenging. Overall, the cohort had good surgical outcomes with a significant decrease in IOP by 36.1% after long-term follow-up.

Clinical management of a rare Peters' anomaly-induced secondary childhood glaucoma: A case report

Childhood glaucoma is a rare disorder that occurs from birth until teenage years caused by an abnormality of aqueous humor pathways. About 50-70% of Peters' anomaly is accompanied by secondary childhood glaucoma. The presence of glaucoma will affect the prognosis. We reported the evaluation and treatment of secondary childhood glaucoma due to Peters' anomaly. A 5 months-old boy was presented with the complaint of a enlarged left eye since 3 months old. The complaint was accompanied by a watering eye and frequently closed upon light exposure. The left eye looked opaquer than contralateral. Examination under anesthesia showed that the intraocular pressure (IOP) was 35 mmHg in the left eye and the corneal diameter was 14 mm. Other findings were keratopathy, diffuse corneal edema, buphthalmos, shallow anterior chamber, anterior synechiae, and linear slit shaped pupils in the nasal region. Patient was treated with ophthalmic timolol maleate which was later followed by trabeculectomy. After 1 week post-surgery, IOP assessment by palpation suggested the right eye within normal range while the IOP of left eye was higger than normal. Blepharospasm, epiphora, photophobia, bleb on superior, subconjunctiva bleeding, buphthalmos, keratopathy, minimal corneal edema, anterior chamber with shallow image, and posterior synechia were found in left eye anterior segment. In conclusion, trabeculotomy and trabeculectomy are recommended if there is no reduction of IOP observed after receiving timolol maleate therapy. The choice of surgical management is dependent on the feasibility of the protocol.

Novel CHRDL1 mutation causing X-linked megalocornea in a family with mild anterior segment manifestations in carrier females

PURPOSE

X-linked megalocornea (XMC) is a rare anterior segment malformation characterized by a nonprogressive enlargement of the cornea to 13 mm or greater in the setting of normal intraocular pressure. XMC is caused by mutations in the CHRDL1 gene and it is inherited as an X-linked recessive trait affecting only males. Here, we describe the results of phenotypic and genetic assessment in a novel XMC pedigree.

METHODS

Three subjects (a father and his two daughters) underwent a complete clinical and imaging ocular examination including biomicroscopy, fundoscopy, tonometry, visual acuity, Pentacam Scheimpflug imaging, anterior segment Swept Source OCT, and ultrabiomicroscopy. Genetic analysis was performed through whole exome sequencing in 3 family members. Candidate variants were validated by sanger sequencing.

RESULTS

The affected father exhibited megalocornea, very deep anterior chambers, retrocorneal pigmentation, iris atrophy, queer iris configuration, extremely open iridocorneal angles, and cataracts. Notably, both daughters showed queer iris configuration and abnormally widely open iridocorneal angles in both eyes. Genetic analysis identified a novel hemizygous c.207+1G>A splicing variant in CHRDL1 in the affected father. Both mildly affected daughters were heterozygous for the pathogenic variant.

CONCLUSIONS

Here, we report an additional XMC family due to a novel mutation in the CHRDL1 gene. Mild anterior segment anomalies were observed in two heterozygous carriers demonstrating for the first time a CHRDL1-linked phenotype in females. A detailed comparison of the clinical and genetic features of this pedigree with those observed in previously published XMC cases is also presented.

Glaucoma Syndromes: Insights into Glaucoma Genetics and Pathogenesis from Monogenic Syndromic Disorders

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.

Novel heterozygous variants in PXDN cause different anterior segment dysgenesis phenotypes in monozygotic twins

BACKGROUND

Since bi-allelic variants in the PXDN gene were first discovered in 2011 to be associated with anterior segment dysgenesis, a spectrum of ophthalmologic and systemic clinical manifestations has been described. This manuscript reports two distinct clinical phenotypes in monozygotic twin sisters, including the previously unreported ocular manifestation of bilateral primary aphakia, associated with novel compound heterozygous variants in the PXDN gene.

MATERIALS AND METHODS

We used genome sequencing to study a non-consanguineous family with monozygotic twin sister probands: one presenting with bilateral microphthalmia, primary aphakia, total corneal opacification, congenital glaucoma, and complex systemic comorbidities; the other with anterior persistent fetal vasculature in the right eye, and Peters anomaly type 2 with cataract and iris coloboma in the left eye but no systemic issues. These findings were compared to published reports of PXDN-related ocular diseases upon comprehensive review of prior literature.

RESULTS

In both affected sisters, genome sequencing identified two novel heterozygous variants in trans in the PXDN gene: c.1569_1570insT, predicting p.(Thr524TyrfsTer53), and c.3206 C > A, predicting p.(Ala1069Asp), respectively. No other potentially diagnostic variants were identified in any other genes.

CONCLUSIONS

This report on two novel compound heterozygous variants in the PXDN gene associated with previously unreported clinical manifestations further expands the genotypic and phenotypic spectrum associated with this gene. Our finding of distinctive clinical phenotypes associated with identical compound heterozygous PXDN variants in monozygotic twins emphasizes the significant clinical variability that can occur, suggesting a potential role for stochastic developmental and/or epigenetic factors in the ultimate pathophysiologic pathway.

Novel Biallelic Variants and Phenotypic Features in Patients with SLC38A8-Related Foveal Hypoplasia

Biallelic pathogenic variants in solute carrier family 38 member 8, SLC38A8, cause a pan-ocular autosomal recessive condition known as foveal hypoplasia 2, FVH2, characterised by foveal hypoplasia, nystagmus and optic nerve chiasmal misrouting. Patients are often clinically diagnosed with ocular albinism, but foveal hypoplasia can occur in several other ocular disorders. Here we describe nine patients from seven families who had molecularly confirmed biallelic recessive variants in SLC38A8 identified through whole genome sequencing or targeted gene panel testing. We identified four novel sequence variants (p.(Tyr88*), p.(Trp145*), p.(Glu233Gly) and c.632+1G>A). All patients presented with foveal hypoplasia, nystagmus and reduced visual acuity; however, one patient did not exhibit any signs of chiasmal misrouting, and three patients had features of anterior segment dysgenesis. We highlight these findings in the context of 30 other families reported to date. This study reinforces the importance of obtaining a molecular diagnosis in patients whose phenotype overlap with other inherited ocular conditions, in order to support genetic counselling, clinical prognosis and family planning. We expand the spectrum of SLC38A8 mutations which will be relevant for treatment through future genetic-based therapies.

Whole Exome Sequencing in Coloboma/Microphthalmia: Identification of Novel and Recurrent Variants in Seven Genes

Coloboma and microphthalmia (C/M) are related congenital eye malformations, which can cause significant visual impairment. Molecular diagnosis is challenging as the genes associated to date with C/M account for only a small percentage of cases. Overall, the genetic cause remains unknown in up to 80% of patients. High throughput DNA sequencing technologies, including whole-exome sequencing (WES), are therefore a useful and efficient tool for genetic screening and identification of new mutations and novel genes in C/M. In this study, we analyzed the DNA of 19 patients with C/M from 15 unrelated families using singleton WES and data analysis for 307 genes of interest. We identified seven novel and one recurrent potentially disease-causing variants in CRIM1, CHD7, FAT1, PTCH1, PUF60, BRPF1, and TGFB2 in 47% of our families, three of which occurred de novo. The detection rate in patients with ocular and extraocular manifestations (67%) was higher than in patients with an isolated ocular phenotype (46%). Our study highlights the significant genetic heterogeneity in C/M cohorts and emphasizes the diagnostic power of WES for the screening of patients and families with C/M.

Novel Mutations in COL6A3 That Associated With Peters' Anomaly Caused Abnormal Intracellular Protein Retention and Decreased Cellular Resistance to Oxidative Stress

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.

Histopathological examination of congenital corneal staphyloma and prognosis after penetrating keratoplasty

The aim of this study was to investigate the histopathological manifestations of congenital corneal staphyloma accompanied by anterior segment dysgenesis and evaluate the prognosis after penetrating keratoplasty with an ultralarge button graft.We retrospectively studied 8 pediatric patients with large congenital corneal staphylomas in the Department of Ophthalmology of Peking University Third Hospital, China, between September 2014 and December 2018. All patients underwent penetrating keratoplasty with ultralarge button grafts, as well as additional operations according to the abnormality of each eye. Pathological investigations of all samples obtained during penetrating keratoplasty were performed with hematoxylin and eosin staining.The main clinical characteristic of congenital corneal staphyloma was an extremely opaque and ectatic cornea. Histopathological examination showed abnormal corneal epithelia and stroma and an absence of Bowman membrane, Descemet membrane, and the endothelium. Different severities of anterior segment dysgenesis, presenting as various histopathological manifestations, were observed in all cases. Several postoperative complications occurred after penetrating keratoplasty in some of the patients; however, the complications were discovered and treated accordingly in a timely manner. Six patients achieved good visual outcomes and a satisfactory cosmetic appearance after penetrating keratoplasty. One patient eventually lost the transparency of the button because of corneal neovascularization, and 1 patient lost visual function because of retinal detachment.Congenital corneal staphyloma combined with anterior segment dysgenesis can exhibit various manifestations on histopathological examination. Penetrating keratoplasty with an ultralarge button graft seems to be a suitable treatment for congenital corneal staphyloma to obtain good functional and aesthetic prognoses.

Novel mutations in the PITX2 gene in Pakistani and Mexican families with Axenfeld-Rieger syndrome

PURPOSE

Axenfeld-Rieger syndrome (ARS) is a rare autosomal dominant disorder that affects the anterior segment of the eye. The aim of this study was to examine the PITX2 gene to identify possible novel mutations in Pakistani and Mexican families affected by the ARS phenotype.

METHODS

Three unrelated probands with a diagnosis of ARS were recruited for this study. Genomic DNA was isolated from the peripheral blood of the probands and their family members. Polymerase chain reaction and Sanger sequencing were used for the analysis of coding exons and the flanking intronic regions of the PITX2 gene. Bioinformatics tools and database (VarSome, Provean, and MutationTaster, SIFT, PolyPhen-2, and HOPE) were evaluated to explore missense variants.

RESULTS

We identified novel heterozygous variations in the PITX2 gene that segregated with the ARS phenotype within the families. The variant NM_153426.2(PITX2):c.226G > T or p.(Ala76Ser) and the mutation NM_153426.2(PITX2):c.455G > A or p.(Cys152Tyr) were identified in two Pakistani pedigrees, and the mutation NM_153426.2(PITX2):c.242_265del or p.(Lys81_Gln88del), segregated in a Mexican family.

CONCLUSION

Our study extends the spectrum of PITX2 mutations in individuals with ARS, enabling an improved diagnosis of this rare but serious syndrome.

Spatiotemporal Characterization of Anterior Segment Mesenchyme Heterogeneity During Zebrafish Ocular Anterior Segment Development

Assembly of the ocular anterior segment (AS) is a critical event during development of the vertebrate visual system. Failure in this process leads to anterior segment dysgenesis (ASD), which is characterized by congenital blindness and predisposition to glaucoma. The anterior segment is largely formed via a neural crest-derived population, the Periocular Mesenchyme (POM). In this study, we aimed to characterize POM behaviors and transcriptional identities during early establishment of the zebrafish AS. Two-color fluorescent in situ hybridization suggested that early AS associated POM comprise of a heterogenous population. In vivo and time-course imaging analysis of POM distribution and migratory dynamics analyzed using transgenic zebrafish embryos (Tg[foxc1b:GFP], Tg[foxd3:GFP], Tg[pitx2:GFP], Tg[lmx1b.1:GFP], and Tg[sox10:GFP]) revealed unique AS distribution and migratory behavior among the reporter lines. Based on fixed timepoint and real-time analysis of POM cell behavior a comprehensive model for colonization of the zebrafish AS was assembled. Furthermore, we generated single cell transcriptomic profiles (scRNA) from our POM reporter lines and characterized unique subpopulation expression patterns. Based on scRNA clustering analysis we observed cluster overlap between neural crest associated (sox10/foxd3), POM (pitx2) and finally AS specified cells (lmx1b, and foxc1b). scRNA clustering also revealed several novel markers potentially associated with AS development and/or function including lum, fmoda, adcyap1b, tgfbi, and hmng2. Taken together, our data indicates that AS-associated POM, or Anterior Segment Mesenchyme (ASM), is not homogeneous but rather comprised of several subpopulations with differing colonization patterns, migration behavior, and transcriptomic profiles.

Spectrum of Genetic Variants Associated with Anterior Segment Dysgenesis in South Florida

Anterior segment dysgenesis (ASD) comprises a wide spectrum of developmental conditions affecting the cornea, iris, and lens, which may be associated with abnormalities of other organs. To identify disease-causing variants, we performed exome sequencing in 24 South Florida families with ASD. We identified 12 likely causative variants in 10 families (42%), including single nucleotide or small insertion–deletion variants in B3GLCT, BMP4, CYP1B1, FOXC1, FOXE3, GJA1, PXDN, and TP63, and a large copy number variant involving PAX6. Four variants were novel. Each variant was detected only in one family. Likely causative variants were detected in 1 out of 7 black and 9 out of 17 white families. In conclusion, exome sequencing for ASD allows us to identify a wide spectrum of rare DNA variants in South Florida. Further studies will explore missing variants, especially in the black communities.

Maternal diet as a risk factor for primary congenital glaucoma and defects of the anterior segment of the eye in the National Birth Defects Prevention Study

Primary congenital glaucoma (PCG) and anterior segment defects (ASDs) are rare ocular malformations diagnosed early in life which can cause blindness. Pathogenic variants in several genes have been linked to these conditions, but little is known about nongenetic risk factors. We investigated the association between maternal nutrition and PCG and ASDs in the National Birth Defects Prevention Study, a large population-based, multicenter case-control study of major birth defects in the United States. Mothers of cases (n = 152) and control infants without a birth defect (n = 9,178) completed an interview which included a food frequency questionnaire capturing usual dietary intake in the year before pregnancy. Maternal nutrition was assessed through individual nutrient intake, calculating a Diet Quality Index for Pregnancy (DQI-P) score for each mother, and using latent class analysis to empirically derive four dietary patterns. We calculated adjusted odds ratios (aORs) and 95% confidence intervals (CI) using logistic regression. The results for individual nutrients varied, with some having an inverse or U-shaped pattern of association with increasing intake. The DQI-P was not associated with risk of PCG and ASDs (aOR 0.91; CI 0.49-1.66, highest vs. lowest quartile). The dietary pattern analysis suggested lower odds among women with a Prudent and Mexican dietary pattern (aOR 0.82, 95% CI 0.52-1.29; aOR 0.80, 95% CI 0.36-1.78, respectively) compared to those with a Western dietary pattern. We found that higher intake of some nutrients and certain dietary patterns may be inversely associated with PCG and ASDs, though caution is urged due to imprecision of estimates.

Ring chromosome 6 in a child with anterior segment dysgenesis and review of its overlap with other FOXC1 deletion phenotypes

Here, we report a patient with ring chromosome 6 [r(6)], associated with anterior segment dysgenesis (ASD) and other anomalies. The phenotype was due to a 1880 kb microdeletion at 6p25.3 identified by whole-genome array analysis, and was mainly attributable to a FOXC1 haploinsufficiency. Currently 37 patients with r(6) have been reported. We found that facial dysmorphism, ASD, heart anomalies, brain anomalies, and hearing loss are constant features only in severe cases of r(6), mainly related to hemizygosity of FOXC1. Thus, overlaps with other FOXC1 related phenotypes, such as the 6p25 deletion syndrome, Axenfeld-Rieger syndrome type 3, and ASD type 3. Contrarily, those patients whose r(6) does not disrupt FOXC1, have mild or moderate phenotypes and do not exhibit ASD.

TASP1 mutation in a female with craniofacial anomalies, anterior segment dysgenesis, congenital immunodeficiency and macrocytic anemia

Background

Threonine Aspartase 1 (Taspase 1) is a highly conserved site‐specific protease whose substrates are broad‐acting nuclear transcription factors that govern diverse biological programs, such as organogenesis, oncogenesis, and tumor progression. To date, no single base pair mutations in Taspase 1 have been implicated in human disease.

Methods

A female infant with a new pattern of diagnostic abnormalities was identified, including severe craniofacial anomalies, anterior and posterior segment dysgenesis, immunodeficiency, and macrocytic anemia. Trio‐based whole exome sequencing was performed to identify disease‐causing variants.

Results

Whole exome sequencing revealed a normal female karyotype (46,XX) without increased regions of homozygosity. The proband was heterozygous for a de novo missense variant, c.1027G>A predicting p.(Val343Met), in the TASP1 gene (NM_017714.2). This variant has not been observed in population databases and is predicted to be deleterious.

Conclusion

One human patient has been reported previously with a large TASP1 deletion and substantial evidence exists regarding the role of several known Taspase 1 substrates in human craniofacial and hematopoietic disorders. Moreover, Taspase 1 deficiency in mice results in craniofacial, ophthalmological and structural brain defects. Taken together, there exists substantial evidence to conclude that the TASP1 variant, p.(Val343Met), is pathogenic in this patient.

Relationship between neural crest cell specification and rare ocular diseases

Development of the eye is closely associated with neural crest cell migration and specification. Eye development is extremely complex, as it requires the working of a combination of local factors, receptors, inductors, and signaling interactions between tissues such as the optic cup and periocular mesenchyme (POM). The POM is comprised of neural crest-derived mesenchymal progenitor cells that give rise to numerous important ocular structures including those tissues that form the optic cup and anterior segment of the eye. A number of genes are involved in the migration and specification of the POM such as PITX2, PITX3, FOXC1, FOXE3, PAX6, LMX1B, GPR48, TFAP2A, and TFAP2B. In this review, we will discuss the relevance of these genes in the development of the POM and how mutations and defects result in rare ocular diseases.

Bilateral anterior segment dysgenesis with the presumed Peters' anomaly in a cat

A seven-month-old female domestic shorthaired cat was presented for buphthalmos in the right eye and corneal cloudiness in the left eye. Full ophthalmic examinations were performed for both eyes and enucleation was done for the right nonvisual eye. Congenital glaucoma caused by anterior segment dysgenesis was confirmed for the right eye. In the left eye, slit-lamp examination revealed focal corneal edema with several iris strands from iris collarette to the affected posterior corneal surfaces. Circular posterior corneal defect was suggested to be the cause of edema. Goniodysgenesis, additionally, was identified. Taken together, the diagnosis of Peters’ anomaly which is a subtype of anterior segment dysgenesis was suggested in the left eye.

A Novel Mutation in FOXC1 in a Lebanese Family with Congenital Heart Disease and Anterior Segment Dysgenesis: Potential Roles for NFATC1 and DPT in the Phenotypic Variations

Congenital heart diseases (CHDs) are still the leading cause of death in neonates. Anterior segment dysgenesis is a broad clinical phenotype that affects the normal development of the eye, leading in most of the cases to glaucoma which is still a major cause of blindness for children and adolescents. Despite tremendous insights gained from genetic studies, a clear genotype–phenotype correlation is still difficult to draw. In Lebanon, a small country with still a high rate of consanguineous marriages, there are little data on the epidemiology of glaucoma amongst children with or without CHD. We carried out whole exome sequencing (WES) on a family with anterior segment dysgenesis, and CHD composed of three affected children with glaucoma, two of them with structural cardiac defects and three healthy siblings. The results unravel a novel mutation in FOXC1 (p. R127H) segregating with the phenotype and inherited from the mother, who did not develop glaucoma. We propose a digenic model for glaucoma in this family by combining the FOXC1 variant with a missense variant inherited from the father in the dermatopontin (DPT) gene. We also unravel a novel NFATC1 missense mutation predicted to be deleterious and present only in the patient with a severe ocular and cardiac phenotype. This is the first report on FOXC1 using WES to genetically characterize a family with both ocular and cardiac malformations. Our results support the usage of such technology to have a better genotype–phenotype picture for Mendelian-inherited diseases for which expressivity and penetrance are still not answered.

New mutations in GJA8 expand the phenotype to include total sclerocornea

This project expands the disease spectrum for mutations in GJA8 to include total sclerocornea, rudimentary lenses and microphthalmia, in addition to this gene's previously known role in isolated congenital cataracts. Ophthalmic findings revealed bilateral total sclerocornea in 3 probands, with small abnormal lenses in 2 of the cases, and cataracts and microphthalmia in 1 case. Next-generation sequencing revealed de novo heterozygous mutations affecting the same codon of GJA8 : (c.281G>A; p.(Gly94Glu) and c.280G>C; p.(Gly94Arg)) in 2 of the probands, in addition to the c.151G>A; p.(Asp51Asn) mutation we had previously identified in the third case. In silico analysis predicted all of the mutations to be pathogenic. These cases show that deleterious, heterozygous mutations in GJA8 can lead to a severe ocular phenotype of total sclerocornea, abnormal lenses, and/or cataracts with or without microphthalmia, broadening the phenotype associated with this gene. GJA8 should be included when investigating patients with the severe anterior segment abnormality of total sclerocornea.

The rare Axenfeld-Rieger syndrome with systemic anomalies: A case report and brief review of literature

RATIONALE

Axenfeld-Rieger syndrome (ARS) is a rare autosomal dominant disorder with ocular anterior segment dysgenesis and systemic anomalies.

PATIENT CONCERNS

A 28-year-old Chinese Han female was referred to Beijing Tongren Eye Center for progressive decrease of the visual acuity on her right eye in the past month.

DIAGNOSES

The patient was diagnosed as ARS with retinal detachment based on series of ophthalmic examinations performed.

INTERVENTIONS

A pars plana vitrectomy was performed to manage the retinal detachment.

OUTCOMES

Her best-corrected visual acuity was slightly improved after surgery.

LESSONS

ARS is a developmental defect of ocular anterior segment with various clinical manifestations which might cause misdiagnosis.

Mutations in CPAMD8 Cause a Unique Form of Autosomal-Recessive Anterior Segment Dysgenesis

Anterior segment dysgeneses (ASDs) comprise a spectrum of developmental disorders affecting the anterior segment of the eye. Here, we describe three unrelated families affected by a previously unclassified form of ASD. Shared ocular manifestations include bilateral iris hypoplasia, ectopia lentis, corectopia, ectropion uveae, and cataracts. Whole-exome sequencing and targeted Sanger sequencing identified mutations in CPAMD8 (C3 and PZP-like alpha-2-macroglobulin domain-containing protein 8) as the cause of recessive ASD in all three families. A homozygous missense mutation in the evolutionarily conserved alpha-2-macroglobulin (A2M) domain of CPAMD8, c.4351T>C (p. Ser1451Pro), was identified in family 1. In family 2, compound heterozygous frameshift, c.2352_2353insC (p.Arg785Glnfs^∗23), and splice-site, c.4549-1G>A, mutations were identified. Two affected siblings in the third family were compound heterozygous for splice-site mutations c.700+1G>T and c.4002+1G>A. CPAMD8 splice-site mutations caused aberrant pre-mRNA splicing in vivo or in vitro. Intriguingly, our phylogenetic analysis revealed rodent lineage-specific CPAMD8 deletion, precluding a developmental expression study in mice. We therefore investigated the spatiotemporal expression of CPAMD8 in the developing human eye. RT-PCR and in situ hybridization revealed CPAMD8 expression in the lens, iris, cornea, and retina early in development, including strong expression in the distal tips of the retinal neuroepithelium that form the iris and ciliary body, thus correlating CPAMD8 expression with the affected tissues. Our study delineates a unique form of recessive ASD and defines a role for CPAMD8, a protein of unknown function, in anterior segment development, implying another pathway for the pathogenicity of ASD.

Anterior segment dysgenesis correlation with epithelial-mesenchymal transition in Smad4 knockout mice

AIM

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).

CONCLUSION

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.

Unilateral foveal hypoplasia in a child with bilateral anterior segment dysgenesis

In patients with foveal hypoplasia, anterior segment dysgenesis and an absence of systemic findings, consider a recently described syndrome of foveal hypoplasia, optic nerve decussation defects and anterior segment dysgenesis (FHONDA) in the differential diagnosis.

Identification of an Alu-repeat-mediated deletion of OPTN upstream region in a patient with a complex ocular phenotype

Genetic causes of ocular conditions remain largely unknown. To reveal the molecular basis for a congenital ocular phenotype associated with glaucoma we performed whole‐exome sequencing (WES) and whole‐genome copy number analyses of patient DNA. WES did not identify a causative variant. Copy number variation analysis identified a deletion of 10p13 in the patient and his unaffected father; the deletion breakpoint contained a single 37‐bp sequence that is normally present in two distinct Alu repeats separated by ~181 kb. The deletion removed part of the upstream region of optineurin (OPTN) as well as the upstream sequence and two coding exons of coiled‐coil domain containing 3 (CCDC3); analysis of the patient's second allele showed normal OPTN and CCDC3 sequences. Studies of zebrafish orthologs identified expression in the developing eye for both genes. OPTN is a known factor in dominant adult‐onset glaucoma and Amyotrophic Lateral Sclerosis (ALS). The deletion eliminates 98 kb of the OPTN upstream sequence leaving only ~1 kb of the proximal promoter region. Comparison of transcriptional activation capability of the 3 kb normal and the rearranged del(10)(p13) OPTN promoter sequences demonstrated a statistically significant decrease for the deleted allele; sequence analysis of the entire deleted region identified multiple conserved elements with possible cis‐regulatory activity. Additional screening of CCDC3 indicated that heterozygous loss‐of‐function alleles are unlikely to cause congenital ocular disease. In summary, we report the first regulatory region deletion involving OPTN, caused by Alu‐mediated nonallelic homologous recombination and possibly contributing to the patient's ocular phenotype. In addition, our data indicate that Alu‐mediated rearrangements of the OPTN upstream region may represent a new source of affected alleles in human conditions. Evaluation of the upstream OPTN sequences in additional ocular and ALS patients may help to determine the role of this region, if any, in human disease.

Abrogation of HMX1 function causes rare oculoauricular syndrome associated with congenital cataract, anterior segment dysgenesis, and retinal dystrophy

PURPOSE

To define the phenotypic manifestation, confirm the genetic basis, and delineate the pathogenic mechanisms underlying an oculoauricular syndrome (OAS).

METHODS

Two individuals from a consanguineous family underwent comprehensive clinical phenotyping and electrodiagnostic testing (EDT). Genome-wide microarray analysis and Sanger sequencing of the candidate gene were used to identify the likely causal variant. Protein modelling, Western blotting, and dual luciferase assays were used to assess the pathogenic effect of the variant in vitro.

RESULTS

Complex developmental ocular abnormalities of congenital cataract, anterior segment dysgenesis, iris coloboma, early-onset retinal dystrophy, and abnormal external ear cartilage presented in the affected family members. Genetic analyses identified a homozygous c.650A>C; p.(Gln217Pro) missense mutation within the highly conserved homeodomain of the H6 family homeobox 1 (HMX1) gene. Protein modelling predicts that the variant may have a detrimental effect on protein folding and/or stability. In vitro analyses were able to demonstrate that the mutation has no effect on protein expression but adversely alters function.

CONCLUSIONS

Oculoauricular syndrome is an autosomal recessive condition that has a profound effect on the development of the external ear, anterior segment, and retina, leading to significant visual loss at an early age. This study has delineated the phenotype and confirmed HMX1 as the gene causative of OAS, enabling the description of only the second family with the condition. HMX1 is a key player in ocular development, possibly in both the pathway responsible for lens and retina development, and via the gene network integral to optic fissure closure.

Anterior segment developmental anomalies in a 33-week-old fetus with MIDAS syndrome

We report anterior segment abnormalities in both eyes of a 33-week-old fetus endorsing the diagnosis of MIDAS (microphthalmia, dermal aplasia, and sclerocornea) syndrome. After abortion, the fetus was examined by a standard pediatric autopsy that included macroscopic and microscopic examination of both eyes. Postmortem findings included craniofacial stigmata (such as hypertelorism, a flat nose and low-set ears) and an agenesis of the corpus callosum. Array comparative genomic hybridization revealed a deletion of the short arm of the X chromosome (region Xp22.2 to p22.32). Ophthalmopathologic examination of the eyes revealed microphthalmia with anterior segment developmental anomalies, in particular sclerocornea and Peters' anomaly, respectively. General pathology findings plus the ocular findings allowed the diagnosis of MIDAS syndrome. A discussion of differential diagnoses is provided. This case report indicates that ophthalmopathologic investigation of fetal eyes can be of great value for the further classification of syndromes.

PITX2 and FOXC1 spectrum of mutations in ocular syndromes

Anterior segment dysgenesis (ASD) encompasses a broad spectrum of developmental conditions affecting anterior ocular structures and associated with an increased risk for glaucoma. Various systemic anomalies are often observed in ASD conditions such as Axenfeld-Rieger syndrome (ARS) and De Hauwere syndrome. We report DNA sequencing and copy number analysis of PITX2 and FOXC1 in 76 patients with syndromic or isolated ASD and related conditions. PITX2 mutations and deletions were found in 24 patients with dental and/or umbilical anomalies seen in all. Seven PITX2-mutant alleles were novel including c.708_730del, the most C-terminal mutation reported to date. A second case of deletion of the distant upstream but not coding region of PITX2 was identified, highlighting the importance of this recently discovered mechanism for ARS. FOXC1 deletions were observed in four cases, three of which demonstrated hearing and/or heart defects, including a patient with De Hauwere syndrome; no nucleotide mutations in FOXC1 were identified. Review of the literature identified several other patients with 6p25 deletions and features of De Hauwere syndrome. The 1.3-Mb deletion of 6p25 presented here defines the critical region for this phenotype and includes the FOXC1, FOXF2, and FOXQ1 genes. In summary, PITX2 or FOXC1 disruptions explained 63% of ARS and 6% of other ASD in our cohort; all affected patients demonstrated additional systemic defects with PITX2 mutations showing a strong association with dental and/or umbilical anomalies and FOXC1 with heart and hearing defects. FOXC1 deletion was also found to be associated with De Hauwere syndrome.

Anterior segment dysgenesis in a child with factor VII deficiency

PURPOSE

To describe the first case of anterior segment dysgenesis associated with factor VII congenital deficit (hypoproconvertinemia).

METHOD

A 2-month-old child with factor VII deficiency was referred to our clinic because of corneal opacities. The child was born to consanguineous parents and severe factor VII deficiency was diagnosed on the third day of life because of gastrointestinal bleeding.

RESULT

Ocular examination under anesthesia showed bilateral corneal opacities with adherent iris strands and peripheral anterior synechiae. The intra-ocular pressure was normal in both eyes and there were neither signs of cataracts nor glaucomatous optic nerve damage.

CONCLUSION

This observation provide new information on the possible ocular findings in patients with hypoproconvertinemia. Based on this report, we suggest that careful coagulation screening should be considered in children who possess idiopathic anterior segment dysgenesis aiming at identifying the possible coagulation disorder.