Pax2a, but not pax2b, influences cell survival and periocular mesenchyme localization to facilitate zebrafish optic fissure closure

Background

Pax2 is required for optic fissure development in many organisms, including humans and zebrafish. Zebrafish loss‐of‐function mutations in pax2a display coloboma, yet the etiology of the morphogenetic defects is unclear. Further, pax2 is duplicated in zebrafish, and a role for pax2b in optic fissure development has not been examined.

Results

Using a combination of imaging and molecular genetics, we interrogated a potential role for pax2b and examined how loss of pax2 affects optic fissure development. Although optic fissure formation appears normal in pax2 mutants, an endothelial‐specific subset of periocular mesenchyme (POM) fails to initially localize within the optic fissure, yet both neural crest and endothelial‐derived POM ectopically accumulate at later stages in pax2a and pax2a; pax2b mutants. Apoptosis is not up‐regulated within the optic fissure in pax2 mutants, yet cell death is increased in tissues outside of the optic fissure, and when apoptosis is inhibited, coloboma is partially rescued. In contrast to pax2a, loss of pax2b does not appear to affect optic fissure morphogenesis.

Conclusions

Our results suggest that pax2a, but not pax2b, supports cell survival outside of the optic fissure and POM abundance within it to facilitate optic fissure closure.

Zebrafish pax2a null mutants display a defect in optic fissure closure and coloboma

Loss of pax2b does not affect optic fissure development

An endothelial‐specific subset of periocular mesenchyme cells fails to initially localize to the optic fissure in pax2a mutants

At a later stage of optic fissure development both neural crest and endothelial‐derived periocular mesenchyme ectopically accumulate within the optic fissure

Pax2a mutants have increased apoptosis in surrounding tissues, but not within the optic fissure margin cells, and apoptosis in part underlies the coloboma phenotype

CHARGE syndrome: A case report of two new CDH7 gene mutations

CHARGE syndrome is a genetic disorder comprising the following clinical features: coloboma, heart defects, choanal atresia, retardation (of growth and development), as well as genitourinary and ear abnormalities. This syndrome is caused by mutations in the CDH7 gene, located on chromosome 8 (8q12). We present two new gene mutations in two patients with CHARGE syndrome, not previously reported in the scientific literature. Both of these patients clearly demonstrate the difference in the clinical expression of this syndrome, with patient 1 having a greater clinical severity compared to patient 2. We conclude that although in the scientific literature to date there is no clear correlation between a patient's genotype and phenotype expression, we can assume from the cases we present that a correlation does in fact exist. Specifically, missense mutations (as in case of patient 2) are associated with milder clinical expression, whereas mutations which result in truncation of the CDH7 protein (as in the case of patient 1 having a nonsense mutation) may be associated with a more severe clinical expression.

First case of coloboma, lens neovascularization, traumatic cataract, and retinal detachment in a young Asian female

Lens neovascularization is a very rare entity to be encountered in the clinical practice. It is possibly a result of chronic ocular inflammation due to injury and subsequent uveitis. Early diagnosis and meticulous management can salvage visual acuity in such cases.

Expanding the phenotypic spectrum consequent upon de novo WDR37 missense variants

Structural eye disorders are increasingly recognised as having a genetic basis, although current genetic testing is limited in its success. De novo missense variants in WDR37 are a recently described cause of a multisystemic syndromic disorder featuring ocular coloboma. This study characterises the phenotypic spectrum of this disorder and reports 2 de novo heterozygous variants (p.Thr115Ile, p.Ser119Tyr) in three unrelated Caucasian individuals. All had a clinical phenotype consisting of bilateral iris and retinal coloboma, developmental delay and additional, variable multisystem features. The variants fall within a highly conserved region upstream of the WD-repeat domains, within an apparent mutation cluster. Consistent with the literature, intellectual disability, structural eye disorders, epilepsy, congenital heart disease, genitorenal anomalies and dysmorphic facial features were observed. In addition, a broader developmental profile is reported with a more specific musculoskeletal phenotype described in association with the novel variant (p.Thr115Ile). We further expand the phenotypic spectrum of WDR37-related disorders to include those with milder developmental delay and strengthen the association of ocular coloboma and musculoskeletal features. We promote the inclusion of WDR37 on gene panels for intellectual disability, epilepsy and structural eye disorders.

Lip Commissure to Eyelid Transposition Flap to Correct Eyelid Agenesis in Cats in a Shelter Setting - a Case Series

Five cats were diagnosed with eyelid agenesis in a 6-month period at the Miami-Dade Animal Services, and a total of 9 blepharoplasties were performed using the lip commissure to eyelid transposition flap (LCET) technique. Eyelid agenesis affected 50%-80% of the superiolateral lid in all cats. Postoperatively, partial necrosis of the flap was observed in 4 and partial dehiscence was observed in 1 of the corrected eyelids, occurring where the buccal mucosa was sutured to the conjunctival mucosa. No cats with partial necrosis of the flap were known to have developed trichiasis due to scar tissue formed at the necrotic site. The single case in which dehiscence occurred developed slight trichiasis that may warrant further intervention to ensure permanent hair ablation. Eyelids were cosmetically acceptable and functional at final examination. Patients showed no evidence of initial discomfort at the surgical sites, nor discomfort or progression of corneal disease during the follow-up time. This case series documents a suitable technique to treat cat eyelid agenesis when referral to a specialist is not an option due to lack of resources, such as in shelters or low-cost veterinary clinics. The surgical technique, outcome and complications presented in this case series are evaluated, and discussed.

Identification of missense MAB21L1 variants in microphthalmia and aniridia

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 Q48Sfs*5 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.

Visual Function and Ophthalmological Findings in CHARGE Syndrome: Revision of Literature, Definition of a New Clinical Spectrum and Genotype Phenotype Correlation

CHARGE syndrome (CS) is a rare genetic disease causing multiple anatomical defects and sensory impairment. Visual function is usually reported by caregivers and has never been described with a structured behavioral assessment. Our primary objective was to describe ocular abnormalities, visual function and genotype–ocular-phenotype correlation in CS. A prospective monocentric cohort study was performed on 14 children with CS carrying pathogenic CHD7 variants. All children underwent ophthalmological evaluation and structured behavioral assessment of visual function. The VISIOCHARGE questionnaire was administered to parents. Colobomas were present in 93% of patients. Genotype–phenotype correlation documented mitigated features in a subset of patients with intronic pathogenic variants predicted to affect transcript processing, and severe features in patients with frameshift/nonsense variants predicting protein truncation at the N-terminus. Abnormal visual function was present in all subjects, with different degrees of impairment. A significant correlation was found between visual function and age at assessment (p-value = 0.025). The present data are the first to characterize visual function in CS patients. They suggest that hypomorphic variants might be associated with milder features, and that visual function appears to be related to age. While studies with larger cohorts are required for confirmation, our data indicate that experience appears to influence everyday use of visual function more than ocular abnormalities do.

Cataract surgery in eyes with associated coloboma: Predictors of outcome and safety of different surgical techniques

Purpose:

The aim of this study was to report the outcome of cataract surgery with different surgical techniques in eyes with coexisting coloboma and to define factors of prognostic importance.

Methods:

Retrospective case sheet review of patients presenting between January 2016 and December 2018, who underwent cataract surgery in eyes with coexisting coloboma.

Results:

Of the 3,30,231 cases operated during the study period, 280 eyes of 276 patients had associated colobomatous malformation. The prevalence of coloboma in eyes undergoing cataract surgery was 0.085%. The mean age of the patients was 46.4 years (range 19 - 88 years). Phacoemulsification (PE) was performed in 130 eyes (46.4%), manual small incision cataract surgery (M-SICS) was done in 115 eyes (41.1%), and 35 eyes (12.5%) underwent intra capsular cataract extraction. Intra-operative complications were noted in 26 (9%) eyes. Incidence of intra-operative and post-operative complications was comparable between PE and M-SICS groups (p = 0.94). The mean corrected distance visual acuity (CDVA) improved from logMAR 1.71 ± 0.62 to 0.87 ± 0.61 (p = 0.00009). On multivariate analysis, microcornea (p = 0.002), type 1 and 2 coloboma (p < 0.001), and intraoperative complications (p = 0.001) were associated with poor visual outcome.

Conclusion:

Favorable functional outcomes can be achieved with phacoemulsification in eyes with softer cataract and corneal diameter >8 mm and with M-SICS in eyes with hard cataracts and corneal diameter of 6–8 mm. PE should be considered as the primary choice whenever permissible by the corneal diameter and severity of nuclear sclerosis. Poor functional outcomes were seen in eyes with smaller corneal diameter, extensive chorioretinal coloboma, and intraoperative complications.

The C-Mannosylome of Human Induced Pluripotent Stem Cells Implies a Role for ADAMTS16 C-Mannosylation in Eye Development

C-mannosylation is a modification of tryptophan residues with a single mannose and can affect protein folding, secretion, and/or function. To date, only a few proteins have been demonstrated to be C-mannosylated, and studies that globally assess protein C-mannosylation are scarce. To interrogate the C-mannosylome of human induced pluripotent stem cells, we compared the secretomes of CRISPR–Cas9 mutants lacking either the C-mannosyltransferase DPY19L1 or DPY19L3 to WT human induced pluripotent stem cells using MS-based quantitative proteomics. The secretion of numerous proteins was reduced in these mutants, including that of A Disintegrin And Metalloproteinase with ThromboSpondin Motifs 16 (ADAMTS16), an extracellular protease that was previously reported to be essential for optic fissure fusion in zebrafish eye development. To test the functional relevance of this observation, we targeted dpy19l1 or dpy19l3 in embryos of the Japanese rice fish medaka (Oryzias latipes) by CRISPR–Cas9. We observed that targeting of dpy19l3 partially caused defects in optic fissure fusion, called coloboma. We further showed in a cellular model that DPY19L1 and DPY19L3 mediate C-mannosylation of a recombinantly expressed thrombospondin type 1 repeat of ADAMTS16 and thereby support its secretion. Taken together, our findings imply that DPY19L3-mediated C-mannosylation is involved in eye development by assisting secretion of the extracellular protease ADAMTS16.

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TSR1 of ADAMTS16 can be C-mannosylated.

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Deletion of DPY19L1 or DPY19L3 in hiPSCs caused reduced secretion of ADAMTS16.

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Targeting of dpy19l3 in medaka occasionally led to coloboma.

Biallelic Variants in KIF17 Associated with Microphthalmia and Coloboma Spectrum

Microphthalmia, anophthalmia, and coloboma (MAC) are a group of congenital eye anomalies that can affect one or both eyes. Patients can present one or a combination of these ocular abnormalities in the so called “MAC spectrum”. The KIF17 gene encodes the kinesin-like protein Kif17, a microtubule-based, ATP-dependent, motor protein that is pivotal for outer segment development and disc morphogenesis in different animal models, including mice and zebrafish. In this report, we describe a Sicilian family with two siblings affected with congenital coloboma, microphthalmia, and a mild delay of motor developmental milestones. Genomic DNA from the siblings and their unaffected parents was sequenced with a clinical exome that revealed compound heterozygous variants in the KIF17 gene (NM_020816.4: c.1255C > T (p.Arg419Trp); c.2554C > T (p.Arg852Cys)) segregating with the MAC spectrum phenotype of the two affected siblings. Variants were inherited from the healthy mother and father, are present at a very low-frequency in genomic population databases, and are predicted to be deleterious in silico. Our report indicates the potential co-segregation of these biallelic KIF17 variants with microphthalmia and coloboma, highlighting a potential conserved role of this gene in eye development across different species.

Closing the Gap: Mechanisms of Epithelial Fusion During Optic Fissure Closure

A key embryonic process that occurs early in ocular development is optic fissure closure (OFC). This fusion process closes the ventral optic fissure and completes the circumferential continuity of the 3-dimensional eye. It is defined by the coming together and fusion of opposing neuroepithelia along the entire proximal-distal axis of the ventral optic cup, involving future neural retina, retinal pigment epithelium (RPE), optic nerve, ciliary body, and iris. Once these have occurred, cells within the fused seam differentiate into components of the functioning visual system. Correct development and progression of OFC, and the continued integrity of the fused margin along this axis, are important for the overall structure of the eye. Failure of OFC results in ocular coloboma-a significant cause of childhood visual impairment that can be associated with several complex ocular phenotypes including microphthalmia and anterior segment dysgenesis. Despite a large number of genes identified, the exact pathways that definitively mediate fusion have not yet been found, reflecting both the biological complexity and genetic heterogeneity of the process. This review will highlight how recent developmental studies have become focused specifically on the epithelial fusion aspects of OFC, applying a range of model organisms (spanning fish, avian, and mammalian species) and utilizing emerging high-resolution live-imaging technologies, transgenic fluorescent models, and unbiased transcriptomic analyses of segmentally-dissected fissure tissue. Key aspects of the fusion process are discussed, including basement membrane dynamics, unique cell behaviors, and the identities and fates of the cells that mediate fusion. These will be set in the context of what is now known, and how these point the way to new avenues of research.

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.

Coloboma may be a shared feature in a spectrum of disorders caused by mutations in the WDR37-PACS1-PACS2 axis

We report a male adult with early infantile-onset epilepsy, facial dysmorphism, and iridal and choroidal coloboma who had a de novo heterozygous mutation in PACS2, that is, c.625G > A p.(Glu209Lys). This specific mutation was previously reported in a patient with PACS2-related disorder (early infantile epileptic encephalopathy 66). De novo heterozygous mutations in WDR37 have been shown to cause a novel human disorder, neurooculocardiogenitourinary syndrome (NOCGUS syndrome) (OMIM #618652), characterized by intellectual disability, facial dysmorphism, and coloboma. According to large-scale interactome data, WDR37 interacts most strongly, by far, with PACS1 and PACS2. Clinically, coloboma has been described as a feature in a WDR37-related disorder and a PACS1-related disorder (Schuurs-Hoeijmakers syndrome), but not in a PACS2-related disorder. Our review of the phenotypes of three human disorders caused by WDR37, PACS1, and PACS2 mutations showed a significant overlap of epilepsy, intellectual disability, cerebellar atrophy, and facial features. The present observation of coloboma as a shared feature among these three disorders suggests that this group of genes may be involved in ocular development. We propose that dysregulation of the WDR37-PACS1-PACS2 axis results in a spectrum that is recognizable by intellectual disability, distinctive facial features, and coloboma.

Genetics Underlying the Interactions between Neural Crest Cells and Eye Development

The neural crest is a unique, transient stem cell population that is critical for craniofacial and ocular development. Understanding the genetics underlying the steps of neural crest development is essential for gaining insight into the pathogenesis of congenital eye diseases. The neural crest cells play an under-appreciated key role in patterning the neural epithelial-derived optic cup. These interactions between neural crest cells within the periocular mesenchyme and the optic cup, while not well-studied, are critical for optic cup morphogenesis and ocular fissure closure. As a result, microphthalmia and coloboma are common phenotypes in human disease and animal models in which neural crest cell specification and early migration are disrupted. In addition, neural crest cells directly contribute to numerous ocular structures including the cornea, iris, sclera, ciliary body, trabecular meshwork, and aqueous outflow tracts. Defects in later neural crest cell migration and differentiation cause a constellation of well-recognized ocular anterior segment anomalies such as Axenfeld–Rieger Syndrome and Peters Anomaly. This review will focus on the genetics of the neural crest cells within the context of how these complex processes specifically affect overall ocular development and can lead to congenital eye diseases.

Compound heterozygous splicing CDON variants result in isolated ocular coloboma

Ocular coloboma is caused by failure of optic fissure closure during development and recognized as part of the microphthalmia, anophthalmia, and coloboma (MAC) spectrum. While many genes are known to cause colobomatous microphthalmia, relatively few have been reported in coloboma with normal eye size. Genetic analysis including trio exome sequencing and Sanger sequencing was undertaken in a family with two siblings affected with bilateral coloboma of the iris, retina, and choroid. Pathogenic variants in MAC genes were excluded. Trio analysis identified compound heterozygous donor splice site variants in CDON, a cell-surface receptor known to function in the Sonic Hedgehog pathway, c.928 + 1G > A and c.2650 + 1G > T, in both affected individuals. Heterozygous missense and truncating CDON variants are associated with dominant holoprosencephaly (HPE) with incomplete penetrance and Cdon-/- mice display variable HPE and coloboma. A homozygous nonsense allele of uncertain significance was recently identified in a consanguineous patient with coloboma and a second molecular diagnosis. We report the first compound heterozygous variants in CDON as a cause of isolated coloboma. CDON is the first HPE gene identified to cause recessive coloboma. Given the phenotypic overlap, further examination of HPE genes in coloboma is indicated.

CHARGE syndrome without colobomas: Ophthalmic findings

To report ophthalmic findings of patients without colobomas, and with a clinical and molecular diagnosis of CHARGE Syndrome. Retrospective study of ophthalmic findings in 67 CHARGE patients-clinically confirmed diagnosis with positive CHD7 mutation-seen in the Ophthalmology department of Cincinnati Children's Hospital Medical Center between January 1, 2008 through September 25, 2018. Criteria for inclusion in this study was absence of any form of a coloboma in either eye. In our cohort, all patients had a positive CHD7 mutation, in addition to a clinical diagnosis. 19.4% (13/67) of CHARGE patients did not have a coloboma in either eye. 69.2% (9/13) had strabismus, 76.9% (10/13) had a refractive error that warranted refractive correction, 23.1% (3/13) had amblyopia, 38.5% (5/13) had nasolacrimal duct obstruction, 30.8% (4/13) had dry eye syndrome and exposure keratopathy, 15.4% (2/13) had ptosis, 15.4% (2/13) had blepharitis, 15.4% (2/13) had Cortical Visual Impairment, 7.7% (1/13) of patients had optic nerve drusen, 7.7% (1/13) had Marcus Gunn Jaw Winking, and 7.7% (1/13) with an eyelid nevus. There are numerous ophthalmic findings in individuals with CHARGE Syndrome without colobomas. No study to date has evaluated the ophthalmic findings in CHD7 positive CHARGE patients without colobomas. These findings need to be assessed and treated to ensure optimal vision in the CHARGE patient population. Absence of coloboma does not rule out a diagnosis of CHARGE syndrome, and if there is a clinical suspicion, clinical confirmation then genetic testing would be warranted.

Spotlight on the pediatric eye: a pictorial review of orbital anatomy and congenital orbital pathologies

Orbital lesions in the pediatric population vary from adults in terms of their presentation, unique pathology, and imaging characteristics. The prompt and accurate diagnosis of these lesions is imperative to prevent serious consequences in terms of visual impairment and disfigurement. Along with dedicated ophthalmologic examination, imaging is instrumental in characterizing these lesions, both for accurate diagnosis and subsequent management. In our pictorial essay, we provide a basic review of orbital embryology, anatomy, and congenital orbital pathologies, with emphasis on radiological findings.

Ocular coloboma: Genetic variants reveal a dynamic model of eye development

Ocular coloboma is a congenital disorder of the eye where a gap exists in the inferior retina, lens, iris, or optic nerve tissue. With a prevalence of 2-19 per 100,000 live births, coloboma, and microphthalmia, an associated ocular disorder, represent up to 10% of childhood blindness. It manifests due to the failure of choroid fissure closure during eye development, and it is a part of a spectrum of ocular disorders that include microphthalmia and anophthalmia. Use of genetic approaches from classical pedigree analyses to next generation sequencing has identified more than 40 loci that are associated with the causality of ocular coloboma. As we have expanded studies to include singleton cases, hereditability has been very challenging to prove. As such, researchers over the past 20 years, have unraveled the complex interrelationship amongst these 40 genes using vertebrate model organisms. Such research has greatly increased our understanding of eye development. These genes function to regulate initial specification of the eye field, migration of retinal precursors, patterning of the retina, neural crest cell biology, and activity of head mesoderm. This review will discuss the discovery of loci using patient data, their investigations in animal models, and the recent advances stemming from animal models that shed new light in patient diagnosis.

Protein elongation variant of PUF60: Milder phenotypic end of the Verheij syndrome

The PUF60 gene encodes a ubiquitously expressed essential splicing factor that is recruited to the U2snRNA complex. The complex binds to the 3' splice site of exons in specific target genes and regulates the inclusion or exclusion of such exons. Recently, pathogenic variants of PUF60 have been shown to cause a relatively specific and potentially recognizable pattern of malformation referred to as Verheij syndrome. Here, we report a 12-year-old female patient with a de novo mutation in PUF60 whose phenotype was representative of the milder end of the phenotypic spectrum of Verheij syndrome; the de novo mutation was a frameshift mutation p.(Ser558Cysfs*21) that resulted in the addition of 21 extra amino acids at the carboxy end of the protein. Among the frequent features of Verheij syndrome, the patient exhibited coloboma, cervical spinal segmentation defects, and borderline intellectual functioning, but lacked cardiac abnormalities, deafness, and urogenital abnormalities. The results of RNA analysis using peripheral blood showed the escape of the mutant allele from nonsense-mediated mRNA decay, possibly accounting for the mild phenotype in the presently reported patient. Based on our clinical observations, we inferred that two embryologic processes, closure of the ocular plate and cervical spinal segmentation, are particularly susceptible to deficient PUF60-mediated splicing regulation, compared with other embryogenetic processes leading to the central nervous system, heart, ear, and kidney.

Use of free oral mucosal graft for treatment of feline eyelid agenesis in seven patients

OBJECTIVE

To describe a simple and effective surgery for feline eyelid agenesis.

PROCEDURE

Free oral mucosal grafts were harvested from the upper lips of the surgical patients. A recipient bed was created by incising the conjunctiva at the conjunctival-skin border and opening a space in the tissue with blunt dissection without removal of tissue. The free oral mucosal graft was sutured into the space with simple continuous suture pattern of 7-0 Vicryl.

RESULTS

Eyelids were cosmetically acceptable at final examination, and areas of coloboma appeared less prominent. Patient comfort was improved in all subjects as subjectively noted by decreased blepharospasm. All grafts were successfully incorporated. All patients developed brown-colored crusting over the grafts within days of the surgery, which gradually resolved over a 4- to 6-week period. Three of seven patients developed few trichiatic hairs at the donor-recipient junction, and two of these patients had follow-up cryoepilation.

CONCLUSION

For feline eyelid agenesis, free oral mucosal graft implantation was successful in creating space between fur and cornea with insertion of smooth-surfaced, hairless tissue, alleviating the discomfort of hair contacting the cornea. The extra tissue can also create a small overhang or fold of tissue (pseudo-lid) which may also be protective. For two cases, cryoepilation of few trichiatic hairs at the donor-recipient border was performed at a later date. As illustrated by case 3, use of a long and wide rectangular graft with squared edges is recommended to lessen the chance of trichiasis at lateral or medial edges of recipient-donor junctions.

Identification of a possible association of JAK2 in development of microphthalmia, anophthalmia, and coloboma (MAC) complex in a child with 9p deletion and duplication

BACKGROUND

Microphthalmia, anophthalmia, coloboma (MAC) complex is a spectrum of ocular abnormalities that occur in isolation or as part of a syndrome. Genetic abnormalities have been shown to account for 80% of cases in bilateral anophthalmia or severe microphthalmia, where 25-30% were attributed to chromosomal defects in this subset of MAC patients. To date, chromosome 9 short arm (9p) abnormalities have not been shown to associate with development of MAC.

PURPOSE

To report a case of MAC spectrum disorder that is related to 9p deletion and duplication.

MATERIALS AND METHODS

A child who exhibited signs of MAC was evaluated retrospectively. Genetic analysis with comparative genomic hybridization (CGH) and a family pedigree was obtained from the proband.

RESULTS

A 3-year-old girl with a history of an atrial septal defect, a horseshoe kidney and global developmental delay was presented. Ophthalmic examination revealed bilateral iris coloboma, bilateral choroidal-retinal coloboma, and left-sided microphthalmia. Subsequent oligonucleotide-based array CGH revealed two different sites of duplication and deletion on 9p (9p24.3 (209020_1143516)x1, 9p24.3p24.1 (1158662_6395264)x3).

CONCLUSION

We present the first case of MAC spectrum disorder that is related to 9p deletion and duplication. The link between the associated genetic abnormality and the phenotypic features is yet to be established. Duplication of JAK2 gene, which is within the same region of abnormalities, may have potentiated the development of MAC spectrum disease.

Morphogenesis and axis specification occur in parallel during optic cup and optic fissure formation, differentially modulated by BMP and Wnt

Optic cup morphogenesis is an intricate process. Especially, the formation of the optic fissure is not well understood. Persisting optic fissures, termed coloboma, are frequent causes for congenital blindness. Even though the defective fusion of the fissure margins is the most acknowledged reason for coloboma, highly variable morphologies of coloboma phenotypes argue for a diverse set of underlying pathomechanisms. Here, we investigate optic fissure morphogenesis in zebrafish to identify potential morphogenetic defects resulting in coloboma. We show that the formation of the optic fissure depends on tissue flow movements, integrated into the bilateral distal epithelial flow forming the optic cup. On the temporal side, the distal flow translates into a ventral perpendicular flow, shaping the temporal fissure margin. On the nasal side, however, the distal flow is complemented by tissue derived from the optic stalk, shaping the nasal fissure margin. Notably, a distinct population of TGFβ-signalling positive cells is translocated from the optic stalk into both fissure margins. Furthermore, we show that induced BMP signalling as well as Wnt-signalling inhibition result in morphogenetic defects of the optic fissure. Our data also indicate that morphogenesis is crucial for a proper positioning of pre-specified dorsal–ventral optic cup domains.

A Syrian patient with Steel syndrome due to compound heterozygous COL27A1 mutations with colobomata of the eye

The joint occurrence of short stature, congenital dislocation of the hip, carpal coalition, dislocation of the radial head, cavus deformity, scoliosis, and vertebral anomalies was first described in 1993 by Steel et al. (OMIM #615155) in 23 children from Puerto Rico. The condition is caused by a deficient matrix protein, collagen type XXVII alpha 1 chain, due to bi‐allelic loss of function mutations in the gene COL27A1. Outside of Puerto Rico, only four families have been described, in three of which the patients also had hearing loss. However, structural eye defects have not yet been reported in conjunction with this rare autosomal recessive syndrome. Here, we describe a 9‐year‐old girl born to nonconsanguineous Syrian parents with the characteristic features of Steel syndrome, including short stature, massive malalignment of large joints, kyphoscoliosis, hearing loss, and typical facial dysmorphism. However, she was also born with bilateral colobomata of the irides and choroido‐retinae with unilateral affection of the macula. Whole exome sequencing identified two pathogenic compound heterozygous variants in COL27A1: c.93del, p.(Phe32Leufs*71) and c.3075del, p.(Lys1026Argfs*33). There was no discernible alternative cause for the colobomata. Our findings might indicate an association of this exceptionally rare disorder caused by COL27A1 mutations with developmental defects of the eye from the anophthalmia/microphthalmia/coloboma spectrum.