Eye Malformations Research Articles

A Novel Oculo-Skeletal syndrome with intellectual disability caused by a particular MAB21L2 mutation

We describe a novel recognizable phenotype characterized by anophthalmia, a distinctive skeletal dysplasia and intellectual disability. Radiographic anomalies include severe rhizomelic shortness of the limbs and abnormal joint formation. Recent exome studies showed that these characteristics are part of the phenotypic spectrum of MAB21L2 gene mutations which cause a range of structural eye malformations such as microphthalmia/anophthalmia and ocular coloboma. The two unrelated individuals described here in detail are heterozygous carriers of the same de novo missense mutation c.151C > T (p.Arg51Cys) in MAB21L2.

Biochemical Basis for Dominant Inheritance, Variable Penetrance, and Maternal Effects in RBP4 Congenital Eye Disease

Gestational vitamin A (retinol) deficiency poses a risk for ocular birth defects and blindness. We identified missense mutations in RBP4, encoding serum retinol binding protein, in three families with eye malformations of differing severity, including bilateral anophthalmia. The mutant phenotypes exhibit dominant inheritance, but incomplete penetrance. Maternal transmission significantly increases the probability of phenotypic expression. RBP normally delivers retinol from hepatic stores to peripheral tissues, including the placenta and fetal eye. The disease mutations greatly reduce retinol binding to RBP, yet paradoxically increase the affinity of RBP for its cell surface receptor, STRA6. By occupying STRA6 nonproductively, the dominant-negative proteins disrupt vitamin A delivery from wild-type proteins within the fetus, but also, in the case of maternal transmission, at the placenta. These findings establish a previously uncharacterized mode of maternal inheritance, distinct from imprinting and oocyte-derived mRNA, and define a group of hereditary disorders plausibly modulated by dietary vitamin A.

Prenatal ultrasound charts of orbital total axial length measurement (TAL): a valuable data for correct fetal eye malformation assessment.

To construct prenatal age-specific reference intervals using ultrasound measurement of total axial length (TAL) in normal fetuses for assessing microphthalmia. Prospective cross-sectional study of fetuses assessed at a prenatal ultrasound unit between 2011 and 2014. The study cohort comprised 309 pregnant women attending for routine fetal biometry, viability, or anomaly scan between 14 and 41 weeks of gestation. Only singleton viable fetus with normal anatomy, adequate amniotic fluid, accurate gestational age, and no maternal medical complications of pregnancy were enrolled. Biometric measurements were obtained in the axial plane in all the fetuses. Those measurements and the relevant gestational age were registered in a computerized database. A linear growth function was observed between gestational age and bi-orbital diameter (r(2) = 0.95; p < 0.001), ln (TAL) (r2 = 0.89; p < 0.001), OD (r(2) = 0.86; p < 0.001), and IOD (r2 = 0.79; p < 0.001). Tables showing the 5th, 50th, and 95th centiles of orbital parameters were created based on the reference interval charts. Ultrasound measurement of the fetal TAL ocular distance is feasible. This may assist the multidisciplinary team in the evaluation of fetal eye abnormalities that might be expressed by deviation in TAL.

Encephalocraniocutaneous Lipomatosis: A Rare Association With Tethered Spinal Cord Syndrome With Review of Literature.

Encephalocraniocutaneous lipomatosis or Haberland syndrome is a rare, congenital neurocutaneous syndrome. It is characterized by unilateral lipomatous hamartomata of the scalp, eyelid, and outer globe of the eye and ipsilateral neurologic malformations. We describe the first case from Lebanon, an infant with classical encephalocraniocutaneous lipomatosis characterized by nevus psiloliparus, unilateral right facial and frontal–temporal subcutaneous lipomas, alopecia, ocular coloboma, aniridia and eyelid nodular tags, ventriculomegaly with intracranial and intraspinal lipomas, and tethered spinal cord. We report this case of rare association between encephalocraniocutaneous lipomatosis and tethered spinal cord syndrome and stress on the importance of spinal cord evaluation in encephalocraniocutaneous lipomatosis.

Clinical anophthalmia and coloboma associated with systemic malformations: etiology and ophthalmologist-patient relationship

This report refers to a two years and nine months patient, carrier of clinical anophthalmia in her right eye associated with posterior coloboma in her left eye and systemic malformations. The mother was vaccinated against rubella three months before conception and, at birth, the laboratory tests showed 267 IU/mL for rubella IgG antibodies level and 3,5 IU/mL for cytomegalovirus, being IgM antibodies negative for both. The abnormalities found have characteristics of congenital rubella syndrome (CRS) and congenital cytomegalovirus infection. It can also constitute genetic alteration, derive from other etiologies or present themselves without explanation. The patient’s psychological evaluation was within normal limits, being referred for vision rehabilitation. The mother manifested depressive symptoms, being shown to her specialized treatment. Further studies are needed to clarify the etiology of congenital eye malformations and the holistic cares to be valued during the relationship ophthalmologist-patient.

G.P.320: Phenotypic heterogeneity of the c.919T>A FKRP gene mutation in humans and a mouse model

Mutations in the Fukutin-related protein gene (FKRP) lead to a alpha-dystroglycanopathy, a genetically heterogeneous group of muscular dystrophies associated with a wide range of phenotypes, from a mild Limb-Girdle Muscular Dystrophy (LGMD2I) to a severe congenital muscular dystrophy (CMD) with brain involvement. The aim of this study was to reinforce the scarce data associated with the uncommon c.919T>A missense mutation in order to clarify the genotype-phenotype correlation and to confirm the severity of this mutation. We report a new homozygous patient and reviewed the only 5 patients previously published (4 heterozygous and 1 homozygous). To understand the pathogenesis of the disease, two mice models, one with the mutation alone (FKRPTyr307Asn) and the second with a neomycin cassette (FKRP-NeoTyr307Asn), have been also generated. The two homozygous patients presented at birth with a severe muscle-eye-brain phenotype associated with mental retardation and severe structural eye and CNS involvement, such as lissencephaly and cerebellar hypoplasia. The three heterozygous patients, carrying the common c.826C>A mutation, developed a LGMD milder phenotype: two a Duchenne-like phenotype and one a Becker-like phenotype. The last heterozygous patient carrying a rare c.1012C>T mutation showed a CMD intermediate phenotype with eye and cerebellar malformation, but normal cognitive development. All six patients required early ventilatory support and three died from respiratory complications. All muscle biopsies showed a dystrophic pattern of variable severity. Although the homozygous FKRPTyr307Asn mice had an unexpected normal phenotype, the FKRP-NeoTyr307Asn mice showed a reduction in muscle mass, hypoglycosylation of α -DG, structural defects in eyes and CNS, and died after birth. Taken together, these findings strongly support our previous observations that this mutation is particularly severe when present either in homozygous or in heterozygous with the non-common mutation.

Pleiotropic functions for transcription factor zscan10.

The transcription factor Zscan10 had been attributed a role as a pluripotency factor in embryonic stem cells based on its interaction with Oct4 and Sox2 in in vitro assays. Here we suggest a potential role of Zscan10 in controlling progenitor cell populations in vivo. Mice homozygous for a Zscan10 mutation exhibit reduced weight, mild hypoplasia in the spleen, heart and long bones and phenocopy an eye malformation previously described for Sox2 hypomorphs. Phenotypic abnormalities are supported by the nature of Zscan10 expression in midgestation embryos and adults suggesting a role for Zscan10 in either maintaining progenitor cell subpopulation or impacting on fate choice decisions thereof.

Monoallelic and Biallelic Mutations in MAB21L2 Cause a Spectrum of Major Eye Malformations

We identified four different missense mutations in the single-exon gene MAB21L2 in eight individuals with bilateral eye malformations from five unrelated families via three independent exome sequencing projects. Three mutational events altered the same amino acid (Arg51), and two were identical de novo mutations (c.151C>T [p.Arg51Cys]) in unrelated children with bilateral anophthalmia, intellectual disability, and rhizomelic skeletal dysplasia. c.152G>A (p.Arg51His) segregated with autosomal-dominant bilateral colobomatous microphthalmia in a large multiplex family. The fourth heterozygous mutation (c.145G>A [p.Glu49Lys]) affected an amino acid within two residues of Arg51 in an adult male with bilateral colobomata. In a fifth family, a homozygous mutation (c.740G>A [p.Arg247Gln]) altering a different region of the protein was identified in two male siblings with bilateral retinal colobomata. In mouse embryos, Mab21l2 showed strong expression in the developing eye, pharyngeal arches, and limb bud. As predicted by structural homology, wild-type MAB21L2 bound single-stranded RNA, whereas this activity was lost in all altered forms of the protein. MAB21L2 had no detectable nucleotidyltransferase activity invitro, and its function remains unknown. Induced expression of wild-type MAB21L2 in human embryonic kidney 293 cells increased phospho-ERK (pERK1/2) signaling. Compared to the wild-type and p.Arg247Gln proteins, the proteins with the Glu49 and Arg51 variants had increased stability. Abnormal persistence of pERK1/2 signaling in MAB21L2-expressing cells during development is a plausible pathogenic mechanism for the heterozygous mutations. The phenotype associated with the homozygous mutation might be a consequence of complete loss of MAB21L2 RNA binding, although the cellular function of this interaction remains unknown.

Comparative Proteomics and Expression Analysis of Five Genes in Epicauta chinensis Larvae from the First to Fifth Instar

Blister beetle is an important insect model for both medicinal and pure research. Previous research has mainly focused on its biology and biochemistry, but very little data is yet available in the molecular biology. This study uses differential proteomics technology to analyze the soluble proteins extracted from each of the 5 instars larvae of Epicauta chinensis. 42 of the differentially-expressed proteins were identified successfully by MALDI-TOF/TOF-MS. Some of these proteins’ function and their expression profiles are analyzed. Our analysis revealed dynamics regulation of the following proteins: Axin-like protein pry-1 (APR-1), dihydrolipoyl dehydrogenase (DLD), vitellogenin (Vg) and lysozyme C (Lmz-S). APR-1 negatively regulates the Wnt signaling pathway. Its overexpression could result in embryo, leg, eye and ovary ectopica or malformation. DLD catalyzes the pyruvate into acetyl-CoA, the latter is the starting material of juvenile hormone (JH) and ipsdienol biosynthesis through the MVA pathway in insects. While Vg synthesis can be regulated by JH and stimulated by food factors. So DLD may affect the synthesis of JH, ipsdienol and Vg indirectly. The activity of lysozyme is an indicator of the immunity. Nutrition/food should be taken into account for its potential role during the development of larva in the future. Among the five genes and their corresponding proteins’ expression, only hsc70 gene showed a good correspondence with the protein level. This reflects the fluctuating relationship between mRNA and protein levels.

Optix defines a neuroepithelial compartment in the optic lobe of the Drosophila brain.

BackgroundDuring early brain development, the organisation of neural progenitors into a neuroepithelial sheet maintains tissue integrity during growth. Neuroepithelial cohesion and patterning is essential for orderly proliferation and neural fate specification. Neuroepithelia are regionalised by the expression of transcription factors and signalling molecules, resulting in the formation of distinct developmental, and ultimately functional, domains.ResultsWe have discovered that the Six3/6 family orthologue Optix is an essential regulator of neuroepithelial maintenance and patterning in the Drosophila brain. Six3 and Six6 are required for mammalian eye and forebrain development, and mutations in humans are associated with severe eye and brain malformation. In Drosophila, Optix is expressed in a sharply defined region of the larval optic lobe, and its expression is reciprocal to that of the transcription factor Vsx1. Optix gain- and loss-of-function affects neuroepithelial adhesion, integrity and polarity. We find restricted cell lineage boundaries that correspond to transcription factor expression domains.ConclusionWe propose that the optic lobe is compartmentalised by expression of Optix and Vsx1. Our findings provide insight into the spatial patterning of a complex region of the brain, and suggest an evolutionarily conserved principle of visual system development.

Focal dermal hypoplasia without focal dermal hypoplasia

Focal dermal hypoplasia (FDH; Goltz-Gorlin syndrome) is an X-linked dominant disorder affecting mainly tissues of ectodermal and mesodermal origin. The phenotype is characterized by hypoplastic linear skin lesions, eye malformations, hair and teeth anomalies, and multiple limbs malformations. The disorder is caused by PORCN mutations. Here we describe a mother and daughter with FDH in whom a c.938T>G in PORCN was detected. Neither of the two had FDH, but otherwise the phenotype was classical. Focal skin hypoplasia is a hallmark of FDH but the present family indicates that FDH should also be considered in absence of this skin manifestation.

A Trans-Acting Protein Effect Causes Severe Eye Malformation in the Mp Mouse

Mp is an irradiation-induced mouse mutation associated with microphthalmia, micropinna and hind limb syndactyly. We show that Mp is caused by a 660 kb balanced inversion on chromosome 18 producing reciprocal 3-prime gene fusion events involving Fbn2 and Isoc1. The Isoc1-Fbn2 fusion gene (Isoc1Mp) mRNA has a frameshift and early stop codon resulting in nonsense mediated decay. Homozygous deletions of Isoc1 do not support a significant developmental role for this gene. The Fbn2-Isoc1 fusion gene (Fbn2 Mp) predicted protein consists of the N-terminal Fibrillin-2 (amino acids 1–2646, exons 1–62) lacking the C-terminal furin-cleavage site with a short out-of-frame extension encoded by the final exon of Isoc1. The Mp limb phenotype is consistent with that reported in Fbn2 null embryos. However, severe eye malformations, a defining feature of Mp, are not seen in Fbn2 null animals. Fibrillin-2Mp forms large fibrillar structures within the rough endoplasmic reticulum (rER) associated with an unfolded protein response and quantitative mass spectrometry shows a generalised defect in protein secretion in conditioned media from mutant cells. In the embryonic eye Fbn2 is expressed within the peripheral ciliary margin (CM). Mp embryos show reduced canonical Wnt-signalling in the CM – known to be essential for ciliary body development - and show subsequent aplasia of CM-derived structures. We propose that the Mp “worse-than-null” eye phenotype plausibly results from a failure in normal trafficking of proteins that are co-expressed with Fbn2 within the CM. The prediction of similar trans-acting protein effects will be an important challenge in the medical interpretation of human mutations from whole exome sequencing.

Disruption of Autoregulatory Feedback by a Mutation in a Remote, Ultraconserved PAX6 Enhancer Causes Aniridia

The strictly regulated expression of most pleiotropic developmental control genes is critically dependent on the activity of long-range cis-regulatory elements. This was revealed by the identification of individuals with a genetic condition lacking coding-region mutations in the gene commonly associated with the disease but having a variety of nearby chromosomal abnormalities, collectively described as cis-ruption disease cases. The congenital eye malformation aniridia is caused by haploinsufficiency of the developmental regulator PAX6. We discovered a de novo point mutation in an ultraconserved cis-element located 150 kb downstream from PAX6 in an affected individual with intact coding region and chromosomal locus. The element SIMO acts as a strong enhancer in developing ocular structures. The mutation disrupts an autoregulatory PAX6 binding site, causing loss of enhancer activity, resulting in defective maintenance of PAX6 expression. These findings reveal a distinct regulatory mechanism for genetic disease by disruption of an autoregulatory feedback loop critical for maintenance of gene expression through development.

Clinical Features and Molecular Characterization of a Patient With Muscle-Eye-Brain Disease

Muscle-eye-brain disease is a congenital muscular dystrophy characterized by structural brain and eye defects. Here, we describe a 12-year-old boy with partial agenesis of corpus callosum, ventriculomegaly, flattened brain stem, diffuse pachygyria, blindness, profound cognitive deficiencies, and generalized muscle weakness, yet without a clear dystrophic pattern on muscle biopsy. There was no glycosylation of α-dystroglycan and the genetic screening revealed a novel truncating mutation, c.1545delC (p.Tyr516Thrfs*21), and a previously identified missense mutation, c.1469G>A (p.Cys490Tyr), in the protein O-mannose beta-1,2-N-acetylglucosaminyltransferase 1 (POMGNT1) gene. These findings broaden the clinical spectrum of muscle-eye-brain disease to include pronounced hypotonia with severe brain and eye malformations, yet with mild histopathologic changes in the muscle specimen, despite the absence of glycosylated α-dystroglycan.

Graded Otx2 activities demonstrate dose-sensitive eye and retina phenotypes

In the human, mutations of OTX2 (Orthodenticle homeobox 2 transcription factor) translate into eye malformations of variable expressivity (even between the two eyes of the same individual) and incomplete penetrance, suggesting the existence of subtle thresholds in OTX2 activity. We have addressed this issue by analyzing retinal structure and function in six mutant mice with graded Otx2 activity: Otx2(+/+), Otx2(+/AA), Otx2(+/GFP), Otx2(AA/AA), Otx2(AA/GFP) and Otx2(GFP/GFP). Null mice (Otx2(GFP/GFP)) fail to develop the head and are embryonic lethal, and compound heterozygous Otx2(AA/GFP) mice show a truncated head and die at birth. All other genotypes develop until adulthood. We analyzed eye structure and visual physiology in the genotypes that develop until adulthood and report that phenotype severity parallels Otx2 activity. Otx2(+/AA) are only mildly affected whereas Otx2(+/GFP) are more affected than Otx2(+/AA) but less than Otx2(AA/AA) mice. Otx2(AA/AA) mice later manifest the most severe defects, with variable expressivity. Electrophysiological and histological analyses of the mouse retina revealed progressive death of bipolar cells and cone photoreceptors that is both Otx2 activity- and age-dependent with the same ranking of phenotypic severity. This study demonstrates the importance of gene dosage in the development of age-dependent pathologies and underscores the fact that small gene dosage differences can cause significant pathological states.

A homozygous mutation in a consanguineous family consolidates the role of ALDH1A3 in autosomal recessive microphthalmia

Anomalies of eye development can lead to the rare eye malformations microphthalmia and anophthalmia (small or absent ocular globes), which are genetically very heterogeneous. Several genes have been associated with microphthalmia and anophthalmia, and exome sequencing has contributed to the identification of new genes. Very recently, homozygous variations within ALDH1A3 have been associated with autosomal recessive microphthalmia with or without cysts or coloboma, and with variable subphenotypes of developmental delay/autism spectrum disorder in eight families. In a consanguineous family where three of the five siblings were affected with microphthalmia/coloboma, we identified a novel homozygous missense mutation in ALDH1A3 using exome sequencing. Of the three affected siblings, one had intellectual disability and one had intellectual disability and autism, while the last one presented with normal development. This study contributes further to the description of the clinical spectrum associated with ALDH1A3 mutations, and illustrates the interfamilial clinical variation observed in individuals with ALDH1A3 mutations.

160 kb deletion in ISPD unmasking a recessive mutation in a patient with Walker–Warburg syndrome

Walker–Warburg syndrome (WWS) is a severe muscular dystrophy with eye and brain malformations. On a molecular level, WWS is a disorder of the O-linked glycosylation of α-dystroglycan and therefore referred to as one of the dystroglycanopathies. The disease family of muscular dystrophy–dystroglycanopathy (MDDG) contains a spectrum of severe to mild disorders, designated as MDDG type A to C. WWS, as the most severe manifestation, corresponds to MDDG type A. Defects in the genes POMT1, POMT2, POMGNT1, FKTN, FKRP, LARGE, GTDC2, G3GALNT2, GMPPB, B3GNT1, TMEM5 and COL4A1 and ISPD have been described as causal for several types of MDDG including WWS, but can only be confirmed in about 60–70% of the clinically diagnosed individuals. The proteins encoded by these genes are involved in the posttranslational modification of α-dystroglycan. Mutations in POMT1, POMT2, POMGNT1, FKTN, FKRP, LARGE, GMPPB, TMEM5 and COL4A1 and ISPD lead to a wide spectrum of phenotypes of congenital muscular dystrophies with or without eye and brain abnormalities. Patients with WWS frequently demonstrate a complete lack of psychomotor development, severe eye malformations, cobblestone lissencephaly and a hypoplastic cerebellum and brainstem, seizures, hydrocephalus and poor prognosis. Here, we present a boy with WWS who showed compound heterozygous changes in ISPD and discuss the clinical and radiological phenotype and the molecular genetic findings, including a novel pathogenic mutation in ISPD.

Anophthalmia and microphthalmia: A clinical case with a prenatal diagnosis

IntroductionAnophthalmia and microphthalmia are serious eye malformations that describe, respectively, the absence of an eye and the presence of a small eye within the orbit. These conditions are the most frequent congenital eye malformations in the newborn, and the precise aetiology remains unknown, but they may occur in isolation or as part of a syndrome, with chromosomal, monogenic and environmental causes already identified. The pre- and post-natal diagnosis can be made using imaging techniques and genetic analysis. The authors present a clinical case diagnosed prenatally. Case reportA 35 year-old primiparous woman, with normal first trimester examinations and karyotype 46,XX, in whom the ultrasound at 18/23 weeks revealed an asymmetry of ocular globes, with a small diameter of the left orbit. This study was complemented with foetal magnetic resonance that confirmed a severe microphthalmia in the left eye, with difficulty in observing the integrity of the optic nerve. The interruption of the pregnancy was discussed, but the parents did not want this. The remaining routine examinations were normal. The pregnancy was terminated at 37 weeks, palpebral closure with absence of ocular globe of the left eye and opacification of cornea and microphthalmia in the right eye was confirmed. ConclusionThis case shows that a difficult diagnosis of a rare pathology can be made in utero by ultrasound. However, some are impossible to diagnosis, and this must be explained to parents.

Maternal folic acid–deficient diet causes congenital malformations in the mouse eye

The eye is a very complex structure derived from the neural tube, surface ectoderm, and migratory mesenchyme from a neural crest origin. Because structures that evolve from the neural tube may be affected by a folate/folic acid (FA) deficiency, the aim of this work was to investigate whether a maternal folic acid-deficient diet may cause developmental alterations in the mouse eye. Female C57BL/6J mice (8 weeks old) were assigned into two different folic acid groups for periods ranging between 2 and 16 weeks. Animals were killed at gestation day 17. Hepatic folate was analyzed, and the eyes from 287 fetuses were macroscopically studied, sectioned and immunolabeled with anti-transforming growth factor (TGF)-β2 and anti-TGF-βRII. Mice exposed to a FA-deficient diet exhibited numerous eye macroscopic anomalies, such as anophthalmia and microphthalmia. Microscopically, the eye was the most affected organ (43.7% of the fetuses). The highest incidence of malformations occurred from the 8th week onward. A statistically significant linear association between the number of maternal weeks on the FA-deficient diet and embryonic microscopic eye malformations was observed. The optic cup derivatives and structures forming the eye anterior segment showed severe abnormalities. In addition, TGF-β2 and TGF-βRII expression in the eye was also altered. This study suggests that an adequate folic acid/folate status plays a key role in the formation of ocular tissues and structures, whereas a vitamin deficiency is negatively associated with a normal eye development even after a short-term exposure.

Goldenhar's Syndrome: A Case Series With Literature Review and Update

Goldenhar's syndrome is a birth defect resulting from the mal-development of the first two branchial arches, with incomplete development of the ear, nose, soft palate, lip and mandible. The phenotype is highly variable. The classic triad is mandibular hypoplasia resulting in facial asymmetry, ear and/or eye malformation, and vertebral anomalies.