Localization of a gene for Duane retraction syndrome to chromosome 2q31

Relationship between retraction and refraction values in patients with Duane's retraction syndrome

PURPOSE

To evaluate refractive findings in patients with unilateral Duane's retraction syndrome (DRS).

METHODS

This retrospective study included 40 patients followed for unilateral DRS. Detailed ophthalmological examinations of the patients were performed. The spherical and cylindrical refractive error, spherical equivalent, and type of refractive error in the eyes with DRS and the fellow eyes were determined. The patients were divided into three subgroups according to their type of DRS. The refractive properties of the eyes with DRS were examined in subgroup analyses. Eye movement limitation was graded between +1 and +4 and compared according to the refractive error type.

RESULTS

The mean age of the patients was 16.8±12.6 (range, 1-60) years. Of the eyes with DRS, 11 (27.5%) were emmetropic, four (10%) were hyperopic, two (5%) were myopic, 11 (27.5%) were myopic astigmatic, and 12 (30.0%) were hyperopic astigmatic. There was no statistically significant difference between the eyes with DRS and fellow eyes in relation to the spherical or cylindrical refractive errors or spherical equivalent (P>0.05 for all). The refraction values for the patients with type 1, type 2 and type 3 DRS were similar between groups (P>0.05). No statistically significant difference was detected in the degree of eye movement limitation according to refractive status (P>0.05).

CONCLUSION

In patients with unilateral DRS, there was no significant difference between the affected eyes and the fellow eyes in terms of refractive error values or types. Refractive status did not significantly differ according to the degree of eye movement limitation. Therefore, although extraocular muscles are affected by DRS, there may not be any significant refractive changes.

Two novel CHN1 variants identified in Duane retraction syndrome pedigrees disrupt development of ocular motor nerves in zebrafish

Duane retraction syndrome (DRS) is a rare congenital eye movement disorder causing by the dysplasia of abducens nerve, and has highly variable phenotype. MRI can reveal the endophenotype of DRS. Most DRS cases are sporadical and isolated, while some are familial or accompanied by other ocular disorders and systemic congenital abnormalities. CHN1 was the most common causative gene for familial DRS. Until now, 13 missense variants of CHN1 have been reported. In this study, we enrolled two unrelated pedigrees with DRS. Detailed clinical examinations, MRI, and the whole exome sequencing (WES) were performed to reveal their clinical and genetic characteristics. Patients from pedigree-1 presented with isolated DRS, and a novel heterozygous variant c.650 A > G, p. His217Arg was identified in CHN1 gene. Patients from pedigree-2 presented with classic DRS and abnormalities in auricle morphology, and the pedigree segregated another novel heterozygous CHN1 variant c.637 T > C, p. Phe213Leu. A variety of bioinformatics software predicted that the two variants had deleterious or disease-causing effects. After injecting of two mutant CHN1 mRNAs into zebrafish embryos, the dysplasia of ocular motor nerves (OMN) was observed. Our present findings expanded the phenotypic and genotypic spectrum of CHN1 related DRS, as well as provided new insights into the role of CHN1 in OMN development. Genetic testing is strongly recommended for patients with a DRS family history or accompanying systemic congenital abnormalities.

Identifying novel disease genes and revealing the pathomechanism of monogenic diseases

Diseases are caused by genetic and/or environmental factors. It is important to understand the pathomechanism of monogenic diseases that are caused only by genetic factors, especially prenatal- or childhood-onset diseases for pediatricians. Identifying "novel" disease genes and elucidating how genomic changes lead to human phenotypes would develop new therapeutic approaches for rare diseases for which no fundamental cure has yet been established. Genomic analysis has evolved along with the development of analytical techniques, from Sanger sequencing (first-generation sequencing) to techniques such as comparative genomic hybridization, massive parallel short-read sequencing (using a next-generation sequencer or second-generation sequencer) and long-read sequencing (using a next-next generation sequencer or third-generation sequencer). I have been researching human genetics using conventional and new technologies, together with my mentors and numerous collaborators, and have identified genes responsible for more than 60 diseases. Here, an overview of genomic analyses of monogenic diseases that aims to identify novel disease genes, and several examples using different approaches depending on the disease characteristics are presented.

A Chinese family with cat eye syndrome and abnormality of eye movement: First case report

Background

Cat eye syndrome (CES) is a rare disease with a wide spectrum of phenotypic variability that is observed in 1:150,000 newborns. CES is characterized clinically by the combination of iris coloboma, anal atresia, and preauricular tags and/or pits. Many eye malformations have been reported to be associated with CES, such as iris and chorioretinal coloboma. However, an abnormality of eye movement has not been previously reported.

Case presentation

We report on a Chinese family carrying a 22q11.1-q11.21 duplication of 1.7Mb tetrasomy (chr22:16,500,000-18,200,000, hg38) in two generations. Based on the proband and her father's clinical manifestations, including ophthalmological examination, cytogenetic analysis, FISH, CNV-seq, and WES, the diagnosis of CES with an abnormality of eye movement was made.

Conclusion

Our findings broadened the symptom spectrum of CES syndrome and laid the foundation for pathogenesis, diagnostic targets, and drug research on the abnormality of eye movement, and were helpful for early diagnosis and intervention of CES.

CHN1 is a Novel Prognostic Marker for Diffuse Large B-Cell Lymphoma

Purpose

Diffuse large B-cell lymphoma (DLBCL) is the most common B-cell malignancy. Thirty to forty percent of DLBCL patients still experience relapse or develop refractory disease even with standard immunochemotherapy, leading to a poor prognosis. Currently, although several gene-based classification methods can be used to predict the prognosis of DLBCL, some patients are still unable to be classified. This study was performed to identify a novel prognostic biomarker for DLBCL.

Patients and Methods

A total of 1850 B-cell non-Hodgkin lymphoma (B-NHL) patients in 8 independent datasets with microarray gene expression profiles were retrieved from the Gene Expression Omnibus (GEO) database and Lymphoma/Leukemia Molecular Profiling Project (LLMPP). The candidate genes were selected through three filters in a strict pipeline. Survival analysis was performed in two independent datasets of patients with both gene expression data and clinical information. Gene set enrichment analysis (GSEA) and the CIBERSORT algorithm were used to explore the biological functions of the genes.

Results

We identified 6 candidate genes associated with the clinical outcome of DLBCL patients: CHN1, CD3D, CLU, ICOS, KLRB1 and LAT. Unlike the other five genes, CHN1 has not been previously reported to be implicated in lymphoma. We also observed that CHN1 had prognostic significance in important clinical subgroups; in particular, high CHN1 expression was significantly related to good outcomes in DLBCL patients with the germinal center B-cell-like (GCB) subtype, stage III–IV, or an International Prognostic Index (IPI) score > 2. Multivariate Cox regression analysis of the two datasets showed that CHN1 was an independent prognostic factor for DLBCL. Additionally, GSEA and CIBERSORT indicated that CHN1 was correlated with cell adhesion and T cell immune infiltration.

Conclusion

Our data indicate for the first time that high CHN1 expression is associated with favorable outcomes in DLBCL patients, suggesting its potential utility as a prognostic marker in DLBCL.

CHN1 and duane retraction syndrome: Expanding the phenotype to cranial nerves development disease

Duane retraction syndrome is a congenital eye movement disorder characterized by a failure of abducens nerve to develop normally, resulting in restriction or absence of abduction, adduction, or both, and narrowing of the palpebral fissure and retraction of the globe on attempted adduction. There is a genetic heterogeneity in Duane retraction syndrome (DURS). DURS maps to chromosome 8q13 in some patients, and pathogenic variants in CHN1 and MAFB genes are known to lead to DURS. We report here a child and his father with Duane retraction syndrome, associated to swallowing difficulties and unilateral trapeze aplasia. A whole exome sequencing revealed a heterozygous missense variant in CHN1 gene. This gene encodes GTPase-activating protein and is involved in the assembly of neuronal locomotor circuits. A patient with a 8q deletion has previously been described with a Duane retraction syndrome associated to trapeze aplasia. We provide an additional description to support the role in cranial nerves development of the CHN1 gene.

Identification of a novel CHN1 p.(Phe213Val) variant in a large Han Chinese family with congenital Duane retraction syndrome

Duane retraction syndrome (DRS) is a neuromuscular dysfunction of the eyes. Although many causative genes of DRS have been identified in Europe and the United States, few reports have been published in regard to Chinese DRS. The aim of the present study was to explore the genetic defect of DRS in a Chinese family. Exome sequencing was used to identify the disease-causing gene for the two affected family members. Ophthalmic and physical examinations, as well as genetic screenings for variants in chimerin 1 (CHN1), were performed for all family members. Functional analyses of a CHN1 variant in 293T cells included a Rac-GTP activation assay, α2-chimaerin translocation assay, and co-immunoprecipitation assay. Genetic analysis revealed a NM_001822.7: c.637T > G variant in the CHN1 gene, which resulted in the substitution of a highly conserved C1 domain with valine at codon 213 (NP_001813.1: p.(Phe213Val)) (ClinVar Accession Number: SCV001335305). In-silico analysis revealed that the p.(Phe213Val) substitution affected the protein stability and connections among the amino acids of CHN1 in terms of its tertiary protein structure. Functional studies indicated that the p.(Phe213Val) substitution reduced Rac-GTP activity and enhanced membrane translocation in response to phorbol-myristoyl acetate (PMA). Together with previous studies, our present findings demonstrate that CHN1 may be an important causative gene for different ethnicities with DRS.

Duane retraction syndrome in a patient with abnormal head position

Duane's syndrome is a rare retraction anomaly characterized by an innervation defect in the lateral rectus muscle, limitation of abduction and adduction due to the result of abnormal innervation of the horizontal rectus muscles, changes in the eyelid fissures, and abnormal vertical eye movements. The affected eye is displaced up and/or down in adduction. This syndrome, also known as Stilling-Turk-Duane syndrome, accounts for approximately 1 to 5% of all strabismus cases. In this article, we present a one-and-a-half-year-old male patient who had abnormal head position, and was diagnosed as having Duane retraction syndrome. Through this study, we want to draw attention to Duane retraction syndrome, which is one of the rare causes of strabismus.

CHN1 gene mutation analysis in patients with Duane retraction syndrome

PURPOSE

To investigate CHN1 (chimerin 1) gene mutations in patients with isolated nonsyndromic Duane syndrome and accompanying positive familial history, bilaterality, or various systemic disorders.

METHODS

Patients with Duane retraction syndrome (DRS) and a positive family history of congenital ocular motility disturbance or bilateral involvement or accompanying any congenital disorder(s) seen consecutively at a single center from 2013 to 2016 were enrolled. All subjects underwent full ophthalmologic examination, including refraction, best-corrected visual acuity, ocular alignment and motility, globe retraction, and biomicroscopic or fundus evaluation. DNA samples were investigated by direct sequencing of the coding regions of the CHN1 gene.

RESULTS

A total of 30 patients (15 males) were included (mean age, 11.8 ± 10.4 years; range, 2-45 years): 8 cases presented with bilateral DRS; 22, with unilateral DRS. Family history of ocular motility abnormality was positive in 16 patients. Eleven cases had an additional congenital disorder. In 2 patients, 2 different mutations were detected in the CHN1 gene: p.E313K (c.937G>A) and p.N224S (c.671A>G).

CONCLUSIONS

CHN1 mutations were identified in 2 bilateral cases and in 1 parent of 1 affected case. One mutation is novel and occurred with additional vertical gaze abnormalities. Additional genetic studies evaluating chimerin 1 (CHN1) and its role in the development of the ocular motor axis are needed to provide new data about these mutations and phenotypic variations.

Duane retraction syndrome: causes, effects and management strategies

Duane retraction syndrome (DRS) is a congenital eye movement anomaly characterized by variable horizontal duction deficits, with narrowing of the palpebral fissure and globe retraction on attempted adduction, occasionally accompanied by upshoot or down-shoot. The etiopathogenesis of this condition can be explained by a spectrum of mechanical, innervational, neurologic and genetic abnormalities occurring independently or which influence each other giving rise to patterns of clinical presentations along with a complex set of ocular and systemic anomalies. Huber type I DRS is the most common form of DRS with an earlier presentation, while Huber type II is the least common presentation. Usually, patients with unilateral type I Duane syndrome have esotropia more frequently than exotropia, those with type II have exotropia and those with type III have esotropia and exotropia occurring equally common. Cases of bilateral DRS may have variable presentation depending upon the type of presentation in each eye. As regards its management, DRS classification based on primary position deviation as esotropic, exotropic or orthotropic is more relevant than Huber’s classification before planning surgery. Surgical approach to these patients is challenging and must be individualized based on the amount of ocular deviation, abnormal head position, associated globe retraction and overshoots.

Management of Duane retraction syndrome with prismatic glasses

PURPOSE

To report the results of using prismatic glasses for Duane retraction syndrome (DRS).

METHODS

Data were obtained from the records of patients who were evaluated during the year 2000 in the Strabismus Unit of the Beyoglu Eye Training and Research Hospital. The average follow-up was 12.2±17.7 months. In all cases, 2 main variables were evaluated: horizontal deviation in the primary position and face turn. Prismatic glasses were provided to patients according to the degree of shift in the primary position.

RESULTS

The mean age of patients was 11.2 years. An analysis was performed on the data collected from 12 cases; 7 patients were females (58.3%) and 5 were males (41.7%), with 11 (91.7%) cases being of type I DRS. All 12 patients had abnormal head posture (face turn) and an angle of mean deviation equaling 10 PD (prism dioptri).

CONCLUSION

Treatment was individualized on a case-by-case basis. Prismatic glasses are useful for eliminating abnormal head posture and ocular misalignment in selected cases.

Clinical presentation and management of congenital ptosis

Congenital ptosis is a rare condition characterized by lower positioning of the upper eyelid that is present at birth and is a clinical condition that is persistent if not treated. It may be unilateral or bilateral and may be associated with other ocular disorders or systemic conditions, including Marcus Gunn, Horner, and Duane syndromes. It is a benign condition but causes functional, cosmetic, and psychological problems in children. However, not all patients need to undergo surgery, and usually only patients at risk of amblyopia need a prompt surgical correction, while in other cases, surgery can be postponed. The grade of ptosis, the eyelid function, and the amblyopic risk are the parameters that affect the ophthalmologist’s decision on timing of surgery and the surgical technique to be used. In fact, there are several types of surgical techniques to correct a congenital ptosis, although very often more than one is needed to obtain an acceptable result. This paper reviews the causes of congenital ptosis and associated diseases. Particular emphasis is given to surgical management and different procedures available to correct the upper eyelid anomaly and avoid permanent damage to visual function.

Congenital cranial dysinnervation disorders

The European Neuromuscular Centre (ENMC) derived the term Congenital Cranial Dysinnervation Disorders in 2002 at an international workshop for a group of congenital neuromuscular diseases. CCDDs are congenital, non-progressive ophthalmoplegia with restriction of globe movement in one or more fields of gaze. This group of sporadic and familial strabismus syndromes was initially referred to as the 'congenital fibrosis syndromes' because it was assumed that the primary pathologic process starts in the muscles of eye motility. Over the last few decades, evidence has accumulated to support that the primary pathologic process of these disorders is neuropathic rather than myopathic. This is believed that for normal development of extra ocular muscles and for preservation of muscle fiber anatomy, normal intra-uterine development of the innervation to these muscles is essential. Congenital dysinnervation to these EOMs can lead to abnormal muscle structure depending upon the stage and the extent of such innervational defects. Over last few years new genes responsible for CCDD have been identified, permitting a better understanding of associated phenotypes, which can further lead to better classification of these disorders. Introduction of high-resolution MRI has led to detailed study of cranial nerves courses and muscles supplied by them. Thus, due to better understanding of pathophysiology and genetics of CCDDs, various treatment modalities can be developed to ensure good ocular alignment and better quality of life for patients suffering from the same.

The genetic basis of incomitant strabismus: consolidation of the current knowledge of the genetic foundations of disease

In recent years, our understanding of the genetic foundations of incomitant strabismus has grown significantly. Much new understanding has been gleaned since the concept of congenital cranial dysinnervation disorders (CCDDs) was introduced in 2002, and the genetic basis of CCDDs continues to be elucidated. In this review, we aim to provide an update of the genetic and clinical presentation of these disorders. Disorders reviewed include Duane syndrome (DS), HOXA1 and HOXB1 syndromes, Moebius syndrome, congenital fibrosis of the extraocular muscles (CFEOM), and horizontal gaze palsy with progressive scoliosis (HGPPS).

Strabismus genetics across a spectrum of eye misalignment disorders

Eye misalignment, called strabismus, is amongst the most common phenotypes observed, occurring in up to 5% of individuals in a studied population. While misalignment is frequently observed in rare complex syndromes, the majority of strabismus cases are non-syndromic. Over the past decade, genes and pathways associated with syndromic forms of strabismus have emerged, but the genes contributing to non-syndromic strabismus remain elusive. Genetic testing for strabismus risk may allow for earlier diagnosis and treatment, as well as decreased frequency of surgery. We review human and model organism literature describing non-syndromic strabismus, including family, twin, linkage, and gene expression studies. Recent advances in the genetics of Duane retraction syndrome are considered, as relatives of those impacted show elevated familial rates of non-syndromic strabismus. As whole genome sequencing efforts are advancing for the discovery of the elusive strabismus genes, this overview is intended to support the interpretation of the new findings.

Diversified clinical presentations associated with a novel sal-like 4 gene mutation in a Chinese pedigree with Duane retraction syndrome

PURPOSE

To determine the underlying genetic cause of Duane retraction syndrome (DRS) in a non-consanguineous Chinese Han family.

METHODS

Detailed ophthalmic and physical examinations were performed on all members from a pedigree with DRS. All exons and their adjacent splicing junctions of the sal-like 4 (SALL4) gene were amplified with polymerase chain reaction and analyzed with direct sequencing in all the recruited family members and 200 unrelated control subjects.

RESULTS

Clinical examination revealed a broad spectrum of phenotypes in the DRS family. Mutation analysis of SALL4 identified a novel heterozygous duplication mutation, c.1919dupT, which was completely cosegregated with the disease in the family and absent in controls. This mutation was predicted to cause a frameshift, introducing a premature stop codon, when translated, resulting in a truncated SALL4 protein, i.e., p.Met640IlefsX25. Bioinformatics analysis showed that the affected region of SALL4 shared a highly conserved sequence across different species. Diversified clinical manifestations were observed in the c.1919dupT carriers of the family.

CONCLUSIONS

We identified a novel truncating mutation in the SALL4 gene that leads to diversified clinical features of DRS in a Chinese family. This mutation is predicted to result in a truncated SALL4 protein affecting two functional domains and cause disease development due to haploinsufficiency through nonsense-mediated mRNA decay.

Simultaneous occurrence of duane retraction syndrome with marfan syndrome

Marfan syndrome (MFS) is an autosomal dominant disorder of connective tissue, while Duane retraction syndrome (DRS) is a congenital cranial dysinnervation disorder (CCDD) which can be transmitted as autosomal dominant disorder in 5–10% of patients. In this paper, we present an 8-year-old girl who presented with left eye DRS and bilateral subluxation of the lens associated with MFS in absence of familial involvement. To our knowledge this is the first case report of DRS with MFS. The occurrence of these syndromes together is very rare and appears to be coincidental.

Imaging findings in congenital cranial dysinnervation disorders

In 2002, the term congenital cranial dysinnervation disorders (CCDDs) was proposed to group heterogeneous syndromes with congenital abnormalities of ocular muscle and facial innervations. The concept of neurogenic etiology has been supported by discovery of genes that are essential to the normal development of brainstem, cranial nerves, and their axonal connections. The CCDDs include Duane retraction syndrome, congenital fibrosis of the extraocular muscles, Möbius syndrome, horizontal gaze palsy with progressive scoliosis, the human homeobox-related disorders, pontine cap tegmental dysplasia, and an expanding list. The purpose of this review was to update the imaging features, as well as clinical and genetic information, regarding cases of CCDDs.

Congenital innervation dysgenesis syndrome (CID)/congenital cranial dysinnervation disorders (CCDDs)

Congenital loss of innervation to the extra-ocular muscles (EOMs) can have a profound effect on the target muscle. This has been well recognised in Duane's retraction syndrome. However, it has been less emphasised in other congenital oculo-motor disorders. Such congenital ocular motor defects have been expanded to include DRS, congenital fibrosis of EOMs, monocular elevation defect, Möbius syndrome, as well as several other non-ocular muscles supplied by cranial nerves such as facial muscles. Such loss of innervation to motor muscles can be unified as a defined clinical entity, which can be labelled as congenital innervation dysgenesis syndrome or CID for short. CID may also affect other muscles supplied by nerves other than the cranial nerves and may be sensory as well as motor.

Duane syndrome in association with 48,XXYY karyotype

Duane syndrome is an ocular motility disorder consisting of deficient horizontal eye movements, eyelid retraction, palpebral fissure narrowing, and abnormal vertical eye movements. It occurs in 1%-5% of patients with strabismus and has also been reported in several syndromes and chromosome abnormalities. Although most cases are sporadic, autosomal-dominant inheritance is seen in up to 10% of cases. Recently, Duane syndrome has been reported to occur in the setting of chromosomal duplication. The 48,XXYY syndrome is a rare syndrome involving duplication of the sex chromosomes. Ocular abnormalities are not typical of this condition. We report the first case of Duane syndrome presenting in an 8-month-old boy with XXYY syndrome. This case lends further support to the association of chromosomal duplication and Duane syndrome.

Potential linkage of different phenotypic forms of childhood strabismus to a recessive susceptibility locus (16p13.12-p12.3)

PURPOSE

To perform linkage analysis on an inbred family with members who exhibit different phenotypic forms of childhood strabismus.

METHODS

Prospective clinical examination and linkage analysis.

RESULTS

three of the ten siblings and their cousin each had a different phenotypic form of childhood strabismus: infantile esotropia with convergence excess, esotropia associated with anisometropic amblyopia, unilateral esotropic Duane syndrome, and monocular elevation deficiency. Linkage analysis for the four strabismic individuals, an unaffected sibling, and the unaffected parents identified a single disease locus on chromosome 16p13.12-p12.3 (Ensembl cytogenetic band) with a 2.5 maximum logarithm of odds score. The region is 6 MB in size and comprises 80 genes.

DISCUSSION

Linkage analysis in this unique family suggests that childhood strabismus can be recessive and that different phenotypic forms of childhood strabismus can share the same underlying genotype.

Duane syndrome in the setting of chromosomal duplications

PURPOSE

To describe the clinical findings in 3 patients with Duane syndrome and 3 different chromosomal duplications that may indicate the location of genes involved in the pathogenesis of this ocular motility disorder.

DESIGN

Observational case series.

METHODS

setting: Clinical practice. patient or study population: Three patients with Duane syndrome and chromosomal duplications from the clinical practice of 1 of the authors. observation procedures: Chart review and retrieval of clinical data and results of pertinent clinical tests, in this case chromosomal studies. main outcome measure: Reporting of details of clinical findings and duplicated chromosomal regions.

RESULTS

Two patients had unilateral type I Duane syndrome and 1 had bilateral type I Duane syndrome. Two had cognitive delay, and all 3 had other systemic abnormalities, including a variety of congenital malformations. The chromosomal abnormalities that were detected using microarray analysis were 2q13(RP11-20G1,RP11-461N11) × 3, 10q24.2q26.3(101,532,585-135,284, 169) × 3, 20q13.12(44,796,613-44,945, 818) × 3, and 22q11.1q11.22(RP11-701M12, RP11-71G19) × 3.

CONCLUSIONS

Patients with Duane syndrome and associated congenital malformations or developmental delay should be evaluated for the presence of underlying chromosomal duplications. The regions of chromosomes 2, 10, and 22 that we report may harbor genes involved in the pathogenesis of Duane syndrome.

Review of the major findings about Duane retraction syndrome (DRS) leading to an updated form of classification

In view of all the reported evidence by electromyography in the 1970s, by histology in the 1980s, and by cerebral imagery since the 2000s, Duane retraction syndrome (DRS) has been described as the consequence of a congenital anomaly of the 6th cranial nerve nuclei with aberrant innervations by supply from the 3rd cranial nerve. Both genetic and environmental factors are likely to play a role when the cranial nerves and ocular muscles are developing between the 4th and the 8th week of gestation. New data from eye movement recordings contributed to better understanding the binocular control of saccades. Modeling of saccades in DRS seems promising for the quantification of the innervational deficit and the mechanical properties of the eye plant. The usual clinical classification of DRS needs to be updated in order to match more accurately the underlying dysinnervation of the extra ocular muscles and to illustrate the continuum that exists between the various forms. This review aims to summarize the major findings about DRS and to guide the clinician in the surgical management of this particular form of strabismus.

Distinctive clinical features of bilateral Duane retraction syndrome

PURPOSE

To compare the clinical characteristics of unilateral and bilateral forms of Duane retraction syndrome.

METHODS

A retrospective chart review of patients with Duane syndrome over a 10-year span was performed. All participants underwent a complete medical and ophthalmologic examination at the time of diagnosis. Data collected included the following: sex, age at first visit, form (unilateral/bilateral), side, type, ocular duction and version, abnormal head position, best-corrected visual acuity, refractive errors, presence of strabismus, binocular function, and associated congenital anomalies.

RESULTS

Of 94 patients identified, 17% were bilaterally affected. Of the bilateral patients, 12% had familial antecedents; 87.5% had the same type in both eyes with 75% bilateral type 1. Patients with bilateral Duane syndrome had significantly different visual acuity (mean, 0.1214 logMar vs 0.0035; p = 0.045), abnormal head position (56.25% vs 89%; p = 0.04), A or V patterns (69% vs 27.6%; p = 0.003), and associated congenital anomalies (50% vs 14%; p = 0.003) than patients with unilateral disease. There was also a suggestion of higher rates of ametropia, global vertical dysfunction, and abnormal stereoacuity in bilateral Duane syndrome that were not statistically significant.

CONCLUSIONS

Patients with bilateral Duane syndrome had lower visual acuity, a lower incidence of abnormal head posture, and a higher incidence of A or V patterns and associated congenital anomalies. Bilateral Duane retraction syndrome seems to involve multiple instances of deinnervation and fibrosis, resulting in horizontal and vertical oculomotor deficits and functional impairments.

Bilateral Duane retraction syndrome associated with an extraordinary hand anomaly

Duane retraction syndrome is an ocular motility disorder with which an increasing number of congenital abnormalities appear to be associated. In the present paper the authors report a case of bilateral Duane retraction syndrome with an extraordinary hand abnormality. Numerous theories concerning the etiology and pathogenesis of Duane retraction syndrome and its relationship to the associated findings have been proposed, but the exact mechanism is still under investigation. Further multi-centered studies and the classification of the associated clinical findings in an organized manner may help to explain this mechanism.

Left-sided Duane's Syndrome and Retinal Coloboma associated with Contralateral Microphthalmia

Case report of a 15-year-old girl presenting with a left-sided Duane's retraction syndrome (DURS) in combination with ipsilateral retinal coloboma and contralateral microphthalmia. Abduction limitation as well as narrowing of the palpebral fissure and globe retraction during attempted adduction (type I DURS) was demonstrated in the left eye. Additionally, a retinal coloboma was observed in the nasal inferior quadrant of the left eye. No other somatic or developmental abnormalities were observed and karyotypic analysis was normal. This is the first case of non-syndromic unilateral DURS associated with a contralateral major ocular malformation. This unusual clinical combination probably arose from the embryonic action of an eye-specific disruptor.

Clinical features associated with an I126M alpha2-chimaerin mutation in a family with autosomal-dominant Duane retraction syndrome

PURPOSE

We describe the clinical phenotype of a Mexican family segregating Duane syndrome as an autosomal-dominant trait linked to chromosome 2q31 (DURS2) and previously reported to harbor a heterozygous alpha2-chimaerin missense mutation.

METHODS

A 5-generation Mexican family was analyzed. Ten affected subjects were available for clinical examination. Participating subjects were tested for visual acuity, ocular alignment by prism cover testing, ocular ductions and versions, and globe retraction. In children, alignment was measured with the Krimsky test in cardinal positions of gaze.

RESULTS

Ten cases were included, 6 female and 4 male subjects. Five cases presented with bilateral and 5 with unilateral Duane syndrome. The right side was the most commonly affected side on unilateral cases. Five cases exhibited exotropia, 4 esotropia, and 1 hypotropia. Seven patients had severe limitation of abduction and two had moderate limitation. Four patients had mild adduction limitation and 4 had moderate limitation. No additional anomalies such as fourth (trochlear) nerve palsy, blepharoptosis, or dense amblyopia, which have been reported in previous families with Duane syndrome, were observed. All 3 cases that exhibited vertical dysfunction had upgaze limitation. One instance of nonpenetrance was recorded.

CONCLUSIONS

Considerable intrafamilial clinical variability was observed in this Duane syndrome pedigree that carried a alpha2-chimaerin mutation. The presence of bilateral involvement and associated vertical movements, which commonly are observed in this and other DURS2 families, could suggest the occurrence of CHN1 mutations as the source of the disease in isolated or familial DURS cases.

Duane retraction syndrome, nystagmus, retinal pigment epitheliopathy and epiretinal membrane with micro- and pachygyria, developmental delay, hearing loss and craniopharyngioma

PURPOSE

To report the association of Duane syndrome with nystagmus and a patterned hyperpigmentation of the retinal pigment epithelium, developmental delay, micro- and pachygyria and craniopharyngioma.

CASE REPORT

We describe a 12-year old girl with developmental delay, hearing loss, cortical micro- and pachygyria, and a cystic craniopharyngioma; her ocular features include unilateral Duane syndrome, monocular nystagmus under binocular conditions, and a patterned hyperpigmentation of the retinal pigment epithelium. Her mother had similar retinal pigment epithelial abnormalities.

CONCLUSIONS

The combination of two neuronal migrational disorders, the unusual retinal pigment epithelial abnormalities in the proband and her mother, and evidence that each feature may be genetic and are suggestive of a genetic basis for this constellation of features.

Genes on bovine chromosome 18 associated with bilateral convergent strabismus with exophthalmos in German Brown cattle

PURPOSE

Bilateral convergent strabismus with exophthalmos (BCSE) is a widespread inherited eye defect in several cattle populations. Its progressive condition often leads to blindness in affected cattle and shortens their length of productive life. Furthermore, breeding with BCSE-affected animals is forbidden by the German animal welfare laws. We performed a mutation and association analysis for three candidate genes (troponin T type 1 [TNNT1], retinol dehydrogenase 13 [RDH13], and TCF3 fusion partner [TFPT]), which are located within the previously identified BCSE-linked region on the telomeric end of bovine chromosome 18 (BTA18). In addition, we developed single nucleotide polymorphisms (SNPs) within these three candidate genes and nine other genes that are contained in this genomic BCSE-region to perform association analyses with BCSE in German Brown cattle.

METHODS

We performed cDNA analyses of all three candidate genes using eye tissues of three affected German Brown cows and three unaffected controls. Furthermore, we screened the exonic and the adjacent genomic sequences of RDH13, TNNT1, and TFPT using four BCSE-affected and four controls of German Brown cattle. Here, we included all exons of RDH13 and those exons of TNNT1 and TFPT for which SNPs were detected by cDNA analyses. In addition, we developed 21 polymerase chain reaction (PCR) products for 17 more genes in the BCSE region and searched them for polymorphisms. All markers detected were genotyped in 48 BCSE-affected German Brown cows and 48 breed and sex matched controls and tested for association with BCSE.

RESULTS

In total, we detected 29 SNPs in 12 genes. In the coding sequence of the three candidate genes, we identified 10 exonic SNPs and a new splice variant of TNNT1. Four SNPs were associated with the BCSE phenotype in single marker-trait analyses. These SNPs were located within DHDH (dihydrodiol dehydrogenase dimeric), CPT1C (carnitine palmitoyltransferase 1C), TNNT1, and NALP7. The marker-trait association for haplotypes including five SNPs of CPT1C, SYT5 (synaptotagmin V), RDH13, and NALP7 (NLR family, pyrin domain containing 7) revealed a significant association with BCSE. We identified three individual haplotypes that were significantly associated with BCSE. These haplotypes spanned the region from 56.05 Mb to 62.87 Mb on BTA18.

CONCLUSIONS

The haplotype association analysis corroborated the results of the linkage study that the telomeric end of BTA18 harbors a gene responsible for BCSE and further refines the BCSE region to a 6.82 Mb interval ranging from 56.05 Mb to 62.87 Mb on BTA18.

Midline orofacial cleft defects in association with type 1 Duane's retraction syndrome

Anomalies of ocular motility associated with Duane's retraction syndrome (DRS) have often been perceived as isolated phenomena arising as a result of congenital ocular miswiring between the lateral and medial recti muscles. Interestingly, the reporting of concomitant ocular and systemic anomalies arising in the setting of DRS discounts this narrow perception and highlights the importance of a thorough investigation for non-ocular comorbidities. A 37-year-old Caucasian male presented for a routine ocular examination with complaints of gradual reduction in uncorrected near vision. Our testing confirmed the characteristic deficit of abduction, palpebral fissure narrowing and globe retraction consistent with a type 1 Duane's defect of the right eye. A midline cleft lip and palate were also noted in the absence of signs of nuchal rigidity/reduced range of motion in the cervical spine, spinal misalignment, deafness, optic nerve anomalies, hypertelorism or altered mental state. Awareness of key comorbidities and the importance of thorough clinical evaluation with appropriate supplemental testing and consultation with a paediatric ophthalmologist are warranted in non-isolated presentations of DRS.

Human CHN1 mutations hyperactivate alpha2-chimaerin and cause Duane's retraction syndrome

Duane's retraction syndrome (DRS) is a complex congenital eye movement disorder caused by aberrant innervation of the extraocular muscles by axons of brainstem motor neurons. Studying families with a variant form of the disorder (DURS2-DRS), we have identified causative heterozygous missense mutations in CHN1, a gene on chromosome 2q31 that encodes alpha2-chimaerin, a Rac guanosine triphosphatase-activating protein (RacGAP) signaling protein previously implicated in the pathfinding of corticospinal axons in mice. We found that these are gain-of-function mutations that increase alpha2-chimaerin RacGAP activity in vitro. Several of the mutations appeared to enhance alpha2-chimaerin translocation to the cell membrane or enhance its ability to self-associate. Expression of mutant alpha2-chimaerin constructs in chick embryos resulted in failure of oculomotor axons to innervate their target extraocular muscles. We conclude that alpha2-chimaerin has a critical developmental function in ocular motor axon pathfinding.

Magnetic resonance imaging of innervational and extraocular muscle abnormalities in Duane-radial ray syndrome

PURPOSE

The authors used magnetic resonance imaging (MRI) to study extraocular muscles (EOMs) and nerves in Duane-radial ray (Okihiro) syndrome (DRRS) caused by mutations in the transcription factor SALL4.

METHODS

The authors examined four male and two female affected members of a pedigree previously reported to cosegregate DRRS and a heterozygous SALL4 mutation. Coronal T1-weighted magnetic resonance images of the orbits and heavily T2-weighted images in the plane of the cranial nerves were obtained in four subjects. MRI findings were correlated with motility examinations and published norms obtained using identical technique.

RESULTS

Five of the six subjects with DRRS had radial ray abnormalities including thumb, radial artery, radial bone, and pectoral muscle hypoplasia. Three had bilateral and three had unilateral ocular involvement. Seven eyes had limitation of both abduction and adduction, whereas two had limitations only of abduction. Most affected eyes had lid fissure narrowing and retraction in adduction. Intraorbital and intracranial abducens nerves (CN6) were small to absent, particularly ipsilateral to abduction deficiency. All subjects undergoing MRI had normal intracranial oculomotor nerves (CN3). Optic nerve (ON) cross-section findings were similar to normal. EOMs and pulleys were structurally normal in most subjects. In some affected orbits, a branch of CN3 closely approximated and presumably innervated the LR.

CONCLUSIONS

DRRS encompasses a Duane syndrome phenotype, with a variable and asymmetric endophenotype including marked CN6 hypoplasia and probable innervation or coinnervation of the LR by CN3. This endophenotype is more limited than reported in DURS2-linked Duane syndrome (On-line Mendelian Inheritance in Man, OMIM 604356) and CFEOM1 (OMIM 135700), which are clinically similar congenital cranial dysinnervation disorders that also feature CN3 hypoplasia and more widespread EOM abnormalities.

Bilateral familial Duane's retraction syndrome

BACKGROUND

Duane's retraction syndrome (DRS) is a congenital oculomotor anomaly that is accompany by globe retraction with simultaneous narrowing of the palpebral fissure on attempted adduction. Hereditary factors have been postulated to be associated with the development of DRS since 1879. However, the modern literature fails to provide substantial scientific evidence to support this premise.

CASE REPORT

A 7-year-old patient presented with bilateral abduction deficit and retraction of the globe with narrowing of the palpebral fissure on attempted adduction.

CONCLUSION

We present a case of Duane's retraction syndrome in which an investigation of the family history uncovered 4 generations of affected family members, lending support to the theory that some cases of DRS are inherited.

Interstitial del(20)(q11.2q12) - clinical and molecular cytogenetic characterization

A 2-year-old male patient with dysmorphic facial features and multiple congenital anomalies suggestive of a chromosome syndrome is presented. The facial features consisted of a large and high forehead, mild metopic ridging, a small triangular face, depressed nasal bridge, microphthalmia (right more than the left), protruding ears, and mildly prominent anteverted nose with long and smooth philtrum. Cytogenetic analysis showed 46,XY,del(20)(q11.2q12). Parental karyotypes were normal. Molecular characterization of del(20)(q11.2q12) by high-resolution microarray comparative genomic hybridization (arrayCGH) showed an approximately 6.8 Mb deletion. To our knowledge this is the first report of a de novo interstitial del(20)(q11.2q12) characterized by arrayCGH.

Clinical characterization of the HOXA1 syndrome BSAS variant

BACKGROUND

The Bosley-Salih-Alorainy syndrome (BSAS) variant of the congenital human HOXA1 syndrome results from autosomal recessive truncating HOXA1 mutations. We describe the currently recognized spectrum of ocular motility, inner ear malformations, cerebrovascular anomalies, and cognitive function.

METHODS

We examined nine affected individuals from five consanguineous Saudi Arabian families, all of whom harbored the same I75-I76insG homozygous mutation in the HOXA1 gene. Patients underwent complete neurologic, neuro-ophthalmologic, orthoptic, and neuropsychological examinations. Six individuals had CT, and six had MRI of the head.

RESULTS

All nine individuals had bilateral Duane retraction syndrome (DRS) type 3, but extent of abduction and adduction varied between eyes and individuals. Eight patients were deaf with the common cavity deformity of the inner ear, while one patient had normal hearing and skull base development. Six had delayed motor milestones, and two had cognitive and behavioral abnormalities meeting Diagnostic and Statistical Manual of Mental Disorders-IV criteria for autism spectrum disorder. MRI of the orbits, extraocular muscles, brainstem, and supratentorial brain appeared normal. All six appropriately studied patients had cerebrovascular malformations ranging from unilateral internal carotid artery hypoplasia to bilateral agenesis.

CONCLUSIONS

This report extends the Bosley-Salih-Alorainy syndrome phenotype and documents the clinical variability resulting from identical HOXA1 mutations within an isolated ethnic population. Similarities between this syndrome and thalidomide embryopathy suggest that the teratogenic effects of early thalidomide exposure in humans may be due to interaction with the HOX cascade.

Two pedigrees segregating Duane's retraction syndrome as a dominant trait map to the DURS2 genetic locus

PURPOSE

The genetic bases of Duane's retraction syndrome (DRS) were investigated to determine its molecular etiologies. In prior studies, the transcription factors SALL4 and HOXA1 were identified as the genes mutated in DRS with radial anomalies, and in DRS with deafness, vascular anomalies, and cognitive deficits, respectively. Less is known, however, about the genetic etiology of DRS when it occurs in isolation, and only one genetic locus for isolated DRS, the DURS2 locus on chromosome 2, has been mapped to date. Toward the goal of identifying the DURS2 gene, two pedigrees have been ascertained that segregate DRS as a dominant trait.

METHODS

Members of two large dominant DRS pedigrees were enrolled in an ongoing study of the genetic basis of the congenital cranial dysinnervation disorders, and linkage analysis was conducted to determine whether their DRS phenotype maps to the DURS2 locus.

RESULTS

By haplotype analysis, the DRS phenotype in each family cosegregates with markers spanning the DURS2 region. Linkage analysis reveals maximum lod scores >2, establishing that the DRS phenotype in these two pedigrees maps to the DURS2 locus.

CONCLUSIONS

These two pedigrees double the published pedigrees known to map to the DURS2 locus and can thus contribute toward the search for the DURS2 gene. The affected members represent a genetically defined population of DURS2-linked DRS individuals, and hence studies of their clinical and structural features can enhance understanding of the DURS2 phenotype, as described in the companion paper.

Magnetic resonance imaging evidence for widespread orbital dysinnervation in dominant Duane's retraction syndrome linked to the DURS2 locus

PURPOSE

High-resolution, multipositional magnetic resonance imaging (MRI) was used to demonstrate extraocular muscles (EOMs) and associated motor nerves in Duane retraction syndrome (DRS) linked to the DURS2 locus on chromosome 2.

METHODS

Five male and three female affected members of two autosomal dominant DURS2 pedigrees were enrolled in the study. Coronal T(1)-weighted MRI of the orbits was obtained in multiple gaze positions, as well as with heavy T(2) weighting in the plane of the cranial nerves. MRI findings were correlated with motility.

RESULTS

All subjects had unilateral or bilateral limitation of abduction, or of both abduction and adduction, with palpebral fissure narrowing and globe retraction in adduction. Orbital motor nerves were typically small, with the abducens nerve (cranial nerve [CN]6) often nondetectable. Lateral rectus (LR) muscles were structurally abnormal in seven subjects, with structural and motility evidence of oculomotor nerve (CN3) innervation from vertical rectus EOMs leading to A or V patterns of strabismus in three cases. Four cases had superior oblique, two cases superior rectus, and one case levator EOM hypoplasia. Only the medial and inferior rectus and inferior oblique EOMs were spared. Two cases had small CN3s.

CONCLUSIONS

DRS linked to the DURS2 locus is associated with bilateral abnormalities of many orbital motor nerves, and structural abnormalities of all EOMs except those innervated by the inferior division of CN3. The LR may be coinnervated by CN3 branches normally destined for any other rectus EOMs. Therefore, DURS2-linked DRS is a diffuse congenital cranial dysinnervation disorder involving but not limited to CN6.

Interstitial deletion of 1q42.13-q43 with Duane retraction syndrome

Duane retraction syndrome is a congenital eye movement disorder characterized by failure of the sixth cranial nerve or nucleus to develop properly, resulting in restriction of abduction, narrowing of the palpebral fissure, and retraction of the globe on attempted adduction and/or restricted adduction. The gene loci of Duane syndrome have been mapped on 8q and 2q, indicating a heterogeneity. We report here a patient with interstitial deletion of 1q with Duane syndrome. The karyotype of our patient suggests another possible locus of the Duane syndrome, and the mapped genes around the deleted region, 1q42.13-43, contain possible candidate genes such as a homeobox gene. However, further clinical descriptions of patients with Duane syndrome and genetic investigations of the deleted regions are needed for a more accurate delineation.

The genetics of strabismus

Strabismus (misalignment of the eyes; also known as "squint") comprises a common heterogeneous group of disorders characterised by a constant or intermittent ocular deviation often associated with amblyopia (uniocular failure of normal visual development) and reduced or absent binocular vision. The associated poor cosmetic appearance may also interfere with social and psychological development. Extensive twin and family studies suggest a significant genetic component to the aetiology of strabismus. The complexity of the molecular basis of strabismus is now beginning to be elucidated with the identification of genetic loci and disease causing genes. Currently greater insights have been gained into the incomitant subtype (differing magnitude of ocular misalignment according to direction of gaze), whereas less is known about the pathogenesis of the more common childhood concomitant strabismus. It is hoped that a greater understanding of the molecular genetics of these disorders will lead to improved knowledge of disease mechanisms and ultimately to more effective treatment. The aim of this paper is to review current knowledge of the molecular genetics of both incomitant and concomitant strabismus.

Are Duane syndrome and infantile esotropia allelic?

PURPOSE

To evaluate the clinical overlap of families with Duane syndrome and infantile esotropia to determine whether the identification of genes for Duane syndrome may explain some cases of infantile esotropia.

METHODS

Three separate groups of patients were evaluated. 1) Families with features of infantile esotropia were identified through the Strabismus Inheritance Study Tasmania (SIST). Clinical details of participants and their families were reviewed for any cases of Duane syndrome. 2) Cases of Duane syndrome were identified through the clinical diagnostic database at the Royal Children's Hospital, Melbourne, and private ophthalmology clinics in Melbourne and Tasmania. Previous medical notes were reviewed and family history of strabismus noted. All affected individuals were invited for re-examination in cases where a positive family history of strabismus was reported; siblings, parents, and other family members, where appropriate, were invited to be examined for signs of Duane syndrome or infantile esotropia. 3) Cases of mosaic trisomy 8, which has been associated with Duane syndrome and infantile esotropia, were reviewed for signs of strabismus.

RESULTS

A total of 133 families from the SIST were reviewed, but no 'pure' families of Duane syndrome were identified. Two families with infantile esotropia had several members affected with Duane syndrome. Of the 40 index cases with Duane syndrome whose families agreed to be involved in the study, 21 had a family history of ocular motility disorders, but only two of these families had multiple cases of Duane syndrome. From 24 cases with mosaic trisomy 8, one individual case had Duane syndrome and another had mild congenital cataracts and infantile esotropia.

CONCLUSIONS

There is clinical overlap in families with Duane syndrome and infantile esotropia. We confirmed the previous association of mosaic trisomy 8 with both Duane syndrome and infantile esotropia. These data suggest that the two conditions may be allelic and may be due to a gene on chromosome 8.