Association of familial Duane anomaly and urogenital abnormalities with a bisatellited marker derived from chromosome 22

The genetic etiologies of bilateral renal agenesis

OBJECTIVE

The goal of this study was to review and analyze the medical literature for cases of prenatal and/or postnatally diagnosed bilateral renal agenesis (BRA) and create a comprehensive summary of the genetic etiologies known to be associated with this condition.

METHODS

A literature search was conducted as a scoping review employing Online Mendeliain Inheritance in Man, PubMed, and Cochrane to identify cases of BRA with known underlying genetic (chromosomal vs. single gene) etiologies and those described in syndromes without any known genetic etiology. The cases were further categorized as isolated versus non-isolated, describing additional findings reported prenatally, postnatally, and postmortem. Inheritance pattern was also documented when appropriate in addition to the reported timing of diagnosis and sex.

RESULTS

We identified six cytogenetic abnormalities and 21 genes responsible for 20 single gene disorders associated with BRA. Five genes have been reported to associate with BRA without other renal anomalies; sixteen others associate with both BRA as well as unilateral renal agenesis. Six clinically recognized syndromes/associations were identified with an unknown underlying genetic etiology. Genetic etiologies of BRA are often phenotypically expressed as other urogenital anomalies as well as complex multi-system syndromes.

CONCLUSION

Multiple genetic etiologies of BRA have been described, including cytogenetic abnormalities and monogenic syndromes. The current era of the utilization of exome and genome-wide sequencing is likely to significantly expand our understanding of the underlying genetic architecture of BRA.

Rare otologic presentation of cat eye syndrome

We encountered an extremely rare case where a patient with cat eye syndrome (CES) who presented with symptoms of posterior semicircular canal dehiscence (PSCD). CES is a rare genetic disorder, resulting from duplication of chromosome 22. Patients may present with variable phenotypes, including characteristic of coloboma, heart defect, periauricular skin pit/tag, microtia, anal atresia and mildly retarded mental development in some cases. PSCD is also a disease of the inner ear, where patients present with third window signs and symptoms due to lack of bony coverage. PSCD is usually associated with a high riding jugular bulb and fibrous dysplasia. In this study, we report a new otologic finding in CES patient as an association of PSCD and high jugular pulp. We describe the work up and its findings and the management of this patient. SIMILAR CASES PUBLISHED:: None.

A Case of Duane's Retraction Syndrome with Multiple Congenital Malformations

Duane's retraction syndrome is associated with various ocular and systemic abnormalities. We report a case with bilateral Duane's retraction syndrome type I accompanied by renal agenesis, vesico-ureteral reflux, patent ductus arteriosus, and external ear malpositioning. Because of disabling consequences, we recommend a thorough physical examination and screening for renal and cardiac abnormalities in all patients presenting with Duane's reaction syndrome.

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.

A microdeletion in the GRHL2 Gene in two unrelated patients with congenital fibrosis of the extra ocular muscles

Objective

Congenital fibrosis of the extraocular muscles type 1 (CFEOM1) is known to be caused by mutations in KIF21A or TUBB3 or other known genes (SALL4, CHN1, HOXA1). However, affected children may harbor other genetic defects. Therefore, a candidate gene analysis (KIF21A, TUBB3 SALL4, CHN1, HOXA1) and a high-resolution array comparative genomic hybridization (arrayCGH) was performed in two unrelated children with sporadic CFEOM1.

Results

Two unrelated Saudi patients did not have any mutation(s) after sequencing the full coding regions of SALL4, CHN1, HOXA1, and TUBB3 genes; and exons 8, 20, and 21 of the KIF21A gene. However, arrayCGH revealed a 3.17 Kb deletion at chromosome 8p22 with copy number state equal to 1, indicating a heterozygous deletion. This deletion was absent in proband’s mother or father or 220 unrelated healthy individuals of similar ethnicity. The deletion encompassed only one functional gene, GRHL2, which encodes a transcription factor. In humans, defects in this gene are a cause of non-syndromic sensorineural deafness, autosomal dominant type 28 (DFNA28). We speculate that GRHL2 gene may have a role in orbital innervations and the defect in this gene (deletion) may be related to the CFEOM1 phenotype in these two children.

The genetics of nonsyndromic bilateral Duane retraction syndrome

PURPOSE

To assess the importance of monogenic mutations and chromosomal copy number variants (CNVs) in the occurrence of nonsyndromic bilateral Duane retraction syndrome (bilateral nsDRS).

METHODS

The medical records of 12 patients with bilateral nsDRS were reviewed. Genes associated with DRS and associated congenital cranial dysinnervation disorders (SALL4, CHN1, HOXA1, TUBB3, and KIF21A) were sequenced in the standard fashion in each patient. Array comparative genomic hybridization (array CGH) was performed using Affymetrix Cytogenetics Whole-Genome 2.7M array, and the results were analyzed using Affymetrix Chromosome Analysis Suite v1.2. CNVs were assessed as unlikely to be pathologic if they were also present in the Database of Genomic Variants (DGV) or our local database of array CGH results in 150 normal individuals of Middle Eastern ethnicity.

RESULTS

No patient had a sequence mutation in SALL4, CHN1, HOXA1, TUBB3, or KIF21A. These 12 patients each had 36-42 chromosomal deletions and/or duplications (mean with standard deviation, 26.25 ± 6.77), but all of these CNVs were present either in the DGV or in our local database of normal individuals of similar ethnicity and, therefore, are considered nonpathogenic.

CONCLUSIONS

The results reported here suggest that bilateral nsDRS is not usually associated with mutations in these genes or with chromosomal CNVs. Current evidence suggests other factors such as epigenetic and/or teratogenic abnormalities may be a potential cause of bilateral nsDRS.

Etiologies of uterine malformations

Ranging from aplastic uterus (including Mayer-Rokitansky-Kuster-Hauser syndrome) to incomplete septate uterus, uterine malformations as a group are relatively frequent in the general population. Specific causes remain largely unknown. Although most occurrences ostensibly seem sporadic, familial recurrences have been observed, which strongly implicate genetic factors. Through the study of animal models, human syndromes, and structural chromosomal variation, several candidate genes have been proposed and subsequently tested with targeted methods in series of individuals with isolated, non-isolated, or syndromic uterine malformations. To date, a few genes have garnered strong evidence of causality, mainly in syndromic presentations (HNF1B, WNT4, WNT7A, HOXA13). Sequencing of candidate genes in series of individuals with isolated uterine abnormalities has been able to suggest an association for several genes, but confirmation of a strong causative effect is still lacking for the majority of them. We review the current state of knowledge about the developmental origins of uterine malformations, with a focus on the genetic variants that have been implicated or associated with these conditions in humans, and we discuss potential reasons for the high rate of negative results. The evidence for various environmental and epigenetic factors is also reviewed. © 2016 Wiley Periodicals, Inc.

CCDD Phenotype Associated with a Small Chromosome 2 Deletion

PURPOSE

Some individuals are born with congenital limitation of ocular motility, often associated with ptosis and retraction of the globe. Many of these disorders are now known as the congenital cranial dysinnervation disorders (CCDDs). While several genes have been associated with CCDD phenotypes, there are still patients for whom the genetic basis has not been identified.

METHODS

Clinical evaluation and neuroimaging, sequencing of candidate genes, and array comparative genomic hybridization (array CGH).

RESULTS

The patient was a four-year-old girl with mild dysmorphism; bilateral mild ptosis; substantial limitation of abduction OS with milder limitations of abduction OD, adduction OS, and vertical gaze OS; and retraction OS > OD on attempted adduction. No mutations were detected in the HOXA1, KIF21A, SALL4, TUBB3, and CHN1 genes. Array CGH revealed a 8 Kb de novo deletion on chromosome 2 (2q24.3) that encompassed a portion of only one gene, the Xin Actin-binding Repeat containing 2 (Gene Symbol XIRP2; NM_001079810). This gene encodes a protein that is involved in muscle development and protecting actin filaments from depolymerization. It interacts functionally with 10 other proteins playing a similar role in muscle development.

CONCLUSIONS

This patient's chromosomal abnormality affected only one gene that currently seems involved only in muscle development. All other genes currently associated with the CCDDs affect neurologic development. Genetic information from this patient implies that genes involved in development and maintenance of extraocular muscles can cause congenital ocular motility disorders as well.

Partial duplication of chromosome 19 associated with syndromic duane retraction syndrome

BACKGROUND

To evaluate possible monogenic and chromosomal anomalies in a patient with unilateral Duane retraction syndrome, modest dysmorphism, cerebral white matter abnormalities, and normal cognitive function.

MATERIALS AND METHODS

Performing high-resolution array comparative genomic hybridization (array CGH) and sequencing of HOXA1, KIF21A, SALL4, and CHN1 genes.

RESULTS

The proband had unilateral Duane retraction syndrome (DRS) type III on the right with low-set ears, prominent forehead, clinodactyly, and a history of frequent infections during early childhood. Motor development and cognitive function were normal. Parents were not related, and no other family member was similarly affected. MRI revealed multiple small areas of high signal on T2 weighted images in cerebral white matter oriented along white matter tracts. Sequencing of HOXA1, KIF21A, SALL4, and CHN1 did not reveal any mutation(s). Array CGH showed a 95 Kb de novo duplication on chromosome 19q13.4 encompassing four killer cell immunoglobulin-like receptor (KIR) genes. Conclusions. KIR genes have not previously been linked to a developmental syndrome, although they are known to be expressed in the human brain and brainstem and to be associated with certain infections and autoimmune diseases, including some affecting the nervous system. DRS and brain neuroimaging abnormalities may imply a central and peripheral oligodendrocyte abnormality related in some fashion to an immunomodulatory disturbance.

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.

Partial tetrasomy of chromosome 22q11.1 resulting from a supernumerary isodicentric marker chromosome in a boy with cat-eye syndrome

The 22q11 region has been implicated in chromosomal rearrangements that result in altered gene dosage, leading to three different congenital malformation syndromes: DiGeorge syndrome, cat-eye syndrome (CES), and der(22) syndrome. Although DiGeorge syndrome is a common genomic disorder on 22q11, CES is quite rare, and there has been no report of Korean CES cases with molecular cytogenetic confirmation. In this study, we present the phenotypic and genetic characteristics of a 3-month-old boy with CES. Clinical findings included micropthalmia, multiple colobomata, and renal and genital anomalies. Cytogenetic analyses showed the presence of a supernumerary marker chromosome, which was identified as a bisatellited and isodicentric chromosome derived from an acrocentric chromosome. The results of array comparative genomic hybridization and fluorescence in situ hybridization studies confirmed the karyotype as 47,XY,+mar.ish idic(22)(q11.1) (D22S43+).arr 22q11.1(15,500,000-15,900,000)x4, resulting in a partial tetrasomy of 22q11.1. To the best of our knowledge, this is the first report in Korea of CES confirmed by cytogenetic and molecular cytogenetic analyses.

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.

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.

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.

FISH approach to determine cat eye syndrome chromosome breakpoints of a patient with cat eye syndrome type II

We report a 19-year-old man with craniofacial dysmorphic features, anorectal malformations, eye colobomas, orthopaedic anomalies, and mild neurodevelopmental delay. Cat eye syndrome (CES) was suspected, and confirmed by cytogenetic analysis which showed the presence of a supernumerary bisatellited chromosome, identified by fluorescence in situ hybridization (FISH) as invdup(22). The marker was further analyzed with six BAC clones located at the 22q11.1 and 22q11.2 regions; this analysis allowed correct assignment at low copy repeat 4 on chromosome 22 (LCR22-4) of the two breakpoints, confirming the presence of a CES chromosome type II. The patient's phenotype is considered in the light of the cytogenetic, and FISH investigations results and other patients reported in literature. Molecular definition of the breakpoints at the LCR22-4 copy confirms the role of different chromosome 22-specific LCRs in CES chromosomes generation, as well as in other chromosome 22 germ line rearrangements. Our report confirms that, unlike other conditions, i.e. the invdup(15) bisatellited dicentric marker, the CES phenotype does not appear to correlate with the size of the marker chromosome. Additional cases are necessary to be able to draw more specific genotype-phenotype correlations and to determine the outcome of patients with CES, especially when this rare condition is diagnosed in prenatal age.

A family with Duane anomaly and distal limb abnormalities: A further family with the arthrogryposis-ophthalmoplegia syndrome

A two-generation family is reported in which three members have Duane anomaly and distal limb abnormalities. All three affected have photopic electroretinogram responses that are abnormal or at the lower limit of the normal range with normal scotopic responses. Two affected family members also have hearing loss. The likeliest diagnosis is the syndrome listed as "arthrogryposis-ophthalmoplegia syndrome" on the London Dysmorphology Database or as "arthrogryposis with oculomotor limitation and electroretinal abnormalities" or "oculomelic aplasia" in OMIM [MIM 108145]. In view of the similarities with Okihiro syndrome, a search for mutations within the SALL4 gene was undertaken, but none were identified.

Paradoxical eyelid movement in trisomy 2p

Paradoxical eyelid movement was reported in a 12-year-old female with 46,XX,dup(2)(p25.3p22.2). Alternating seesaw-like movement of the eyelids during lateral gazing had been observed at 5 months of age when she was first referred to our neuropediatric outpatient department, and the abnormal lid movement persisted without any change for 11 years. The differentiation of the features of the paradoxical lid movements in our patient from those of Duane syndrome were discussed, and a possible pathogenesis is discussed as well. Besides ophthalmologic abnormalities, the patient demonstrated severe psychomotor retardation, marked growth failure, symptomatic generalized epilepsy, and multiple anomalies. The dysmorphism consisted of a cleft lip, a narrow high-arched palate, malalignment, lowset ears, and kyphoscoliosis caused by fused thoracic vertebrae.

Congenital anomalies in patients with Duane retraction syndrome and their relatives

PURPOSE

Although the high incidence of skeletal, neural, and other ocular problems has been identified in previous reports of large cohorts of patients with Duane syndrome, there has not been any documentation of anomalies in close relatives. Patients with Duane syndrome have a greater than 50% incidence of associated abnormalities that include deafness, other ocular anomalies, cranial nerve palsies, and skeletal abnormalities. This study was undertaken to review the experience of our strabismus service with patients who have Duane retraction syndrome (DRS) and to delineate the associated anomalies in them and their first-degree relatives.

METHODS

A prospective study of all patients with Duane syndrome who were seen at the strabismus service at Moorfields Eye Hospital has been ongoing for the last 4 years. All patients were assessed for the presence of ophthalmologic features of DRS and then referred to the pediatric service for a physical and neurologic examination. First-degree relatives were also examined, and a family pedigree was generated.

RESULTS

We have evaluated 68 patients with DRS, of which 60.2% were female patients. The left eye was involved at a ratio of 4:1 in unilateral cases. The number of bilateral cases was 57.3%. Among the patients with DRS, 46% had first-degree relatives with associated abnormalities.

CONCLUSIONS

The high incidence of associated anomalies in patients and first-degree relatives may suggest that a common genetic defect is responsible. This has to be confirmed with molecular genetic studies, which were not performed on these families because of a lack of available resources. However, our findings may indicate that the inheritance of Duane syndrome is much higher than the 10% previously reported, if any congenital abnormality is accepted as DRS associated. Children with Duane syndrome may benefit from a full medical assessment, in view of the frequency of other abnormalities, and so may their siblings.

Duane's syndrome

Duane's syndrome is an unusual congenital form of strabismus where there is paradoxical anomalous lateral rectus innervation of the affected eye due to misdirection of axons destined for the medial rectus. Three types of Duane's syndrome are recognized. Most cases of Duane's syndrome are sporadic but up to 10% are familial, usually with autosomal dominant inheritance. Several autosomal dominant syndromes with dysmorphic features are associated with Duane's syndrome. Chromosomal loci for genes contributing to Duane's syndrome have been suggested at 4q, 8q and 22q. Duane's syndrome is heterogeneous at multiple levels with variations in its ocular manifestations, accompanying systemic manifestations and in the chromosomal loci with which it may be associated. The definition clinically and genetically of the various subgroups of Duane's syndrome will provide a valuable insight into brainstem axonal guidance to the extraocular muscles during human development.

Clinical diversity of hereditary Duane's retraction syndrome

OBJECTIVE

To define the spectrum of ophthalmic manifestations of Duane's retraction syndrome (DRS) in a large family.

DESIGN

Cross-sectional study of 110 among 114 living relatives in an extended family.

METHODS

History and ophthalmic examination obtained on all participants.

MAIN OUTCOME MEASURES

Ocular motility, strabismus, visual acuity, binocularity, associated neurologic problems.

RESULTS

Twenty-five individuals were affected with DRS. Twenty-four subjects (96%) had bilateral DRS, but there was a broad spectrum of severity. Strabismus occurred in 76% and amblyopia in 48%. Associated findings included fourth cranial nerve palsy, partial third cranial nerve palsy, nystagmus, seizures, and deafness. Fourth cranial nerve palsies and manifest strabismus tended to cluster within single family units.

CONCLUSIONS

Strabismus and amblyopia are much more common with bilateral DRS than with unilateral DRS. There is much phenotypic variability among individuals within families with hereditary Duane's syndrome. The responsible gene(s) may affect the development of many cranial nerves. Genetic compounding may play a role in the phenotypic segregation seen within this large family.

A review of fluorescence in situ hybridization (FISH): current status and future prospects

Fluorescence in situ hybridization (FISH) is a powerful technique for detecting DNA or RNA sequences in cells, tissues and tumors. This molecular cytogenetic technique enables the localization of specific DNA sequences within interphase chromatin and metaphase chromosomes and the identification of both structural and numerical chromosome changes. FISH is quickly becoming one of the most extensively used cytochemical staining techniques owing to its sensitivity and versatility, and with the improvement of current technology and cost effectiveness, its use will surely continue to expand. Here we review the wide variety of current applications and future prospects of FISH technology.

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

Duane retraction syndrome (DRS) is a congenital eye-movement disorder characterized by a failure of cranial nerve VI (the abducens nerve) to develop normally, resulting in restriction or absence of abduction, restricted adduction, and narrowing of the palpebral fissure and retraction of the globe on attempted adduction. DRS has a prevalence of approximately 0.1% in the general population and accounts for 5% of all strabismus cases. Undiagnosed DRS in children can lead to amblyopia, a permanent uncorrectable loss of vision. A large family with autosomal dominant DRS was examined and tested for genetic linkage. After exclusion of candidate regions previously associated with DRS, a genomewide search with highly polymorphic microsatellite markers was performed, and significant evidence for linkage was obtained at chromosome 2q31 (D2S2314 maximum LOD score 11.73 at maximum recombination fraction. 0). Haplotype analysis places the affected gene in a 17.8-cM region between the markers D2S2330 and D2S364. No recombinants were seen with markers between these two loci. The linked region contains the homeobox D gene cluster. Three of the genes within this cluster, known to participate in hindbrain development, were sequenced in affected and control individuals. Coding sequences for these genes were normal or had genetic alterations unlikely to be responsible for the DRS phenotype. Identifying the gene responsible for DRS may lead to an improved understanding of early cranial-nerve development.

Exclusion of candidate genetic loci for Duane retraction syndrome

PURPOSE

To report preliminary linkage analysis of a large Hispanic family showing autosomal dominant inheritance for Duane retraction syndrome.

METHODS

Microsatellite analysis was used to examine genomic DNA isolated from members of a large family with autosomal dominant Duane retraction syndrome for linkage to candidate loci for Duane retraction syndrome. Chromosomes 4, 8, and 22 were chosen for study because previous reports had documented karyotypic abnormalities in unrelated patients with Duane retraction syndrome.

RESULTS

No lod scores over 0.5 were found for markers on chromosomes 4, 8, or 22. This analysis excludes these candidate sites.

CONCLUSIONS

Studies do not support linkage between Duane retraction syndrome in this family and chromosomes 4, 8, and 22. Duane retraction syndrome may result from mutations in a heterogeneous group of genes.

A molecular and FISH approach to determining karyotype and phenotype correlations in six patients with supernumerary marker(22) chromosomes

In a cytogenetic, molecular, and clinical study of patients with autosomal supernumerary marker chromosomes (SMC), 6 out of 72 (8.3%) were shown by fluorescence in situ hybridisation (FISH) to be derived from chromosome 22. PCR microsatellite analysis and FISH using primers and cosmids from proximal 22q showed 3 of the 6 to contain euchromatin. The first, a de novo nonmosaic bisatellited, dicentric SMC, was acsertained in a patient with cat eye syndrome and Duane anomaly. Microsatellite analysis showed the SMC was maternal in origin with euchromatin extending to D22S427, i.e., proximal to the DiGeorge syndrome critical region (DGSCR). The second, a nonmosaic bisatellited, dicentric marker, was found in a child with severe hypotonia and developmental delay and had been inherited from the patient's phenotypically normal father. FISH showed the SMC to contain euchromatin extending into the DGSCR. The third, a de novo SMC, was ascertained antenatally and was shown to contain 22q euchromatin extending distal to the DGSCR. The 19-week terminated fetus was phenotypically normal at autopsy. Two of the three SMC(22)s not containing detectable proximal 22q euchromatin were ascertained coincidentally in phenotypically normal individuals, whereas the third, the only mosaic with a minority euploid cell line, was found in a patient with mild developmental delay. These results suggest that SMC(22)s devoid of proximal 22q euchromatin are not associated with adverse phenotypic effects whereas SMC(22)s containing euchromatin may be found in individuals with phenotypes ranging from cat eye syndrome to normal.

Duane's retraction syndrome associated with chromosome 4q27-31 segment deletion

PURPOSE/METHOD

A 15-year-old boy with bilateral blepharoptosis, bilateral type 1 Duane's retraction syndrome, and mild learning difficulties underwent chromosomal analysis.

RESULTS/CONCLUSIONS

A de novo deletion of a segment of the long arm of chromosome 4 (4q27-31) was found. To our knowledge, no other individuals with this chromosome deletion have Duane's retraction syndrome. The chromosome defect lies close to the epidermal growth factor gene, 4q25, which was recently linked to Rieger's syndrome. We suggest that families with Duane's retraction syndrome should be assessed for linkage to the area of 4q27-31.