Surgical treatment of advanced chronic angle closure glaucoma in Weill-Marchesani syndrome

PURPOSE

To describe the surgical treatment of advanced chronic angle closure glaucoma in Weill-Marchesani syndrome.

PATIENTS AND METHODS

Two children with Weill-Marchesani syndrome (4 eyes) undergoing lensectomy, anterior vitrectomy, and sutured intraocular lens (IOL) and Molteno tube shunt surgery at Wills Eye Hospital were prospectively studied. Visual acuity and intraocular pressure (IOP) were recorded.

RESULTS

Both patients presented with increasing myopia and advanced glaucomatous damage. Laser iridotomy was ineffective in deepening the anterior chamber. The first patient developed a flat anterior chamber after trabeculectomy. At the 12-month follow-up visit, all 4 eyes had an important decrease in IOP and cupping after combined lensectomy, anterior vitrectomy, and sutured IOL and Molteno tube shunt placement. One eye had a transitory postoperative choroidal effusion and retinal detachment that resolved spontaneously.

CONCLUSIONS

Advanced chronic angle closure glaucoma in Weill-Marchesani syndrome may be treated with a combination of lensectomy, anterior vitrectomy, and sutured IOL and Molteno tube shunt surgery. In early cases, prophylactic peripheral iridotomies should be stressed.

Candidate high myopia loci on chromosomes 18p and 12q do not play a major role in susceptibility to common myopia

BACKGROUND

To determine whether previously reported loci predisposing to nonsyndromic high myopia show linkage to common myopia in pedigrees from two ethnic groups: Ashkenazi Jewish and Amish. We hypothesized that these high myopia loci might exhibit allelic heterogeneity and be responsible for moderate /mild or common myopia.

METHODS

Cycloplegic and manifest refraction were performed on 38 Jewish and 40 Amish families. Individuals with at least -1.00 D in each meridian of both eyes were classified as myopic. Genomic DNA was genotyped with 12 markers on chromosomes 12q21-23 and 18p11.3. Parametric and nonparametric linkage analyses were conducted to determine whether susceptibility alleles at these loci are important in families with less severe, clinical forms of myopia.

RESULTS

There was no strong evidence of linkage of common myopia to these candidate regions: all two-point and multipoint heterogeneity LOD scores were < 1.0 and non-parametric linkage p-values were > 0.01. However, one Amish family showed slight evidence of linkage (LOD>1.0) on 12q; another 3 Amish families each gave LOD >1.0 on 18p; and 3 Jewish families each gave LOD >1.0 on 12q.

CONCLUSIONS

Significant evidence of linkage (LOD> 3) of myopia was not found on chromosome 18p or 12q loci in these families. These results suggest that these loci do not play a major role in the causation of common myopia in our families studied.

A susceptibility locus for myopia in the normal population is linked to the PAX6 gene region on chromosome 11: a genomewide scan of dizygotic twins

Myopia is a common, complex trait with considerable economic and social impact and, in highly affected individuals, ocular morbidity. We performed a classic twin study of 506 unselected twin pairs and inferred the heritability of refractive error to be 0.89 (95% confidence interval 0.86-0.91). A genomewide scan of 221 dizygotic twin pairs, analyzed by use of optimal Haseman-Elston regression methods implemented by use of generalized linear modeling, showed significant linkage (LOD >3.2) to refractive error at four loci, with a maximum LOD score of 6.1 at 40 cM on chromome 11p13. Evidence of linkage at this locus, as well as at the other linkage peaks at chromosomes 3q26 (LOD 3.7), 8p23 (LOD 4.1), and 4q12 (LOD 3.3), remained the same or became stronger after model fit was checked and outliers were downweighted. Examination of potential candidate genes showed the PAX6 gene directly below the highest peak at the 11p13 locus. PAX6 is fundamental to identity and growth of the eye, but reported mutations usually result in catastrophic congenital phenotypes such as aniridia. Haplotype tagging of 17 single-nucleotide polymorphisms (SNPs), which covered the PAX6 gene and had common minor allele frequencies, identified 5 SNPs that explained 0.999 of the haplotype diversity. Linkage and association analysis of the tagging SNPs showed strong evidence of linkage for all markers with a minimum chi 21 of 7.5 (P=.006) but no association. This suggests that PAX6 may play a role in myopia development, possibly because of genetic variation in an upstream promoter or regulator, although no definite association between PAX6 common variants and myopia was demonstrated in this study.

Sequence variants in the transforming growth beta-induced factor (TGIF) gene are not associated with high myopia

PURPOSE

High myopia is a common complex-trait eye disorder, with implications for blindness due to increased risk of retinal detachment, macular degeneration, premature cataracts, and glaucoma. Mapping studies have identified at least four loci for nonsyndromic autosomal dominant high myopia at 18p11.31, 12q22-q23, 17q21-q23, and 7q36. The smallest haplotyped interval for these loci is that of the MYP2 locus on 18p11.31. Recently, the transforming growth beta-induced factor (TGIF) gene was reported to be a candidate gene for MYP2-associated high myopia in single-nucleotide polymorphism studies. The purpose of this study was to determine whether DNA sequence variants in the human TGIF gene are causally related to MYP2-associated high myopia.

METHODS

The protein coding regions and intron-exon boundaries of the human TGIF gene were sequenced using genomic DNA samples from MYP2 individuals (affected, unaffected) and external control subjects. The TGIF model used was the April 20, 2003, human genome National Center for Biotechnology Information (NCBI) build 33, which has 10 exons and encodes eight transcript variants. Polymorphic sequence changes were compared to those in the previous report. Reverse-transcription polymerase chain reaction (RT-PCR) was performed to validate TGIF gene expression in ocular tissues.

RESULTS

A total of 21 polymorphisms of TGIF were found by direct sequencing: 3 were missense, 2 were silent, 10 were not translated, 4 were intronic, and 2 were homozygous deletions. The 3 missense allelic variants were localized to exon 10 at positions 236C-->T(Pro-->Leu), 244C-->T(Pro-->Ser), and 245C-->T(Pro-->Leu). Silent mutations were observed in exon 10 at positions 177A-->G, 333C-->T. Ten polymorphisms were novel. No sequence alterations were exclusively associated with the affected disease phenotype. RT-PCR results confirmed expression of TGIF in RNA samples derived from human sclera, cornea, optic nerve, and retina.

CONCLUSIONS

TGIF is a known candidate gene for MYP2-associated high myopia, based on its mapped location within the MYP2 interval. Mutation analysis of the encoded TGIF gene for MYP2 autosomal dominant high myopia did not identify sequence alterations associated with the disease phenotype. Further studies of MYP2 candidate genes are needed to determine the gene that causes of this potentially blinding disorder.

X-linked high myopia associated with cone dysfunction

OBJECTIVE

Bornholm eye disease (BED) consists of X-linked high myopia, high cylinder, optic nerve hypoplasia, reduced electroretinographic flicker with abnormal photopic responses, and deuteranopia. The disease maps to chromosome Xq28 and is the first designated high-grade myopia locus (MYP1). We studied a second family from Minnesota with a similar X-linked phenotype, also of Danish descent. All affected males had protanopia instead of deuteranopia.

METHODS

X chromosome genotyping, fine-point mapping, and haplotype analysis of the DNA from 22 Minnesota family individuals (8 affected males and 5 carrier females) and 6 members of the original family with BED were performed. Haplotype comparisons and mutation screening of the red-green cone pigment gene array were performed on DNA from both kindreds.

RESULTS

Significant maximum logarithm of odds scores of 3.38 and 3.11 at theta = 0.0 were obtained with polymorphic microsatellite markers DXS8106 and DXYS154, respectively, in the Minnesota family. Haplotype analysis defined an interval of 34.4 cM at chromosome Xq27.3-Xq28. Affected males had a red-green pigment hybrid gene consistent with protanopia. We genotyped Xq27-28 polymorphic markers of the family with BED, and narrowed the critical interval to 6.8 cM. The haplotypes of the affected individuals were different from those of the Minnesota pedigree. Bornholm eye disease-affected individuals showed the presence of a green-red hybrid gene consistent with deuteranopia.

CONCLUSIONS

Because of the close geographic origin of the 2 families, we expected affected individuals to have the same haplotype in the vicinity of the same mutation. Mapping studies, however, suggested independent mutations of the same gene. The red-green and green-red hybrid genes are common X-linked color vision defects, and thus are unrelated to the high myopia and other eye abnormalities in these 2 families.

CLINICAL RELEVANCE

X-linked high myopia with possible cone dysfunction has been mapped to chromosome Xq28 with intervals of 34.4 and 6.8 centimorgan for 2 families of Danish origin.

Prevalence of myopia in local and international schools in Hong Kong

PURPOSE

This study aims to investigate genetic and environmental influences on physiological myopia by studying the difference in myopia prevalence between local schools and international schools in Hong Kong.

METHODS

Vision screening was carried out in local and international schools for students 13 to 15 years old. Types of refractive error were identified by visual acuity measurement, the presence of spectacles, a simple refraction, and the use of plus and minus ophthalmic lenses.

RESULTS

Three local schools and six international schools participated in the study. Two hundred eighty-nine students were from the local schools, and 789 students were from the international schools. Prevalence of myopia at the local schools ranged from 85 to 88%, whereas it ranged from 60 to 66% in the international schools. Students in the international schools were subdivided into Chinese origin, white, mixed Chinese, and Asian. Prevalence of myopia was highest in the Chinese group (82.8%) and lowest in the white group (40.5%). There was no age or gender difference in the prevalence of myopia.

CONCLUSIONS

Hong Kong Chinese students had a higher prevalence of myopia regardless of whether they studied in local or international schools when compared with other ethnic groups, such as whites. This further supports a genetic input into myopia development.

[Stickler syndrome with rapidly progressive mitral valve regurgitation: report of a case]

A 36-year-old man with Stickler syndrome who underwent mitral valve replacement for rapidly progressive mitral regurgitation due to prolapse of an anterior leaflet. Stickler syndrome is a relatively rare condition caused by a defective collagen gene and characterized by high myopia, sensorineural-hearing deficit and flattened facial features. The prevalence of mitral valve prolapse in Stickler syndrome is reported to be much higher than in the general population because of its connective tissue dysplasia. Mitral regurgitation rapidly and refractorily progresses. Prompt surgical treatment should be recommended to mitral regurgitation in Stickler syndrome, and mitral valve replacement with a prosthetic valve is a better selection than mitral valve plasty for tissue fragility.

Screening for differential gene expression during the development of form-deprivation myopia in the chicken

PURPOSE

To use the technique of differential gene display to analyze changes in gene expression that occur during the development of and recovery from form-deprivation myopia.

METHODS

The differential display-reverse transcriptase-polymerase chain reaction technique was used to detect cDNAs that are differentially expressed after 24 h (including 12 h in the light) after fitting with a diffuser to induce form-deprivation myopia. Messenger RNA levels were determined by quantitative Northern blotting in retinas after 11 days of form deprivation or in retinas where the diffusers had been removed the previous day.

RESULTS

Twenty-six differentially expressed genes were processed in our initial screen. Two of these, alphaB-crystallin and retinoic acid receptor-alpha, were studied further. Levels of alphaB-crystallin mRNA were increased on day 11 in retinas from form-deprived eyes relative to eyes of control chickens and were reduced to below those levels within 6 to 12 h after removal of the diffusers. Levels of retinoic acid receptor-alpha mRNA showed similar changes, except that after removal of the diffusers, the levels further increased.

CONCLUSIONS

The technique of differential gene display can be used to detect changes in gene expression during the regulation of eye growth. The response of alphaB-crystallin is particularly interesting because expression increases when eye growth is high and decreases when eye growth slows.

Myopia: precedents for research in the twenty-first century

The myopic eye is generally considered to be a vulnerable eye and, at levels greater than 6 D, one that is especially susceptible to a range of ocular pathologies. There is concern therefore that the prevalence of myopia in young adolescent eyes has increased substantially over recent decades and is now approaching 10-25% and 60-80%, respectively, in industrialized societies of the West and East. Whereas it is clear that the major structural correlate of myopia is longitudinal elongation of the posterior vitreous chamber, other potential correlates include profiles of lenticular and corneal power, the relationship between longitudinal and transverse vitreous chamber dimensions and ocular volume. The most potent predictors for juvenile-onset myopia continue to be a refractive error </=+0.50 D at 5 years of age and family history. Significant and continuing progress is being made on the genetic characteristics of high myopia with at least four chromosomes currently identified. Twin studies and genetic modelling have computed a heritability index of at least 80% across the whole ametropic continuum. The high index does not, however, preclude an environmental precursor, sustained near work with high cognitive demand being the most likely. The significance of associations between accommodation, oculomotor dysfunction and human myopia is equivocal despite animal models that have demonstrated that sustained hyperopic defocus can induce vitreous chamber growth. Recent optical and pharmaceutical approaches to the reduction of myopia progression in children are likely precedents for future research, for example progressive addition spectacle lens trials and the use of the topical M1 muscarinic antagonist pirenzepine.

[Prognostication of a complicated course of myopia in children]

The aim of the case study was to define the earliest criteria of the transformation of myopia into its aggravated form. Two related risk factors were isolated on the basis of a comprehensive examination of 135 children and teenagers with uncomplicated myopia of 0.5-16 d and with myopia complicated by different-type peripheral vitreochorioretinal dystrophies (PVCRD). They are primarily a reduced acoustic sclera density in the excavation zone and in the region of the posterior eye pole, diminished antioxidant reserve of the lachrymal fluid and heredity (presence of PVCRD in close relatives). Besides, a mild relationship was established between the eye fundus status in children and teenagers with myopia, on the one hand, and myopia progression rate, linear blood-flow velocity in the ciliary body, relative accommodation reserve and a value of the anterior-posterior eye axis, on the other hand. No reliable correlation was found between the eye fundus status and the below parameters: volumetric and linear blood flows in the ocular artery and in the posterior ciliary arteries, volumetric blood flow velocity in the ciliary body, intraocular pressure values, elastic elevation and rigidity factor. The most significant differences between the complicated and uncomplicated types of myopia in children were registered in its mild degree.

Cohen syndrome in the Ohio Amish

We describe eight members from two large Amish kindreds who share a phenotype characterized by early-onset pigmentary retinopathy and myopia, global developmental delay and mental retardation, microcephaly, short stature, hypotonia, joint hyperextensibility, small hands and feet, common facial appearance, and friendly disposition. Several of the children had intermittent granulocytopenia. The phenotypic occurrence in three siblings coupled with the increased coefficient of inbreeding in the Amish suggested that this disorder is autosomal recessive and due to a single founder allele. Despite similarity to the clinical features of Cohen syndrome, experienced dysmorphologists attending the 23rd David W. Smith Workshop suggested the facial gestalt of the Amish children was inconsistent with this diagnosis. We mapped the locus responsible for these individuals' phenotype to chromosome 8q22-q23, which contains the recently discovered Cohen syndrome gene, COH1. Complete sequencing of the COH1 gene identified a likely disease-causing frameshift mutation and a missense mutation in the Amish patients. A comparison of features among different Cohen syndrome populations with shared linkage to the COH1 locus or known COH1 gene mutations may allow for the determination of improved clinical criteria on which to suspect the diagnosis of Cohen syndrome. We conclude that facial gestalt seems to be an unreliable indicator of Cohen syndrome between ethnic populations, although it is quite consistent among affected individuals within a particular ethnic group. Other features common to almost all individuals with proven COH1 mutations, such as retinal dystrophy, myopia, microcephaly, mental retardation, global developmental delay, hypotonia, and joint hyperextensibility appear to be better clinical indicators of this disorder.

Knobloch syndrome: novel mutations in COL18A1, evidence for genetic heterogeneity, and a functionally impaired polymorphism in endostatin

Knobloch syndrome (KNO) is an autosomal recessive disorder characterized by high myopia, vitreoretinal degeneration with retinal detachment, and congenital encephalocele. Pathogenic mutations in the COL18A1 gene on 21q22.3 were recently identified in KNO families. Analysis of two unrelated KNO families from Hungary and New Zealand allowed us to confirm the involvement of COL18A1 in the pathogenesis of KNO and to demonstrate the existence of genetic heterogeneity. Two COL18A1 mutations were identified in the Hungarian family: a 1-bp insertion causing a frameshift and a premature in-frame stop codon and an amino acid substitution. This missense variant is located in a conserved amino acid of endostatin, a cleavage product of the carboxy-terminal domain of collagen alpha 1 XVIII. D1437N (D104N in endostatin) likely represents a pathogenic mutation, as we show that the endostatin N104 mutant is impaired in its affinity towards laminin. Linkage to the COL18A1 locus was excluded in the New Zealand family, providing evidence for the existence of a second KNO locus. We named the second unmapped locus for Knobloch syndrome KNO2. Mutation analysis excluded COL15A1, a member of the multiplexin collagen subfamily similar to COL18A1, as being responsible for KNO2.

A novel mutation in the PITX2 gene in a family with Axenfeld-Rieger syndrome

PURPOSE

To determine the underlying genetic cause of Axenfeld-Rieger syndrome (ARS) in a three-generation family.

INTRODUCTION

ARS is a multisystem, autosomal dominant disorder characterized by specific ocular and non-ocular anomalies sometimes caused by mutations in the transcription factor gene, PITX2.

METHODS

The three coding exons of the PITX2 gene, i.e., exons 2, 3, and 4, in affected and unaffected subjects were amplified by polymerase chain reaction (PCR) and sequenced. The PCR products of exon 4 were subcloned and sequenced to confirm the nature of the mutation.

RESULTS

A deletion of thymine (T) 1261 was identified, creating a frameshift mutation in codon 227. This change is predicted to create 11 novel amino acids downstream, followed by premature truncation of the protein.

CONCLUSIONS

This mutation highlights the functional importance of a conserved 14-amino acid sequence at the C-terminus of the protein thought to be important in repressing DNA binding and in protein-protein interactions.

[Variations of the zinc finger protein 161 gene in Chinese with or without high myopia]

To investigate the association between variations of ZFP161 gene and high myopia, A total of 204 probands with simple high myopia(< or = -6.0 dipoters) were collected while 116 normal persons from different families without high myopia or related disease were used as controls. Genomic DNA was prepared from the peripheral leucocytes. The coding sequences of ZFP161 gene in 320 subjects were analyzed by using exon-by-exon PCR-heteroduplex-SSCP analysis. Identification of the Variations by cloning and sequencing, combinated with controls and family analysis, was used to disclose the correlation between ZFP161 gene and high myopia. A mutation of ZFP161 gene was identified as an insertion of AT before the 58th nucleotide of intron 1 (IVS1 58-59)(1/204) and a variation of ZFP161 gene was identified as a heterozygous C to A of the 168th nucleotide in exon 2 (Codon56, GCC-->GCA, Ala56Ala). Ala56Ala is a non-sense mutation identified in 5 of the 204 patients and 3 of 116 controls. No evidence shows that these variations are responsible for high myopia.

Molecular biology of myopia

Experiments in animal models of myopia have emphasised the importance of visual input in emmetropisation but it is also evident that the development of human myopia is influenced to some degree by genetic factors. Molecular genetic approaches can help to identify both the genes involved in the control of ocular development and the potential targets for pharmacological intervention. This review covers a variety of techniques that are being used to study the molecular biology of myopia. In the first part, we describe techniques used to analyse visually induced changes in gene expression: Northern Blot, polymerase chain reaction (PCR) and real-time PCR to obtain semi-quantitative and quantitative measures of changes in transcription level of a known gene, differential display reverse transcription PCR (DD-RT-PCR) to search for new genes that are controlled by visual input, rapid amplification of 5' cDNA (5'-RACE) to extend the 5' end of sequences that are regulated by visual input, in situ hybridisation to localise the expression of a given gene in a tissue and oligonucleotide microarray assays to simultaneously test visually induced changes in thousands of transcripts in single experiments. In the second part, we describe techniques that are used to localise regions in the genome that contain genes that are involved in the control of eye growth and refractive errors in mice and humans. These include quantitative trait loci (QTL) mapping, exploiting experimental test crosses of mice and transmission disequilibrium tests (TDT) in humans to find chromosomal intervals that harbour genes involved in myopia development. We review several successful applications of this battery of techniques in myopia research.

Evidence for an "epidemic" of myopia

INTRODUCTION

It has been widely suggested that the prevalence of myopia is growing worldwide, and that the increases observed in East Asia, in particular, are sufficiently severe as to warrant the term "epidemic". Data in favour of a cohort effect in myopia prevalence are reviewed, with attention to significant shortcomings in the quality of available evidence. Additional factors contributing to myopia prevalence, including near work, genetics and socioeconomic status, are detailed.

MATERIALS AND METHODS

Medline search of articles regarding myopia prevalence, trends and mechanisms.

RESULTS

Age-related changes in myopia prevalence (increase during childhood, and regression in the fifth and sixth decades) are discussed as an alternative explanation for cross-sectional patterns in myopia prevalence. There have only been a handful of studies that have examined the relative contribution of longitudinal changes in refraction over life and birth cohort differences on age-specific myopia prevalence as measured in cross-sectional studies. Available data suggest that both longitudinal changes and cohort effects may be present, and that their relative contribution may differ in different racial groups.

CONCLUSIONS

In view of the relatively weak evidence in favour of a large cohort effect for myopia in East Asia, and the even greater lack of evidence for increased prevalence of secondary ocular pathology, there appears to be inadequate support for large-scale interventions to prevent or delay myopia at the present time.

Dissecting the genetics of human high myopia: a molecular biologic approach

PURPOSE

Despite the plethora of experimental myopia animal studies that demonstrate biochemical factor changes in various eye tissues, and limited human studies utilizing pharmacologic agents to thwart axial elongation, we have little knowledge of the basic physiology that drives myopic development. Identifying the implicated genes for myopia susceptibility will provide a fundamental molecular understanding of how myopia occurs and may lead to directed physiologic (ie, pharmacologic, gene therapy) interventions. The purpose of this proposal is to describe the results of positional candidate gene screening of selected genes within the autosomal dominant high-grade myopia-2 locus (MYP2) on chromosome 18p11.31.

METHODS

A physical map of a contracted MYP2 interval was compiled, and gene expression studies in ocular tissues using complementary DNA library screens, microarray matches, and reverse-transcription techniques aided in prioritizing gene selection for screening. The TGIF, EMLIN-2, MLCB, and CLUL1 genes were screened in DNA samples from unrelated controls and in high-myopia affected and unaffected family members from the original seven MYP2 pedigrees. All candidate genes were screened by direct base pair sequence analysis.

RESULTS

Consistent segregation of a gene sequence alteration (polymorphism) with myopia was not demonstrated in any of the seven families. Novel single nucleotide polymorphisms were found.

CONCLUSION

The positional candidate genes TGIF, EMLIN-2, MLCB, and CLUL1 are not associated with MYP2-linked high-grade myopia. Base change polymorphisms discovered with base sequence screening of these genes were submitted to an Internet database. Other genes that also map within the interval are currently undergoing mutation screening.

Astigmatic Axis is Related to the Level of Spherical Ametropia

PURPOSE

Against-the-rule (ATR) astigmatism has been shown to be a risk factor for subsequent myopia development. In this study, we evaluated the relationship between astigmatic axis and the level of spherical ametropia in both myopes and hypermetropes.

METHODS

Astigmatic axes were analyzed in two distinct cohorts. First, 53 high myopes from families that were recruited for linkage analysis were compared with an age-matched control group derived from family members. Second, cross-sectional data were analyzed for 90,884 subjects attending 19 optometric practices in the north of England. Initially, the relationship between astigmatic axis and cylinder power and between axis and sphere power were analyzed in 21- to 40-year olds and 21- to 30-year olds, respectively, to control for the effects of age. Multivariate logistic regression analysis was then performed using data for all compound astigmats in the cohort to examine the effect of sphere power, cylinder power, age, and sex on the odds of subjects having either ATR or with-the-rule (WTR) astigmatism.

RESULTS

In the genetic study cohort, there was an excess of WTR astigmats in the high myopes compared with controls, but this only reached significance for the right eye. In the much larger optometric practice sample, the association of WTR astigmatism with high myopia was highly significant. A parallel increase in WTR astigmatism was also found for high hypermetropes. In addition, the odds of having WTR astigmatism were increased if subjects were young or had a high cylinder power. ATR astigmatism occurred more often with increasing age and in subjects with lower spherical ametropia. Indeed, for 21- to 30-year-old subjects with low myopia (> or =-2.00 DS in the least minus meridian), ATR occurred more often than WTR astigmatism.

CONCLUSION

Astigmatic axis was found to be related to the level of ametropia, with both a higher spherical component or higher cylinder power increasing the odds of astigmatism being WTR. Low ametropes, particularly myopes, were more likely to have axes ATR.

Chromosomal anomalies on 6p25 in iris hypoplasia and Axenfeld-Rieger syndrome patients defined on a purpose-built genomic microarray

In many inherited diseases, the same phenotype can be produced both by single-base changes and by large deletions, or in some cases by duplications. Routine high-throughput sequencing can now detect small mutations relatively easily in a diagnostic setting, but deletions and duplications in the 50-500-kb region remain a more difficult problem. We have explored the application of array-CGH to the detection of such changes on a set of 20 samples consisting of patients with eye diseases associated with changes on chromosome 6p25 together with unaffected individuals, as well as two samples from tuberous sclerosis 2 (TSC2)-affected patients. We developed a microarray consisting of degenerate oligonucleotide primer (DOP)-PCR products from 260 human genomic clones, including BACs, PACs, and cosmids. In a masked study, chromosome changes in patients with iris hypoplasia (duplication) and Axenfeld-Rieger syndrome (deletion) were unequivocally distinguished from controls. Of the 20 6p25 samples analyzed, 19 were analyzed correctly (10 duplication cases, two deletions, and seven normals), while one individual failed to give a result because of poor hybridization. The extent of the duplication or deletion estimated was similar to that obtained by independent and much more time-consuming FISH experiments. On the other hand, deletions in the two TSC2-affected samples, previously mapped by DNA molecular combing, were not detected on the array, possibly due to the repeat content of that region. Excluding the 16p13 cosmids, consistent results were obtained from all other cosmid clones; the potential for producing affordable disease-specific diagnostic microarray as an adjunct to diagnosis is discussed.

Using natural STOP growth signals to prevent excessive axial elongation and the development of myopia

Myopia is emerging as a major public health issue due to its increasing prevalence and long-term pathological outcomes. Prevention must focus on limiting excessive axial elongation which is the cause of both myopic refractive error and its pathological outcomes. The increasing prevalence appears to be due to environmental changes involving near work, rather than to a genetic failure of emmetropisation. Attempts to control the progression of myopia optically have been unsuccessful; the only available preventive regime involves the use of atropine eye drops. This regime has short-term side effects, and since the site and mechanism of action of muscarinic antagonists are unclear, there are concerns about its long-term safety. Recent studies on natural STOP growth signals suggest that they are evoked by relatively brief periods of imposed myopic defocus, and can overcome strong pressures towards increased axial elongation. While STOP signals have only been successfully used in chickens to prevent excessive axial elongation, similar signals are generated in mammals and non-human primates. Further studies may define the conditions under which this approach could be used to prevent the development of myopia in humans.

[The SNPs analysis of encoding sequence of interacting factor gene in Chinese population]

OBJECTIVE

To screen the variations of TG interacting factor(TGIF) gene in encoding sequence in Chinese high myopia patients and normal controls and to analyze the SNPs of TGIF gene encoding sequence in Chinese population.

METHODS

Genomic DNA was collected from 204 probands with high myopia and 112 unrelated persons without high myopia. The coding sequences of TGIF gene in 316 subjects were analyzed by using exon-by-exon PCR heteroduplex-SSCP analysis and sequencing.

RESULTS

There were 3 types of SNP and one single nucleotide mutation in the coding sequence of TGIF gene: IVS-2 nt350 G --> T(36/204), codon140 CCA --> CCG; Pro140Pro codon163 CCG --> CTG;Pro163Leu and codon126 GTG --> GCG; Val126Ala(1/204). The SNPs of codon140 CCA --> CCG and codon163 CCG --> CTG were composed of 3 alleles and 5 genotypes in Chinese population which abide by Hardy-Weinberg law.

CONCLUSION

There was no evidence to prove that mutations in the TGIF gene are responsible for the high myopia in Chinese. Three SNPs of coding sequence TGIF gene in Chinese population abide by Hardy-Weinberg law.

The mystery of myopia

Published data from all parts of the world show that myopia is rare before school age, gradually increases during school life and reaches its highest level of prevalence during the years of most intense study at university. It is widely held that continuous reading harms the eyes, but none of the attempts made so far to reduce accommodative fatigue by introducing pauses during reading and teaching, eye exercises, etc. have been successful in reducing the number of children who develop myopia. However, we should not exclude the possibility that the introduction into schools of better tables, better lighting, more breaks and more sport has not only benefited the general health of children, mentally as well as physically, but has also decreased the development and progression of myopia. More research in this area is needed, but relevant protocols are difficult to establish. The aetiology of myopia is multifactorial and both genes and environment play important roles. Twin studies indicate a strong genetic influence and a weak environmental impact, while extreme myopia prevalences among selected population groups (university students) point to the opposite.

Interactions of genes and environment in myopia

Myopia is a condition in which the eye is too long for the focal length of cornea and lens, and the plane of sharp focus ends up in front of the retina. Given that the growth of the length of the eye is normally controlled with extreme precision by an image-processing feedback mechanism in the retina, myopia can either be the result of inappropriate visual stimulation, genetically determined changes in the gain or offset of the feedback loops or of inappropriate responses of the target tissues. There is no doubt that an environmental component is involved and extended near work appears to be the major risk factor. However, there is also no doubt that myopia is inherited since myopic parents are much more likely to have myopic children, and myopia is far more frequent in Asian populations than in the USA or Europe, even if groups are compared that have performed similar amounts of near work. A number of systemic or ophthalmic diseases are associated with myopia, indicating that metabolic conditions may interfere either with the gains of the feedback loops or the responses of the target tissue, the sclera. Since there is still no therapy against myopia development, research is directed toward the identification of genes that control the axial elongation of the eye.

Donnai-Barrow syndrome: four additional patients

In 1993, Donnai and Barrow reported a new syndrome in two sets of sibs and in an unrelated child, including diaphragmatic hernia, exomphalos, absent corpus callosum, hypertelorism, myopia, and sensorineural deafness. Since then, only four similar patients have been documented. We describe four additional patients, including two sibling pairs from healthy parents. This report firmly establishes this syndrome as a distinct clinical entity and provides further evidence for its previously postulated autosomal recessive inheritance.

Focal polymicrogyria, continuous spike-and-wave discharges during slow-wave sleep and Cohen syndrome: a case report

Cohen syndrome is a rare genetic disorder consisting of truncal obesity, hypotonia, mental retardation, characteristic facial appearance and ocular anomalies. Other diagnostic clinical features include narrow hands and feet, low growth parameters, neutropenia and chorioretinal dystrophy. Here, we report an 18-year-old male with Cohen syndrome associated with focal polymicrogyria and continuous spike-and-wave discharges during slow-wave sleep.