Evidence of clinical and genetic heterogeneity in autosomal dominant congenital cerulean cataracts

Autosomal dominant cerulean cataracts (ADCC) have previously been mapped to two loci: one on chromosome 17q24 and the other on chromosome 22q11.2-q12.2, which includes the beta-B2 crystallin (CRYBB2) candidate gene. Using polymorphic markers in these regions (D17S802, D17S836, D17S1806 and CRYBB2, D22S258) for linkage analysis, we excluded these loci in a large Moroccan family presenting with an unusual form of ADCC with early onset of lens opacities and rapid evolution. This finding confirms the clinical and genetic heterogeneity of autosomal dominant congenital cerulean cataracts.     

常染色体显性遗传先天性白内障相关基因的研究进展

先天性白内障是由于胚胎期晶状体代谢异常而导致的自身透明度下降的致盲性疾病,遗传因素与疾病的发生、发展有很大的联系.目前研究发现先天性白内障的发生至少与22个基因的变异有关,其中以常染色体显性遗传为主,涉及的基因包括晶状体蛋白基因(CRY)、缝隙连接通道蛋白基因(GJA)、膜蛋白基因(MIP)、细胞骨架蛋白基因(BFSP)和转录调节因子基因等.本文对近几年来关于常染色体显性遗传先天性白内障致病基因方面的研究进行综述.     

Clinical and genetic heterogeneity in autosomal dominant cataract

AIMS: To determine the different morphologies of autosomal dominant cataract (ADC), assess the intra- and interfamilial variation in cataract morphology, and undertake a genetic linkage study to identify loci for genes causing ADC and detect the underlying mutation. METHODS: Patients were recruited from the ocular genetic database at Moorfields Eye Hospital. All individuals underwent an eye examination with particular attention to the lens including anterior segment photography where possible. Blood samples were taken for DNA extraction and genetic linkage analysis was carried out using polymorphic microsatellite markers. RESULTS: 292 individuals from 16 large pedigrees with ADC were examined, of whom 161 were found to be affected. The cataract phenotypes could all be described as one of the eight following morphologies-anterior polar, posterior polar, nuclear, lamellar, coralliform, blue dot (cerulean), cortical, and pulverulent. The phenotypes varied in severity but the morphology was consistent within each pedigree, except in those affected by the pulverulent cataract, which showed considerable intrafamilial variation. Positive linkage was obtained in five families; in two families linkage was demonstrated to new loci and in three families linkage was demonstrated to previously described loci. In one of the families the underlying mutation was isolated. Exclusion data were obtained on five families. CONCLUSIONS: Although there is considerable clinical heterogeneity in ADC, the phenotype is usually consistent within families. There is extensive genetic heterogeneity and specific cataract phenotypes appear to be associated with mutations at more than one chromosome locus. In cases where the genetic mutation has been identified the molecular biology and clinical phenotype are closely associated.     

Evidence of genetic heterogeneity in autosomal recessive congenital fibrosis of the extraocular muscles

PURPOSE: Autosomal recessive congenital fibrosis of the extraocular muscles (CFEOM2) has been described in families from Saudi Arabia. Affected individuals have ptosis and exotropic ophthalmoplegia, and their disease has been mapped to chromosome 11q13. Here, we describe the phenotypic findings in a similarly affected Yemenite family and analyze the family for linkage to the CFEOM2 locus, as well as to the autosomal dominant CFEOM1 and CFEOM3 loci on chromosomes 12cen and 16q24, respectively. METHODS: The family was ascertained through two affected daughters. There are four unaffected siblings, and the parents are consanguineous. Each family member was examined, and linkage analysis was performed using markers from the CFEOM1, CFEOM2, and CFEOM3 loci. RESULTS: Both affected daughters have congenital bilateral ophthalmoplegia. The 15-month-old proband has restrictive exotropia. She fixates with either eye in abduction and with a compensatory head turn to the opposite side. Her 4-year-old sister has a small exotropia and severely limited eye movements. All other family members have normal ophthalmologic examinations. Genetic analysis excluded linkage of the family's disease to the CFEOM2 and CFEOM3 loci. A lod score of 2.0 (the maximum possible, given the family size and structure), was obtained at the CFEOM1 locus, and the alleles reduced to homozygosity in both affected daughters and none of the other children. CONCLUSIONS: These data establish that there is genetic heterogeneity in autosomal recessive CFEOM and suggest that this second recessive locus may be allelic to the autosomal dominant CFEOM1 locus at 12cen.     

Choroidal Thickening During Young Adulthood and Baseline Choroidal Thickness Predicts Refractive Error Change

PurposeThe purpose of this study was to explore the age-related change in choroidal thickness (ChT) and test the hypothesis that baseline ChT is predictive of refractive error change in healthy young adults.MethodsParticipants underwent spectral-domain optical coherence tomography (SD-OCT) imaging and autorefraction at 20 (baseline) and 28 years old. The enhanced depth imaging mode on the SD-OCT was used to obtain images of the choroid. Scans were exported from the SD-OCT and analyzed with a custom software that automatically measures the central ChT. The longitudinal change in subfoveal ChT and association between baseline subfoveal ChT and 8-year change in refractive error (spherical equivalent) were determined using linear mixed models.ResultsIn total, 395 eyes of 198 participants (44% men; 18–22 years at baseline) were included. Over 8 years, mean spherical equivalent decreased by 0.25 diopters (D) and axial length increased by 0.09 mm. Subfoveal choroid thickened by 1.3 µm/year (95% confidence interval [CI] = 0.6–2.0), but this was reduced by 0.9 µm/year (95% CI = 1.6–0.2) for every 1 mm increase in axial length. For every 10 µm increase in baseline ChT, average annual change in spherical equivalent and axial length reduced by 0.006 D/year and 0.003 mm/year, respectively.ConclusionsIn a community-based cohort of young adults, the choroid continued to change during early adulthood. Choroidal thickening was less in eyes that were longer at baseline, and the choroid thinned in eyes that showed myopia progression. The association between baseline ChT and longitudinal changes in spherical equivalent and axial length supports the hypothesis that ChT may be predictive of refractive error development and/or myopia progression.     

常染色体显性遗传眼球震颤家系的临床表型及致病基因的研究

目的　研究１个中国人常染色体显性遗传性眼球震颤家系的临床特点,并通过候选基因直接测序的方法对该家系的致病基因及发病机制进行研究。方法　选择１个先天性眼球震颤家系,对家系所有成员进行全身检查及视力、眼位、眼球运动、眼球震颤中间带、验光等眼科的相关检查后,从家系中每一代各选１例患者（包括先证者）及正常人,进行候选基因ＦＲＭＤ７、ＧＰＲ１４３与ＰＡＸ６基因的外显子测序。结果　家系患者的眼球震颤为水平冲动型,并且具有中间带。除了先证者有部分眼组织缺损及小眼球等异常外,其余患者的眼前节均未见明显发育异常。家系患者ＰＡＸ６基因第７外显子的第３８２碱基发生了杂合突变（ｃ．Ｃ３８２Ｔ）,从而引起了氨基酸的改变（ｐ．Ｒ１２８Ｃ）,该突变可能影响了ＰＡＸ６蛋白与其调控的下游基因的调控序列的结合,进而导致ＰＡＸ６基因功能异常,影响眼部发育。结论　该常染色体显性遗传性眼球震颤家系的致病基因为ＰＡＸ６基因。     

Genetic linkage analysis of autosomal dominant congenital cataracts with lens-specific DNA probes and polymorphic phenotypic markers

The authors studied a four-generation family with autosomal dominant congenital cataracts (ADCCs) using linkage analysis with 23 polymorphic phenotypic markers and DNA restriction fragment length polymorphisms (RFLPs) detected by lens-specific DNA probes. A total of 19 family members were studied and the ten affected members had embryonal lens opacities. Close linkage was rejected with DNA probes encoding beta-crystallin, gamma-crystallin, and the major intrinsic protein of the lens fiber membrane (MIP) excluding defects of these genes as the cause of the cataract in this family. No statistically significant lod scores were produced with the polymorphic phenotypic markers. These results support the genetic heterogeneity of ADCCs.     

中国南方先天性白内障一家系GJA8基因C>G新突变

目的 对一个常染色体显性遗传先天性白内障（ADCC）家系进行候选基因筛查,以期寻找其可能的致病基因。设计 实验研究。研究对象 一个中国南方ADCC家系。方法 应用聚合酶链反应（PCR）和DNA直接测序方法,对该家系进行ADCC常见致病基因突变筛查。主要指标 基因序列。结果 临床眼科检查显示该家系先天性白内障类型为核性白内障。候选基因序列测定显示在GJA8基因c.565位置上存在C>G的突变,该突变导致在缝隙连接蛋白Cx50 p.189位置上的脯氨酸突变为丙氨酸,此氨基酸改变位点位于缝隙连接蛋白结构中第二个细胞外段。而该家系中非患者和100名对照者基因组序列均无此改变。结论 位于GJA8 的c.565C>G突变是导致此先天性白内障家系可能的致病原因,缝隙连接蛋白第二个胞外结构域对晶状体的透明性起着重要作用。（眼科, 2013, 22: 86-89）     

常染色体显性遗传性粉尘状白内障致病基因的研究进展

常染色体显性遗传性粉尘状白内障是常见的眼部疾病,它通常使人失明,其表型是分布于晶状体的不同部位像粉尘样的混浊。本文就常染色体显性遗传性粉尘状白内障的相关蛋白、基因突变作一综述。     

Evidence for genetic heterogeneity in families with congenital motor nystagmus (CN)

Background: Wolfram syndrome is characterized by optic atrophy, insulin dependent diabetes mellitus, diabetes insipidus and deafness. There are several other associated conditions reported in the literature, but congenital or early childhood cataracts are not among them.

Materials and methods: Observational case series with confirmatory genetic analysis.

Results: A pair of siblings, followed over 17 years, who manifest congenital or early childhood cataracts, diabetes insipidus, diabetes mellitus, optic atrophy, and deafness. They are both compound heterozygotes for mutations (V415 deletion and A684V substitution) in the WFS1 gene. Their father has congenital sensorineural hearing loss and developed optic atrophy. He is heterozygous for A684V in WFS1.

Conclusions: Wolfram syndrome should be in the differential diagnosis of genetic syndromes associated with congenital and early childhood cataracts. Here, we report on a mother who is a phenotypically normal carrier of an autosomal recessive Wolfram syndrome gene, and a father who has some of the findings of the syndrome and carries a single mutation that appears to be responsible for his hearing loss and optic atrophy. Their 2 children are compound heterozygotes and manifest the full Wolfram syndrome, in addition to cataracts.     

Factors influencing willingness to participate in ophthalmic clinical trials and strategies for effective recruitment

AIM: To explore the factors influencing individuals’ willingness to participate in ophthalmic clinical trials. METHODS: A questionnaire survey was conducted from January to April 2021 among patients and their family members at Zhongshan Ophthalmic Center, Sun Yat-sen University, in Guangzhou, China. The survey gathered data on respondents’ willingness, demographic and socioeconomic profiles, as well as their reasons and concerns regarding engagement in clinical trials. RESULTS: Of the 1078 residents surveyed (mean age 31.2±13.1y; 65.8% females) in Guangzhou, 749 (69.5%) expressed a willingness to participate in future ophthalmic clinical trials. Specific characteristics associated with greater willingness included a younger age, lower annual income, higher education, prior participation experience, previous ophthalmic treatment, and a better understanding of clinical trials. With the exception of age, these characteristics were significantly linked to a higher willingness. The primary barrier to participation, expressed by 64.8% of those willing and 54.4% of those unwilling, was “Uncertain efficacy”. In terms of motivations, the willing group ranked “Better therapeutic benefits” (35.0%), “Professional monitoring” (34.3%), and “Trust in healthcare professionals” (33.1%) as their top three reasons, whereas the unwilling participants indicated “Full comprehension of the protocol” (46.2%) as the key facilitator. CONCLUSION: This study reveals a substantial willingness to participate in ophthalmic clinical trials and demonstrates the predictive role of demographic and socioeconomic factors. Variations in motivators and concerns between willing and unwilling participants highlight the significance of tailored recruitment strategies. Importantly, the need for and trust in healthcare professionals stand out as powerful motivations, underscoring the importance of enhancing physician-patient relationships, adopting patient-centered communication approaches, and addressing individualized needs to improve accrual rates.     

Statistical evaluation of visual functions in dominant and recessive autosomal pigmentary retinopathy

A statistical study of the progress of fundus lesions and functional loss in relation with age and with inheritance modus was performed in patients with pigmentary retinopathy. A three-way interaction was found between following parameters: (1) inheritance modus, age and pigment anomalies of the fundus; (2) inheritance modus, age and visual field; (3) inheritance modus, age and ERG; (4) inheritance modus, vision and ERG; (5) inheritance modus, dark adaptation and visual field.     

晶状体蛋白基因在一先天性白内障家系中的突变筛查

目的研究晶状体蛋白基因与先天性白内障的关系。方法收集1个先天性白内障家系,制备外周血白细胞基因组DNA。除对CRYGD基因直接测序外,在距离已知晶状体蛋白基因5个厘摩范围内选取微卫星标记进行连锁分析,计算微卫星位点与致病基因之间的最大优势对数值(LOD SCORE),来确定晶状体蛋白基因与此家系致病基因的关系。结果当重组分数分别为0.1、0.2、0.3、0.4时,所选取的位于晶状体蛋白基因附近的14个微卫星位点与该家系致病基因之间连锁的LOD值均为负值,故排除连锁。CRYGD基因测序后在基因编码区及启动子、内含子与外显子连接处的剪切位点均未见任何碱基改变。结论晶状体蛋白基因非此家系的致病基因,为进一步定位与克隆该家系的致病基因,需进行全基因组扫描,以探求先天性白内障的分子发病机制。     

A novel mutation of p.F32I in GJA8 in human dominant congenital cataracts

AIM: To identify a causative mutation in a three-generation family with autosomal dominant congenital total cataract and dissect the molecular consequence of the identified mutation. METHODS: Clinical and ophthalmological examinations were performed on the affected and unaffected family members. Mutation were screened in recruited family members by polymerase chain reaction (PCR) of the two reported genes (CRYAA and GJA8) which were linked to human total cataracts and direct sequencing of the PCR product. The molecular consequences of the identified mutation was dissected. The plasmids carrying wild-type and mutant mouse ORF of Gja8, coding for connexin 50 (Cx50), were generated and ectopic expressed in 293 cells. Recombinant protein expression and cellular localization of recombinated Cx50 were assessed by confocal microscopy. RESULTS: Clinical and ophthalmological examinations were performed on the affected and unaffected family members. Mutation were screened in recruited family members by PCR of the two reported genes (CRYAA and GJA8) which were linked to human total cataracts and direct sequencing of the PCR product. The molecular consequences of the identified mutation was dissected. The plasmids carrying wild-type and mutant mouse ORF of Gja8, coding for Cx50, were generated and ectopic expressed in 293 cells. Recombinant protein expression and cellular localization of recombinated Cx50 were assessed by confocal microscopy. CONCLUSION: This study has identified a novel cataract mutation in GJA8, which adds a novel mutation to the existing spectrum of Cx50 mutations with cataract. The molecular consequences of p.F32I mutation in GJA8 exclude instability and the mislocalization of mutant Cx50 protein.     

PAX6基因在一先天性无虹膜家系中的突变筛查

目的研究PAX6基因突变是否是导致一先天性无虹膜家系致病的原因。方法收集一先天性无虹膜家系,制备外周血基因组DNA,PCR扩增PAX6基因的外显子及其邻近的内含子,应用单链构象多态性（SSCP）法检测,如果发现变异条带,将相应的扩增产物回收并纯化后进行PAX6基因测序。测序结果与GenBank公布的PAX6基因正常序列比对,寻找有无突变。结果本家系43名成员中有8例患病,遗传方式符合常染色体显性遗传特点,40岁以上的4例患者眼压高于35mmHg。所有患者中未发现全身并发症。在家系所有患者中均未发现异常条带。结论 PAX6基因与该先天性无虹膜家系无关。该家系的致病基因有待进一步通过全基因组扫描的方法来确定。     

Further evidence of genetic heterogeneity in familial exudative vitreoretinopathy; exclusion of EVR1, EVR3, and EVR4 in a large autosomal dominant pedigree

BACKGROUND/AIMS: Familial exudative vitreoretinopathy (FEVR) is an inherited blinding condition characterised by abnormal development of the retinal vasculature. The aim of this study was to perform linkage analysis in a large family affected with FEVR to determine whether the mutation involved was in one of the three known autosomal dominant FEVR loci or in another as yet unidentified gene. METHODS: Genomic DNA samples from family members were polymerase chain reaction (PCR) amplified with fluorescently tagged microsatellite markers spanning the EVR1/EVR4 locus (11q13-14) and the EVR3 locus (11p12-13). The resulting PCR products were resolved using an automated DNA sequencer and the alleles sized. These data were used to construct haplotypes across each locus and linkage analysis was performed to prove or exclude linkage. RESULTS: The clinical evaluation in this family suggested features typical of FEVR, with deficient peripheral retinal vascularisation being the common phenotype in all affected individuals. However, linkage analysis proved that this family has a form of FEVR genetically distinct from the EVR1, EVR3 and EVR4 loci. CONCLUSION: The exclusion of linkage in this family to any of the known FEVR loci proves the existence of a fourth locus for autosomal dominant FEVR and shows that this rare disorder is far more heterogeneous than previously thought.     

一特殊表型的常染色体显性遗传先天性白内障家系致病基因的筛选与鉴定

背景遗传因素是先天性白内障的主要致病因素之一,致病基因的筛查是研究先天性白内障发病分子机制的重要步骤。目的明确一结晶样晶状体混浊的先天性常染色体显性遗传白内障（ADCC）家系的致病基因。方法收集山西省榆社县一个四代先天性结晶样混浊白内障家系22名成员,其中患者10例。在获得知情同意后,该家系成员进行家系调查以确定遗传方式。经裂隙灯显微镜检查和常规眼科临床检查确定表型。采集其中17例家系成员的外周静脉血5ml并提取DNA,ADCC的17个已知致病基因周围选取22个荧光标记的微卫星,通过对微卫星标志物的扩增和基因型分析对该家系进行基因两点连锁分析,并计算对数优势评分（LOD）值。对筛选的候选基因进行直接测序分析。结果该家系患者晶状体混浊表型非常类似,家系分析表明为四代垂直遗传,符合单基因ADCC的特点。基因连锁分析提示,该家系与微卫星D2S325位点和D2S2358位点连锁,最大LOD值分别为1．20（0=0）和0．22（0=0）,位于此区域内的CRYGD基因测序后发现一个已经报道的错义突变c．C70A（p．P23T）。结论CRYGD基因P23T突变是该家系结晶样晶状体混浊的致病原因。     

Clinical and genetic studies of an autosomal dominant cone-rod dystrophy with features of Stargardt disease

Much progress has been made in the past five years in the understanding of Leber congenital amaurosis (LCA) and allied early-onset retinal dystrophies, various forms of stationary sensory retinal blindness, and genes that are involved in the development of the retina. Uncomplicated Leber congenital amaurosis has been associated with mutations of six genes: GUCY2D (encoding RetGC-1) at 17p13.1, RPE65 at 1q31, CRX at 19q13.3, AIPLI at 17p13.1, CRB1 at 1q31-3, and RPGRIP at 14q11. A similar early-onset severe retinal degeneration phenotype has been associated with mutation of TULP1 at 6p21.3. Leber appreciated that the condition he described merged with the phenotypes of early childhood-onset severe retinal degenerations. This insight has been confirmed at the molecular level for mutations of GUCY2D , RPE65 , CRX , AIPL1 , and CRB1 , which cause not only LCA, but also early-childhood and even adult-onset retinal degenerations. This paper reviews the new finding of LCA from mutations of CRB1 and discusses the molecular basis of X-linked blue monochromacy, autosomal recessive congenital achromatopsia from mutations of the genes for ACHM2 ( CNGA3 ) and ACHM3 ( CNGB3 ), X-linked congenital stationary night blindness (CSNB) from mutations of CACNA1F (incomplete CSNB) and NYX (complete CSNB), and the enhanced S-cone syndrome from mutation of the developmental gene, NR2E3 at 15q23, which appears to regulate the development of M- and L-cones from S-cones. These discoveries have opened new areas of cellular and developmental biology for future research into the causes of retinal blindness.     

Spectrum and frequency of mutations in IMPDH1 associated with autosomal dominant retinitis pigmentosa and leber congenital amaurosis

PURPOSE: The purpose of this study was to determine the frequency and spectrum of inosine monophosphate dehydrogenase type I (IMPDH1) mutations associated with autosomal dominant retinitis pigmentosa (RP), to determine whether mutations in IMPDH1 cause other forms of inherited retinal degeneration, and to analyze IMPDH1 mutations for alterations in enzyme activity and nucleic acid binding. METHODS: The coding sequence and flanking intron/exon junctions of IMPDH1 were analyzed in 203 patients with autosomal dominant RP (adRP), 55 patients with autosomal recessive RP (arRP), 7 patients with isolated RP, 17 patients with macular degeneration (MD), and 24 patients with Leber congenital amaurosis (LCA). DNA samples were tested for mutations by sequencing only or by a combination of single-stranded conformational analysis and by sequencing. Production of fluorescent reduced nicotinamide adenine dinucleotide (NADH) was used to measure enzymatic activity of mutant IMPDH1 proteins. The affinity and the specificity of mutant IMPDH1 proteins for single-stranded nucleic acids were determined by filter-binding assays. RESULTS: Five different IMPDH1 variants, Thr116Met, Asp226Asn, Val268Ile, Gly324Asp, and His 372Pro, were identified in eight autosomal dominant RP families. Two additional IMPDH1 variants, Arg105Trp and Asn198Lys, were found in two patients with isolated LCA. None of the novel IMPDH1 mutants identified in this study altered the enzymatic activity of the corresponding proteins. In contrast, the affinity and/or the specificity of single-stranded nucleic acid binding were altered for each IMPDH1 mutant except the Gly324Asp variant. CONCLUSIONS: Mutations in IMPDH1 account for approximately 2% of families with adRP, and de novo IMPDH1 mutations are also rare causes of isolated LCA. This analysis of the novel IMPDH1 mutants substantiates previous reports that IMPDH1 mutations do not alter enzyme activity and demonstrates that these mutants alter the recently identified single-stranded nucleic acid binding property of IMPDH. Studies are needed to further characterize the functional significance of IMPDH1 nucleic acid binding and its potential relationship to retinal degeneration.