A novel mutation in the CRYAA gene associated with congenital cataract and microphthalmia in a Chinese family.

BACKGROUND: Congenital cataract is the leading cause of blindness in children worldwide. Approximately half of all congenital cataracts have a genetic basis. Protein aggregation is the single most important factor in cataract formation. METHODS: A four-generation Chinese family diagnosed with autosomal dominant congenital cataracts and microphthalmia was recruited at the Shengjing Hospital of China Medical University. Genomic DNA was extracted from the peripheral blood of the participants. All coding exons and flanking regions of seven candidate genes (CRYAA, CRYBA4, CRYBB2, CRYGC, GJA8, MAF, and PITX3) were amplified and sequenced. Restriction fragment length polymorphism (RFLP) assays were performed to confirm the candidate causative variant, c.35G > T in the CRYAA gene. We constructed pcDNA3.1(+)-CRYAA expression plasmids containing either the wild-type or the R12L mutant alleles and respectively transfected them into HEK293T cells and into HeLa cells. Western blotting was performed to determine protein expression levels and protein solubility. Immunofluorescence was performed to determine protein sub-cellular localization. RESULTS: A heterozygous variant c.35G > T was identified in exon 1 of CRYAA, which resulted in a substitution of arginine to leucine at codon 12 (p.R12L). The nucleotide substitution c.35G > T was co-segregated with the disease phenotype in the family. The mutant R12L-CRYAA in HEK293T cells showed a significant increase in the expression level of the CRYAA protein compared with the wild-type cells. Moreover, a large amount of the mutant protein aggregated in the precipitate where the wild-type protein was not detected. Immunofluorescence studies showed that the overexpressed mutant CRYAA in HeLa cells formed large cytoplasmic aggregates and aggresomes. CONCLUSIONS: In summary, we described a case of human congenital cataract and microphthalmia caused by a novel mutation in the CRYAA gene, which substituted an arginine at position 12 in the N-terminal region of αA-crystallin. The molecular mechanisms that underlie the pathogenesis of human congenital cataract may be characterized by the prominent effects of the p.R12L mutation on αA-crystallin aggregation and solubility. Our study also expands the spectrum of known CRYAA mutations.

Novel TMEM98 mutations in pedigrees with autosomal dominant nanophthalmos.

PURPOSE: Autosomal dominant nanophthalmos is an inherited eye disorder characterized by a structurally normal but smaller eye. Patients with nanophthalmos have high hyperopia (far-sightedness), a greater incidence of angle-closure glaucoma, and increased risk of surgical complications. In this study, the clinical features and the genetic basis of nanophthalmos were investigated in two large autosomal dominant nanophthalmos pedigrees. METHODS: Fourteen members of a Caucasian pedigree from the United States and 15 members of a pedigree from the Mariana Islands enrolled in a genetic study of nanophthalmos and contributed DNA samples. Twenty of 29 family members underwent eye examinations that included measurement of axial eye length and/or refractive error. The genetic basis of nanophthalmos in the pedigrees was studied with linkage analysis, whole exome sequencing, and candidate gene (i.e., TMEM98) sequencing to identify the nanophthalmos-causing gene. RESULTS: Nine members of the pedigree from the United States and 11 members of the pedigree from the Mariana Islands were diagnosed with nanophthalmos that is transmitted as an autosomal dominant trait. The patients with nanophthalmos had abnormally short axial eye lengths, which ranged from 15.9 to 18.4 mm. Linkage analysis of the nanophthalmos pedigree from the United States identified nine large regions of the genome (greater than 10 Mbp) that were coinherited with disease in this family. Genes within these "linked regions" were examined for disease-causing mutations using exome sequencing, and a His196Pro mutation was detected in the TMEM98 gene, which was recently reported to be a nanophthalmos gene. Sanger sequencing subsequently showed that all other members of this pedigree with nanophthalmos also carry the His196Pro TMEM98 mutation. Testing the Mariana Islands pedigree for TMEM98 mutations identified a 34 bp heterozygous deletion that spans the 3' end of exon 4 in all affected family members. Neither TMEM98 mutation was detected in public exome sequence databases. CONCLUSIONS: A recent report identified a single TMEM98 missense mutation in a nanophthalmos pedigree. Our discovery of two additional TMEM98 mutations confirms the important role of the gene in the pathogenesis of autosomal dominant nanophthalmos.

Digital evaluation of orbital development in chinese children with congenital microphthalmia.

PURPOSE: To evaluate the asymmetry of bilateral orbital development in Chinese children with congenital microphthalmia and to provide a criterion for tailoring treatment timing and therapy. DESIGN: Retrospective cohort study. METHODS: By combining multisection helical computerized tomography imaging with a computer-aided design system, we measured 38 children between 0 and 6 years of age with congenital microphthalmia and 70 normal children of the same age group. Variables were measured, including orbital volume, depth, width, and height and eyeball volume. Displacement of the orbital rims was calculated by mirroring the unaffected orbit across the midsagittal plane of body. RESULTS: Significant differences were observed between the orbital volume, eyeball volume, orbital width, and orbital height of the affected and unaffected sides of children with congenital microphthalmia (P < .001). The difference between the orbital depth of the affected and unaffected sides was not significant (P = .055). Growth of the inferior and lateral rims retarded by an average of 3 mm, whereas that of the medial and superior rims retarded by less than 1 mm. CONCLUSIONS: The amount of decrease in orbital volume of children with congenital microphthalmia is related to the severity of the disease (decrease in size of the eye), rather than to age. Retarded orbital development is evident primarily in the inferior and lateral rims, correlating mostly with zygomatic and then maxilla and frontal bone. The growth of the affected orbit slows down or even stagnates by 3 years of age. Intervention therapy before 3 years of age was critical.

Nanophthalmos in a Melanesian population.

PURPOSE: To characterize the ophthalmic features and causes of visual loss in a cohort of Melanesians living in New Caledonia with nanophthalmos. METHODS: In this observational study, axial length, visual acuity (VA), cycloplegic autorefraction were assessed and dilated fundus examination was performed. Visual impairment was defined as VA<6/12 in the better eye, hypermetropia as >+1.0 dioptre (D), astigmatism as >or=1.0 D and anisometropia as >or=1.0 D difference between both eyes. Unilateral amblyopia was defined as at least a two-line difference in VA between both eyes and bilateral amblyopia as VA<6/12 in both eyes which was not adequately explained by refractive error and macular folds. RESULTS: Seventeen community-dwelling participants (aged 1.1-45.3 years) with short axial length (range from 16.1 to 21.6 mm) were identified. Of the 17 subjects, 14 were found to have crowded optic discs, three with papillomacular folds, three with a papillomacular band and three with macular radial folds. Further, all subjects demonstrated bilateral hypermetropia (range from +1.3 D to +15.1 D). A high proportion of subjects had astigmatism (12) and anisometropia (nine) in at least one eye. Visual impairment was found in nine subjects: five bilateral and four unilateral. Causes of visual impairment included amblyopia (seven), ametropia (seven) and macular folds (two). Amblyopia was attributed to several factors, including hypermetropia, anisometropia, astigmatism and esotropia. CONCLUSIONS: In this sample of Melanesians with nanophthalmos, a spectrum of ophthalmic features that was consistent with intraocular crowding was found. Over half of the subjects were visually impaired, mostly due to amblyopia and ametropia. Further characterization of the underlying genetic cause of nanophthalmos in this cohort will be the focus of future studies.

A population-based case-control study of isolated anophthalmia and microphthalmia.

The purpose of the study was to reveal the etiological factors in the origin of isolated an/microphthalmia. The dataset of the Hungarian Case-Control Surveillance of Congenital Abnormalities, 1980-2002 containing 56 cases with isolated an/microphthalmia and 22,744 malformed controls with other non-ocular defects from the Hungarian Congenital Abnormality Registry, in addition of 56 matched control pairs and 37,837 population controls without defects from the National Birth Registry, was evaluated. Exposure data and family history were collected (i) prospectively by prenatal logbook and other medical records, (ii) retrospectively through a structured questionnaire filled-in by mothers, and (iii) information obtained by regional nurses at home visit of non-respondent mothers. The autosomal recessive origin of isolated an/microphthalmia was indicated in about 10% of cases on the basis of sib recurrence. Cases with isolated an/microphthalmia had a much shorter mean gestational age and smaller mean birth weight, a much larger proportion of preterm birth and low birthweight. Their mothers were younger with a predominance of first birth order, frequently unmarried with low socioeconomic status. These findings are in agreement with a much higher prevalence at birth of cases with isolated an/microphthalmia in the gypsy population probably due to the interaction of inbreeding effect and low socioeconomic status. Further molecular genetic studies are needed to identify gene mutations of isolated an/microphthalmia in the Hungarian gypsy population.

Micro syndrome in Muslim Pakistan children.

OBJECTIVE: To date, Micro syndrome has been reported in only three children from one family. We describe an additional 14 children from 11 families. DESIGN: Retrospective case series. PARTICIPANTS: Fourteen children from 11 families attending one of five British hospitals. MAIN OUTCOME MEASURES: The following features were documented: pre- and postoperative eye findings, electrophysiologic analysis, systemic abnormalities, development, neuroimaging, genealogy, geographic origin of family. RESULTS: We expand and modify the description of ocular and electrophysiologic findings in Micro syndrome. The eye findings of microphakia, microphthalmos, characteristic lens opacity, and atonic pupils were the presenting feature in all infants and were the most reliable diagnostic signs in the immediate postnatal period. Cortical visual impairment, microcephaly, and developmental delay were not always detectable initially; they developed in all children by 6 months of age. Microgenitalia were a useful diagnostic clue in affected males only. Therefore, eye features were more consistently useful in determining diagnosis than dysmorphology or brain imaging. The families of all the children originate from the Muslim population of Northern Pakistan. Inheritance is likely to be autosomal recessive. CONCLUSIONS: Micro syndrome usually presents to the ophthalmologist, who may be able to make the diagnosis on the basis of characteristic eye findings combined with ethnic origin. Initially, the nature and severity of nonophthalmic features are not apparent. Early diagnosis of the underlying condition is important to guide management of the cataracts, glaucoma, and developmental delay. It is helpful for the family and medical staff to be aware of the low level of vision that develops despite optimal ophthalmic intervention. Genetic counseling extending into the wider family is particularly important in view of the high rate of consanguinity.