GUCY2D mutations in a Chinese cohort with autosomal dominant cone or cone-rod dystrophies.

BACKGROUND: To report the results of the GUCY2D gene mutation analysis in a cohort of Chinese patients with cone or cone-rod dystrophies (COD or CORD) and to describe the clinical features observed in patients with molecularly confirmed COD or CORD. METHODS: A total of 74 probands clinically diagnosed with COD or CORD were recruited for genetic analysis; these included 15 unrelated patients with a positive family history consistent with an autosomal dominant pattern of inheritance and 59 unrelated sporadic cases. All probands underwent ophthalmic examinations including best-corrected visual acuity, fundus examination, optical coherence tomography, and electroretinography. Genomic DNA was extracted from venous blood of all participants, and all coding exons and exon-intron boundaries of the GUCY2D gene were screened for mutations by PCR-based DNA sequencing. Restriction fragment length polymorphism analysis and allele-specific PCR analysis were used to validate the substitution in all available family members. RESULTS: Four different GUCY2D missense mutations--three affected codon 838 and one affected codon 849--were identified in nine unrelated probands. Mutation p.R838H was identified in four probands, while both mutations p.R838C and p.R838P were found in two unrelated patients, and mutation p.T849A was found in one proband. The GUCY2D mutations were found in 47% of the patients (7/15) with autosomal dominant cone dystrophy. Patients with mutation p.R838P presented a relatively severe clinical phenotype. CONCLUSION: The GUCY2D mutations were frequent in Chinese families with autosomal dominant cone or cone-rod dystrophies. All mutations were found in exon 13, which should be given priority during mutation screening analysis.

Two novel PRP31 premessenger ribonucleic acid processing factor 31 homolog mutations including a complex insertion-deletion identified in Chinese families with retinitis pigmentosa.

OBJECTIVE: To identify the causative mutations in two Chinese families with retinitis pigmentosa (RP), and to describe the associated phenotype. METHODS: Individuals from two unrelated families underwent full ophthalmic examinations. After informed consent was obtained, genomic DNA was extracted from the venous blood of all participants. Linkage analysis was performed on the known genetic loci for autosomal dominant retinitis pigmentosa with a panel of polymorphic markers in the two families, and then all coding exons of the PRP31 premessenger ribonucleic acid processing factor 31 homolog (PRPF31) gene were screened for mutations with direct sequencing of PCR-amplified DNA fragments. Allele-specific PCR was used to validate a substitution in all available family members and 100 normal controls. A large deletion was detected with real-time quantitative PCR (RQ-PCR) using a panel of primers from regions around the PRPF31 gene. Long-range PCR, followed by DNA sequencing, was used to define the breakpoints. RESULTS: Clinical examination and pedigree analysis revealed two four-generation families (RP24 and RP106) with autosomal dominant retinitis pigmentosa. A significant two-point linkage odd disequilibrium score was generated at marker D19S926 (Zmax=3.55, θ=0) for family RP24 and D19S571 (Zmax=3.21, θ=0) for family RP106, and further linkage and haplotype studies confined the disease locus to chromosome 19q13.42 where the PRPF31 gene is located. Mutation screening of the PRPF31 gene revealed a novel deletion c.1215delG (p.G405fs+7X) in family RP106. The deletion cosegregated with the family's disease phenotype, but was not found in 100 normal controls. No disease-causing mutation was detected in family RP24 with PCR-based sequencing analysis. RQ-PCR and long-range PCR analysis revealed a complex insertion-deletion (indel) in the patients of family RP24. The deletion is more than 19 kb and encompasses part of the PRPF31 gene (exons 1-3), together with three adjacent genes. CONCLUSIONS: Our results further confirmed that haploinsufficiency is the main mechanism for RP11 and that genomic arrangements may be prevalent in PRPF31 mutations.

Identification of two mutations of the RHO gene in two Chinese families with retinitis pigmentosa: correlation between genotype and phenotype.

PURPOSE: To describe the clinical and genetic findings in two Chinese families with retinitis pigmentosa (RP). METHODS: Two unrelated families were examined clinically. After informed consent was obtained, genomic DNA was extracted from the venous blood of all participants. Genotyping and haplotyping analysis was performed on the known genetic loci for autosomal dominant retinitis pigmentosa (adRP) with a panel of polymorphic markers in the two families, and then mutation screening of all coding exons of the RHO gene was performed by direct sequencing of PCR-amplified DNA fragments. Whenever substitutions were identified in a patient, restriction fragment length polymorphism analysis was performed on all available family members and on 100 normal controls. RESULTS: Clinical examination and pedigree analysis revealed two four-generation families (83 and 112) with adRP. A significant two-point linkage odd disequilibrium (LOD) score was generated at marker D3S1292 (Zmax=1.90, θ=0) for family 83 and (Zmax=2.77, θ=0) for family 112, respectively, and further linkage and haplotype studies confined the disease locus to 3q21-22 where the RHO gene is located. Mutation screening of the RHO gene in the two families revealed a G→C transversion at position 505 (p.A169P) of the cDNA sequence in family 83 and a C→A transversion at position 1040 (p.P347Q) of the cDNA in family 112. The novel p.A169P and recurrent p.P347Q mutations cosegregated with the phenotypes of the two families. Secondary structure prediction suggested that the mutant rhodopsin 169P led to significant secondary structure changes between residues 165 and 169, which may interfere with the correct folding of the transmembrane domain. CONCLUSIONS: Two mutations of the RHO gene were identified in two Chinese families with adRP. Our findings further suggest codon 347 is the mutation hotspot of the RHO.

Large novel deletions detected in Chinese families with aniridia: correlation between genotype and phenotype.

PURPOSE: To describe the clinical and genetic findings in two Chinese families with aniridia and other ocular abnormalities. METHODS: Two unrelated families were examined clinically. After informed consent was obtained, genomic DNA was extracted from the venous blood of all participants. Mutation screening of all exons of the PAX6 (paired box gene 6) gene was performed by direct sequencing of PCR-amplified DNA fragments. Multiplex ligation-dependent probe amplification (MLPA) was performed to detect large deletions. Linkage analysis was used to validate the large deletions revealed by MLPA in all available family members. RESULTS: Clinical examination and pedigree analysis revealed one four-generation family (85) and one three- generation family (86) with total aniridia, congenital cataracts, foveal hypoplasia, and glaucoma. No mutation in PAX6 was identified after PCR-sequencing. Through MLPA analysis, a large deletion including the whole PAX6 gene, DKFZp686k1684 (hypothetical LOC440034), and the RCN1 (reticulocalbin 1) gene was detected in family 85; a 3' deletion to the PAX6 gene including the ELP4 (elongator complex protein 4) and the DCDC1 (doublecortin domain containing 1) gene was identified in family 86.The two large deletions were confirmed with linkage analysis and the "loss of heterozygous" in the different PAX6 regions were co-segregated with the phenotype of the two families, respectively. CONCLUSIONS: Patients with the PAX6 contiguous gene deletion, including the RCN1 gene, presented more severe vision impairments than those carrying the PAX6 3' deletion. Large deletions may account for several Chinese families and sporadic cases with aniridia and screening for these kinds of alterations should be included in aniridia patients' analyses.

[Theoretic explanation about visual disorder induced by fibrous dysplasia of skull: pressure disequilibrium between lamina cribrosa].

OBJECTIVE: To investigate the causes for changes in optic nerve head and visual impairment caused by fibrous dysplasia (FD) of optic canal stenosis. METHODS: A total of 12 FD patients, diagnosed by CT, received the fundus and optical coherence tomography (OCT). Those with FD involving optic canal underwent decompression. The examination of OCT showed that lamina cribrosa located at the top was the exposure factor for retinal pigment epithelium (RPE). There were decreased vision or edematous optic nerve and atrophic lesion. Odds ratio was calculated by Fisher's exact test. RESULTS: The examination of CT showed the results of optic canal stenosis caused by lesions involving 18 sides: 8-sides with normal vision. Among which, 6 showing that lamina cribrosa was located below RPE and a lamina cribrosa plate near RPE at follow-up, 1 side OCT showing lamina cribrosa above RPE with normal optic nerve; a lateral lamina cribrosa was located above RPE with edematous optic nerve. Visual impairment at 10 sides, normal papillary 2 sides, atrophic papillary 8 sides, OCT showed that lamina cribrosa was located above RPE, postoperatively OCT showed that lamina cribrosa below with 7 sides having improved visual acuity. Fisher's exact test was performed (P = 0.000, odds ratio = infinity). CONCLUSION: The optic canal stenosis causes a rising pressure of lamina cribrosa zone to shift above RPE. The channel becomes distorted so as to squeeze and cut the ganglion cell axons of optic nerve, block the axoplasmic transport and result in blood circulation disorder. The above factors are the etiologies of visual impairments. Postoperatively lamina cribrosa zone pressure drops so that depressed lamina cribrosa and channel deformation recover and visual acuity improves.

[Single channel multifocal VEP studies in normal Chinese].

OBJECTIVE: To investigate the waveform characters of single channel mVEP and its variability in normal Chinese people. METHODS: VERIS Science 4.3 system was used to record and analyze single channel mVEP. The stimulation was performed with a 60 pattern segment dartboard configuration. The Michelson contrast was 99% and the repetition rate 75 Hz. Recording electrodes were placed 3 cm above and 3 cm below the inion. The m-14 sequence required 4 minutes of recording time per eye, which was divided into 8 short segments. The signal was amplified 100 000 times and band-pass filtered between 3 and 100 Hz. The first slices of second kernel at 60 locations were analyzed. The main wave peak-to-trough amplitude and latency from 30 to 130 ms signal window were measured and calculated with the costumed Matlab program. The study included 64 normal subjects (39 women and 25 men). The age range was 13 - 66 years. 7 subjects were tested 2 - 7 times on different occasions for reproducibility. The statistic analysis was performed with Excel and SPSS. RESULTS: In mVEP trace array, the polarity of upper hemifield traces was usually opposite to lower hemifield traces. However, at near vertical meridian areas and near below horizontal meridian areas, the trace polarity had some variability. The main wave mean amplitudes of 60 location responses in left eye were from 0.177 microV to 0.401 microV. The amplitude CVs for 60 locations were from 36.6% to 60.7%. The mean latencies of 60 location responses were from 100 to 116 ms, and latency CVs were from 8.8% to 18.1%. The smaller signals located in zones of upper periphery, along vertical meridian, below horizontal meridian and the larger signals located in near horizontal meridian areas and near non-axial meridian areas which distribution is like a bow tie. There was smaller amplitude variability in the some upper hemifiled locations with smaller amplitude, and there was larger amplitude variability in the some lower hemifiled locations with larger amplitude. The mean amplitudes of all 60 locations in male subjects were lower than that in female subjects, in which 30 locations were low significantly (P < 0.05). The gender influence on latency was less, in which only at 10 locations the difference was significant (P < 0.05). At 20 locations of all, which were mainly distributed at near vertical meridian of lower hemifiled, there was a significant positive correlation of age with amplitude. The age influence on latency was also less. CONCLUSIONS: The larger variability of main wave peak-to-trough amplitude in single channel mVEP existed in different subjects and different locations of same subject. In analysis of mVEP amplitude, the influence of VEP curve location, gender and age should be considered. The main wave latencies of intersubject and intrasubject have smaller variability, and less effect by gender and age, so latency may be a useful diagnostic parameter.