Novel cytochrome P4501B1 (CYP1B1) gene mutations in Japanese patients with primary congenital glaucoma

PURPOSE: To investigate CYP1B1 gene mutations in Japanese patients with primary congenital glaucoma (PCG). METHODS: Sixty-five unrelated Japanese patients with PCG were screened by PCR-single-strand conformational polymorphism (SSCP) analysis followed by direct sequencing. No patients were offspring of consanguineous marriages, a common occurrence among patients in previous reports. PCG haplotypes were constructed with intragenic polymorphisms in affected individuals. Three-dimensional atomic structures of human CYP1B1 and four mutant CYP1B1 sequences representing missense mutations were assembled using homology modeling and were regularized by an energy-minimization procedure. RESULTS: Eleven novel mutations, including seven definite and four probable mutations, were detected in 13 (20%) of the 65 unrelated patients. Of the seven definite mutations, three were predicted to truncate the CYP1B1 open reading frame. The other four were missense mutations (Asp192Val, Ala330Phe, Val364Met, and Arg444Gln), all located in conserved core structures determining proper folding and heme-binding ability of cytochrome P450 molecules. Molecular modeling demonstrated that two of four mutations in positions 330 and 364 were structurally neutral, but Arg444Gln caused significant structural change. Of the four probable mutations, three were missense (Val198Ile, Val320Leu, and Glu499Gly); the other was a base substitution in the noncoding region of exon 1. CONCLUSIONS: The 11 varied CYP1B1 mutations found in 13 unrelated Japanese patients with sporadic occurrence of PCG represent an allelic heterogeneity and may be unique to a specific population.     

Phenotype of cytochrome P4501B1 gene (CYP1B1) mutations in Japanese patients with primary congenital glaucoma

AIM: To investigate the phenotypes associated with cytochrome P4501B1 gene (CYP1B1) mutations in Japanese patients with primary congenital glaucoma (PCG). METHODS: 66 Japanese patients with PCG were screened for sequence mutations in the CYP1B1 gene using single strand conformation polymorphism analysis followed by automated DNA sequencing. 11 cases had a CYP1B1 mutation in both alleles (the mutation group) and 21 cases did not have a CYP1B1 mutation (the "no mutation" group). The clinical features, such as age of onset, sex, intraocular pressure, and Descemet's membrane rupture, of the two groups were compared. RESULTS: The clinical symptoms and signs did not differ for the two groups. The mean age at onset was 1.7 months in the mutation group and 3.1 months in the no mutation group, and the male:female ratio was 6:5 in the mutation group and 19:2 in the no mutation group. Both of these differences were statistically significant. CONCLUSIONS: In clinically diagnosed cases of PCG, a subgroup shows a CYP1B1 gene mutation. Age at onset was earlier in PCG patients with CYP1B1 mutations than in patients without mutations. Women were more prevalent among patients with mutations than those without mutations.     

Cytochrome P450 1B1 gene mutations in Japanese patients with primary congenital glaucoma(1)

PURPOSE: To report a novel missense mutation and DNA polymorphism of the CYP1B1gene in Japanese patients with primary congenital glaucoma. METHODS: A series of 11 unrelated patients with primary congenital glaucoma was examined. Patients were followed in the Kagoshima University Hospital between 1979 and 1998. DNA was extracted from leukocytes of the patients, their families, and unrelated healthy individuals. Amplicons spanning the coding regions of the CYP1B1 gene were examined by direct sequencing and enzyme-restriction detection. RESULTS: In the 11 unrelated patients, besides the previously reported insertional mutation (1620 ins G), a novel missense mutation was identified at codons 444 to replace arginine with glutamine (R444Q) in one patient. The novel missense mutation cosegregated in the relevant family as an autosomal recessive pattern and was not found in other patients or control individuals. In addition, five polymorphic sites were found at codons 48, 119, 330, 432, and 449. These polymorphic alleles did not cosegregate with the disease, and they were found in healthy individuals as well. CONCLUSIONS: Approximately 20% of Japanese patients with primary congenital glaucoma may be affected by mutations in the CYP1B1 gene. Further studies are justified to explore whether a relationship exists between the phenotypic expressivity of the disease and the type of mutation.     

A novel truncating mutation of cytochrome P4501B1 (CYP1B1) gene in primary infantile glaucoma.

PURPOSE: To report a novel mutation of the CYP1B1 gene in a Japanese patient with primary infantile glaucoma. METHODS: DNA was extracted from leukocytes of six unrelated patients with primary infantile glaucoma. The coding regions of the CYP1B1 gene were amplified by polymerase chain reaction, examined by agarose gel separation and heteroduplex methods, and directly sequenced. RESULTS: One of the patients with primary infantile glaucoma had a mutation of the CYP1B1 gene, with an abnormal shift in agarose gel separation and heteroduplex analysis. Direct sequencing disclosed a homozygous insertion of guanine at nucleotide 1620 of exon 3, which produced a frameshift leading to premature termination of amino acid translation. The patient was male and had sporadic, classic primary infantile glaucoma. None of the other five patients with infantile glaucoma, the 30 patients with primary adult-onset glaucoma, or the 70 healthy control subjects showed any abnormalities in the CYP1B1 gene. CONCLUSIONS: This is the first report of CYP1B1 gene mutation in primary infantile glaucoma from the Eastern world. CYP1B1 gene mutation for primary infantile glaucoma spreads worldwide, but its prevalence may have ethnic or geographic differences.     

Compound heterozygous mutations in CYP1B1 gene leads to severe primary congenital glaucoma phenotype

AIM: To identify the novel mutation alleles in the CYP1B1 gene of primary congenital glaucoma (PCG) patients at Shandong Province of China, and investigate their correlation with glaucomatous features. METHODS: The DNA from the peripheral blood of 13 congenital glaucoma patients and 50 ethnically matched healthy controls from the affiliated hospital of Qingdao University were extracted. The coding region of the CYP1B1 gene was amplified by PCR and direct DNA sequencing was performed. Disease causing-variants were analyzed by comparing the sequences and the structures of wild type and mutant CYP1B1 proteins by PyMOL software. RESULTS: Two missense mutations, including A330F caused by c.988G>T&c.989C>T, and R390H caused by c.1169G>A, were identified in one of the 13 PCG patients analyzed in our study. A330F mutation was observed to be novel in the Chinese Han population, which dramatically altered the protein structure of CYP1B1 gene, including the changes in the ligand-binding pocket. Furthermore, R390H mutation caused the changes in heme-protein binding site of this gene. In addition, the clinical phenotype displayed by PCG patient with these mutations was more pronounced than other PCG patients without these mutations. Multiple surgeries and combined drug treatment were not effective in reducing the elevated intraocular pressure in this patient. CONCLUSION: A novel A330F mutation is identified in the CYP1B1 gene of Chinese PCG patient. Moreover, in combination with other mutation R390H, this PCG patient shows significant difference in the CYP1B1 protein structure, which may specifically contribute to severe glaucomatous phenotype.     

Cytochrome P4501B1 mutations cause only part of primary congenital glaucoma in Ecuador

Purpose: To determine the role of cytochrome P4501B1 ( CYP1B1 ) mutations in causing primary congenital glaucoma (PCG) in a cohort of Native Americans from Quito, Ecuador. Materials and methods: Seventeen patients with PCG from 15 Native American families were recruited from the Ophthalmology Clinic at Hospital Metropolitano, Quito, Ecuador. Experienced ophthalmologists examined all affected study subjects. Purified DNA was prepared from peripheral blood samples and CYP1B1 coding exons (exons 2 and 3) were amplified and sequenced. Southern blot was performed only on those affected patients who showed no mutations in the CYP1B1 coding exons. Results: The molecular basis of PCG in two families was determined: two novel mutations (a deletion and a point mutation) and one novel polymorphism in CYP1B1 were identified in addition to a previously described single amino acid substitution. Southern blot analyses on whole genomic DNA from affected individuals in whom no mutations were identified by the direct PCR/sequencing approach did not detect any large rearrangements or mutations outside the coding region. Conclusion: These findings suggest that mutations in CYP1B1 are not a major cause of PCG in this population and that at least one additional locus for this condition is responsible for most cases. Further, the PCG phenotype did not correlate readily with the molecular basis of the disorder, suggesting that careful clinical analysis of the phenotype cannot predict the molecular basis of the disease with accuracy.     

Novel compound heterozygous mutations in the MFRP gene in a Japanese patient with posterior microphthalmos

Purpose  

To report a case of posterior microphthalmos caused by novel compound heterozygous mutations in the membrane-type frizzled-related protein (MFRP) gene.     

Cytochrome P4501B1 mutations cause only part of primary congenital glaucoma in Ecuador

PURPOSE: To determine the role of cytochrome P450IBI (CYP1B1) mutations in causing primary congenital glaucoma (PCG) in a cohort of Native Americans from Quito, Ecuador. MATERIALS AND METHODS: Seventeen patients with PCG from 15 Native American families were recruited from the Ophthalmology Clinic at Hospital Metropolitano, Quito, Ecuador. Experienced ophthalmologists examined all affected study subjects. Purified DNA was prepared from peripheral blood samples and CYP1B1 coding exons (exons 2 and 3) were amplified and sequenced. Southern blot was performed only on those affected patients who showed no mutations in the CYP1B1 coding exons. RESULTS: The molecular basis of PCG in two families was determined: two novel mutations (a deletion and a point mutation) and one novel polymorphism in CYP1B1 were identified in addition to a previously described single amino acid substitution. Southern blot analyses on whole genomic DNA from affected individuals in whom no mutations were identified by the direct PCR/sequencing approach did not detect any large rearrangements or mutations outside the coding region. CONCLUSION: These findings suggest that mutations in CYPIBI are not a major cause of PCG in this population and that at least one additional locus for this condition is responsible for most cases. Further, the PCG phenotype did not correlate readily with the molecular basis of the disorder, suggesting that careful clinical analysis of the phenotype cannot predict the molecular basis of the disease with accuracy.     

Overview of Cytochrome P450 1B1 gene mutations in patients with primary congenital glaucoma

The objective of this study was to investigate the distribution of mutations in the Cytochrome P450 1B1 gene (CYP1B1) in patients with primary congenital glaucoma (PCG) among different populations. All identifiable original studies on CYP1B1 gene mutations of patients with PCG were reviewed. Finally, DNA mutations within the CYP1B1 gene were identified in 542 patients with PCG according to 52 scientific articles and 147 distinct mutations were found. The 3987G>A (G61E) missense mutation is a founder mutation in Middle Eastern population, responsible for 45.52% of CYP1B1 mutations. In Gypsies, missense mutation 7996G>A (E387K) seems to be a founder mutation, accounting for 79.63% of CYP1B1 mutations. It seems that there is no founder mutation in Asian or Caucasian population, but also accumulates in some spots. Mutations 7927G>A (V364M), 7990C>T (L385F) and 8006G>A (R390H) are common in Asian population. In Caucasians, 7940G>A (R368H), 8037dup10, 8006G>A (R390H), 7901del13, 4340delG, 3987G>A (G61E), 7996G>A (E387K), 4490G>A (E229K) and 8005C>T/A (R390C/S) are common mutations. The findings suggest that ethnic differences and the geographical distribution of PCG may be associated with different CYP1B1 mutation patterns. Such information may be useful in developing strategies for reliable clinical genetic testing of patients with PCG and their families.     

原发性先天性青光眼CYP1B1基因变异初步研究

目的了解CYP1B1基因变异在中国原发性先天性青光眼(PCG)患者发病中的作用。方法收集来自不同地区的16例PCG患者,对其CYP1B1基因编码外显子进行直接测序,对照组进行单核苷酸多态性分析。结果在1例PCG患者中发现了一种变异,为8006G>A(R390H)。它是位于外显子III的错义突变。还发现了五种单核苷酸多态性,分别为3793T>G,R48G,A119S,A330S,V432L。结论CYP1B1基因是导致中国人PCG患者的致病基因,但也有其他变异可能和PCG变异有关。     

原发性先天性青光眼CYP1B1基因新变异

目的 探讨CYP1B1基因变异在湖南地区原发性先天性青光眼患者中的分布.方法 病例对照研究.收集来自湖南地区的13例原发性先天性青光眼患者的临床资料进行分析,对13例患者的CYP1B1基因编码外显子进行直接测序和聚合酶链反应-限制性内切酶技术检测.结果 13例原发性先天性青光眼患者中,有1例发现一种基因新突变(c.C319G,L107V),是位于外显子2的错义突变.100例正常人中未见L107V突变.同时发现已报道的4种单核苷酸多态位点,分别为R48G、A119S、V432L、D449D.结论 CYP1B1基因L107V突变可能是导致湖南地区原发性先天性青光眼患者的致病原因之一.     

Molecular analysis of the CYP1B1 gene: identification of novel truncating mutations in patients with primary congenital glaucoma

BACKGROUND: Mutations and polymorphisms have been identified in the CYP1B1 gene; while mutations that affect the conserved core structures of cytochrome P4501B1 result in primary congenital glaucoma (PCG), mutations in other regions hold the potential to define differences in estrogen metabolism. In the present study, we analyzed the CYP1B1 gene in Mexican patients with PCG and described four novel mutations. MATERIALS AND METHODS: The sample included 12 nonrelated cases with PCG. Analysis of coding regions of the CYP1B1 gene was performed through PCR and DNA sequencing analysis from genomic DNA. RESULTS AND DISCUSSION: Molecular analysis of the CYP1B1 gene showed the following molecular defects: (1) a novel single-base pair deletion within codon 370 (1454delC) that produces a substitution of leucine instead of proline and a premature stop codon 57 amino acids after the last original amino acid; this family also harbored a novel polymorphic variant of the cytochrome P4501B1 with six single-nucleotide polymorphisms (142C-->G; 355G-->T; 729G-->C; 4326C-->G; 4360C-->G and 4379C-->T); (2) a novel single-base pair deletion within codon 277 (1176delT) that results in a premature stop codon; (3) a novel single-base pair deletion within codon 179 (880delG) that produces a substitution of arginine instead of alanine and a premature stop codon 17 amino acids downstream from the last original amino acid, and (4) a duplication (or insertion) of ten base pairs within codon 404 (1556dupATGCCACCAC) that results in a premature stop codon 26 amino acids after the last original amino acid. We also observed in 2 nonrelated patients a deletion of 13 bp (1410_1422delGAGTGCAGGCAGA) previously reported for other populations. CONCLUSION: We reported four novel mutations and a novel polymorphic variant in the CYP1B1 gene in PCG in the Mexican population; it has important implications in diagnosis and genetic counseling.     

Novel CYP1B1 mutations and a possible prognostic use for surgical management of congenital glaucoma

AIM: To identify CYP1B1 gene mutations and evaluate their possible role as a prognostic factor for success rates in the surgical management of Egyptian congenital glaucoma patients. METHODS: Totally 42 eyes of 29 primary congenital glaucoma patients were operated on with combined trabeculotomy/trabeculectomy with mitomycin-C and followed up at 1d, 1wk, 1, 6 and 12mo postoperatively. Genomic DNA was extracted from peripheral blood leukocytes. Coding regions of CYP1B1 gene were amplified using 13 pairs of primers, screened for mutations using single-strand conformation polymorphism followed by sequencing of both strands. Efficacy of the operation was graded as either a success [maintaining intraocular pressure (IOP) less than 21 mm Hg with or without anti-glaucoma medication], or a failure (IOP more than 21 mm Hg with topical antiglaucoma medications). RESULTS: Seven novel mutations out of a total of 15 different mutations were found in the CYP1B1 genes of 14 patients (48.2%). The presence of CYP1B1 gene mutations did not correlate with the failure of the surgery (P=0.156, odds ratio=3.611, 95%CI, 0.56 to 22.89); while the positive consanguinity strongly correlated with failure of the initial procedure (P=0.016, odds ratio=11.25, 95%CI, 1.57 to 80.30). However, the Kaplan-Meier survival analysis revealed a significantly lower time of IOP control in the subgroup with mutations in CYP1B1 versus the congenital primary glaucoma group without mutations (log rank test, P=0.015). CONCLUSION: Seven new CYP1B1 mutations are identified in Egyptian patients. Patients harboring confirmed mutations suffered from early failure of the initial surgery. CYP1B1 mutations could be considered as a prognostic factor for surgery in primary congenital glaucoma.     

Compound heterozygous CNGA3 mutations (R436W, L633P) in a Japanese patient with congenital achromatopsia

Congenital achromatopsia is a stationary retinal disorder with autosomal recessive inheritance that is characterized by loss of color discrimination, low visual acuity, photophobia, and nystagmus. This disorder has been shown to be associated with CNGA3, CNGB3, and GNAT2 mutations, and the frequency of mutations in the CNGA3 gene (encoding alpha subunit of the cone-specific cGMP-gated cation channel) was 23-33% in European populations. The aim of this study was to test the hypothesis that CNGA3 mutations are also responsible for congenital achromatopsia in Japanese patients. DNA from venous blood samples from a total of 14 patients from 13 Japanese pedigrees was prepared. Mutation screening of the CNGA3 gene was performed using direct sequencing and PCR-single-strand conformation polymorphism analysis. Compound heterozygous missense mutations (p.R436W and p.L633P, the latter of which was novel) were identified in one patient only, a 22-year-old female. Neither of these two mutations was found in 150 Japanese control individuals. The patient's parents and sister carried one of these mutations each but were not affected. No mutations in the CNGB3 or GNAT2 genes were identified in the patient. Clinically, best-corrected visual acuity was 0.1 in both eyes. No specific findings were obtained in funduscopy. Optical coherence topography revealed a normal foveal thickness but a 20% decrease in parafoveal thickness. Ganzfeld full-field electroretinograms (ERGs) showed normal responses in rod and mixed rod-plus-cone ERGs but no response in cone or 30-Hz flicker ERGs. Spectral sensitivity on a white background revealed a curve with only one peak at around 500 nm, which fits the absorption spectrum of human rhodopsin. L633, conserved among vertebrate orthologs of human CNGA3, is a hydrophobic residue forming part of the carboxy-terminal leucine zipper (CLZ) domain, which is functionally important in the mediation of intracellular interactions. To our knowledge, this is the first report of a Japanese complete achromat with CNGA3 mutations, and of any patient with a missense mutation within the CLZ domain. The outcome suggests low frequency (7%, 1/14) of CNGA3 mutations in Japanese patients.     

Primary congenital glaucoma: three case reports on novel mutations and combinations of mutations in the GLC3A (CYP1B1) gene

PURPOSE: To describe three patients with congenital glaucoma homozygous and compound heterozygous for different mutations and benign sequence variants in the cytochrome P 450 1B1 (CYP1B1) gene. METHODS: All patients were examined by slit-lamp biomicroscopy, gonioscopy, measurement of the cornea and optic disc, ultrasound biometry, and automated static threshold perimetry when possible. Direct sequence analysis was performed on DNA extracted from peripheral blood from the patients and their parents. RESULTS: For patient 1, a newborn boy with buphthalmos and an opaque cornea, a novel homozygous C/T transition in codon 355 (CGA>TGA) led to a predicted nonsense codon Arg355X truncating the protein by 188 amino acids. For patient 2, a 24-year-old man, a compound heterozygous mutation 1410-1422del/1546-1555dup was found. For patient 3, a 34-year-old man, two novel heterozygous missense mutations resulting in an Ala443Gly and a Glu229Lys amino acid exchange and five benign sequence variants were found. CONCLUSION: Our results confirm the crucial role of CYP1B1 mutations for congenital glaucoma.