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Molecular analysis of the PAX6 gene in Mexican patients with congenital aniridia: report of four novel mutations.

ABSTRACT: Paired box gene 6 (PAX6) heterozygous mutations are well known to cause congenital non-syndromic aniridia. These mutations produce primarily protein truncations and have been identified in approximately 40%-80% of all aniridia cases worldwide. In Mexico, there is only one previous report describing three intragenic deletions in five cases. In this study, we further analyze PAX6 variants in a group of Mexican aniridia patients and describe associated ocular findings.We evaluated 30 nonrelated probands from two referral hospitals. Mutations were detected by single-strand conformation polymorphism (SSCP) and direct sequencing, and novel missense mutations and intronic changes were analyzed by in silico analysis. One intronic variation (IVS2+9G>A), which in silico analysis suggested had no pathological effects, was searched in 103 unaffected controls.Almost all cases exhibited phenotypes that were at the severe end of the aniridia spectrum with associated ocular alterations such as nystagmus, macular hypoplasia, and congenital cataracts. The mutation detection rate was 30%. Eight different mutations were identified: four (c.184_188dupGAGAC, c.361T>C, c.879dupC, and c.277G>A) were novel, and four (c.969C>T, IVS6+1G>C, c.853delC, and IVS7-2A>G) have been previously reported. The substitution at position 969 was observed in two patients. None of the intragenic deletions previously reported in Mexican patients were found. Most of the mutations detected predict either truncation of the PAX6 protein or conservative amino acid changes in the paired domain. We also detected two intronic non-pathogenic variations, IVS9-12C>T and IVS2+9G>A, that had been previously reported. Because the latter variation was considered potentially pathogenic, it was analyzed in 103 healthy Mexican newborns where we found an allelic frequency of 0.1116 for the A allele.This study adds four novel mutations to the worldwide PAX6 mutational spectrum, and reaffirms the finding that c.969C>T is one of the three more frequent causal mutations in aniridia cases. It also provides evidence that IVS2+9G>A is an intronic change without pathogenic effect.

SUBMITTER: Villarroel CE

PROVIDER: S-EPMC2530489 | biostudies-literature | 2008 Sep

REPOSITORIES: biostudies-literature

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Molecular analysis of the PAX6 gene in Mexican patients with congenital aniridia: report of four novel mutations.

Villarroel Camilo E CE Villanueva-Mendoza Cristina C Orozco Lorena L Alcántara-Ortigoza Miguel Angel MA Jiménez Diana F DF Ordaz Juan C JC González-del Angel Ariadna A

Molecular vision 20080908

<h4>Purpose</h4>Paired box gene 6 (PAX6) heterozygous mutations are well known to cause congenital non-syndromic aniridia. These mutations produce primarily protein truncations and have been identified in approximately 40%-80% of all aniridia cases worldwide. In Mexico, there is only one previous report describing three intragenic deletions in five cases. In this study, we further analyze PAX6 variants in a group of Mexican aniridia patients and describe associated ocular findings.<h4>Methods</h ...[more]

PMID: 18776953

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Project description:Aniridia and congenital cataract represent rare but severe developmental ocular conditions. We examined 33 probands from France for mutations in several transcription factors associated with these phenotypes, the forkhead box E3 (FOXE3), paired box gene 6 (PAX6), paired-like homeodomain transcription factor 2 (PITX2), and paired-like homeodomain transcription factor 3 (PITX3) genes.Out of 33 probands, 27 were affected with congenital cataract while the remaining six were affected with aniridia (with or without cataract). The coding regions of FOXE3, PAX6, PITX2, and PITX3 were examined by direct DNA sequencing of gene-specific PCR products.A novel dominant mutation at the stop codon of FOXE3, c.959G>C (p.X320SerextX72), was identified in a patient with congenital cataract. Another novel FOXE3 sequence change, c.571-579dup (p.Tyr191_Pro193dup), was identified in a patient with aniridia, mild lens opacities, and some additional ocular defects; this patient was also found to carry a nonsense mutation in PAX6. PAX6 mutations were identified in two additional probands with aniridia and cataracts. None of the observed sequence alterations were found in normal controls. No mutations were identified in PITX2 or PITX3.The p.X320SerextX72 mutation is only the fourth FOXE3 allele associated with a dominant phenotype since the majority of FOXE3 mutations appear to be recessive with no phenotype observed in heterozygous carriers. The encoded protein is predicted to contain a complete normal sequence followed by seventy-two erroneous amino acids; the position and effect of this mutation are similar to two of the previously reported dominant changes, suggesting a common mechanism for dominant alleles. The p.Tyr191_Pro193dup is predicted to result in an in-frame duplication of three amino acids; however, the contribution of this mutation to the phenotype is unclear since the affected patient also carries a nonsense mutation in PAX6 which acts upstream of FOXE3 in the molecular pathway. The identified PAX6 mutations correspond to the two most commonly observed mutant alleles and demonstrate phenotypes that are consistent with the previously reported spectrum.

Dataset Information

Molecular analysis of the PAX6 gene in Mexican patients with congenital aniridia: report of four novel mutations.

Publications

Molecular analysis of the PAX6 gene in Mexican patients with congenital aniridia: report of four novel mutations.

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