11p13 deletions can be more frequent than the PAX6 gene point mutations in Polish patients with aniridia.

Aniridia is a rare, bilateral, congenital ocular disorder causing incomplete formation of the iris, usually characterized by iris aplasia/hypoplasia. It can also appear with other ocular anomalies, such as cataracts, glaucoma, corneal pannus, optic nerve hypoplasia, macular hypoplasia, or ectopia lentis. In the majority of cases, it is caused by mutation in the PAX6 gene, but it can also be caused by microdeletions that involve the 11p13 region. Twelve unrelated patients of Polish origin with a clinical diagnosis of aniridia were screened for the presence of microdeletions in the 11p13 region by means of multiplex ligation probe amplification (MLPA). Additionally, the coding regions of the PAX6 gene were sequenced in all probands. MLPA examination revealed different size deletions of the 11p13 region in five patients. In three cases, deletions encompassed the entire PAX6 gene and a few adjacent genes. In one case, a fragment of the PAX6 gene was deleted only. In the final case, the deletion did not include any PAX6 sequence. Our molecular findings provide further evidence of the existence of the distant 3' regulatory elements in the downstream region of the PAX6 gene, which is known from other studies to influence the level of protein expression. Sequence analysis of the PAX6 gene revealed the three different point mutations in the remaining four patients with aniridia. All the detected mutations were reported earlier. Based on accomplished results, the great diversity of the molecular basis of aniridia was found. It varies from point mutations to different size deletions in the 11p13 region which encompass partly or completely the PAX6 gene or cause a position effect.

A 556 kb deletion in the downstream region of the PAX6 gene causes familial aniridia and other eye anomalies in a Chinese family.

PURPOSE: The paired box gene 6 (PAX6) on human chromosome 11p13 is an essential transcription factor for eye formation in animals. Mutations in PAX6 can lead to varieties of autosomal-dominant ocular malformations with aniridia as the major clinical signs. Known genetic alterations causing haplo-insufficiency of PAX6 include nonsense mutations, frame-shift mutations, splicing errors, or genomic deletions. The purpose of this study was to identify genetic defects as the underlying cause of familial aniridia in a large Chinese family. METHODS: All exons of PAX6 in the proband were sequenced by the Sanger sequencing technique. The genome of the proband was evaluated by a microarray-based comparative genomic hybridization (aCGH). Quantitative real-time PCR was applied to verify the abnormal aCGH findings in the proband and to test five other family members. RESULTS: There were no detectable pathogenic mutations in the exons of PAX6 in the proband. The aCGH analysis showed two copies of PAX6 but revealed a 566 kb hemizygous deletion of chromosome 11p13, including four annotated genes doublecortin domain containing 1 (DCDC1), DnaJ homolog subfamily C member 24 (DNAJC24), IMP1 inner mitochondrial membrane(IMMP1L), andelongation factor protein 4 (ELP4) downstream of PAX6. Quantitative real-time PCR verified the deletion in the proband and further identified the deletion in a blind fashion in four affected family members but not in the one with a normal phenotype. CONCLUSIONS: The 566 kb hemizygous deletion of chromosome 11p13 downstream of PAX6 should be the cause of the familial aniridia in this Chinese family, although two copies of PAX6 are intact. aCGH evaluation should be applied if there is a negative result for the mutation detection of PAX6 in patients with aniridia.

Genotype/phenotype association in Indian congenital aniridia.

The developmental birth eye disorder of iris is known as aniridia. Heterozygous PAX6 gene, which causes human aniridia and small eye in mice, is located on chromosome 11p13. The variability had been documented between the affected individuals within the families, is due to genotypic variation. Haploinsufficiency renders PAX6 allele non-functional or amorphic, however it presents hypomorphic or neomorphic alleles. India is not a well-studied ethnic group, hence the focus on congenital aniridia gene analysis supports the literature and the phenotypic association were analysed both in sporadic as well as familial. The consistent association of truncating PAX6 mutations with the phenotype is owing to non-sense-mediated decay (NMD). It is presumed that the genetic impact of increased homozygosity and heterozygocity in Indian counter part arises as the consequence of consanguineous marriages. The real fact involved in congenital aniridia with other related phenotypes with PAX6 mutations are still controversial.

A novel PAX6 gene mutation in an Indian aniridia patient.

PURPOSE: A mutation in the PAX6 gene is thought to be the genetic cause of aniridia. Here we search for PAX6 gene mutations in Indian aniridia patients. METHODS: We amplified the coding exons of the PAX6 gene from the genomic DNA of 15 unrelated aniridia patients using polymerase chain reaction technology. We then performed single-strand conformation polymorphism analysis and heteroduplex analysis to search for sequence variants. RESULTS: Sequencing of shifted bands in two patients revealed PAX6 gene mutations. One of these was a novel mutation, 1180insA, located in exon 10 at the start of the PST domain. The other mutation, 1080C->T (R240X), located in exon 9 within the homeodomain, and is another example of the most commonly reported PAX6 mutation. CONCLUSIONS: Although PAX6 gene mutations and polymorphisms have been reported from various ethnic groups, we report for the first time the identification of PAX6 gene mutations in Indian aniridia patients.