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Aniridia
Anophthalmia
Microphthalmia
Developmental Eye Disease
PAX6
SOX2
SIX6
Mutation analysis for three genes involved in development eye disease is offered.
PAX6
It has been estimated that over 80% of patients with aniridia, without deletion of the PAX6 gene, have a heterozygous mutation identifiable by DNA sequence analysis as performed by GeneDx, Inc. Most of the identified mutations are loss-of-function mutations, including nonsense and frameshift mutations. Individuals with other developmental eye abnormalities may also have mutation in the PAX6 gene and homozygous PAX6 mutation has been associated with anophthalmia.
SIX6 and SOX2
The etiology of anophthalmia and microphthalmia is heterogeneous and includes chromosomal abnormalities, prenatal exposures, and single gene disorders. Syndromic anophthalmia is associated with mutation in the SOX2 gene (and sometimes homozygous PAX6 gene mutation, see above). In one study, eleven percent of individuals with sporadic bilateral anophthalmia were found to have truncating mutation in the SOX2. Other associated findings were male genitourinary abnormalities, myopathy, and spastic diplegia. Heterozygous mutations in SIX6 have been associated with anophthalmia and pituitary hypoplasia, while heterozygous deletion of SIX6 has been seen in some cases of bilateral anophthalmia. However, the overall incidence of SIX6 mutations in developmental eye disorders appears to be low.
We offer mutation analysis of the PAX6, SIX6 and SOX2 genes as separate tests. Using genomic DNA obtained from buccal (cheek) swabs or blood (1-5 ml in EDTA), each test consists of bi-directional sequence analysis of the coding region. This analysis is expected to identify most types of mutations, if they exist, with the exception of gross deletions. In circumstances when such a gene deletion is suspected, CopyDx gene copy number analysis is available to detect a whole or partial SIX6 or SOX2 gene deletions and Multiplex Ligation-dependent Probe Amplification (MLPA) analysis is available to determine the copy number of almost all exons of the PAX6 gene. Genomic deletions/duplications of 12 genes neighboring the PAX6 locus (including those genes involved in the WAGR syndrome) may also be detected with this MLPA analysis. Carrier testing and prenatal diagnosis is available once the mutation in a family has been defined.
Information Sheet (PAX6)
Information Sheet (SOX2, SIX6)
Consent Document
Genetic Test Sample Submission Form (Test Requisition Form) including Payment Options
Aniridia, Iris, Eye, Wilms, WAGR, PAX, SOX, SIX, Anophthalmia, Anopthalmia, Microphthalmia, Micropthalmia, Coloboma, Cataract, Optic nerve
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