Examination of SOX2 in variable ocular conditions identifies a recurrent deletion in microphthalmia and lack of mutations in other phenotypes

PURPOSE: The role of SRY-Box 2 (SOX2) in anophthalmia/microphthalmia (A/M) is well known, with 10%–20% of A/M explained by mutations in SOX2. SOX2 plays roles in the development of both the posterior and anterior segment structures of the eye and relies on interactions with tissue-specific partner proteins to execute its function, raising the possibility that SOX2 mutations may result in varying ocular phenotypes. Recent data has identified a missense mutation in SOX2 in an extended pedigree with phenotypes as varied as A/M, isolated iris hypoplasia, iris and chorioretinal coloboma, pupil defects, and hypermetropia, suggesting a broader phenotypic spectrum associated with SOX2 mutations. METHODS: Screening of SOX2 was completed in 89 patients with a variety of ocular anomalies, including 28 with A/M and 61 with normal eye size and anterior segment dysgenesis (28), cataract (14), isolated coloboma (5), or other eye disorders (14). RESULTS: The recurrent de novo frameshift mutation c.70del20 was identified in one patient with microphthalmia and syndromic anomalies consistent with SOX2 anophthalmia syndrome; the mutation frequency in our A/M population (4%) was lower than previously reported; it is likely that extensive utilization of clinical SOX2 testing has led to a bias toward SOX2-negative A/M cases in our research cohort. No disease-causing mutations were identified in patients with non-microphthalmia phenotypes. CONCLUSIONS: The recurrent c.70del20 mutation accounts for 21% of all independent SOX2 mutations reported to date. Due to the increased use of clinical SOX2 testing, the frequency of SOX2 mutations identified in research A/M populations will likely continue to decrease. Mutations in SOX2 do not appear to be a common cause of ocular defects other than anophthalmia/microphthalmia.