Clinical and mutation analysis of 51 probands with anophthalmia and/or severe microphthalmia from a single center

Abstract

Clinical evaluation and mutation analysis was performed in 51 consecutive probands with severe eye malformations - anophthalmia and/or severe microphthalmia - seen in a single specialist ophthalmology center. The mutation analysis consisted of bidirectional sequencing of the coding regions of SOX2, OTX2, PAX6 (paired domain), STRA6, BMP4, SMOC1, FOXE3, and RAX, and genome-wide array-based copy number assessment. Fifteen (29.4%) of the 51 probands had likely causative mutations affecting SOX2 (9/51), OTX2 (5/51), and STRA6 (1/51). Of the cases with bilateral anophthalmia, 9/12 (75%) were found to be mutation positive. Three of these mutations were large genomic deletions encompassing SOX2 (one case) or OTX2 (two cases). Familial inheritance of three intragenic, plausibly pathogenic, and heterozygous mutations was observed. An unaffected carrier parent of an affected child with an identified OTX2 mutation confirmed the previously reported nonpenetrance for this disorder. Two families with SOX2 mutations demonstrated a parent and child both with significant but highly variable eye malformations. Heterozygous loss-of-function mutations in SOX2 and OTX2 are the most common genetic pathology associated with severe eye malformations and bi-allelic loss-of-function in STRA6 is confirmed as an emerging cause of nonsyndromal eye malformations.

Keywords: Anophthalmia; BMP4; FOXE3; OTX2; PAX6; RAX; SMOC1; SOX2; STRA6; array CGH; coloboma; de novo mutations; gene deletion; haploinsufficiency; microphthalmia; missense mutations; transcription factors.

Figure 1

Schematic diagram showing three heterozygous deletions identified by array comparative genomic hybridization (CGH). (A) A de novo 1.69 Mb deletion in CaseID 2850 (chr3:182,649,000–184,339,000 equivalent to hg19 chr3:181,166,306–182,856,306) resulting in a loss of a single copy of SOX2, shown in red. Deletions are marked by red bars. Genomic coordinates are based on the March 2006 Human Genome Assembly (NCBI36/hg18). (B) A 6.5 Mb deletion in CaseID 3000 (chr14:56,094,000–62,594,000; equivalent to hg19 chr14:57,024,247–63,524-247) and a de novo 455 kb deletion in CaseID 3346 (chr14:56,224,000–56,679,000; equivalent to hg19 chr14:57,154,247–57,609,247). Both deletions resulted in a loss of a single copy of OTX2, shown in red.

Figure 2

Portrait images of patients with a mutation in the SOX2 gene. Affected son at age 3 years and his mother with unilateral anophthalmia at the right and left side (FamID 3432), respectively, are shown in the upper panel. The daughter with right anophthalmia, left microphthalmia, and microcornea at age 5 months and her mother with bilateral irido and left > right chorio-retinal coloboma are shown in the middle and fundus images in the left panel (CaseID 3327). Lower panel shows CaseID 3194 and CaseID 2850 at age 3 months and CaseID 3370 at 4 years (wears prosthetic shells) with bilateral anophthalmia, CaseID 3303 with right anophthalmia (wears prosthesis) and left microphthalmia, sclerocornea and microcornea at age 4 years, CaseID 3797 with right anophthalmia and left microphthalmia, sclerocornea and microcornea at age 3 months (small image).

Figure 3

Cerebral abnormalities associated with a mutation in SOX2 gene. Cavum vergae in a 3-year-old child with unilateral anophthalmia (CaseID 3432; proton-weighted sagittal and transversal spine echo 3 mm scan). Pineal cyst in a child with bilateral anophthalmia (note: orbital expander OU; CaseID 2850 at age 4.5 years; T2-weighted sagittal and T1-weighted transversal spine echo 3-mm scan). Small posterior part of the corpus callosum and septum pellucidum cyst in a child with bilateral anophthalmia (CaseID 3194 at age 3 months; T2-weighted sagittal and transversal spine echo 3-mm scan). Fronto-temporal cerebral volume reduction (T2-weighted native sagittal spine echo 2 mm and transversal 4-mm scan) in a 3-month-old boy with bilateral anophthalmia (CaseID 2813)

Figure 4

Portrait images of the children with mutations in the OTX2 gene: CaseID 2867 at age 1 year with right anophthalmia (wears prosthetic shell) and left microphthalmia and microcornea. CaseID 2896 with bilateral anophthalmia and left microtia at age 3 months and age 6 years (wears prosthetic shells both sides; upper panel). CaseID 3000 at age 9 years with bilateral anophthalmia (wears prosthetic shell on the left side). CaseID 3197 with right anophthalmia at age 3 months. CaseID 3346 at age 1 year with bilateral anophthalmia (wears prosthetic shell on the right side).

Figure 5

Chest X-ray (anterior–posterior scan) and chest CAT scan (axial and anterior–posterior scan) of CaseID 3279 with STRA6 mutation show an elevated diaphragm, a right–left lung asymmetry with reduced lung volume in the left lung, and left-shifted heart.