First report of OPA1 screening in Greek patients with autosomal dominant optic atrophy and identification of a previously undescribed OPA1 mutation

Abstract

Purpose: To describe the genotype-phenotype correlation in four Greek pedigrees with autosomal dominant optic atrophy (ADOA) and OPA1 mutations.

Methods: Seven patients from four unrelated families (F1, F2, F3, F4) were clinically assessed for visual acuity, color vision, ptosis, afferent pupillary defects, and visual fields and underwent orthoptic assessment, slit-lamp biomicroscopy, and fundus examination to establish their clinical status. Genomic DNA was extracted from peripheral blood samples from all participants. The coding region (exons 1-28), including the intron-exon boundaries of the OPA1 gene, was screened in the probands of the four families, as well as in seven additional family members (four affected and three unaffected) with PCR and direct DNA sequencing.

Results: All patients presented bilateral decrease in best-corrected visual acuity and temporal pallor of the optic disc. The visual fields of the adult patients showed characteristic scotomata. Other signs were present in some patients such as decreased color discrimination and a gray crescent within the neuroretinal rim. After the OPA1 gene was sequenced, a previously undescribed heterozygous splice-site mutation c.784-1G>T in intron 7 was detected in family F2. In families F1, F3, and F4, a previously reported in-frame deletion c.876_878delTGT/p.(Val294del), the frameshift c.2366delA/p.(Asn789Metfs*11), and splice-site c.1140+5G>C mutations were detected, respectively.

Conclusions: This is the first report of molecular characterization of Greek patients with ADOA. Our findings provide additional information regarding the genotype-phenotype correlation and establish the role of the OPA1 gene in Greek patients with ADOA.

Figure 1

DNA sequence analysis of exon 9 and flanking sequences of the OPA1 gene in family F1. A: Pedigree F1. The arrow indicates the proband. Affected and unaffected individuals are represented with black and open circles, respectively. Males are represented with a quadrant and females with a circle. The asterisk sign indicates individuals clinically and genetically examined. B: Mutant sequence in proband F1 II:5. The antisense sequence confirmed the same in-frame mutation. C: Normal sequence. The horizontal lines in B and C indicate deletion of the three nucleotides TGT (c.876_878delTGT) resulting in the in-frame deletion of valine at codon 294 of the OPA1 protein [p.(Valdel294)].

Figure 2

DNA sequence analysis of exon 8 and flanking sequences of the OPA1 gene in family F2. A: Pedigree F2. The arrow indicates the proband. Affected and unaffected individuals are represented with black and open circles, respectively. Males are represented with a quadrant and females with a circle. The asterisk sign indicates individuals both clinically and genetically examined. B: Mutant sequence in proband F2 II:1. The antisense sequence confirmed the same splicing site mutation. C: Normal sequence. The arrows in B and C indicate the position of the G to T substitution at the 3′ acceptor splice site of intron 7 (c.784–1G>T).

Figure 3

DNA sequence analysis of exon 24 and flanking sequences of the OPA1 gene in family F3. A: Pedigree F3. The arrow indicates the proband. Affected and unaffected individuals are represented with black and open circles, respectively. Males are represented with a quadrant and females with a circle. The asterisk sign indicates individuals both clinically and genetically examined. Questions marks indicate probably affected family members. B: Mutant sequence in proband F3 III:24. The antisense sequence confirmed the same in-frame mutation. C: Normal sequence. The arrows in B and C indicate the deletion of nucleotide A (c.2366delA) resulting in the frameshift p.(Asn789Metfs*11) mutation of the OPA1 protein.

Figure 4

DNA sequence analysis of exon 11 and flanking sequences of the OPA1 gene in family F4. A: Pedigree F4. The arrow indicates the proband. Affected and unaffected individuals are represented with black and open circles, respectively. Males are represented with a quadrant and females with a circle. The asterisk sign indicates individuals both clinically and genetically examined. B: Mutant sequence in proband F4 III:1. C: Normal sequence. The arrows in B and C indicate the position of the G to C substitution at the fifth nucleotide of the 5′ donor site of intron 11.

Figure 5

Left Humphrey 30–2 visual field showing a cecocentral scotoma of the proband F1 II:5.

Figure 6

Fundus photograph of the right eye shows optic nerve temporal pallor in the patient F3 III:24 with dominant optic atrophy.

Figure 7

Fundus photograph of the left optic disc showing gray crescent situated temporally in patient F3 III:24.