Myopia and Late-Onset Progressive Cone Dystrophy Associate to LVAVA/MVAVA Exon 3 Interchange Haplotypes of Opsin Genes on Chromosome X
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Genetics Myopia and Late-Onset Progressive Cone Dystrophy Associate to LVAVA/MVAVA Exon 3 Interchange Haplotypes of Opsin Genes on Chromosome X Orsolya Orosz,1 Istv´an Rajta,2 Attila Vajas,1 Lili Tak´acs,1 Adrienne Csutak,1 Mariann Fodor,1 Bence Kolozsv´ari,1 Miklos´ Resch,3 Katalin Senyi,´ 3 Bal´azs Lesch,3 Viktoria´ Szabo,´ 3 Andr´as Berta,1 Istv´an Balogh,4 and Gergely Losonczy1,5 1Department of Ophthalmology, University of Debrecen, Debrecen, Hungary 2Institute for Nuclear Research, Hungarian Academy of Sciences, Debrecen, Hungary 3Department of Ophthalmology, Semmelweis University, Budapest, Hungary 4Division of Clinical Genetics, Department of Laboratory Medicine, University of Debrecen, Debrecen, Hungary 5Department of Ophthalmology, Zuyderland-Eyescan, Sittard-Geleen, The Netherlands Correspondence: Gergely Losonczy, PURPOSE. Rare interchange haplotypes in exon 3 of the OPN1LW and OPN1MW opsin genes Department of Ophthalmology, Uni- cause X-linked myopia, color vision defect, and cone dysfunction. The severity of the disease versity of Debrecen, H-4032, Na- varies on a broad scale from nonsyndromic high myopia to blue cone monochromatism. Here, gyerdei krt. 98, Debrecen, Hungary; we describe a new genotype–phenotype correlation attributed to rare exon 3 interchange [email protected]. haplotypes simultaneously present in the long- and middle-wavelength sensitive opsin genes Submitted: December 31, 2016 (L- and M-opsin genes). Accepted: February 28, 2017 METHODS. A multigenerational family with X-linked high myopia and cone dystrophy was Citation: Orosz O, Rajta I, Vajas A, et investigated. al. Myopia and late-onset progressive cone dystrophy associate to LVAVA/ RESULTS. Affected male patients had infantile onset myopia with normal visual acuity and color MVAVA exon 3 interchange haplotypes vision until their forties. Visual acuity decreased thereafter, along with the development of of opsin genes on chromosome X. severe protan and deutan color vision defects. A mild decrease in electroretinography Invest Ophthalmol Vis Sci. response of cone photoreceptors was detected in childhood, which further deteriorated in 2017;58:1834–1842. DOI:10.1167/ middle-aged patients. Rods were also affected, however, to a lesser extent than cones. Clinical iovs.16-21405 exome sequencing identified the LVAVA and MVAVA toxic haplotypes in the OPN1LW and OPN1MW opsin genes, respectively. CONCLUSION. Here, we show that LVAVA haplotype of the OPN1LW gene and MVAVA haplotype of the OPN1MW gene cause apparently nonsyndromic high myopia in young patients but lead to progressive cone–rod dystrophy with deuteranopia and protanopia in middle-aged patients corresponding to a previously unknown disease course. To the best of our knowledge, this is the first report on the joint effect of these toxic haplotypes in the two opsin genes on chromosome X. Keywords: X-linked high myopia, cone dystrophy, LVAVA he long- and middle-wavelength sensitive opsin genes (L- amino acids present at these locations. Normal opsin genes T and M-opsin genes; OPN1LW, OPN1MW, respectively) specify the haplotypes LVAIS and MVAIA in the L and M genes, reside in a head-to-tail tandem array on Xq28 and share 98% respectively. Toxic opsin variants that have been discovered in nucleotide identity.1 The normal gene array is composed of a human opsin-related diseases so far include LVAVA, LIAVA, locus control region (LCR), a single L gene followed by one or LIAVS, LIVVA, MVVVA, and MIAVA.4,11,26–31 Patients reported so more M genes with only the first two genes in the array far with an exon 3 interchange haplotype are summarized in expressed due to their proximity to the upstream cis-regulatory the Supplementary Material. Toxic exon 3 interchange haplo- LCR.2–5 Mutations in the LCR, L- (OPN1LW), and M- (OPN1MW) types have been commonly reported in BED.14,26,29,32–34 BED opsin genes on Xq28 lead to various X-linked cone-photore- was originally described in a family from the Danish island of ceptor disorders including red-green color vision defects Bornholm.32 The second family with BED from Minnesota had (Online Mendelian Inheritance in Man [OMIM] #303800 and also a Danish origin.14 Affected males had infantile onset #303900), X-linked cone dysfunction (Bornholm Eye Disease myopia with astigmatism, decreased visual acuity from child- [BED], OMIM #300843), X-linked cone dystrophy, and blue hood, subnormal photopic, and normal scotopic electroretino- cone monochromatism (BCM; OMIM #303700).1,4,6–25 Rare gram (ERG) parameters with normal macular appearance. The exon 3 interchange haplotypes are a recently described group disease showed no progression with age. The first family had a of mutations of the opsin genes on chromosome X, which deutan while the second had a protan color vision defect. The involve amino acid residues 153, 171, 174, 178, and 180, and disease was accounted for by the LVAVA interchange haplotype their name is the acronym of the one letter code of specific in one of the first two genes in the opsin gene array in both Copyright 2017 The Authors iovs.arvojournals.org j ISSN: 1552-5783 1834 This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. Downloaded from iovs.arvojournals.org on 09/25/2021 Rare Opsin Haplotypes Cause Late-Onset Cone Dystrophy IOVS j March 2017 j Vol. 58 j No. 3 j 1835 families. This observation was the first to identify LVAVA acuity along with color vision deficiency in patients older than haplotype as a cause of BED.26 LVAVA haplotype associated to a 40 years. similar phenotype with either protan or deutan color vision defect in four individuals from four recently reported families.28 Rare interchange haplotypes have been shown to METHODS cause skipping of exon 3, a frame shift and premature termination of translation. However, in contrast to the LIAVA Patients and Ophthalmology Investigations haplotype, there was a residual low level of correctly spliced In the present study, we have investigated members of a three- opsin mRNA with the LVAVA or MIAVA haplotypes observed generation family with X-linked high-grade myopia. Autorefrac- indicating some amount of functionally normal opsin pro- 29,35 tometry was performed using a Topcon KR 8100 equipment teins. Accordingly, color vision defect was explained by (Topcon Corp., Tokyo, Japan). Color vision was tested under the lack of either L- or M-opsin genes in the first two positions standardized conditions, with pseudoisochromatic plates of the opsin gene array instead of a direct opsin inactivating 26 (Tafeln und Prufung¨ des Farbensinnes, 29. Auflage, 2002), effect in patients with the LVAVA haplotype. These observa- the Farnsworth Munsell 100-hue test and the anomaloscope tion suggests that the LVAVA haplotype has a dominant effect Nagel type II test. Color fundus photographs were taken with a on the development of myopia, a key element of BED, Zeiss FF450þIR fundus camera (Carl Zeiss AG, Jena, Germany) however, it is transcribed at a sufficient level to provide 26 mounted with a ZK-5 color sensor (Allied Vision Technologies normal opsin function. The strongest clinical evidence GmbH, Stadtroda, Germany) operated with Zeiss Visupack 4.4 supporting this hypothesis is the report on two Chinese software. Optical coherence tomography and confocal-scan- families with nonsyndromic high myopia associating to the 33,34 ning laser fundus autofluorescence (FAF) imaging was per- LVAVA haplotype. However, this represents a strikingly formed with Spectralis OCT (Heidelberg Engineering, different phenotype than observed in BED patients with the Heidelberg, Germany). Electroretinography was executed with same haplotype. Interestingly, the LVAVA haplotype is unique Ganzfeld Q400 equipment (Roland Consult GmbH, Branden- among interchange mutations in another aspect as well. burg, Germany) using standard International Society for According to its definition, BED is a nonprogressive disease. Clinical Electrophysiology of Vision parameters.36 Measures However, a spectral-domain optical coherence tomography of photoreceptor dysfunction were defined as: mild (70%–99% (SD-OCT) and adaptive optics scanning laser ophthalmoscopy of normal amplitude), moderate (30%–69% of normal), severe analysis of two patients with an LVAVA-only genotype showed (1%–29% of normal), or undetectable. The research was characteristic signs of progressive macular dystrophy including performed according to the Declaration of Helsinki and was overall retinal thinning, mottling of photoreceptor inner approved by the local institutional review boards. Written segments, and structural disruption of the inner retina and 27 informed consent was obtained from participating family the outer nuclear layer. This finding indicated that LVAVA members prior to investigation. haplotype causes progressive degenerative changes that result in damage to neighboring cells in addition to those expressing the mutated opsin. Moreover, these patients gradually devel- Isolation of Genomic DNA oped clinical signs of BED during their elementary school Genomic DNA was isolated from EDTA or citrate anticoagulat- years, representing a somewhat later disease onset than ed blood using the QIAamp Blood Mini kit according to the 27 observed in other BED patients. Taken together, our manufacturer’s instructions (Qiagen GmbH, Hilden, Germany). understanding on the genotype–phenotype correlation associ- ating to the LVAVA haplotype has largely developed since the first description of BED as a stationary disease with color vision