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Sanfilippo P.G.,University of Melbourne | Medland S.E.,Queensland Institute for Medical Research | Hewitt A.W.,University of Melbourne | Kearns L.S.,University of Melbourne | And 8 more authors.
Investigative Ophthalmology and Visual Science | Year: 2011

PURPOSE. To compare the distributional parameters for a series of ocular biometric traits between twins and their singleton siblings, to evaluate the generalizability of twin data, as used in heritability analyses to the general population. METHODS. A series of birth, anthropometric, and 13 ocular biometric traits were selected for analysis: interpupillary distance (IPD), visual acuity (logMAR), spherical equivalent refractive error, corneal curvature, axial length, anterior chamber depth (ACD), central corneal thickness (CCT), intraocular pressure (IOP), optic disc, cup and rim areas, and measures of retinal vessel caliber; central retinal arteriolar equivalent (CRAE), and central retinal venular equivalent (CRVE). Structural equation modeling was used to test the assumption that the means and variances for each trait did not differ between twins and their siblings. RESULTS. Significant differences in log-likelihood for birth weight and gestational age were observed between twins and siblings, with the latter being both heavier and closer to fullterm at birth. Siblings were also found to have larger IPD and axial length, and better visual acuity compared with their twin counterparts. Refractive error, corneal curvature, ACD, CCT, optic disc parameters, and retinal vascular calibers did not differ significantly between the two groups. CONCLUSIONS. Twins are representative of the general population for some but not all measures of ocular biometry. Consequently, care should be taken when extrapolating twin data for these traits in heritability and other genetic studies. Birth weight differences between twins and siblings do not appear to account for the differences in ocular biometry observed in this study. © 2011 The Association for Research in Vision and Ophthalmology, Inc. Source

Sanfilippo P.G.,University of Melbourne | Chu B.-S.,Catholic University of Daegu | Bigault O.,University of Melbourne | Kearns L.S.,University of Melbourne | And 7 more authors.
Acta Ophthalmologica | Year: 2014

Purpose To investigate the age range for which cycloplegia provides additional information compared with non-cycloplegic refraction in teenagers and young adults. Methods Data for 1295 subjects (704 female; 591 male) from the Twins Eye Study in Tasmania (TEST) and the Brisbane Adolescent Twin Study (mean age: 19.65 ± 3.56, range: 13-26 years) were included. For all participants, cycloplegia was induced by instillation of either one drop of 1% cyclopentolate (13-14 years) or one drop of 1% tropicamide (15-26 years). Pre- and postcycloplegic refractive errors for both eyes were measured using a Humphrey-598 automated refractor and spherical equivalents of refractive error were calculated. Generalized Estimating Equations (GEE) were used to model the spherical equivalent refraction (SER) for each eye against age (by year) and axial length (in the given eye). Results The mean group difference between pre- and postcycloplegic SER (post minus pre) was 0.17 ± 0.52 D and 0.12 ± 0.51 D for the right and left eyes, respectively, indicating that postcycloplegic refraction was generally more hyperopic/less myopic. The mean difference between pre- and postcycloplegic SER decreased from 0.36 ± 0.41 D in the 13-year-olds to 0.06 ± 0.50 D in people aged 25 years. After adjusting for family-relatedness, the difference between pre- and postcycloplegia SER was significant in all age groups up until the age of 20 years. Conclusions Non-cycloplegic autorefraction can result in group mean SER differences of greater myopia than cycloplegic autorefraction and occurs in teenagers (13-19 years of age), but not in adults 20-26 years. These data suggest that cycloplegia is not required in population estimates of refractive error for young adults once they reach approximately 20 years of age. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd. Source

Taylor W.D.,Duke University | Taylor W.D.,Duke Neuropsychiatric Imaging Research Laboratory | Benjamin S.,Duke University | McQuoid D.R.,Duke University | And 7 more authors.
Psychiatry Research - Neuroimaging | Year: 2012

The renin-angiotensin system (RAS) is implicated in the response to physiological and psychosocial stressors, but its role in stress-related psychiatric disorders is poorly understood. We examined if variation in AGTR1, the gene coding for the type 1 angiotensin II receptor (AT1R), is associated with a diagnosis of depression and differences in white matter hyperintensities and frontotemporal brain volumes. Participants comprised 257 depressed and 116 nondepressed elderly Caucasian subjects who completed clinical assessments and provided blood samples for genotyping. We used a haplotype-tagging single nucleotide polymorphism (htSNP) analysis to test for variation in AGTR1. For measurement of hyperintense lesions, 1.5 Tesla magnetic resonance imaging (MRI) data were available on 33 subjects. For measurements of the hippocampus and dorsolateral prefrontal cortex (dlPFC), 3 Tesla MRI data were available on 70 subjects. Two htSNPs exhibited statistically significant frequency differences between diagnostic cohorts: rs10935724 and rs12721331. Although hyperintense lesion volume did not significantly differ by any htSNP, dlPFC and hippocampus volume differed significantly for several htSNPs. Intriguingly, for those htSNPs differing significantly for both dlPFC and hippocampus volume, the variant associated with smaller dlPFC volume was associated with larger hippocampal volume. This supports the idea that genetic variation in AGTR1 is associated with depression and differences in frontotemporal morphology. © 2012 Elsevier Ireland Ltd. Source

Tran-Viet K.-N.,Duke Center for Human Genetics | Tran-Viet K.-N.,University of California at Berkeley | Soler V.,Duke Center for Human Genetics | Soler V.,University Paul Sabatier | And 19 more authors.
Molecular Vision | Year: 2013

Purpose: Stickler syndrome is an arthro-ophthalmopathy with phenotypic overlap with Wagner syndrome. The common Stickler syndrome type I is inherited as an autosomal dominant trait, with causal mutations in collagen type II alpha 1 (COL2A1). Wagner syndrome is associated with mutations in versican (VCAN), which encodes for a chondroitin sulfate proteoglycan. A three-generation Caucasian family variably diagnosed with either syndrome was screened for sequence variants in the COL2A1 and VCAN genes. Methods: Genomic DNA samples derived from saliva were collected from all family members (six affected and four unaffected individuals). Complete sequencing of COL2A1 and VCAN was performed on two affected individuals. Direct sequencing of remaining family members was conducted if the discovered variants followed segregation. Results: A base-pair substitution (c.258C>A) in exon 2 of COL2A1 cosegregated with familial disease status. This known mutation occurs in a highly conserved site that causes a premature stop codon (p.C86X). The mutation was not seen in 1,142 ethnically matched control DNA samples. Conclusions: Premature stop codons in COL2A1 exon 2 lead to a Stickler syndrome type I ocular-only phenotype with few or no systemic manifestations. Mutation screening of COL2A1 exon 2 in families with autosomal dominant vitreoretinopathy is important for accurate clinical diagnosis. © 2013 Molecular Vision. Source

Tran-Viet K.-N.,Duke Center for Human Genetics | Powell C.,Duke Center for Human Genetics | Barathi V.A.,National University of Singapore | Barathi V.A.,Singapore Eye Research Institute | And 22 more authors.
American Journal of Human Genetics | Year: 2013

Myopia, or near-sightedness, is an ocular refractive error of unfocused image quality in front of the retinal plane. Individuals with high-grade myopia (dioptric power greater than -6.00) are predisposed to ocular morbidities such as glaucoma, retinal detachment, and myopic maculopathy. Nonsyndromic, high-grade myopia is highly heritable, and to date multiple gene loci have been reported. We performed exome sequencing in 4 individuals from an 11-member family of European descent from the United States. Affected individuals had a mean dioptric spherical equivalent of -22.00 sphere. A premature stop codon mutation c.157C>T (p.Gln53*) cosegregating with disease was discovered within SCO2 that maps to chromosome 22q13.33. Subsequent analyses identified three additional mutations in three highly myopic unrelated individuals (c.341G>A, c.418G>A, and c.776C>T). To determine differential gene expression in a developmental mouse model, we induced myopia by applying a -15.00D lens over one eye. Messenger RNA levels of SCO2 were significantly downregulated in myopic mouse retinae. Immunohistochemistry in mouse eyes confirmed SCO2 protein localization in retina, retinal pigment epithelium, and sclera. SCO2 encodes for a copper homeostasis protein influential in mitochondrial cytochrome c oxidase activity. Copper deficiencies have been linked with photoreceptor loss and myopia with increased scleral wall elasticity. Retinal thinning has been reported with an SC02 variant. Human mutation identification with support from an induced myopic animal provides biological insights of myopic development. © 2013 The American Society of Human Genetics. Source

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