Genomics

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Castle MJ, Turunen HT, Vandenberghe LH, Wolfe JH. Controlling AAV Tropism in the Nervous System with Natural and Engineered Capsids. Methods Mol Biol 2016;1382:133-49.Abstract

More than one hundred naturally occurring variants of adeno-associated virus (AAV) have been identified, and this library has been further expanded by an array of techniques for modification of the viral capsid. AAV capsid variants possess unique antigenic profiles and demonstrate distinct cellular tropisms driven by differences in receptor binding. AAV capsids can be chemically modified to alter tropism, can be produced as hybrid vectors that combine the properties of multiple serotypes, and can carry peptide insertions that introduce novel receptor-binding activity. Furthermore, directed evolution of shuffled genome libraries can identify engineered variants with unique properties, and rational modification of the viral capsid can alter tropism, reduce blockage by neutralizing antibodies, or enhance transduction efficiency. This large number of AAV variants and engineered capsids provides a varied toolkit for gene delivery to the CNS and retina, with specialized vectors available for many applications, but selecting a capsid variant from the array of available vectors can be difficult. This chapter describes the unique properties of a range of AAV variants and engineered capsids, and provides a guide for selecting the appropriate vector for specific applications in the CNS and retina.

Cepko C. Intrinsically different retinal progenitor cells produce specific types of progeny. Nat Rev Neurosci 2014;15(9):615-27.Abstract
Lineage studies conducted in the retina more than 25 years ago demonstrated the multipotency of retinal progenitor cells (RPCs). The number and types of cells produced by individual RPCs, even from a single time point in development, were found to be highly variable. This raised the question of whether this variability was due to intrinsic differences among RPCs or to extrinsic and/or stochastic effects on equivalent RPCs or their progeny. Newer lineage studies that have made use of molecular markers of RPCs, retrovirus-mediated lineage analyses of specific RPCs and live imaging have begun to provide answers to this question. RPCs that produce two postmitotic daughter cells - that is, terminally dividing RPCs - have been the most well characterized RPCs to date, and have been shown to produce specific types of daughter cells. In addition, recent studies have begun to shed light on the mechanisms that drive the temporal order in which retinal cells are born.
Chan W, Wiggs JL, Sobrin L. The Genetic Influence on Corticosteroid-Induced Ocular Hypertension: A Field Positioned for Discovery. Am J Ophthalmol 2019;202:1-5.Abstract
PURPOSE: To provide evidence that corticosteroid-induced ocular hypertension has a genetic component. DESIGN: Evidence-based perspective. METHODS: We conducted a comprehensive literature search for studies exploring genetic influences on intraocular pressure responses to corticosteroid treatment. RESULTS: Studies demonstrating increased risk of corticosteroid-induced ocular hypertension among first-degree relatives of affected individuals support a genetic contribution to the disease. Family and personal history of primary open-angle glaucoma also increases the risk of corticosteroid-induced intraocular pressure elevation, suggesting common genetic etiologies. A number of studies have attempted to identify predisposing genetic factors; however, reproducible findings have not yet been reported. The recent availability of large data sets with clinical and genetic data for patients affected by corticosteroid-induced ocular hypertension and glaucoma provides new opportunities to study the genetic underpinnings of this important condition. CONCLUSIONS: There is substantial evidence suggesting a genetic component to corticosteroid-related ocular hypertension and glaucoma, but specific genetic risk factors have yet to be identified. The current confluence of large genetic data sets and affordable genetic sequencing technologies has great potential for discovering the genes that increase risk for this blinding complication of corticosteroid therapy.
Cheng L, Desai J, Miranda CJ, Duncan JS, Qiu W, Nugent AA, Kolpak AL, Wu CC, Drokhlyansky E, DeLisle MM, Chan W-M, Wei Y, Propst F, Reck-Peterson SL, Fritzsch B, Engle EC. Human CFEOM1 mutations attenuate KIF21A autoinhibition and cause oculomotor axon stalling. Neuron 2014;82(2):334-49.Abstract
The ocular motility disorder "Congenital fibrosis of the extraocular muscles type 1" (CFEOM1) results from heterozygous mutations altering the motor and third coiled-coil stalk of the anterograde kinesin, KIF21A. We demonstrate that Kif21a knockin mice harboring the most common human mutation develop CFEOM. The developing axons of the oculomotor nerve's superior division stall in the proximal nerve; the growth cones enlarge, extend excessive filopodia, and assume random trajectories. Inferior division axons reach the orbit but branch ectopically. We establish a gain-of-function mechanism and find that human motor or stalk mutations attenuate Kif21a autoinhibition, providing in vivo evidence for mammalian kinesin autoregulation. We identify Map1b as a Kif21a-interacting protein and report that Map1b⁻/⁻ mice develop CFEOM. The interaction between Kif21a and Map1b is likely to play a critical role in the pathogenesis of CFEOM1 and highlights a selective vulnerability of the developing oculomotor nerve to perturbations of the axon cytoskeleton.
Choquet H, Wiggs JL, Khawaja AP. Clinical implications of recent advances in primary open-angle glaucoma genetics. Eye (Lond) 2020;34(1):29-39.Abstract
Over the last decade, genetic studies, including genome-wide association studies (GWAS), have accelerated the discovery of genes and genomic regions contributing to primary open-angle glaucoma (POAG), a leading cause of irreversible vision loss. Here, we review the findings of genetic studies of POAG published in English prior to September 2019. In total, 74 genomic regions have been associated at a genome-wide level of significance with POAG susceptibility. Recent POAG GWAS provide not only insight into global and ethnic-specific genetic risk factors for POAG susceptibility across populations of diverse ancestry, but also important functional insights underlying biological mechanisms of glaucoma pathogenesis. In this review, we also summarize the genetic overlap between POAG, glaucoma endophenotypes, such as intraocular pressure and vertical cup-disc ratio (VCDR), and other eye disorders. We also discuss approaches recently developed to increase power for POAG locus discovery and to predict POAG risk. Finally, we discuss the recent development of POAG gene-based therapies and future strategies to treat glaucoma effectively. Understanding the genetic architecture of POAG is essential for an earlier diagnosis of this common eye disorder, predictive testing of at-risk patients, and design of gene-based targeted medical therapies none of which are currently available.
Chung DC, Bertelsen M, Lorenz B, Pennesi ME, Leroy BP, Hamel CP, Pierce E, Sallum J, Larsen M, Stieger K, Preising M, Weleber R, Yang P, Place E, Liu E, Schaefer G, DiStefano-Pappas J, Elci OU, McCague S, Wellman JA, High KA, Reape KZ. The Natural History of Inherited Retinal Dystrophy Due to Biallelic Mutations in the RPE65 Gene. Am J Ophthalmol 2019;199:58-70.Abstract
PURPOSE: To delineate the natural history of visual parameters over time in individuals with biallelic RPE65 mutation-associated inherited retinal dystrophy (IRD); describe the range of causative mutations; determine potential genotype/phenotype relationships; and describe the variety of clinical diagnoses. DESIGN: Global, multicenter, retrospective chart review. METHODS: Study Population: Seventy individuals with biallelic RPE65 mutation-associated IRD. PROCEDURES: Data were extracted from patient charts. MEASUREMENTS: Visual acuity (VA), Goldmann visual field (GVF), optical coherence tomography, color vision testing, light sensitivity testing, and electroretinograms (retinal imaging and fundus photography were collected and analyzed when available). RESULTS: VA decreased with age in a nonlinear, positive-acceleration relationship (P < .001). GVF decreased with age (P < .0001 for both V4e and III4e), with faster GVF decrease for III4e stimulus vs V4e (P = .0114, left eye; P = .0076, right eye). On average, a 1-year increase in age decreased III4e GVF by ∼25 sum total degrees in each eye while V4e GVF decreased by ∼37 sum total degrees in each eye, although individual variability was observed. A total of 78 clinical diagnoses and 56 unique RPE65 mutations were recorded, without discernible RPE65 mutation genotype/phenotype relationships. CONCLUSIONS: The number of clinical diagnoses and lack of a consistent RPE65 mutation-to-phenotype correlation underscore the need for genetic testing. Significant relationships between age and worsening VA and GVF highlight the progressive loss of functional retina over time. These data may have implications for optimal timing of treatment for IRD attributable to biallelic RPE65 mutations.
Cogné B, Latypova X, Senaratne LDS, Martin L, Koboldt DC, Kellaris G, Fievet L, Le Meur G, Caldari D, Debray D, Nizon M, Frengen E, Bowne SJ, Consortium L99, Cadena EL, Daiger SP, Bujakowska KM, Pierce EA, Gorin M, Katsanis N, Bézieau S, Petersen-Jones SM, Occelli LM, Lyons LA, Legeai-Mallet L, Sullivan LS, Davis EE, Isidor B. Mutations in the Kinesin-2 Motor KIF3B Cause an Autosomal-Dominant Ciliopathy. Am J Hum Genet 2020;106(6):893-904.Abstract
Kinesin-2 enables ciliary assembly and maintenance as an anterograde intraflagellar transport (IFT) motor. Molecular motor activity is driven by a heterotrimeric complex comprised of KIF3A and KIF3B or KIF3C plus one non-motor subunit, KIFAP3. Using exome sequencing, we identified heterozygous KIF3B variants in two unrelated families with hallmark ciliopathy phenotypes. In the first family, the proband presents with hepatic fibrosis, retinitis pigmentosa, and postaxial polydactyly; he harbors a de novo c.748G>C (p.Glu250Gln) variant affecting the kinesin motor domain encoded by KIF3B. The second family is a six-generation pedigree affected predominantly by retinitis pigmentosa. Affected individuals carry a heterozygous c.1568T>C (p.Leu523Pro) KIF3B variant segregating in an autosomal-dominant pattern. We observed a significant increase in primary cilia length in vitro in the context of either of the two mutations while variant KIF3B proteins retained stability indistinguishable from wild type. Furthermore, we tested the effects of KIF3B mutant mRNA expression in the developing zebrafish retina. In the presence of either missense variant, rhodopsin was sequestered to the photoreceptor rod inner segment layer with a concomitant increase in photoreceptor cilia length. Notably, impaired rhodopsin trafficking is also characteristic of recessive KIF3B models as exemplified by an early-onset, autosomal-recessive, progressive retinal degeneration in Bengal cats; we identified a c.1000G>A (p.Ala334Thr) KIF3B variant by genome-wide association study and whole-genome sequencing. Together, our genetic, cell-based, and in vivo modeling data delineate an autosomal-dominant syndromic retinal ciliopathy in humans and suggest that multiple KIF3B pathomechanisms can impair kinesin-driven ciliary transport in the photoreceptor.
and Consortium CCG, Cornelis MC, Byrne EM, Esko T, Nalls MA, Ganna A, Paynter N, Monda KL, Amin N, Fischer K, Renstrom F, Ngwa JS, Huikari V, Cavadino A, Nolte IM, Teumer A, Yu K, Marques-Vidal P, Rawal R, Manichaikul A, Wojczynski MK, Vink JM, Zhao JH, Burlutsky G, Lahti J, Mikkilä V, Lemaitre RN, Eriksson J, Musani SK, Tanaka T, Geller F, Luan J, Hui J, Mägi R, Dimitriou M, Garcia ME, Ho W-K, Wright MJ, Rose LM, Magnusson PKE, Pedersen NL, Couper D, Oostra BA, Hofman A, Ikram MA, Tiemeier HW, Uitterlinden AG, van Rooij FJA, Barroso I, Johansson I, Xue L, Kaakinen M, Milani L, Power C, Snieder H, Stolk RP, Baumeister SE, Biffar R, Gu F, Bastardot F, Kutalik Z, Jacobs DR, Forouhi NG, Mihailov E, Lind L, Lindgren C, Michaëlsson K, Morris A, Jensen M, Khaw K-T, Luben RN, Wang JJ, Männistö S, Perälä M-M, Kähönen M, Lehtimäki T, Viikari J, Mozaffarian D, Mukamal K, Psaty BM, Döring A, Heath AC, Montgomery GW, Dahmen N, Carithers T, Tucker KL, Ferrucci L, Boyd HA, Melbye M, Treur JL, Mellström D, Hottenga JJ, Prokopenko I, Tönjes A, Deloukas P, Kanoni S, Lorentzon M, Houston DK, Liu Y, Danesh J, Rasheed A, Mason MA, Zonderman AB, Franke L, Kristal BS, Kristal BS, Kristal BS, Kristal BS, Karjalainen J, Reed DR, Westra H-J, Evans MK, Saleheen D, Harris TB, Dedoussis G, Curhan G, Stumvoll M, Beilby J, Pasquale LR, Feenstra B, Bandinelli S, Ordovas JM, Chan AT, Peters U, Ohlsson C, Gieger C, Martin NG, Waldenberger M, Siscovick DS, Raitakari O, Eriksson JG, Mitchell P, Hunter DJ, Kraft P, Rimm EB, Boomsma DI, Borecki IB, Loos RJF, Wareham NJ, Vollenweider P, Caporaso N, Grabe HJ, Neuhouser ML, Wolffenbuttel BHR, Hu FB, Hyppönen E, Järvelin M-R, Cupples LA, Franks PW, Ridker PM, van Duijn CM, Heiss G, Metspalu A, North KE, Ingelsson E, Nettleton JA, van Dam RM, Chasman DI. Genome-wide meta-analysis identifies six novel loci associated with habitual coffee consumption. Mol Psychiatry 2015;20(5):647-56.Abstract
Coffee, a major dietary source of caffeine, is among the most widely consumed beverages in the world and has received considerable attention regarding health risks and benefits. We conducted a genome-wide (GW) meta-analysis of predominately regular-type coffee consumption (cups per day) among up to 91 462 coffee consumers of European ancestry with top single-nucleotide polymorphisms (SNPs) followed-up in ~30 062 and 7964 coffee consumers of European and African-American ancestry, respectively. Studies from both stages were combined in a trans-ethnic meta-analysis. Confirmed loci were examined for putative functional and biological relevance. Eight loci, including six novel loci, met GW significance (log10Bayes factor (BF)>5.64) with per-allele effect sizes of 0.03-0.14 cups per day. Six are located in or near genes potentially involved in pharmacokinetics (ABCG2, AHR, POR and CYP1A2) and pharmacodynamics (BDNF and SLC6A4) of caffeine. Two map to GCKR and MLXIPL genes related to metabolic traits but lacking known roles in coffee consumption. Enhancer and promoter histone marks populate the regions of many confirmed loci and several potential regulatory SNPs are highly correlated with the lead SNP of each. SNP alleles near GCKR, MLXIPL, BDNF and CYP1A2 that were associated with higher coffee consumption have previously been associated with smoking initiation, higher adiposity and fasting insulin and glucose but lower blood pressure and favorable lipid, inflammatory and liver enzyme profiles (P<5 × 10(-8)).Our genetic findings among European and African-American adults reinforce the role of caffeine in mediating habitual coffee consumption and may point to molecular mechanisms underlying inter-individual variability in pharmacological and health effects of coffee.
Consugar MB, Navarro-Gomez D, Place EM, Bujakowska KM, Sousa ME, Fonseca-Kelly ZD, Taub DG, Janessian M, Wang DY, Au ED, Sims KB, Sweetser DA, Fulton AB, Liu Q, Wiggs JL, Gai X, Pierce EA. Panel-based genetic diagnostic testing for inherited eye diseases is highly accurate and reproducible, and more sensitive for variant detection, than exome sequencing. Genet Med 2015;17(4):253-61.Abstract

PURPOSE: Next-generation sequencing-based methods are being adopted broadly for genetic diagnostic testing, but the performance characteristics of these techniques with regard to test accuracy and reproducibility have not been fully defined. METHODS: We developed a targeted enrichment and next-generation sequencing approach for genetic diagnostic testing of patients with inherited eye disorders, including inherited retinal degenerations, optic atrophy, and glaucoma. In preparation for providing this genetic eye disease (GEDi) test on a CLIA-certified basis, we performed experiments to measure the sensitivity, specificity, and reproducibility, as well as the clinical sensitivity, of the test. RESULTS: The GEDi test is highly reproducible and accurate, with sensitivity and specificity of 97.9 and 100%, respectively, for single-nucleotide variant detection. The sensitivity for variant detection was notably better than the 88.3% achieved by whole-exome sequencing using the same metrics, because of better coverage of targeted genes in the GEDi test as compared with a commercially available exome capture set. Prospective testing of 192 patients with inherited retinal degenerations indicated that the clinical sensitivity of the GEDi test is high, with a diagnostic rate of 51%. CONCLUSION: Based on quantified performance metrics, the data suggest that selective targeted enrichment is preferable to whole-exome sequencing for genetic diagnostic testing.Genet Med 17 4, 253-261.

Cronin T, Vandenberghe LH, Hantz P, Juttner J, Reimann A, Kacsó A-E, Huckfeldt RM, Busskamp V, Kohler H, Lagali PS, Roska B, Bennett J. Efficient transduction and optogenetic stimulation of retinal bipolar cells by a synthetic adeno-associated virus capsid and promoter. EMBO Mol Med 2014;6(9):1175-90.Abstract

In this report, we describe the development of a modified adeno-associated virus (AAV) capsid and promoter for transduction of retinal ON-bipolar cells. The bipolar cells, which are post-synaptic to the photoreceptors, are important retinal targets for both basic and preclinical research. In particular, a therapeutic strategy under investigation for advanced forms of blindness involves using optogenetic molecules to render ON-bipolar cells light-sensitive. Currently, delivery of adequate levels of gene expression is a limiting step for this approach. The synthetic AAV capsid and promoter described here achieves high level of optogenetic transgene expression in ON-bipolar cells. This evokes high-frequency (~100 Hz) spiking responses in ganglion cells of previously blind, rd1, mice. Our vector is a promising vehicle for further development toward potential clinical use.

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Dabul ANG, Avaca-Crusca JS, Van Tyne D, Gilmore MS, Camargo ILBC. Resistance in In Vitro Selected Tigecycline-Resistant Methicillin-Resistant Staphylococcus aureus Sequence Type 5 Is Driven by Mutations in mepR and mepA Genes. Microb Drug Resist 2018;24(5):519-526.Abstract
A tigecycline-susceptible (TGC-S) Sequence Type (ST) 5 clinical methicillin-resistant Staphylococcus aureus (MRSA) strain was cultured in escalating levels of tigecycline, yielding mutants eightfold more resistant. Their genomes were sequenced to identify genetic alterations, resulting in resistance. Alterations in rpsJ, commonly related to tigecycline resistance, were also investigated. Tigecycline resistance was mediated by loss-of-function mutations in the transcriptional repressor mepR, resulting in derepression of the efflux pump mepA. Increased levels of resistance were obtained by successive mutations in mepA itself. No alterations in RpsJ were observed in selected strains, but we observed a K57M substitution, previously correlated with resistance, among TGC-S clinical strains. Thus, the pathway to tigecycline resistance in CC5 MRSA in vitro appears to be derepression of mep operon as the result of mepR loss-of-function mutation, followed by alterations in MepA efflux pump. This shows that other evolutionary pathways, besides mutation of rpsJ, are available for evolving tigecycline resistance in CC5 MRSA.
Daniels AB, Sandberg MA, Chen J, Weigel-DiFranco C, Fielding Hejtmancic J, Berson EL. Genotype-phenotype correlations in Bardet-Biedl syndrome. Arch Ophthalmol 2012;130(7):901-7.Abstract
OBJECTIVE: To determine whether mutations in different Bardet-Biedl syndrome (BBS) genes result in different ocular phenotypes. METHODS: Thirty-seven patients from 31 families were enrolled who met the clinical criteria for BBS and for whom a BBS mutation had been identified. Seventeen patients harbored mutations in BBS1, 10 in BBS10, and 10 in other genes (BBS2, BBS3, BBS5, BBS7, and BBS12). All the patients underwent ocular examination; 36 patients had computerized full-field electroretinograms (ERGs). RESULTS: Visual acuity was significantly better in BBS1 patients than in patients with other BBS mutations (P=.01), and a larger proportion of BBS1 patients had good (≥20/50) visual acuity (P=.01). The ERG amplitudes were significantly higher in BBS1 patients than in patients with other BBS mutations in response to 0.5-Hz and 30-Hz flashes (P<.001 for both). All the BBS1 patients harbored at least 1 missense mutation compared with only 45% of patients with mutations in other BBS genes (P<.001); the rest harbored only null alleles. However, multivariate analysis demonstrated that visual acuity or ERG amplitude did not depend on the type of mutation present (missense or null) when controlling for BBS gene. Prevalences of bone spicule pigmentation and cataract were comparable in BBS subtypes. CONCLUSIONS: Patients with BBS1 mutations had a milder phenotype than did patients with mutations in other BBS genes. Clinically, this manifested as significantly better visual acuity and larger ERG amplitudes. CLINICAL RELEVANCE: These phenotypic differences can help guide genetic testing and genetic counseling for patients with this syndrome.
Di Gioia SA, Connors S, Matsunami N, Cannavino J, Rose MF, Gilette NM, Artoni P, de Macena Sobreira NL, Chan W-M, Webb BD, Robson CD, Cheng L, Van Ryzin C, Ramirez-Martinez A, Mohassel P, Leppert M, Scholand MB, Grunseich C, Ferreira CR, Hartman T, Hayes IM, Morgan T, Markie DM, Fagiolini M, Swift A, Chines PS, Speck-Martins CE, Collins FS, Jabs EW, Bönnemann CG, Olson EN, Olson EN, Carey JC, Robertson SP, Manoli I, Engle EC. A defect in myoblast fusion underlies Carey-Fineman-Ziter syndrome. Nat Commun 2017;8:16077.Abstract
Multinucleate cellular syncytial formation is a hallmark of skeletal muscle differentiation. Myomaker, encoded by Mymk (Tmem8c), is a well-conserved plasma membrane protein required for myoblast fusion to form multinucleated myotubes in mouse, chick, and zebrafish. Here, we report that autosomal recessive mutations in MYMK (OMIM 615345) cause Carey-Fineman-Ziter syndrome in humans (CFZS; OMIM 254940) by reducing but not eliminating MYMK function. We characterize MYMK-CFZS as a congenital myopathy with marked facial weakness and additional clinical and pathologic features that distinguish it from other congenital neuromuscular syndromes. We show that a heterologous cell fusion assay in vitro and allelic complementation experiments in mymk knockdown and mymk(insT/insT) zebrafish in vivo can differentiate between MYMK wild type, hypomorphic and null alleles. Collectively, these data establish that MYMK activity is necessary for normal muscle development and maintenance in humans, and expand the spectrum of congenital myopathies to include cell-cell fusion deficits.
Ding M, Ellervik C, Huang T, Jensen MK, Curhan GC, Pasquale LR, Kang JH, Wiggs JL, Hunter DJ, Willett WC, Rimm EB, Kraft P, Chasman DI, Qi L, Hu FB, Qi Q. Diet quality and genetic association with body mass index: results from 3 observational studies. Am J Clin Nutr 2018;108(6):1291-1300.Abstract
Background: It is unknown whether dietary quality modifies genetic association with body mass index (BMI). Objective: This study examined whether dietary quality modifies genetic association with BMI. Design: We calculated 3 diet quality scores including the Alternative Healthy Eating Index 2010 (AHEI-2010), the Alternative Mediterranean Diet score (AMED), and the Dietary Approach to Stop Hypertension (DASH) diet score. We examined the interactions of a genetic risk score (GRS) based on 97 BMI-associated variants with the 3 diet quality scores on BMI in 30,904 participants from 3 large cohorts. Results: We found significant interactions between total GRS and all 3 diet scores on BMI assessed after 2-3 y, with an attenuated genetic effect observed in individuals with healthier diets (AHEI: P-interaction = 0.003; AMED: P = 0.001; DASH: P = 0.004). For example, the difference in BMI (kg/m2) per 10-unit increment of the GRS was smaller among participants in the highest tertile of AHEI score compared with those in the lowest tertile (0.84; 95% CI: 0.72, 0.96 compared with 1.14; 95% CI: 0.99, 1.29). Results were consistent across the 3 cohorts with no significant heterogeneity. The interactions with diet scores on BMI appeared more significant for central nervous system GRSs (P < 0.01 for 3 diet scores) than for non-central nervous system GRSs (P > 0.05 for 3 diet scores). Conclusions: A higher diet quality attenuated genetic predisposition to obesity. These findings underscore the importance of maintaining a healthful diet for the prevention of obesity, particularly for those individuals with a strong genetic predisposition to obesity. This trial was registered with the Clinical Trial Registry as NCT03577639.
Dobyns WB, Aldinger KA, Ishak GE, Mirzaa GM, Timms AE, Grout ME, Dremmen MHG, Schot R, Vandervore L, van Slegtenhorst MA, Wilke M, Kasteleijn E, Lee AS, Barry BJ, Chao KR, Szczałuba K, Kobori J, Hanson-Kahn A, Bernstein JA, Carr L, D'Arco F, Miyana K, Okazaki T, Saito Y, Sasaki M, Das S, Wheeler MM, Bamshad MJ, Nickerson DA, of for Genomics UWCM, for at the of and Harvard CMGBIMIT, Engle EC, Verheijen FW, Doherty D, Mancini GMS. MACF1 Mutations Encoding Highly Conserved Zinc-Binding Residues of the GAR Domain Cause Defects in Neuronal Migration and Axon Guidance. Am J Hum Genet 2018;103(6):1009-1021.Abstract
To date, mutations in 15 actin- or microtubule-associated genes have been associated with the cortical malformation lissencephaly and variable brainstem hypoplasia. During a multicenter review, we recognized a rare lissencephaly variant with a complex brainstem malformation in three unrelated children. We searched our large brain-malformation databases and found another five children with this malformation (as well as one with a less severe variant), analyzed available whole-exome or -genome sequencing data, and tested ciliogenesis in two affected individuals. The brain malformation comprised posterior predominant lissencephaly and midline crossing defects consisting of absent anterior commissure and a striking W-shaped brainstem malformation caused by small or absent pontine crossing fibers. We discovered heterozygous de novo missense variants or an in-frame deletion involving highly conserved zinc-binding residues within the GAR domain of MACF1 in the first eight subjects. We studied cilium formation and found a higher proportion of mutant cells with short cilia than of control cells with short cilia. A ninth child had similar lissencephaly but only subtle brainstem dysplasia associated with a heterozygous de novo missense variant in the spectrin repeat domain of MACF1. Thus, we report variants of the microtubule-binding GAR domain of MACF1 as the cause of a distinctive and most likely pathognomonic brain malformation. A gain-of-function or dominant-negative mechanism appears likely given that many heterozygous mutations leading to protein truncation are included in the ExAC Browser. However, three de novo variants in MACF1 have been observed in large schizophrenia cohorts.
Dudek AM, Zabaleta N, Zinn E, Pillay S, Zengel J, Porter C, Franceschini JS, Estelien R, Carette JE, Zhou GL, Vandenberghe LH. GPR108 Is a Highly Conserved AAV Entry Factor. Mol Ther 2020;28(2):367-381.Abstract
Adeno-associated virus (AAV) is a highly promising gene transfer vector, yet major cellular requirements for AAV entry are poorly understood. Using a genome-wide CRISPR screen for entry of evolutionarily divergent serotype AAVrh32.33, we identified GPR108, a member of the G protein-coupled receptor superfamily, as an AAV entry factor. Of greater than 20 divergent AAVs across all AAV clades tested in human cell lines, only AAV5 transduction was unaffected in the GPR108 knockout (KO). GPR108 dependency was further shown in murine and primary cells in vitro. These findings are further validated in vivo, as the Gpr108 KO mouse demonstrates 10- to 100-fold reduced expression for AAV8 and rh32.33 but not AAV5. Mechanistically, both GPR108 N- and C-terminal domains are required for transduction, and on the capsid, a VP1 unique domain that is not conserved on AAV5 can be transferred to confer GPR108 independence onto AAV2 chimeras. In vitro binding and fractionation studies indicate reduced nuclear import and cytosolic accumulation in the absence of GPR108. We thus have identified the second of two AAV entry factors that is conserved between mice and humans relevant both in vitro and in vivo, further providing a mechanistic understanding to the tropism of AAV gene therapy vectors.
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Ehrenberg M, Pierce EA, Cox GF, Fulton AB. CRB1: one gene, many phenotypes. Semin Ophthalmol 2013;28(5-6):397-405.Abstract
Mutations in the CRB1 gene cause severe retinal degenerations, which may present as Leber congenital amaurosis, early onset retinal dystrophy, retinitis pigmentosa, or cone-rod dystrophy. Some clinical features should alert the ophthalmologist to the possibility of CRB1 disease. These features are nummular pigmentation of the retina, atrophic macula, retinal degeneration associated with Coats disease, and a unique form of retinitis pigmentosa named para-arteriolar preservation of the retinal pigment epithelium (PPRPE). Retinal degenerations associated with nanophthalmos and hyperopia, or with keratoconus, can serve as further clinical cues to mutations in CRB1. Despite this, no clear genotype-phenotype relationship has been established in CRB1 disease. In CRB1-disease, as in other inherited retinal degenerations (IRDs), it is essential to diagnose the specific disease-causing gene for the disease as genetic therapy has progressed considerably in the last few years and might be applicable.
Espinosa-Medina I, Garcia-Marques J, Cepko C, Lee T. High-throughput dense reconstruction of cell lineages. Open Biol 2019;9(12):190229.Abstract
The first meeting exclusively dedicated to the 'High-throughput dense reconstruction of cell lineages' took place at Janelia Research Campus (Howard Hughes Medical Institute) from 14 to 18 April 2019. Organized by Tzumin Lee, Connie Cepko, Jorge Garcia-Marques and Isabel Espinosa-Medina, this meeting echoed the recent eruption of new tools that allow the reconstruction of lineages based on the phylogenetic analysis of DNA mutations induced during development. Combined with single-cell RNA sequencing, these tools promise to solve the lineage of complex model organisms at single-cell resolution. Here, we compile the conference consensus on the technological and computational challenges emerging from the use of the new strategies, as well as potential solutions.
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Fan BJ, Pasquale LR, Kang JH, Levkovitch-Verbin H, Haines JL, Wiggs JL. Association of clusterin (CLU) variants and exfoliation syndrome: An analysis in two Caucasian studies and a meta-analysis. Exp Eye Res 2015;139:115-22.Abstract

Exfoliation syndrome (XFS) is an important risk factor for glaucoma (XFG) worldwide. LOXL1 variants are highly associated with XFS in most populations; however, the high frequency of risk alleles in normal individuals and the reversal of risk alleles in different ethnic populations suggest that other factors contribute to XFS pathogenesis. Clusterin (CLU) is an extracellular matrix chaperone that prevents protein aggregation and is highly expressed in ocular tissues affected by XFS. Studies examining common CLU variants for association with XFS have been inconsistent. The purpose of this study was to evaluate CLU variants for association with XFS in two independent datasets from the United States (222 cases and 344 controls) and Israel (92 cases and 102 controls). Seven tag SNPs that captured >95% of alleles at r(2) greater than 0.8 across the CLU genomic region were genotyped using TaqMan assays. Genotypes for an additional SNP, rs2279590, were imputed using phased haplotypes of HapMap reference CEU samples. Of the 8 CLU SNPs selected for the study, none were significantly associated with XFS in either case-control group (age and sex adjusted P > 0.14 and 0.36, respectively, in the US and Israeli datasets), or when they were meta-analyzed together (age and sex adjusted P > 0.13). Haplotype analysis using all 8 SNPs or only the promoter region SNPs also did not show significant associations of CLU with XFS in the combined US and Israeli dataset (P > 0.28). Meta-analysis of the data from this study and previous studies in Caucasian populations (1184 cases and 978 controls) resulted in statistically significant association of rs2279590 with XFS (summary OR = 1.18, 95% CI: 1.03-1.33, P = 0.01). Significant association between rs2279590 and XFS was also found in Indian populations (summary OR = 0.76, 95% CI: 0.61-0.96; P = 0.02); however, significant heterogeneity between the Caucasian and Indian populations possibly due to reversal of the risk allele precluded an overall meta-analysis for rs2279590 (Q = 0.001, I(2) = 91%). No significant association was identified for rs3087554 in either Caucasian populations (summary OR = 0.90, 95% CI: 0.77-1.05, P = 0.17) or Indian populations (summary OR = 0.89, 95% CI: 0.72-1.10, P = 0.28), or in both populations combined (1705 cases and 3713 controls; summary OR = 0.90, 95% CI: 0.79-1.01, P = 0.08). Significant heterogeneity precluded the addition of the Japanese data to the meta-analysis for rs3087554 (Q = 0.006, I(2) = 87%). Our results suggest that common CLU variants may contribute to modest XFS risk but even larger datasets are required to confirm these findings.

Farkas MH, Au ED, Sousa ME, Pierce EA. RNA-Seq: Improving Our Understanding of Retinal Biology and Disease. Cold Spring Harb Perspect Med 2015;Abstract

Over the past several years, rapid technological advances have allowed for a dramatic increase in our knowledge and understanding of the transcriptional landscape, because of the ability to study gene expression in greater depth and with more detail than previously possible. To this end, RNA-Seq has quickly become one of the most widely used methods for studying transcriptomes of tissues and individual cells. Unlike previously favored analysis methods, RNA-Seq is extremely high-throughput, and is not dependent on an annotated transcriptome, laying the foundation for novel genetic discovery. Additionally, RNA-Seq derived transcriptomes provide a basis for widening the scope of research to identify potential targets in the treatment of retinal disease.

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