Publications by authors named "John R Gilbert"

96 Publications

Three Brothers With Autism Carry a Stop-Gain Mutation in the HPA-Axis Gene NR3C2.

Autism Res 2020 04 17;13(4):523-531. Epub 2020 Feb 17.

John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, Florida.

Whole exome sequencing and copy-number variant analysis was performed on a family with three brothers diagnosed with autism. Each of the siblings shares an alteration in the nuclear receptor subfamily 3 group C member 2 (NR3C2) gene that is predicted to result in a stop-gain mutation (p.Q919X) in the mineralocorticoid receptor (MR) protein. This variant was maternally inherited and provides further evidence for a connection between the NR3C2 and autism. Interestingly, the NR3C2 gene encodes the MR protein, a steroid hormone-regulated transcription factor that acts in the hypothalamic-pituitary-adrenal axis and has been connected to stress and anxiety, both of which are features often seen in individuals with autism. Autism Res 2020, 13: 523-531. © 2020 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Given the complexity of the genetics underlying autism, each gene contributes to risk in a relatively small number of individuals, typically less than 1% of all autism cases. Whole exome sequencing of three brothers with autism identified a rare variant in the nuclear receptor subfamily 3 group C member 2 gene that is predicted to strongly interfere with its normal function. This gene encodes the mineralocorticoid receptor protein, which plays a role in how the body responds to stress and anxiety, features that are often elevated in people diagnosed with autism. This study adds further support to the relevance of this gene as a risk factor for autism.
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http://dx.doi.org/10.1002/aur.2269DOI Listing
April 2020

Exceptionally low likelihood of Alzheimer's dementia in APOE2 homozygotes from a 5,000-person neuropathological study.

Nat Commun 2020 02 3;11(1):667. Epub 2020 Feb 3.

Department of Epidemiology, University of Washington, 1959 NE Pacific Street, Seattle, WA, 98195, USA.

Each additional copy of the apolipoprotein E4 (APOE4) allele is associated with a higher risk of Alzheimer's dementia, while the APOE2 allele is associated with a lower risk of Alzheimer's dementia, it is not yet known whether APOE2 homozygotes have a particularly low risk. We generated Alzheimer's dementia odds ratios and other findings in more than 5,000 clinically characterized and neuropathologically characterized Alzheimer's dementia cases and controls. APOE2/2 was associated with a low Alzheimer's dementia odds ratios compared to APOE2/3 and 3/3, and an exceptionally low odds ratio compared to APOE4/4, and the impact of APOE2 and APOE4 gene dose was significantly greater in the neuropathologically confirmed group than in more than 24,000 neuropathologically unconfirmed cases and controls. Finding and targeting the factors by which APOE and its variants influence Alzheimer's disease could have a major impact on the understanding, treatment and prevention of the disease.
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http://dx.doi.org/10.1038/s41467-019-14279-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6997393PMC
February 2020

Time for Well-Powered Controlled Prospective Studies to Test a Causal Role for Herpes Viruses in Alzheimer's Disease Using Antiherpetic Drugs.

J Gerontol A Biol Sci Med Sci 2020 05;75(6):1058-1060

Leonard M. Miller School of Medicine, University of Miami, Florida.

Twenty-six phase III studies on Alzheimer's disease are ongoing or have been completed in 2018. Most of these studies are targeting amyloid-beta, its production, polymerization, and/or multiple interactions. None of the amyloid-beta studies seem to affect positively the clinical outcome of patients with Alzheimer's disease thus far, no matter the advancement of disease. It is time to consider other hypotheses for the pathogenesis of Alzheimer's disease, including the potential role of human herpes viruses (HHV), and especially HHV1 (herpes simplex virus type 1), HHV3 (varicella zoster virus), HHV6A, and HHV7. With this perspective, we review the scientific evidence and make the case for appropriately powered, prospective, randomized, and controlled studies using an anti-HHV drug, to establish a causal role for HHV in Alzheimer's disease.
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http://dx.doi.org/10.1093/gerona/glz150DOI Listing
May 2020

Genetic meta-analysis of diagnosed Alzheimer's disease identifies new risk loci and implicates Aβ, tau, immunity and lipid processing.

Nat Genet 2019 03 28;51(3):414-430. Epub 2019 Feb 28.

Research Center and Memory Clinic of Fundació ACE, Institut Català de Neurociències Aplicades-Universitat Internacional de Catalunya, Barcelona, Spain.

Risk for late-onset Alzheimer's disease (LOAD), the most prevalent dementia, is partially driven by genetics. To identify LOAD risk loci, we performed a large genome-wide association meta-analysis of clinically diagnosed LOAD (94,437 individuals). We confirm 20 previous LOAD risk loci and identify five new genome-wide loci (IQCK, ACE, ADAM10, ADAMTS1, and WWOX), two of which (ADAM10, ACE) were identified in a recent genome-wide association (GWAS)-by-familial-proxy of Alzheimer's or dementia. Fine-mapping of the human leukocyte antigen (HLA) region confirms the neurological and immune-mediated disease haplotype HLA-DR15 as a risk factor for LOAD. Pathway analysis implicates immunity, lipid metabolism, tau binding proteins, and amyloid precursor protein (APP) metabolism, showing that genetic variants affecting APP and Aβ processing are associated not only with early-onset autosomal dominant Alzheimer's disease but also with LOAD. Analyses of risk genes and pathways show enrichment for rare variants (P = 1.32 × 10), indicating that additional rare variants remain to be identified. We also identify important genetic correlations between LOAD and traits such as family history of dementia and education.
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http://dx.doi.org/10.1038/s41588-019-0358-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6463297PMC
March 2019

Identification of rare noncoding sequence variants in gamma-aminobutyric acid A receptor, alpha 4 subunit in autism spectrum disorder.

Neurogenetics 2018 01 18;19(1):17-26. Epub 2017 Nov 18.

John P. Hussman Institute for Human Genomics, Miller School of Medicine, University of Miami, Miami, FL, USA.

Alterations of the gamma-aminobutyric acid (GABA) signaling system has been strongly linked to the pathophysiology of autism spectrum disorder (ASD). Genetic associations of common variants in GABA receptor subunits, in particular GABRA4 on chromosome 4p12, with ASD have been replicated by several studies. Moreover, molecular investigations have identified altered transcriptional and translational levels of this gene and protein in brains of ASD individuals. Since the genotyped common variants are likely not the functional variants contributing to the molecular consequences or underlying ASD phenotype, this study aims to examine rare sequence variants in GABRA4, including those outside the protein coding regions of the gene. We comprehensively re-sequenced the entire protein coding and noncoding portions of the gene and putative regulatory sequences in 82 ASD individuals and 55 developmentally typical pediatric controls, all homozygous for the most significant previously associated ASD risk allele (G/G at rs1912960). We identified only a single common, coding variant, and no association of any single marker or set of variants with ASD. Functional annotation of noncoding variants identified several rare variants in putative regulatory sites. Finally, a rare variant unique to ASD cases, in an evolutionary conserved site of the 3'UTR, shows a trend toward decreasing gene expression. Hence, GABRA4 rare variants in noncoding DNA may be variants of modest physiological effects in ASD etiology.
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http://dx.doi.org/10.1007/s10048-017-0529-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5792317PMC
January 2018

Early-Onset Alzheimer Disease and Candidate Risk Genes Involved in Endolysosomal Transport.

JAMA Neurol 2017 09;74(9):1113-1122

John P. Hussman Institute for Human Genomics, Miller School of Medicine, University of Miami, Miami, Florida.

Importance: Mutations in APP, PSEN1, and PSEN2 lead to early-onset Alzheimer disease (EOAD) but account for only approximately 11% of EOAD overall, leaving most of the genetic risk for the most severe form of Alzheimer disease unexplained. This extreme phenotype likely harbors highly penetrant risk variants, making it primed for discovery of novel risk genes and pathways for AD.

Objective: To search for rare variants contributing to the risk for EOAD.

Design, Setting, And Participants: In this case-control study, whole-exome sequencing (WES) was performed in 51 non-Hispanic white (NHW) patients with EOAD (age at onset <65 years) and 19 Caribbean Hispanic families previously screened as negative for established APP, PSEN1, and PSEN2 causal variants. Participants were recruited from John P. Hussman Institute for Human Genomics, Case Western Reserve University, and Columbia University. Rare, deleterious, nonsynonymous, or loss-of-function variants were filtered to identify variants in known and suspected AD genes, variants in multiple unrelated NHW patients, variants present in 19 Hispanic EOAD WES families, and genes with variants in multiple unrelated NHW patients. These variants/genes were tested for association in an independent cohort of 1524 patients with EOAD, 7046 patients with late-onset AD (LOAD), and 7001 cognitively intact controls (age at examination, >65 years) from the Alzheimer's Disease Genetics Consortium. The study was conducted from January 21, 2013, to October 13, 2016.

Main Outcomes And Measures: Alzheimer disease diagnosed according to standard National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer Disease and Related Disorders Association criteria. Association between Alzheimer disease and genetic variants and genes was measured using logistic regression and sequence kernel association test-optimal gene tests, respectively.

Results: Of the 1524 NHW patients with EOAD, 765 (50.2%) were women and mean (SD) age was 60.0 (4.9) years; of the 7046 NHW patients with LOAD, 4171 (59.2%) were women and mean (SD) age was 77.4 (8.6) years; and of the 7001 NHW controls, 4215 (60.2%) were women and mean (SD) age was 77.4 (8.6) years. The gene PSD2, for which multiple unrelated NHW cases had rare missense variants, was significantly associated with EOAD (P = 2.05 × 10-6; Bonferroni-corrected P value [BP] = 1.3 × 10-3) and LOAD (P = 6.22 × 10-6; BP = 4.1 × 10-3). A missense variant in TCIRG1, present in a NHW patient and segregating in 3 cases of a Hispanic family, was more frequent in EOAD cases (odds ratio [OR], 2.13; 95% CI, 0.99-4.55; P = .06; BP = 0.413), and significantly associated with LOAD (OR, 2.23; 95% CI, 1.37-3.62; P = 7.2 × 10-4; BP = 5.0 × 10-3). A missense variant in the LOAD risk gene RIN3 showed suggestive evidence of association with EOAD after Bonferroni correction (OR, 4.56; 95% CI, 1.26-16.48; P = .02, BP = 0.091). In addition, a missense variant in RUFY1 identified in 2 NHW EOAD cases showed suggestive evidence of an association with EOAD as well (OR, 18.63; 95% CI, 1.62-213.45; P = .003; BP = 0.129).

Conclusions And Relevance: The genes PSD2, TCIRG1, RIN3, and RUFY1 all may be involved in endolysosomal transport-a process known to be important to development of AD. Furthermore, this study identified shared risk genes between EOAD and LOAD similar to previously reported genes, such as SORL1, PSEN2, and TREM2.
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http://dx.doi.org/10.1001/jamaneurol.2017.1518DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5691589PMC
September 2017

Rare coding variants in PLCG2, ABI3, and TREM2 implicate microglial-mediated innate immunity in Alzheimer's disease.

Nat Genet 2017 09 17;49(9):1373-1384. Epub 2017 Jul 17.

Boston University School of Medicine, Boston, Massachusetts, USA.

We identified rare coding variants associated with Alzheimer's disease in a three-stage case-control study of 85,133 subjects. In stage 1, we genotyped 34,174 samples using a whole-exome microarray. In stage 2, we tested associated variants (P < 1 × 10) in 35,962 independent samples using de novo genotyping and imputed genotypes. In stage 3, we used an additional 14,997 samples to test the most significant stage 2 associations (P < 5 × 10) using imputed genotypes. We observed three new genome-wide significant nonsynonymous variants associated with Alzheimer's disease: a protective variant in PLCG2 (rs72824905: p.Pro522Arg, P = 5.38 × 10, odds ratio (OR) = 0.68, minor allele frequency (MAF) = 0.0059, MAF = 0.0093), a risk variant in ABI3 (rs616338: p.Ser209Phe, P = 4.56 × 10, OR = 1.43, MAF = 0.011, MAF = 0.008), and a new genome-wide significant variant in TREM2 (rs143332484: p.Arg62His, P = 1.55 × 10, OR = 1.67, MAF = 0.0143, MAF = 0.0089), a known susceptibility gene for Alzheimer's disease. These protein-altering changes are in genes highly expressed in microglia and highlight an immune-related protein-protein interaction network enriched for previously identified risk genes in Alzheimer's disease. These genetic findings provide additional evidence that the microglia-mediated innate immune response contributes directly to the development of Alzheimer's disease.
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http://dx.doi.org/10.1038/ng.3916DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5669039PMC
September 2017

Novel approach for independent control of brain hypothermia and systemic normothermia: cerebral selective deep hypothermia for refractory cardiac arrest.

J Neurointerv Surg 2017 Aug 25;9(8):e32. Epub 2017 Jan 25.

Department of Cardiovascular Surgery, National Taiwan University Hospital, Taipei, Taiwan.

A 38-year-old man was found unconscious, alone in the driver's seat of his car. The emergency medical team identified his condition as pulseless ventricular tachycardia. Defibrillation was attempted but failed. Extracorporeal membrane oxygenation (ECMO) was started in the emergency room 52 min after the estimated arrest following the extracorporeal cardiopulmonary resuscitation (ECPR) protocol in our center. The initial prognosis under the standard protocol was <25% chance of survival. A novel adjunctive to our ECPR protocol, cerebral selective deep (<30°C) hypothermia (CSDH), was applied. CSDH adds a second independent femoral access extracorporeal circuit, perfusing cold blood into the patient's common carotid artery. The ECMO and CSDH circuits demonstrated independent control of cerebral and core temperatures. Nasal temperature was lowered to below 30°C for 12 hours while core was maintained at normothermia. The patient was discharged without significant neurological deficit 32 days after the initial arrest.
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http://dx.doi.org/10.1136/neurintsurg-2016-012806.repDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5583700PMC
August 2017

Novel approach for independent control of brain hypothermia and systemic normothermia: cerebral selective deep hypothermia for refractory cardiac arrest.

BMJ Case Rep 2017 Jan 20;2017. Epub 2017 Jan 20.

Department of Cardiovascular Surgery, National Taiwan University Hospital, Taipei, Taiwan.

A 38-year-old man was found unconscious, alone in the driver's seat of his car. The emergency medical team identified his condition as pulseless ventricular tachycardia. Defibrillation was attempted but failed. Extracorporeal membrane oxygenation (ECMO) was started in the emergency room 52 min after the estimated arrest following the extracorporeal cardiopulmonary resuscitation (ECPR) protocol in our center. The initial prognosis under the standard protocol was <25% chance of survival. A novel adjunctive to our ECPR protocol, cerebral selective deep (<30°C) hypothermia (CSDH), was applied. CSDH adds a second independent femoral access extracorporeal circuit, perfusing cold blood into the patient's common carotid artery. The ECMO and CSDH circuits demonstrated independent control of cerebral and core temperatures. Nasal temperature was lowered to below 30°C for 12 hours while core was maintained at normothermia. The patient was discharged without significant neurological deficit 32 days after the initial arrest.
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http://dx.doi.org/10.1136/bcr-2016-012806DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5256511PMC
January 2017

ABCA7 frameshift deletion associated with Alzheimer disease in African Americans.

Neurol Genet 2016 Jun 17;2(3):e79. Epub 2016 May 17.

John P. Hussman Institute for Human Genomics (H.N.C., B.W.K., S.R., K.L.H.-N., M.A.K., P.L.W., D.V.B., D.M.D., M.L.C., J.M.V., J.R.G., G.W.B., E.R.M., R.M.C., M.A.P.-V.), Department of Neurology (H.N.C., J.M.V., M.A.P.-V.), Dr. John T. Macdonald Foundation Department of Human Genetics (D.M.D., M.L.C., J.M.V., J.R.G., G.W.B., E.R.M., R.M.C.), Miller School of Medicine, University of Miami, FL; The Taub Institute for Research on Alzheimer's Disease and the Aging Brain (B.N.V., R.M.), Gertrude H. Sergievsky Center, Departments of Neurology, Psychiatry, and Epidemiology, College of Physicians and Surgeons, Columbia University, New York, NY; Department of Pathology and Laboratory Medicine (B.A.D., G.D.S.), University of Pennsylvania Perelman School of Medicine, Philadelphia, PA; Department of Biology (R.L., G.S.B., M.A.P.-V.), North Carolina A&T State University, Greensboro, NC; Departments of Medicine, Neurology, Ophthalmology, Genetics & Genomics, Epidemiology, and Biostatistics (L.A.F.), Boston University, MA; and Department of Epidemiology and Biostatistics (J.L.H.), Institute for Computational Biology, Case Western Reserve University School of Medicine, Cleveland, OH.

Objective: To identify a causative variant(s) that may contribute to Alzheimer disease (AD) in African Americans (AA) in the ATP-binding cassette, subfamily A (ABC1), member 7 (ABCA7) gene, a known risk factor for late-onset AD.

Methods: Custom capture sequencing was performed on ∼150 kb encompassing ABCA7 in 40 AA cases and 37 AA controls carrying the AA risk allele (rs115550680). Association testing was performed for an ABCA7 deletion identified in large AA data sets (discovery n = 1,068; replication n = 1,749) and whole exome sequencing of Caribbean Hispanic (CH) AD families.

Results: A 44-base pair deletion (rs142076058) was identified in all 77 risk genotype carriers, which shows that the deletion is in high linkage disequilibrium with the risk allele. The deletion was assessed in a large data set (531 cases and 527 controls) and, after adjustments for age, sex, and APOE status, was significantly associated with disease (p = 0.0002, odds ratio [OR] = 2.13 [95% confidence interval (CI): 1.42-3.20]). An independent data set replicated the association (447 cases and 880 controls, p = 0.0117, OR = 1.65 [95% CI: 1.12-2.44]), and joint analysis increased the significance (p = 1.414 × 10(-5), OR = 1.81 [95% CI: 1.38-2.37]). The deletion is common in AA cases (15.2%) and AA controls (9.74%), but in only 0.12% of our non-Hispanic white cohort. Whole exome sequencing of multiplex, CH families identified the deletion cosegregating with disease in a large sibship. The deleted allele produces a stable, detectable RNA strand and is predicted to result in a frameshift mutation (p.Arg578Alafs) that could interfere with protein function.

Conclusions: This common ABCA7 deletion could represent an ethnic-specific pathogenic alteration in AD.
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http://dx.doi.org/10.1212/NXG.0000000000000079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4871806PMC
June 2016

Segregation of a rare TTC3 variant in an extended family with late-onset Alzheimer disease.

Neurol Genet 2016 Feb 14;2(1):e41. Epub 2016 Jan 14.

John P. Hussman Institute for Human Genomics (M.A.K., H.N.C., K.L.H.-N., S.R., B.W.K., P.L.W., S.L.Z., E.R.M., G.W.B., J.M.V., M.L.C., J.R.G., R.M.C., M.A.P.-V.), Department of Neurology (H.N.C., S.L.Z., J.M.V., M.A.P.-V.), and Dr. John T. Macdonald Foundation Department of Human Genetics (S.L.Z., E.R.M., G.W.B., J.M.V., M.L.C., J.R.G., M.A.P.-V.), University of Miami, Miller School of Medicine, Miami, FL; Departments of Medicine, Neurology, Ophthalmology, Genetics & Genomics, Epidemiology, and Biostatistics (L.A.F.), Boston University, Boston, MA; Department of Epidemiology and Biostatistics (J.L.H.), Institute for Computational Biology, Case Western Reserve University School of Medicine, Cleveland, OH; and Department of Pathology and Laboratory Medicine (G.D.S.), University of Pennsylvania School of Medicine, Philadelphia, PA.

Objective: The genetic risk architecture of Alzheimer disease (AD) is complex with single pathogenic mutations leading to early-onset AD, while both rare and common genetic susceptibility variants contribute to the more widespread late-onset AD (LOAD); we sought to discover novel genes contributing to LOAD risk.

Methods: Whole-exome sequencing and genome-wide genotyping were performed on 11 affected individuals in an extended family with an apparent autosomal dominant pattern of LOAD. Variants of interest were then evaluated in a large cohort of LOAD cases and aged controls.

Results: We detected a single rare, nonsynonymous variant shared in all 11 LOAD individuals, a missense change in the tetratricopeptide repeat domain 3 (TTC3) gene. The missense variant, rs377155188 (p.S1038C), is predicted to be damaging. Affecteds-only multipoint linkage analysis demonstrated that this region of TTC3 has a LOD score of 2.66 in this family.

Conclusion: The TTC3 p.S1038C substitution may represent a segregating, rare LOAD risk variant. Previous studies have shown that TTC3 expression is consistently reduced in LOAD patients and negatively correlated with AD neuropathology and that TTC3 is a regulator of Akt signaling, a key pathway disrupted in LOAD. This study demonstrates how utilizing whole-exome sequencing in a large, multigenerational family with a high incidence of LOAD could reveal a novel candidate gene.
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http://dx.doi.org/10.1212/NXG.0000000000000041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4817909PMC
February 2016

Linkage of familial essential tremor to chromosome 5q35.

Mov Disord 2016 07 26;31(7):1059-62. Epub 2016 Feb 26.

John P. Hussman Institute for Human Genomics, Miller School of Medicine, University of Miami, Miami, Florida, USA.

Background: Essential tremor is a neurological condition characterized by tremor during voluntary movement. To date, 3 loci linked to familial essential tremor have been identified.

Methods: We examined 48 essential tremor patients in 5 large essential tremor pedigrees in our data set for genetic linkage using an Affymetrix Axiom array. Linkage analysis was performed using an affecteds-only dominant model in SIMWALK2. To incorporate all genotype information, GERMLINE was used to identify genome segments shared identical-by-descent in pairs of affecteds. Exome sequencing was performed in pedigrees showing evidence of linkage.

Results: For one family, chromosomes 5 and 18 showed genome-wide significant linkage to essential tremor. Shared segment analysis excluded the 18p11 candidate region and reduced the 5q35 region by 1 megabase. Exome sequencing did not identify a potential causative variant in this region.

Conclusion: A locus on chromosome 5 is linked to essential tremor. Further research is needed to identify a causative variant. © 2016 International Parkinson and Movement Disorder Society.
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http://dx.doi.org/10.1002/mds.26582DOI Listing
July 2016

Targeted massively parallel sequencing of autism spectrum disorder-associated genes in a case control cohort reveals rare loss-of-function risk variants.

Mol Autism 2015 7;6:43. Epub 2015 Jul 7.

John P. Hussman Institute for Human Genomics, Miller School of Medicine, University of Miami, Miami, FL 33136 USA ; Dr. John T. Macdonald Foundation Department of Human Genetics, Miller School of Medicine, University of Miami, Miami, FL 33136 USA.

Background: Autism spectrum disorder (ASD) is highly heritable, yet genome-wide association studies (GWAS), copy number variation screens, and candidate gene association studies have found no single factor accounting for a large percentage of genetic risk. ASD trio exome sequencing studies have revealed genes with recurrent de novo loss-of-function variants as strong risk factors, but there are relatively few recurrently affected genes while as many as 1000 genes are predicted to play a role. As such, it is critical to identify the remaining rare and low-frequency variants contributing to ASD.

Methods: We have utilized an approach of prioritization of genes by GWAS and follow-up with massively parallel sequencing in a case-control cohort. Using a previously reported ASD noise reduction GWAS analyses, we prioritized 837 RefSeq genes for custom targeting and sequencing. We sequenced the coding regions of those genes in 2071 ASD cases and 904 controls of European white ancestry. We applied comprehensive annotation to identify single variants which could confer ASD risk and also gene-based association analysis to identify sets of rare variants associated with ASD.

Results: We identified a significant over-representation of rare loss-of-function variants in genes previously associated with ASD, including a de novo premature stop variant in the well-established ASD candidate gene RBFOX1. Furthermore, ASD cases were more likely to have two damaging missense variants in candidate genes than controls. Finally, gene-based rare variant association implicates genes functioning in excitatory neurotransmission and neurite outgrowth and guidance pathways including CACNAD2, KCNH7, and NRXN1.

Conclusions: We find suggestive evidence that rare variants in synaptic genes are associated with ASD and that loss-of-function mutations in ASD candidate genes are a major risk factor, and we implicate damaging mutations in glutamate signaling receptors and neuronal adhesion and guidance molecules. Furthermore, the role of de novo mutations in ASD remains to be fully investigated as we identified the first reported protein-truncating variant in RBFOX1 in ASD. Overall, this work, combined with others in the field, suggests a convergence of genes and molecular pathways underlying ASD etiology.
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http://dx.doi.org/10.1186/s13229-015-0034-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4504419PMC
July 2015

Two knockdown models of the autism genes SYNGAP1 and SHANK3 in zebrafish produce similar behavioral phenotypes associated with embryonic disruptions of brain morphogenesis.

Hum Mol Genet 2015 Jul 16;24(14):4006-23. Epub 2015 Apr 16.

Department of Biology, University of Miami, Coral Gables, FL, USA,

Despite significant progress in the genetics of autism spectrum disorder (ASD), how genetic mutations translate to the behavioral changes characteristic of ASD remains largely unknown. ASD affects 1-2% of children and adults, and is characterized by deficits in verbal and non-verbal communication, and social interactions, as well as the presence of repetitive behaviors and/or stereotyped interests. ASD is clinically and etiologically heterogeneous, with a strong genetic component. Here, we present functional data from syngap1 and shank3 zebrafish loss-of-function models of ASD. SYNGAP1, a synaptic Ras GTPase activating protein, and SHANK3, a synaptic scaffolding protein, were chosen because of mounting evidence that haploinsufficiency in these genes is highly penetrant for ASD and intellectual disability (ID). Orthologs of both SYNGAP1 and SHANK3 are duplicated in the zebrafish genome and we find that all four transcripts (syngap1a, syngap1b, shank3a and shank3b) are expressed at the earliest stages of nervous system development with pronounced expression in the larval brain. Consistent with early expression of these genes, knockdown of syngap1b or shank3a cause common embryonic phenotypes including delayed mid- and hindbrain development, disruptions in motor behaviors that manifest as unproductive swim attempts, and spontaneous, seizure-like behaviors. Our findings indicate that both syngap1b and shank3a play novel roles in morphogenesis resulting in common brain and behavioral phenotypes.
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http://dx.doi.org/10.1093/hmg/ddv138DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4476447PMC
July 2015

Rarity of the Alzheimer disease-protective APP A673T variant in the United States.

JAMA Neurol 2015 Feb;72(2):209-16

Department of Medical and Molecular Genetics, Indiana University, Indianapolis.

Importance: Recently, a rare variant in the amyloid precursor protein gene (APP) was described in a population from Iceland. This variant, in which alanine is replaced by threonine at position 673 (A673T), appears to protect against late-onset Alzheimer disease (AD). We evaluated the frequency of this variant in AD cases and cognitively normal controls to determine whether this variant will significantly contribute to risk assessment in individuals in the United States.

Objective: To determine the frequency of the APP A673T variant in a large group of elderly cognitively normal controls and AD cases from the United States and in 2 case-control cohorts from Sweden.

Design, Setting, And Participants: Case-control association analysis of variant APP A673T in US and Swedish white individuals comparing AD cases with cognitively intact elderly controls. Participants were ascertained at multiple university-associated medical centers and clinics across the United States and Sweden by study-specific sampling methods. They were from case-control studies, community-based prospective cohort studies, and studies that ascertained multiplex families from multiple sources.

Main Outcomes And Measures: Genotypes for the APP A673T variant were determined using the Infinium HumanExome V1 Beadchip (Illumina, Inc) and by TaqMan genotyping (Life Technologies).

Results: The A673T variant genotypes were evaluated in 8943 US AD cases, 10 480 US cognitively normal controls, 862 Swedish AD cases, and 707 Swedish cognitively normal controls. We identified 3 US individuals heterozygous for A673T, including 1 AD case (age at onset, 89 years) and 2 controls (age at last examination, 82 and 77 years). The remaining US samples were homozygous for the alanine (A673) allele. In the Swedish samples, 3 controls were heterozygous for A673T and all AD cases were homozygous for the A673 allele. We also genotyped a US family previously reported to harbor the A673T variant and found a mother-daughter pair, both cognitively normal at ages 72 and 84 years, respectively, who were both heterozygous for A673T; however, all individuals with AD in the family were homozygous for A673.

Conclusions And Relevance: The A673T variant is extremely rare in US cohorts and does not play a substantial role in risk for AD in this population. This variant may be primarily restricted to Icelandic and Scandinavian populations.
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http://dx.doi.org/10.1001/jamaneurol.2014.2157DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4324097PMC
February 2015

Effects of multiple genetic loci on age at onset in late-onset Alzheimer disease: a genome-wide association study.

JAMA Neurol 2014 Nov;71(11):1394-404

Department of Neuroscience, Mount Sinai School of Medicine, New York, New York32Department of Psychiatry, Mount Sinai School of Medicine, New York, New York33Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York.

Importance: Because APOE locus variants contribute to risk of late-onset Alzheimer disease (LOAD) and to differences in age at onset (AAO), it is important to know whether other established LOAD risk loci also affect AAO in affected participants.

Objectives: To investigate the effects of known Alzheimer disease risk loci in modifying AAO and to estimate their cumulative effect on AAO variation using data from genome-wide association studies in the Alzheimer Disease Genetics Consortium.

Design, Setting, And Participants: The Alzheimer Disease Genetics Consortium comprises 14 case-control, prospective, and family-based data sets with data on 9162 participants of white race/ethnicity with Alzheimer disease occurring after age 60 years who also had complete AAO information, gathered between 1989 and 2011 at multiple sites by participating studies. Data on genotyped or imputed single-nucleotide polymorphisms most significantly associated with risk at 10 confirmed LOAD loci were examined in linear modeling of AAO, and individual data set results were combined using a random-effects, inverse variance-weighted meta-analysis approach to determine whether they contribute to variation in AAO. Aggregate effects of all risk loci on AAO were examined in a burden analysis using genotype scores weighted by risk effect sizes.

Main Outcomes And Measures: Age at disease onset abstracted from medical records among participants with LOAD diagnosed per standard criteria.

Results: Analysis confirmed the association of APOE with earlier AAO (P = 3.3 × 10(-96)), with associations in CR1 (rs6701713, P = 7.2 × 10(-4)), BIN1 (rs7561528, P = 4.8 × 10(-4)), and PICALM (rs561655, P = 2.2 × 10(-3)) reaching statistical significance (P < .005). Risk alleles individually reduced AAO by 3 to 6 months. Burden analyses demonstrated that APOE contributes to 3.7% of the variation in AAO (R(2) = 0.256) over baseline (R(2) = 0.221), whereas the other 9 loci together contribute to 2.2% of the variation (R(2) = 0.242).

Conclusions And Relevance: We confirmed an association of APOE (OMIM 107741) variants with AAO among affected participants with LOAD and observed novel associations of CR1 (OMIM 120620), BIN1 (OMIM 601248), and PICALM (OMIM 603025) with AAO. In contrast to earlier hypothetical modeling, we show that the combined effects of Alzheimer disease risk variants on AAO are on the scale of, but do not exceed, the APOE effect. While the aggregate effects of risk loci on AAO may be significant, additional genetic contributions to AAO are individually likely to be small.
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http://dx.doi.org/10.1001/jamaneurol.2014.1491DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4314944PMC
November 2014

Genome-wide association meta-analysis of neuropathologic features of Alzheimer's disease and related dementias.

PLoS Genet 2014 Sep 4;10(9):e1004606. Epub 2014 Sep 4.

Department of Neurology, Taub Institute for Research on Alzheimer's Disease and the Aging Brain, Columbia University, New York, New York, United States of America.

Alzheimer's disease (AD) and related dementias are a major public health challenge and present a therapeutic imperative for which we need additional insight into molecular pathogenesis. We performed a genome-wide association study and analysis of known genetic risk loci for AD dementia using neuropathologic data from 4,914 brain autopsies. Neuropathologic data were used to define clinico-pathologic AD dementia or controls, assess core neuropathologic features of AD (neuritic plaques, NPs; neurofibrillary tangles, NFTs), and evaluate commonly co-morbid neuropathologic changes: cerebral amyloid angiopathy (CAA), Lewy body disease (LBD), hippocampal sclerosis of the elderly (HS), and vascular brain injury (VBI). Genome-wide significance was observed for clinico-pathologic AD dementia, NPs, NFTs, CAA, and LBD with a number of variants in and around the apolipoprotein E gene (APOE). GalNAc transferase 7 (GALNT7), ATP-Binding Cassette, Sub-Family G (WHITE), Member 1 (ABCG1), and an intergenic region on chromosome 9 were associated with NP score; and Potassium Large Conductance Calcium-Activated Channel, Subfamily M, Beta Member 2 (KCNMB2) was strongly associated with HS. Twelve of the 21 non-APOE genetic risk loci for clinically-defined AD dementia were confirmed in our clinico-pathologic sample: CR1, BIN1, CLU, MS4A6A, PICALM, ABCA7, CD33, PTK2B, SORL1, MEF2C, ZCWPW1, and CASS4 with 9 of these 12 loci showing larger odds ratio in the clinico-pathologic sample. Correlation of effect sizes for risk of AD dementia with effect size for NFTs or NPs showed positive correlation, while those for risk of VBI showed a moderate negative correlation. The other co-morbid neuropathologic features showed only nominal association with the known AD loci. Our results discovered new genetic associations with specific neuropathologic features and aligned known genetic risk for AD dementia with specific neuropathologic changes in the largest brain autopsy study of AD and related dementias.
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http://dx.doi.org/10.1371/journal.pgen.1004606DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4154667PMC
September 2014

Exome sequencing of extended families with autism reveals genes shared across neurodevelopmental and neuropsychiatric disorders.

Mol Autism 2014 Jan 10;5(1). Epub 2014 Jan 10.

John P, Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, 1501 NW 10th Avenue, BRB-314 (M860), Miami, FL, USA.

Background: Autism spectrum disorders (ASDs) comprise a range of neurodevelopmental conditions of varying severity, characterized by marked qualitative difficulties in social relatedness, communication, and behavior. Despite overwhelming evidence of high heritability, results from genetic studies to date show that ASD etiology is extremely heterogeneous and only a fraction of autism genes have been discovered.

Methods: To help unravel this genetic complexity, we performed whole exome sequencing on 100 ASD individuals from 40 families with multiple distantly related affected individuals. All families contained a minimum of one pair of ASD cousins. Each individual was captured with the Agilent SureSelect Human All Exon kit, sequenced on the Illumina Hiseq 2000, and the resulting data processed and annotated with Burrows-Wheeler Aligner (BWA), Genome Analysis Toolkit (GATK), and SeattleSeq. Genotyping information on each family was utilized in order to determine genomic regions that were identical by descent (IBD). Variants identified by exome sequencing which occurred in IBD regions and present in all affected individuals within each family were then evaluated to determine which may potentially be disease related. Nucleotide alterations that were novel and rare (minor allele frequency, MAF, less than 0.05) and predicted to be detrimental, either by altering amino acids or splicing patterns, were prioritized.

Results: We identified numerous potentially damaging, ASD associated risk variants in genes previously unrelated to autism. A subset of these genes has been implicated in other neurobehavioral disorders including depression (SLIT3), epilepsy (CLCN2, PRICKLE1), intellectual disability (AP4M1), schizophrenia (WDR60), and Tourette syndrome (OFCC1). Additional alterations were found in previously reported autism candidate genes, including three genes with alterations in multiple families (CEP290, CSMD1, FAT1, and STXBP5). Compiling a list of ASD candidate genes from the literature, we determined that variants occurred in ASD candidate genes 1.65 times more frequently than in random genes captured by exome sequencing (P = 8.55 × 10-5).

Conclusions: By studying these unique pedigrees, we have identified novel DNA variations related to ASD, demonstrated that exome sequencing in extended families is a powerful tool for ASD candidate gene discovery, and provided further evidence of an underlying genetic component to a wide range of neurodevelopmental and neuropsychiatric diseases.
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http://dx.doi.org/10.1186/2040-2392-5-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3896704PMC
January 2014

KIAA1462, a coronary artery disease associated gene, is a candidate gene for late onset Alzheimer disease in APOE carriers.

PLoS One 2013 12;8(12):e82194. Epub 2013 Dec 12.

Center for Human Genetics Research and Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, United States of America.

Alzheimer disease (AD) is a devastating neurodegenerative disease affecting more than five million Americans. In this study, we have used updated genetic linkage data from chromosome 10 in combination with expression data from serial analysis of gene expression to choose a new set of thirteen candidate genes for genetic analysis in late onset Alzheimer disease (LOAD). Results in this study identify the KIAA1462 locus as a candidate locus for LOAD in APOE4 carriers. Two genes exist at this locus, KIAA1462, a gene associated with coronary artery disease, and "rokimi", encoding an untranslated spliced RNA The genetic architecture at this locus suggests that the gene product important in this association is either "rokimi", or a different isoform of KIAA1462 than the isoform that is important in cardiovascular disease. Expression data suggests that isoform f of KIAA1462 is a more attractive candidate for association with LOAD in APOE4 carriers than "rokimi" which had no detectable expression in brain.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082194PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3861372PMC
October 2014

C9ORF72 intermediate repeat copies are a significant risk factor for Parkinson disease.

Ann Hum Genet 2013 Sep 12;77(5):351-63. Epub 2013 Jul 12.

University of Miami, Miller School of Medicine, John P. Hussman Institute for Human Genomics, Biomedical Research building, 1501 NW 10th Ave, Miami, FL, 33136, USA.

We set out to determine whether expansions in the C9ORF72 repeat found in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) families are associated with Parkinson disease (PD). We determined the repeat size in a total of 889 clinically ascertained patients (including PD and essential tremor plus Parkinsonism (ETP)) and 1144 controls using a repeat-primed PCR assay. We found that large C9ORF72 repeat expansions (>30 repeats) were not contributing to PD risk. However, PD and ETP cases had a significant increase in intermediate (>20 to 30+) repeat copies compared to controls. Overall, 14 cases (13 PD, 1 ETP) and three controls had >20 repeat copies (Fisher's exact test p = 0.002). Further, seven cases and no controls had >23 repeat copies (p = 0.003). Our results suggest that intermediate copy numbers of the C9ORF72 repeat contribute to risk for PD and ETP. This also suggests that PD, ALS and FTD share some pathophysiological mechanisms of disease. Further studies are needed to elucidate the contribution of the C9ORF72 repeat in the overall PD population and to determine whether other common genetic risk factors exist between these neurodegenerative disorders.
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http://dx.doi.org/10.1111/ahg.12033DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3815478PMC
September 2013

Parkinsonism and distinct dementia patterns in a family with the MAPT R406W mutation.

Alzheimers Dement 2014 May 30;10(3):360-5. Epub 2013 May 30.

University of Miami, Miller School of Medicine, John P. Hussman Institute for Human Genomics, Miami, FL, USA; University of Miami, Miller School of Medicine, Dr. John T. Macdonald Foundation Department of Human Genetics, Miami, FL, USA. Electronic address:

Background: The Arg406Trp (R406W) missense mutation in the microtubule-associated protein-tau gene (MAPT) is a known cause of early-onset dementia. Various dementia phenotypes have been described, including frontotemporal dementia (FTD), FTD with parkinsonism, and early-onset Alzheimer disease (EOAD)-like presentations.

Methods: Using whole-exome capture with subsequent sequencing, we identified the R406W mutation in a family with multiple individuals with clinically diagnosed EOAD, in a pattern suggesting autosomal dominant inheritance. We reevaluated all available family members clinically.

Results: Each of the affected individuals had a course meeting clinical criteria for EOAD. Two distinct disease trajectories were apparent: one rapidly progressive, and the other long and gradual. Four of five affected individuals also manifested parkinsonian symptoms. FTD features were not prominent and, when present, appeared only late in the course of dementia.

Conclusions: The MAPT R406W mutation is associated with EOAD-like symptoms and parkinsonism without FTD, as well as distinct cognitive courses.
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http://dx.doi.org/10.1016/j.jalz.2013.02.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3762928PMC
May 2014

Evaluating mitochondrial DNA variation in autism spectrum disorders.

Ann Hum Genet 2013 Jan 6;77(1):9-21. Epub 2012 Nov 6.

John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, FL 33136, USA.

Despite the increasing speculation that oxidative stress and abnormal energy metabolism may play a role in Autism Spectrum Disorders (ASD), and the observation that patients with mitochondrial defects have symptoms consistent with ASD, there are no comprehensive published studies examining the role of mitochondrial variation in autism. Therefore, we have sought to comprehensively examine the role of mitochondrial DNA (mtDNA) variation with regard to ASD risk, employing a multi-phase approach. In phase 1 of our experiment, we examined 132 mtDNA single-nucleotide polymorphisms (SNPs) genotyped as part of our genome-wide association studies of ASD. In phase 2 we genotyped the major European mitochondrial haplogroup-defining variants within an expanded set of autism probands and controls. Finally in phase 3, we resequenced the entire mtDNA in a subset of our Caucasian samples (∼400 proband-father pairs). In each phase we tested whether mitochondrial variation showed evidence of association to ASD. Despite a thorough interrogation of mtDNA variation, we found no evidence to suggest a major role for mtDNA variation in ASD susceptibility. Accordingly, while there may be attractive biological hints suggesting the role of mitochondria in ASD our data indicate that mtDNA variation is not a major contributing factor to the development of ASD.
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http://dx.doi.org/10.1111/j.1469-1809.2012.00736.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3535511PMC
January 2013

The expanding role of MBD genes in autism: identification of a MECP2 duplication and novel alterations in MBD5, MBD6, and SETDB1.

Autism Res 2012 Dec 10;5(6):385-97. Epub 2012 Oct 10.

John P. Hussman Institute for Human Genomics, University of Miami, Miller School of Medicine, Miami, FL 33136, USA.

The methyl-CpG-binding domain (MBD) gene family was first linked to autism over a decade ago when Rett syndrome, which falls under the umbrella of autism spectrum disorders (ASDs), was revealed to be predominantly caused by MECP2 mutations. Since that time, MECP2 alterations have been recognized in idiopathic ASD patients by us and others. Individuals with deletions across the MBD5 gene also present with ASDs, impaired speech, intellectual difficulties, repetitive behaviors, and epilepsy. These findings suggest that further investigations of the MBD gene family may reveal additional associations related to autism. We now describe the first study evaluating individuals with ASD for rare variants in four autosomal MBD family members, MBD5, MBD6, SETDB1, and SETDB2, and expand our initial screening in the MECP2 gene. Each gene was sequenced over all coding exons and evaluated for copy number variations in 287 patients with ASD and an equal number of ethnically matched control individuals. We identified 186 alterations through sequencing, approximately half of which were novel (96 variants, 51.6%). We identified 17 ASD specific, nonsynonymous variants, four of which were concordant in multiplex families: MBD5 Tyr1269Cys, MBD6 Arg883Trp, MECP2 Thr240Ser, and SETDB1 Pro1067del. Furthermore, a complex duplication spanning of the MECP2 gene was identified in two brothers who presented with developmental delay and intellectual disability. From our studies, we provide the first examples of autistic patients carrying potentially detrimental alterations in MBD6 and SETDB1, thereby demonstrating that the MBD gene family potentially plays a significant role in rare and private genetic causes of autism.
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http://dx.doi.org/10.1002/aur.1251DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3528798PMC
December 2012

Genome-wide association and linkage study in the Amish detects a novel candidate late-onset Alzheimer disease gene.

Ann Hum Genet 2012 Sep;76(5):342-51

Center for Human Genetics Research, Vanderbilt University Medical Center, Nashville, TN, USA.

To identify novel late-onset Alzheimer disease (LOAD) risk genes, we have analysed Amish populations of Ohio and Indiana. We performed genome-wide SNP linkage and association studies on 798 individuals (109 with LOAD). We tested association using the Modified Quasi-Likelihood Score test and also performed two-point and multipoint linkage analyses. We found that LOAD was significantly associated with APOE (P= 9.0 × 10-6) in all our ascertainment regions except for the Adams County, Indiana, community (P= 0.55). Genome-wide, the most strongly associated SNP was rs12361953 (P= 7.92 × 10-7). A very strong, genome-wide significant multipoint peak [recessive heterogeneity multipoint LOD (HLOD) = 6.14, dominant HLOD = 6.05] was detected on 2p12. Three additional loci with multipoint HLOD scores >3 were detected on 3q26, 9q31 and 18p11. Converging linkage and association results, the most significantly associated SNP under the 2p12 peak was at rs2974151 (P= 1.29 × 10-4). This SNP is located in CTNNA2, which encodes catenin alpha 2, a neuronal-specific catenin known to have function in the developing brain. These results identify CTNNA2 as a novel candidate LOAD gene, and implicate three other regions of the genome as novel LOAD loci. These results underscore the utility of using family-based linkage and association analyses in isolated populations to identify novel loci for traits with complex genetic architecture.
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http://dx.doi.org/10.1111/j.1469-1809.2012.00721.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3419486PMC
September 2012

Transcriptome profiling of genes involved in neural tube closure during human embryonic development using long serial analysis of gene expression (long-SAGE).

Birth Defects Res A Clin Mol Teratol 2012 Sep 18;94(9):683-92. Epub 2012 Jul 18.

Center for Human Genetics, Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.

Background: Neural tube defects (NTDs) are common human birth defects with a complex etiology. To develop a comprehensive knowledge of the genes expressed during normal neurulation, we established transcriptomes from human neural tube fragments during and after neurulation using long Serial Analysis of Gene Expression (long-SAGE).

Methods: Rostral and caudal neural tubes were dissected from normal human embryos aged between 26 and 32 days of gestation. Tissues from the same region and Carnegie stage were pooled (n ≥ 4) and total RNA extracted to construct four long-SAGE libraries. Tags were mapped using the UniGene Homo sapiens 17 bp tag-to-gene best mapping set. Differentially expressed genes were identified by chi-square or Fisher's exact test, and validation was performed for a subset of those transcripts using in situ hybridization. In silico analyses were performed with BinGO and EXPANDER.

Results: We observed most genes to be similarly regulated in rostral and caudal regions, but expression profiles differed during and after closure. In silico analysis found similar enrichments in both regions for biologic process terms, transcription factor binding and miRNA target motifs. Twelve genes potentially expressing alternate isoforms by region or developmental stage, and the microRNAs miR-339-5p, miR-141/200a, miR-23ab, and miR-129/129-5p are among several potential candidates identified here for future research.

Conclusions: Time appears to influence gene expression in the developing central nervous system more than location. These data provide a novel complement to traditional strategies of identifying genes associated with human NTDs and offer unique insight into the genes associated with normal human neurulation.
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http://dx.doi.org/10.1002/bdra.23040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3438356PMC
September 2012

Linkage and association of successful aging to the 6q25 region in large Amish kindreds.

Age (Dordr) 2013 Aug 7;35(4):1467-77. Epub 2012 Jul 7.

Dr. John T. Macdonald Foundation Department of Human Genetics and John P. Hussman Institute of Human Genomics, Miller School of Medicine, University of Miami, 1501 NW 10th Avenue, Room 414, Miami, FL 33136, USA.

Successful aging (SA) is a multidimensional phenotype involving living to older age with high physical function, preserved cognition, and continued social engagement. Several domains underlying SA are heritable, and identifying health-promoting polymorphisms and their interactions with the environment could provide important information regarding the health of older adults. In the present study, we examined 263 cognitively intact Amish individuals age 80 and older (74 SA and 189 "normally aged") all of whom are part of a single 13-generation pedigree. A genome-wide association study of 630,309 autosomal single nucleotide polymorphisms (SNPs) was performed and analyzed for linkage using multipoint analyses and for association using the modified quasi-likelihood score test. There was evidence for linkage on 6q25-27 near the fragile site FRA6E region with a dominant model maximum multipoint heterogeneity LOD score = 3.2. The 1-LOD-down support interval for this linkage contained one SNP for which there was regionally significant evidence of association (rs205990, p = 2.36 × 10(-5)). This marker survived interval-wide Bonferroni correction for multiple testing and was located between the genes QKI and PDE10A. Other areas of chromosome 6q25-q27 (including the FRA6E region) contained several SNPs associated with SA (minimum p = 2.89 × 10(-6)). These findings suggest potentially novel genes in the 6q25-q27 region linked and associated with SA in the Amish; however, these findings should be verified in an independent replication cohort.
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http://dx.doi.org/10.1007/s11357-012-9447-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3705095PMC
August 2013

Novel late-onset Alzheimer disease loci variants associate with brain gene expression.

Neurology 2012 Jul 20;79(3):221-8. Epub 2012 Jun 20.

Department of Neuroscience, Biostatistics Unit, Mayo Clinic Florida, Jacksonville, FL, USA.

Objective: Recent genome-wide association studies (GWAS) of late-onset Alzheimer disease (LOAD) identified 9 novel risk loci. Discovery of functional variants within genes at these loci is required to confirm their role in Alzheimer disease (AD). Single nucleotide polymorphisms that influence gene expression (eSNPs) constitute an important class of functional variants. We therefore investigated the influence of the novel LOAD risk loci on human brain gene expression.

Methods: We measured gene expression levels in the cerebellum and temporal cortex of autopsied AD subjects and those with other brain pathologies (∼400 total subjects). To determine whether any of the novel LOAD risk variants are eSNPs, we tested their cis-association with expression of 6 nearby LOAD candidate genes detectable in human brain (ABCA7, BIN1, CLU, MS4A4A, MS4A6A, PICALM) and an additional 13 genes ±100 kb of these SNPs. To identify additional eSNPs that influence brain gene expression levels of the novel candidate LOAD genes, we identified SNPs ±100 kb of their location and tested for cis-associations.

Results: CLU rs11136000 (p = 7.81 × 10(-4)) and MS4A4A rs2304933/rs2304935 (p = 1.48 × 10(-4)-1.86 × 10(-4)) significantly influence temporal cortex expression levels of these genes. The LOAD-protective CLU and risky MS4A4A locus alleles associate with higher brain levels of these genes. There are other cis-variants that significantly influence brain expression of CLU and ABCA7 (p = 4.01 × 10(-5)-9.09 × 10(-9)), some of which also associate with AD risk (p = 2.64 × 10(-2)-6.25 × 10(-5)).

Conclusions: CLU and MS4A4A eSNPs may at least partly explain the LOAD risk association at these loci. CLU and ABCA7 may harbor additional strong eSNPs. These results have implications in the search for functional variants at the novel LOAD risk loci.
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http://dx.doi.org/10.1212/WNL.0b013e3182605801DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3398432PMC
July 2012

Evaluation of copy number variations reveals novel candidate genes in autism spectrum disorder-associated pathways.

Hum Mol Genet 2012 Aug 27;21(15):3513-23. Epub 2012 Apr 27.

John P. Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, Miami, FL 33136, USA.

Autism spectrum disorders (ASDs) are highly heritable, yet relatively few associated genetic loci have been replicated. Copy number variations (CNVs) have been implicated in autism; however, the majority of loci contribute to <1% of the disease population. Therefore, independent studies are important to refine associated CNV regions and discover novel susceptibility genes. In this study, a genome-wide SNP array was utilized for CNV detection by two distinct algorithms in a European ancestry case-control data set. We identify a significantly higher burden in the number and size of deletions, and disrupting more genes in ASD cases. Moreover, 18 deletions larger than 1 Mb were detected exclusively in cases, implicating novel regions at 2q22.1, 3p26.3, 4q12 and 14q23. Case-specific CNVs provided further evidence for pathways previously implicated in ASDs, revealing new candidate genes within the GABAergic signaling and neural development pathways. These include DBI, an allosteric binder of GABA receptors, GABARAPL1, the GABA receptor-associated protein, and SLC6A11, a postsynaptic GABA transporter. We also identified CNVs in COBL, deletions of which cause defects in neuronal cytoskeleton morphogenesis in model vertebrates, and DNER, a neuron-specific Notch ligand required for cerebellar development. Moreover, we found evidence of genetic overlap between ASDs and other neurodevelopmental and neuropsychiatric diseases. These genes include glutamate receptors (GRID1, GRIK2 and GRIK4), synaptic regulators (NRXN3, SLC6A8 and SYN3), transcription factor (ZNF804A) and RNA-binding protein FMR1. Taken together, these CNVs may be a few of the missing pieces of ASD heritability and lead to discovering novel etiological mechanisms.
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http://dx.doi.org/10.1093/hmg/dds164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3392110PMC
August 2012

Evidence of novel fine-scale structural variation at autism spectrum disorder candidate loci.

Mol Autism 2012 Apr 2;3. Epub 2012 Apr 2.

Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, 1501 NW 10 Ave, M-860, Miami, FL 33136, USA.

Background: Autism spectrum disorders (ASD) represent a group of neurodevelopmental disorders characterized by a core set of social-communicative and behavioral impairments. Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the brain, acting primarily via the GABA receptors (GABR). Multiple lines of evidence, including altered GABA and GABA receptor expression in autistic patients, indicate that the GABAergic system may be involved in the etiology of autism.

Methods: As copy number variations (CNVs), particularly rare and de novo CNVs, have now been implicated in ASD risk, we examined the GABA receptors and genes in related pathways for structural variation that may be associated with autism. We further extended our candidate gene set to include 19 genes and regions that had either been directly implicated in the autism literature or were directly related (via function or ancestry) to these primary candidates. For the high resolution CNV screen we employed custom-designed 244 k comparative genomic hybridization (CGH) arrays. Collectively, our probes spanned a total of 11 Mb of GABA-related and additional candidate regions with a density of approximately one probe every 200 nucleotides, allowing a theoretical resolution for detection of CNVs of approximately 1 kb or greater on average. One hundred and sixty-eight autism cases and 149 control individuals were screened for structural variants. Prioritized CNV events were confirmed using quantitative PCR, and confirmed loci were evaluated on an additional set of 170 cases and 170 control individuals that were not included in the original discovery set. Loci that remained interesting were subsequently screened via quantitative PCR on an additional set of 755 cases and 1,809 unaffected family members.

Results: Results include rare deletions in autistic individuals at JAKMIP1, NRXN1, Neuroligin4Y, OXTR, and ABAT. Common insertion/deletion polymorphisms were detected at several loci, including GABBR2 and NRXN3. Overall, statistically significant enrichment in affected vs. unaffected individuals was observed for NRXN1 deletions.

Conclusions: These results provide additional support for the role of rare structural variation in ASD.
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http://dx.doi.org/10.1186/2040-2392-3-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3352055PMC
April 2012
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