Publications by authors named "Tanyeri Barak"

6 Publications

  • Page 1 of 1

DIAPH1 Variants in Non-East Asian Patients With Sporadic Moyamoya Disease.

JAMA Neurol 2021 Jun 14. Epub 2021 Jun 14.

Yale Center for Genome Analysis, West Haven, Connecticut.

Importance: Moyamoya disease (MMD), a progressive vasculopathy leading to narrowing and ultimate occlusion of the intracranial internal carotid arteries, is a cause of childhood stroke. The cause of MMD is poorly understood, but genetic factors play a role. Several familial forms of MMD have been identified, but the cause of most cases remains elusive, especially among non-East Asian individuals.

Objective: To assess whether ultrarare de novo and rare, damaging transmitted variants with large effect sizes are associated with MMD risk.

Design, Setting, And Participants: A genetic association study was conducted using whole-exome sequencing case-parent MMD trios in a small discovery cohort collected over 3.5 years (2016-2019); data were analyzed in 2020. Medical records from US hospitals spanning a range of 1 month to 1.5 years were reviewed for phenotyping. Exomes from a larger validation cohort were analyzed to identify additional rare, large-effect variants in the top candidate gene. Participants included patients with MMD and, when available, their parents. All participants who met criteria and were presented with the option to join the study agreed to do so; none were excluded. Twenty-four probands (22 trios and 2 singletons) composed the discovery cohort, and 84 probands (29 trios and 55 singletons) composed the validation cohort.

Main Outcomes And Measures: Gene variants were identified and filtered using stringent criteria. Enrichment and case-control tests assessed gene-level variant burden. In silico modeling estimated the probability of variant association with protein structure. Integrative genomics assessed expression patterns of MMD risk genes derived from single-cell RNA sequencing data of human and mouse brain tissue.

Results: Of the 24 patients in the discovery cohort, 14 (58.3%) were men and 18 (75.0%) were of European ancestry. Three of 24 discovery cohort probands contained 2 do novo (1-tailed Poisson P = 1.1 × 10-6) and 1 rare, transmitted damaging variant (12.5% of cases) in DIAPH1 (mammalian diaphanous-1), a key regulator of actin remodeling in vascular cells and platelets. Four additional ultrarare damaging heterozygous DIAPH1 variants (3 unphased) were identified in 3 other patients in an 84-proband validation cohort (73.8% female, 77.4% European). All 6 patients were non-East Asian. Compound heterozygous variants were identified in ena/vasodilator-stimulated phosphoproteinlike protein EVL, a mammalian diaphanous-1 interactor that regulates actin polymerization. DIAPH1 and EVL mutant probands had severe, bilateral MMD associated with transfusion-dependent thrombocytopenia. DIAPH1 and other MMD risk genes are enriched in mural cells of midgestational human brain. The DIAPH1 coexpression network converges in vascular cell actin cytoskeleton regulatory pathways.

Conclusions And Relevance: These findings provide the largest collection to date of non-East Asian individuals with sporadic MMD harboring pathogenic variants in the same gene. The results suggest that DIAPH1 is a novel MMD risk gene and impaired vascular cell actin remodeling in MMD pathogenesis, with diagnostic and therapeutic ramifications.
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http://dx.doi.org/10.1001/jamaneurol.2021.1681DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8204259PMC
June 2021

Somatic POLE mutations cause an ultramutated giant cell high-grade glioma subtype with better prognosis.

Neuro Oncol 2015 Oct 3;17(10):1356-64. Epub 2015 Mar 3.

Department of Neurosurgery, Yale Program in Brain Tumor Research, Yale School of Medicine, New Haven, Connecticut (E.Z.E.-O., A.O.Ç., S.B.O., A.S.H., V.C., G.C.-G., J.B., C.Ç., T.B., S.C., B.B., M.B., J.M.G., K.M.-G., K.B., K.Y., M.G.); Department of Genetics, Yale School of Medicine, New Haven, Connecticut (K.B., M.G.); Computational Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York (N.S., N.W., C.S.); Department of Neurosurgery, Acıbadem University School of Medicine, Istanbul, Turkey (K.O., M.N.P.); Division of Hematology and Oncology, Faculty of Medicine, Department of Pediatrics, Selçuk University, Konya, Turkey (Y.K., D.K.); Department of Pathology, Yale School of Medicine, New Haven, Connecticut (J.L., J.S., A.V., A.J.H.).

Background: Malignant high-grade gliomas (HGGs), including the most aggressive form, glioblastoma multiforme, show significant clinical and genomic heterogeneity. Despite recent advances, the overall survival of HGGs and their response to treatment remain poor. In order to gain further insight into disease pathophysiology by correlating genomic landscape with clinical behavior, thereby identifying distinct HGG molecular subgroups associated with improved prognosis, we performed a comprehensive genomic analysis.

Methods: We analyzed and compared 720 exome-sequenced gliomas (136 from Yale, 584 from The Cancer Genome Atlas) based on their genomic, histological, and clinical features.

Results: We identified a subgroup of HGGs (6 total, 4 adults and 2 children) that harbored a statistically significantly increased number of somatic mutations (mean = 9257.3 vs 76.2, P = .002). All of these "ultramutated" tumors harbored somatic mutations in the exonuclease domain of the polymerase epsilon gene (POLE), displaying a distinctive genetic profile, characterized by genomic stability and increased C-to-A transversions. Histologically, they all harbored multinucleated giant or bizarre cells, some with predominant infiltrating immune cells. One adult and both pediatric patients carried homozygous germline mutations in the mutS homolog 6 (MSH6) gene. In adults, POLE mutations were observed in patients younger than 40 years and were associated with a longer progression-free survival.

Conclusions: We identified a genomically, histologically, and clinically distinct subgroup of HGGs that harbored somatic POLE mutations and carried an improved prognosis. Identification of distinctive molecular and pathological HGG phenotypes has implications not only for improved classification but also for potential targeted treatments.
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http://dx.doi.org/10.1093/neuonc/nov027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4578578PMC
October 2015

Recessive LAMC3 mutations cause malformations of occipital cortical development.

Nat Genet 2011 Jun 15;43(6):590-4. Epub 2011 May 15.

Department of Neurosurgery, Yale School of Medicine, New Haven, Connecticut, USA.

The biological basis for regional and inter-species differences in cerebral cortical morphology is poorly understood. We focused on consanguineous Turkish families with a single affected member with complex bilateral occipital cortical gyration abnormalities. By using whole-exome sequencing, we initially identified a homozygous 2-bp deletion in LAMC3, the laminin γ3 gene, leading to an immediate premature termination codon. In two other affected individuals with nearly identical phenotypes, we identified a homozygous nonsense mutation and a compound heterozygous mutation. In human but not mouse fetal brain, LAMC3 is enriched in postmitotic cortical plate neurons, localizing primarily to the somatodendritic compartment. LAMC3 expression peaks between late gestation and late infancy, paralleling the expression of molecules that are important in dendritogenesis and synapse formation. The discovery of the molecular basis of this unusual occipital malformation furthers our understanding of the complex biology underlying the formation of cortical gyrations.
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http://dx.doi.org/10.1038/ng.836DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3329933PMC
June 2011

The essential role of centrosomal NDE1 in human cerebral cortex neurogenesis.

Am J Hum Genet 2011 May 28;88(5):523-35. Epub 2011 Apr 28.

Department of Neurosurgery, Center for Human Genetics and Genomics, and Program on Neurogenetics, Yale School of Medicine, New Haven, CT 06510, USA.

We investigated three families whose offspring had extreme microcephaly at birth and profound mental retardation. Brain scans and postmortem data showed that affected individuals had brains less than 10% of expected size (≤10 standard deviation) and that in addition to a massive reduction in neuron production they displayed partially deficient cortical lamination (microlissencephaly). Other body systems were apparently unaffected and overall growth was normal. We found two distinct homozygous mutations of NDE1, c.83+1G>T (p.Ala29GlnfsX114) in a Turkish family and c.684_685del (p.Pro229TrpfsX85) in two families of Pakistani origin. Using patient cells, we found that c.83+1G>T led to the use of a novel splice site and to a frameshift after NDE1 exon 2. Transfection of tagged NDE1 constructs showed that the c.684_685del mutation resulted in a NDE1 that was unable to localize to the centrosome. By staining a patient-derived cell line that carried the c.83+1G>T mutation, we found that this endogeneously expressed mutated protein equally failed to localize to the centrosome. By examining human and mouse embryonic brains, we determined that NDE1 is highly expressed in neuroepithelial cells of the developing cerebral cortex, particularly at the centrosome. We show that NDE1 accumulates on the mitotic spindle of apical neural precursors in early neurogenesis. Thus, NDE1 deficiency causes both a severe failure of neurogenesis and a deficiency in cortical lamination. Our data further highlight the importance of the centrosome in multiple aspects of neurodevelopment.
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http://dx.doi.org/10.1016/j.ajhg.2011.03.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3146716PMC
May 2011

The effects of protein kinase C activator phorbol dibutyrate on traumatic brain edema and aquaporin-4 expression.

Ulus Travma Acil Cerrahi Derg 2010 Sep;16(5):390-4

Department of Neurosurgery, İstanbul University, İstanbul Faculty of Medicine, İstanbul, Turkey.

Background: Aquaporin-4 (AQP4) is the major water channel in the central nervous system. Brain edema emerges from increased AQP4 expression in traumatic brain injury (TBI). Cell line studies have shown that the protein kinase activator phorbol ester exerts a suppressive effect on AQP4 and water permeability. The aim of this study was to investigate the effects of a phorbol ester, phorbol dibutyrate (PDBu), on increased TBI AQP4 expression and accompanying brain edema.

Methods: Fifty-six male Wistar rats were first divided into two groups: the edema group, in which the percentage of water in brain tissue would be evaluated, and the immunohistochemical group, allowing AQP4 expression to be determined. Both groups were further sub-divided into four groups consisting of 7 subjects. These four groups were as follows: sham-operated control group, severe diffuse TBI group, 0.9% saline-treated diffuse TBI group, and the PDBu-treated diffuse TBI group (2300 µg/kg, iv). The results were evaluated statistically.

Results: PDBu treatment significantly reduced brain water concentration (p<0.001). Furthermore, PDBu was found to reduce trauma-induced AQP4 upregulation (p<0.05).

Conclusion: This study showed that traumatic brain edema was prevented by intravenous PDBu administration via AQP4 downregulation, supporting the idea emphasizing the importance of AQP4 expression control in TBI.
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September 2010

Whole-exome sequencing identifies recessive WDR62 mutations in severe brain malformations.

Nature 2010 Sep 22;467(7312):207-10. Epub 2010 Aug 22.

Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut 06510, USA.

The development of the human cerebral cortex is an orchestrated process involving the generation of neural progenitors in the periventricular germinal zones, cell proliferation characterized by symmetric and asymmetric mitoses, followed by migration of post-mitotic neurons to their final destinations in six highly ordered, functionally specialized layers. An understanding of the molecular mechanisms guiding these intricate processes is in its infancy, substantially driven by the discovery of rare mutations that cause malformations of cortical development. Mapping of disease loci in putative Mendelian forms of malformations of cortical development has been hindered by marked locus heterogeneity, small kindred sizes and diagnostic classifications that may not reflect molecular pathogenesis. Here we demonstrate the use of whole-exome sequencing to overcome these obstacles by identifying recessive mutations in WD repeat domain 62 (WDR62) as the cause of a wide spectrum of severe cerebral cortical malformations including microcephaly, pachygyria with cortical thickening as well as hypoplasia of the corpus callosum. Some patients with mutations in WDR62 had evidence of additional abnormalities including lissencephaly, schizencephaly, polymicrogyria and, in one instance, cerebellar hypoplasia, all traits traditionally regarded as distinct entities. In mice and humans, WDR62 transcripts and protein are enriched in neural progenitors within the ventricular and subventricular zones. Expression of WDR62 in the neocortex is transient, spanning the period of embryonic neurogenesis. Unlike other known microcephaly genes, WDR62 does not apparently associate with centrosomes and is predominantly nuclear in localization. These findings unify previously disparate aspects of cerebral cortical development and highlight the use of whole-exome sequencing to identify disease loci in settings in which traditional methods have proved challenging.
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http://dx.doi.org/10.1038/nature09327DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3129007PMC
September 2010
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