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| 2. |
- Halvardson, Jonatan, et al.
(författare)
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Mutations in HECW2 are associated with intellectual disability and epilepsy
- 2016
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Ingår i: Journal of Medical Genetics. - : BMJ. - 0022-2593 .- 1468-6244. ; 53:10, s. 697-704
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: De novo mutations are a frequent cause of disorders related to brain development. We report the results of screening patients diagnosed with both epilepsy and intellectual disability (ID) using exome sequencing to identify known and new causative de novo mutations relevant to these conditions.METHODS: Exome sequencing was performed on 39 patient-parent trios to identify de novo mutations. Clinical significance of de novo mutations in genes was determined using the American College of Medical Genetics and Genomics standard guidelines for interpretation of coding variants. Variants in genes of unknown clinical significance were further analysed in the context of previous trio sequencing efforts in neurodevelopmental disorders.RESULTS: In 39 patient-parent trios we identified 29 de novo mutations in coding sequence. Analysis of de novo and inherited variants yielded a molecular diagnosis in 11 families (28.2%). In combination with previously published exome sequencing results in neurodevelopmental disorders, our analysis implicates HECW2 as a novel candidate gene in ID and epilepsy.CONCLUSIONS: Our results support the use of exome sequencing as a diagnostic approach for ID and epilepsy, and confirm previous results regarding the importance of de novo mutations in this patient group. The results also highlight the utility of network analysis and comparison to previous large-scale studies as strategies to prioritise candidate genes for further studies. This study adds knowledge to the increasingly growing list of causative and candidate genes in ID and epilepsy and highlights HECW2 as a new candidate gene for neurodevelopmental disorders.
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| 3. |
- Ramos, Jillian, et al.
(författare)
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Identification and rescue of a tRNA wobble inosine deficiency causing intellectual disability disorder
- 2020
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Ingår i: RNA. - : Cold Spring Harbor Laboratory. - 1355-8382 .- 1469-9001. ; 26:11, s. 1654-1666
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Tidskriftsartikel (refereegranskat)abstract
- The deamination of adenosine to inosine at the wobble position of tRNA is an essential post-transcriptional RNA modification required for wobble decoding in bacteria and eukaryotes. In humans, the wobble inosine modification is catalyzed by the heterodimeric ADAT2/3 complex. Here, we describe novel pathogenic ADAT3 variants impairing adenosine deaminase activity through a distinct mechanism that can be corrected through expression of the heterodimeric ADAT2 subunit. The variants were identified in a family in which all three siblings exhibit intellectual disability linked to biallelic variants in the ADAT3 locus. The biallelic ADAT3 variants result in a missense variant converting alanine to valine at a conserved residue or the introduction of a premature stop codon in the deaminase domain. Fibroblast cells derived fromtwo ID-affected individuals exhibit a reduction in tRNA wobble inosine levels and severely diminished adenosine tRNA deaminase activity. Notably, the ADAT3 variants exhibit impaired interaction with the ADAT2 subunit and alterations in ADAT2-dependent nuclear localization. Based upon these findings, we find that tRNA adenosine deaminase activity and wobble inosine modification can be rescued in patient cells by overexpression of the ADAT2 catalytic subunit. These results uncover a key role for the inactive ADAT3 deaminase domain in proper assembly with ADAT2 and demonstrate that ADAT2/3 nuclear import is required for maintaining proper levels of the wobble inosine modification in tRNA.
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| 5. |
- Zaghlool, Ammar, et al.
(författare)
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A Role for the Chromatin-Remodeling Factor BAZ1A in Neurodevelopment
- 2016
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Ingår i: Human Mutation. - : Hindawi Limited. - 1059-7794 .- 1098-1004. ; 37:9, s. 964-975
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Tidskriftsartikel (refereegranskat)abstract
- Chromatin-remodeling factors are required for a wide range of cellular and biological processes including development and cognition, mainly by regulating gene expression. As these functions would predict, deregulation of chromatin-remodeling factors causes various disease syndromes, including neurodevelopmental disorders. Recent reports have linked mutations in several genes coding for chromatin-remodeling factors to intellectual disability (ID). Here, we used exome sequencing and identified a nonsynonymous de novo mutation in BAZ1A (NM_182648.2:c.4043T > G, p.Phe1348Cys), encoding the ATP-utilizing chromatin assembly and remodeling factor 1 (ACF1), in a patient with unexplained ID. ACF1 has been previously reported to bind to the promoter of the vitamin D receptor (VDR)-regulated genes and suppress their expression. Our results show that the patient displays decreased binding of ACF1 to the promoter of the VDR-regulated gene CYP24A1. Using RNA sequencing, we find that the mutation affects the expression of genes involved in several pathways including vitamin D metabolism, Wnt signaling and synaptic formation. RNA sequencing of BAZ1A knockdown cells and Baz1a knockout mice revealed that BAZ1A carry out distinctive functions in different tissues. We also demonstrate that BAZ1A depletion influence the expression of genes important for nervous system development and function. Our data point to an important role for BAZ1A in neurodevelopment, and highlight a possible link for BAZ1A to ID.
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| 6. |
- Zaghlool, Ammar, et al.
(författare)
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Mutation in the chromatin-remodeling factor BAZ1A is associated with intellectual disability
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Exome sequencing has led to the identification of mutations in several genes involved in chromatin remodeling in syndromic forms of intellectual disability. Here, we used exome sequencing to identify a single non-synonymous de novo mutation in BAZ1A, encoding the ATP-utilizing chromatin assembly and remodeling factor 1 (ACF1), in a patient with unexplained intellectual disability. ACF1 has been previously reported to bind to the promoter of vitamin D receptor (VDR) regulated genes and suppress their expression in the absence of vitamin D. We found that the mutation in BAZ1A affects the expression of many genes, mainly involved in extra cellular matrix organization, synaptic function and vitamin D3 metabolism. The differential expression of CYP24A, SYNGAP1 and COL1A2 correlates with the clinical diagnosis of the patient. We therefore propose that BAZ1A represents yet another chromatin remodeling gene involved in causing an intellectual disability syndrome.
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| 7. |
- Zhao, Jin James, 1983-, et al.
(författare)
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Exome sequencing reveals NAA15 and PUF60 as candidate genes associated with intellectual disability
- 2018
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Ingår i: American Journal of Medical Genetics Part B. - : WILEY. - 1552-4841 .- 1552-485X. ; 177:1, s. 10-20
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Tidskriftsartikel (refereegranskat)abstract
- Intellectual Disability (ID) is a clinically heterogeneous condition that affects 2-3% of population worldwide. In recent years, exome sequencing has been a successful strategy for studies of genetic causes of ID, providing a growing list of both candidate and validated ID genes. In this study, exome sequencing was performed on 28 ID patients in 27 patient-parent trios with the aim to identify de novo variants (DNVs) in known and novel ID associated genes. We report the identification of 25 DNVs out of which five were classified as pathogenic or likely pathogenic. Among these, a two base pair deletion was identified in the PUF60 gene, which is one of three genes in the critical region of the 8q24.3 microdeletion syndrome (Verheij syndrome). Our result adds to the growing evidence that PUF60 is responsible for the majority of the symptoms reported for carriers of a microdeletion across this region. We also report variants in several genes previously not associated with ID, including a de novo missense variant in NAA15. We highlight NAA15 as a novel candidate ID gene based on the vital role of NAA15 in the generation and differentiation of neurons in neonatal brain, the fact that the gene is highly intolerant to loss of function and coding variation, and previously reported DNVs in neurodevelopmental disorders.
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| 8. |
- Zhao, Jin James, 1983-, et al.
(författare)
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Reduced cell surface levels of GPI-linked markers in a new case with PIGG loss of function
- 2017
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Ingår i: Human Mutation. - : Hindawi Limited. - 1059-7794 .- 1098-1004. ; 38:10, s. 1394-1401
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Tidskriftsartikel (refereegranskat)abstract
- Glycosylphosphatidylinositol (GPI) is a glycolipid that tethers more than 150 different proteins to the cell surface. Aberrations in biosynthesis of GPI anchors cause congenital disorders of glycosylation with clinical features including intellectual disability (ID), seizures, and facial dysmorphism. Here, we present two siblings with ID, cerebellar hypoplasia, cerebellar ataxia, early-onset seizures, and minor facial dysmorphology. Using exome sequencing, we identified a homozygous nonsense variant (NM_001127178.1:c.1640G>A, p.Trp547*) in the gene Phosphatidylinositol Glycan Anchor Biosynthesis, Class G (PIGG) in both the patients. Variants in several other GPI anchor synthesis genes lead to a reduced expression of GPI-anchored proteins (GPI-APs) that can be measured by flow cytometry. No significant differences in GPI-APs could be detected in patient granulocytes, consistent with recent findings. However, fibroblasts showed a reduced global level of GPI anchors and of specific GPI-linked markers. These findings suggest that fibroblasts might be more sensitive to pathogenic variants in GPI synthesis pathway and are well suited to screen for GPI-anchor deficiencies. Based on genetic and functional evidence, we confirm that pathogenic variants in PIGG cause an ID syndrome, and we find that loss of function of PIGG is associated with GPI deficiency.
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