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Yılmaz M, Kamaşak T, Teralı K, Çebi AH, Türkyılmaz A. The first Turkish family with a novel biallelic missense variant of the ALKBH8 gene: A study on the clinical and variant spectrum of ALKBH8-related intellectual developmental disorders. Am J Med Genet A 2024; 194:e63535. [PMID: 38189198 DOI: 10.1002/ajmg.a.63535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Revised: 12/12/2023] [Accepted: 12/26/2023] [Indexed: 01/09/2024]
Abstract
ABH8, the protein encoded by the ALKBH8 gene, modifies tRNAs by methylating their anticodon wobble uridine residues. The variations in the ALKBH8 gene are associated with the "intellectual developmental disorder, autosomal recessive type 71" (MIM: 618504) phenotype in the OMIM database. This phenotype is characterized by global developmental delay, facial dysmorphic features, and psychiatric problems. To date, 12 patients from five distinct families carrying variants of the ALKBH8 gene have been reported in the literature. In the present study, we report the first Turkish family harboring a novel homozygous missense variant, NM_138775.3:c.1874G > C (p.Arg625Pro), in the last exon of the ALKBH8 gene. Two affected siblings in this family showed signs of global developmental delay and intellectual disability. Based on the dysmorphological assessment of the cases, fifth finger clinodactyly and fetal fingertip pads were prominent, in addition to the dysmorphic findings similar to those reported in previous studies. Minor dysmorphic limb anomalies in relation to this phenotype have not yet been previously reported in the literature. Our computational studies revealed the potential deleterious effects of the Arg-to-Pro substitution on the structure and stability of the ABH8 methyltransferase domain. In the present report, the first Turkish family with an ultrarare disease associated with the ALKBH8 gene was reported, and a novel deleterious variant in the ALKBH8 gene and additional clinical features that were not reported with this condition have been reported.
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Affiliation(s)
- Mustafa Yılmaz
- Department of Medical Genetics, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey
| | - Tülay Kamaşak
- Department of Pediatric Neurology, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey
| | - Kerem Teralı
- Department of Medical Biochemistry, Faculty of Medicine, Cyprus International University, Nicosia, Cyprus
| | - Alper Han Çebi
- Department of Medical Genetics, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey
| | - Ayberk Türkyılmaz
- Department of Medical Genetics, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey
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Madhwani KR, Sayied S, Ogata CH, Hogan CA, Lentini JM, Mallik M, Dumouchel JL, Storkebaum E, Fu D, O’Connor-Giles KM. tRNA modification enzyme-dependent redox homeostasis regulates synapse formation and memory. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.14.566895. [PMID: 38014328 PMCID: PMC10680711 DOI: 10.1101/2023.11.14.566895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Post-transcriptional modification of RNA regulates gene expression at multiple levels. ALKBH8 is a tRNA modifying enzyme that methylates wobble uridines in specific tRNAs to modulate translation. Through methylation of tRNA-selenocysteine, ALKBH8 promotes selenoprotein synthesis and regulates redox homeostasis. Pathogenic variants in ALKBH8 have been linked to intellectual disability disorders in the human population, but the role of ALKBH8 in the nervous system is unknown. Through in vivo studies in Drosophila, we show that ALKBH8 controls oxidative stress in the brain to restrain synaptic growth and support learning and memory. ALKBH8 null animals lack wobble uridine methylation and exhibit a global reduction in protein synthesis, including a specific decrease in selenoprotein levels. Loss of ALKBH8 or independent disruption of selenoprotein synthesis results in ectopic synapse formation. Genetic expression of antioxidant enzymes fully suppresses synaptic overgrowth in ALKBH8 null animals, confirming oxidative stress as the underlying cause of dysregulation. ALKBH8 animals also exhibit associative learning and memory impairments that are reversed by pharmacological antioxidant treatment. Together, these findings demonstrate the critical role of tRNA modification in redox homeostasis in the nervous system and reveal antioxidants as a potential therapy for ALKBH8-associated intellectual disability.
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Affiliation(s)
| | - Shanzeh Sayied
- Department of Neuroscience, Brown University, Providence, RI, USA
| | | | - Caley A. Hogan
- Laboratory of Genetics, University of Wisconsin-Madison, Madison, WI, USA
| | - Jenna M. Lentini
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, NY, USA
| | - Moushami Mallik
- Molecular Neurobiology Laboratory, Donders Institute for Brain, Cognition, and Behaviour, Radboud University, Nijmegen, NL
| | | | - Erik Storkebaum
- Molecular Neurobiology Laboratory, Donders Institute for Brain, Cognition, and Behaviour, Radboud University, Nijmegen, NL
| | - Dragony Fu
- Department of Biology, Center for RNA Biology, University of Rochester, Rochester, NY, USA
| | - Kate M. O’Connor-Giles
- Department of Neuroscience, Brown University, Providence, RI, USA
- Carney Institute for Brain Sciences, Brown University, Providence, RI, USA
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Hogan CA, Gratz SJ, Dumouchel JL, Thakur RS, Delgado A, Lentini JM, Madhwani KR, Fu D, O'Connor‐Giles KM. Expanded tRNA methyltransferase family member TRMT9B regulates synaptic growth and function. EMBO Rep 2023; 24:e56808. [PMID: 37642556 PMCID: PMC10561368 DOI: 10.15252/embr.202356808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 08/03/2023] [Accepted: 08/14/2023] [Indexed: 08/31/2023] Open
Abstract
Nervous system function rests on the formation of functional synapses between neurons. We have identified TRMT9B as a new regulator of synapse formation and function in Drosophila. TRMT9B has been studied for its role as a tumor suppressor and is one of two metazoan homologs of yeast tRNA methyltransferase 9 (Trm9), which methylates tRNA wobble uridines. Whereas Trm9 homolog ALKBH8 is ubiquitously expressed, TRMT9B is enriched in the nervous system. However, in the absence of animal models, TRMT9B's role in the nervous system has remained unstudied. Here, we generate null alleles of TRMT9B and find it acts postsynaptically to regulate synaptogenesis and promote neurotransmission. Through liquid chromatography-mass spectrometry, we find that ALKBH8 catalyzes canonical tRNA wobble uridine methylation, raising the question of whether TRMT9B is a methyltransferase. Structural modeling studies suggest TRMT9B retains methyltransferase function and, in vivo, disruption of key methyltransferase residues blocks TRMT9B's ability to rescue synaptic overgrowth, but not neurotransmitter release. These findings reveal distinct roles for TRMT9B in the nervous system and highlight the significance of tRNA methyltransferase family diversification in metazoans.
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Affiliation(s)
- Caley A Hogan
- Genetics Training ProgramUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Scott J Gratz
- Department of NeuroscienceBrown UniversityProvidenceRIUSA
| | | | - Rajan S Thakur
- Department of NeuroscienceBrown UniversityProvidenceRIUSA
| | - Ambar Delgado
- Department of NeuroscienceBrown UniversityProvidenceRIUSA
| | - Jenna M Lentini
- Department of Biology, Center for RNA BiologyUniversity of RochesterRochesterNYUSA
| | | | - Dragony Fu
- Department of Biology, Center for RNA BiologyUniversity of RochesterRochesterNYUSA
| | - Kate M O'Connor‐Giles
- Department of NeuroscienceBrown UniversityProvidenceRIUSA
- Carney Institute for Brain ScienceProvidenceRIUSA
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Cavallin I, Bartosovic M, Skalicky T, Rengaraj P, Demko M, Schmidt-Dengler MC, Drino A, Helm M, Vanacova S. HITS-CLIP analysis of human ALKBH8 reveals interactions with fully processed substrate tRNAs and with specific noncoding RNAs. RNA (NEW YORK, N.Y.) 2022; 28:1568-1581. [PMID: 36192131 PMCID: PMC9670814 DOI: 10.1261/rna.079421.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2022] [Accepted: 09/09/2022] [Indexed: 06/16/2023]
Abstract
Transfer RNAs acquire a large plethora of chemical modifications. Among those, modifications of the anticodon loop play important roles in translational fidelity and tRNA stability. Four human wobble U-containing tRNAs obtain 5-methoxycarbonylmethyluridine (mcm5U34) or 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U34), which play a role in decoding. This mark involves a cascade of enzymatic activities. The last step is mediated by alkylation repair homolog 8 (ALKBH8). In this study, we performed a transcriptome-wide analysis of the repertoire of ALKBH8 RNA targets. Using a combination of HITS-CLIP and RIP-seq analyses, we uncover ALKBH8-bound RNAs. We show that ALKBH8 targets fully processed and CCA modified tRNAs. Our analyses uncovered the previously known set of wobble U-containing tRNAs. In addition, both our approaches revealed ALKBH8 binding to several other types of noncoding RNAs, in particular C/D box snoRNAs.
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Affiliation(s)
- Ivana Cavallin
- Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic
| | - Marek Bartosovic
- Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic
| | - Tomas Skalicky
- Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic
- Institute of Parasitology, Biology Centre, Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic
| | - Praveenkumar Rengaraj
- Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic
| | - Martin Demko
- Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic
| | | | - Aleksej Drino
- Medical University of Vienna, Center for Anatomy and Cell Biology, 1090 Vienna, Austria
| | - Mark Helm
- Johannes Gutenberg-Universität Mainz, Institute of Pharmaceutical and Biomedical Science (IPBS), D-55128 Mainz, Germany
| | - Stepanka Vanacova
- Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic
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Lee MY, Ojeda-Britez S, Ehrbar D, Samwer A, Begley TJ, Melendez JA. Selenoproteins and the senescence-associated epitranscriptome. Exp Biol Med (Maywood) 2022; 247:2090-2102. [PMID: 36036467 PMCID: PMC9837304 DOI: 10.1177/15353702221116592] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Selenium is a naturally found trace element, which provides multiple benefits including antioxidant, anticancer, and antiaging, as well as boosting immunity. One unique feature of selenium is its incorporation as selenocysteine, a rare 21st amino acid, into selenoproteins. Twenty-five human selenoproteins have been discovered, and a majority of these serve as crucial antioxidant enzymes for redox homeostasis. Unlike other amino acids, incorporation of selenocysteine requires a distinctive UGA stop codon recoding mechanism. Although many studies correlating selenium, selenoproteins, aging, and senescence have been performed, it has not yet been explored if the upstream events regulating selenoprotein synthesis play a role in senescence-associated pathologies. The epitranscriptomic writer alkylation repair homolog 8 (ALKBH8) is critical for selenoprotein production, and its deficiency can significantly decrease levels of selenoproteins that are essential for reactive oxygen species (ROS) detoxification, and increase oxidative stress, one of the major drivers of cellular senescence. Here, we review the potential role of epitranscriptomic marks that govern selenocysteine utilization in regulating the senescence program.
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Affiliation(s)
- May Y Lee
- College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, NY 12203, USA
- The RNA Institute, University at Albany, Albany, NY 12222, USA
| | - Stephen Ojeda-Britez
- College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, NY 12203, USA
| | - Dylan Ehrbar
- The RNA Institute, University at Albany, Albany, NY 12222, USA
- Department of Biological Sciences, University at Albany, Albany, NY 12222, USA
- RNA Epitranscriptomics and Proteomics Resource, University at Albany, Albany, NY 12222, USA
| | | | - Thomas J Begley
- The RNA Institute, University at Albany, Albany, NY 12222, USA
- Department of Biological Sciences, University at Albany, Albany, NY 12222, USA
- RNA Epitranscriptomics and Proteomics Resource, University at Albany, Albany, NY 12222, USA
| | - J Andres Melendez
- College of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, NY 12203, USA
- The RNA Institute, University at Albany, Albany, NY 12222, USA
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Waqas A, Nayab A, Shaheen S, Abbas S, Latif M, Rafeeq MM, Al-Dhuayan IS, Alqosaibi AI, Alnamshan MM, Sain ZM, Habib AH, Alam Q, Umair M, Saqib MAN. Case Report: Biallelic Variant in the tRNA Methyltransferase Domain of the AlkB Homolog 8 Causes Syndromic Intellectual Disability. Front Genet 2022; 13:878274. [PMID: 35571055 PMCID: PMC9096442 DOI: 10.3389/fgene.2022.878274] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 03/18/2022] [Indexed: 11/23/2022] Open
Abstract
Intellectual disability (ID) has become very common and is an extremely heterogeneous disorder, where the patients face many challenges with deficits in intellectual functioning and adaptive behaviors. A single affected family revealed severe disease phenotypes such as ID, developmental delay, dysmorphic facial features, postaxial polydactyly type B, and speech impairment. DNA of a single affected individual was directly subjected to whole exome sequencing (WES), followed by Sanger sequencing. Data analysis revealed a novel biallelic missense variant (c.1511G>C; p.(Trp504Ser)) in the ALKBH8 gene, which plays a significant role in tRNA modifications. Our finding adds another variant to the growing list of ALKBH8-associated tRNA modifications causing ID and additional phenotypic manifestations. The present study depicts the key role of the genes associated with tRNA modifications, such as ALKBH8, in the development and pathophysiology of the human brain.
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Affiliation(s)
- Ahmed Waqas
- Department of Zoology, Division of Science and Technology, University of Education, Lahore, Pakistan
| | - Anam Nayab
- Microbiology and Biotechnology Research Lab, Department of Biotechnology, Fatima Jinnah Women University, The Mall, Rawalpindi, Pakistan
| | - Shabnam Shaheen
- Department of Higher Education, Government Girls Degree College Lakki Marwat, Lakki Marwat, Pakistan
| | - Safdar Abbas
- Department of Biological Science, Darmouth College, Hanover, NH, United States
| | - Muhammad Latif
- Department of Zoology, Division of Science and Technology, University of Education, Lahore, Pakistan
| | - Misbahuddin M Rafeeq
- Department of Pharmacology, Faculty of Medicine, Rabigh, King Abduaziz University, Jeddah, Saudi Arabia
| | - Ibtesam S Al-Dhuayan
- Department of Biology, College of Science, Imam Abdulrahman bin Faisal University, Dammam, Saudi Arabia
| | - Amany I Alqosaibi
- Department of Biology, College of Science, Imam Abdulrahman bin Faisal University, Dammam, Saudi Arabia
| | - Mashael M Alnamshan
- Department of Biology, College of Science, Imam Abdulrahman bin Faisal University, Dammam, Saudi Arabia
| | - Ziaullah M Sain
- Department of Microbiology, Faculty of Medicine, Rabigh, King Abduaziz University, Jeddah, Saudi Arabia
| | - Alaa Hamed Habib
- Department of Physiology, Faculty of Medicine, King Abduaziz University, Jeddah, Saudi Arabia
| | - Qamre Alam
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia
| | - Muhammad Umair
- Medical Genomics Research Department, King Abdullah International Medical Research Center (KAIMRC), King Saud Bin Abdulaziz University for Health Sciences, Ministry of National Guard Health Affairs (MNGH), Riyadh, Saudi Arabia.,Department of Life Sciences, School of Science, University of Management and Technology (UMT), Lahore, Pakistan
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