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Molecular basis of neurodegeneration in a mouse model of Polr3-related disease (tRNA)

ABSTRACT: Pathogenic variants in subunits of RNA polymerase (Pol) III cause a spectrum of neurodegenerative diseases including 4H leukodystrophy. We developed a postnatal whole-body mouse model expressing pathogenic mutations in Polr3a to examine the molecular mechanisms by which reduced Pol III activity results primarily in central nervous system phenotypes. Polr3a mutant mice exhibit behavioral deficits, exocrine pancreatic atrophy and cerebral pathology. Transcriptome and immunohistochemistry analyses of cerebra show a reduction in most Pol III transcripts, induction of innate immune and integrated stress responses and cell type-specific gene expression changes reflecting neuron and oligodendrocyte loss and microglial activation. A global decrease in mature tRNA levels and an altered tRNA profile preceded cerebral neurodegeneration suggesting a causal role in disease initiation. In cerebella, heart and kidney, Pol III transcripts other than tRNAs were generally unaffected. The results suggest tissue-specific thresholds of sensitivity to defects in Pol III transcription.

ORGANISM(S): Mus musculus

PROVIDER: GSE246161 | GEO | 2024/01/10

REPOSITORIES: GEO

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Molecular basis of neurodegeneration in a mouse model of Polr3-related disease (RNA)

Project description:Pathogenic variants in subunits of RNA polymerase (Pol) III cause a spectrum of neurodegenerative diseases including 4H leukodystrophy. We developed a postnatal whole-body mouse model expressing pathogenic mutations in Polr3a to examine the molecular mechanisms by which reduced Pol III activity results primarily in central nervous system phenotypes. Polr3a mutant mice exhibit behavioral deficits, exocrine pancreatic atrophy and cerebral pathology. Transcriptome and immunohistochemistry analyses of cerebra show a reduction in most Pol III transcripts, induction of innate immune and integrated stress responses and cell type-specific gene expression changes reflecting neuron and oligodendrocyte loss and microglial activation. A global decrease in mature tRNA levels and an altered tRNA profile preceded cerebral neurodegeneration suggesting a causal role in disease initiation. In cerebella, heart and kidney, Pol III transcripts other than tRNAs were generally unaffected. The results suggest tissue-specific thresholds of sensitivity to defects in Pol III transcription.

2024-01-10 | GSE246160 | GEO

Leukodystrophy-associated POLR3A mutations down-regulate the RNA polymerase III transcript and important regulatory RNA BC200

Project description:RNA polymerase III (Pol III) is an essential enzyme responsible for the synthesis of several small non-coding RNAs, a number of which are involved in mRNA translation. Recessive mutations in POLR3A, encoding the largest subunit of Pol III, cause POLR3-related hypomyelinating leukodystrophy (POLR3-HLD), characterized by deficient central nervous system myelination. Identification of the downstream effectors of pathogenic POLR3A mutations has been so far elusive. Here, we used CRISPR-Cas9 to introduce the POLR3A mutation c.2554A>G (p.M852V) into human cell lines and assessed its impact on Pol III biogenesis, nuclear import, DNA occupancy, transcription, and protein levels. Transcriptomic profiling uncovered a subset of transcripts vulnerable to Pol III hypofunction, including a global reduction in tRNA levels. The brain cytoplasmic BC200 RNA (BCYRN1), involved in translation regulation, was consistently affected in all our cellular models, including patient-derived fibroblasts. Genomic BC200 deletion in an oligodendroglial cell line led to major transcriptomic and proteomic changes, having a larger impact than those of POLR3A mutations. Upon differentiation, mRNA levels of the MBP gene, encoding myelin basic protein, were significantly decreased in POLR3A-mutant cells. Our findings provide the first evidence for impaired Pol III transcription in cellular models of POLR3-HLD and identify several candidate effectors, including BC200 RNA, having a potential role in oligodendrocyte biology and involvement in the disease.

2019-03-20 | GSE118739 | GEO

A Multiplicity of Factors Contributes to Selective RNA polymerase III occupancy of a Subset of RNA polymerase III Genes in Mouse Liver

Project description:The genomic loci occupied by RNA polymerase (pol) III have been characterized in human culture cells by genome-wide chromatin immunoprecipitation experiments followed by deep sequencing (ChIP-Seq). These studies have in particular shown that only about 40 % of the annotated 622 human tRNA genes and pseudogenes are occupied by pol III, and that these genes are often in regions of open chromatin rich in active pol II transcription units. Here we have used ChIP-Seq to characterize pol III-occupied loci in a differentiated tissue, the mouse liver. Our studies define the mouse liver pol III-occupied loci and point to a conserved pol III-occupied mammalian interspersed repeat (MIR) as a potential regulator of a pol III subunit-encoding gene. They reveal that synteny relationships can be established between a number of human and mouse pol III genes, and that the expression levels of these genes are significantly linked. They establish that variations within the A and B promoter boxes, as well as the strength of the terminator sequence can strongly affect pol III occupancy of tRNA genes. They reveal correlations with various genomic features that together describe the pol III occupancy scores over some 50% of tRNA genes. In mouse liver, pol III-occupied loci represented in the NCBI37/mm9 genome assembly comprise fifty 5S genes, fourteen known non-tRNA genes, nine 4.5S genes, and some twenty nine SINEs. In addition, out of the 433 annotated tRNA genes, half are occupied by pol III. Transfer RNA gene expression levels reflect both an underlying genomic organization that is conserved in dividing human culture cells and resting mouse liver cells, and the particular promoter and terminator strengths of individual genes. 12 samples examinded, 4 on pol III, 2 on pol II, 2 on H3K4me3, 2 on H3k36me3, 2 input samples.

2012-01-19 | E-GEOD-33421 | biostudies-arrayexpress

Recessive mutations in POLR1C cause a leukodystrophy by impairing biogenesis of RNA polymerase III

Project description:A small proportion of 4H (Hypomyelination, Hypodontia and Hypogonadotropic Hypogonadism) or RNA polymerase III (POLR3)-related leukodystrophy cases are negative for mutations in the previously identified causative genes POLR3A and POLR3B. Here, we report eight of these cases carrying recessive mutations in POLR1C, a gene encoding a shared POLR1 and POLR3 subunit, also mutated in some Treacher Collins syndrome (TCS) cases. Using shotgun proteomics and ChIP-sequencing we demonstrate that leukodystrophy causative mutations, but not TCS mutations, in POLR1C impair assembly and nuclear import of POLR3, but not POLR1, leading to decreased binding to POLR3 target genes. This study is the first to show that distinct mutations in a gene coding for a shared subunit of two RNA polymerases lead to selective modification of the enzymes' availability leading to two different clinical conditions and to shed some light on the pathophysiological mechanism of one of the most common hypomyelinating leukodystrophies, POLR3-related leukodystrophy.

2019-10-16 | PXD002154 | Pride

A Multiplicity of Factors Contributes to Selective RNA polymerase III occupancy of a Subset of RNA polymerase III Genes in Mouse Liver

2012-01-19 | GSE33421 | GEO

Riluzole partially restores RNA polymerase III complex assembly in cells expressing the leukodystrophy-causative variant POLR3B R103H

Project description:The mechanism of assembly of RNA polymerase III (Pol III), the 17-subunit enzyme that synthesizes tRNAs, 5S rRNA, and other small-nuclear (sn) RNAs in eukaryotes, is not clearly understood. The recent discovery of the HSP90 co-chaperone PAQosome (Particle for Arrangement of Quaternary structure) revealed a function for this machinery in the biogenesis of nuclear RNA polymerases. However, the connection between Pol III subunits and the PAQosome during the assembly process remains unexplored. Here, we report the development of a mass spectrometry-based assay that allows the characterization of Pol III assembly. This assay was used to dissect the stages of Pol III assembly, to start defining the function of the PAQosome in this process, to dissect the assembly defects driven by the leukodystrophy-causative R103H substitution in POLR3B, and to discover that riluzole, an FDA-approved drug for alleviation of ALS symptoms, partly corrects these assembly defects. Together, these results shed new light on the mechanism and regulation of human nuclear Pol III biogenesis.

2023-03-10 | PXD034961 | Pride

Leukodystrophy-associated POLR3A mutations down-regulate the RNA polymerase III transcript and important regulatory RNA BC200

Project description:Leukodystrophy-associated POLR3A mutations down-regulate the RNA polymerase III transcript and important regulatory RNA BC200

| PRJNA486660 | ENA

RNA-Seq of six mammals

Project description:Homologous vertebrate tissues express a highly conserved set of transcribed genes; paradoxically, expression of tRNAs that are required to translate mRNAs into proteins have been reported to be divergent. To resolve this paradox, we mapped the genome-wide occupancy of pol III in primary tissues isolated from six mammals. We confirmed that the specific tRNA genes bound by pol III, as well as the extent and stability of binding, can vary substantially among mammalian tissues, and we discovered that this divergence is far greater between species. We combined pol III occupancy from genomically discrete tRNA loci into collective binding into isoacceptor classes and then into amino acid-based isotype classes, and at each step we found increasing conservation. At the level of amino acid isotypes, pol III binding is almost invariant among all the tissues and species profiled. Thus, the basal transcriptional machinery is constrained collectively in its synthesis of functional tRNA isotypes, despite rapid divergence of polymerase binding to specific tRNA genes. Part of experiment series: RNA-Seq E-MTAB-424, ChIP-Seq E-MTAB-958

2011-07-29 | E-MTAB-424 | biostudies-arrayexpress

ChIP-Seq of six mammals tissues: liver, muscle, testes with antibody against RNA polymerase III

2011-07-29 | E-MTAB-958 | biostudies-arrayexpress

Transfer RNA pools in human cells are controlled by selective gene expression [tRNA-Seq]

Project description:Transfer RNAs are required for translating genetic information into protein sequence. The human genome contains hundreds of tRNA genes, many of which in multiple copies. How their expression is regulated to control functional tRNA levels is unknown. Here, we combined quantitative tRNA profiling and ChIP-Seq to measure tRNA expression upon differentiation of human induced pluripotent stem cells (hiPSC) into neuronal and cardiac cells. We find that tRNA transcript pools vary substantially, while the abundance of tRNAs with distinct anticodons, which governs decoding rates, is more stable among cell types. Mechanistically, RNA Polymerase III (Pol III) samples a wide range of tRNA genes in hiPSC and becomes constrained to a housekeeping subset upon differentiation. This is mediated by diminished mTOR signaling, which activates the Pol III repressor MAF1. Our data rationalize how tRNA anticodon pools are buffered in different cellular contexts and reveal that mTOR activity drives selective tRNA expression.

2023-10-23 | GSE227927 | GEO

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