Novel Pathogenic Variants in Cause POLR3-Related Leukodystrophy.

POLR3-related hypomyelinating leukodystrophy (POLR3-HLD) is a rare inherited neurological disorder caused by biallelic pathogenic variants in specific genes encoding subunits of RNA polymerase III (Pol III). Here, we report the third patient worldwide with pathogenic variants in and clinical features consistent with POLR3-HLD. The female patient presented with mild intellectual and behavioural disturbances in childhood, as well as growth delay, with brain MRI revealing diffuse hypomyelination and a pattern consistent with POLR3-HLD.

Biallelic pathogenic variants in alter tRNA transcription and cause a hypomyelinating leukodystrophy: A case report.

RNA polymerase III-related leukodystrophy (POLR3-related leukodystrophy) is a rare, genetically determined hypomyelinating disease arising from biallelic pathogenic variants in genes encoding subunits of RNA polymerase III (Pol III). Here, we describe the first reported case of POLR3-related leukodystrophy caused by biallelic pathogenic variants in , encoding the RPC4 subunit of Pol III. The individual, a female, demonstrated delays in walking and expressive and receptive language as a child and later cognitively plateaued.

Solving inherited white matter disorder etiologies in the neurology clinic: Challenges and lessons learned using next-generation sequencing.

Introduction: Rare neurodevelopmental disorders, including inherited white matter disorders or leukodystrophies, often present a diagnostic challenge on a genetic level given the large number of causal genes associated with a range of disease subtypes. This study aims to demonstrate the challenges and lessons learned in the genetic investigations of leukodystrophies through presentation of a series of cases solved using exome or genome sequencing.

Methods: Each of the six patients had a leukodystrophy associated with hypomyelination or delayed myelination on MRI, and inconclusive clinical diagnostic genetic testing results.

Variants in impair LSM complexes assembly, neurodevelopment in zebrafish and may be associated with an ultra-rare neurological disease.

Leukodystrophies, genetic neurodevelopmental and/or neurodegenerative disorders of cerebral white matter, result from impaired myelin homeostasis and metabolism. Numerous genes have been implicated in these heterogeneous disorders; however, many individuals remain without a molecular diagnosis. Using whole-exome sequencing, biallelic variants in were uncovered in two unrelated individuals, one with a leukodystrophy and the other who died .

Expanding the phenotypic and molecular spectrum of RNA polymerase III-related leukodystrophy.

Objective: To expand the phenotypic spectrum of severity of POLR3-related leukodystrophy and identify genotype-phenotype correlations through study of patients with extremely severe phenotypes.

Methods: We performed an international cross-sectional study on patients with genetically proven POLR3-related leukodystrophy and atypical phenotypes to identify 6 children, 3 males and 3 females, with an extremely severe phenotype compared with that typically reported. Clinical, radiologic, and molecular features were evaluated for all patients, and functional and neuropathologic studies were performed on 1 patient.

Clinical spectrum of POLR3-related leukodystrophy caused by biallelic pathogenic variants.

Objective: To determine the clinical, radiologic, and molecular characteristics of RNA polymerase III-related leukodystrophy (POLR3-HLD) caused by biallelic pathogenic variants.

Methods: A cross-sectional observational study involving 25 centers worldwide was conducted. Clinical and molecular information was collected on 23 unreported and previously reported patients with POLR3-HLD and biallelic pathogenic variants in .

Dystonia in RNA Polymerase III-Related Leukodystrophy.

Objectives: To identify the prevalence of dystonia in a RNA Polymerase III (POLR3)-related leukodystrophy patient cohort and to further characterize their dystonic features.

Background: POLR3-related leukodystrophy is a hypomyelinating leukodystrophy characterized by neurological and non-neurological features. Dystonia remains a challenging and under-recognized feature.

Biallelic mutations in valyl-tRNA synthetase gene VARS are associated with a progressive neurodevelopmental epileptic encephalopathy.

Aminoacyl-tRNA synthetases (ARSs) function to transfer amino acids to cognate tRNA molecules, which are required for protein translation. To date, biallelic mutations in 31 ARS genes are known to cause recessive, early-onset severe multi-organ diseases. VARS encodes the only known valine cytoplasmic-localized aminoacyl-tRNA synthetase.

Biallelic Loss-of-Function Variants in AIMP1 Cause a Rare Neurodegenerative Disease.

AIMP1/p43, is a noncatalytic component of the mammalian multi-tRNA synthetase complex that catalyzes the ligation of amino acids to their cognate tRNAs. AIMP1 is largely expressed in the central nervous system, where it is part of the regulatory machine of the neurofilament assembly, playing a crucial role in neuronal development and function. To date, nonsense mutations in AIMP1 have been associated with a primary neurodegenerative disorder consisting of cerebral atrophy, hypomyelination, microcephaly and epilepsy, whereas missense mutations have recently been linked to intellectual disability without neurodegeneration.

Bi-allelic Mutations in EPRS, Encoding the Glutamyl-Prolyl-Aminoacyl-tRNA Synthetase, Cause a Hypomyelinating Leukodystrophy.

Hypomyelinating leukodystrophies are genetic disorders characterized by insufficient myelin deposition during development. They are diagnosed on the basis of both clinical and MRI features followed by genetic confirmation. Here, we report on four unrelated affected individuals with hypomyelination and bi-allelic pathogenic variants in EPRS, the gene encoding cytoplasmic glutamyl-prolyl-aminoacyl-tRNA synthetase.

Diffuse hypomyelination is not obligate for POLR3-related disorders.

Objective: To report atypical MRI patterns associated with POLR3A and POLR3B mutations.

Methods: This was a multicenter retrospective study to collect neuroradiologic, clinical, and molecular data of patients with mutations in POLR3A and POLR3B without the classic MRI phenotype, i.e.

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

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.

Large exonic deletions in POLR3B gene cause POLR3-related leukodystrophy.

POLR3-related (or 4H) leukodystrophy is an autosomal recessive disorder caused by mutations in POLR3A or POLR3B and is characterized by neurological and non-neurological features. In a small proportion of patients, no mutation in either gene or only one mutation is found. Analysis of the POLR3B cDNA revealed a large deletion of exons 21-22 in one case and of exons 26-27 in another case.

POLR3A and POLR3B Mutations in Unclassified Hypomyelination.

Objective: This study aims to ascertain frequency of mutations in POLR3A or POLR3B, which are associated with 4H leukodystrophy, in a cohort of patients with unclassified hypomyelination.

Methods And Results: In a cohort of 22 patients with the magnetic resonance imaging (MRI) diagnosis of unclassified hypomyelination and without typical clinical signs, we evaluated clinical and MRI features. Developmental delay or intellectual disability, ataxia, and spasticity were frequent symptoms.

Neurogenic bladder and neuroendocrine abnormalities in Pol III-related leukodystrophy.

Background: Pol III-related leukodystrophies, including 4H leukodystrophy, are recently recognized disorders that comprise hypomyelination and various neurologic and non-neurologic clinical manifestations. We report the unique neurologic presentation of the micturition dysfunction in Pol III-related leukodystrophy and describe the novel endocrine abnormalities in this entity.

Case Presentation: A 32-year-old Caucasian female exhibited chronic urinary incontinence that commenced at the age of 7 years and remained the unexplained symptom more than two decades before the onset of progressive neurologic decline.

Spastic paraparesis and marked improvement of leukoencephalopathy in Aicardi-Goutières syndrome.

Aicardi-Goutières syndrome (AGS) is a rare genetic disorder with inflammatory immune-mediated pathogenesis. Disease onset is most commonly marked by recurrent fevers, irritability, and developmental regression in the 1st year of life. A stable phase characterized by severe spastic quadriparesis and cognitive deficit follows.

Clinical spectrum of 4H leukodystrophy caused by POLR3A and POLR3B mutations.

Objective: To study the clinical and radiologic spectrum and genotype-phenotype correlation of 4H (hypomyelination, hypodontia, hypogonadotropic hypogonadism) leukodystrophy caused by mutations in POLR3A or POLR3B.

Methods: We performed a multinational cross-sectional observational study of the clinical, radiologic, and molecular characteristics of 105 mutation-proven cases.

Results: The majority of patients presented before 6 years with gross motor delay or regression.

TUBB4A de novo mutations cause isolated hypomyelination.

Objective: We present a series of unrelated patients with isolated hypomyelination, with or without mild cerebellar atrophy, and de novo TUBB4A mutations.

Methods: Patients in 2 large institutional review board-approved leukodystrophy bioregistries at Children's National Medical Center and Montreal Children's Hospital with similar MRI features had whole-exome sequencing performed. MRIs and clinical information were reviewed.

A homozygous mutation in the NDUFS1 gene presents with a mild cavitating leukoencephalopathy.

We report a case of mild cavitating leukoencephalopathy associated with a homozygous c.755A > G (p.Asp252Gly) NDUFS1 mutation in a 7-year old boy.

Mutations in POLR3A and POLR3B are a major cause of hypomyelinating leukodystrophies with or without dental abnormalities and/or hypogonadotropic hypogonadism.

Background: Leukodystrophies are a heterogeneous group of inherited neurodegenerative disorders characterised by abnormal central nervous system white matter. Mutations in POLR3A and POLR3B genes were recently reported to cause four clinically overlapping hypomyelinating leukodystrophy phenotypes. Our aim was to investigate the presence and frequency of POLR3A and POLR3B mutations in patients with genetically unexplained hypomyelinating leukodystrophies with typical clinical and/or radiologic features of Pol III-related leukodystrophies.

A novel genome-based approach correlates TMPRSS3 overexpression in ovarian cancer with DNA hypomethylation.

Objective: In an attempt to analyze more profoundly aberrant DNA hypomethylation in epithelial ovarian cancer (EOC), we applied a novel genome-based approach which includes expression profiling following pharmacologic stimulation of DNA methylation with the methyl donor S-adenosyl-l-methionine (SAM).

Methods: Four different EOC cell lines (OVCAR3, SKOV3, TOV21 and TOV112) were treated with SAM, and gene expression profiling was performed in SAM-treated and control EOC cells. Genes, downregulated upon SAM treatment were considered as potentially hypomethylated in EOC.