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Genetically determined leukoencephalopathies comprise a group of rare inherited white matter disorders. The majority are progressive diseases resulting in early death. We performed a cross-sectional pilot study including 55 parents from 36 families to assess the level of stress experienced by parents of patients with genetically determined leukoencephalopathies, aged 1 month to 12 years. Thirty-four mothers and 21 fathers completed the Parenting Stress Index–4th Edition. One demographic questionnaire was completed per family. Detailed clinical data was gathered on all patients. Statistical analysis was performed with total stress percentile score as the primary outcome. Mothers and fathers had significantly higher stress levels compared with the normative sample; 20% of parents had high levels of stress whereas 11% had clinically significant levels of stress. Mothers and fathers had comparable total stress percentile scores. We identified pediatric behavioral difficulties and gross motor function to be factors influencing stress in mothers. Our study is the first to examine parental stress in this population and highlights the need for parental support early in the disease course. In this pilot study, we demonstrated that using the Parenting Stress Index–4th Edition to assess stress levels in parents of patients with genetically determined leukoencephalopathies is feasible, leads to valuable and actionable results, and should be used in larger, prospective studies.

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. Methods A retrospective chart review was performed in a cohort of 20 patients for whom videos of a standardized neurological examination were available. Patients were recruited at the Montreal Children's Hospital of the McGill University Health Center and the Myelin Disorders Bioregistry Project. Families were consented at the initial assessment and the following data was recorded: age and symptoms at clinical presentation, investigations, causal gene and mutation(s), type and severity of dystonia, and treatment response when needed. Standardized examination videos were reviewed by three independent reviewers and scored using the Global Dystonia Scale. Results 10 males and 10 females were included in this study; 12/20 had POLR3A mutations, while 8/20 had POLR3B mutations; 19/20 patients had documented dystonia, with 3/19 requiring therapy. There was a good response in two patients to a single agent, and a poor response in one patient to three agents; the majority had mild-to-moderate multifocal dystonia without a functional impact. Conclusions Dystonia is a common, yet underdiagnosed, slowly progressive manifestation of POLR3-related leukodystrophy, and in most cases has limited-to-no functional impact. When treatment is needed, good response to typically used medication may occur. Further studies are needed to assess evolution of dystonia over time, patients' functional outcome, and response to therapy (when needed).

Summary 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 LSM7 were uncovered in two unrelated individuals, one with a leukodystrophy and the other who died in utero. LSM7 is part of the two principle LSM protein complexes in eukaryotes, namely LSM1-7 and LSM2-8. Here, we investigate the molecular and functional outcomes of these LSM7 biallelic variants in vitro and in vivo. Affinity purification-mass spectrometry of the LSM7 variants showed defects in the assembly of both LSM complexes. Lsm7 knockdown in zebrafish led to central nervous system defects, including impaired oligodendrocyte development and motor behavior. Our findings demonstrate that variants in LSM7 cause misassembly of the LSM complexes, impair neurodevelopment of the zebrafish, and may be implicated in human disease. The identification of more affected individuals is needed before the molecular mechanisms of mRNA decay and splicing regulation are added to the categories of biological dysfunctions implicated in leukodystrophies, neurodevelopmental and/or neurodegenerative diseases., Derksen et al. use molecular and functional studies to demonstrate that variants in LSM7 lead to defects in the assembly of LSM complexes, impair neurodevelopment in zebrafish, and might be implicated in human disease.

Context 4H or POLR3-related leukodystrophy is an autosomal recessive disorder typically characterized by hypomyelination, hypodontia, and hypogonadotropic hypogonadism, caused by biallelic pathogenic variants in POLR3A, POLR3B, POLR1C, and POLR3K. The endocrine and growth abnormalities associated with this disorder have not been thoroughly investigated to date. Objective To systematically characterize endocrine abnormalities of patients with 4H leukodystrophy. Design An international cross-sectional study was performed on 150 patients with genetically confirmed 4H leukodystrophy between 2015 and 2016. Endocrine and growth abnormalities were evaluated, and neurological and other non-neurological features were reviewed. Potential genotype/phenotype associations were also investigated. Setting This was a multicenter retrospective study using information collected from 3 predominant centers. Patients A total of 150 patients with 4H leukodystrophy and pathogenic variants in POLR3A, POLR3B, or POLR1C were included. Main Outcome Measures Variables used to evaluate endocrine and growth abnormalities included pubertal history, hormone levels (estradiol, testosterone, stimulated LH and FSH, stimulated GH, IGF-I, prolactin, ACTH, cortisol, TSH, and T4), and height and head circumference charts. Results The most common endocrine abnormalities were delayed puberty (57/74; 77% overall, 64% in males, 89% in females) and short stature (57/93; 61%), when evaluated according to physician assessment. Abnormal thyroid function was reported in 22% (13/59) of patients. Conclusions Our results confirm pubertal abnormalities and short stature are the most common endocrine features seen in 4H leukodystrophy. However, we noted that endocrine abnormalities are typically underinvestigated in this patient population. A prospective study is required to formulate evidence-based recommendations for management of the endocrine manifestations of this disorder., Canadian Institutes of Health Research [201610PJT-377869, MOP-G2-341146-159133-BRIDG]; Fondation Les Amis d'Elliot; Leuco-Action; Fondation Lueur d'Espoir pour Ayden; Fondation le Tout pour Loo; Reseau de Medecine Genetique Appliquee of the Fonds de Recherche du Quebec-Sante; Compute Canada; Fonds de Recherche du Quebec en Sante (FRQS) Doctoral Scholarship; Fondation du Grand defi Pierre Lavoie Doctoral Scholarship; McGill Faculty of Medicine F. S.B. Miller Fellowship; Research Institute of the McGill University Health Centre Desjardins Studentship in Child Health Research; Directorate of Higher Education Overseas Scholarship-Dikti Scholarship, Ministry of National Education, Republic of Indonesia; CIHR [201603PJT-148695]; BC Children's Hospital Foundation through its intramural Investigator Grant Award Program (IGAP); National Institute for Neurological Disorders and Stroke [R01NS082094]; Jakob Kamens Chair in Translational Neurotherapeutics; Fonds de Recherche du Quebec-Sante (FRQS); Canadian Institutes of Health Research; European Reference Network for Rare Neurological Disorders (ERN-RND) [739510], This study was supported by grants from the Canadian Institutes of Health Research (201610PJT-377869, MOP-G2-341146-159133-BRIDG), Fondation Les Amis d'Elliot, Leuco-Action, Fondation Lueur d'Espoir pour Ayden, Fondation le Tout pour Loo, and Reseau de Medecine Genetique Appliquee of the Fonds de Recherche du Quebec-Sante to G. Bernard. This research was enabled in part by support provided by Compute Canada (www.computecanada.ca).S.Perrier is supported by the Fonds de Recherche du Quebec en Sante (FRQS) Doctoral Scholarship, the Fondation du Grand defi Pierre Lavoie Doctoral Scholarship, the McGill Faculty of Medicine F. S.B. Miller Fellowship, and the Research Institute of the McGill University Health Centre Desjardins Studentship in Child Health Research. F. K.C. is a recipient of the Directorate of Higher Education Overseas Scholarship-Dikti Scholarship, Ministry of National Education, Republic of Indonesia. W.T. G. received funding from the CIHR (201603PJT-148695) and is supported by the BC Children's Hospital Foundation through its intramural Investigator Grant Award Program (IGAP). B.L. F. was supported by the National Institute for Neurological Disorders and Stroke (R01NS082094). A.V. receives funding from the Jakob Kamens Chair in Translational Neurotherapeutics. G. Bernard has received a Research Scholar Junior 1 award from the Fonds de Recherche du Quebec-Sante (FRQS) (2012-2016) and the New Investigator Salary Award from the Canadian Institutes of Health Research (2017-2022). I.K.M., M. Synofzik, D. Tonduti, B.P.v.d.W., M.S. V.d.K., and N.I.W. are members of the European Reference Network for Rare Neurological Disorders (ERN-RND), project ID 739510.

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. Here, we report the first French-Canadian patient with a novel frameshift AIMP1 homozygous mutation (c.191_192delAA, p.Gln64Argfs*25), resulting in a severe neurodegenerative phenotype. We review and discuss the phenotypic spectrum associated with AIMP1 pathogenic variants.

Summary: 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 LSM7 were uncovered in two unrelated individuals, one with a leukodystrophy and the other who died in utero. LSM7 is part of the two principle LSM protein complexes in eukaryotes, namely LSM1-7 and LSM2-8. Here, we investigate the molecular and functional outcomes of these LSM7 biallelic variants in vitro and in vivo. Affinity purification-mass spectrometry of the LSM7 variants showed defects in the assembly of both LSM complexes. Lsm7 knockdown in zebrafish led to central nervous system defects, including impaired oligodendrocyte development and motor behavior. Our findings demonstrate that variants in LSM7 cause misassembly of the LSM complexes, impair neurodevelopment of the zebrafish, and may be implicated in human disease. The identification of more affected individuals is needed before the molecular mechanisms of mRNA decay and splicing regulation are added to the categories of biological dysfunctions implicated in leukodystrophies, neurodevelopmental and/or neurodegenerative diseases.

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. Here, we report seven patients from five unrelated families with five different biallelic missense variants in VARS. Subjects present with a range of global developmental delay, epileptic encephalopathy and primary or progressive microcephaly. Longitudinal assessment demonstrates progressive cortical atrophy and white matter volume loss. Variants map to the VARS tRNA binding domain and adjacent to the anticodon domain, and disrupt highly conserved residues. Patient primary cells show intact VARS protein but reduced enzymatic activity, suggesting partial loss of function. The implication of VARS in pediatric neurodegeneration broadens the spectrum of human diseases due to mutations in tRNA synthetase genes., Valyl-tRNA synthetase (VARS) charges valyl-tRNA with the amino acid valine, required for translation. Here, the authors describe a progressive epileptic encephalopathy in individuals from five families carrying biallelic mutations in the VARS gene that leave the enzyme activity partially intact.

ObjectiveTo expand the phenotypic spectrum of severity of POLR3-related leukodystrophy and identify genotype-phenotype correlations through study of patients with extremely severe phenotypes.MethodsWe 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.ResultsEach patient presented between 1 and 3 months of age with failure to thrive, severe dysphagia, and developmental delay. Four of the 6 children died before age 3 years. MRI of all patients revealed a novel pattern with atypical characteristics, including progressive basal ganglia and thalami abnormalities. Neuropathologic studies revealed patchy areas of decreased myelin in the cerebral hemispheres, cerebellum, brainstem, and spinal cord, with astrocytic gliosis in the white matter and microglial activation. Cellular vacuolization was observed in the thalamus and basal ganglia, and neuronal loss was evident in the putamen and caudate. Genotypic similarities were also present between all 6 patients, with one allele containing a POLR3A variant causing a premature stop codon and the other containing a specific intronic splicing variant (c.1771-7C>G), which produces 2 aberrant transcripts along with some wild-type transcript.ConclusionsWe describe genotype-phenotype correlations at the extreme end of severity of the POLR3-related leukodystrophy spectrum and shed light on the complex disease pathophysiology.

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. EPRS is a bifunctional aminoacyl-tRNA synthetase that catalyzes the aminoacylation of glutamic acid and proline tRNA species. It is a subunit of a large multisynthetase complex composed of eight aminoacyl-tRNA synthetases and its three interacting proteins. In total, five different EPRS mutations were identified. The p.Pro1115Arg variation did not affect the assembly of the multisynthetase complex (MSC) as monitored by affinity purification-mass spectrometry. However, immunoblot analyses on protein extracts from fibroblasts of the two affected individuals sharing the p.Pro1115Arg variant showed reduced EPRS amounts. EPRS activity was reduced in one affected individual's lymphoblasts and in a purified recombinant protein model. Interestingly, two other cytoplasmic aminoacyl-tRNA synthetases have previously been implicated in hypomyelinating leukodystrophies bearing clinical and radiological similarities to those in the individuals we studied. We therefore hypothesized that leukodystrophies caused by mutations in genes encoding cytoplasmic aminoacyl-tRNA synthetases share a common underlying mechanism, such as reduced protein availability, abnormal assembly of the multisynthetase complex, and/or abnormal aminoacylation, all resulting in reduced translation capacity and insufficient myelin deposition in the developing brain.

The diagnosis of 4H leukodystrophy (hypomyelination, hypogonadotropic hypogonadism, and hypodontia) is based on clinical findings and magnetic resonance imaging (MRI). Recently, mutations of the genes encoding Pol III (RNA polymerase III) subunit A (POLR3A) and subunit B (POL3B) have been identified as the genetic causes of hypomyelination. We describe two Polish female siblings aged 5 and 10 years with compound heterozygous mutations in POLR3B. They both presented with similar clinical symptoms and MRI findings presenting as 4H leukodystrophy, and the association of polymicrogyria and cataract. According to our observation in young children with the absence of hypogonadotropic hypogonadism, brain MRI pattern is very essential in proper early diagnosis of 4H leukodystrophy. All clinical and radiological results are of course helpful, however genetic conformation is always necessary.

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. POLR3A and POLR3B were sequenced. A compound heterozygote mutation in POLR3B was found in only one patient. Additional investigations allowed a definitive diagnosis in 10 patients. Conclusion Mutations in POLR3A or POLR3B are rare in patients with unclassified hypomyelination, and alternative diagnoses should be considered first

ObjectiveTo determine the clinical, radiologic, and molecular characteristics of RNA polymerase III-related leukodystrophy (POLR3-HLD) caused by biallelic POLR1C pathogenic variants.MethodsA 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 POLR1C. Brain MRI studies were reviewed.ResultsFourteen female and 9 male patients aged 7 days to 23 years were included in the study. Most participants presented early in life (birth to 6 years), and motor deterioration was seen during childhood. A notable proportion of patients required a wheelchair before adolescence, suggesting a more severe phenotype than previously described in POLR3-HLD. Dental, ocular, and endocrine features were not invariably present (70%, 50%, and 50%, respectively). Five patients (22%) had a combination of hypomyelinating leukodystrophy and abnormal craniofacial development, including 1 individual with clear Treacher Collins syndrome (TCS) features. Brain MRI revealed hypomyelination in all cases, often with areas of pronounced T2 hyperintensity corresponding to T1 hypointensity of the white matter. Twenty-nine different pathogenic variants (including 12 new disease-causing variants) in POLR1C were identified.ConclusionsThis study provides a comprehensive description of POLR3-HLD caused by biallelic POLR1C pathogenic variants based on the largest cohort of patients to date. These results suggest distinct characteristics of POLR1C-related disorder, with a spectrum of clinical involvement characterized by hypomyelinating leukodystrophy with or without abnormal craniofacial development reminiscent of TCS.

Background: Biallelic variants in POLR1C are associated with POLR3-related leukodystrophy (POLR3-HLD), or 4H leukodystrophy (Hypomyelination, Hypodontia, Hypogonadotropic Hypogonadism), and Treacher Collins syndrome (TCS). The clinical spectrum of POLR3-HLD caused by variants in this gene has not been described. Methods: A cross-sectional observational study involving 25 centers worldwide was conducted between 2016 and 2018. The clinical, radiologic and molecular features of 23 unreported and previously reported cases of POLR3-HLD caused by POLR1C variants were reviewed. Results: Most participants presented between birth and age 6 years with motor difficulties. Neurological deterioration was seen during childhood, suggesting a more severe phenotype than previously described. The dental, ocular and endocrine features often seen in POLR3-HLD were not invariably present. Five patients (22%) had a combination of hypomyelinating leukodystrophy and abnormal craniofacial development, including one individual with clear TCS features. Several cases did not exhibit all the typical radiologic characteristics of POLR3-HLD. A total of 29 different pathogenic variants in POLR1C were identified, including 13 new disease-causing variants. Conclusions: Based on the largest cohort of patients to date, these results suggest novel characteristics of POLR1C-related disorder, with a spectrum of clinical involvement characterized by hypomyelinating leukodystrophy with or without abnormal craniofacial development reminiscent of TCS.

WOS: 000375050100016, PubMed ID: 27029625, 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., diffuse hypomyelination associated with relative T2 hypointensity of the ventrolateral thalamus, globus pallidus, optic radiation, corticospinal tract at the level of the internal capsule, and dentate nucleus, cerebellar atrophy, and thinning of the corpus callosum.Results:Eight patients were identified: 6 carried mutations in POLR3A and 2 in POLR3B. We identified 2 novel MRI patterns: 4 participants presented a selective involvement of the corticospinal tracts, specifically at the level of the posterior limbs of the internal capsules; 4 patients presented moderate to severe cerebellar atrophy. Incomplete hypomyelination was observed in 5 participants.Conclusion:Diffuse hypomyelination is not an obligatory feature of POLR3-related disorders. Two distinct patterns, selective involvement of the corticospinal tracts and cerebellar atrophy, are added to the MRI presentation of POLR3-related disorders., Fonds de recherche du Quebec-Sante (FRQS); Fondation Monaco; Directorate of Higher Education Overseas Scholarship-Dikti Scholarship, Ministry of National Education, Republic of Indonesia; Fonds de Recherche du Quebec en Sante (FRQS); ZonMw (TOP grant) [91211005]; Canadian Institute for Health ResearchCanadian Institutes of Health Research (CIHR) [MOP-G-287547]; Reseau de Medecine Genetique Appliquee du FRQS; BMBF through the Juniorverbund in der Systemmedizin "mitOmics"Federal Ministry of Education & Research (BMBF) [FKZ 01ZX1405C], R.L.P. has received a Doctoral Award from the Fonds de recherche du Quebec-Sante (FRQS) and has been supported by the Fondation Monaco. F.K.C. is a recipient of the Directorate of Higher Education Overseas Scholarship-Dikti Scholarship, Ministry of National Education, Republic of Indonesia. G.B. has received a Research Scholar Junior 1 award from the Fonds de Recherche du Quebec en Sante (FRQS). N.I.W. and M.S.v.d.K. are supported by ZonMw (TOP grant 91211005). This work was supported by Canadian Institute for Health Research grant MOP-G-287547 and the Reseau de Medecine Genetique Appliquee du FRQS to G.B. T.H. was supported by the BMBF through the Juniorverbund in der Systemmedizin "mitOmics" (FKZ 01ZX1405C).

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. DNA hypomethylation was independently validated in ovarian tumor and control tissues by bisulfite sequencing PCR (BSP). Results Among the genes identified, one of particular interest was the type II serine protease TMPRSS3 gene variants A and D (TMPRSS3-A/D), previously recognized as overexpressed in EOC and representing potential EOC therapeutic targets. Consecutive BSP analysis demonstrated that the common putative promoter region of the TMPRSS3-A/D gene variants was significantly hypomethylated in high-grade serous EOC tumors, compared to low-malignant potential ovarian tumors and normal ovarian tissue. Conclusions Our data imply that TMPRSS3-A/D overexpression in EOC is probably due to hypomethylation of their control region thus indicating that TMPRSS3-A/D variants could also represent novel molecular targets for epigenetic therapy of late stages of the disease. Our results also suggest that the frequently observed upregulation of different members of the type II serine proteases gene family in advanced cancer could be due to aberrant DNA hypomethylation. Furthermore, our study introduces a promising discovery approach that could be used for the identification of hypomethylated genes in different experimental cell models.

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. These are the first reports of long deletions causing POLR3-related leukodystrophy, suggesting that deletions and duplications in POLR3A or POLR3B should be investigated in patients with a compatible phenotype, especially if one pathogenic variant has been identified.

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., Some RNA polymerase (POLR) 3-related leukodystrophy cases do not have the causal mutations in POLR3A and POLR3B. Here, by exome sequencing, the authors identify recessive mutations in POLR1C, a gene encoding a shared POLR1 and POLR3 subunit, impairing assembly and nuclear import of POLR3, but not POLR1.

Aicardi-Goutieres 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. Brain calcifications, leukoencephalopathy, and cerebral atrophy are the radiological hallmarks of AGS and often show progression over time. We present an atypical patient with late- onset AGS characterized by spastic paraparesis and a leukoencephalopathy that markedly improved during follow-up, demonstrating a nonprogressive disease course and the exceptional amelioration of the white matter abnormalities.

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 Children9s National Medical Center and Montreal Children9s Hospital with similar MRI features had whole-exome sequencing performed. MRIs and clinical information were reviewed. Results: Five patients who presented with hypomyelination without the classic basal ganglia abnormalities were found to have novel TUBB4A mutations through whole-exome sequencing. Clinical and imaging characteristics were reviewed suggesting a spectrum of clinical manifestations. Conclusion: Hypomyelinating leukodystrophies remain a diagnostic challenge with a large percentage of unresolved cases. This finding expands the phenotype of TUBB4A -related hypomyelinating conditions beyond hypomyelination with atrophy of the basal ganglia and cerebellum. TUBB4A mutation screening should be considered in cases of isolated hypomyelination or hypomyelination with nonspecific cerebellar atrophy.

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. Biochemical analysis confirmed an isolated reduction in complex I activity. Magnetic resonance imaging of the brain showed a diffuse cystic leukoencephalopathy with the involvement of the corpus callosum and sparing of the gray matter. The clinical course was marked by an acute presentation of neurological deficits at 24 months followed by recurrent episodes of mild neurological deterioration, subsequent remissions, and prolonged periods of stability. This is one of the mildest known clinical presentations of complex I deficiency secondary to mutations in NDUFS1, expanding the clinical spectrum and natural history of this disorder. Consideration of clinical variability needs to be taken into account in patient management and family counseling. © 2014 Springer-Verlag.

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. Methods The entire coding region and the flanking exon/intron boundaries of POLR3A and/or POLR3B genes were amplified and sequenced in 14 patients. Results Recessive mutations in POLR3A or POLR3B were uncovered in all 14 patients. Eight novel mutations were identified in POLR3A : six missenses, one nonsense, and one frameshift mutation. Seven patients carried compound heterozygous mutations in POLR3B , of whom six shared the common mutation in exon 15 (p.V523E). Seven novel mutations were identified in POLR3B : four missenses, two splice sites, and one intronic mutation. Conclusions To date, our group has described 37 patients, of whom 27 have mutations in POLR3A and 10 in POLR3B, respectively. Altogether, our results further support the proposal that POLR3A and POLR3B mutations are a major cause of hypomyelinating leukodystrophies and suggest that POLR3A mutations are more frequent.