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Mitochondrial leukodystrophies constitute a group of different conditions presenting with a wide range of clinical presentation but with some shared neuroradiological features. Genetic defects in NUBPL have been recognized as cause of a pediatric onset mitochondrial leukodystrophy characterized by onset at the end of the first year of life with motor delay or regression and cerebellar signs, followed by progressive spasticity. Early magnetic resonance imagings (MRIs) show white matter abnormalities with predominant involvement of frontoparietal regions and corpus callosum. A striking cerebellar involvement is usually observed. Later MRIs show spontaneous improvement of white matter abnormalities but worsening of the cerebellar involvement evolving to global atrophy and progressive involvement of brainstem. After the 7 cases initially described, 11 more subjects were reported. Some of them were similar to patients from the original series while few others broadened the phenotypic spectrum. We performed a literature review and report on a new patient who further expand the spectrum of NUBPL-related leukodystrophy. With our study we confirm that the association of cerebral white matter and cerebellar cortex abnormalities is a feature commonly observed in early stages of the disease but beside the original and so far prevalent presentation, there are also uncommon phenotypes: clinical onset can be earlier and more severe than previously thought and signs of extraneurological involvement can be observed. Brain white matter can be diffusely abnormal without anteroposterior gradient, can progressively worsen, and cystic degeneration can be present. Thalami can be involved. Basal ganglia can also become involved during disease evolution.

Loss of function of the astrocyte membrane protein MLC1 is the primary genetic cause of the rare white matter disease Megalencephalic Leukoencephalopathy with subcortical Cysts (MLC), which is characterized by disrupted brain ion and water homeostasis. MLC1 is prominently present around fluid barriers in the brain, such as in astrocyte endfeet contacting blood vessels and in processes contacting the meninges. Whether the protein plays a role in other astrocyte domains is unknown. Here, we show that MLC1 is present in distal astrocyte processes, also known as perisynaptic astrocyte processes (PAPs) or astrocyte leaflets, which closely interact with excitatory synapses in the CA1 region of the hippocampus. We find that the PAP tip extending toward excitatory synapses is shortened in Mlc1-null mice. This affects glutamatergic synaptic transmission, resulting in a reduced rate of spontaneous release events and slower glutamate re-uptake under challenging conditions. Moreover, while PAPs in wildtype mice retract from the synapse upon fear conditioning, we reveal that this structural plasticity is disturbed in Mlc1-null mice, where PAPs are already shorter. Finally, Mlc1-null mice show reduced contextual fear memory. In conclusion, our study uncovers an unexpected role for the astrocyte protein MLC1 in regulating the structure of PAPs. Loss of MLC1 alters excitatory synaptic transmission, prevents normal PAP remodeling induced by fear conditioning and disrupts contextual fear memory expression. Thus, MLC1 is a new player in the regulation of astrocyte-synapse interactions.

Tissue-resident macrophages of the brain, including microglia, are implicated in the pathogenesis of various CNS disorders and are possible therapeutic targets by their chemical depletion or replenishment by hematopoietic stem cell therapy. Nevertheless, a comprehensive understanding of microglial function and the consequences of microglial depletion in the human brain is lacking. In human disease, heterozygous variants in CSF1R, encoding the Colony-stimulating factor 1 receptor, can lead to adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) possibly caused by microglial depletion. Here, we investigate the effects of ALSP-causing CSF1R variants on microglia and explore the consequences of microglial depletion in the brain. In intermediate- and late-stage ALSP post-mortem brain, we establish that there is an overall loss of homeostatic microglia and that this is predominantly seen in the white matter. By introducing ALSP-causing missense variants into the zebrafish genomic csf1ra locus, we show that these variants act dominant negatively on the number of microglia in vertebrate brain development. Transcriptomics and proteomics on relatively spared ALSP brain tissue validated a downregulation of microglia-associated genes and revealed elevated astrocytic proteins, possibly suggesting involvement of astrocytes in early pathogenesis. Indeed, neuropathological analysis and in vivo imaging of csf1r zebrafish models showed an astrocytic phenotype associated with enhanced, possibly compensatory, endocytosis. Together, our findings indicate that microglial depletion in zebrafish and human disease, likely as a consequence of dominant-acting pathogenic CSF1R variants, correlates with altered astrocytes. These findings underscore the unique opportunity CSF1R variants provide to gain insight into the roles of microglia in the human brain, and the need to further investigate how microglia, astrocytes, and their interactions contribute to white matter homeostasis.

Brain oedema is a life-threatening complication of various neurological conditions. Understanding molecular mechanisms of brain volume regulation is critical for therapy development. Unique insight comes from monogenic diseases characterized by chronic brain oedema, of which megalencephalic leukoencephalopathy with subcortical cysts (MLC) is the prototype. Variants in MLC1 or GLIALCAM, encoding proteins involved in astrocyte volume regulation, are the main causes of MLC. In some patients the genetic cause remains unknown. We performed genetic studies to identify novel gene variants in MLC patients, diagnosed by clinical and MRI features, without MLC1 or GLIALCAM variants. We determined subcellular localization of the related novel proteins in cells and in human brain tissue. We investigated functional consequences of the newly identified variants on volume regulation pathways using cell volume measurements, biochemical analysis and electrophysiology. We identified a novel homozygous variant in AQP4, encoding the water channel aquaporin-4, in two siblings, and two de novo heterozygous variants in GPRC5B, encoding the orphan G protein-coupled receptor GPRC5B, in three unrelated patients. The AQP4 variant disrupts membrane localization and thereby channel function. GPRC5B, like MLC1, GlialCAM and aquaporin-4, is expressed in astrocyte endfeet in human brain. Cell volume regulation is disrupted in GPRC5B patient-derived lymphoblasts. GPRC5B functionally interacts with ion channels involved in astrocyte volume regulation. In conclusion, we identify aquaporin-4 and GPRC5B as old and new players in genetic brain oedema. Our findings shed light on the protein complex involved in astrocyte volume regulation and identify GPRC5B as novel potentially druggable target for treating brain oedema.

Astrocytes regulate central nervous system development, maintain its homeostasis and orchestrate repair upon injury. Emerging evidence support functional specialization of astroglia, both between and within brain regions. Different subtypes of gray matter astrocytes have been identified, yet molecular and functional diversity of white matter astrocytes remains largely unexplored. Nonetheless, their important and diverse roles in maintaining white matter integrity and function are well recognized. Compelling evidence indicate that impairment of normal astrocytic function and their response to injury contribute to a wide variety of diseases, including white matter disorders. In this review, we highlight our current understanding of astrocyte heterogeneity in the white matter of the mammalian brain and how an interplay between developmental origins and local environmental cues contribute to astroglial diversification. In addition, we discuss whether, and if so, how, heterogeneous astrocytes could contribute to white matter function in health and disease and focus on the sparse human research data available. We highlight four leukodystrophies primarily due to astrocytic dysfunction, the so-called astrocytopathies. Insight into the role of astroglial heterogeneity in both healthy and diseased white matter may provide new avenues for therapies aimed at promoting repair and restoring normal white matter function.

Metachromatic leukodystrophy is a lethal metabolic leukodystrophy, with emerging treatments for early disease stages. Biomarkers to measure disease activity are required for clinical assessment and treatment follow-up. This retrospective study compared neurofilament light chain and glial fibrillary acidic protein (GFAP) levels in CSF (n = 11) and blood (n = 92) samples of 40 patients with metachromatic leukodystrophy (aged 0–42 years) with 38 neurologically healthy children (aged 0–17 years) and 38 healthy adults (aged 18–45 years), and analysed the associations between these levels with clinical phenotype and disease evolution in untreated and transplanted patients. Metachromatic leukodystrophy subtype was determined based on the (expected) age of symptom onset. Disease activity was assessed by measuring gross motor function deterioration and brain MRI. Longitudinal analyses with measurements up to 23 years after diagnosis were performed using linear mixed models. CSF and blood neurofilament light chain and GFAP levels in paediatric controls were negatively associated with age (all P < 0.001). Blood neurofilament light chain level at diagnosis (median, interquartile range; picograms per millilitre) was significantly increased in both presymptomatic (14.7, 10.6–56.7) and symptomatic patients (136, 40.8–445) compared to controls (5.6, 4.5–7.1), and highest among patients with late-infantile (456, 201–854) or early-juvenile metachromatic leukodystrophy (291.0, 104–445) and those ineligible for treatment based on best practice (291, 57.4–472). GFAP level (median, interquartile range; picogram per millilitre) was only increased in symptomatic patients (591, 224–1150) compared to controls (119, 78.2–338) and not significantly associated with treatment eligibility (P = 0.093). Higher blood neurofilament light chain and GFAP levels at diagnosis were associated with rapid disease progression in late-infantile (P = 0.006 and P = 0.051, respectively) and early-juvenile patients (P = 0.048 and P = 0.039, respectively). Finally, blood neurofilament light chain and GFAP levels decreased during follow-up in untreated and transplanted patients but remained elevated compared with controls. Only neurofilament light chain levels were associated with MRI deterioration (P < 0.001). This study indicates that both proteins may be considered as non-invasive biomarkers for clinical phenotype and disease stage at clinical assessment, and that neurofilament light chain might enable neurologists to make better informed treatment decisions. In addition, neurofilament light chain holds promise assessing treatment response. Importantly, both biomarkers require paediatric reference values, given that their levels first decrease before increasing with advancing age.

Objective: Metachromatic leukodystrophy is a lysosomal storage disease caused by deficient arylsulfatase A. It is characterized by progressive demyelination and thus mainly affects the white matter. Hematopoietic stem cell transplantation may stabilize and improve white matter damage, yet some patients deteriorate despite successfully treated leukodystrophy. We hypothesized that post-treatment decline in metachromatic leukodystrophy might be caused by gray matter pathology. Methods: Three metachromatic leukodystrophy patients treated with hematopoietic stem cell transplantation with a progressive clinical course despite stable white matter pathology were clinically and radiologically analyzed. Longitudinal volumetric MRI was used to quantify atrophy. We also examined histopathology in three other patients deceased after treatment and compared them with six untreated patients. Results: The three clinically progressive patients developed cognitive and motor deterioration after transplantation, despite stable mild white matter abnormalities on MRI. Volumetric MRI identified cerebral and thalamus atrophy in these patients, and cerebellar atrophy in two. Histopathology showed that in brain tissue of transplanted patients, arylsulfatase A expressing macrophages were clearly present in the white matter, but absent in the cortex. Arylsulfatase A expression within patient thalamic neurons was lower than in controls, the same was found in transplanted patients. Interpretation: Neurological deterioration may occur after hematopoietic stem cell transplantation in metachromatic leukodystrophy despite successfully treated leukodystrophy. MRI shows gray matter atrophy, and histological data demonstrate absence of donor cells in gray matter structures. These findings point to a clinically relevant gray matter component of metachromatic leukodystrophy, which does not seem sufficiently affected by transplantation.

Objective: Mucopolysaccharidosis type IIIA (MPSIIIA) caused by recessive SGSH variants results in sulfamidase deficiency, leading to neurocognitive decline and death. No disease-modifying therapy is available. The AAVance gene therapy trial investigates AAVrh.10 overexpressing human sulfamidase (LYS-SAF302) delivered by intracerebral injection in children with MPSIIIA. Post-treatment MRI monitoring revealed lesions around injection sites. Investigations were initiated in one patient to determine the cause. Methods: Clinical and MRI details were reviewed. Stereotactic needle biopsies of a lesion were performed; blood and CSF were sampled. All samples were used for viral studies. Immunohistochemistry, electron microscopy, and transcriptome analysis were performed on brain tissue of the patient and various controls. Results: MRI revealed focal lesions around injection sites with onset from 3 months after therapy, progression until 7 months post therapy with subsequent stabilization and some regression. The patient had transient slight neurological signs and is following near-normal development. No evidence of viral or immunological/inflammatory cause was found. Immunohistochemistry showed immature oligodendrocytes and astrocytes, oligodendrocyte apoptosis, strong intracellular and extracellular sulfamidase expression and hardly detectable intracellular or extracellular heparan sulfate. No activation of the unfolded protein response was found. Interpretation: Results suggest that intracerebral gene therapy with local sulfamidase overexpression leads to dysfunction of transduced cells close to injection sites, with extracellular spilling of lysosomal enzymes. This alters extracellular matrix composition, depletes heparan sulfate, impairs astrocyte and oligodendrocyte function, and causes cystic white matter degeneration at the site of highest gene expression. The AAVance trial results will reveal the potential benefit–risk ratio of this therapy.

The enzyme ubiquitin-like modifier activating enzyme 5 (UBA5) plays an important role in activating ubiquitin-fold modifier 1 (UFM1) and its associated cascade. UFM1 is widely expressed and known to facilitate the post-translational modification of proteins. Variants in UBA5 and UFM1 are involved in neurodevelopmental disorders with early-onset epileptic encephalopathy as a frequently seen disease manifestation. Using whole exome sequencing, we detected a homozygous UBA5 variant (c.895C > T p. [Pro299Ser]) in a patient with severe global developmental delay and epilepsy, the latter from the age of 4 years. Magnetic resonance imaging showed hypomyelination with atrophy and T2 hyperintensity of the thalamus. Histology of the sural nerve showed axonal neuropathy with decreased myelin. Functional analyses confirmed the effect of the Pro299Ser variant on UBA5 protein function, showing 58% residual protein activity. Our findings indicate that the epilepsy currently associated with UBA5 variants may present later in life than previously thought, and that radiological signs include hypomyelination and thalamic involvement. The data also reinforce recently reported associations between UBA5 variants and peripheral neuropathy.

Objectives: Metachromatic leukodystrophy (MLD) has characteristic white matter (WM) changes on brain MRI, which often trigger biochemical and genetic confirmation of the diagnosis. In early or pre-symptomatic disease stages, these typical MRI changes might be absent, hampering early diagnosis. This study aims to describe the characteristics of MRI WM abnormalities at diagnosis, related to clinical presentation. Methods: We retrospectively reviewed brain MRIs of MLD patients followed in 2 centers at the time of diagnosis regarding MLD MRI score and presence of tigroid pattern. In addition, MLD subtype, symptom status, CNS/PNS phenotype, motor/cognitive/mixed phenotype, and the presence of CNS symptoms were evaluated. Results: We included 104 brain MRIs from patients with late-infantile (n = 43), early-juvenile (n = 24), late-juvenile (n = 20) and adult (n = 17) onset. Involvement of the corpus callosum was a characteristic early MRI sign and was present in 71% of the symptomatic late-infantile patients, 94% of the symptomatic early-juvenile patients and 100% of the symptomatic late-juvenile and adult patients. Symptomatic early-juvenile, late-juvenile and adult patients generally had WM abnormalities on MRI suggestive of MLD. By contrast, 47% of the early-symptomatic late-infantile patients had no or only mild WM abnormalities on MRI, even in the presence of CNS symptoms including pyramidal signs. Interpretation: Patients with late-infantile MLD may have no or only mild, nonspecific abnormalities at brain MRI, partly suggestive of ‘delayed myelination’, even with clear clinical symptoms. This may lead to significant diagnostic delay. Knowledge of these early MRI signs (or their absence) is important for fast diagnosis.

Introduction: Vanishing white matter (VWM) is a leukodystrophy that leads to neurological dysfunction and early death. Astrocytes are indicated as therapeutic target, because of their central role in VWM pathology. Previous cell replacement therapy using primary mouse glial precursors phenotypically improved VWM mice. Aims: The aim of this study was to determine the translational potential of human stem cell-derived glial cell replacement therapy for VWM. We generated various glial cell types from human pluripotent stem cells in order to identify a human cell population that successfully ameliorates disease hallmarks of a VWM mouse model. The effects of cell grafts on motor skills and VWM brain pathology were assessed. Results: Transplantation of human glial precursor populations improved the VWM phenotype. The intrinsic properties of these cells were partially reflected by cell fate post-transplantation, but were also affected by the host microenvironment. Strikingly, the spread of transplanted cells into the white matter versus the gray matter was different when grafted into the VWM brain as compared to a healthy brain. Conclusions: Transplantation of human glial cell populations can have therapeutic effects for VWM. For further translation to the clinic, the microenvironment in the VWM patient brain should be considered as an important moderator of cell replacement therapy.

Proteostasis is essential for cellular survival and particularly important for highly specialised post-mitotic cells such as neurons. Transient reduction in protein synthesis by protein kinase R-like endoplasmic reticulum (ER) kinase (PERK)-mediated phosphorylation of eukaryotic translation initiation factor 2α (p-eIF2α) is a major proteostatic survival response during ER stress. Paradoxically, neurons are remarkably tolerant to PERK dysfunction, which suggests the existence of cell type-specific mechanisms that secure proteostatic stress resilience. Here, we demonstrate that PERK-deficient neurons, unlike other cell types, fully retain the capacity to control translation during ER stress. We observe rescaling of the ATF4 response, while the reduction in protein synthesis is fully retained. We identify two molecular pathways that jointly drive translational control in PERK-deficient neurons. Haem-regulated inhibitor (HRI) mediates p-eIF2α and the ATF4 response and is complemented by the tRNA cleaving RNase angiogenin (ANG) to reduce protein synthesis. Overall, our study elucidates an intricate back-up mechanism to ascertain translational control during ER stress in neurons that provides a mechanistic explanation for the thus far unresolved observation of neuronal resilience to proteostatic stress.

Objective: Vanishing white matter (VWM) is a leukodystrophy, characterized by stress-sensitive neurological deterioration and premature death. It is currently without curative treatment. It is caused by bi-allelic pathogenic variants in the genes encoding eukaryotic initiation factor 2B (eIF2B). eIF2B is essential for the regulation of the integrated stress response (ISR), a physiological response to cellular stress. Preclinical studies on VWM mouse models revealed that deregulated ISR is key in the pathophysiology of VWM and an effective treatment target. Guanabenz, an α2-adrenergic agonist, attenuates the ISR and has beneficial effects on VWM neuropathology. The current study aimed at elucidating guanabenz's disease-modifying potential and mechanism of action in VWM mice. Sephin1, an ISR-modulating guanabenz analog without α2-adrenergic agonistic properties, was included to separate effects on the ISR from α2-adrenergic effects. Methods: Wild-type and VWM mice were subjected to placebo, guanabenz or sephin1 treatments. Effects on clinical signs, neuropathology, and ISR deregulation were determined. Guanabenz's and sephin1's ISR-modifying effects were tested in cultured cells that expressed or lacked the α2-adrenergic receptor. Results: Guanabenz improved clinical signs, neuropathological hallmarks, and ISR regulation in VWM mice, but sephin1 did not. Guanabenz's effects on the ISR in VWM mice were not replicated in cell cultures and the contribution of α2-adrenergic effects on the deregulated ISR could therefore not be assessed. Interpretation: Guanabenz proved itself as a viable treatment option for VWM. The exact mechanism through which guanabenz exerts its ameliorating impact on VWM requires further studies. Sephin1 is not simply a guanabenz replacement without α2-adrenergic effects.

Background Vanishing white matter (VWM) is a leukodystrophy, caused by recessive mutations in eukaryotic initiation factor 2B (eIF2B)‐subunit genes (EIF2B1–EIF2B5); 80% are missense mutations. Clinical severity is highly variable, with a strong, unexplained genotype–phenotype correlation. Materials and Methods With information from a recent natural history study, we severity‐graded 97 missense mutations. Using in silico modeling, we created a new human eIF2B model structure, onto which we mapped the missense mutations. Mutated residues were assessed for location in subunits, eIF2B complex, and functional domains, and for information on biochemical activity. Results Over 50% of mutations have (ultra‐)severe phenotypic effects. About 60% affect the ε‐subunit, containing the catalytic domain, mostly with (ultra‐)severe effects. About 55% affect subunit cores, with variable clinical severity. About 36% affect subunit interfaces, mostly with severe effects. Very few mutations occur on the external eIf2B surface, perhaps because they have minor functional effects and are tolerated. One external surface mutation affects eIF2B‐substrate interaction and is associated with ultra‐severe phenotype. Conclusion Mutations that lead to (ultra‐)severe disease mostly affect amino acids with pivotal roles in complex formation and function of eIF2B. Therapies for VWM are emerging and reliable mutation‐based phenotype prediction is required for propensity score matching for trials and in the future for individualized therapy decisions., Vanishing white matter (VWM) is a clinically highly variable leukodystrophy, caused by recessive mutations in eukaryotic initiation factor 2B (eIF2B)‐subunit genes, mostly missense mutations. To gain insight into the strong genotype‐phenotype correlation, we severity‐graded 97 missense mutations using information from a clinical natural history study, created a new human eIF2B model structure by in silico modeling, and assessed mutated residues for location in subunits, eIF2B complex, and functional domains, and for information on biochemical activity. We demonstrated that mutations associated with (ultra‐)severe disease mostly affect amino acids with pivotal roles in complex formation and eIF2B function, while mutations on the external eIf2B surface are mostly associated with mild phenotypes, probably because of minor functional effects. Therapies for VWM are emerging and reliable mutation‐based phenotype prediction is required for propensity score matching for trials and individualized therapy decisions.

Objective Heterozygous NOTCH3 variants are known to cause cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), with patients typically presenting in adulthood. We describe three patients presenting at an early age with a vascular leukoencephalopathy. Genome sequencing revealed bi-allelic variants in the NOTCH3 gene. Methods Clinical records and available MRI and CT scans of three patients from two unrelated families were retrospectively reviewed. Results The patients presented at 9 to 14 months of age with developmental delay, seizures, or both. The disease course was characterized by cognitive impairment and variably recurrent strokes, migraine attacks, and seizures. MRI findings pointed at a small vessel disease, with extensive cerebral white matter abnormalities, atrophy, lacunes in the basal ganglia, microbleeds, and microcalcifications. The anterior temporal lobes were spared. Bi-allelic cysteine-sparing NOTCH3 variants in exons 1, 32, and 33 were found. Interpretation This study indicates that bi-allelic loss-of-function NOTCH3 variants may cause a vascular leukoencephalopathy, distinct from CADASIL.

BACKGROUND: X-linked adrenoleukodystrophy (ALD) is the most common genetic peroxisomal disorder with an estimated prevalence of 1:15,000. Approximately two-thirds of males with ALD manifest the inflammatory demyelinating cerebral phenotype (cALD) at some disease stage, in which focal, inflammatory lesions progress over months to years. Hematopoietic stem-cell transplantation can permanently halt cALD progression, but it is only effective if initiated early. Although most cALD lesions progress relentlessly, a subset may spontaneously arrest; subsequent reactivation of these arrested lesions has not been previously detailed.OBJECTIVE: We describe a novel arresting-relapsing variant of cALD.METHODS: Salient clinical and radiographic studies were reviewed and summarized for cALD patients with episodic deteriorations.RESULTS: We report a series of five unrelated men with spontaneously arrested cALD lesions that subsequently manifested signs of clinical and radiologic lesion progression during longitudinal follow-up. In three of five patients, functional status was too poor to attempt transplant by the time the recurrence was identified. One patient experienced reactivation followed by another period of spontaneous arrest.CONCLUSIONS: These cases emphasize the need for continued clinical and radiologic vigilance for adult men with ALD to screen for evidence of new or reactivated cALD lesions to facilitate prompt treatment evaluation.

Objective: Genome sequencing (GS) is promising for unsolved leukodystrophies, but its efficacy has not been prospectively studied. Methods: A prospective time-delayed crossover design trial of GS to assess the efficacy of GS as a first-line diagnostic tool for genetic white matter disorders took place between December 1, 2015 and September 27, 2017. Patients were randomized to receive GS immediately with concurrent standard of care (SoC) testing, or to receive SoC testing for 4 months followed by GS. Results: Thirty-four individuals were assessed at interim review. The genetic origin of 2 patient's leukoencephalopathy was resolved before randomization. Nine patients were stratified to the immediate intervention group and 23 patients to the delayed-GS arm. The efficacy of GS was significant relative to SoC in the immediate (5/9 [56%] vs 0/9 [0%]; Wild–Seber, p < 0.005) and delayed (control) arms (14/23 [61%] vs 5/23 [22%]; Wild–Seber, p < 0.005). The time to diagnosis was significantly shorter in the immediate-GS group (log-rank test, p = 0.04). The overall diagnostic efficacy of combined GS and SoC approaches was 26 of 34 (76.5%, 95% confidence interval = 58.8–89.3%) in

Biallelic variants in POLR3A cause 4H leukodystrophy, characterized by hypomyelination in combination with cerebellar and pyramidal signs and variable non-neurological manifestations. Basal ganglia are spared in 4H leukodystrophy, and dystonia is not prominent. Three patients with variants in POLR3A, an atypical presentation with dystonia, and MR involvement of putamen and caudate nucleus (striatum) and red nucleus have previously been reported. Genetic, clinical findings and 18 MRI scans from nine patients with homozygous or compound heterozygous POLR3A variants and predominant striatal changes were retrospectively reviewed in order to characterize the striatal variant of POLR3A-associated disease. Prominent extrapyramidal involvement was the predominant clinical sign in all patients. The three youngest children were severely affected with muscle hypotonia, impaired head control, and choreic movements. Presentation of the six older patients was milder. Two brothers diagnosed with juvenile parkinsonism were homozygous for the c.1771-6C > G variant in POLR3A; the other seven either carried c.1771-6C > G (n = 1) or c.1771-7C > G (n = 7) together with another variant (missense, synonymous, or intronic). Striatal T2-hyperintensity and atrophy together with involvement of the superior cerebellar peduncles were characteristic. Additional MRI findings were involvement of dentate nuclei, hila, or peridentate white matter (3, 6, and 4/9), inferior cerebellar peduncles (6/9), red nuclei (2/9), and abnormal myelination of pyramidal and visual tracts (6/9) but no frank hypomyelination. Clinical and MRI findings in patients with a striatal variant of POLR3A-related disease are distinct from 4H leukodystrophy and associated with one of two intronic variants, c.1771-6C > G or c.1771-7C > G, in combination with another POLR3A variant.

OBJECTIVE: In metachromatic leukodystrophy, a lysosomal storage disorder due to decreased arylsulfatase A activity, hematopoietic stem cell transplantation may stop brain demyelination and allow remyelination, thereby halting white matter degeneration. This is the first study to define the effects and therapeutic mechanisms of hematopoietic stem cell transplantation on brain tissue of transplanted metachromatic leukodystrophy patients.METHODS: Autopsy brain tissue was obtained from eight (two transplanted and six nontransplanted) metachromatic leukodystrophy patients, and two age-matched controls. We examined the presence of donor cells by immunohistochemistry and microscopy. In addition, we assessed myelin content, oligodendrocyte numbers, and macrophage phenotypes. An unpaired t-test, linear regression or the nonparametric Mann-Whitney U-test was performed to evaluate differences between the transplanted, nontransplanted, and control group.RESULTS: In brain tissue of transplanted patients, we found metabolically competent donor macrophages expressing arylsulfatase A distributed throughout the entire white matter. Compared to nontransplanted patients, these macrophages preferentially expressed markers of alternatively activated, anti-inflammatory cells that may support oligodendrocyte survival and differentiation. Additionally, transplanted patients showed higher numbers of oligodendrocytes and evidence for remyelination. Contrary to the current hypothesis on therapeutic mechanism of hematopoietic cell transplantation in metachromatic leukodystrophy, we detected no enzymatic cross-correction to resident astrocytes and oligodendrocytes.INTERPRETATION: In conclusion, donor macrophages are able to digest accumulated sulfatides and may play a neuroprotective role for resident oligodendrocytes, thereby enabling remyelination, albeit without evidence of cross-correction of oligo- and astroglia. These results emphasize the importance of immunomodulation in addition to the metabolic correction, which might be exploited for improved outcomes.

Contains fulltext : 220431.pdf (Publisher’s version ) (Closed access) BACKGROUND: Disordered thyroid hormone transport, due to mutations in the SLC16A2 gene encoding monocarboxylate transporter 8 (MCT8), is characterised by intellectual and motor disability resulting from cerebral hypothyroidism and chronic peripheral thyrotoxicosis. We sought to systematically assess the phenotypic characteristics and natural history of patients with MCT8 deficiency. METHODS: We did an international, multicentre, cohort study, analysing retrospective data from Jan 1, 2003, to Dec 31, 2019, from patients with MCT8 deficiency followed up in 47 hospitals in 22 countries globally. The key inclusion criterion was genetically confirmed MCT8 deficiency. There were no exclusion criteria. Our primary objective was to analyse the overall survival of patients with MCT8 deficiency and document causes of death. We also compared survival between patients who did or did not attain full head control by age 1.5 years and between patients who were or were not underweight by age 1-3 years (defined as a bodyweight-for-age Z score

Genetic white matter disorders have heterogeneous etiologies and overlapping clinical presentations. We performed a study of the diagnostic efficacy of genome sequencing in 41 unsolved cases with prior exome sequencing, resolving an additional 14 from an historical cohort (n = 191). Reanalysis in the context of novel disease‐associated genes and improved variant curation and annotation resolved 64% of cases. The remaining diagnoses were directly attributable to genome sequencing, including cases with small and large copy number variants (CNVs) and variants in deep intronic and technically difficult regions. Genome sequencing, in combination with other methodologies, achieved a diagnostic yield of 85% in this retrospective cohort.

Objectives: Metachromatic leukodystrophy (MLD) is a fatal lysosomal storage disease characterized by progressive demyelination within the central and peripheral nervous system. Rapid diagnosis is crucial in view of evolving therapeutic options. Strabismus has anecdotally been described as a feature in children with MLD. Our first aim was to examine the prevalence of strabismus as an early or even presenting sign of MLD in two nationwide cohorts. Second, we aimed to investigate the temporal relation between the onset of strabismus and gross motor deterioration, other early onset eye movement disorders and brain white matter abnormalities. Methods: Clinical records of 204 MLD patients at the University Children's Hospital Tubingen and Amsterdam University Medical Center were reviewed on the presence of strabismus and other eye movement disorders. Gross motor deterioration and white matter abnormalities on brain MRI were evaluated by using the Gross Motor Function Classification in MLD and MLD LOES score, respectively. Results: We identified strabismus as an early sign in MLD patients with the late-infantile form, with a prevalence of 27% (N = 17). The onset of strabismus preceded gross motor symptoms and brain white matter abnormalities in 71% and 46% respectively of the cases. Important characteristics were an acute-onset paralytic esotropia, partly accompanied by other eye movement abnormalities, and gadolinium enhancement of the cranial nerves. Conclusions: Acute-onset paralytic strabismus in toddlers should be considered a potential early sign of late-infantile MLD and might result from early cranial nerve involvement. Brain MRI with gadolinium contrast may facilitate early diagnosis.

Nucleotide metabolism is a complex pathway regulating crucial cellular processes such as nucleic acid synthesis, DNA repair and proliferation. This study shows that impairment of the biosynthesis of one of the building blocks of DNA, dTTP, causes a severe, early-onset neurodegenerative disease. Here, we describe two unrelated children with bi-allelic variants in DTYMK, encoding dTMPK, which catalyzes the penultimate step in dTTP biosynthesis. The affected children show severe microcephaly and growth retardation with minimal neurodevelopment. Brain imaging revealed severe cerebral atrophy and disappearance of the basal ganglia. In cells of affected individuals, dTMPK enzyme activity was minimal, along with impaired DNA replication. In addition, we generated dtymk mutant zebrafish that replicate this phenotype of microcephaly, neuronal cell death and early lethality. An increase of ribonucleotide incorporation in the genome as well as impaired responses to DNA damage were observed in dtymk mutant zebrafish, providing novel pathophysiological insights. It is highly remarkable that this deficiency is viable as an essential component for DNA cannot be generated, since the metabolic pathway for dTTP synthesis is completely blocked. In summary, by combining genetic and biochemical approaches in multiple models we identified loss-of-function of DTYMK as the cause of a severe postnatal neurodegenerative disease and highlight the essential nature of dTTP synthesis in the maintenance of genome stability and neuronal survival.

Objective: Vanishing white matter (VWM) is a genetic brain white matter disorder caused by mutations in eIF2B. eIF2B is central in the integrated stress response (ISR), during which its activity is inhibited by various cellular stresses. VWM is a chronic progressive disease with episodes of rapid neurological deterioration provoked by stresses. VWM patients and VWM mouse models show ISR deregulation in brain, correlating with chronic disease development. ISR inhibition ameliorates the chronic disease in VWM mice. The subacute deteriorations have not been modeled yet. We hypothesized that ISR activation could worsen disease progression in mice and model the episodic neurological deterioration. Method: We chose to activate the ISR by subjecting wild-type (wt) and VWM mice to an isocaloric low protein diet. This model would allow us to investigate the contribution of ISR activation in subacute decline in VWM. Results: We found that the low protein diet did not significantly affect amino acid levels nor ISR levels in wt and VWM mouse brain. Our study serendipitously led to the discovery of increased levels of glycine, asparagine and Fgf21 mRNA in VWM mouse brain irrespective of the dietary protein content. Strikingly, the ISR was not activated by the low protein diet in the liver of VWM in contrast to wt mice, due to a modest ISR deregulation in this organ. Discussion: A model for subacute neurological deterioration in VWM was not established. Possibly, ISR deregulation in VWM results in reduced ISR responsiveness.

Item does not contain fulltext NOTCH1 belongs to the NOTCH family of proteins that regulate cell fate and inflammatory responses. Somatic and germline NOTCH1 variants have been implicated in cancer, Adams-Oliver syndrome, and cardiovascular defects. We describe 7 unrelated patients grouped by the presence of leukoencephalopathy with calcifications and heterozygous de novo gain-of-function variants in NOTCH1. Immunologic profiling showed upregulated CSF IP-10, a cytokine secreted downstream of NOTCH1 signaling. Autopsy revealed extensive leukoencephalopathy and microangiopathy with vascular calcifications. This evidence implicates that heterozygous gain-of-function variants in NOTCH1 lead to a chronic central nervous system (CNS) inflammatory response resulting in a calcifying microangiopathy with leukoencephalopathy. ANN NEUROL 2022;92:895-901.

Phosphatidylinositol 4-kinase IIIα (PI4KIIIα/PI4KA/OMIM:600286) is a lipid kinase generating phosphatidylinositol 4-phosphate (PI4P), a membrane phospholipid with critical roles in the physiology of multiple cell types. PI4KIIIα’s role in PI4P generation requires its assembly into a heterotetrameric complex with EFR3, TTC7 and FAM126. Sequence alterations in two of these molecular partners, TTC7 (encoded by TTC7A or TCC7B) and FAM126, have been associated with a heterogeneous group of either neurological (FAM126A) or intestinal and immunological (TTC7A) conditions. Here we show that biallelic PI4KA sequence alterations in humans are associated with neurological disease, in particular hypomyelinating leukodystrophy. In addition, affected individuals may present with inflammatory bowel disease, multiple intestinal atresia and combined immunodeficiency. Our cellular, biochemical and structural modelling studies indicate that PI4KA-associated phenotypical outcomes probably stem from impairment of PI4KIIIα-TTC7-FAM126's organ-specific functions, due to defective catalytic activity or altered intra-complex functional interactions. Together, these data define PI4KA gene alteration as a cause of a variable phenotypical spectrum and provide fundamental new insight into the combinatorial biology of the PI4KIIIα-FAM126-TTC7-EFR3 molecular complex., Salter et al. show that biallelic variants in PI4KA—which encodes the enzymatic core of the PI4KIIIα-TTC7-FAM126 complex—cause a clinically diverse disorder comprising neurological, intestinal and immunological abnormalities.

Purpose: Recent reports of individuals with cytoplasmic transfer RNA (tRNA) synthetase-related disorders have identified cases with phenotypic variability from the index presentations. We sought to assess phenotypic variability in individuals with AARS1-related disease. Methods: A cross-sectional survey was performed on individuals with biallelic variants in AARS1. Clinical data, neuroimaging, and genetic testing results were reviewed. Alanyl tRNA synthetase (AlaRS) activity was measured in available fibroblasts. Results: We identified 11 affected individuals. Two phenotypic presentations emerged, one with early infantile–onset disease resembling the index cases of AARS1-related epileptic encephalopathy with deficient myelination (n = 7). The second (n = 4) was a later-onset disorder, where disease onset occurred after the first year of life and was characterized on neuroimaging by a progressive posterior predominant leukoencephalopathy evolving to include the frontal white matter. AlaRS activity was significantly reduced in five affected individuals with both early infantile–onset and late-onset phenotypes. Conclusion: We suggest that variants in AARS1 result in a broader clinical spectrum than previously appreciated. The predominant form results in early infantile–onset disease with epileptic encephalopathy and deficient myelination. However, a subgroup of affected individuals manifests with late-onset disease and similarly rapid progressive clinical decline. Longitudinal imaging and clinical follow-up will be valuable in understanding factors affecting disease progression and outcome.

Aim: To evaluate quantitative electroencephalogram (EEG) measures as predictors of long-term neurodevelopmental outcome in infants with a postconceptional age below 46 weeks, including typically developing infants born at term, infants with heterogeneous underlying pathologies, and infants born preterm. Method: A comprehensive search was performed using PubMed, Embase, and Web of Science from study inception up to 8th January 2021. Studies that examined associations between neonatal quantitative EEG measures, based on conventional and amplitude-integrated EEG, and standardized neurodevelopmental outcomes at 2 years of age or older were reviewed. Significant associations between neonatal quantitative EEG and long-term outcome measures were grouped into one or more of the following categories: cognitive outcome; motor outcome; composite scores; and other standardized outcome assessments. Results: Twenty-four out of 1740 studies were included. Multiple studies showed that conventional EEG-based absolute power in the delta, theta, alpha, and beta frequency bands and conventional and amplitude-integrated EEG-related amplitudes were positively associated with favourable long-term outcome across several domains, including cognition and motor performance. Furthermore, a lower presence of discontinuous background pattern was also associated with favourable outcomes. However, interpretation of the results is limited by heterogeneity in study design and populations. Interpretation: Neonatal quantitative EEG measures may be used as prognostic biomarkers to identify those infants who will develop long-term difficulties and who might benefit from early interventions.