Genotype-phenotype correlation in vanishing white matter disease

In vivo base editing of a pathogenic Eif2b5 variant improves vanishing white matter phenotypes in mice

Vanishing white matter (VWM) is a fatal leukodystrophy caused by recessive mutations in subunits of the eukaryotic translation initiation factor 2B. Currently, there are no effective therapies for VWM. Here, we assessed the potential of adenine base editing to correct human pathogenic VWM variants in mouse models. Using adeno-associated viral vectors, we delivered intein-split adenine base editors into the cerebral ventricles of newborn VWM mice, resulting in 45.9% ± 5.9% correction of the Eif2b5R191H variant in the cortex. Treatment slightly increased mature astrocyte populations and partially recovered the integrated stress response (ISR) in female VWM animals. This led to notable improvements in bodyweight and grip strength in females; however, locomotor disabilities were not rescued. Further molecular analyses suggest that more precise editing (i.e., lower rates of bystander editing) as well as more efficient delivery of the base editors to deep brain regions and oligodendrocytes would have been required for a broader phenotypic rescue. Our study emphasizes the potential, but also identifies limitations, of current in vivo base-editing approaches for the treatment of VWM or other leukodystrophies.

Adult-onset leukodystrophy with vanishing white matter: a case series of 19 patients

BACKGROUND

Leukodystrophy with vanishing white matter (LVWM) is an autosomal recessive disease with typical pediatric-onset caused by mutations in one of the five EIF2B genes. Adult-onset (AO) cases are rare.

METHODS

In this observational study, we reviewed clinical and laboratory information of the patients with AO-LVWM assessed at two referral centers in Italy and Portugal from Jan-2007 to Dec-2019.

RESULTS

We identified 18 patients (13 females) with AO-LVWM caused by EIF2B5 or EIF2B3 mutations. Age of neurological onset ranged from 16 to 60 years, with follow-ups occurring from 2 to 37 years. Crucial symptoms were cognitive and motor decline. In three patients, stroke-like events were the first manifestation; in another, bladder dysfunction remained the main complaint across decades. Brain MRI showed white matter (WM) rarefaction in all cases, except two. Diffusion-weighted imaging documented focal hyperintensity in the acute stage of stroke-like events. 1H-spectroscopy primarily showed N-acetyl-aspartate reduction; 18fluorodeoxyglucose-PET revealed predominant frontoparietal hypometabolism; evoked potential studies demonstrated normal-to-reduced amplitudes; neuro-ophthalmological assessment showed neuroretinal thinning, and b-wave reduction on full-field electroretinogram. Interestingly, we found an additional patient with LVWM-compatible phenotype and monoallelic variants in two distinct eIF2B genes, EIF2B1 and EIF2B2.

CONCLUSIONS

AO-LVWM presents varying clinical manifestations at onset, including stroke-like events. WM rarefaction is the most consistent diagnostic clue even in the latest onset cases. Spectroscopy and electrophysiological features are compatible with axon, rather than myelin, damage. Cerebral glucose metabolic abnormalities and retinal alterations can be present. LVWM might also be caused by a digenic inheritance affecting the eIF2B complex.

Clinical, genetic, and molecular characteristics in a central-southern Chinese cohort of genetic leukodystrophies

OBJECTIVE

Leukodystrophies are a diverse group of rare inherited disorders that affect the white matter of the central nervous system with a wide phenotypic spectrum. We aimed to characterize the clinical and genetic features of leukodystrophies in a central-southern Chinese cohort.

METHODS

A cohort of 16 Chinese probands with leukodystrophy was recruited and performed genetic analysis by targeted panels or whole-exome sequencing. Further functional analysis of identified mutations in the colony stimulating factor 1 receptor (CSF1R) gene was explored.

RESULTS

A total of eight pathogenic variants (3 novel, 5 documented) were identified in genes including AARS2, ABCD1, CSF1R, and GALC. Common symptoms of leukodystrophy such as cognitive decline, behavioral symptoms, bradykinesia, and spasticity were observed in mutation carriers as well as other rare features (e.g., seizure, dysarthric, and vision impairment). Overexpressing CSF1R mutants p.M875I and p.F971Sfs*7 in vitro showed pronounced cleavage CSF1R and suppressed protein expression, respectively, and reduced transcripts of both mutants were observed. CSF1 treatment revealed deficient and suppressed CSF1R phospho-activation with the mutants. In contrast to the plasma membrane and endoplasmic reticulum (ER) localized wild-type CSF1R, M875I mutant showed much less membrane association and greater detainment in the ER, whereas F971Sfs*7 mutation led to aberrant non-ER localization. Both mutations caused suppressed cell viability, which was partially resulted from deficient/suppressed CSF1R-ERK signaling.

INTERPRETATION

In summary, our findings expand the mutation spectrum of these genes in leukodystrophies. Supported by in vitro validation of the pathogenicity of heterozygous CSF1R mutations, our data also provide insights into the pathogenic mechanisms of CSF1R-related leukodystrophy.

Core protocol development for phase 2/3 clinical trials in the leukodystrophy vanishing white matter: a consensus statement by the VWM consortium and patient advocates

BACKGROUND

The leukodystrophy "Vanishing White Matter" (VWM) is an orphan disease with neurological decline and high mortality. Currently, VWM has no approved treatments, but advances in understanding pathophysiology have led to identification of promising therapies. Several investigational medicinal products are either in or about to enter clinical trial phase. Clinical trials in VWM pose serious challenges, as VWM has an episodic disease course; disease phenotype is highly heterogeneous and predictable only for early onset; and study power is limited by the small patient numbers. To address these challenges and accelerate therapy delivery, the VWM Consortium, a group of academic clinicians with expertise in VWM, decided to develop a core protocol to function as a template for trials, to improve trial design and facilitate sharing of control data, while permitting flexibility regarding other trial details. Overall aims of the core protocol are to collect safety, tolerability, and efficacy data for treatment assessment and marketing authorization.

METHODS

To develop the core protocol, the VWM Consortium designated a committee, including clinician members of the VWM Consortium, family and patient group advocates, and experts in statistics, clinical trial design and alliancing with industries. We drafted three age-specific protocols, to stratify into more homogeneous patient groups, of ages ≥ 18 years, ≥ 6 to < 18 years and < 6 years. We chose double-blind, randomized, placebo-controlled design for patients aged ≥ 6 years; and open-label non-randomized natural-history-controlled design for patients < 6 years. The protocol describes study populations, age-specific endpoints, inclusion and exclusion criteria, study schedules, sample size determinations, and statistical considerations.

DISCUSSION

The core protocol provides a shared uniformity across trials, enables a pool of shared controls, and reduces the total number of patients necessary per trial, limiting the number of patients on placebo. All VWM clinical trials are suggested to adhere to the core protocol. Other trial components such as choice of primary outcome, pharmacokinetics, pharmacodynamics, and biomarkers are flexible and unconstrained by the core protocol. Each sponsor is responsible for their trial execution, while the control data are handled by a shared research organization. This core protocol benefits the efficiency of parallel and consecutive trials in VWM, and we hope accelerates time to availability of treatments for VWM.

TRIAL REGISTRATION

NA. From a scientific and ethical perspective, it is strongly recommended that all interventional trials using this core protocol are registered in a clinical trial register.

EIF2B2 gene mutation causing early onset vanishing white matter disease: a case report

Background

Leukoencephalopathy with vanishing white matter (VWM) is an autosomal recessive neurological disease. The physiopathology of disease is still little understood, but it seems to involve impairment in maturation of astrocytes; as a consequence white matter is more prone to cellular stress. Disease is caused by mutations in five genes encoding subunits of the translation initiation factor eIF2B. We know five different types of VWM syndrome classified based different ages of onset (prenatal, infantile, childhood, juvenile and adult onset).

Case presentation

We report the case of a 4-month-old boy with early seizure onset, recurrent hypoglycemia and post mortem diagnosis of vanishing white matter disease (VMD). At the admission he presented suspected critical episodes, resolved after intravenous administration of benzodiazepines. The brain MRI showed total absence of myelination that suggested hypomyelination leukoencephalopathy. The whole exome sequencing (WES) revealed a variant of EIF2B2 gene (p. Val308Met) present in homozygosity. In this case report we also describe the clinical evolution of seizures, in fact the epileptic seizures had a polymorphic aspect, from several complex partial seizures secondarily generalized to status epilepticus.

Conclusion

Infantile and early childhood onset forms are associated with chronic progressive neurological signs, with episodes of rapid neurological worsening, and poor prognosis, with death in few months or years. Clinical presentation of epilepsy is poorly documented and do not include detailed information about the type, time of onset and severity of seizures. No therapeutic strategies for VWM disease have been reported.

Therapy Trial Design in Vanishing White Matter: An Expert Consortium Opinion

Vanishing white matter (VWM) is a leukodystrophy caused by recessive variants in the genes EIF2B1-EIF2B5. It is characterized by chronic neurologic deterioration with superimposed stress-provoked episodes of rapid decline. Disease onset spans from the antenatal period through senescence. Age at onset predicts disease evolution for patients with early onset, whereas disease evolution is unpredictable for later onset; patients with infantile and early childhood onset consistently have severe disease with rapid neurologic decline and often early death, whereas patients with later onset have highly variable disease. VWM is rare, but likely underdiagnosed, particularly in adults. Apart from measures to prevent stressors that could provoke acute deteriorations, only symptomatic care is currently offered. With increased insight into VWM disease mechanisms, opportunities for treatment have emerged. EIF2B1-EIF2B5 encode the 5-subunit eukaryotic initiation factor 2B complex, which is essential for translation of mRNAs into proteins and is a principal regulator of the integrated stress response (ISR). ISR deregulation is central to VWM pathology. Targeting components of the ISR has proven beneficial in mutant VWM mouse models, and several drugs are now in clinical development. However, clinical trials in VWM pose considerable challenges: low numbers of known patients with VWM, unpredictable disease course for patients with onset after early childhood, absence of intermediate biomarkers, and novel first-in-human molecular targets. Given these challenges and considering the critical need to offer therapies, we have formulated recommendations for enhanced diagnosis, drug trial setup, and patient selection, based on our expert evaluation of molecular, laboratory, and clinical data.

An eleven-year history of Vanishing White Matter Disease in an adult patient with no cognitive decline and EIF2B5 mutations. A case report

Vanishing White Matter Disease (VWMD) is a rare autosomal recessive leukoencephalopathy . The classical presentation is characterized by a severe cerebellar ataxia, spasticity, neurological deterioration with a chronic progressive course and episodes of acute neurological deterioration after stress conditions.We report a 52-year-old man with VWMD and atypical features who manifested two major events of transient aphasia eleven years apart with complete recovery in 48 hours. No cognitive decline was present. Brain MRI revealed typical aspects of VWMD including diffuse leukoencephalopathy with relative sparing of U-fibers. We identified the presence of c.592G>A (p.Glu198Lys) and c.1360 C>T (p.Pro454Ser) mutations in EIF2B5.

Correlation Between Genotype and Age of Onset in Leukoencephalopathy With Vanishing White Matter

Purpose: Leukoencephalopathy with vanishing white matter (VWM) is an autosomal recessive leukoencephalopathy caused by mutations in any of the five genes encoding the subunits of eukaryotic translation initiation factor 2B (eIF2B). The severity of the disease varies considerably, and its genotypic-phenotypic correlation is still unclear. Age of onset is the only independent clinical predictor for VWM severity. In this study, the correlation between genotype and age at onset of patients was investigated.

Methods: Data were collected from patients with VWM in the available literature reports and from those diagnosed in Peking University First Hospital. The age of onset was divided into early-onset (≤4 years) and late-onset type (>4 years) for the analysis of the correlation between genotype and age of onset in patients with VWM.

Results: A total of 341 patients were included, 281 were reported in 87 available articles and 60 were diagnosed in our center. A total of 180 different mutations were found, among which 86.1% were missense. The gene (EIF2B1-5) in which the mutation located, and the number of null alleles were not associated with age of onset in these patients. Certain mutations such as eIF2Bε[Arg195His] and eIF2Bε[Arg269Gln] that were predicted to have a serious influence on eIF2B structure were related to earlier age of onset. EIF2Bγ[Ala87Val] which was predicted to have a minimal influence on eIF2B structure, was related to later age of onset. Whereas eIF2Bβ[Glu213Gly], eIF2Bβ[Gly200Val] and eIF2Bε[Thr91Ala], also predicted having a small effect on the structure of eIF2B, did not show correlation with the age of onset. The onset age of patients with one or biallelic missense mutations located in the catalytic domain or other homologous domains in catalytic subunits (eIF2Bγ, ε) was earlier than that of patients with biallelic mutations located in the NT domain.

Conclusion: The onset age of patients with different genotypes varied greatly. The degree of influence in protein structure of some missense mutations was correlated with phenotypic severity, but the results were not completely consistent. The combined effect of biallelic mutations, the role of regulatory genes, environmental stress and other potential factors on phenotypes need to be further explored.

Comparative Proteome Research in a Zebrafish Model for Vanishing White Matter Disease

Vanishing white matter (VWM) disease is a genetic leukodystrophy leading to severe neurological disease and early death. VWM is caused by bi-allelic mutations in any of the five genes encoding the subunits of the eukaryotic translation factor 2B (EIF2B). Previous studies have attempted to investigate the molecular mechanism of VWN by constructing models for each subunit of EIF2B that causes VWM disease. The underlying molecular mechanisms of the way in which mutations in EIF2B3 result in VWM are largely unknown. Based on our recent results, we generated an eif2b3 knockout (eif2b3^-/-) zebrafish model and performed quantitative proteomic analysis between the wild-type (WT) and eif2b3^-/- zebrafish, and identified 25 differentially expressed proteins. Four proteins were significantly upregulated, and 21 proteins were significantly downregulated in eif2b3^-/- zebrafish compared to WT. Lon protease and the neutral amino acid transporter SLC1A4 were significantly increased in eif2b3^-/- zebrafish, and crystallin proteins were significantly decreased. The differential expression of proteins was confirmed by the evaluation of mRNA levels in eif2b3^-/- zebrafish, using whole-mount in situ hybridization analysis. This study identified proteins which candidates as key regulators of the progression of VWN disease, using quantitative proteomic analysis in the first EIF2B3 animal model of VWN disease.

Vanishing white matter: Eukaryotic initiation factor 2B model and the impact of missense mutations

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 disease expression of truncated EIF2B5 activates induced stress response

Vanishing white matter disease (VWM) is a severe leukodystrophy of the central nervous system caused by mutations in subunits of the eukaryotic initiation factor 2B complex (eIF2B). Current models only partially recapitulate key disease features, and pathophysiology is poorly understood. Through development and validation of zebrafish (Danio rerio) models of VWM, we demonstrate that zebrafish eif2b mutants phenocopy VWM, including impaired somatic growth, early lethality, effects on myelination, loss of oligodendrocyte precursor cells, increased apoptosis in the CNS, and impaired motor swimming behavior. Expression of human EIF2B2 in the zebrafish eif2b2 mutant rescues lethality and CNS apoptosis, demonstrating conservation of function between zebrafish and human. In the mutants, intron 12 retention leads to expression of a truncated eif2b5 transcript. Expression of the truncated eif2b5 in wild-type larva impairs motor behavior and activates the ISR, suggesting that a feed-forward mechanism in VWM is a significant component of disease pathophysiology.

CT and MRI findings in infantile vanishing white matter

Infantile vanishing white matter disease is an uncommon cause of developmental delay and seizures in children. Presented here is a case of vanishing white matter disease diagnosed at 6 months of age. Imaging findings demonstrated widespread white matter abnormalities throughout the supratentorial and infratentorial brain. The diagnosis of infantile vanishing white matter disease was confirmed via molecular analysis which revealed a rare mutation in the gene responsible for this disorder.

Foetal onset of EIF2B related disorder in two siblings: cerebellar hypoplasia with absent Bergmann glia and severe hypomyelination

Bi-allelic pathogenic variants in genes of the EIF2B family are responsible for Childhood Ataxia with Central nervous system Hypomyelination/Vanishing White Matter disease, a progressive neurodegenerative disorder of the central white matter. Only seven molecularly proven cases with antenatal onset have been reported so far. We report for the first time the neuropathological findings obtained from two foetuses harbouring deleterious variants in the EIF2B5 gene who presented in utero growth retardation and microcephaly with simplified gyral pattern that led to a medical termination of the pregnancy at 27 and 32 weeks of gestation. Neuropathological examination confirmed microcephaly with delayed gyration, periventricular pseudo-cysts and severe cerebellar hypoplasia. Histologically, the cerebellar cortex was immature, the dentate nuclei were fragmented and myelin stains revealed almost no myelination of the infratentorial structures. Bergmann glia was virtually absent associated to a drastic decreased number of mature astrocytes in the cerebellar white matter, multiple nestin-positive immature astrocytes as well as increased numbers of PDGRFα-positive oligodendrocyte precursors. Whole exome sequencing performed in the two foetuses and their parents allowed the identification of two EIF2B5 compound heterozygous variants in the two foetuses: c.468C > G p.Ile156Met and c.1165G > A p.Val389Met, the parents being heterozygous carriers. These variants are absent in the genome Aggregation Database (gnomAD r2.0.2). Contrary to the variant Ile156Met already described in a patient with CACH syndrome, the variant p.Val389Met is novel and predicted to be deleterious using several softwares. Neuropathological findings further expand the phenotypic spectrum of the disease that very likely occurs during early gestation and may manifest from the second half of pregnancy by a severe impairment of cerebral and cerebellar development.

Stem cell derived oligodendrocytes to study myelin diseases

Oligodendroglial pathology is central to de- and dysmyelinating, but also contributes to neurodegenerative and psychiatric diseases as well as brain injury. The understanding of oligodendroglial biology in health and disease has been significantly increased during recent years by experimental in vitro and in vivo preclinical studies as well as histological analyses of human tissue samples. However, for many of these diseases the underlying pathology is still not fully understood and treatment options are frequently lacking. This is at least partly caused by the limited access to human oligodendrocytes from patients to perform functional studies and drug screens. The induced pluripotent stem cell technology (iPSC) represents a possibility to circumvent this obstacle and paves new ways to study human disease and to develop new treatment options for so far incurable central nervous system (CNS) diseases. In this review, we summarize the differences between human and rodent oligodendrocytes, provide an overview of the different techniques to generate oligodendrocytes from human progenitor or stem cells and describe the results from studies using iPSC derived oligodendroglial lineage cells. Furthermore, we discuss future perspectives and challenges of the iPSC technology with respect to disease modeling, drug screen, and cell transplantation approaches.

Adult-onset vanishing white matter disease with the EIF2B2 gene mutation presenting as menometrorrhagia

Background

Vanishing white matter disease (VWMD) is one of the most prevalent inherited leukoencephalopathies, which generally presents in childhood as a progressive disorder while less beginning in adulthood. The present report describes the clinical, neuroimaging, and genetic findings of a female patient with adult-onset VWMD. In addition, to provide a clearer delineation of the clinical and genetic characteristics of female adult-onset VWMD patients, 32 genetically confirmed female adult-onset EIF2B-mutated cases are summarized.

Case presentation

The patient described here suffered from long-term menometrorrhagia prior to manifesting progressive neurological impairments that included tremors, bilateral pyramidal tract injury, cerebellar ataxia, and dementia. To the best of our knowledge, this is the first female patient with adult-onset VWMD suffering from long-term menometrorrhagia attributed to the c.254 T > A and c.496A > G mutations in the EIF2B2 gene; the c.496A > G mutation has not been reported in previous studies. The patient also exhibited metabolic dysfunction. The present findings widen the spectrum of phenotypic heterogeneity observed in VWMD patients.

Conclusions

The present report summarizes 33 female patients with adult-onset VWMD to provide an overview of the clinical and genetic characteristics of this disorder and ovarioleukodystrophy. The mean age of clinical onset in female patients with adult-onset VWMD was 36.8 years and the neurological symptoms primarily included motor and cognitive dysfunction such as paraparesis, cerebellar ataxia, and executive deficits. In addition, ovarian failure occurred in all of these female patients and usually preceded the neurological symptoms. Furthermore, several patients also suffered from metabolic dysfunction. All 33 patients had mutations on EIF2B1–5, and of these, the c.338 G > A mutation in the EIF2B5 gene (p.Arg113His) was the most common. These findings suggest that clinicians should be aware of adult-onset forms of VWMD as well as its typical magnetic resonance imaging (MRI) and clinical characteristics although this pathology is usually recognized as a pediatric disorder. No curative treatment is presently available, and thus early recognition is important to prevent triggering events and to allow for genetic counseling.

Electronic supplementary material

The online version of this article (10.1186/s12883-019-1429-9) contains supplementary material, which is available to authorized users.

Missing in Action: Dysfunctional RNA Metabolism in Oligodendroglial Cells as a Contributor to Neurodegenerative Diseases?

The formation of myelin around axons by oligodendrocytes (OL) poses an enormous synthetic and energy challenge for the glial cell. Local translation of transcripts, including the mRNA for the essential myelin protein Myelin Basic Protein (MBP) at the site of myelin deposition has been recognised as an efficient mechanism to assure proper myelin sheath assembly. Oligodendroglial precursor cells (OPCs) form synapses with neurons and may localise many additional mRNAs in a similar fashion to synapses between neurons. In some diseases in which demyelination occurs, an abundance of OPCs is present but there is a failure to efficiently remyelinate and to synthesise MBP. This compromises axonal survival and function. OPCs are especially sensitive to cellular stress as occurring in neurodegenerative diseases, which can impinge on their ability to translate mRNAs into protein. Stress causes the build up of cytoplasmic stress granules (SG) in which many RNAs are sequestered and translationally stalled until the stress ceases. Chronic stress in particular could convert this initially protective reaction of the cell into damage, as persistence of SG may lead to pathological aggregate formation or long-term translation block of SG-associated RNAs. The recent recognition that many neurodegenerative diseases often exhibit an early white matter pathology with a proliferation of surviving OPCs, renders a study of the stress-associated processes in oligodendrocytes and OPCs especially relevant. Here, we discuss a potential dysfunction of RNA regulation in myelin diseases such as Multiple Sclerosis (MS) and Vanishing white matter disease (VWM) and potential contributions of OL dysfunction to neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD) and Fragile X syndrome (FXS).

Vanishing white matter: a leukodystrophy due to astrocytic dysfunction

VWM is one of the most prevalent leukodystrophies with unique clinical, pathological and molecular features. It mostly affects children, but may develop at all ages, from birth to senescence. It is dominated by cerebellar ataxia and susceptible to stresses that act as factors provoking disease onset or episodes of rapid neurological deterioration possibly leading to death. VWM is caused by mutations in any of the genes encoding the five subunits of the eukaryotic translation initiation factor 2B (eIF2B). Although eIF2B is ubiquitously expressed, VWM primarily manifests as a leukodystrophy with increasing white matter rarefaction and cystic degeneration, meager astrogliosis with no glial scarring and dysmorphic immature astrocytes and increased numbers of oligodendrocyte progenitor cells that are restrained from maturing into myelin-forming cells. Recent findings point to a central role for astrocytes in driving the brain pathology, with secondary effects on both oligodendroglia and axons. In this, VWM belongs to the growing group of astrocytopathies, in which loss of essential astrocytic functions and gain of detrimental functions drive degeneration of the white matter. Additional disease mechanisms include activation of the unfolded protein response with constitutive predisposition to cellular stress, failure of astrocyte-microglia crosstalk and possibly secondary effects on the oxidative phosphorylation. VWM involves a translation initiation factor. The group of leukodystrophies due to defects in mRNA translation is also growing, suggesting that this may be a common disease mechanism. The combination of all these features makes VWM an intriguing natural model to understand the biology and pathology of the white matter.

Natural History of Vanishing White Matter

OBJECTIVE

To comprehensively describe the natural history of vanishing white matter (VWM), aiming at improving counseling of patients/families and providing natural history data for future therapeutic trials.

METHODS

We performed a longitudinal multicenter study among 296 genetically confirmed VWM patients. Clinical information was obtained via disease-specific clinical questionnaire, Health Utilities Index and Guy's Neurological Disability Scale assessments, and chart review.

RESULTS

First disease signs occurred at a median age of 3 years (mode = 2 years, range = before birth to 54 years); 60% of patients were symptomatic before the age of 4 years. The nature of the first signs varied for different ages of onset. Overall, motor problems were the most common presenting sign, especially in children. Adolescent and adult onset patients were more likely to exhibit cognitive problems early after disease onset. One hundred two patients were deceased. Multivariate Cox regression analysis revealed a positive relation between age at onset and both preservation of ambulation and survival. Absence of stress-provoked episodes and absence of seizures predicted more favorable outcome. In patients with onset before 4 years, earlier onset was associated with more severe disability and higher mortality. For onset from 4 years on, disease course was generally milder, with a wide variation in severity. There were no significant differences for sex or for the 5 eIF2B gene groups. The results confirm the presence of a genotype-phenotype correlation.

INTERPRETATION

The VWM disease spectrum consists of a continuum with extremely wide variability. Age at onset is a strong predictor for disease course. Ann Neurol 2018;84:274-288.

New Insights in Vanishing White Matter Disease: Isolated Bilateral Optic Neuropathy in Adult Onset Disease

BACKGROUND

Vanishing white matter disease (VWMD) is a rare disease affecting cerebral white matter. The adult form is even rarer and manifests with motor symptoms, behavioral problems, and dementia. There is no treatment and progression is inevitable. We describe a case with atypical manifestations and an unusual course.

METHODS

Description of a 42-year-old man with VWMD complaining of progressive visual loss in the right eye.

RESULTS

The patient's visual acuity was 20/60, right eye, and 20/25, left eye, with pale optic nerves bilaterally. MRI showed atrophy of the corpus callosum, diffuse rarefaction of cerebral white matter including the anterior and posterior visual pathways.

CONCLUSION

Our patient had no further symptoms besides loss of visual acuity, which is rare in patients with VWMD of the same age and genetic mutation.

Leukodystrophies: a proposed classification system based on pathological changes and pathogenetic mechanisms

Leukodystrophies are genetically determined disorders characterized by the selective involvement of the central nervous system white matter. Onset may be at any age, from prenatal life to senescence. Many leukodystrophies are degenerative in nature, but some only impair white matter function. The clinical course is mostly progressive, but may also be static or even improving with time. Progressive leukodystrophies are often fatal, and no curative treatment is known. The last decade has witnessed a tremendous increase in the number of defined leukodystrophies also owing to a diagnostic approach combining magnetic resonance imaging pattern recognition and next generation sequencing. Knowledge on white matter physiology and pathology has also dramatically built up. This led to the recognition that only few leukodystrophies are due to mutations in myelin- or oligodendrocyte-specific genes, and many are rather caused by defects in other white matter structural components, including astrocytes, microglia, axons and blood vessels. We here propose a novel classification of leukodystrophies that takes into account the primary involvement of any white matter component. Categories in this classification are the myelin disorders due to a primary defect in oligodendrocytes or myelin (hypomyelinating and demyelinating leukodystrophies, leukodystrophies with myelin vacuolization); astrocytopathies; leuko-axonopathies; microgliopathies; and leuko-vasculopathies. Following this classification, we illustrate the neuropathology and disease mechanisms of some leukodystrophies taken as example for each category. Some leukodystrophies fall into more than one category. Given the complex molecular and cellular interplay underlying white matter pathology, recognition of the cellular pathology behind a disease becomes crucial in addressing possible treatment strategies.

eIF2B-related multisystem disorder in two sisters with atypical presentations

BACKGROUND

Vanishing white matter disease (VWM) is a chronic progressive leukoencephalopathy that is characterized by cerebellar ataxia and spasticity, together with cystic degeneration of the cerebral white matter as evidenced by brain magnetic resonance imaging (MRI). Here, we report two sisters with EIF2B2 variants, who presented with delayed development and failure to thrive before 1 year of age, developed cataracts, and showed diffuse leukoencephalopathy.

CASE PRESENTATION

The index case had a history of hepatomegaly and intermittent vomiting after upper respiratory infection at 11 months of age. Her older brothers had died at an early age, one with similar symptoms and the other because of septic shock. Her older sister had similar presenting symptoms; she later suffered from both cataracts and primary amenorrhea, but showed neurological improvement. Her follow-up MRIs (at 21 years of age) revealed progressive diffuse brain atrophy with leukoencephalopathy, without cystic rarefaction. Whole-exome sequencing of the index case revealed the presence of the compound heterozygous variants, Val85Glu and Met226Lys in EIF2B2. The affected sister had the same compound heterozygous variants, and their unaffected parents were heterozygous carriers of each variant.

CONCLUSIONS

This study expanded the clinical and genetic spectrum of VWM with EIF2B2 variants. It would be better to consider VWM as an eIF2B-related multisystem disorder, not just as a neurological disorder, on the basis that this is a family of housekeeping genes that affect multiple organs.

Progressive leukoencephalopathy impairs neurobehavioral development in sialin-deficient mice

Slc17a5^-/- mice represent an animal model for the infantile form of sialic acid storage disease (SASD). We analyzed genetic and histological time-course expression of myelin and oligodendrocyte (OL) lineage markers in different parts of the CNS, and related this to postnatal neurobehavioral development in these mice. Sialin-deficient mice display a distinct spatiotemporal pattern of sialic acid storage, CNS hypomyelination and leukoencephalopathy. Whereas few genes are differentially expressed in the perinatal stage (p0), microarray analysis revealed increased differential gene expression in later postnatal stages (p10-p18). This included progressive upregulation of neuroinflammatory genes, as well as continuous down-regulation of genes that encode myelin constituents and typical OL lineage markers. Age-related histopathological analysis indicates that initial myelination occurs normally in hindbrain regions, but progression to more frontal areas is affected in Slc17a5^-/- mice. This course of progressive leukoencephalopathy and CNS hypomyelination delays neurobehavioral development in sialin-deficient mice. Slc17a5^-/- mice successfully achieve early neurobehavioral milestones, but exhibit progressive delay of later-stage sensory and motor milestones. The present findings may contribute to further understanding of the processes of CNS myelination as well as help to develop therapeutic strategies for SASD and other myelination disorders.

Case of Childhood Ataxia with Central Nervous System Hypomyelination with a Novel Mutation in EIF2B3 gene

A 4-year-old boy presented with loss of motor milestones following viral fever. On examination, the child had increased tone and exaggerated deep tendon reflexes. Magnetic resonance imaging of the brain showed white matter hyperintensities on T2-weighted images, which revealed partial inversion on fluid-attenuated inversion recovery images. Clinical exome sequencing revealed a novel homozygous mutation c.1270T>G: pCys424Gly in exon 11 of the EIF2B3 gene. This novel mutation is reported in this article along with a literature review.

Different Eukaryotic Initiation Factor 2Bε Mutations Lead to Various Degrees of Intolerance to the Stress of Endoplasmic Reticulum in Oligodendrocytes

Background:

Vanishing white matter disease (VWM), a human autosomal recessive inherited leukoencephalopathy, is due to mutations in eukaryotic initiation factor 2B (eIF2B). eIF2B is responsible for the initiation of protein synthesis by its guanine nucleotide exchange factor (GEF) activity. Mutations of eIF2B impair GEF activity at different degree. Previous studies implied improperly activated unfolded protein response (UPR) and endoplasmic reticulum stress (ERS) participated in the pathogenesis of VWM. Autophagy relieves endoplasmic reticulum load by eliminating the unfolded protein. It is still unknown the effects of genotypes on the pathogenesis. In this work, UPR and autophagy flux were analyzed with different mutational types.

Methods:

ERS tolerance, reflected by apoptosis and cell viability, was detected in human oligodendrocyte cell line transfected with the wild type, or different mutations of p. Arg113His, p. Arg269* or p. Ser610-Asp613del in eIF2Bε. A representative UPR-PERK component of activating transcription factor 4 (ATF4) was measured under the basal condition and ERS induction. Autophagy was analyzed the flux in the presence of lysosomal inhibitors.

Results:

The degree of ERS tolerance varied in different genotypes. The truncated or deletion mutant showed prominent apoptosis cell viability declination after ERS induction. The most seriously damaged GEF activity of p. Arg269* group underwent spontaneous apoptosis. The truncated or deletion mutant showed elevated ATF4 under basal as well as ERS condition. Decreased expression of LC3-I and LC3-II in the mutants reflected an impaired autophagy flux, which was more obvious in the truncated or deletion mutants after ERS induction.

Conclusions:

GEF activities in different genotypes could influence the cell ERS tolerance as well as compensatory pathways of UPR and autophagy. Oligodendrocytes with truncated or deletion mutants showed less tolerable to ERS.

Astrocytes are central in the pathomechanisms of vanishing white matter

Vanishing white matter (VWM) is a fatal leukodystrophy that is caused by mutations in genes encoding subunits of eukaryotic translation initiation factor 2B (eIF2B). Disease onset and severity are codetermined by genotype. White matter astrocytes and oligodendrocytes are almost exclusively affected; however, the mechanisms of VWM development remain unclear. Here, we used VWM mouse models, patients' tissue, and cell cultures to investigate whether astrocytes or oligodendrocytes are the primary affected cell type. We generated 2 mouse models with mutations (Eif2b5Arg191His/Arg191His and Eif2b4Arg484Trp/Arg484Trp) that cause severe VWM in humans and then crossed these strains to develop mice with various mutation combinations. Phenotypic severity was highly variable and dependent on genotype, reproducing the clinical spectrum of human VWM. In all mutant strains, impaired maturation of white matter astrocytes preceded onset and paralleled disease severity and progression. Bergmann glia and retinal Müller cells, nonforebrain astrocytes that have not been associated with VWM, were also affected, and involvement of these cells was confirmed in VWM patients. In coculture, VWM astrocytes secreted factors that inhibited oligodendrocyte maturation, whereas WT astrocytes allowed normal maturation of VWM oligodendrocytes. These studies demonstrate that astrocytes are central in VWM pathomechanisms and constitute potential therapeutic targets. Importantly, astrocytes should also be considered in the pathophysiology of other white matter disorders.

Fifteen novel EIF2B1-5 mutations identified in Chinese children with leukoencephalopathy with vanishing white matter and a long term follow-up

Leukoencephalopathy with vanishing white matter (VWM) is one of the most prevalent inherited childhood white matter disorders, which caused by mutations in each of the five subunits of eukaryotic translation initiation factor 2B (EIF2B1-5). In our study, 34 out of the 36 clinically diagnosed children (94%) were identified to have EIF2B1-5 mutations by sequencing. 15 novel mutations were identified. CNVs were not detected in patients with only one mutant allele and mutation-negative determined by gene sequencing. There is a significantly higher incidence of patients with EIF2B3 mutations compared with Caucasian patients (32% vs. 4%). c.1037T>C (p.Ile346Thr) in EIF2B3 was confirmed to be a founder mutation in Chinese, which probably one of the causes of the genotypic differences between ethnicities. Our average 4.4 years-follow-up on infantile, early childhood and juvenile VWM children suggested a rapid deterioration in motor function. Episodic aggravation was presented in 90% of infantile cases and 71.4% of childhood cases. 10 patients died during the follow-up. The Kaplan-Meier curve showed that the median survival time is 8.83 ± 1.51 years. This is the largest sample of children in a VWM follow-up study, which is helpful for a more depth understanding about the natural course.

Vanishing white matter disease in French-Canadian patients from Quebec

BACKGROUND

Vanishing white matter disease is an autosomal recessive leukodystrophy caused by mutations in any of the five genes encoding the subunits of the eukaryotic translation initiation factor 2B. Most of the reported patients are of North American and European ancestry.

OBJECTIVE

The objective of the study was to review the clinical, radiological, and molecular characteristics of vanishing white matter disease in a cohort of French-Canadian patients.

METHODS

Between 2004 and March 2012, five French-Canadian (non-Cree) patients from Quebec were clinically and genetically diagnosed with vanishing white matter disease within three Montreal Neurogenetics and Leukodystrophy clinics. Their clinical presentation and evolution, demographic characteristics, genetic mutations, and imaging were reviewed and compared with what is known in the literature.

RESULTS

Sequencing of the exons and intronic boundaries of the EIF2B1-5 genes revealed a rare 260C>T (A87V) missense mutation in EIF2B3 in two homozygous patients and one compound heterozygous patient. This mutation was previously reported in only one patient in the literature. The carrier frequency is unknown. Also, three of five Quebec patients had an extremely rare vanishing white matter disease presentation of migraines with transient neurological abnormalities.

CONCLUSION

The 260C>T (A87V) mutation in exon 3 of the EIF2B3 gene is likely a founder mutation for vanishing white matter disease in Quebec. Transient hemiparesthesia and hemiparesis episodes accompanied by headaches as presenting abnormalities of vanishing white matter disease are usually rare but seemed to be more frequent among the French-Canadian Quebec patients. They seemed to be preceded by periods of stress.

Vanishing white matter disease presenting as opsoclonus myoclonus syndrome in childhood--a case report and review of the literature

BACKGROUND

Vanishing white matter disease is caused by mutations of the eukaryotic translation initiation factor 2B (EIF2B) and is a prevalent cause of inherited childhood leukoencephalopathy. Infantile and early childhood onset forms are associated with chronic progressive neurological signs, with episodes of rapid, neurological, and poor prognosis, with death in few months or years. In contrast, onset in late childhood and adult onset is rare and is associated with long-term survival because of milder signs and slow progression.

PATIENT DESCRIPTION

We present a patient with a genetically proven vanishing white matter disease, typical brain MRI, presenting with opsoclonus myoclonus in early childhood and a delayed development of adult multifocal dystonia and schizoaffective disorder with continued survival. In addition we have also reviewed the relevant literature based on 42 previous articles summarizing clinical details of 318 individuals with vanishing white matter disease (single case reports to case series). In 283, genetic mutation of EIF2B was confirmed with the onset of vanishing white matter disease reported as antenatal (seven), infantile (eight), early childhood (107), between infantile and early childhood (20), late childhood (25), between early and late childhood (three), adult (68), and between late childhood and adult (21).

CONCLUSIONS

Various movement disorders have been described with vanishing white matter disease either at presentation (mimicking an opsoclonus myoclonus syndrome) or in adulthood (dystonia and myoclonus) with continuing survival. Relatively preserved cognition is a novel presentation and is reported in this article along with a comprehensive literature review.

Vanishing White Matter With Hepatomegaly and Hypertriglyceridemia Attacks

Vanishing white matter disease is one of the most prevalent leukodystrophies in childhood. It is caused by mutations in any of the genes encoding the 5 subunits of the eukaryotic translation initiation factor 2B (eIF2B), EIF2B1 through EIF2B5. Phenotypic variation is wide and it may affect people of all ages. Here we present a child with vanishing white matter who had hepatomegaly and hypertriglyceridemia attacks along with neurologic deterioration episodes. He was found heterozygous for the 2 mutations c.817 A>C, p.Lys273Gln and c.939_948del, p.Asp314ProfsX23 in the gene EIF2B2. Until today, this association was not defined in the literature.

A yeast purification system for human translation initiation factors eIF2 and eIF2Bε and their use in the diagnosis of CACH/VWM disease

Recessive inherited mutations in any of five subunits of the general protein synthesis factor eIF2B are responsible for a white mater neurodegenerative disease with a large clinical spectrum. The classical form is called Childhood Ataxia with CNS hypomyelination (CACH) or Vanishing White Matter Leukoencephalopathy (VWM). eIF2B-related disorders affect glial cells, despite the fact that eIF2B is a ubiquitous protein that functions as a guanine-nucleotide exchange factor (GEF) for its partner protein eIF2 in the translation initiation process in all eukaryotic cells. Decreased eIF2B activity measured by a GEF assay in patients' immortalised lymphocytic cells provides a biochemical diagnostic assay but is limited by the availability of eIF2 protein, which is classically purified from a mammalian cell source by column chromatography. Here we describe the generation of a recombinant expression system to produce purified human eIF2 from yeast cells. We demonstrate that human eIF2 can function in yeast cells in place of the equivalent yeast factor. We purify human eIF2 and the C-terminal domain of human eIF2Bε using affinity chromatography from engineered yeast cells and find that both function in a GEF assay: the first demonstration that this human eIF2Bε domain has GEF function. We show that CACH/VWM mutations within this domain reduce its activity. Finally we demonstrate that the recombinant eIF2 functions similarly to eIF2 purified from rat liver in GEF assays with CACH/VWM eIF2B-mutated patient derived lymphocytic cells.

Adult-onset vanishing white matter disease due to a novel EIF2B3 mutation

OBJECTIVE

To report a novel mutation in the gene EIF2B3 responsible for a late-onset form of vanishing white matter disease.

DESIGN

Case report.

SETTING

University teaching hospital.

PATIENT

A 29-year-old pregnant woman with a history of premature ovarian failure and hemiplegic migraines presented with a 10-week history of progressive confusion and headaches. Magnetic resonance imaging of the brain revealed a diffuse leukoencephalopathy.

RESULTS

Sequencing of the exons and intron boundaries of EIF2B3 uncovered 2 missense mutations: c.260C>T(p.Ala87Val) and c.272G>A(p.Arg91His). To our knowledge,the latter missense mutation has never been previously reported.

CONCLUSION

This is the second report of adult-onset vanishing white matter disease due to mutations in EIF2B3 and the first report of the c.272G>A (p.Arg91His) missense mutation.

An unmasked mutation of EIF2B2 due to submicroscopic deletion of 14q24.3 in a patient with vanishing white matter disease

Leukodystrophy with vanishing white matter (VWM) is a neurodegenerative disorder with autosomal recessive traits that is caused by alteration of the eukaryotic translation initiation factor-2B (EIF2B). An 11-month-old patient with distinctive features began to exhibit progressive developmental deterioration associated with intractable epilepsy, which was triggered by recurrent acute infectious diseases. Brain magnetic resonance imaging (MRI) revealed abnormal white matter intensity. Chromosomal microarray testing identified a submicroscopic deletion at 14q24.3 that included EIF2B2, the gene encoding one of the subunits of EIF2B. Because the patient's clinical findings were distinctive for VWM, compound heterozygous mutations of EIF2B2 were suspected, and subsequent sequencing analysis of the remaining allele unmasked the existence of a novel missense mutation of EIF2B2 (V85W). Some distinctive features including small palpebral fissures, bushy eyebrows, ear abnormalities, small upturned nose, downturned corners of the mouth, and micrognathia may be the common features of the patients with 14q24.3 deletions.

Late onset vanishing white matter disease presenting with learning difficulties

BACKGROUND

Vanishing white matter is an inherited leukoencephalopathy with typical childhood onset. Late onset forms are rare and may present with an extended range of phenotypes. Case report We present a patient born to consanguineous parents who developed learning disabilities by the age of 16 years. At the age of 25 she had a focal motor seizure with subsequent hemiparesis. After an extensive investigation she was diagnosed and treated as multiple sclerosis. There was progressive memory and planning impairment and, six years later, Sjögren syndrome with central nervous system involvement was diagnosed. For six months she was treated with cyclophosphamide, without any improvement. The next two years she had major clinical deterioration following infections. A homozygous mutation was identified in the EIF2B5 gene at the age of 33, and she died a year later.

CONCLUSIONS

VWM leukoencephalopathy is still largely recognized as a pediatric disorder, with many adult neurologists being unfamiliar with the late onset presentations. We wish to draw attention into these forms, avoiding submitting these patients to extensive workup and unnecessary treatments.

Vanishing white matter: the next 10 years

Vanishing white matter (VWM) is an inherited and often severe brain disease. It is caused by mutations in the genes for eIF2B, a protein that plays a key role in mRNA translation. The age of onset and clinical features are highly variable. In severe cases, onset may be antenatal and other organs are affected. The main feature is always a progressive encephalopathy, faster deterioration being provoked by head injury or febrile infections. The myelinating cells, oligodendrocytes, are affected in VWM. Initial studies suggested that VWM mutations decreased eIF2B’s activity. However, recent findings indicate that the situation is more complex. Studies in human brain samples or a mouse model for VWM indicate that development of astroglial cells and oligodendrocytes is impaired. Defects in eIF2B likely affect cell stress pathways and the expression of specific proteins, although their identities remain unknown.

Imaging evidence of early brain tissue degeneration in patients with vanishing white matter disease: a multimodal MR study

To find imaging signs of active degenerative processes in vanishing white matter disease (VWM), six VWM patients and six matched controls underwent MR examinations. The data were analyzed with modified Scheltens scales for morphological findings and determined quantitatively for apparent diffusion coefficient (ADC). Single-voxel MR spectra were acquired at the parietal white matter and analyzed with LCModel. Typical VWM brain lesions were found in all patients accompanied by proton diffusion abnormalities: Increased ADC appeared in brain regions with severe myelin destruction in all patients, and reduced ADC in two of six younger patients in remaining white matter adjacent to the lesions or at the borders around the lesions, who had a short history of the disease (≤ 1 year). The MR spectroscopy revealed reductions of NAA, Cho, and Cr, which correlate to the grade of white matter abnormalities. An increase of myo-inositol as marker of reactive gliosis was missing. Thus, restricted proton diffusion was evident in younger VWM patients with short history of disease, which in combination with lack of reactive gliosis may reflect early white matter degeneration in VWM. The multimodal MR methods are useful for characterizing such tissue degeneration in brain in vivo.

Ovarioleukodystrophy: report of a case with the c.338G>A (p.Arg113His) mutation on exon 3 and the c.896G>A (p.Arg299His) mutation on exon 7 of the EIF2B5 gene

The authors present a 28-year-old lady with progressive neurological deterioration beginning in childhood. She had clinical, radiological and genetic features of ovarioleukodystrophy. This is part of the spectrum of vanishing white matter disease and the first such case reported in the UK. The authors also discuss the literature on the disease.