Neurologic phenotypes associated with COL4A1/2 mutations: Expanding the spectrum of disease

Objective

To characterize the neurologic phenotypes associated with COL4A1/2 mutations and to seek genotype–phenotype correlation.

Methods

We analyzed clinical, EEG, and neuroimaging data of 44 new and 55 previously reported patients with COL4A1/COL4A2 mutations.

Results

Childhood-onset focal seizures, frequently complicated by status epilepticus and resistance to antiepileptic drugs, was the most common phenotype. EEG typically showed focal epileptiform discharges in the context of other abnormalities, including generalized sharp waves or slowing. In 46.4% of new patients with focal seizures, porencephalic cysts on brain MRI colocalized with the area of the focal epileptiform discharges. In patients with porencephalic cysts, brain MRI frequently also showed extensive white matter abnormalities, consistent with the finding of diffuse cerebral disturbance on EEG. Notably, we also identified a subgroup of patients with epilepsy as their main clinical feature, in which brain MRI showed nonspecific findings, in particular periventricular leukoencephalopathy and ventricular asymmetry. Analysis of 15 pedigrees suggested a worsening of the severity of clinical phenotype in succeeding generations, particularly when maternally inherited. Mutations associated with epilepsy were spread across COL4A1 and a clear genotype–phenotype correlation did not emerge.

Conclusion

COL4A1/COL4A2 mutations typically cause a severe neurologic condition and a broader spectrum of milder phenotypes, in which epilepsy is the predominant feature. Early identification of patients carrying COL4A1/COL4A2 mutations may have important clinical consequences, while for research efforts, omission from large-scale epilepsy sequencing studies of individuals with abnormalities on brain MRI may generate misleading estimates of the genetic contribution to the epilepsies overall.

Bi-allelic Mutations in NDUFA6 Establish Its Role in Early-Onset Isolated Mitochondrial Complex I Deficiency

Isolated complex I deficiency is a common biochemical phenotype observed in pediatric mitochondrial disease and often arises as a consequence of pathogenic variants affecting one of the ∼65 genes encoding the complex I structural subunits or assembly factors. Such genetic heterogeneity means that application of next-generation sequencing technologies to undiagnosed cohorts has been a catalyst for genetic diagnosis and gene-disease associations. We describe the clinical and molecular genetic investigations of four unrelated children who presented with neuroradiological findings and/or elevated lactate levels, highly suggestive of an underlying mitochondrial diagnosis. Next-generation sequencing identified bi-allelic variants in NDUFA6, encoding a 15 kDa LYR-motif-containing complex I subunit that forms part of the Q-module. Functional investigations using subjects’ fibroblast cell lines demonstrated complex I assembly defects, which were characterized in detail by mass-spectrometry-based complexome profiling. This confirmed a marked reduction in incorporated NDUFA6 and a concomitant reduction in other Q-module subunits, including NDUFAB1, NDUFA7, and NDUFA12. Lentiviral transduction of subjects’ fibroblasts showed normalization of complex I. These data also support supercomplex formation, whereby the ∼830 kDa complex I intermediate (consisting of the P- and Q-modules) is in complex with assembled complex III and IV holoenzymes despite lacking the N-module. Interestingly, RNA-sequencing data provided evidence that the consensus RefSeq accession number does not correspond to the predominant transcript in clinically relevant tissues, prompting revision of the NDUFA6 RefSeq transcript and highlighting not only the importance of thorough variant interpretation but also the assessment of appropriate transcripts for analysis.

Trial of Fingolimod versus Interferon Beta-1a in Pediatric Multiple Sclerosis

BACKGROUND

Treatment of patients younger than 18 years of age with multiple sclerosis has not been adequately examined in randomized trials. We compared fingolimod with interferon beta-1a in this population.

METHODS

In this phase 3 trial, we randomly assigned patients 10 to 17 years of age with relapsing multiple sclerosis in a 1:1 ratio to receive oral fingolimod at a dose of 0.5 mg per day (0.25 mg per day for patients with a body weight of ≤40 kg) or intramuscular interferon beta-1a at a dose of 30 μg per week for up to 2 years. The primary end point was the annualized relapse rate.

RESULTS

Of a total of 215 patients, 107 were assigned to fingolimod and 108 to interferon beta-1a. The mean age of the patients was 15.3 years. Among all patients, there was a mean of 2.4 relapses during the preceding 2 years. The adjusted annualized relapse rate was 0.12 with fingolimod and 0.67 with interferon beta-1a (absolute difference, 0.55 relapses; relative difference, 82%; P<0.001). The key secondary end point of the annualized rate of new or newly enlarged lesions on T₂-weighted magnetic resonance imaging (MRI) was 4.39 with fingolimod and 9.27 with interferon beta-1a (absolute difference, 4.88 lesions; relative difference, 53%; P<0.001). Adverse events, excluding relapses of multiple sclerosis, occurred in 88.8% of patients who received fingolimod and 95.3% of those who received interferon beta-1a. Serious adverse events occurred in 18 patients (16.8%) in the fingolimod group and included seizures (in 4 patients), infection (in 4 patients), and leukopenia (in 2 patients). Serious adverse events occurred in 7 patients (6.5%) in the interferon beta-1a group and included infection (in 2 patients) and supraventricular tachycardia (in 1 patient).

CONCLUSIONS

Among pediatric patients with relapsing multiple sclerosis, fingolimod was associated with a lower rate of relapse and less accumulation of lesions on MRI over a 2-year period than interferon beta-1a but was associated with a higher rate of serious adverse events. Longer studies are required to determine the durability and safety of fingolimod in pediatric multiple sclerosis. (Funded by Novartis Pharma; PARADIGMS ClinicalTrials.gov number, NCT01892722 .).

Molecularly defined diffuse leptomeningeal glioneuronal tumor (DLGNT) comprises two subgroups with distinct clinical and genetic features

Diffuse leptomeningeal glioneuronal tumors (DLGNT) represent rare CNS neoplasms which have been included in the 2016 update of the WHO classification. The wide spectrum of histopathological and radiological features can make this enigmatic tumor entity difficult to diagnose. In recent years, large-scale genomic and epigenomic analyses have afforded insight into key genetic alterations occurring in multiple types of brain tumors and provide unbiased, complementary tools to improve diagnostic accuracy. Through genome-wide DNA methylation screening of > 25,000 tumors, we discovered a molecularly distinct class comprising 30 tumors, mostly diagnosed histologically as DLGNTs. Copy-number profiles derived from the methylation arrays revealed unifying characteristics, including loss of chromosomal arm 1p in all cases. Furthermore, this molecular DLGNT class can be subdivided into two subgroups [DLGNT methylation class (MC)-1 and DLGNT methylation class (MC)-2], with all DLGNT-MC-2 additionally displaying a gain of chromosomal arm 1q. Co-deletion of 1p/19q, commonly seen in IDH-mutant oligodendroglioma, was frequently observed in DLGNT, especially in DLGNT-MC-1 cases. Both subgroups also had recurrent genetic alterations leading to an aberrant MAPK/ERK pathway, with KIAA1549:BRAF fusion being the most frequent event. Other alterations included fusions of NTRK1/2/3 and TRIM33:RAF1, adding up to an MAPK/ERK pathway activation identified in 80% of cases. In the DLGNT-MC-1 group, age at diagnosis was significantly lower (median 5 vs 14 years, p < 0.01) and clinical course less aggressive (5-year OS 100, vs 43% in DLGNT-MC-2). Our study proposes an additional molecular layer to the current histopathological classification of DLGNT, of particular use for cases without typical morphological or radiological characteristics, such as diffuse growth and radiologic leptomeningeal dissemination. Recurrent 1p deletion and MAPK/ERK pathway activation represent diagnostic biomarkers and therapeutic targets, respectively-laying the foundation for future clinical trials with, e.g., MEK inhibitors that may improve the clinical outcome of patients with DLGNT.

Potential Risks to Stable Long-term Outcome of Allogeneic Hematopoietic Stem Cell Transplantation for Children With Cerebral X-linked Adrenoleukodystrophy

IMPORTANCE

Allogeneic hematopoietic stem cell transplantation is the standard intervention for childhood cerebral X-linked adrenoleukodystrophy. However, the pretransplant conditions, demyelination patterns, complications, and neurological outcomes of this therapy are not well characterized.

OBJECTIVES

To identify the risks to stable neurocognitive survival after hematopoietic stem cell transplantation and to describe subgroups of patients with distinct clinical long-term outcomes.

DESIGN, SETTING, AND PARTICIPANTS

This case series analyzed the treatment and outcome of a cohort of 36 boys who underwent hematopoietic stem cell transplantation at Charité Universitätsmedizin Berlin, Germany, between January 1, 1997, and October 31, 2014. Case analysis was performed from January 1, 2016, through November 30, 2017. During this retrospective review, the adrenoleukodystrophy-disability rating score and the neurological function score were used. Demyelinating lesions in the brain were quantified by the Loes score.

MAIN OUTCOMES AND MEASURES

Overall survival, survival without major functional disabilities, and event-free survival were analyzed. Patients' clinical symptoms, demyelination patterns, and stem cell source were stratified.

RESULTS

Of the 36 boys who underwent hematopoietic stem cell transplantation, the median (range) age was 7.2 (4.2-15.4) years; 18 were presymptomatic and 18 were symptomatic. Twenty-seven patients (75%) were alive at a median (interquartile range [IQR]) follow-up of 108 (40-157) months. Sixteen of 18 presymptomatic patients (89%) survived, and 13 (72%) had an event-free survival with a median (IQR) survival time of 49 (37-115) months. Among the symptomatic patients, 11 of 18 (61%) survived, but only 1 was an event-free survival (6%) (median [IQR] time, 9 [3-22] months). Of the 9 patients who received a bone marrow transplant from a matched family donor, all survived. Among the 36 patients, 6 disease-related deaths (17%) and 3 transplant-related deaths (8%) occurred. Deaths from disease progression (n = 6) occurred only in patients with demyelination patterns other than parieto-occipital. In total, 18 patients (50%) displayed limited parieto-occipital (Loes score <9) or frontal (Loes score <4) demyelination before transplant (favorable). None of these patients died of progressive disease or developed major functional disabilities, 15 of them were characterized by stable neuroimaging after the transplant, and event-free survival was 77% (95% CI, 60%-100%). In contrast, the other 18 patients with more extended parieto-occipital demyelination (n = 6), frontal involvement (n = 4), or other demyelination patterns (n = 8) progressed (unfavorable): 13 patients developed epilepsy and 10 developed major functional disabilities, and their event-free survival was 0%. This newly defined neuroimaging assessment correlated best with neurocognitive deterioration after transplant (hazard ratio, 16.7; 95% CI, 4.7-59.6).

CONCLUSIONS AND RELEVANCE

All patients with favorable neuroimaging who received matched bone marrow remained stable after transplant, while some of the other patients developed major functional disabilities. Newborn screening for the disease and regular neuroimaging are recommended, and patients who lack a matched bone marrow donor may need to find new therapeutic options.

Relapse Rate and MRI Activity in Young Adult Patients With Multiple Sclerosis: A Post Hoc Analysis of Phase 3 Fingolimod Trials

Background

Disease activity differs in young patients with multiple sclerosis (MS) compared with the overall adult MS population.

Objective

The objective of this paper is to evaluate the effect of fingolimod 0.5 mg on disease activity in young adults with MS from three randomized, double-blind Phase 3 trials.

Methods

Annualized relapse rate (ARR), number of new/newly enlarging T2 lesions (neT2), and no evidence of disease activity (NEDA-3) were estimated in the intent-to-treat population at age 20 (youngest) and 30 (young) and compared to the overall population. Models used included a negative binomial regression (ARR/neT2) and a logistic regression (NEDA), with age at baseline as a continuous covariate.

Results

ARRs were higher in younger patients (all p < 0.05), and significantly reduced with fingolimod versus placebo or interferon beta-1a (IFN β-1a), with the percentage reduction inversely proportional to age. Fingolimod was significantly associated with a lower number of neT2 lesions versus placebo/IFN in all age groups except versus IFN in the youngest patients. Regardless of age, fingolimod-treated patients were more likely to achieve NEDA-3 versus placebo/IFN β-1a, with strongest benefits in the youngest patients (all p < 0.05).

Conclusions

Young adults show higher levels of MS disease activity, and may particularly benefit from fingolimod treatment compared with the overall study population.

Super-resolution imaging reveals the sub-diffraction phenotype of Zellweger Syndrome ghosts and wild-type peroxisomes

Peroxisomes are ubiquitous cell organelles involved in many metabolic and signaling functions. Their assembly requires peroxins, encoded by PEX genes. Mutations in PEX genes are the cause of Zellweger Syndrome spectrum (ZSS), a heterogeneous group of peroxisomal biogenesis disorders (PBD). The size and morphological features of peroxisomes are below the diffraction limit of light, which makes them attractive for super-resolution imaging. We applied Stimulated Emission Depletion (STED) microscopy to study the morphology of human peroxisomes and peroxisomal protein localization in human controls and ZSS patients. We defined the peroxisome morphology in healthy skin fibroblasts and the sub-diffraction phenotype of residual peroxisomal structures (‘ghosts’) in ZSS patients that revealed a relation between mutation severity and clinical phenotype. Further, we investigated the 70 kDa peroxisomal membrane protein (PMP70) abundance in relationship to the ZSS sub-diffraction phenotype. This work improves the morphological definition of peroxisomes. It expands current knowledge about peroxisome biogenesis and ZSS pathoethiology to the sub-diffraction phenotype including key peroxins and the characteristics of ghost peroxisomes.

Respiration and the watershed of spinal CSF flow in humans

The dynamics of human CSF in brain and upper spinal canal are regulated by inspiration and connected to the venous system through associated pressure changes. Upward CSF flow into the head during inspiration counterbalances venous flow out of the brain. Here, we investigated CSF motion along the spinal canal by real-time phase-contrast flow MRI at high spatial and temporal resolution. Results reveal a watershed of spinal CSF dynamics which divides flow behavior at about the level of the heart. While forced inspiration prompts upward surge of CSF flow volumes in the entire spinal canal, ensuing expiration leads to pronounced downward CSF flow, but only in the lower canal. The resulting pattern of net flow volumes during forced respiration yields upward CSF motion in the upper and downward flow in the lower spinal canal. These observations most likely reflect closely coupled CSF and venous systems as both large caval veins and their anastomosing vertebral plexus react to respiration-induced pressure changes.

Cognitive deficits including executive functioning in relation to clinical parameters in paediatric MS patients

Background

A number of studies have investigated cognitive impairment in paediatric patients with multiple sclerosis (MS) but deficits regarding executive functions have not been comprehensively assessed up to now. This study was meant to explore cognitive impairment in German paediatric MS patients with a focus on deficits in executive functions and relate these to clinical disease parameters.

Methods and findings

Forty paediatric MS patients, which presented at the German centre for MS in childhood and adolescence, were assessed for cognitive deficits applying a very comprehensive battery of cognitive tests including the Wechsler Intelligence scale and subtests of the D-KEFS for executive functions. The performance of MS patients was compared with a group of age and sex matched healthy controls using between-subjects ANOVAs. Paediatric MS patients performed worse in tests assessing verbal comprehension and fluency, processing speed, memory, calculation skills and other executive functions. Arranged by the cognitive domain, group differences were most pronounced regarding verbal comprehension and fluency for the WISC subtests Comprehension (p = 0.000), Vocabulary (p = 0.003) and Information (p = 0.005); regarding processing speed for the written SDMT (p = 0.001) and the WISC subtest Coding (p = 0.005); regarding memory for the VLMT training (p = 0.007) and the BASIC MLT pattern learning training (p = 0.009); regarding executive functions including working memory for the WISC subtest Arithmetics (p = 0.002), the D-KEFS Design Fluency (p = 0.003) and the Corsi block tapping backward task (p = 0.003). Fluid reasoning was largely intact. Relations of cognitive performance and clinical parameters were assessed in MS patients. Disease duration was associated with a reduced performance in tests belonging to the domains verbal comprehension and fluency (WISC Vocabulary: p = 0.034, WISC Information: p = 0.015) and fluid reasoning (WISC Picture Completion: p = 0.003) as well as the WISC Working Memory Index (p = 0.047). Patients with a disease onset between 11 and 14 years performed better in fluid reasoning (WISC matrix reasoning: p = 0.024) than patients with a disease onset at an age above 14. The number of relapses negatively influenced the visual spatial memory performance (BASIC MLT pattern learning training: p = 0.009).

Conclusions

The distribution of cognitive deficits in a representative group German of paediatric MS patients was similar to the pattern known from other European and North-American cohorts. Paediatric MS patients do have cognitive deficits in executive functions and key qualities necessary for successful school performance. Disease duration, age of onset and the number of relapses influence cognitive performance. Cognitive screenings should be implemented on a regular basis for paediatric MS patients, enabling early intervention.

Interferon beta-1b in treatment-naïve paediatric patients with relapsing-remitting multiple sclerosis: Two-year results from the BETAPAEDIC study

Background and objective

Study evaluating Betaferon(R)'s safety and tolerability in paediatric patients with multiple sclerosis (BETAPAEDIC) is a prospective, open-label observational multicentre study to assess the safety and effectiveness of interferon beta-1b in paediatric patients with relapsing-remitting multiple sclerosis.

Methods

Treatment-naïve patients (12-16 years) scheduled to start interferon beta-1b were enrolled with follow-up visits every six months for two years. Effectiveness was evaluated by annualised relapse rate, Expanded Disability Status Scale progression, cranial magnetic resonance imaging and cognitive testing. Fatigue was assessed by the Fatigue Severity Scale.

Results

Sixty-eight patients were screened and 67 enrolled, with mean (standard deviation) age 14.2 (1.3) years (n=65 in the effectiveness analysis). Mean disease duration was 11 months before study enrolment; at baseline, mean (standard deviation) Expanded Disability Status Scale was 0.6 (1.0); T2 lesion number 18.3 (15.1). Mean annualised relapse rate during the study was 0.7 (n=57), 28/57 patients (49.1%) had no relapses and for 40/52 (76.9%) no Expanded Disability Status Scale progression was observed; 23/56 (41.1%) were relapse- and progression-free to last follow-up. Neuropsychological test and fatigue scores were within normal ranges (baseline and last follow-up). Eighteen patients had fatigue at some point. New T2 and gadolinium-enhancing (Gd+) lesions were seen in 43/55 (66.2%) and 29/55 (52.7%) patients respectively. Most frequent adverse events were influenza-like illness, headache, injection-site reactions and elevated liver enzymes.

Conclusion

Interferon beta-1b is an effective treatment with a favourable safety profile for paediatric patients.

The functional readthrough extension of malate dehydrogenase reveals a modification of the genetic code

Translational readthrough gives rise to C-terminally extended proteins, thereby providing the cell with new protein isoforms. These may have different properties from the parental proteins if the extensions contain functional domains. While for most genes amino acid incorporation at the stop codon is far lower than 0.1%, about 4% of malate dehydrogenase (MDH1) is physiologically extended by translational readthrough and the actual ratio of MDH1x (extended protein) to ‘normal' MDH1 is dependent on the cell type. In human cells, arginine and tryptophan are co-encoded by the MDH1x UGA stop codon. Readthrough is controlled by the 7-nucleotide high-readthrough stop codon context without contribution of the subsequent 50 nucleotides encoding the extension. All vertebrate MDH1x is directed to peroxisomes via a hidden peroxisomal targeting signal (PTS) in the readthrough extension, which is more highly conserved than the extension of lactate dehydrogenase B. The hidden PTS of non-mammalian MDH1x evolved to be more efficient than the PTS of mammalian MDH1x. These results provide insight into the genetic and functional co-evolution of these dually localized dehydrogenases.

Cathepsin D Polymorphism C224T in Childhood-Onset Neurodegenerative Disorders: No Impact for Childhood Dementia

Compromised lysosomal functioning has been identified as a major risk factor for neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Furthermore, the association between a defined cathepsin D ( CTSD ) polymorphism and a higher risk of sporadic Alzheimer's disease has been established for particular populations. Here, we analyzed 189 children with rare neurodegenerative disease for carrying the T-allele by polymerase chain reaction-restriction fragment length polymorphism. We found no statistical differences in genotype and allele frequencies between the neurodegenerative group and European descent participants of genetic studies using the Cochran-Armitage's trend test. In contrast to adult-onset neurodegenerative diseases, analysis of clinical datasets of children carrying the T-allele did not demonstrate differences to the general disease group.

Activating de novo mutations in NFE2L2 encoding NRF2 cause a multisystem disorder

Transcription factor NRF2, encoded by NFE2L2, is the master regulator of defense against stress in mammalian cells. Somatic mutations of NFE2L2 leading to NRF2 accumulation promote cell survival and drug resistance in cancer cells. Here we show that the same mutations as inborn de novo mutations cause an early onset multisystem disorder with failure to thrive, immunodeficiency and neurological symptoms. NRF2 accumulation leads to widespread misregulation of gene expression and an imbalance in cytosolic redox balance. The unique combination of white matter lesions, hypohomocysteinaemia and increased G-6-P-dehydrogenase activity will facilitate early diagnosis and therapeutic intervention of this novel disorder.

The NRF2 transcription factor regulates the response to stress in mammalian cells. Here, the authors show that activating mutations in NRF2, commonly found in cancer cells, are found in four patients with a multisystem disorder characterized by immunodeficiency and neurological symptoms.

Therapy of highly active pediatric multiple sclerosis

Objective:

Study aims were to determine the frequency of highly active disease in pediatric multiple sclerosis (MS), the response to natalizumab (NTZ) and fingolimod (FTY) treatment, and the impact of current treatment modalities on the clinical course.

Methods:

Retrospective single-center study in the German Center for MS in Childhood and Adolescence.

Results:

Of 144 patients with first MS manifestation between 2011 and 2015, 41.6% fulfilled the criteria for highly active MS. In total, 55 patients treated with NTZ and 23 with FTY demonstrated a significant reduction in relapse rate (NTZ: 95.2%, FTY: 75%), new T2 lesions (NTZ: 97%, FTY: 81%), and contrast-enhancing lesions (NTZ: 97%, FTY: 93%). However, seven patients switched from NTZ to FTY experienced an increase in disease activity. Comparing pediatric MS patients treated in 2005 with those treated in 2015 showed a 46% reduction in relapse rate and a 44% reduction in mean Expanded Disability Status Scale (EDSS).

Conclusion:

The rate of highly active disease among pediatric MS patients is high; more than 40% in our cohort. Response to NTZ and FTY treatment is similar if not better than observed in adults. Current treatment modalities including earlier treatment initiation and the introduction of NTZ and FTY have significantly improved the clinical course of pediatric MS.

A new CUL4B variant associated with a mild phenotype and an exceptional pattern of leukoencephalopathy

Cabezas type of X-linked syndromic intellectual disability (MRXSC; MIM300354) is a rare X-linked recessive intellectual disability characterized primarily by intellectual disability, short stature, hypogonadism, and gait abnormalities. It is caused by a wide spectrum of hemizygous variants in CUL4B. In a 10-year-old boy with an exceptional leukoencephalopathy pattern, we identified a new missense variant p.Leu329Gln in CUL4B using "Mendeliome" sequencing. However, his phenotype does not include the severe characteristics currently known for MRXSC. We discuss the divergent phenotype and propose a potential connection between the different CUL4B variants and corresponding phenotypes in the context of the current literature as well as 3D homology modeling.

Dysferlin mediates membrane tubulation and links T-tubule biogenesis to muscular dystrophy

The multi-C2 domain protein dysferlin localizes to the plasma membrane and the T-tubule system in skeletal muscle; however, its physiological mode of action is unknown. Mutations in the DYSF gene lead to autosomal recessive limb-girdle muscular dystrophy type 2B and Miyoshi myopathy. Here, we show that dysferlin has membrane tubulating capacity and that it shapes the T-tubule system. Dysferlin tubulates liposomes, generates a T-tubule-like membrane system in non-muscle cells, and links the recruitment of phosphatidylinositol 4,5-bisphosphate to the biogenesis of the T-tubule system. Pathogenic mutant forms interfere with all of these functions, indicating that muscular wasting and dystrophy are caused by the dysferlin mutants' inability to form a functional T-tubule membrane system.

STAR syndrome-associated CDK10/Cyclin M regulates actin network architecture and ciliogenesis

CDK10/CycM is a protein kinase deficient in STAR (toe Syndactyly, Telecanthus and Anogenital and Renal malformations) syndrome, which results from mutations in the X-linked FAM58A gene encoding Cyclin M. The biological functions of CDK10/CycM and etiology of STAR syndrome are poorly understood. Here, we report that deficiency of CDK10/Cyclin M promotes assembly and elongation of primary cilia. We establish that this reflects a key role for CDK10/Cyclin M in regulation of actin network organization, which is known to govern ciliogenesis. In an unbiased screen, we identified the RhoA-associated kinase PKN2 as a CDK10/CycM phosphorylation substrate. We establish that PKN2 is a bone fide regulator of ciliogenesis, acting in a similar manner to CDK10/CycM. We discovered that CDK10/Cyclin M binds and phosphorylates PKN2 on threonines 121 and 124, within PKN2's core RhoA-binding domain. Furthermore, we demonstrate that deficiencies in CDK10/CycM or PKN2, or expression of a non-phosphorylatable version of PKN2, destabilize both the RhoA protein and the actin network architecture. Importantly, we established that ectopic expression of RhoA is sufficient to override the induction of ciliogenesis resulting from CDK10/CycM knockdown, indicating that RhoA regulation is critical for CDK10/CycM's negative effect on ciliogenesis. Finally, we show that kidney sections from a STAR patient display dilated renal tubules and abnormal, elongated cilia. Altogether, these results reveal CDK10/CycM as a key regulator of actin dynamics and a suppressor of ciliogenesis through phosphorylation of PKN2 and promotion of RhoA signaling. Moreover, they suggest that STAR syndrome is a ciliopathy.

Diagnostic and prognostic value of in vivo proton MR spectroscopy for Zellweger syndrome spectrum patients

Defects in the biogenesis of peroxisomes cause a clinically and genetically heterogeneous group of neurometabolic disorders, the Zellweger syndrome spectrum (ZSS). Diagnosis predominantly is based on characteristic clinical symptoms, a typical biochemical profile, as well as on identification of the molecular defect in any of the 12 known human PEX genes. The diagnostic workup can be hindered if the typical clinical symptoms are missing and predicting the clinical course of a given patient is almost unfeasible. As a safe and noninvasive method to analyze specific chemical compounds in localized brain regions, in vivo proton magnetic resonance spectroscopy (MRS) can provide an indication in this diagnostic process and may help predict the clinical course. However, to date, there are very few reports on this topic. In this study, we performed localized in vivo proton MRS without confounding contributions from T1- and T2-relaxation effects at 2 Tesla in a comparably large group of seven ZSS patients. Patients' absolute metabolite concentrations in cortical gray matter, white matter, and basal ganglia were assessed and compared with age-matched control values. Our results confirm and extend knowledge about in vivo MRS findings in ZSS patients. Besides affirmation of nonspecific reduction of N-acetylaspartate + N-acetylaspartylglutamate (tNAA) in combination with lipid accumulation as a diagnostic hint for this disease group, the amount of tNAA loss seems to reflect disease burden and may prove to be of prognostic value regarding the clinical course of an already diagnosed patient.

Compound heterozygous variants in PGAP1 causing severe psychomotor retardation, brain atrophy, recurrent apneas and delayed myelination: a case report and literature review

Background

Mutations in proteins involved in the glycosylphosphatidylinositol anchor biosynthesis and remodeling pathway are associated with autosomal recessive forms of intellectual disability. Recently mutations in the PGAP1 gene that codes for PGAP1, a protein localized in the endoplasmic reticulum responsible for the first step of the remodeling of glycosylphosphatidylinositol was linked to a disorder characterized by psychomotor retardation and facial dysmorphism. Whole exome sequencing (WES) was performed in siblings with severely delayed myelination and psychomotor retardation. Mutations in PGAP1 were confirmed by Sanger sequencing and RNA analysis. A literature search was performed to describe the emerging phenotype of PGAP1 related disease.

Case presentation

WES resulted in the detection of two novel compound heterozygous mutations in PGAP1, one base pair insertion leading to a frame shift c.334_335InsA (p.A112fs) and a splice site mutation leading to exon skipping c.G1173C (p.L391L). A symptom not described in PGAP1 related disorder before but prominent in the siblings were recurrent apnea especially during sleep that persisted at least until age 2 years. Sequential cerebral MRI at age one and two year(s) respectively revealed frontal accentuated brain atrophy and significantly delayed myelination.

Conclusion

We report siblings with two novel mutations in PGAP1. Other that the common symptoms related to PGAP1 mutations including non-progressive psychomotor retardation, neonatal feeding problems, microcephaly and brain atrophy these patients displayed severely delayed myelination and recurrent apneas thereby widing the clinical spectrum associated with such mutations.

Electronic supplementary material

The online version of this article (doi:10.1186/s12883-016-0602-7) contains supplementary material, which is available to authorized users.

[State of integration of palliative care at Comprehensive Cancer Centers funded by German Cancer Aid]

BACKGROUND

Similarities and differences of integration of palliative care in clinical care, research and education structures at German Comprehensive Cancer Centers (CCC) are not known in detail.

OBJECTIVE

Provide an overview of availability and the way of integration of specialized palliative care at CCCs funded by the German Cancer Aid (Deutsche Krebshilfe, DKH).

METHOD

We conducted structured interviews from May to August 2014 with heads of palliative care departments (personally or by telephone). The interviews included a quantitative and a qualitative part. Other stakeholders of CCCs were asked the questions of the qualitative part. We evaluated the qualitative data using the content analysis by Mayring and MAXQDA 11.0. SPSS 21.0 was used for quantitative analysis.

RESULTS

26 interviews were realized in 13 CCCs with 14 sites, which received funding, by DKH till August 2014 (one CCC had two university hospitals). Of these, 12 sites had a palliative care unit (86%), 11 sites had palliative care consulting services available (79%). Participation of palliative care specialists in tumor boards is not provided in 3 institutions (21%) and is often not feasible on regular basis in the other institutions, due to staffing shortage. In 7 sites (50%) defined criteria to integrate palliative care into CCCs were available. In the last 5 years specialized palliative care of 4 sites received an invitation for a research project by another department within the CCC (29%). 10 sites (71%) had started own palliative care research projects. Chairs in palliative care were available in 4 CCCs (29%).

CONCLUSION

The extent and depth of palliative care integration in the 14 CCC sites is heterogeneous.

Leukoencephalopathy and early death associated with an Ashkenazi-Jewish founder mutation in the Hikeshi gene

BACKGROUND

Leukodystrophies are genetic white matter disorders affecting the formation or maintenance of myelin. Among the recently discovered genetic defects associated with leukodystrophies, several genes converge on a common mechanism involving protein transcription/translation and ER stress response.

METHODS

The genetic basis of a novel congenital leukodystrophy, associated with early onset spastic paraparesis, acquired microcephaly and optic atrophy was studied in six patients from three unrelated Ashkenazi-Jewish families. To this end we used homozygosity mapping, exome analysis, western blot (Hikeshi, HSF1-pS326 and b-actin) in patient fibroblasts, indirect immunofluorescence (HSP70 and HSF1) in patient fibroblasts undergoing heat shock stress, nuclear injection of plasmids expressing Hikeshi or EGFP in patient fibroblasts, in situ hybridization and Immunoblot analysis of Hikeshi in newborn and adult mouse brain.

RESULTS

All the patients were homozygous for a missense mutation, p.Val54Leu, in C11ORF73 encoding HSP70 nuclear transporter protein, Hikeshi. The mutation segregated with the disease in the families and was carried by 1:200 Ashkenazi-Jewish individuals. The mutation was associated with undetectable level of Hikeshi in the patients' fibroblasts and with lack of nuclear HSP70 during heat shock stress, a phenomenon which was reversed upon the introduction of normal human Hikeshi to the patients cells. Hikeshi was found to be expressed in central white matter of mouse brain.

CONCLUSIONS

These data underscore the importance of Hikeshi for HSP70 relocation into the nucleus. It is likely that in the absence of Hikeshi, HSP70 cannot attenuate the multiple heat shock induced nuclear phenotypes, leaving the cells unprotected during heat shock stress. We speculate that the sudden death of three of the six patients following a short febrile illness and the life-threatening myo-pericarditis in the fourth are the result of excess extra-nuclear HSP70 level which initiates cytokine release or provide target for natural killer cells. Alternatively, nuclear HSP70 might play an active role in stressed cells protection.

Obtaining a genetic diagnosis in a child with disability: impact on parental quality of life

Recent progress in genetic testing has facilitated obtaining an etiologic diagnosis in children with developmental delay/intellectual disability (DD/ID) or multiple congenital anomalies (MCA) or both. Little is known about the benefits of diagnostic elucidation for affected families. We studied the impact of a genetic diagnosis on parental quality of life (QoL) using a validated semiquantitative questionnaire in families with a disabled child investigated by array-based comparative genomic hybridization (aCGH). We received completed questionnaires from 95 mothers and 76 fathers of 99 families. We used multivariate analysis for adjustment of potential confounders. Taken all 99 families together, maternal QoL score (percentile rank scale 51.05) was significantly lower than fathers' QoL (61.83, p = 0.01). Maternal QoL score was 20.17 [95% CI (5.49; 34.82)] percentile rank scales higher in mothers of children with diagnostic (n = 34) aCGH as opposed to mothers of children with inconclusive (n = 65) aCGH (Hedges' g = 0.71). Comparison of these QoL scores with retrospectively recalled QoL before aCGH revealed an increase of maternal QoL after diagnostic clarification. Our results indicate a benefit for maternal QoL if a genetic test, here aCGH, succeeds to clarify the etiologic diagnosis in a disabled child.

Extensive acute axonal damage in pediatric multiple sclerosis lesions

OBJECTIVE

Axonal damage occurs early in multiple sclerosis (MS) and contributes to the degree of clinical disability. Children with MS more often show disabling and polyfocal neurological symptoms at disease onset than adults with MS. Thus, axonal damage may differ between pediatric and adult MS patients.

METHODS

We analyzed axonal pathology in archival brain biopsy and autopsy samples from 19 children with early MS. Lesions were classified according to demyelinating activity and presence of remyelination. Axonal density and extent of acute axonal damage were assessed using Bielschowsky silver impregnation and immunohistochemistry for amyloid precursor protein (APP), respectively. Axonal injury was correlated with the inflammatory infiltrate as well as clinical characteristics. Results were compared with data from adult MS patients.

RESULTS

Acute axonal damage was most extensive in early active demyelinating (EA) lesions of pediatric patients and correlated positively with the Expanded Disability Status Scale at attack leading to biopsy/autopsy. Comparison with 12 adult patients showed a 50% increase in the extent of acute axonal damage in EA lesions from children compared to adults, with the highest number of APP-positive spheroids found prior to puberty. The extent of acute axonal damage correlated positively with the number of lesional macrophages. Axonal density was reduced in pediatric lesions irrespective of the demyelinating activity or the presence of remyelination. Axonal reduction was similar between children and adults.

INTERPRETATION

Our results provide evidence for more pronounced acute axonal damage in inflammatory demyelinating lesions from children compared to adults.

Characterization of the MeCP2R168X knockin mouse model for Rett syndrome

Rett syndrome, one of the most common causes of mental retardation in females, is caused by mutations in the X chromosomal gene MECP2. Mice deficient for MeCP2 recapitulate some of the symptoms seen in patients with Rett syndrome. It has been shown that reactivation of silent MECP2 alleles can reverse some of the symptoms in these mice. We have generated a knockin mouse model for translational research that carries the most common nonsense mutation in Rett syndrome, R168X. In this article we describe the phenotype of this mouse model. In male MeCP2(R168X) mice life span was reduced to 12-14 weeks and bodyweight was significantly lower than in wild type littermates. First symptoms including tremor, hind limb clasping and inactivity occurred at age 27 days. At age 6 weeks nest building, rotarod, open-field and elevated plus maze experiments showed impaired motor performance, reduced activity and decreased anxiety-like behavior. Plethysmography at the same time showed apneas and irregular breathing with reduced frequency. Female MeCP2R168X mice showed no significant abnormalities except decreased performance on the rotarod at age 9 months. In conclusion we show that the male MeCP2(R168X) mice have a phenotype similar to that seen in MECP2 knockout mouse models and are therefore well suited for translational research. The female mice, however, have a much milder and less constant phenotype making such research with this mouse model more challenging.

Peroxisomal lactate dehydrogenase is generated by translational readthrough in mammals

Translational readthrough gives rise to low abundance proteins with C-terminal extensions beyond the stop codon. To identify functional translational readthrough, we estimated the readthrough propensity (RTP) of all stop codon contexts of the human genome by a new regression model in silico, identified a nucleotide consensus motif for high RTP by using this model, and analyzed all readthrough extensions in silico with a new predictor for peroxisomal targeting signal type 1 (PTS1). Lactate dehydrogenase B (LDHB) showed the highest combined RTP and PTS1 probability. Experimentally we show that at least 1.6% of the total cellular LDHB is targeted to the peroxisome by a conserved hidden PTS1. The readthrough-extended lactate dehydrogenase subunit LDHBx can also co-import LDHA, the other LDH subunit, into peroxisomes. Peroxisomal LDH is conserved in mammals and likely contributes to redox equivalent regeneration in peroxisomes.

DOI:http://dx.doi.org/10.7554/eLife.03640.001

Amino acids are the building blocks of proteins, and the order of the amino acids in a protein is determined by the order in which ‘codons’ appear in a messenger RNA molecule. Most codons represent a specific amino acid, but there are also three stop codons that are used to mark the end of a protein.

When the cellular machinery that ‘translates’ the messenger RNA molecule into a protein encounters a stop codon, it stops and releases the completed protein. Sometimes, however, the stop codon is not interpreted as a stop signal, and the translation of the messenger RNA molecule continues until another stop codon is encountered. This process is known as readthrough.

Some organisms, in particular viruses and fungi, use readthrough to produce a wider range of proteins than their genomes would otherwise allow. While readthrough also occurs in higher organisms such as mammals, it is not known if the resulting proteins perform extra functions that the original protein does not perform.

A number of factors affect whether readthrough occurs when an mRNA template is being translated. For example, each of the three stop codons has a different likelihood of having its stop signal misinterpreted, and the mRNA sequence that surrounds the stop codon can also affect the likelihood of readthrough.

Schueren et al. have developed a computational model that estimates how common this form of translational readthrough is in the human genome. The model was based on the identity of the stop codons themselves and the surrounding mRNA sequence. This model was then combined with another model that identifies proteins that are targeted to a structure inside a cell called the peroxisome, which is where a number of essential energy-releasing reactions take place. The combined model enabled Schueren et al. to identify proteins that both perform functions in the peroxisome and are likely to be formed by readthrough.

The combined model suggested a protein that is a part of lactate dehydrogenase: an enzyme that speeds up chemical reactions that are important for the cell to produce energy. Low levels of lactate dehydrogenase had previously been found in the peroxisome, despite it apparently lacking a specific sequence of amino acids that proteins need to have to enter the peroxisome. However, Schueren et al. confirmed experimentally that readthrough does occur for the lactate dehydrogenase component identified by the model, revealing that it contains a ‘hidden’ peroxisome-targeting region. Furthermore, when more translational readthrough occurred, more lactate dehydrogenase was found in the peroxisomes.

This unusual way that lactate dehydrogenase enters the peroxisome is an example of how the cell optimizes the used of the genetic information encoded in the genome and in messenger RNA. Translational readthrough always ensures that a certain proportion of lactate dehydrogenase will be brought to the peroxisome. The computational model developed here will be a valuable tool to identify other such proteins produced from genomes, including the human genome and those of other species.

DOI:http://dx.doi.org/10.7554/eLife.03640.002

JC virus antibody status in a pediatric multiple sclerosis cohort: prevalence, conversion rate and influence on disease severity

BACKGROUND

Because of the emergence of novel therapies for multiple sclerosis (MS) and the associated increased risk of progressive multifocal leukoencephalopathy, John Cunningham (JC) virus infection has become a focus of interest for neurologists. However, little is known about JC virus infection in pediatric MS to date.

OBJECTIVE

We aimed to analyze the prevalence of anti-JC virus antibodies, the conversion rate and the influence of the anti-JC virus antibody status on the clinical course in a large pediatric MS cohort.

METHODS

Anti-JC virus antibodies were analyzed in serum samples within six months of disease onset and during the course of the disease. Clinical data were extracted from a pediatric MS databank.

RESULTS

A total of 51.6% of 256 patients were found to be positive for anti-JC virus antibodies at onset of disease. No correlation between antibody status and clinical course was seen. Analyzing 693 follow-up serum samples revealed high titer stability, and an annual conversion rate of 4.37% was seen.

CONCLUSION

No evidence was found that seropositivity for anti-JC virus antibodies influences the clinical course. Surprisingly, seroprevalence for anti-JC virus antibodies was more than twice as high as anticipated in this age group, raising the question of whether the infection increases the risk of MS development.

MRI-based diagnostic biomarkers for early onset pediatric multiple sclerosis

Currently, it is unclear whether pediatric multiple sclerosis (PMS) is a pathoetiologically homogeneous disease phenotype due to clinical and epidemiological differences between early and late onset PMS (EOPMS and LOPMS). Consequently, the question was raised whether diagnostic guidelines need to be complemented by specific EOPMS markers. To search for such markers, we analyzed cerebral MRI images acquired with standard protocols using computer-based classification techniques. Specifically, we applied classification algorithms to gray (GM) and white matter (WM) tissue probability parameters of small brain regions derived from T2-weighted MRI images of EOPMS patients (onset <12 years), LOPMS patients (onset ≥12 years), and healthy controls (HC). This was done for PMS subgroups matched for disease duration and participant age independently. As expected, maximal diagnostic information for distinguishing PMS patients and HC was found in a periventricular WM area containing lesions (87.1% accuracy, p < 2.2 × 10⁻⁵). MRI-based biomarkers specific for EOPMS were identified in prefrontal cortex. Specifically, a coordinate in middle frontal gyrus contained maximal diagnostic information (77.3%, p = 1.8 × 10⁻⁴). Taken together, we were able to identify biomarkers reflecting pathognomonic processes specific for MS patients with very early onset. Especially GM involvement in the separation between PMS subgroups suggests that conventional MRI contains a richer set of diagnostically informative features than previously assumed.

•

EOPMS can be diagnosed accurately with computer-based classification and T2w-MRI.

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Separation of EOPMS and HC confirmed the pivotal role of WM lesions for diagnosis.

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Separation of EOPMS and LOPMS showed that GM variations are also informative.

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Thus, conventional MRI contains a richer set of biomarkers than assumed so far.

Structure of sulfamidase provides insight into the molecular pathology of mucopolysaccharidosis IIIA

Mucopolysaccharidosis type IIIA (Sanfilippo A syndrome), a fatal childhood-onset neurodegenerative disease with mild facial, visceral and skeletal abnormalities, is caused by an inherited deficiency of the enzyme N-sulfoglucosamine sulfohydrolase (SGSH; sulfamidase). More than 100 mutations in the SGSH gene have been found to reduce or eliminate its enzymatic activity. However, the molecular understanding of the effect of these mutations has been confined by a lack of structural data for this enzyme. Here, the crystal structure of glycosylated SGSH is presented at 2 Å resolution. Despite the low sequence identity between this unique N-sulfatase and the group of O-sulfatases, they share a similar overall fold and active-site architecture, including a catalytic formylglycine, a divalent metal-binding site and a sulfate-binding site. However, a highly conserved lysine in O-sulfatases is replaced in SGSH by an arginine (Arg282) that is positioned to bind the N-linked sulfate substrate. The structure also provides insight into the diverse effects of pathogenic mutations on SGSH function in mucopolysaccharidosis type IIIA and convincing evidence for the molecular consequences of many missense mutations. Further, the molecular characterization of SGSH mutations will lay the groundwork for the development of structure-based drug design for this devastating neurodegenerative disorder.

Peroxisomes are juxtaposed to strategic sites on mitochondria

Peroxisomes are ubiquitous and dynamic organelles that house many important pathways of cellular metabolism. In recent years it has been demonstrated that mitochondria are tightly connected with peroxisomes and are defective in several peroxisomal diseases. Indeed, these two organelles share metabolic routes as well as resident proteins and, at least in mammals, are connected via a vesicular transport pathway. However the exact extent of cross-talk between peroxisomes and mitochondria remains unclear. Here we used a combination of high throughput genetic manipulations of yeast libraries alongside high content screens to systematically unravel proteins that affect the transport of peroxisomal proteins and peroxisome biogenesis. Follow up work on the effector proteins that were identified revealed that peroxisomes are not randomly distributed in cells but are rather localized to specific mitochondrial subdomains such as mitochondria-ER junctions and sites of acetyl-CoA synthesis. Our approach highlights the intricate geography of the cell and suggests an additional layer of organization as a possible way to enable efficient metabolism. Our findings pave the way for further studying the machinery aligning mitochondria and peroxisomes, the role of the juxtaposition, as well as its regulation during various metabolic conditions. More broadly, the approaches used here can be easily applied to study any organelle of choice, facilitating the discovery of new aspects in cell biology.

The expanding clinical and genetic spectrum of ATP1A3-related disorders

OBJECTIVE

We aimed to delineate the clinical and genetic spectrum of ATP1A3-related disorders and recognition of a potential genotype-phenotype correlation.

METHODS

We identified 16 new patients with alternating hemiplegia of childhood (AHC) and 3 new patients with rapid-onset dystonia-parkinsonism (RDP) and included these as well as the clinical and molecular findings of all previously reported 164 patients with mutation-positive AHC and RDP in our analyses.

RESULTS

Major clinical characteristics shared in common by AHC and RDP comprise a strikingly asymmetric, predominantly dystonic movement disorder with rostrocaudal gradient of involvement and physical, emotional, or chemical stressors as triggers. The clinical courses include an early-onset polyphasic for AHC, a later-onset mono- or biphasic for RDP, as well as intermediate forms. Meta-analysis of the 8 novel and 38 published ATP1A3 mutations shows that the ones affecting transmembrane and functional domains tend to be associated with AHC as the more severe phenotype. The majority of mutations are located in exons 8, 14, 17, and 18.

CONCLUSION

AHC and RDP constitute clinical prototypes in a continuous phenotypic spectrum of ATP1A3-related disorders. Intermediate phenotypes combining criteria of both conditions are increasingly recognized. Efficient stepwise mutation analysis of the ATP1A3 gene may prioritize those exons where current state of knowledge indicates mutational clusters.

A Novel SLC6A8 Mutation in a Large Family with X-Linked Intellectual Disability: Clinical and Proton Magnetic Resonance Spectroscopy Data of Both Hemizygous Males and Heterozygous Females

X-linked creatine transport (CRTR) deficiency, caused by mutations in the SLC6A8 gene, leads to intellectual disability, speech delay, epilepsy, and autistic behavior in hemizygous males. Additional diagnostic features are depleted brain creatine levels and increased creatine/creatinine ratio (cr/crn) in urine. In heterozygous females the phenotype is highly variable and diagnostic hallmarks might be inconclusive. This survey aims to explore the intrafamilial variability of clinical and brain proton Magnetic Resonance Spectroscopy (MRS) findings in males and females with CRTR deficiency. X-chromosome exome sequencing identified a novel missense mutation in the SLC6A8 gene (p.G351R) in a large family with X-linked intellectual disability. Detailed clinical investigations including neuropsychological assessment, measurement of in vivo brain creatine concentrations using quantitative MRS, and analyses of creatine metabolites in urine were performed in five clinically affected family members including three heterozygous females and one hemizygous male confirming the diagnosis of CRTR deficiency. The severe phenotype of the hemizygous male was accompanied by most distinct aberrations of brain creatine concentrations (-83% in gray and -79% in white matter of age-matched normal controls) and urinary creatine/creatinine ratio. In contrast, the heterozygous females showed varying albeit generally milder phenotypes with less severe brain creatine (-50% to -33% in gray and -45% to none in white matter) and biochemical urine abnormalities. An intrafamilial correlation between female phenotype, brain creatine depletion, and urinary creatine abnormalities was observed. The combination of powerful new technologies like exome-next-generation sequencing with thorough systematic evaluation of patients will further expand the clinical spectrum of neurometabolic diseases.

Microduplication of 3p26.3 in nonsyndromic intellectual disability indicates an important role of CHL1 for normal cognitive function

Terminal deletions of chromosome 3p26.3 confined to the CHL1 gene have previously been described in children with intellectual disability and epilepsy. Here, we report for the first time, a 3p26.3 duplication including only the CHL1 gene in an intellectually disabled girl with epilepsy. The penetrance of both deletions and duplications in 3p26.3 is reduced because all chromosomal imbalances were inherited from healthy parents. Further studies are needed to specify the pathogenic mechanism of 3p26.3 imbalances and to estimate recurrence risks in genetic counseling. However, the description of both deletions and duplications of chromosome 3p26.3 in nonsyndromic intellectual disability suggests that CHL1 is a dosage-sensitive gene with an important role for normal cognitive development.

Methotrexate treatment of FraX fibroblasts results in FMR1 transcription but not in detectable FMR1 protein levels

Background

Fragile X syndrome is caused by the loss of FMRP expression due to methylation of the FMR1 promoter. Treatment of fragile X syndrome patients’ lymphoblastoid cells with 5-azadeoxycytidine results in demethylation of the promoter and reactivation of the gene. The aim of the study was to analyze if methotrexate, an agent which also reduces DNA methylation but with less toxicity than 5-azadeoxycytidine, has therapeutic potential in fragile X syndrome.

Methods

Fibroblasts of fragile X syndrome patients were treated with methotrexate in concentrations ranging from 1 to 4 μg/ml for up to 14 days. FMR1 and FMRP expression were analyzed by quantitative PCR and western blotting.

Results

FMR1 mRNA was detected and levels correlated positively with methotrexate concentrations and time of treatment, but western blotting did not show detectable FMRP levels.

Conclusions

We show that it is possible to reactivate FMR1 transcription in fibroblasts of fragile X syndrome patients by treatment with methotrexate. However, we were not able to show FMRP expression, possibly due to the reduced translation efficacy caused by the triplet repeat extension. Unless FMR1 reactivation is more effective in vivo our results indicate that methotrexate has no role in the treatment of fragile X syndrome.

T-cell homeostasis in pediatric multiple sclerosis: old cells in young patients

OBJECTIVE

To assess pediatric patients with multiple sclerosis (MS) for early signs of homeostatic and functional abnormalities in conventional (Tcon) and regulatory T cells (Treg).

METHODS

We studied the composition of the peripheral T-cell compartment and Treg function in a cross-sectional study with 30 pediatric MS (pMS) patients by multicolor flow cytometry and proliferation assays. Data were compared to those obtained from adult patients (n = 26) and age-matched control donors (n = 67).

RESULTS

Proportions of naive T cells were 10%-20% higher in children than in adults, reflecting the age-related decline. pMS patients, however, had clearly lower numbers of naive T cells, among them recent thymic emigrants (RTE), whereas percentages of memory T cells were increased. In the Treg compartment, reduced RTE numbers coincided with markedly dampened suppressive capacities of total Treg. These homeostatic changes in circulating T cells precisely paralleled the pattern seen in adult MS. As in adults, treatment with immunomodulatory drugs attenuated these alterations.

CONCLUSION

The homeostatic changes detected in the T-cell compartment in pMS are similar to those in adult-onset disease. With ratios between naive and memory T-cell subsets matching those of 20- to 30-years-older controls, signs of early thymic involution are already found in pMS, suggesting that an intrinsic compromise in thymic-dependent T-cell neogenesis might contribute to MS pathogenesis.

Pediatric onset multiple sclerosis: McDonald criteria 2010 and the contribution of spinal cord MRI

Background:

Diagnostic magnetic resonance imaging (MRI) criteria have not been sufficiently validated in pediatric multiple sclerosis (MS) despite differences in epidemiologic data and clinical disease courses between pediatric and adult MS.

Objective:

The objective of this paper is to evaluate the diagnostic applicability and validity of the revised McDonald diagnostic criteria 2010 in a large cohort of pediatric-onset MS patients (POMS) and compare them to previously recommended MRI-based classifications. Furthermore, we aimed to investigate the contribution of spinal cord lesions to the revised McDonald criteria 2010.

Methods:

A cohort of 85 patients with definite MS, age at onset 2.8–18 years, was analyzed in a retrospective multicenter study. Number and regional distribution of T2w and contrast-enhancing T1w lesions at initial and follow-up MRIs were main outcome measures.

Results:

In 62% of POMS the initial MRI within four weeks after symptom onset was sufficient to diagnose MS according to the revised McDonald criteria 2010. In a subcohort of patients with spinal MRI at first presentation, 10% reached the dissemination in space (DIS) and dissemination in time (DIT) criteria only by the inclusion of contrast-enhancing spinal lesions.

Conclusions:

The revised McDonald criteria 2010 facilitate the diagnosis of POMS already at first presentation. The addition of a spinal cord MRI was helpful only in selected cases.

West syndrome, microcephaly, grey matter heterotopia and hypoplasia of corpus callosum due to a novel ARFGEF2 mutation

West syndrome (WS) is an epileptic encephalopathy of childhood, defined by the presence of clustered spasms usually occurring before the age of 1 year, hypsarrhythmia on EEG that is notoriously difficult to define, and developmental arrest or regression. The incidence of WS is 1:3200 live births with an aetiology-dependent prognosis. Up to 80% of children with symptomatic WS suffer from mental retardation, and approximately 50% develop Lennox-Gastaut syndrome. Using homozygosity mapping followed by exome sequencing, we identified a ADP-ribosylation factor (ARF) guanine nucleotide-exchange factor two (brefeldin A-inhibited) (ARFGEF2) mutation in five related infants with WS. ARFGEF2 is involved in the activation of ARFs by accelerating replacement of bound guanosine diphosphate (GDP) with Guanosine triphosphate (GTP), and is involved in Golgi transport. A mutation in ARFGEF2 has been previously described only once, causing microcephaly and periventricular heterotopia. Here, we describe a novel ARFGEF2 mutation in five related patients presenting with WS, microcephaly, periventricular heterotopia and thin corpus callosum.

Functional analysis of PEX13 mutation in a Zellweger syndrome spectrum patient reveals novel homooligomerization of PEX13 and its role in human peroxisome biogenesis

In humans, the concerted action of at least 13 different peroxisomal PEX proteins is needed for proper peroxisome biogenesis. Mutations in any of these PEX genes can lead to lethal neurometabolic disorders of the Zellweger syndrome spectrum (ZSS). Previously, we identified the W313G mutation located within the SH3 domain of the peroxisomal protein, PEX13. As this tryptophan residue is highly conserved in almost all known SH3 proteins, we investigated the pathogenic mechanism of the W313G mutation and its role in PEX13 interactions and functions in peroxisome biogenesis. Here, we report for the first time that human PEX13 interacts with itself in peroxisomes in living cells. We demonstrate that the import of PTS1 (peroxisomal targeting signal 1) proteins is specifically disrupted when homooligomerization of PEX13 is interrupted. Live cell FRET microscopy in living cells as well as co-immunoprecipitation experiments reveal that the highly conserved W313 residue is important for self-association of PEX13 but is not required for interaction with PEX14, a well-established interaction partner at the peroxisomal membrane. Experiments with truncated constructs indicate that although the W313G mutation resides in the C-terminal SH3 domain, the N-terminal half is necessary for peroxisomal localization, which in turn appears to be crucial for homooligomerization. Furthermore, rescue of homooligomerization in the W313G mutant cells through complementation with truncation constructs restores import of peroxisomal matrix proteins. Taken together, the thorough analyses of a ZSS patient mutation unraveled the general cell biological function of PEX13 and its mechanism in the import of peroxisomal matrix PTS1 proteins.

Rapid degradation of an active formylglycine generating enzyme variant leads to a late infantile severe form of multiple sulfatase deficiency

Multiple sulfatase deficiency (MSD) is a rare inborn error of metabolism affecting posttranslational activation of sulfatases by the formylglycine generating enzyme (FGE). Due to mutations in the encoding SUMF1 gene, FGE's catalytic capacity is impaired resulting in reduced cellular sulfatase activities. Both, FGE protein stability and residual activity determine disease severity and have previously been correlated with the clinical MSD phenotype. Here, we report a patient with a late infantile severe course of disease. The patient is compound heterozygous for two so far undescribed SUMF1 mutations, c.156delC (p.C52fsX57) and c.390A>T (p.E130D). In patient fibroblasts, mRNA of the frameshift allele is undetectable. In contrast, the allele encoding FGE-E130D is expressed. FGE-E130D correctly localizes to the endoplasmic reticulum and has a very high residual molecular activity in vitro (55% of wildtype FGE); however, it is rapidly degraded. Thus, despite substantial residual enzyme activity, protein instability determines disease severity, which highlights that potential MSD treatment approaches should target protein folding and stabilization mechanisms.