Neurodegenerative Course Research Articles

Neurodegeneration in Niemann-Pick Type C Disease: An Updated Review on Pharmacological and Non-Pharmacological Approaches to Counteract Brain and Cognitive Impairment.

Niemann–Pick type C (NPC) disease is an autosomal recessive storage disorder, characterized by abnormal sequestration of unesterified cholesterol in the late endo-lysosomal system of cells. Progressive neurological deterioration and the onset of symptoms, such as ataxia, seizures, cognitive decline, and severe dementia, are pathognomonic features of the disease. In addition, different pathological similarities, including degeneration of hippocampal and cortical neurons, hyperphosphorylated tau, and neurofibrillary tangle formation, have been identified between NPC disease and other neurodegenerative pathologies. However, the underlying pathophysiological mechanisms are not yet well understood, and even a real cure to counteract neurodegeneration has not been identified. Therefore, the combination of current pharmacological therapies, represented by miglustat and cyclodextrin, and non-pharmacological approaches, such as physical exercise and appropriate diet, could represent a strategy to improve the quality of life of NPC patients. Based on this evidence, in our review we focused on the neurodegenerative aspects of NPC disease, summarizing the current knowledge on the molecular and biochemical mechanisms responsible for cognitive impairment, and suggesting physical exercise and nutritional treatments as additional non-pharmacologic approaches to reduce the progression and neurodegenerative course of NPC disease.

Niemann-Pick disease type A: a case report

BACKGROUND
 Niemann-Pick disease (NPD) types A result from the deficient activity of sphingomyelinase. NPD type A is characterized by early-onset, progressive neurodegenerative course; systemic disease manifestations, including massive hepatosplenomegaly, interstitial lung disease, and cherry-red macula; and death in early childhood. The objective: to enhance the recognition of health care providers about the potential undiagnosed NPD because nonspecific clinical manifestation
 
 CASE PRESENTATION 
 A 18-months-old boy was admitted to Dr. Kariadi Hospital with enlarged abdomen since seventh month old with failure to thrive. He also showed progressive loss of neurologic function, microcephaly with open major fontanelle, recurrent pulmonary and systemic infection. Physical examination revealed facial dysmorphic, milestone regression, under-nutrition, crackles in both lungs, hepatosplenomegaly with petechial in extremities and floppy infants. Laboratory investigations showed anemia (9.4 g/dL) and thrombocytopenia (73.000/mm3). The lactate dehydrogenase (482 U/L) and alkaline phosphatase (159, 03 IU/L) were higher than normal. Abdominal ultrasound revealed hepatomegaly with normal parenchyma and splenomegaly without nodule. Skeletal survey revealed Erlenmeyer flask deformity. Foam cell are detected in bone marrow puncture. Retcam examination showed cherry red spot at the macula. Bera revealed auditory neuropathy. The enzyme activity showed normal ?–Glucosidase (5.55 uM/hr) and chitotriosidase (105,8 nmol/ml) but low sphingomyelinases activity (0.30 uM/hr) which confirmed the diagnosis of NPD.
 DISCUSSION
 Niemann-Pick disease (NPD) types A result from the deficient activity of sphingomyelinase. NPD type A is characterized by early-onset, progressive neurodegenerative course; systemic disease manifestations, including massive hepatosplenomegaly, interstitial lung disease, and cherry-red macula; and death in early childhood. Type A is very rare and a severe infantile form with neurologic degeneration resulting in death usually by 3 years of age. No treatment available for type A and It’s a rare disease in Indonesia. 
 CONCLUSION 
 These investigations were able to diagnose this child as a NPD-Type A. Patient was closely monitored and symptomatic treatment was provided.

The Association Between Brain Reserve, Cognitive Reserve, and Neuropsychological and Functional Outcomes in Males With Chronic Moderate-to-Severe Traumatic Brain Injury.

Purpose Moderate-to-severe traumatic brain injury (TBI) leads to significant neural and cognitive impairment, affecting functional outcome. This study investigated the chronic effects of moderate-to-severe TBI on brain reserve (BR), cognitive reserve (CR), and neuropsychological and functional outcome. Method The group with TBI consisted of 41 male participants with a primary diagnosis of moderate-to-severe closed head injury (time since injury [TSI], M = 6.12 years, range: 1-23, SD = 5.99, Mdn = 4). TBI survivors were compared to 24 neurotypical male participants, matched on age and education. Magnetic resonance imaging T1 anatomical images were used to calculate gray and white matter and cerebrospinal fluid volume. BR was calculated using the ventricle-to-brain ratio. CR was assessed using two hold measures: the Peabody Picture Vocabulary Test and the Pseudowords task. Functional outcome was measured using the Glasgow Outcome Scale-Extended. Results Neuropsychological performance of TBI survivors was significantly lower than their neurotypical controls, as measured by theoretically driven composites of verbal and visual memory, executive functions, attention, and CR. They presented greater ventricle-to-brain ratio volume, compared to noninjured controls, with higher scores indicating lower BR levels. Both BR and TSI were significantly associated with CR. Also, a median-split analysis revealed a TSI effect on CR. Significant associations were evident between the Glasgow Outcome Scale-Extended and the BR and CR measures. Conclusions Lingering neuropsychological deficits in chronic TBI support the role of BR and CR in functional outcome. Furthermore, TSI interferes with CR supporting the notion that TBI sets off a chronic neurodegenerative and progressive course that interferes with semantic knowledge. Supplemental Material https://doi.org/10.23641/asha.14049923.

Long-term disease course of two patients with multiple sulfatase deficiency differs from metachromatic leukodystrophy in a broad cohort.

Multiple sulfatase deficiency (MSD) is a lysosomal storage disease caused by a deficiency of formylglycine‐generating enzyme due to SUMF1 defects. MSD may be misdiagnosed as metachromatic leukodystrophy (MLD), as neurological and neuroimaging findings are similar, and arylsulfatase A (ARSA) deficiency and enhanced urinary sulfatide excretion may also occur. While ARSA deficiency seems a cause for neurological symptoms and later neurodegenerative disease course, deficiency of other sulfatases results in clinical features such as dysmorphism, dysostosis, or ichthyosis. We report on a girl and a boy of the same origin presenting with severe ARSA deficiency and neurological and neuroimaging features compatible with MLD. However, exome sequencing revealed not yet described homozygosity of the missense variant c.529G > C, p.Ala177Pro in SUMF1. We asked whether dynamics of disease course differs between MSD and MLD. Comparison to a cohort of 59 MLD patients revealed different disease course concerning onset and disease progression in both MSD patients. The MSD patients showed first gross motor symptoms earlier than most patients with juvenile MLD (<10th percentile of Gross‐Motor‐Function in MLD [GMFC‐MLD] 1). However, subsequent motor decline was more protracted (75th and 90th percentile of GMFC‐MLD 2 (loss of independent walking) and 75th percentile of GMFC‐MLD 5 (loss of any locomotion)). Language decline started clearly after 50th percentile of juvenile MLD and progressed rapidly. Thus, dynamics of disease course may be a further clue for the characterization of MSD. These data may contribute to knowledge of natural course of ultra‐rare MSD and be relevant for counseling and therapy.

A novel acceptor stem variant in mitochondrial tRNATyr impairs mitochondrial translation and is associated with a severe phenotype

Genetic defects in mitochondrial DNA encoded tRNA genes impair mitochondrial translation with resultant defects in the mitochondrial respiratory chain and oxidative phosphorylation system. The phenotypic spectrum of disease seen in mitochondrial tRNA defects is variable and proving pathogenicity of new variants is challenging. Only three pathogenic variants have been described previously in the mitochondrial tRNATyr gene MT-TY, with the reported phenotypes consisting largely of adult onset myopathy and ptosis. We report a patient with a novel MT-TY acceptor stem variant m.5889A>G at high heteroplasmy in muscle, low in blood, and absent in the mother's blood. The phenotype consisted of a childhood-onset severe multi-system disorder characterized by a neurodegenerative course including ataxia and seizures, failure-to-thrive, combined myopathy and neuropathy, and hearing and vision loss. Brain imaging showed progressive atrophy and basal ganglia calcifications. Mitochondrial biomarkers lactate and GDF15 were increased. Functional studies showed a deficient activity of the respiratory chain enzyme complexes containing mtDNA-encoded subunits I, III and IV. There were decreased steady state levels of these mitochondrial complex proteins, and presence of incompletely assembled complex V forms in muscle. These changes are typical of a mitochondrial translational defect. These data support the pathogenicity of this novel variant. Careful review of variants in MT-TY additionally identified two other pathogenic variants, one likely pathogenic variant, nine variants of unknown significance, five likely benign and four benign variants.

Pre-clinical Gene Therapy with AAV9/AGA in Aspartylglucosaminuria Mice Provides Evidence for Clinical Translation

Aspartylglucosaminuria (AGU) is an autosomal recessive lysosomal storage disease caused by loss of the enzyme aspartylglucosaminidase (AGA), resulting in AGA substrate accumulation. AGU patients have a slow but progressive neurodegenerative disease course, for which there is no approved disease-modifying treatment. In this study, AAV9/AGA was administered to Aga−/− mice intravenously (i.v.) or intrathecally (i.t.), at a range of doses, either before or after disease pathology begins. At either treatment age, AAV9/AGA administration led to (1) dose dependently increased and sustained AGA activity in body fluids and tissues; (2) rapid, sustained, and dose-dependent elimination of AGA substrate in body fluids; (3) significantly rescued locomotor activity; (4) dose-dependent preservation of Purkinje neurons in the cerebellum; and (5) significantly reduced gliosis in the brain. Treated mice had no abnormal neurological phenotype and maintained body weight throughout the whole experiment to 18 months old. In summary, these results demonstrate that treatment of Aga−/− mice with AAV9/AGA is effective and safe, providing strong evidence that AAV9/AGA gene therapy should be considered for human translation. Further, we provide a direct comparison of the efficacy of an i.v. versus i.t. approach using AAV9, which should greatly inform the development of similar treatments for other related lysosomal storage diseases.

P.350 Preliminary data on the association of HSP70 and major depression obtained on a transdiagnostic study

Genetic defects in mitochondrial DNA encoded tRNA genes impair mitochondrial translation with resultant defects in the mitochondrial respiratory chain and oxidative phosphorylation system. The phenotypic spectrum of disease seen in mitochondrial tRNA defects is variable and proving pathogenicity of new variants is challenging. Only three pathogenic variants have been described previously in the mitochondrial tRNATyr gene MT-TY, with the reported phenotypes consisting largely of adult onset myopathy and ptosis. We report a patient with a novel MT-TY acceptor stem variant m.5889A>G at high heteroplasmy in muscle, low in blood, and absent in the mother's blood. The phenotype consisted of a childhood-onset severe multi-system disorder characterized by a neurodegenerative course including ataxia and seizures, failure-to-thrive, combined myopathy and neuropathy, and hearing and vision loss. Brain imaging showed progressive atrophy and basal ganglia calcifications. Mitochondrial biomarkers lactate and GDF15 were increased. Functional studies showed a deficient activity of the respiratory chain enzyme complexes containing mtDNA-encoded subunits I, III and IV. There were decreased steady state levels of these mitochondrial complex proteins, and presence of incompletely assembled complex V forms in muscle. These changes are typical of a mitochondrial translational defect. These data support the pathogenicity of this novel variant. Careful review of variants in MT-TY additionally identified two other pathogenic variants, one likely pathogenic variant, nine variants of unknown significance, five likely benign and four benign variants.

Trans-synaptic and retrograde axonal spread of Lewy pathology following pre-formed fibril injection in an in vivo A53T alpha-synuclein mouse model of synucleinopathy

It is necessary to develop an understanding of the specific mechanisms involved in alpha-synuclein aggregation and propagation to develop disease modifying therapies for age-related synucleinopathies, including Parkinson’s disease and Dementia with Lewy Bodies. To adequately address this question, we developed a new transgenic mouse model of synucleinopathy that expresses human A53T SynGFP under control of the mouse prion protein promoter. Our characterization of this mouse line demonstrates that it exhibits several distinct advantages over other, currently available, mouse models. This new model allows rigorous study of the initial location of Lewy pathology formation and propagation in the living brain, and strongly suggests that aggregation begins in axonal structures with retrograde propagation to the cell body. This model also shows expeditious development of alpha-synuclein pathology following induction with small, in vitro-generated alpha-synuclein pre-formed fibrils (PFFs), as well as accelerated cell death of inclusion-bearing cells. Using this model, we found that aggregated alpha-synuclein somatic inclusions developed first in neurons, but later showed a second wave of inclusion formation in astrocytes. Interestingly, astrocytes appear to survive much longer after inclusion formation than their neuronal counterparts. This model also allowed careful study of peripheral-to-central spread of Lewy pathology after PFF injection into the hind limb musculature. Our results clearly show evidence of progressive, retrograde trans-synaptic spread of Lewy pathology through known neuroanatomically connected pathways in the motor system. As such, we have developed a promising tool to understand the biology of neurodegeneration associated with alpha-synuclein aggregation and to discover new treatments capable of altering the neurodegenerative disease course of synucleinopathies.

Hospitalization Rates and Comorbidities in Patients with Progressive Supranuclear Palsy in Germany from 2010 to 2017.

Progressive supranuclear palsy (PSP) belongs to the disease spectrum of Parkinsonian syndromes. Due to the chronic and progressive neurodegenerative course of the disease, PSP patients often have to be hospitalized to undergo diagnostic and therapeutic measures. The dynamics and characteristics of PSP inpatient treatment in Germany have not been investigated thus far. The current study analyzed trends of inpatient treatment in Germany for the years 2010–2017 based on the German DRG statistics (“diagnostic-related groups”) in the category G23.- (other degenerative diseases of the basal ganglia) and with special focus on PSP (G23.1). Inpatient case numbers of the G23.- category comprised a total of 21,196 patients from 2010–2017, whereas the PSP subcategory (G23.1) amounted to 10,663 cases. In the analyzed time period, PSP patient numbers constantly increased from 963 in 2010 to 1780 in 2017 with yearly growth rates of up to 20%. Similar trends were observed for other Parkinsonian syndromes such as multiple system atrophy (MSA). Differentiating PSP inpatients by gender demonstrated a higher proportion of males (55–60%) in comparison to female patients for the entire observation period. The average age of hospitalized PSP patients over these years was between 72.3 and 73.4 years without relevant differences for gender. The most common comorbidities consisted of cardiovascular, neurological, muscular and urological disorders. In summary, the analysis demonstrates that PSP patients are increasingly hospitalized in Germany and the current concepts of stationary care have to differentiate standard practices for Parkinson’s disease (PD) to also address the needs of patients with PSP and other Parkinsonian syndromes.

Protein Aggregation and Dysfunction of Autophagy-Lysosomal Pathway: A Vicious Cycle in Lysosomal Storage Diseases.

Many neurodegenerative conditions are characterized by the deposition of protein aggregates (mainly amyloid-like) in the central nervous system (CNS). In post-mitotic CNS cells protein aggregation causes cytotoxicity by interfering with various cellular functions. Mutations in different genes may directly cause protein aggregation. However, genetic factors together with aging may contribute to the onset of protein aggregation also by affecting cellular degradative functions, in particular the autophagy-lysosomal pathway (ALP). Increasing body of evidence show that ALP dysfunction and protein aggregation are functionally interconnected and induce each other during neurodegenerative processes. We will summarize the findings supporting these concepts by focusing on lysosomal storage diseases (LSDs), a class of metabolic inherited conditions characterized by global lysosomal dysfunction and often associated to a severe neurodegenerative course. We propose a model by which the inherited lysosomal defects initiate aggregate-prone protein deposition, which, in turns, worsen ALP degradation function, thus generating a vicious cycle, which boost neurodegenerative cascades.

Multiple Sclerosis: Clinical Updates in Women's Health Care Primary and Preventive Care Review.

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disease of the central nervous system. The disease affects more women than men and often is diagnosed during a woman's childbearing years. Typical clinical presentations of the disease are extensive and variable, with symptoms that include dysregulated mood, fatigue, vision problems, weakness, tremor, imbalance, abnormal sensations, bladder dysfunction, and heat sensitivity. If a woman aged 15-50 years experiences these neurologic symptoms in isolation or combination, and the symptoms are not explained by other underlying medical conditions, MS should be suspected. Multiple sclerosis can be divided into four clinical subtypes: 1) relapsing-remitting MS, 2) secondary progressive MS, 3) primary progressive MS, and 4) clinically isolated syndrome. Relapsing-remitting MS at the time of onset is the most common form and accounts for approximately 80% of all cases of MS. Relapsing-remitting MS does not affect life expectancy. However, because of the neurodegenerative and progressive course of the disease, patients accumulate physical and cognitive disabilities over time that result in impaired ability to work, increased financial burden, and slightly increased mortality. A variety of possible risk and prognostic indicators have been identified that may predict the course of disease, particularly the extent of relapses and disability. Multiple sclerosis currently is incurable, but many disease-modifying therapies are available that can reduce the frequency of clinically evident exacerbations and accumulation of disease burden as defined by the number of lesions identified on magnetic resonance imaging. The choice of disease-modifying therapies, contraception use, and treatment of symptoms should be individualized based on age at onset and disease activity and, during pregnancy, the gestational age. Proactive management of MS across the woman's life cycle reduces morbidity, improves maternal and fetal health during pregnancy and the postpartum period, and increases quality-of life-measures for patients and their families.

A homozygous canonical splice acceptor site mutation in PRUNE1 is responsible for a rare childhood neurodegenerative disease in Manitoba Cree families.

Autosomal recessive PRUNE1 mutations are reported to cause a severe neurodevelopmental disorder with microcephaly, hypotonia, and brain malformations. We describe clinical and neuropathological features in a cohort of nine individuals of Cree descent who, because of a founder effect, are homozygous for the same PRUNE1 mutation. They follow the course of a combined neuromuscular and neurodegenerative disease, rather than a pure failure of normal development. This cohort presented in infancy with features of lower motor neuron disease, such as hypotonia, contractures, tongue fasciculations, and feeding difficulties in the absence of congenital brain anomalies and microcephaly. A neurodegenerative course followed with onset of seizures, spasticity, and respiratory insufficiency. Muscle biopsies showed denervation/reinnervation features, nonspecific atrophy and end-stage atrophy. Autopsy findings in two patients are also described, suggesting length dependent central motor axon degeneration, peripheral motor axon degeneration, possible spinal motor neuron degeneration, and accumulation of beta amyloid precursor protein inclusions in select brainstem nuclei. Exome sequencing and homozygosity mapping identified a homozygous PRUNE1 mutation in a canonical splice site, which produces two abnormal PRUNE1 mRNA products. Based on our studies and the histopathology and phenotypic data, we provide further evidence that this disorder leads to a neurodegenerative disease affecting both the peripheral and central nervous systems and suggest that the pathogenic c.521-2A>G mutation could lead to an altered effect on tubulin dynamics.

Lysosomal storage diseases.

Lysosomal storage diseases (LSDs) are a group of over 70 diseases that are characterized by lysosomal dysfunction, most of which are inherited as autosomal recessive traits. These disorders are individually rare but collectively affect 1 in 5,000 live births. LSDs typically present in infancy and childhood, although adult-onset forms also occur. Most LSDs have a progressive neurodegenerative clinical course, although symptoms in other organ systems are frequent. LSD-associated genes encode different lysosomal proteins, including lysosomal enzymes and lysosomal membrane proteins. The lysosome is the key cellular hub for macromolecule catabolism, recycling and signalling, and defects that impair any of these functions cause the accumulation of undigested or partially digested macromolecules in lysosomes (that is, 'storage') or impair the transport of molecules, which can result in cellular damage. Consequently, the cellular pathogenesis of these diseases is complex and is currently incompletely understood. Several LSDs can be treated with approved, disease-specific therapies that are mostly based on enzyme replacement. However, small-molecule therapies, including substrate reduction and chaperone therapies, have also been developed and are approved for some LSDs, whereas gene therapy and genome editing are at advanced preclinical stages and, for a few disorders, have already progressed to the clinic.

Annual severity increment score as a tool for stratifying patients with Niemann-Pick disease type C and for recruitment to clinical trials

BackgroundNiemann-Pick disease type C (NPC) is a lysosomal storage disease with a heterogeneous neurodegenerative clinical course. Multiple therapies are in clinical trials and inclusion criteria are currently mainly based on age and neurological signs, not taking into consideration differential individual rates of disease progression.ResultsIn this study, we have evaluated a simple metric, denoted annual severity increment score (ASIS), that measures rate of disease progression and could easily be used in clinical practice. We show that ASIS is stable over several years and can be used to stratify patients for clinical trials. It achieves greater homogeneity of the study cohort relative to age-based inclusion and provides an evidence-based approach for establishing inclusion/exclusion criteria. In addition, we show that ASIS has prognostic value and demonstrate that treatment with an experimental therapy - acetyl-DL-leucine - is associated with a reduction in ASIS scores.ConclusionASIS has the potential to be a useful metric for clinical monitoring, trial recruitment, for prognosis and measuring response to therapy.

Mercury Involvement in Neuronal Damage and in Neurodegenerative Diseases.

Neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis are characterized by a chronic and selective process of neuronal cell death. Although the causes of neurodegenerative diseases remain still unknown, it is now a well-established idea that more factors, such as genetic, endogenous, and environmental, are involved. Among environmental causes, the accumulation of mercury, a heavy metal considered a toxic agent, was largely studied as a probable factor involved in neurodegenerative disease course. Mercury exists in three main forms: elemental mercury, inorganic mercury, and organic mercury (methylmercury and ethylmercury). Sources of elemental mercury can be natural (volcanic emission) or anthropogenic (coal-fired electric utilities, waste combustion, hazardous-waste incinerators, and gold extraction). Moreover, mercury is still used as an antiseptic, as a medical preservative, and as a fungicide. Dental amalgam can emit mercury vapor. Mercury vapor, being highly volatile and lipid soluble, can cross the blood-brain barrier and the lipid cell membranes and can be accumulated into the cells in its inorganic forms. Also, methylmercury can pass through blood-brain and placental barriers, causing serious damage in the central nervous system. This review describes the toxic effects of mercury in cell cultures, in animal models, and in patients with neurodegenerative diseases. In vitro experiments showed that mercury exposure was principally involved in oxidative stress and apoptotic processes. Moreover, motor and cognitive impairment and neural loss have been confirmed in various studies performed in animal models. Finally, observational studies on patients with neurodegenerative diseases showed discordant data about a possible mercury involvement.

Homozygous boricua TBCK mutation causes neurodegeneration and aberrant autophagy.

Autosomal-recessive mutations in TBCK cause intellectual disability of variable severity. Although the physiological function of TBCK remains unclear, loss-of-function mutations are associated with inhibition of mechanistic target of rapamycin complex 1 (mTORC1) signaling. Given that mTORC1 signaling is known to regulate autophagy, we hypothesized that TBCK-encephalopathy patients with a neurodegenerative course have defects in autophagic-lysosomal dysfunction. Children (n = 8) of Puerto Rican (Boricua) descent affected with homozygous TBCK p.R126X mutations underwent extensive neurological phenotyping and neurophysiological studies. We quantified autophagosome content in TBCK-/- patient-derived fibroblasts by immunostaining and assayed autophagic markers by western assay. Free sialylated oligosaccharide profiles were assayed in patient's urine and fibroblasts. The neurological phenotype of children with TBCK p.R126X mutations, which we call TBCK-encephaloneuronopathy (TBCKE), include congenital hypotonia, progressive motor neuronopathy, leukoencephalopathy, and epilepsy. Systemic features include coarse facies, dyslipidemia, and osteoporosis. TBCK-/- fibroblasts in vitro exhibit increased numbers of LC3+ autophagosomes and increased autophagic flux by immunoblots. Free oligosaccharide profiles in fibroblasts and urine of TBCKE patients differ from control fibroblasts and are ameliorated by treatment with the mTORC1 activator leucine. TBCKE is a clinically distinguishable syndrome with progressive central and peripheral nervous system dysfunction, consistently observed in patients with the p.R126X mutation. We provide evidence that inappropriate autophagy in the absence of cellular stressors may play a role in this disorder, and that mTORC1 activation may ameliorate the autophagic-lysosomal system dysfunction. Free oligosaccharide profiles could serve as a novel biomarker for this disorder as well as a tool to evaluate potential therapeutic interventions. Ann Neurol 2018;83:153-165.

Delineating SPTAN1 associated phenotypes: from isolated epilepsy to encephalopathy with progressive brain atrophy.

De novo in-frame deletions and duplications in the SPTAN1 gene, encoding the non-erythrocyte αII spectrin, have been associated with severe West syndrome with hypomyelination and pontocerebellar atrophy. We aimed at comprehensively delineating the phenotypic spectrum associated with SPTAN1 mutations. Using different molecular genetic techniques, we identified 20 patients with a pathogenic or likely pathogenic SPTAN1 variant and reviewed their clinical, genetic and imaging data. SPTAN1 de novo alterations included seven unique missense variants and nine in-frame deletions/duplications of which 12 were novel. The recurrent three-amino acid duplication p.(Asp2303_Leu2305dup) occurred in five patients. Our patient cohort exhibited a broad spectrum of neurodevelopmental phenotypes, comprising six patients with mild to moderate intellectual disability, with or without epilepsy and behavioural disorders, and 14 patients with infantile epileptic encephalopathy, of which 13 had severe neurodevelopmental impairment and four died in early childhood. Imaging studies suggested that the severity of neurological impairment and epilepsy correlates with that of structural abnormalities as well as the mutation type and location. Out of seven patients harbouring mutations outside the α/β spectrin heterodimerization domain, four had normal brain imaging and three exhibited moderately progressive brain and/or cerebellar atrophy. Twelve of 13 patients with mutations located within the spectrin heterodimer contact site exhibited severe and progressive brain, brainstem and cerebellar atrophy, with hypomyelination in most. We used fibroblasts from five patients to study spectrin aggregate formation by Triton-X extraction and immunocytochemistry followed by fluorescence microscopy. αII/βII aggregates and αII spectrin in the insoluble protein fraction were observed in fibroblasts derived from patients with the mutations p.(Glu2207del), p.(Asp2303_Leu2305dup) and p.(Arg2308_Met2309dup), all falling in the nucleation site of the α/β spectrin heterodimer region. Molecular modelling of the seven SPTAN1 amino acid changes provided preliminary evidence for structural alterations of the A-, B- and/or C-helices within each of the mutated spectrin repeats. We conclude that SPTAN1-related disorders comprise a wide spectrum of neurodevelopmental phenotypes ranging from mild to severe and progressive. Spectrin aggregate formation in fibroblasts with mutations in the α/β heterodimerization domain seems to be associated with a severe neurodegenerative course and suggests that the amino acid stretch from Asp2303 to Met2309 in the α20 repeat is important for α/β spectrin heterodimer formation and/or αII spectrin function.

CAD mutations and uridine-responsive epileptic encephalopathy.

Unexplained global developmental delay and epilepsy in childhood pose a major socioeconomic burden. Progress in defining the molecular bases does not often translate into effective treatment. Notable exceptions include certain inborn errors of metabolism amenable to dietary intervention. CAD encodes a multifunctional enzyme involved in de novo pyrimidine biosynthesis. Alternatively, pyrimidines can be recycled from uridine. Exome sequencing in three families identified biallelic CAD mutations in four children with global developmental delay, epileptic encephalopathy, and anaemia with anisopoikilocytosis. Two died aged 4 and 5 years after a neurodegenerative disease course. Supplementation of the two surviving children with oral uridine led to immediate cessation of seizures in both. A 4-year-old female, previously in a minimally conscious state, began to communicate and walk with assistance after 9 weeks of treatment. A 3-year-old female likewise showed developmental progress. Blood smears normalized and anaemia resolved. We establish CAD as a gene confidently implicated in this neurometabolic disorder, characterized by co-occurrence of global developmental delay, dyserythropoietic anaemia and seizures. While the natural disease course can be lethal in early childhood, our findings support the efficacy of uridine supplementation, rendering CAD deficiency a treatable neurometabolic disorder and therefore a potential condition for future (genetic) newborn screening.

Lysosomal dysfunction disrupts presynaptic maintenance and restoration of presynaptic function prevents neurodegeneration in lysosomal storage diseases

Lysosomal storage disorders (LSDs) are inherited diseases characterized by lysosomal dysfunction and often showing a neurodegenerative course. There is no cure to treat the central nervous system in LSDs. Moreover, the mechanisms driving neuronal degeneration in these pathological conditions remain largely unknown. By studying mouse models of LSDs, we found that neurodegeneration develops progressively with profound alterations in presynaptic structure and function. In these models, impaired lysosomal activity causes massive perikaryal accumulation of insoluble α‐synuclein and increased proteasomal degradation of cysteine string protein α (CSPα). As a result, the availability of both α‐synuclein and CSPα at nerve terminals strongly decreases, thus inhibiting soluble NSF attachment receptor (SNARE) complex assembly and synaptic vesicle recycling. Aberrant presynaptic SNARE phenotype is recapitulated in mice with genetic ablation of one allele of both CSPα and α‐synuclein. The overexpression of CSPα in the brain of a mouse model of mucopolysaccharidosis type IIIA, a severe form of LSD, efficiently re‐established SNARE complex assembly, thereby ameliorating presynaptic function, attenuating neurodegenerative signs, and prolonging survival. Our data show that neurodegenerative processes associated with lysosomal dysfunction may be presynaptically initiated by a concomitant reduction in α‐synuclein and CSPα levels at nerve terminals. They also demonstrate that neurodegeneration in LSDs can be slowed down by re‐establishing presynaptic functions, thus identifying synapse maintenance as a novel potentially druggable target for brain treatment in LSDs.

Cell-based high-throughput screening identifies galactocerebrosidase enhancers as potential small-molecule therapies for Krabbe's disease.

Krabbe's disease, also known as globoid cell leukodystrophy (GLD), is a lysosomal storage disease caused by the deficiency of the lysosomal enzyme β-galactocerebrosidase (GALC), resulting in severe neurological manifestations related to demyelination secondary to elevated galactosylsphingosine (psychosine) with its subsequent cytotoxicity. The only available treatment is hematopoietic stem cell transplantation, which delays disease onset but does not prevent long-term neurological manifestations. This article describes the identification of small molecules that enhance mutant GALC activity, identified by quantitative cell-based high-throughput screening (qHTS). Using a specific neurologically relevant murine cell line (145M-Twi) modified to express common human hGALC-G270D mutant, we were able to detect GALC activity in a 1,536-well microplate format. The qHTS of approximately 46,000 compounds identified three small molecules that showed significant enhancements of residual mutant GALC activity in primary cell lines from GLD patients. These compounds were shown to increase the levels of GALC-G270D mutant in the lysosomal compartment. In kinetic assessments, these small molecules failed to disturb the GALC kinetic profile under acidic conditions, which is highly desirable for folding-assisting molecules operating in the endoplasmic reticulum and not affecting GALC catalytic properties in the lysosomal compartment. In addition, these small molecules rescued the decreased GALC activity at neutral pH and partially stabilized GALC under heat-denaturating conditions. These drug-like compounds can be used as the starting point to develop novel small-molecule agents to treat the progressive neurodegenerative course of GLD. © 2016 Wiley Periodicals, Inc.