A Novel De novo Heterozygous Mutation in the SON Gene Associated with Septo-optic Dysplasia: A New Phenotype

Septo-optic dysplasia (SOD) syndrome is a rare congenital disorder characterized by a classic triad of optic nerve/chiasm hypoplasia, agenesis of septum pellucidum and corpus callosum, and hypoplasia of the hypothalamic-pituitary axis.Herein, we report the clinical case of 2-year-old boy presenting with psychomotor delay, nystagmus, congenital hypothyroidism, and a clinically relevant growth delay. The neuroradiological examination showed partial segmental agenesis of the corpus callosum, agenesis of the septum pellucidum, optic nerve hypoplasia, and a small pituitary gland with a small median pituitary stalk. A whole-exome sequencing analysis detected a novel heterozygous de novo variant c.1069_1070delAG in SON, predicted as likely pathogenic.To date, SON pathogenic variants have been described as responsible for Zhu-Tokita-Takenouchi-Kim (ZTTK) syndrome, a multisystemic neurodevelopmental disorder mainly characterized by intellectual disability, facial dysmorphisms, visual abnormalities, brain malformations, feeding difficulties, and growth delay. The herein described case is the first recognized clinic-radiological occurrence of SOD syndrome with hypothalamic-pituitary dysfunction in a patient carrying a SON gene variant, considered responsible of ZTTK syndrome, suggesting a possible relationship between SOD and SON gene alterations, never described so far, making the search for SON gene mutations advisable in patients with SOD.

A case of a childhood onset developmental encephalopathy with a novel de novo truncating variant in the Membrane Protein Palmitoylated 5 (MPP5) gene

BACKGROUND

Membrane Protein Palmitoylated 5 (MPP5) is a highly conserved apical complex protein, essential for cell polarity. Defects in neuronal cell polarity are associated with neurologic disorders. Only three patients with heterozygous MPP5 de novo variants have been reported so far, with global developmental delay, behavioral changes and in only one case epileptic seizures.

OBJECTIVE

To describe a new patient with a novel truncating de novo mutation in MPP5 and to characterize in detail the epileptic phenotype and electroencephalographic features of the encephalopathy.

METHODS

We identified a novel truncating de novo mutation in MPP5 in a 44 year old patient by exome sequencing (p.Ser498Phefs*15). We retrospectively analyzed his clinical and instrumental data along a thirty-year follow up.

RESULT

Our patient presents with generalized tonic-clonic seizures, myoclonic and clonic seizures, non-epileptic myoclonus, tremor, severe intellectual disability, mild face dysmorphic traits, and psychosis.

DISCUSSION AND CONCLUSION

We present a case of a childhood onset developmental encephalopathy with a likely-pathogenic variant in the MPP5 gene.. This represents the first complete description of the epileptic syndrome associated with the MPP5 gene.

Olanzapine, risperidone and ziprasidone differently affect lysosomal function and autophagy, reflecting their different metabolic risk in patients

The metabolic effects induced by antipsychotics in vitro depend on their action on the trafficking and biosynthesis of sterols and lipids. Previous research showed that antipsychotics with different adverse effects in patients cause similar alterations in vitro, suggesting the low clinical usefulness of cellular studies. Moreover, the inhibition of peripheral AMPK was suggested as potential aetiopathogenic mechanisms of olanzapine, and different effects on autophagy were reported for several antipsychotics. We thus assessed, in clinically-relevant culture conditions, the aetiopathogenic mechanisms of olanzapine, risperidone and ziprasidone, antipsychotics with respectively high, medium, low metabolic risk in patients, finding relevant differences among them. We highlighted that: olanzapine impairs lysosomal function affecting autophagy and autophagosome clearance, and increasing intracellular lipids and sterols; ziprasidone activates AMPK increasing the autophagic flux and reducing intracellular lipids; risperidone increases lipid accumulation, while it does not affect lysosomal function. These in vitro differences align with their different impact on patients. We also provided evidence that metformin add-on improved autophagy in olanzapine-treated cells and reduced lipid accumulation induced by both risperidone and olanzapine in an AMPK-dependent way; metformin also increased the production of bile acids to eliminate cholesterol accumulations caused by olanzapine. These results have different clinical implications. We demonstrated that antipsychotics with different metabolic impacts on patients actually have different mechanisms of action, thus supporting the possibility of a personalised antipsychotic treatment. Moreover, we found that metformin can fully revert the phenotype caused by risperidone but not the one caused by olanzapine, that still activates SREBP2.

Extreme phenotypic heterogeneity in non-expansion spinocerebellar ataxias

Although the best-known spinocerebellar ataxias (SCAs) are triplet repeat diseases, many SCAs are not caused by repeat expansions. The rarity of individual non-expansion SCAs, however, has made it difficult to discern genotype-phenotype correlations. We therefore screened individuals who had been found to bear variants in a non-expansion SCA-associated gene through genetic testing, and after we eliminated genetic groups that had fewer than 30 subjects, there were 756 subjects bearing single-nucleotide variants or deletions in one of seven genes: CACNA1A (239 subjects), PRKCG (175), AFG3L2 (101), ITPR1 (91), STUB1 (77), SPTBN2 (39), or KCNC3 (34). We compared age at onset, disease features, and progression by gene and variant. There were no features that reliably distinguished one of these SCAs from another, and several genes-CACNA1A, ITPR1, SPTBN2, and KCNC3-were associated with both adult-onset and infantile-onset forms of disease, which also differed in presentation. Nevertheless, progression was overall very slow, and STUB1-associated disease was the fastest. Several variants in CACNA1A showed particularly wide ranges in age at onset: one variant produced anything from infantile developmental delay to ataxia onset at 64 years of age within the same family. For CACNA1A, ITPR1, and SPTBN2, the type of variant and charge change on the protein greatly affected the phenotype, defying pathogenicity prediction algorithms. Even with next-generation sequencing, accurate diagnosis requires dialogue between the clinician and the geneticist.

Case report: A novel FARS2 deletion and a missense variant in a child with complicated, rapidly progressive spastic paraplegia

Defects in FARS2 are associated with either epileptic phenotypes or a spastic paraplegia subtype known as SPG77. Here, we describe an 8-year-old patient with severe and complicated spastic paraplegia, carrying a missense variant (p.Pro361Leu) and a novel intragenic deletion in FARS2. Of note, the disease is unexpectedly progressing rapidly and in a biphasic way differently from the previously reported cases. Our study provides the first detailed molecular characterization of a FARS2 deletion and its underlying molecular mechanism, and demonstrates the need for combining different tools to improve the diagnostic rate.

Rescue of lysosomal function as therapeutic strategy for SPG15 hereditary spastic paraplegia

SPG15 is a hereditary spastic paraplegia subtype caused by mutations in Spastizin, a protein encoded by the ZFYVE26 gene. Spastizin is involved in autophagosome maturation and autophagic lysosome reformation and SPG15-related mutations lead to autophagic lysosome reformation defects with lysosome enlargement, free lysosome depletion and autophagosome accumulation. Symptomatic and rehabilitative treatments are the only therapy currently available for patients. Here, we targeted autophagy and lysosomes in SPG15 patient-derived cells by using a library of autophagy-modulating compounds. We identified a rose of compounds affecting intracellular calcium levels, the calcium-calpain pathway or lysosomal functions, which reduced autophagosome accumulation. The six most effective compounds were tested in vivo in a new SPG15 loss of function Drosophila model that mimicked the reported SPG15 phenotype, with autophagosome accumulation, enlarged lysosomes, reduced free lysosomes, autophagic lysosome reformation defects and locomotor deficit. These compounds, namely verapamil, Bay K8644, 2',5'-dideoxyadenosine, trehalose, Small-Molecule Enhancer of Rapamycin 28 and trifluoperazine, improved lysosome biogenesis and function in vivo, demonstrating that lysosomes are a key pharmacological target to rescue SPG15 phenotype. Among the others, the Small-Molecule Enhancer of Rapamycin 28 was the most effective, rescuing both autophagic lysosome reformation defects and locomotor deficit, and could be considered as a potential therapeutic compound for this hereditary spastic paraplegia subtype.

Case Reports: Novel Missense Variants in the Filamin C Actin Binding Domain Cause Variable Phenotypes

Filamin C is a large dimeric actin-binding protein, most prevalent in skeletal and cardiac muscle Z-discs, where it participates in sarcomere mechanical stabilization and intracellular signaling, interacting with numerous binding partners. Dominant heterozygous mutations of Filamin C gene cause several forms of myopathy and structural or arrhythmogenic cardiomyopathy. In this report we describe clinical and molecular findings of two Italian patients, in whom we identified two novel missense variants located within the Filamin C actin binding domain. Muscle imaging, histological and ultrastructural findings are also reported. Our results underline the extreme inter- and intrafamilial variability of clinical manifestations, hence the need to extend the investigation also to asymptomatic relatives, and the relevance of a broad diagnostic approach involving muscle electron microscopy, skeletal muscle magnetic resonance imaging and next generation sequencing techniques.

Clinical and genetic features of a cohort of patients with MFN2-related neuropathy

Charcot–Marie–Tooth disease type 2A (CMT2A) is a rare inherited axonal neuropathy caused by mutations in MFN2 gene, which encodes Mitofusin 2, a transmembrane protein of the outer mitochondrial membrane. We performed a cross-sectional analysis on thirteen patients carrying mutations in MFN2, from ten families, describing their clinical and genetic characteristics. Evaluated patients presented a variable age of onset and a wide phenotypic spectrum, with most patients presenting a severe phenotype. A novel heterozygous missense variant was detected, p.K357E. It is located at a highly conserved position and predicted as pathogenic by in silico tools. At a clinical level, the p.K357E carrier shows a severe sensorimotor axonal neuropathy. In conclusion, our work expands the genetic spectrum of CMT2A, disclosing a novel mutation and its related clinical effect, and provides a detailed description of the clinical features of a cohort of patients with MFN2 mutations. Obtaining a precise genetic diagnosis in affected families is crucial both for family planning and prenatal diagnosis, and in a therapeutic perspective, as we are entering the era of personalized therapy for genetic diseases.

Clinical-Genetic Features Influencing Disability in Spastic Paraplegia Type 4

Background and Objectives

Hereditary spastic paraplegias (HSPs) are a group of inherited rare neurologic disorders characterized by length-dependent degeneration of the corticospinal tracts and dorsal columns, whose prominent clinical feature is represented by spastic gait. Spastic paraplegia type 4 (SPG4, SPAST-HSP) is the most common form. We present both clinical and molecular findings of a large cohort of patients, with the aim of (1) defining the clinical spectrum of SPAST-HSP in Italy; (2) describing their molecular features; and (3) assessing genotype-phenotype correlations to identify features associated with worse disability.

Methods

A cross-sectional retrospective study with molecular and clinical data collected in an anonymized database was performed.

Results

A total of 723 Italian patients with SPAST-HSP (58% men) from 316 families, with a median age at onset of 35 years, were included. Penetrance was 97.8%, with men showing higher Spastic Paraplegia Rating Scale (SPRS) scores (19.67 ± 12.58 vs 16.15 ± 12.61, p = 0.009). In 26.6% of patients with SPAST-HSP, we observed a complicated phenotype, mainly including intellectual disability (8%), polyneuropathy (6.7%), and cognitive decline (6.5%). Late-onset cases seemed to progress more rapidly, and patients with a longer disease course displayed a more severe neurologic disability, with higher SPATAX (3.61 ± 1.46 vs 2.71 ± 1.20, p < 0.001) and SPRS scores (22.63 ± 11.81 vs 12.40 ± 8.83, p < 0.001). Overall, 186 different variants in the SPAST gene were recorded, of which 48 were novel. Patients with SPAST-HSP harboring missense variants displayed intellectual disability (14.5% vs 4.4%, p < 0.001) more frequently, whereas patients with truncating variants presented more commonly cognitive decline (9.7% vs 2.6%, p = 0.001), cerebral atrophy (11.2% vs 3.4%, p = 0.003), lower limb spasticity (61.5% vs 44.5%), urinary symptoms (50.0% vs 31.3%, p < 0.001), and sensorimotor polyneuropathy (11.1% vs 1.1%, p < 0.001). Increasing disease duration (DD) and abnormal motor evoked potentials (MEPs) were also associated with increased likelihood of worse disability (SPATAX score>3).

Discussion

The SPAST-HSP phenotypic spectrum in Italian patients confirms a predominantly pure form of HSP with mild-to-moderate disability in 75% of cases, and slight prevalence of men, who appeared more severely affected. Early-onset cases with intellectual disability were more frequent among patients carrying missense SPAST variants, whereas patients with truncating variants showed a more complicated disease. Both longer DD and altered MEPs are associated with worse disability.

Monoallelic KIF1A-related disorders: a multicenter cross sectional study and systematic literature review

BACKGROUND

Monoallelic variants in the KIF1A gene are associated with a large set of clinical phenotypes including neurodevelopmental and neurodegenerative disorders, underpinned by a broad spectrum of central and peripheral nervous system involvement.

METHODS

In a multicenter study conducted in patients presenting spastic gait or complex neurodevelopmental disorders, we analyzed the clinical, genetic and neuroradiological features of 28 index cases harboring heterozygous variants in KIF1A. We conducted a literature systematic review with the aim to comparing our findings with previously reported KIF1A-related phenotypes.

RESULTS

Among 28 patients, we identified nine novel monoallelic variants, and one a copy number variation encompassing KIF1A. Mutations arose de novo in most patients and were prevalently located in the motor domain. Most patients presented features of a continuum ataxia-spasticity spectrum with only five cases showing a prevalently pure spastic phenotype and six presenting congenital ataxias. Seventeen mutations occurred in the motor domain of the Kinesin-1A protein, but location of mutation did not correlate with neurological and imaging presentations. When tested in 15 patients, muscle biopsy showed oxidative metabolism alterations (6 cases), impaired respiratory chain complexes II + III activity (3/6) and low CoQ10 levels (6/9). Ubiquinol supplementation (1gr/die) was used in 6 patients with subjective benefit.

CONCLUSIONS

This study broadened our clinical, genetic, and neuroimaging knowledge of KIF1A-related disorders. Although highly heterogeneous, it seems that manifestations of ataxia-spasticity spectrum disorders seem to occur in most patients. Some patients also present secondary impairment of oxidative metabolism; in this subset, ubiquinol supplementation therapy might be appropriate.

Long-term follow-up in a cohort of children with isolated corpus callosum agenesis at fetal MRI

Objective

This long‐term retrospective follow‐up study aimed to address the knowledge gap between prenatal diagnosis of complete isolated Agenesis of Corpus Callosum (cACC) at fetal MRI and postnatal neurodevelopmental outcome to improve prenatal counseling for parents.

Methods

Data on fetuses with isolated cACC from a single‐center MRI database built up in two decades were considered. Detailed postnatal clinical, neuropsychological evaluations were performed and descriptions of available neuroradiological and genetic data were provided.

Results

Following a detailed neuropsychological evaluation and a long‐term follow‐up, the subsequent results emerged: 38 school‐aged children (older than 6 years) of 50 (aged 2.5‐15 years) showed normal intellectual functions (50%), intellectual disability (21%), and borderline intelligence quotient (29%). Deficits in motor functions (58%), executive functions (37%), language (61%), memory abilities (58%), and academic performances (53%) were found. Twenty‐one percent of participants showed behavioral difficulties. Almost half of the participants underwent rehabilitation. Additional findings (21%) were detected at postnatal brain MRI, and a significant association between additional findings at postnatal imaging and abnormal neurodevelopmental outcome was observed.

Interpretations

This study supports the view that children with prenatal diagnosis of isolated cACC may present with several degrees of neurologic and neuropsychological impairment which become more evident only in their second decade of life. Postnatal MRI and detailed genetic analysis may add crucial information to prenatal data and substantially influence final judgment on the outcome and orient clinical management and counseling.

Acid Sphingomyelinase Controls Early Phases of Skeletal Muscle Regeneration by Shaping the Macrophage Phenotype

Skeletal muscle regeneration is a complex process involving crosstalk between immune cells and myogenic precursor cells, i.e., satellite cells. In this scenario, macrophage recruitment in damaged muscles is a mandatory step for tissue repair since pro-inflammatory M1 macrophages promote the activation of satellite cells, stimulating their proliferation and then, after switching into anti-inflammatory M2 macrophages, they prompt satellite cells' differentiation into myotubes and resolve inflammation. Here, we show that acid sphingomyelinase (ASMase), a key enzyme in sphingolipid metabolism, is activated after skeletal muscle injury induced in vivo by the injection of cardiotoxin. ASMase ablation shortens the early phases of skeletal muscle regeneration without affecting satellite cell behavior. Of interest, ASMase regulates the balance between M1 and M2 macrophages in the injured muscles so that the absence of the enzyme reduces inflammation. The analysis of macrophage populations indicates that these events depend on the altered polarization of M1 macrophages towards an M2 phenotype. Our results unravel a novel role of ASMase in regulating immune response during muscle regeneration/repair and suggest ASMase as a supplemental therapeutic target in conditions of redundant inflammation that impairs muscle recovery.

Novel SPTBN2 gene mutation and first intragenic deletion in early onset spinocerebellar ataxia type 5

In the present study, we describe two novel cases of SCA5 with early onset. The first one, carrying a novel heterozygous de novo missense mutation in SPTBN2 gene, showed a striking very severe cerebellar atrophy and reduction of volume of the pons at a very young age (16 months). The latter, carrying the first de novo intragenic deletion so far reported in SPTBN2 gene, showed a mild cerebellar atrophy involving the hemispheres and a later onset. In both cases, for the first time, a hyperintense signal of the dentate nuclei was observed.

Refining the mutational spectrum and gene-phenotype correlates in pontocerebellar hypoplasia: results of a multicentric study

BACKGROUND

Pontocerebellar hypoplasias (PCH) comprise a group of genetically heterogeneous disorders characterised by concurrent hypoplasia of the pons and the cerebellum and variable clinical and imaging features. The current classification includes 13 subtypes, with ~20 known causative genes. Attempts have been made to delineate the phenotypic spectrum associated to specific PCH genes, yet clinical and neuroradiological features are not consistent across studies, making it difficult to define gene-specific outcomes.

METHODS

We performed deep clinical and imaging phenotyping in 56 probands with a neuroradiological diagnosis of PCH, who underwent NGS-based panel sequencing of PCH genes and MLPA for CASK rearrangements. Next, we conducted a phenotype-based unsupervised hierarchical cluster analysis to investigate associations between genes and specific phenotypic clusters.

RESULTS

A genetic diagnosis was obtained in 43 probands (77%). The most common causative gene was CASK, which accounted for nearly half cases (45%) and was mutated in females and occasionally in males. The European founder mutation p.Ala307Ser in TSEN54 and pathogenic variants in EXOSC3 accounted for 18% and 9% of cases, respectively. VLDLR, TOE1 and RARS2 were mutated in single patients. We were able to confirm only few previously reported associations, including jitteriness and clonus with TSEN54 and lower motor neuron signs with EXOSC3. When considering multiple features simultaneously, a clear association with a phenotypic cluster only emerged for EXOSC3.

CONCLUSION

CASK represents the major PCH causative gene in Italy. Phenotypic variability associated with the most common genetic causes of PCH is wider than previously thought, with marked overlap between CASK and TSEN54-associated disorders.

Loss of ap4s1 in zebrafish leads to neurodevelopmental defects resembling spastic paraplegia 52

Autosomal recessive spastic paraplegia 52 is caused by biallelic mutations in AP4S1 which encodes a subunit of the adaptor protein complex 4 (AP‐4). Using next‐generation sequencing, we identified three novel unrelated SPG52 patients from a cohort of patients with cerebral palsy. The discovered variants in AP4S1 lead to reduced AP‐4 complex formation in patient‐derived fibroblasts. To further understand the role of AP4S1 in neuronal development and homeostasis, we engineered the first zebrafish model of AP‐4 deficiency using morpholino‐mediated knockdown of ap4s1. In this model, we discovered several phenotypes mimicking SPG52, including altered CNS development, locomotor deficits, and abnormal neuronal excitability.

FAHN/SPG35: a narrow phenotypic spectrum across disease classifications

The endoplasmic reticulum enzyme fatty acid 2-hydroxylase (FA2H) plays a major role in the formation of 2-hydroxy glycosphingolipids, main components of myelin. FA2H deficiency in mice leads to severe central demyelination and axon loss. In humans it has been associated with phenotypes from the neurodegeneration with brain iron accumulation (fatty acid hydroxylase-associated neurodegeneration, FAHN), hereditary spastic paraplegia (HSP type SPG35) and leukodystrophy (leukodystrophy with spasticity and dystonia) spectrum. We performed an in-depth clinical and retrospective neurophysiological and imaging study in a cohort of 19 cases with biallelic FA2H mutations. FAHN/SPG35 manifests with early childhood onset predominantly lower limb spastic tetraparesis and truncal instability, dysarthria, dysphagia, cerebellar ataxia, and cognitive deficits, often accompanied by exotropia and movement disorders. The disease is rapidly progressive with loss of ambulation after a median of 7 years after disease onset and demonstrates little interindividual variability. The hair of FAHN/SPG35 patients shows a bristle-like appearance; scanning electron microscopy of patient hair shafts reveals deformities (longitudinal grooves) as well as plaque-like adhesions to the hair, likely caused by an abnormal sebum composition also described in a mouse model of FA2H deficiency. Characteristic imaging features of FAHN/SPG35 can be summarized by the 'WHAT' acronym: white matter changes, hypointensity of the globus pallidus, ponto-cerebellar atrophy, and thin corpus callosum. At least three of four imaging features are present in 85% of FA2H mutation carriers. Here, we report the first systematic, large cohort study in FAHN/SPG35 and determine the phenotypic spectrum, define the disease course and identify clinical and imaging biomarkers.

Loss of paraplegin drives spasticity rather than ataxia in a cohort of 241 patients with SPG7

OBJECTIVE

We took advantage of a large multinational recruitment to delineate genotype-phenotype correlations in a large, trans-European multicenter cohort of patients with spastic paraplegia gene 7 (SPG7).

METHODS

We analyzed clinical and genetic data from 241 patients with SPG7, integrating neurologic follow-up data. One case was examined neuropathologically.

RESULTS

Patients with SPG7 had a mean age of 35.5 ± 14.3 years (n = 233) at onset and presented with spasticity (n = 89), ataxia (n = 74), or both (n = 45). At the first visit, patients with a longer disease duration (>20 years, n = 62) showed more cerebellar dysarthria (p < 0.05), deep sensory loss (p < 0.01), muscle wasting (p < 0.01), ophthalmoplegia (p < 0.05), and sphincter dysfunction (p < 0.05) than those with a shorter duration (<10 years, n = 93). Progression, measured by Scale for the Assessment and Rating of Ataxia evaluations, showed a mean annual increase of 1.0 ± 1.4 points in a subgroup of 30 patients. Patients homozygous for loss of function (LOF) variants (n = 65) presented significantly more often with pyramidal signs (p < 0.05), diminished visual acuity due to optic atrophy (p < 0.0001), and deep sensory loss (p < 0.0001) than those with at least 1 missense variant (n = 176). Patients with at least 1 Ala510Val variant (58%) were older (age 37.6 ± 13.7 vs 32.8 ± 14.6 years, p < 0.05) and showed ataxia at onset (p < 0.05). Neuropathologic examination revealed reduction of the pyramidal tract in the medulla oblongata and moderate loss of Purkinje cells and substantia nigra neurons.

CONCLUSIONS

This is the largest SPG7 cohort study to date and shows a spasticity-predominant phenotype of LOF variants and more frequent cerebellar ataxia and later onset in patients carrying at least 1 Ala510Val variant.

The Fine Tuning of Drp1-Dependent Mitochondrial Remodeling and Autophagy Controls Neuronal Differentiation

Mitochondria play a critical role in neuronal function and neurodegenerative disorders, including Alzheimer’s, Parkinson’s and Huntington diseases and amyotrophic lateral sclerosis, that show mitochondrial dysfunctions associated with excessive fission and increased levels of the fission protein dynamin-related protein 1 (Drp1). Our data demonstrate that Drp1 regulates the transcriptional program induced by retinoic acid (RA), leading to neuronal differentiation. When Drp1 was overexpressed, mitochondria underwent remodeling but failed to elongate and this enhanced autophagy and apoptosis. When Drp1 was blocked during differentiation by overexpressing the dominant negative form or was silenced, mitochondria maintained the same elongated shape, without remodeling and this increased cell death. The enhanced apoptosis, observed with both fragmented or elongated mitochondria, was associated with increased induction of unfolded protein response (UPR) and ER-associated degradation (ERAD) processes that finally affect neuronal differentiation. These findings suggest that physiological fission and mitochondrial remodeling, associated with early autophagy induction are essential for neuronal differentiation. We thus reveal the importance of mitochondrial changes to generate viable neurons and highlight that, rather than multiple parallel events, mitochondrial changes, autophagy and apoptosis proceed in a stepwise fashion during neuronal differentiation affecting the nuclear transcriptional program.

Broadening the Spectrum of Adulthood X-Linked Adrenoleukodystrophy: A Report of Two Atypical Cases

X-linked adrenoleukodystrophy (x-ALD) is a rare genetic disorder caused by a mutation in the ABCD1 gene, which encodes for a peroxisomal very long chain fatty acid transporter. Clinically, x-ALD can present a wide spectrum of different phenotypes: asymptomatic carriers, Addison only, cerebral x-ALD, and myelopathy with/without evidence of peripheral axonopathy (Adrenomyeloneuropathy). We report on two cases of adult x-ALD, with atypical phenotypes: (Case 1) A 37-years-old male with a 2-years-long history of spastic paraparesis, urinary urgency, and subclinical adrenocortical insufficiency. As an atypical finding, the MRI showed multiple congenital brain development defects. (Case 2) A 63-years-old male with a previous diagnosis of Addison disease, with a 6-years-long history of spastic paraparesis. Two years later, he complained of severe and disabling burning pain in his feet. A nerve conduction study was normal, but a skin biopsy revealed autonomic and somatic small fiber neuropathy. In both cases, genetic testing disclosed hemizygous mutation in ABCD1 associated with x-ALD: c.1394-2A > G and p.(Thr254Met), respectively. While case 1 supports the key role of peroxisome functions in brain development, case 2 points to a possible selective and clinically relevant peripheral small fiber degeneration in x-ALD myelopathy.

Charcot-Marie-Tooth disease with pyramidal features due to a new mutation of EGR2 gene

Background and aim of the work: Childhood-onset peripheral neuropathies are often of genetic origin. Charcot-Marie-Tooth (CMT), is considered the commonest neuromuscular disorder. Due to its high clinical heterogeneity, especially in the pediatric age, the co-existence of central and peripheral symptoms and signs does not necessarily rule out a diagnosis of hereditary peripheral neuropathy. Methods: We describe the clinical, neurophysiological and genetic findings in a teen-age patient evaluated for acquired toe-walking and progressive difficulties in walking since the age of 5. Genetic testing was carried out with a targeted NGS panel. Identified variants are analyzed using Variant Studio program (Illumina). Rare variants and variants considered as pathogenic were analyzed by Sanger direct sequencing. Results: The coexistence ofperipheral and pyramidal signs in the lower limbs, the absence of a significant pre/perinatal history, the unremarkable brain and spine MRI, together with the presence of a sensory-motor polyneuropathy in all four limbs, prompted the execution of genetic investigations with an NGS panel covering hereditary spastic paraplegias, motor neuron disease and Charcot-Marie-Tooth. We identified a previously undescribed variant (c.1142G>T, p.Arg381Leu) in the EGR2 gene. Conclusions:ERG2 gene has been described as a cause of various phenotypes, including a rare autosomal dominant form of CMT (CMT type 1D) representing approximately 1% of all CMT subgroups. We describe a novel pathogenic variant in EGR2 gene leading to the development of a complex association of peripheral and central neurological signs, underscoring the genetic and clinical heterogeneity of hereditary neuropathies of pediatric onset. (www.actabiomedica.it)

"Ears of the Lynx" MRI Sign Is Associated with SPG11 and SPG15 Hereditary Spastic Paraplegia

BACKGROUND AND PURPOSE

The "ears of the lynx" MR imaging sign has been described in case reports of hereditary spastic paraplegia with a thin corpus callosum, mostly associated with mutations in the spatacsin vesicle trafficking associated gene, causing Spastic Paraplegia type 11 (SPG11). This sign corresponds to long T1 and T2 values in the forceps minor of the corpus callosum, which appears hyperintense on FLAIR and hypointense on T1-weighted images. Our purpose was to determine the sensitivity and specificity of the ears of the lynx MR imaging sign for genetic cases compared with common potential mimics.

MATERIALS AND METHODS

Four independent raters, blinded to the diagnosis, determined whether the ears of the lynx sign was present in each of a set of 204 single anonymized FLAIR and T1-weighted MR images from 34 patients with causal mutations associated with SPG11 or Spastic Paraplegia type 15 (SPG15). 34 healthy controls, and 34 patients with multiple sclerosis.

RESULTS

The interrater reliability for FLAIR images was substantial (Cohen κ, 0.66-0.77). For these images, the sensitivity of the ears of the lynx sign across raters ranged from 78.8 to 97.0 and the specificity ranged from 90.9 to 100. The accuracy of the sign, measured by area under the receiver operating characteristic curve, ranged from very good (87.1) to excellent (93.9).

CONCLUSIONS

The ears of the lynx sign on FLAIR MR imaging is highly specific for the most common genetic subtypes of hereditary spastic paraplegia with a thin corpus callosum. When this sign is present, there is a high likelihood of a genetic mutation, particularly associated with SPG11 or SPG15, even in the absence of a family history.

KIF5A and ALS2 Variants in a Family With Hereditary Spastic Paraplegia and Amyotrophic Lateral Sclerosis

This paper describes the clinical evolution and the novel genetic findings in a KIF5A mutated family previously reported as affected by spastic paraparesis only. The additional evidence we report here, a homozygous ALS2 mutation detected in the proband, and the clinical evolution observed in the affected members of the family, are in line with the evidence of an overlap between Hereditary Spastic Paraplegias and Amyotrophic Lateral Sclerosis associated with variants in these genes. The proband, a 14-years-old boy, started manifesting a pure form of HSP at age 14 months. The disease rapidly progressed to a juvenile form of ALS. This boy carries a heterozygous missense variant in KIF5A p.(Glu755Lys), inherited from the father, and a homozygous missense variant in the alsin protein encoded by the ALS2 gene p.(Pro192Leu). The father shows a family history of ALS. In the last few years, he has been developing signs and symptoms of both upper and lower motor neuron degeneration, with mild bulbar motor involvement and emotional lability. The patients described in this family, confirm the continuum and partial overlap of the two clinical entities, HSP and ALS, historically viewed as distinct entities. The genetic findings in this family further substantiate the genetic bases underlying the overlap, broadening the clinical spectrum associated with KIF5A mutations.

Tensor-based morphometry using scalar and directional information of diffusion tensor MRI data (DTBM): Application to hereditary spastic paraplegia

Tensor-based morphometry (TBM) performed using T1-weighted images (T1WIs) is a well-established method for analyzing local morphological changes occurring in the brain due to normal aging and disease. However, in white matter regions that appear homogeneous on T1WIs, T1W-TBM may be inadequate for detecting changes that affect specific pathways. In these regions, diffusion tensor MRI (DTI) can identify white matter pathways on the basis of their different anisotropy and orientation. In this study, we propose performing TBM using deformation fields constructed using all scalar and directional information provided by the diffusion tensor (DTBM) with the goal of increasing sensitivity in detecting morphological abnormalities of specific white matter pathways. Previously, mostly fractional anisotropy (FA) has been used to drive registration in diffusion MRI-based TBM (FA-TBM). However, FA does not have the directional information that the tensors contain, therefore, the registration based on tensors provides better alignment of brain structures and better localization of volume change. We compare our DTBM method to both T1W-TBM and FA-TBM in investigating differences in brain morphology between patients with complicated hereditary spastic paraplegia of type 11 (SPG11) and a group of healthy controls. Effect size maps of T1W-TBM of SPG11 patients showed diffuse atrophy of white matter. However, DTBM indicated that atrophy was more localized, predominantly affecting several long-range pathways. The results of our study suggest that DTBM could be a powerful tool for detecting morphological changes of specific white matter pathways in normal brain development and aging, as well as in degenerative disorders.

ZFYVE26/SPASTIZIN and SPG11/SPATACSIN mutations in hereditary spastic paraplegia types AR-SPG15 and AR-SPG11 have different effects on autophagy and endocytosis

ZFYVE26/Spastizin and SPG11/Spatacsin encode 2 large proteins that are mutated in hereditary autosomal-recessive spastic paraplegia/paraparesis (HSP) type 15 (AR-SPG15) and type 11 (AR-SPG11), respectively. We previously have reported that AR-SPG15-related ZFYVE26 mutations lead to autophagy defects with accumulation of immature autophagosomes. ZFYVE26 and SPG11 were found to be part of a complex including the AP5 (adaptor related protein complex 5) and to have a critical role in autophagic lysosomal reformation with identification of autophagic and lysosomal defects in cells with both AR-SPG15- and AR-SPG11-related mutations. In spite of these similarities between the 2 proteins, here we report that ZFYVE26 and SPG11 are differently involved in autophagy and endocytosis. We found that both ZFYVE26 and SPG11 interact with RAB5A and RAB11, 2 proteins regulating endosome trafficking and maturation, but only ZFYVE26 mutations affected RAB protein interactions and activation. ZFYVE26 mutations lead to defects in the fusion between autophagosomes and endosomes, while SPG11 mutations do not affect this step and lead to a milder autophagy defect. We thus demonstrate that ZFYVE26 and SPG11 affect the same cellular physiological processes, albeit at different levels: both proteins have a role in autophagic lysosome reformation, but only ZFYVE26 acts at the intersection between endocytosis and autophagy, thus representing a key player in these 2 processes. Indeed expression of the constitutively active form of RAB5A in cells with AR-SPG15-related mutations partially rescues the autophagy defect. Finally the model we propose demonstrates that autophagy and the endolysosomal pathway are central processes in the pathogenesis of these complicated forms of hereditary spastic paraparesis. Abbreviations: ALR, autophagic lysosome reformation; AP5, adaptor related protein complex 5; AR, autosomal-recessive; HSP, hereditary spastic paraplegia/paraparesis; ATG14, autophagy related 14; BafA, bafilomycin A₁; BECN1, beclin 1; EBSS, Earle balanced salt solution; EEA1, early endosome antigen 1; EGF, epidermal growth factor; EGFR, epidermal growth factor receptor; GDP, guanosine diphosphate; GFP, green fluorescent protein; GTP, guanosine triphosphate; HSP, hereditary spastic paraplegias; LBPA, lysobisphosphatidic acid; MAP1LC3B/LC3B, microtubule associated protein 1 light chain 3 beta; MVBs, multivesicular bodies; PIK3C3, phosphatidylinositol 3-kinase, catalytic subunit type 3; PIK3R4, phosphoinositide-3-kinase regulatory subunit 4; PtdIns3P, phosphatidylinositol-3-phosphate; RFP, red fluorescent protein; RUBCN, RUN and cysteine rich domain containing beclin 1 interacting protein; shRNA, short hairpin RNA; SQSTM1/p62, sequestosome 1; TCC: thin corpus callosum; TF, transferrin; UVRAG, UV radiation resistance associated.

Autophagy controls neonatal myogenesis by regulating the GH-IGF1 system through a NFE2L2- and DDIT3-mediated mechanism

Macroautophagy/autophagy is emerging as an important process in adult muscle stem cells functions: it regulates metabolic reprogramming during activation from a quiescent state, maintains stemness and prevents senescence. We now show that autophagy is specifically required for neonatal myogenesis and muscle development. Specific deletion of Atg7 in PAX7⁺ (paired box 7) precursors led in mice to a dwarf phenotype, with an effect restricted to the neonatal phase of muscle development. Atg7 knockdown suppressed neonatal satellite cell (nSC) proliferation and differentiation, downregulating the GH-IGF1 functions. When we disrupted autophagy, NFE2L2/NRF2 (nuclear factor, erythroid 2 like 2) accumulated in muscle and nSCs and negatively modulated DDIT3/CHOP (DNA-damage inducible transcript 3) expression. Lower levels of DDIT3 were responsible for reduced GHR expression leading to impaired local production of IGF1. Our results conclusively identify a novel autophagy-dependent pathway that regulates nSC behavior and indicate that autophagy is required for skeletal muscle development in the neonatal phase. Abbreviations: AKT/protein kinase B: Thymoma viral proto-oncogene; ASCs: adult stem cells; ATF4: activating transcription factor 4; ATG7: autophagy related 7; BAT: brown adipose tissue; BMP: bone morphogenetic protein; CEBPB: CCAAT/enhancer binding protein (C/EBP), beta; CSA: cross sectional area; CTNNB1: catenin (cadherin associated protein), beta 1; DDIT3: DNA-damage inducible transcript 3; DM: differentiation medium; E: embryonic stage; EIF2AK3/PERK; EIF4EBP1: eukaryotic translation initiation factor 2 alpha kinase 3; eukaryotic translation initiation factor 4E binding protein 1; ER: endoplasmic reticulum; FGF21: fibroblast growth factor 21; GH: growth hormone; GHR: growth hormone receptor; HSCs: hematopoietic stem cells; IGF1: insulin-like growth factor 1; ITGAM: integrin alpha M; KEAP1: kelch-like ECH-associated protein 1; LY6A/Sca-1; MAP1LC3: lymphocyte antigen 6 complex, locus A; microtubule-associated protein 1 light chain 3; MAPK1/ERK2: mitogen-activated protein kinase 1; MAPK3/ERK1: mitogen-activated protein kinase 3; miRNAs: microRNAs; MSCs: mesenchymal stem cells; MTOR: mechanistic target of rapamycin kinase; mtUPR: mitochondrial unfolded protein response; MYF5: myogenic factor 5; MYH: myosin, heavy polypeptide; MYOD1: myogenic differentiation 1; MYOG: myogenin; NFE2L2: nuclear factor, erythroid derived 2, like 2; nSC: neonatal satellite cells; NSCs: neuronal stem cells; P: postnatal day; PAX7: paired box 7; PECAM1: platelet/endothelial cell adhesion molecule 1; PPARG: peroxisome proliferator activated receptor gamma; PTPRC: protein tyrosine phosphatase, receptor type, C; ROS: reactive oxygen species; RPS6: ribosomal protein S6; SCs: adult satellite cells; SQSTM1: sequestosome 1; STAT5: signal transducer and activator of transcription 5; TGFB1: transforming growth factor beta 1; WAT: white adipose tissue; WT: wild type.

Nitric Oxide Generated by Tumor-Associated Macrophages Is Responsible for Cancer Resistance to Cisplatin and Correlated With Syntaxin 4 and Acid Sphingomyelinase Inhibition

Tumor microenvironment is fundamental for cancer progression and chemoresistance. Among stromal cells tumor-associated macrophages (TAMs) represent the largest population of infiltrating inflammatory cells in malignant tumors, promoting their growth, invasion, and immune evasion. M2-polarized TAMs are endowed with the nitric oxide (NO)-generating enzyme inducible nitric oxide synthase (iNOS). NO has divergent effects on tumors, since it can either stimulate tumor cells growth or promote their death depending on the source of it; likewise the role of iNOS in cancer differs depending on the cell type. The role of NO generated by TAMs has not been investigated. Using different tumor models in vitro and in vivo we found that NO generated by iNOS of M2-polarized TAMs is able to protect tumor cells from apoptosis induced by the chemotherapeutic agent cisplatin (CDDP). Here, we demonstrate that the protective effect of NO depends on the inhibition of acid sphingomyelinase (A-SMase), which is activated by CDDP in a pathway involving the death receptor CD95. Mechanistic insights indicate that NO actions occur via generation of cyclic GMP and activation of protein kinase G (PKG), inducing phosphorylation of syntaxin 4 (synt4), a SNARE protein responsible for A-SMase trafficking and activation. Noteworthy, phosphorylation of synt4 at serine 78 by PKG is responsible for the proteasome-dependent degradation of synt4, which limits the CDDP-induced exposure of A-SMase to the plasma membrane of tumor cells. This inhibits the cytotoxic mechanism of CDDP reducing A-SMase-triggered apoptosis. This is the first demonstration that endogenous NO system is a key mechanism through which TAMs protect tumor cells from chemotherapeutic drug-induced apoptosis. The identification of the pathway responsible for A-SMase activity downregulation in tumors leading to chemoresistance warrants further investigations as a means to identify new anti-cancer molecules capable of specifically inhibiting synt4 degradation.

Hereditary spastic paraplegia type 5: natural history, biomarkers and a randomized controlled trial

Spastic paraplegia type 5 (SPG5) is a rare subtype of hereditary spastic paraplegia, a highly heterogeneous group of neurodegenerative disorders defined by progressive neurodegeneration of the corticospinal tract motor neurons. SPG5 is caused by recessive mutations in the gene CYP7B1 encoding oxysterol-7α-hydroxylase. This enzyme is involved in the degradation of cholesterol into primary bile acids. CYP7B1 deficiency has been shown to lead to accumulation of neurotoxic oxysterols. In this multicentre study, we have performed detailed clinical and biochemical analysis in 34 genetically confirmed SPG5 cases from 28 families, studied dose-dependent neurotoxicity of oxysterols in human cortical neurons and performed a randomized placebo-controlled double blind interventional trial targeting oxysterol accumulation in serum of SPG5 patients. Clinically, SPG5 manifested in childhood or adolescence (median 13 years). Gait ataxia was a common feature. SPG5 patients lost the ability to walk independently after a median disease duration of 23 years and became wheelchair dependent after a median 33 years. The overall cross-sectional progression rate of 0.56 points on the Spastic Paraplegia Rating Scale per year was slightly lower than the longitudinal progression rate of 0.80 points per year. Biochemically, marked accumulation of CYP7B1 substrates including 27-hydroxycholesterol was confirmed in serum (n = 19) and cerebrospinal fluid (n = 17) of SPG5 patients. Moreover, 27-hydroxycholesterol levels in serum correlated with disease severity and disease duration. Oxysterols were found to impair metabolic activity and viability of human cortical neurons at concentrations found in SPG5 patients, indicating that elevated levels of oxysterols might be key pathogenic factors in SPG5. We thus performed a randomized placebo-controlled trial (EudraCT 2015-000978-35) with atorvastatin 40 mg/day for 9 weeks in 14 SPG5 patients with 27-hydroxycholesterol levels in serum as the primary outcome measure. Atorvastatin, but not placebo, reduced serum 27-hydroxycholesterol from 853 ng/ml [interquartile range (IQR) 683-1113] to 641 (IQR 507-694) (-31.5%, P = 0.001, Mann-Whitney U-test). Similarly, 25-hydroxycholesterol levels in serum were reduced. In cerebrospinal fluid 27-hydroxycholesterol was reduced by 8.4% but this did not significantly differ from placebo. As expected, no effects were seen on clinical outcome parameters in this short-term trial. In this study, we define the mutational and phenotypic spectrum of SPG5, examine the correlation of disease severity and progression with oxysterol concentrations, and demonstrate in a randomized controlled trial that atorvastatin treatment can effectively lower 27-hydroxycholesterol levels in serum of SPG5 patients. We thus demonstrate the first causal treatment strategy in hereditary spastic paraplegia.

Reversal of Defective Mitochondrial Biogenesis in Limb-Girdle Muscular Dystrophy 2D by Independent Modulation of Histone and PGC-1α Acetylation

Mitochondrial dysfunction occurs in many muscle degenerative disorders. Here, we demonstrate that mitochondrial biogenesis was impaired in limb-girdle muscular dystrophy (LGMD) 2D patients and mice and was associated with impaired OxPhos capacity. Two distinct approaches that modulated histones or peroxisome proliferator-activated receptor-gamma coactivator 1 α (PGC-1α) acetylation exerted equivalent functional effects by targeting different mitochondrial pathways (mitochondrial biogenesis or fatty acid oxidation[FAO]). The histone deacetylase inhibitor Trichostatin A (TSA) changed chromatin assembly at the PGC-1α promoter, restored mitochondrial biogenesis, and enhanced muscle oxidative capacity. Conversely, nitric oxide (NO) triggered post translation modifications of PGC-1α and induced FAO, recovering the bioenergetics impairment of muscles but shunting the defective mitochondrial biogenesis. In conclusion, a transcriptional blockade of mitochondrial biogenesis occurred in LGMD-2D and could be recovered by TSA changing chromatin conformation, or it could be overcome by NO activating a mitochondrial salvage pathway.

Clinical and Paraclinical Indicators of Motor System Impairment in Hereditary Spastic Paraplegia: A Pilot Study

BACKGROUND

Hereditary spastic paraplegias (HSP) are a composite and genetically heterogeneous group of conditions mainly expressed by the impairment of the central motor system ("pure" forms). The involvement of other components of the central nervous system or of other systems is described in the "complicate" forms. The definition of an investigation protocol capable, by assembling clinical and paraclinical indicators to fully represent the extent of the motor system impairment, would help both the clinical handling of these conditions and contribute to our understanding of their pathogenesis.

METHODS

We applied a clinical and paraclinical protocol which included tools exploring motor and non motor functioning, neurophysiology and MRI to a composite cohort of 70 molecularly defined HSP patients aged 3 to 65, to define for each indicator its significance in detailing the presence and the severity of the pathology.

RESULTS

Clinically increased deep tendon reflexes and lower limb (LL) weakness are constant findings in all patients. The "complicated" forms are characterized by peripheral motor impairment, cognitive and cerebellar involvement. The Spastic Paraplegia Rating Scale efficiently reflects the severity of functional problems and correlates with disease duration. Neurophysiology consistently documents the impairment of the central motor pathway to the LLs. Nevertheless, the upper extremities and sensory system involvement is a frequent finding. MRI diffusion tensor imaging (DTI) highlighted a significant alteration of FA and MD. Combining the sampling of the various portion of the cortico-spinal tract (CST) DTI consistently discriminated patients from controls.

CONCLUSION

We propose a graded clinical and paraclinical protocol for HSP phenotype definition, indicating for each tool the discriminative and descriptive capacity. Our protocol applied to 9 different forms of HSP showed that the functional impairment often extends beyond the CST. The novel DTI approach may add significant elements in disease recognition, staging and mapping.

The emerging role of acid sphingomyelinase in autophagy

Autophagy, the main intracellular process of cytoplasmic material degradation, is involved in cell survival and death. Autophagy is regulated at various levels and novel modulators of its function are being continuously identified. An intriguing recent observation is that among these modulators is the sphingolipid metabolising enzyme, Acid Sphingomyelinase (A-SMase), already known to play a fundamental role in apoptotic cell death participating in several pathophysiological conditions. In this review we analyse and discuss the relationship between autophagy and A-SMase describing how A-SMase may regulate it and defining, for the first time, the existence of an A-SMase-autophagy axis. The imbalance of this axis plays a role in cancer, nervous system, cardiovascular, and hepatic disorders.

Aberrant supracallosal longitudinal bundle: MR features, pathogenesis and associated clinical phenotype

OBJECTIVE

To describe the MRI and structural features of a peculiar malformation of the corpus callosum (CC) in a group of young patients with intellectual disability.

METHODS

We studied with conventional MRI and DTI a group of subjects showing an aberrant supracallosal bundle, characterized by the presence of a triangle-shaped bulging above the dorsal surface of CC on the midline. Clinical evaluations, CGH-array and instrumental analysis were also collected.

RESULTS

Among 85 patients with malformed CC, we identified 15 subjects that showed the supracallosal bundle. The CC was thickened in five cases, long and thinned in three cases, short and thinned in three cases and it had a "ribbon-like" appearance in four subjects. Additional brain anomalies were present in eight cases. DTI colour maps and tractography showed that the bundle had an antero-posterior longitudinal orientation and that the tract bifurcated posteriorly, ending in the posterior hippocampi. Patients had different combinations of neurological symptoms, but all showed mild or severe intellectual disability.

CONCLUSIONS

Combining radiological and genetic data with embryological knowledge of the development of cerebral commissures, we hypothesize that the supracallosal bundle represents a vestigial structure, the dorsal fornix, present during fetal life. Its persistence is associated with intellectual disability.

KEY POINTS

• An aberrant longitudinal bundle can be detected above corpus callosum. • The presence of the supracallosal bundle is associated with intellectual disability. • The supracallosal bundle may represent a persistent dorsal fornix.

Mutations in α- and β-tubulin encoding genes: implications in brain malformations

The tubulin gene family is mainly expressed in post-mitotic neurons during cortical development with a specific spatial and temporal expression pattern. Members of this family encode dimeric proteins consisting of two closely related subunits (α and β), representing the major constituents of microtubules. Tubulin genes play a crucial role in the mechanisms of the Central Nervous System development such as neuronal migration and axonal guidance (axon outgrowth and maintenance). Different mutations in α/β-tubulin genes (TUBA1A, TUBA8, TUBB2A, TUBB4A, TUBB2B, TUBB3, and TUBB) might alter the dynamic properties and functions of microtubules in several ways, effecting a reduction in the number of functional tubulin heterodimers and causing alterations in GTP binding and disruptions of the binding of other proteins to microtubules (motor proteins and other microtubule interacting proteins). In recent years an increasing number of brain malformations has been associated with mutations in tubulin genes: malformations of cortical development such as lissencephaly and various grades of gyral disorganization, focal or diffuse polymicrogyria and open or closed-lips schizencephaly as likely consequences of an altered neuronal migration process; abnormalities or agenesis of the midline commissural structures (anterior commissure, corpus callosum and fornix), hypoplasia of the oculomotor and optic nerves, dysmorphisms of the hind-brain as expression of axon guidance disorders. Dysmorphisms of the basal ganglia (fusion between the caudate nucleus and putamen with absence of the anterior limb of the internal capsule) and hippocampi were also observed. A rare form of leukoencephalopathy characterized by hypomyelination with atrophy of the basal ganglia an cerebellum (H-ABC) was also recently described. The present review, describing the structural and functional features of tubulin genes, aims to revise the main cerebral associated malformations and related clinical aspects, suggesting a genotype-phenotype correlation.

Hereditary Spastic Paraplegia: Beyond Clinical Phenotypes toward a Unified Pattern of Central Nervous System Damage

PURPOSE

To investigate whether specific patterns of brain gray matter (GM) regional volumes and white matter (WM) microstructural abnormalities and spinal cord atrophy occur in patients with pure and complicated hereditary spastic paraplegias (HSPs). Relationships between clinical and cognitive features of patients with HSP who had brain and cervical cord damage were also investigated.

MATERIALS AND METHODS

This study was approved by the local ethical committees on human studies, and written informed consent from all subjects was obtained prior to enrollment. Forty-four patients with HSP (20 genetically defined cases and 24 without genetic diagnosis) and 19 healthy control subjects underwent clinical, neuropsychological, and advanced magnetic resonance (MR) imaging evaluations. Patterns of GM atrophy and WM microstructural damage obtained by using structural and diffusion-tensor MR imaging were compared between groups. Cervical cord atrophy was also assessed by using an active surface method. Correlations between clinical, cognitive, and diffusion-tensor MR imaging measures were evaluated.

RESULTS

Clinical data showed that spastic paraplegia is accompanied by a number of other features, including sensory disturbances, and verbal and spatial memory deficits, not only in complicated HSP but also in pure HSP. MR imaging demonstrated a similar involvement of motor, association, and cerebellar WM pathways (P < .05, family-wise error corrected for multiple comparisons) and cervical cord (P < .001) in patients with HSP relative to healthy control subjects, regardless of their clinical picture. The severity of WM damage correlated with the degree of spasticity (P < .05, family-wise error corrected) and cognitive impairment (r values, -0.39 to 0.51; P values, .001-.05) in both pure and complicated HSP.

CONCLUSION

The detection of a distributed pattern of central nervous system damage in patients with pure and complicated HSP suggests that the "primary" corticospinal tract involvement known to occur in these patients may be associated with a neurodegenerative process, which spreads out to extramotor regions, likely via anatomic connections. This observation is in line with emerging pieces of evidence that, independent of the clinical phenotype, there is a common neurodegenerative cascade shared by different neurologic disorders.

Deficient nitric oxide signalling impairs skeletal muscle growth and performance: involvement of mitochondrial dysregulation

BACKGROUND

Nitric oxide (NO), generated in skeletal muscle mostly by the neuronal NO synthases (nNOSμ), has profound effects on both mitochondrial bioenergetics and muscle development and function. The importance of NO for muscle repair emerges from the observation that nNOS signalling is defective in many genetically diverse skeletal muscle diseases in which muscle repair is dysregulated. How the effects of NO/nNOSμ on mitochondria impact on muscle function, however, has not been investigated yet.

METHODS

In this study we have examined the relationship between the NO system, mitochondrial structure/activity and skeletal muscle phenotype/growth/functions using a mouse model in which nNOSμ is absent. Also, NO-induced effects and the NO pathway were dissected in myogenic precursor cells.

RESULTS

We show that nNOSμ deficiency in mouse skeletal muscle leads to altered mitochondrial bioenergetics and network remodelling, and increased mitochondrial unfolded protein response (UPR(mt)) and autophagy. The absence of nNOSμ is also accompanied by an altered mitochondrial homeostasis in myogenic precursor cells with a decrease in the number of myonuclei per fibre and impaired muscle development at early stages of perinatal growth. No alterations were observed, however, in the overall resting muscle structure, apart from a reduced specific muscle mass and cross sectional areas of the myofibres. Investigating the molecular mechanisms we found that nNOSμ deficiency was associated with an inhibition of the Akt-mammalian target of rapamycin pathway. Concomitantly, the Akt-FoxO3-mitochondrial E3 ubiquitin protein ligase 1 (Mul-1) axis was also dysregulated. In particular, inhibition of nNOS/NO/cyclic guanosine monophosphate (cGMP)/cGMP-dependent-protein kinases induced the transcriptional activity of FoxO3 and increased Mul-1 expression. nNOSμ deficiency was also accompanied by functional changes in muscle with reduced muscle force, decreased resistance to fatigue and increased degeneration/damage post-exercise.

CONCLUSIONS

Our results indicate that nNOSμ/NO is required to regulate key homeostatic mechanisms in skeletal muscle, namely mitochondrial bioenergetics and network remodelling, UPR(mt) and autophagy. These events are likely associated with nNOSμ-dependent impairments of muscle fibre growth resulting in a deficit of muscle performance.

Novel SETX variants in a patient with ataxia, neuropathy, and oculomotor apraxia are associated with normal sensitivity to oxidative DNA damaging agents

BACKGROUND

Homozygous and compound heterozygous mutations in SETX are associated with AOA2 disease, a recessive form of ataxia with oculomotor apraxia and neuropathy with onset of ataxia between the first and second decade of life. The majority of the AOA2 mutated cell lines tested show hypersensitivity to oxidative DNA damaging agents, with one exception.

RESULTS

We describe a patient presenting with early-onset progressive ataxia, oculomotor apraxia, axonal sensory-motor neuropathy, optic atrophy, delayed psychomotor development, and a behavior disorder. The patient carries two novel missense variants in the SETX gene. Based on the hypothesis that the patient's clinical phenotype may represent an atypical form of the AOA2 disease, we tested the patient-derived cell line for hypersensitivity to oxidative DNA damaging agents, with negative results.

CONCLUSIONS

The lack of hypersensitivity we observed may be explained either by considering the atypical clinical picture of the patient analyzed or, alternatively, by hypothesizing that the variants detected are not the cause of the observed phenotype. Consistent with the first hypothesis of an atypical AOA2 form and based on the multiple functions of senataxin reported so far, it is likely that different sets of SETX mutations/variants may have variable functional effects that still need to be functionally characterized. The possibility that the severe and complicated clinical picture presented by the patient described here represents a clinical entity differing from the known recessive ataxias should be considered as well.