Distal hereditary motor neuronopathy as a new phenotype associated with variants in BAG3

OBJECTIVE

To describe a new phenotype associated with a novel variant in BAG3: autosomal dominant adult-onset distal hereditary motor neuronopathy.

METHODS

This study enrolled eight affected individuals from a single family and included a comprehensive evaluation of the clinical phenotype, neurophysiologic testing, muscle MRI, muscle biopsy and western blot of BAG3 protein in skeletal muscle. Genetic workup included whole exome sequencing and segregation analysis of the detected variant in BAG3.

RESULTS

Seven patients developed slowly progressive and symmetric distal weakness and atrophy of lower limb muscles, along with absent Achilles reflexes. The mean age of onset was 46 years. The neurophysiological examination was consistent with the diagnosis of distal motor neuronopathy. One 57-year-old female patient was minimally symptomatic. The pattern of inheritance was autosomal dominant, with one caveat: one female patient who was an obligate carrier of the variant died at the age of 73 years without exhibiting any muscle weakness. The muscle biopsies revealed neurogenic changes. A novel heterozygous truncating variant c.1513_1514insGGAC (p.Val505GlyfsTer6) in the gene BAG3 was identified in all affected family members.

CONCLUSIONS

We report an autosomal dominant adult-onset distal hereditary motor neuronopathy with incomplete penetrance in women as a new phenotype related to a truncating variant in the BAG3 gene. Our findings expand the phenotypic spectrum of BAG3-related disorders, which previously included dilated cardiomyopathy, myofibrillar myopathy and adult-onset Charcot-Marie-Tooth type 2 neuropathy. Variants in BAG3 should be considered in the differential diagnosis of distal hereditary motor neuronopathies.

Genetic Heterogeneity Underlying Phenotypes with Early-Onset Cerebellar Atrophy

Cerebellar atrophy (CA) is a frequent neuroimaging finding in paediatric neurology, usually associated with cerebellar ataxia. The list of genes involved in hereditary forms of CA is continuously growing and reveals its genetic complexity. We investigated ten cases with early-onset cerebellar involvement with and without ataxia by exome sequencing or by a targeted panel with 363 genes involved in ataxia or spastic paraplegia. Novel variants were investigated by in silico or experimental approaches. Seven probands carry causative variants in well-known genes associated with CA or cerebellar hypoplasia: SETX, CACNA1G, CACNA1A, CLN6, CPLANE1, and TBCD. The remaining three cases deserve special attention; they harbour variants in MAST1, PI4KA and CLK2 genes. MAST1 is responsible for an ultrarare condition characterised by global developmental delay and cognitive decline; our index case added ataxia to the list of concomitant associated symptoms. PIK4A is mainly related to hypomyelinating leukodystrophy; our proband presented with pure spastic paraplegia and normal intellectual capacity. Finally, in a patient who suffers from mild ataxia with oculomotor apraxia, the de novo novel CLK2 c.1120T>C variant was found. The protein expression of the mutated protein was reduced, which may indicate instability that would affect its kinase activity.

A novel TRMT5 mutation causes a complex inherited neuropathy syndrome: the role of nerve pathology in defining a demyelinating neuropathy

AIMS

To present data obtained from three patients belonging to three unrelated families with an infantile onset demyelinating neuropathy associated to somatic and neurodevelopmental delay, and to describe the underlying genetic changes.

METHODS

We performed whole-exome sequencing on genomic DNA from the patients and their parents, and reviewed the clinical, muscle and nerve data, the serial neurophysiological studies, brain, and muscle MRIs, as well as the respiratory chain complex activity in the muscle of the three index patients. Computer modelling was used to characterize the new missense variant detected.

RESULTS

All three patients had a short stature, delayed motor milestone acquisition, intellectual disability and cerebellar abnormalities associated with a severe demyelinating neuropathy, with distinct morphological features. Despite the proliferation of giant mitochondria, the mitochondrial respiratory chain complex activity in skeletal muscle was normal, except in one patient in whom there was a mild decrease in complex I enzyme activity. All three patients carried the same two compound heterozygous variants of the TRMT5 (tRNA Methyltransferase 5) gene, one known pathogenic frameshift mutation [c.312_315del (p.Ile105Serfs*4)] and a second rare missense change [c.665T>C (p.Ile222Thr)]. TRMT5 is a nuclear-encoded protein involved in the post-transcriptional maturation of mitochondrial tRNA. Computer modelling of the human TRMT5 protein structure suggests that the rare p.Ile222Thr mutation could affect the stability of tRNA binding.

CONCLUSIONS

Our study expands the phenotype of mitochondrial disorders caused by TRTM5 mutations and defines a new form of recessive demyelinating peripheral neuropathy.

Conservative treatments for feline fibroadenomatous changes of the mammary gland

Background:

Fibroadenomatous changes (FAC) of the mammary gland in cats represents a benign, progesterone-associated fibroglandular proliferation of one or more mammary glands that may occur in intact female cats at the time of puberty, during pregnancy or pseudopregnancy, or in female and male cats of any age under progestin treatment. Nowadays, the elective treatment of FAC is based on the progesterone antagonist aglepristone. This study aimed to report the treatment of FAC with a combination of drugs designed to preserve mammary gland integrity, even in pregnant cats.

Case Description:

Eight sexually intact female cats with FAC showed mammary glands that were symmetrically enlarged and inflamed in all cases, and the skin was ulcerated in six cats. Four cats were on days 25–32 of pregnancy at presentation. Non-pregnant cats were treated with aglepristone and with a dietary supplement containing maltodextrin and bromelain. The mammary glands were massaged daily with an Aloe vera emollient gel. If the gland was inflamed or ulcerated, broad-spectrum antimicrobial, and anti-inflammatory treatments were given, and the ulcers were treated topically with a hypericum and neem-based cream. Two of the four pregnant cats were treated with the same therapeutic schedule plus cloprostenol to facilitate uterine emptying. Two pregnant cats underwent the same protocol except for aglepristone, which was not administered to safeguard the litter and see if the adjuvant therapy worked independently. At term, they delivered four and three kittens, respectively, that were normally nursed and weaned after 40 days. In all the studied cases, the mammary gland reduced in size 2–3 weeks after the start of the treatment and completely remitted after 4–5 weeks.

Conclusion:

This case series encourages adjuvant therapy in the course of FAC to preserve mammary gland integrity and functionality. Exploiting the natural decline of progesterone at the end of pregnancy (or pseudopregnancy), the therapy may also be used without aglepristone, when its use has other limitations.

Pediatric inherited peripheral neuropathy: a prospective study at a Spanish referral center

Background

Single‐center clinical series provide important information on genetic distribution that can guide genetic testing. However, there are few such studies on pediatric populations with inherited peripheral neuropathies (IPNs).

Methods

Thorough genetic testing was performed on IPN patients under 20 years of age from a geographically well‐defined Mediterranean area (Valencian Community, Spain), annually assessed with the Charcot–Marie–Tooth disease Pediatric Scale (CMTPedS).

Results

From 86 families with IPNs, 99 patients (59 males) were identified, 85 with sensorimotor neuropathy or CMT (2/3 demyelinating form) and 14 with distal hereditary motor neuropathy (dHMN). Genetic diagnosis was achieved in 79.5% families, with a similar mutation detection rate in the demyelinating (88.7%) and axonal (89.5%) forms, significantly higher than in the dHMN families (27.3%). CMT1A was the most common subtype, followed by those carrying heterozygous mutations in either the GDAP1 or GJB1 genes. Mutations in 15 other genes were identified, including a new pathogenic variant in the ATP1A gene. The CMTPedS detected significant disease progression in all genetic subtypes of CMT, at a rate of 1.84 (±3.7) over 1 year (p < 0.0005, n = 62) and a 2‐year rate of 3.6 (±4.4: p < 0.0005, n = 45). Significant disease worsening was also detected for CMT1A over 1 (1.7 ± 3.6, p < 0.05) and 2 years (4.2 ± 4.3, p < 0.0005).

Conclusions

This study highlights the unique spectrum of IPN gene frequencies among pediatric patients in this specific geographic region, identifying the CMTPedS as a sensitive tool to detect significant disease worsening over 1 year that could help optimize the design of clinical trials.

Charcot-Marie-Tooth disease due to MORC2 mutations in Spain

BACKGROUND AND PURPOSE

MORC2 mutations have been described as a rare cause of axonal Charcot-Marie-Tooth disease (CMT2Z). The aim of this work was to determine the frequency and distribution of these mutations throughout Spain, to provide a comprehensive phenotypical description and, if possible, to establish a genotype-phenotype correlation.

METHODS

Retrospectively, data on patients diagnosed with CMT2Z in Spain were collected and clinical, electrophysiological and muscle imaging information were analysed.

RESULTS

Fifteen patients with CMT2Z were identified throughout Spain, seven of them belonging to a single kindred, whilst the rest were sporadic. The most common mutation was p.R252W, and four new mutations were identified. Eleven patients were categorized as having a scapuloperoneal phenotype, with asymmetric muscle weakness, early proximal upper limb involvement and frequent spontaneous muscular activity with distal sensory impairment and pes cavus, whilst two presented with a more classic length dependent sensory motor phenotype. This distinction was corroborated by the distribution of muscle fatty infiltration in muscle imaging. Two other patients were classified as having a neurodevelopmental phenotype consisting in congenital or early onset, delay in motor milestones, and global developmental delay in one of them. Nerve conduction studies revealed an unequivocally axonal neuropathy with frequent spontaneous activity, and serum creatine kinase levels were increased in 50% of the patients.

CONCLUSIONS

MORC2 mutations are a rare cause of CMT in Spain, but in-depth phenotyping reveals a recognizable phenotypic spectrum that will be clinically relevant for future identification of this disease.

Mutant PRPF8 Causes Widespread Splicing Changes in Spliceosome Components in Retinitis Pigmentosa Patient iPSC-Derived RPE Cells

Retinitis pigmentosa (RP) is a rare, progressive disease that affects photoreceptors and retinal pigment epithelial (RPE) cells with blindness as a final outcome. Despite high medical and social impact, there is currently no therapeutic options to slow down the progression of or cure the disease. The development of effective therapies was largely hindered by high genetic heterogeneity, inaccessible disease tissue, and unfaithful model organisms. The fact that components of ubiquitously expressed splicing factors lead to the retina-specific disease is an additional intriguing question. Herein, we sought to correlate the retinal cell-type-specific disease phenotype with the splicing profile shown by a patient with autosomal recessive RP, caused by a mutation in pre-mRNA splicing factor 8 (PRPF8). In order to get insight into the role of PRPF8 in homeostasis and disease, we capitalize on the ability to generate patient-specific RPE cells and reveal differentially expressed genes unique to RPE cells. We found that spliceosomal complex and ribosomal functions are crucial in determining cell-type specificity through differential expression and alternative splicing (AS) and that PRPF8 mutation causes global changes in splice site selection and exon inclusion that particularly affect genes involved in these cellular functions. This finding corroborates the hypothesis that retinal tissue identity is conferred by a specific splicing program and identifies retinal AS events as a framework toward the design of novel therapeutic opportunities.

Expanding the β-III Spectrin-Associated Phenotypes toward Non-Progressive Congenital Ataxias with Neurodegeneration

(1) Background: A non-progressive congenital ataxia (NPCA) phenotype caused by β-III spectrin (SPTBN2) mutations has emerged, mimicking spinocerebellar ataxia, autosomal recessive type 14 (SCAR14). The pattern of inheritance, however, resembles that of autosomal dominant classical spinocerebellar ataxia type 5 (SCA5). (2) Methods: In-depth phenotyping of two boys studied by a customized gene panel. Candidate variants were sought by structural modeling and protein expression. An extensive review of the literature was conducted in order to better characterize the SPTBN2-associated NPCA. (3) Results: Patients exhibited an NPCA with hypotonia, developmental delay, cerebellar syndrome, and cognitive deficits. Both probands presented with progressive global cerebellar volume loss in consecutive cerebral magnetic resonance imaging studies, characterized by decreasing midsagittal vermis relative diameter measurements. Cortical hyperintensities were observed on fluid-attenuated inversion recovery (FLAIR) images, suggesting a neurodegenerative process. Each patient carried a novel de novo SPTBN2 substitution: c.193A > G (p.K65E) or c.764A > G (p.D255G). Modeling and protein expression revealed that both mutations might be deleterious. (4) Conclusions: The reported findings contribute to a better understanding of the SPTBN2-associated phenotype. The mutations may preclude proper structural organization of the actin spectrin-based membrane skeleton, which, in turn, is responsible for the underlying disease mechanism.

Distal hereditary motor neuropathies: Mutation spectrum and genotype-phenotype correlation

BACKGROUND AND PURPOSE

Distal hereditary motor neuropathies (dHMNs) are a heterogeneous group of disorders characterized by degeneration of the motor component of peripheral nerves. Currently, only 15% to 32.5% of patients with dHMN are characterized genetically. Additionally, the prevalence of these genetic disorders is not well known. Recently, biallelic mutations in the sorbitol dehydrogenase gene (SORD) have been identified as a cause of dHMN, with an estimated frequency in undiagnosed cases of up to 10%.

METHODS

In the present study, we included 163 patients belonging to 108 different families who were diagnosed with a dHMN and who underwent a thorough genetic screening that included next-generation sequencing and subsequent Sanger sequencing of SORD.

RESULTS

Most probands were sporadic cases (62.3%), and the most frequent age of onset of symptoms was 2 to 10 years (28.8%). A genetic diagnosis was achieved in 37/108 (34.2%) families and 78/163 (47.8%) of all patients. The most frequent cause of distal hereditary motor neuropathies were mutations in HSPB1 (10.4%), GARS1 (9.8%), BICD2 (8.0%), and DNAJB2 (6.7%) genes. In addition, 3.1% of patients were found to be carriers of biallelic mutations in SORD. Mutations in another seven genes were also identified, although they were much less frequent. Eight new pathogenic mutations were detected, and 17 patients without a definite genetic diagnosis carried variants of uncertain significance. The calculated minimum prevalence of dHMN was 2.3 per 100,000 individuals.

CONCLUSIONS

This study confirms the genetic heterogeneity of dHMN and that biallelic SORD mutations are a cause of dHMN in different populations.

Bi-allelic mutations in EGR2 cause autosomal recessive demyelinating neuropathy by disrupting the EGR2-NAB complex

BACKGROUND AND PURPOSE

Mutations in the early growth response 2 gene (EGR2) cause demyelinating, but also axonal, neuropathies differing in severity and age of onset. Except for one family, all reported cases have autosomal dominant inheritance and mutations are localized within the three zinc finger (ZNF) DNA-binding domain. The aim of this study was to provide a clinical and molecular analysis of a novel recessive mutation in EGR2.

METHODS

Clinical and electrophysiological assessments of three affected patients, from a consanguineous family, were performed. Genetic analyses of EGR2 were carried out by Sanger sequencing. Functional effects of clinical recessive mutations were assessed using a mammalian two-hybrid assay.

RESULTS

A novel missense mutation (c.791C>T; p.P264L) in the homozygous state was detected outside the ZNF domains of the EGR2 gene. Three affected siblings presented with distal demyelinating polyneuropathy with severe sensory loss, progressive thoracolumbar scoliosis and trigeminal neuralgia. Respiratory compromise and cranial nerve dysfunction were also found. Our data indicate that the p.P264L mutation prevents interaction of EGR2 transcription factor with NAB corepressors, suggesting that a disruption of the NAB-EGR2 protein interactions can result in dramatic neuropathy.

CONCLUSION

Mutations in, or next to, the R1 domain of EGR2 should be considered with extreme caution for genetic counseling, since these could cause a severe neuropathy with an autosomal recessive manner of transmission.

Impaired proteasome activity and neurodegeneration with brain iron accumulation in FBXO7 defect

FBXO7 is implicated in the ubiquitin-proteasome system and parkin-mediated mitophagy. FBXO7defects cause a levodopa-responsive parkinsonian-pyramidal syndrome(PPS).

METHODS

We investigated the disease molecular bases in a child with PPS and brain iron accumulation.

RESULTS

A novel homozygous c.368C>G (p.S123*) FBXO7 mutation was identified in a child with spastic paraplegia, epilepsy, cerebellar degeneration, levodopa nonresponsive parkinsonism, and brain iron deposition. Patient's fibroblasts assays demonstrated an absence of FBXO7 RNA expression leading to impaired proteasome degradation and accumulation of poly-ubiquitinated proteins.

CONCLUSION

This novel FBXO7 phenotype associated with impaired proteasome activity overlaps with neurodegeneration with brain iron accumulation disorders.

Genetics of Wilson disease and Wilson-like phenotype in a clinical series from eastern Spain

Wilson's disease (WD) is an autosomal recessive disorder caused by ATP7B mutations. Subjects with only one mutation may show clinical signs and individuals with biallelic changes may remain asymptomatic. We aimed to achieve a conclusive genetic diagnosis for 34 patients clinically diagnosed of WD. Genetic analysis comprised from analysis of exons to WES (whole exome sequencing), including promoter, introns, UTRs (untranslated regions), besides of study of large deletions/duplications by MLPA (multiplex ligation-dependent probe amplification). Biallelic ATP7B mutations were identified in 30 patients, so that four patients were analyzed using WES. Two affected siblings resulted to be compound heterozygous for mutations in CCDC115, which is involved in a form of congenital disorder of glycosylation. In sum, the majority of patients with a WD phenotype carry ATP7B mutations. However, if genetic diagnosis is not achieved, additional genes should be considered because other disorders may mimic WD.

Characterization of molecular mechanisms underlying the axonal Charcot-Marie-Tooth neuropathy caused by MORC2 mutations

Mutations in MORC2 lead to an axonal form of Charcot-Marie-Tooth (CMT) neuropathy type 2Z. To date, 31 families have been described with mutations in MORC2, indicating that this gene is frequently involved in axonal CMT cases. While the genetic data clearly establish the causative role of MORC2 in CMT2Z, the impact of its mutations on neuronal biology and their phenotypic consequences in patients remains to be clarified. We show that the full-length form of MORC2 is highly expressed in both embryonic and adult human neural tissues and that Morc2 expression is dynamically regulated in both the developing and the maturing murine nervous system. To determine the effect of the most common MORC2 mutations, p.S87L and p.R252W, we used several in vitro cell culture paradigms. Both mutations induced transcriptional changes in patient-derived fibroblasts and when expressed in rodent sensory neurons. These changes were more pronounced and accompanied by abnormal axonal morphology, in neurons expressing the MORC2 p.S87L mutation, which is associated with a more severe clinical phenotype. These data provide insight into the neuronal specificity of the mutated MORC2-mediated phenotype and highlight the importance of neuronal cell models to study the pathophysiology of CMT2Z.

A very mild phenotype of Charcot-Marie-Tooth disease type 4H caused by two novel mutations in FGD4

BACKGROUND

Mutations in the FGD4 gene cause an autosomal recessive demyelinating peripheral neuropathy referred to as CMT4H, characterized by its onset in infancy or early-childhood and its slow progression.

METHODS

The clinical and genetic status of two patients with CMT4H was studied, performing genetic testing with a panel of genes and analysing FGD4 mRNA expression by quantitative PCR.

RESULTS

Two novel FGD4 variants (c.514delG and c.2211dupA) were identified in two mildly affected Spanish siblings with CMT4H, and with disease onset in late adolescence/adulthood (one of them remaining asymptomatic at 20). On examination, foot deformity was observed without weakness or sensory involvement, and in the muscles of the lower extremities magnetic resonance imaging showed no fat replacement. Further analysis of FGD4 expression in peripheral blood suggested that neither mutation affected splicing, nor did they affect the dosage of FGD4 mRNA (compared to a healthy control). It was predicted that each allele would produce a truncated protein, p.Ala172Glnfs*28 (c.514delG) and p.Ala738Serfs*5 (c.2211dupA), the latter containing all the functional domains of the native protein.

CONCLUSIONS

The conservation of functional domains in the proteins produced from the FGD4 gene of two patients with CMT4H, could explain both the milder phenotype and the later disease onset in these patients. These results expand the clinical and mutational spectrum of FGD4-related peripheral neuropathies.

Characterising the phenotype and mode of inheritance of patients with inherited peripheral neuropathies carrying MME mutations

Background

Mutations in the metalloendopeptidase (MME) gene were initially identified as a cause of autosomal recessive Charcot-Marie-Tooth disease type 2 (CMT2). Subsequently, variants in MME were linked to other late-onset autosomal dominant polyneuropathies. Thus, our goal was to define the phenotype and mode of inheritance of patients carrying changes in MME.

Methods

We screened 197 index cases with a hereditary neuropathy of the CMT type or distal hereditary motor neuropathy (dHMN) and 10 probands with familial amyotrophic lateral sclerosis (fALS) using a custom panel of 119 genes. In addition to the index case subjects, we also studied other clinically and/or genetically affected and unaffected family members.

Results

We found 17 variants in MME in a total of 20 index cases, with biallelic MME mutations detected in 13 cases from nine families (three in homozygosis and six in compound heterozygosis) and heterozygous variants found in 11 families. All patients with biallelic variants had a similar phenotype, consistent with late-onset axonal neuropathy. Conversely, the phenotype of patients carrying heterozygous mutations was highly variable [CMT type 1 (CMT1), CMT2, dHMN and fALS] and mutations did not segregate with the disease.

Conclusion

MME mutations that segregate in an autosomal recessive pattern are associated with a late-onset CMT2 phenotype, yet we could not demonstrate that MME variants in heterozygosis cause neuropathy. Our data highlight the importance of establishing an accurate genetic diagnosis in patients carrying MME mutations, especially with a view to genetic counselling.

PLA2G6-associated neurodegeneration: New insights into brain abnormalities and disease progression

INTRODUCTION

PLA2G6-associated neurodegeneration (PLAN) comprises a continuum of three phenotypes with overlapping clinical and radiologic features.

METHODS

Observational clinical study in a cohort of infantile and childhood onset PLAN patients and genetic analysis of the PLA2G6 gene. We analysed chronological evolution in terms of age at onset and disease course through a 66-item questionnaire. We performed qualitative and quantitative assessment of MRI abnormalities and searched for clinical and radiological phenotype and genotype correlations.

RESULTS

Sixteen PLAN patients (mean age: 10.2 years, range 3-33) were evaluated, with a median onset (years) of signs/symptoms as follows: neurological regression (1.5), oculomotor abnormalities (1.5), hypotonia (1.8), gait loss (2.2), pyramidal signs (3.0), axonal neuropathy (3.0), dysphagia (4.0), optic atrophy (4.0), psychiatric symptoms (4.0), seizures (5.9), joint contractures (6.0), dystonia (8.0), bladder dysfunction (13.0) and parkinsonism (15.0). MRI assessment identified cerebellar atrophy (19/19), brain iron deposition (10/19), clava hypertrophy (8/19) and T2/FLAIR hyperintensity of the cerebellar cortex (6/19). The mid-sagittal vermis relative diameter (MVRD) correlated with age at onset of clinical variants, meaning that the earlier the onset, the more severe the cerebellar atrophy. All patients harboured missense, nonsense and frameshift mutations in PLA2G6, including four novel variants.

CONCLUSIONS

Cerebellar atrophy was a universal radiological sign in infantile and childhood onset PLAN, and correlated with the severity of the phenotype. Iron accumulation within the globus pallidum and substantia nigra was also a common and strikingly uniform feature regardless of the phenotype.

Substrate interaction defects in histidyl-tRNA synthetase linked to dominant axonal peripheral neuropathy

Histidyl-tRNA synthetase (HARS) ligates histidine to cognate tRNA molecules, which is required for protein translation. Mutations in HARS cause the dominant axonal peripheral neuropathy Charcot-Marie-Tooth disease type 2W (CMT2W); however, the precise molecular mechanism remains undefined. Here, we investigated three HARS missense mutations associated with CMT2W (p.Tyr330Cys, p.Ser356Asn, and p.Val155Gly). The three mutations localize to the HARS catalytic domain and failed to complement deletion of the yeast ortholog (HTS1). Enzyme kinetics, differential scanning fluorimetry (DSF), and analytical ultracentrifugation (AUC) were employed to assess the effect of these substitutions on primary aminoacylation function and overall dimeric structure. Notably, the p.Tyr330Cys, p.Ser356Asn, and p.Val155Gly HARS substitutions all led to reduced aminoacylation, providing a direct connection between CMT2W-linked HARS mutations and loss of canonical ARS function. While DSF assays revealed that only one of the variants (p.Val155Gly) was less thermally stable relative to wild-type, all three HARS mutants formed stable dimers, as measured by AUC. Our work represents the first biochemical analysis of CMT-associated HARS mutations and underscores how loss of the primary aminoacylation function can contribute to disease pathology.

On the complexity of clinical and molecular bases of neurodegeneration with brain iron accumulation

Neurodegeneration with brain iron accumulation (NBIA) is a group of inherited heterogeneous neurodegenerative rare disorders. These patients present with dystonia, spasticity, parkinsonism and neuropsychiatric disturbances, along with brain magnetic resonance imaging (MRI) evidence of iron accumulation. In sum, they are devastating disorders and to date, there is no specific treatment. Ten NBIA genes are accepted: PANK2, PLA2G6, C19orf12, COASY, FA2H, ATP13A2, WDR45, FTL, CP, and DCAF17; and nonetheless, a relevant percentage of patients remain without genetic diagnosis, suggesting that other novel NBIA genes remain to be discovered. Overlapping complex clinical pictures render an accurate differential diagnosis difficult. Little is known about the pathophysiology of NBIAs. The reported NBIA genes take part in a variety of pathways: CoA synthesis, lipid and iron metabolism, autophagy, and membrane remodeling. The next-generation sequencing revolution has achieved relevant advances in genetics of Mendelian diseases and provide new genes for NBIAs, which are investigated according to 2 main strategies: genes involved in disorders with similar phenotype and genes that play a role in a pathway of interest. To achieve an effective therapy for NBIA patients, a better understanding of the biological process underlying disease is crucial, moving toward a new age of precision medicine.

Clinical rating scale for pantothenate kinase-associated neurodegeneration: A pilot study

BACKGROUND

Pantothenate kinase-associated neurodegeneration is a progressive neurological disorder occurring in both childhood and adulthood. The objective of this study was to design and pilot-test a disease-specific clinical rating scale for the assessment of patients with pantothenate kinase-associated neurodegeneration.

METHODS

In this international cross-sectional study, patients were examined at the referral centers following a standardized protocol. The motor examination was filmed, allowing 3 independent specialists in movement disorders to analyze 28 patients for interrater reliability assessment. The scale included 34 items (maximal score, 135) encompassing 6 subscales for cognition, behavior, disability, parkinsonism, dystonia, and other neurological signs.

RESULTS

Forty-seven genetically confirmed patients (30 ± 17 years; range, 6-77 years) were examined with the scale (mean score, 62 ± 21; range, 20-106). Dystonia with prominent cranial involvement and atypical parkinsonian features were present in all patients. Other common signs were cognitive impairment, psychiatric features, and slow and hypometric saccades. Dystonia, parkinsonism, and other neurological features had a moderate to strong correlation with disability. The scale showed good internal consistency for the total scale (Cronbach's α = 0.87). On interrater analysis, weighted kappa values (0.30-0.93) showed substantial or excellent agreement in 85% of the items. The scale also discriminated a subgroup of homozygous c.1583C>T patients with lower scores, supporting construct validity for the scale.

CONCLUSIONS

The proposed scale seems to be a reliable and valid instrument for the assessment of pediatric and adult patients with pantothenate kinase-associated neurodegeneration. Additional validation studies with a larger sample size will be required to confirm the present results and to complete the scale validation testing. © 2017 International Parkinson and Movement Disorder Society.

Distribution and genotype-phenotype correlation of GDAP1 mutations in Spain

Mutations in the GDAP1 gene can cause Charcot-Marie-Tooth disease. These mutations are quite rare in most Western countries but not so in certain regions of Spain or other Mediterranean countries. This cross-sectional retrospective multicenter study analyzed the clinical and genetic characteristics of patients with GDAP1 mutations across Spain. 99 patients were identified, which were distributed across most of Spain, but especially in the Northwest and Mediterranean regions. The most common genotypes were p.R120W (in 81% of patients with autosomal dominant inheritance) and p.Q163X (in 73% of autosomal recessive patients). Patients with recessively inherited mutations had a more severe phenotype, and certain clinical features, like dysphonia or respiratory dysfunction, were exclusively detected in this group. Dominantly inherited mutations had prominent clinical variability regarding severity, including 29% of patients who were asymptomatic. There were minor clinical differences between patients harboring specific mutations but not when grouped according to localization or type of mutation. This is the largest clinical series to date of patients with GDAP1 mutations, and it contributes to define the genetic distribution and genotype-phenotype correlation in this rare form of CMT.

Molecular and functional characterization of the BMPR2 gene in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension is a progressive disease that causes the obstruction of precapillary pulmonary arteries and a sustained increase in pulmonary vascular resistance. The aim was to analyze functionally the variants found in the BMPR2 gene and to establish a genotype-phenotype correlation. mRNA expression studies were performed using pSPL3 vector, studies of subcellular localization were performed using pEGFP-N1 vector and luciferase assays were performed using pGL3-Basic vector. We have identified 30 variants in the BMPR2 gene in 27 of 55 patients. In 16 patients we detected pathogenic mutations. Minigene assays revealed that 6 variants (synonymous, missense) result in splicing defect. By immunofluorescence assay, we observed that 4 mutations affect the protein localization. Finally, 4 mutations located in the 5'UTR region showed a decreased transcriptional activity in luciferase assays. Genotype-phenotype correlation, revealed that patients with pathogenic mutations have a more severe phenotype (sPaP p = 0.042, 6MWT p = 0.041), a lower age at diagnosis (p = 0.040) and seemed to have worse response to phosphodiesterase-5-inhibitors (p = 0.010). Our study confirms that in vitro expression analysis is a suitable approach in order to investigate the phenotypic consequences of the nucleotide variants, especially in cases where the involved genes have a pattern of expression in tissues of difficult access.

Chaperonopathies: Spotlight on Hereditary Motor Neuropathies

Distal hereditary motor neuropathies (dHMN) are a group of rare hereditary neuromuscular disorders characterized by an atrophy that affects peroneal muscles in the absence of sensory symptoms. To date, 23 genes are thought to be responsible for dHMN, four of which encode chaperones: DNAJB2, which encodes a member of the HSP40/DNAJ co-chaperone family; and HSPB1, HSPB3, and HSPB8, encoding three members of the small heat shock protein family. While around 30 different mutations in HSPB1 have been identified, the remaining three genes are altered in many fewer cases. Indeed, a mutation of HSPB3 has only been described in one case, whereas a few cases have been reported carrying mutations in DNAJB2 and HSPB8, most of them caused by a founder c.352+1G>A mutation in DNAJB2 and by mutations affecting the K141 residue in the HSPB8 chaperone. Hence, their rare occurrence makes it difficult to understand the pathological mechanisms driven by such mutations in this neuropathy. Chaperones can assemble into multi-chaperone complexes that form an integrated chaperone network within the cell. Such complexes fulfill relevant roles in a variety of processes, such as the correct folding of newly synthesized proteins, in which chaperones escort them to precise cellular locations, and as a response to protein misfolding, which includes the degradation of proteins that fail to refold properly. Despite this range of functions, mutations in some of these chaperones lead to diseases with a similar clinical profile, suggesting common pathways. This review provides an overview of the genetics of those dHMNs that share a common disease mechanism and that are caused by mutations in four genes encoding chaperones: DNAJB2, HSPB1, HSPB3, and HSPB8.

Mutations in the MORC2 gene cause axonal Charcot-Marie-Tooth disease

Charcot-Marie-Tooth disease (CMT) is a complex disorder with wide genetic heterogeneity. Here we present a new axonal Charcot-Marie-Tooth disease form, associated with the gene microrchidia family CW-type zinc finger 2 (MORC2). Whole-exome sequencing in a family with autosomal dominant segregation identified the novel MORC2 p.R190W change in four patients. Further mutational screening in our axonal Charcot-Marie-Tooth disease clinical series detected two additional sporadic cases, one patient who also carried the same MORC2 p.R190W mutation and another patient that harboured a MORC2 p.S25L mutation. Genetic and in silico studies strongly supported the pathogenicity of these sequence variants. The phenotype was variable and included patients with congenital or infantile onset, as well as others whose symptoms started in the second decade. The patients with early onset developed a spinal muscular atrophy-like picture, whereas in the later onset cases, the initial symptoms were cramps, distal weakness and sensory impairment. Weakness and atrophy progressed in a random and asymmetric fashion and involved limb girdle muscles, leading to a severe incapacity in adulthood. Sensory loss was always prominent and proportional to disease severity. Electrophysiological studies were consistent with an asymmetric axonal motor and sensory neuropathy, while fasciculations and myokymia were recorded rather frequently by needle electromyography. Sural nerve biopsy revealed pronounced multifocal depletion of myelinated fibres with some regenerative clusters and occasional small onion bulbs. Morc2 is expressed in both axons and Schwann cells of mouse peripheral nerve. Different roles in biological processes have been described for MORC2. As the silencing of Charcot-Marie-Tooth disease genes have been associated with DNA damage response, it is tempting to speculate that a deregulation of this pathway may be linked to the axonal degeneration observed in MORC2 neuropathy, thus adding a new pathogenic mechanism to the long list of causes of Charcot-Marie-Tooth disease.

Complexity of the Hereditary Motor and Sensory Neuropathies: Clinical and Cellular Characterization of the MPZ p.D90E Mutation

Early-onset hereditary motor and sensory neuropathies are rare diseases representing a broad clinical and genetic spectrum. Without a notable familial history, the clinical diagnosis is complicated because acquired causes of peripheral neuropathy, such as inflammatory neuropathies, neuropathies with toxic causes, and nutritional deficiencies, must be considered. We examined the clinical, electrophysiological, and pathologic manifestations of a boy with an initial diagnosis of chronic inflammatory demyelinating polyneuropathy. The progression of the disease despite treatment led to a suspicion of hereditary motor and sensory neuropathy. Genetic testing revealed the presence of the MPZ p.D90E mutation in heterozygosis. To clarify the pathogenicity of this mutation and achieve a conclusive diagnosis, we investigated the MPZ p.D90E mutation through in silico and cellular approaches. This study broadens the clinical phenotype of hereditary motor and sensory neuropathy due to MPZ mutation and emphasises the difficulty of achieving an accurate genetic diagnosis in a sporadic patient to provide an appropriate pharmacologic treatment.

Junctophilin-1 is a modifier gene of GDAP1-related Charcot-Marie-Tooth disease

Mutations in the GDAP1 gene cause different forms of Charcot-Marie-Tooth (CMT) disease, and the primary clinical expression of this disease is markedly variable in the dominant inheritance form (CMT type 2K; CMT2K), in which carriers of the GDAP1 p.R120W mutation can display a wide range of clinical severity. We investigated the JPH1 gene as a genetic modifier of clinical expression variability because junctophilin-1 (JPH1) is a good positional and functional candidate. We demonstrated that the JPH1-GDAP1 cluster forms a paralogon and is conserved in vertebrates. Moreover, both proteins play a role in Ca(2+) homeostasis, and we demonstrated that JPH1 is able to restore the store-operated Ca(2+) entry (SOCE) activity in GDAP1-silenced cells. After the mutational screening of JPH1 in a series of 24 CMT2K subjects who harbour the GDAP1 p.R120W mutation, we characterized the JPH1 p.R213P mutation in one patient with a more severe clinical picture. JPH1(p.R213P) cannot rescue the SOCE response in GDAP1-silenced cells. We observed that JPH1 colocalizes with STIM1, which is the activator of SOCE, in endoplasmic reticulum-plasma membrane puncta structures during Ca(2+) release in a GDAP1-dependent manner. However, when GDAP1(p.R120W) is expressed, JPH1 seems to be retained in mitochondria. We also established that the combination of GDAP1(p.R120W) and JPH1(p.R213P) dramatically reduces SOCE activity, mimicking the effect observed in GDAP1 knock-down cells. In summary, we conclude that JPH1 and GDAP1 share a common pathway and depend on each other; therefore, JPH1 can contribute to the phenotypical consequences of GDAP1 mutations.

Sh3tc2 deficiency affects neuregulin-1/ErbB signaling

Mutations in SH3TC2 trigger autosomal recessive demyelinating Charcot-Marie-Tooth type 4C (CMT4C) neuropathy. Sh3tc2 is specifically expressed in Schwann cells and is necessary for proper myelination of peripheral axons. In line with the early onset of neuropathy observed in patients with CMT4C, our analyses of the murine model of CMT4C revealed that the myelinating properties of Sh3tc2-deficient Schwann cells are affected at an early stage. This early phenotype is associated with changes in the canonical Nrg1/ErbB pathway involved in control of myelination. We demonstrated that Sh3tc2 interacts with ErbB2 and plays a role in the regulation of ErbB2 intracellular trafficking from the plasma membrane upon Nrg1 activation. Interestingly, both the loss of Sh3tc2 function in mice and the pathological mutations present in CMT4C patients affect ErbB2 internalization, potentially altering its downstream intracellular signaling pathways. Altogether, our results indicate that the molecular mechanism for the axonal size sensing is disturbed in Sh3tc2-deficient myelinating Schwann cells, thus providing a novel insight into the pathophysiology of CMT4C neuropathy.

Missense mutations in the SH3TC2 protein causing Charcot-Marie-Tooth disease type 4C affect its localization in the plasma membrane and endocytic pathway

Mutations in SH3TC2 (KIAA1985) cause Charcot-Marie-Tooth disease (CMT) type 4C, a demyelinating inherited neuropathy characterized by early-onset and scoliosis. Here we demonstrate that the SH3TC2 protein is present in several components of the endocytic pathway including early endosomes, late endosomes and clathrin-coated vesicles close to the trans-Golgi network and in the plasma membrane. Myristoylation of SH3TC2 in glycine 2 is necessary but not sufficient for the proper location of the protein in the cell membranes. In addition to myristoylation, correct anchoring also needs the presence of SH3 and TPR domains. Mutations that cause a stop codon and produce premature truncations that remove most of the TPR domains are expressed as the wild-type protein. In contrast, missense mutations in or around the region of the first-TPR domain are absent from early endosomes, reduced in plasma membrane and late endosomes and are variably present in clathrin-coated vesicles. Our findings suggest that the endocytic and membrane trafficking pathway is involved in the pathogenesis of CMT4C disease. We postulate that missense mutations of SH3TC2 could impair communication between the Schwann cell and the axon causing an abnormal myelin formation.

A novel delins mutation in the alpha-TTP gene in a family segregating ataxia with isolated vitamin E deficiency

Ataxia with isolated vitamin E deficiency is a rare autosomal recessive neurodegenerative disease due to mutations in the alpha-tocopherol transfer protein gene. In ataxia with isolated vitamin E deficiency, the biochemical hallmark is the low plasmatic levels of vitamin E and, in most of the patients, vitamin E supplementation allows a stabilization of the neurologic conditions. We have investigated the genetic cause of ataxia and reduced levels of vitamin E, and apolipoproteins A1 and B in a 16-y-old patient. Results revealed that our propositus is a compound heterozygote for the c.227_229delinsATT/c.744delA mutations in the alpha-tocopherol transfer protein gene, each inherited from one of the two parents. His sister is also a compound heterozygote for both mutations, and she presents a biochemical pattern similar to that of his brother. After receiving the vitamin E supplementation, plasmatic levels of vitamin E and apolipoprotein A1 have been normalized in the propositus. The detected mutations would justify the undetectable levels of vitamin E, but would not explain the also decreased levels of the apolipoproteins, as neither that after treatment with vitamin E, the levels of apolipoprotein B do not become normal. These findings suggest that other genes may play a role in producing this atypical biochemical profile.

The p.R1109X mutation in SH3TC2 gene is predominant in Spanish Gypsies with Charcot-Marie-Tooth disease type 4

Charcot-Marie-Tooth (CMT) disease type 4 (CMT4) is the name given to autosomal recessive forms of hereditary motor and sensory neuropathy (HMSN). When we began this study, three genes or loci associated with inherited peripheral neuropathies had already been identified in the European Gypsy population: HMSN-Lom (MIM 601455), HMSN-Russe (MIM 605285) and the congenital cataracts facial dysmorphism neuropathy syndrome (MIM 604168). We have carried out genetic analyses in a series of 20 Spanish Gypsy families diagnosed with a demyelinating CMT disease compatible with an autosomal recessive trait. We found the p.R148X mutation in the N-myc downstream-regulated gene 1 gene to be responsible for the HMSN-Lom in four families and also possible linkage to the HMSN-Russe locus in three others. We have also studied the CMT4C locus because of the clinical similarities and showed that in 10 families, the disease is caused by mutations located on the SH3 domain and tetratricopeptide repeats 2 (SH3TC2) gene: p.R1109X in 20 out of 21 chromosomes and p.C737_P738delinsX in only one chromosome. Moreover, the SH3TC2 p.R1109X mutation is associated with a conserved haplotype and, therefore, may be a private founder mutation for the Gypsy population. Estimation of the allelic age revealed that the SH3TC2 p.R1109X mutation may have arisen about 225 years ago, probably as the consequence of a bottleneck.

Project LID (lower infant deaths). Lessons learned from a local infant mortality review project

Project LID (Lower Infant Deaths) is an infant mortality review project conducted by the Minneapolis Department of Health and Family Support and the Saint Paul-Ramsey County Department of Public Health. Infant death occurs when a live-born infant dies before age 1. Multidisciplinary teams reviewed 112 infant-mother cases involving infant death using vital and medical records. Open-ended maternal interviews were conducted for approximately half of the cases. This combination of quantitative and qualitative data provided insights into the contributing social, medical, and environmental factors experienced by some families in Hennepin and Ramsey counties. Case review teams developed recommendations to address factors identified in each case. Recommendations are directed to health care providers, professional societies, health systems, government organizations, policymakers, and community- and school-based organizations. This article describes findings from the project and presents recommendations for Minnesota physicians with practices in obstetrics, family medicine, and pediatrics.

[Microsurgery of the renal arteries]

The extracorporal microsurgery of renal artery branches has improved the therapeutic possibilities of complicated vascular abnormalities. Intrarenal stenoses can only be treated by this technique and excellent therapeutic conditions are rendered possible, if more than two artery branches have to be replaced. The technical results are satisfactory, if the quality of the renal parenchyma is considered, which has been abnormal in a number of cases at the moment of the surgical treatment. The results concerning the arterial hypertension and the renal function are remarkable, when considering the fact that most of the kidneys treated by this technique would have been removed some years ago.