Dysregulated iron homeostasis in dystrophin-deficient cardiomyocytes: correction by gene editing and pharmacological treatment

AIMS

Duchenne muscular dystrophy (DMD)-associated cardiomyopathy is a serious life-threatening complication, the mechanisms of which have not been fully established, and therefore no effective treatment is currently available. The purpose of the study was to identify new molecular signatures of the cardiomyopathy development in DMD.

METHODS AND RESULTS

For modelling of DMD-associated cardiomyopathy, we prepared three pairs of isogenic control and dystrophin-deficient human induced pluripotent stem cell (hiPSC) lines. Two isogenic hiPSC lines were obtained by CRISPR/Cas9-mediated deletion of DMD exon 50 in unaffected cells generated from healthy donor and then differentiated into cardiomyocytes (hiPSC-CM). The latter were subjected to global transcriptomic and proteomic analyses followed by more in-depth investigation of selected pathway and pharmacological modulation of observed defects. Proteomic analysis indicated a decrease in the level of mitoNEET protein in dystrophin-deficient hiPSC-CM, suggesting alteration in iron metabolism. Further experiments demonstrated increased labile iron pool both in the cytoplasm and mitochondria, a decrease in ferroportin level and an increase in both ferritin and transferrin receptor in DMD hiPSC-CM. Importantly, CRISPR/Cas9-mediated correction of the mutation in the patient-derived hiPSC reversed the observed changes in iron metabolism and restored normal iron levels in cardiomyocytes. Moreover, treatment of DMD hiPSC-CM with deferoxamine (DFO, iron chelator) or pioglitazone (mitoNEET stabilizing compound) decreased the level of reactive oxygen species in DMD hiPSC-CM.

CONCLUSION

To our knowledge, this study demonstrated for the first time impaired iron metabolism in human DMD cardiomyocytes, and potential reversal of this effect by correction of DMD mutation or pharmacological treatment. This implies that iron overload-regulating compounds may serve as novel therapeutic agents in DMD-associated cardiomyopathy.

Long-term nusinersen treatment across a wide spectrum of spinal muscular atrophy severity: a real-world experience

BACKGROUND

Spinal muscular atrophy (SMA) is an autosomal recessive disorder caused by a biallelic mutation in the SMN1 gene, resulting in progressive muscle weakness and atrophy. Nusinersen is the first disease-modifying drug for all SMA types. We report on effectiveness and safety data from 120 adults and older children with SMA types 1c-3 treated with nusinersen.

METHODS

Patients were evaluated with the Hammersmith Functional Motor Scale Expanded (HFMSE; n = 73) or the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND; n = 47). Additionally, the Revised Upper Limb Module (RULM) and 6-minute walk test (6MWT) were used in a subset of patients. Patients were followed for up to 30 months of nusinersen treatment (mean, SD; 23, 14 months). Subjective treatment outcomes were evaluated with the Patients Global Impression-Improvement (PGI-I) scale used in all patients or caregivers at each follow-up visit.

RESULTS

An increase in the mean HFMSE score was noted at month 14 (T14) (3.9 points, p < 0.001) and month 30 (T30) (5.1 points, p < 0.001). The mean RULM score increased by 0.79 points at T14 (p = 0.001) and 1.96 points (p < 0.001) at month 30 (T30). The mean CHOP-INTEND increased by 3.6 points at T14 (p < 0.001) and 5.6 points at month 26 (p < 0.001). The mean 6MWT improved by 16.6 m at T14 and 27 m at T30 vs. baseline. A clinically meaningful improvement in HFMSE (≥ 3 points) was seen in 62% of patients at T14, and in 71% at T30; in CHOP INTEND (≥ 4 points), in 58% of patients at T14 and in 80% at T30; in RULM (≥ 2 points), in 26.6% of patients at T14 and in 43.5% at T30; and in 6MWT (≥ 30-meter increase), in 26% of patients at T14 and in 50% at T30. Improved PGI-I scores were reported for 75% of patients at T14 and 85% at T30; none of the patients reporting worsening at T30. Adverse events were mild and related to lumbar puncture.

CONCLUSIONS

In our study, nusinersen led to continuous functional improvement over 30-month follow-up and was well tolerated by adults and older children with a wide spectrum of SMA severity.

Cathepsin B p.Gly284Val Variant in Parkinson's Disease Pathogenesis

Parkinson's disease (PD) is generally considered a sporadic disorder, but a strong genetic background is often found. The aim of this study was to identify the underlying genetic cause of PD in two affected siblings and to subsequently assess the role of mutations in Cathepsin B (CTSB) in susceptibility to PD. A typical PD family was identified and whole-exome sequencing was performed in two affected siblings. Variants of interest were validated using Sanger sequencing. CTSB p.Gly284Val was genotyped in 2077 PD patients and 615 unrelated healthy controls from the Czech Republic, Ireland, Poland, Ukraine, and the USA. The gene burden analysis was conducted for the CTSB gene in an additional 769 PD probands from Mayo Clinic Florida familial PD cohort. CTSB expression and activity in patient-derived fibroblasts and controls were evaluated by qRT-PCR, western blot, immunocytochemistry, and enzymatic assay. The CTSB p.Gly284Val candidate variant was only identified in affected family members. Functional analysis of CTSB patient-derived fibroblasts under basal conditions did not reveal overt changes in endogenous expression, subcellular localization, or enzymatic activity in the heterozygous carrier of the CTSB variant. The identification of the CTSB p.Gly284Val may support the hypothesis that the CTSB locus harbors variants with differing penetrance that can determine the disease risk.

Generation of DMBi002-A human induced pluripotent stem cell line from patient with Spinal muscular atrophy type 3

Spinal Muscular Atrophy (SMA) is a genetic neuromuscular disease caused by mutations inSMN1 gene encoding survival motor neuron (SMN) protein. Lack of this protein leads to progressive loss of motor neurons and therefore to gradual loss of signal transmission between motor neurons and skeletal muscle cells. As a consequence, patients develop muscle atrophy and lose the ability to move independently, what is also related to problems with breathing and swallowing. Here, we describe the generation of human induced pluripotent stem cells (hiPSC) from peripheral blood mononuclear cells (PBMC) of adult SMA type 3 patient with a use of Sendai virus vectors.

Pediatric CIDP: Diagnosis and Management. A Single-Center Experience

Background: Chronic inflammatory demyelinating polyneuropathy (CIDP) is a rare acquired polyneuropathy that especially among youngest children should be differentiated with hereditary neuropathies. Even though upon diagnosis treatment options are similar in children and adults, diagnostic challenges are faced in the pediatric population. Methods: We conducted a retrospective analysis of clinical symptoms, nerve conduction study results, modes of treatment, and final outcome in 37 children aged 3.5-17 years with a final diagnosis of CIDP (18 girls, 19 boys). We established three groups of patients based on age at onset of CIDP: 0-4, 4-13, and 13-18 years. Follow-up ranged from 10 to 222 months. Results: In our analysis, 19/37 patients (51.4%) had an atypical presentation: distal variant of CIDP in 12/37 patients (32.4%) and pure motor variant of CIDP in 5/37 patients (13.5%), and one patient had a pure sensory variant (1/37, 2.7%). Furthermore, 3/37 patients (8.1%) had additional concurring symptoms, including involuntary movements of face muscles (1/37, 2.7%) or hand tremor (2/37, 5.4%). During the follow-up, 23/37 patients (62.2%) received intravenous immunoglobulin (IVIg); 22/37 patients (59.5%) received steroids, 6/37 patients (16.2%) received IVIg and steroids, and 12/37 patients (32.4%) received immunosuppressive drugs, mostly azathioprine, but also methotrexate and rituximab. One patient was treated with plasmapheresis. Complete remission was achieved in 19/37 patients (51.4%) with CIDP in its typical form. Remission with residual symptoms or minimal deficit was observed in 4/37 patients (10.8%), whereas 14/37 patients (37.8%) remain on treatment with gradual improvement. Conclusion: Childhood CIDP may occur in its typical form, but even ~50% of children can present as an atypical variant including distal, pure motor, or pure sensory. Most children have a good prognosis; however, many of them may require long-term treatment. This highlights the importance of an early diagnosis and treatment for childhood CIDP.

Acute Autonomic Neuropathy as a Rare Cause of Severe Arterial Hypertension in a Child

A 7-year-old boy was admitted to the Pediatric Cardiology Department with blood pressure of 160/120 mmHg accompanied by burning pain in his hands and feet and tachycardia, followed by a seizure attack for the first time in his life, which presented shortly after admission. The child underwent a widespread diagnostic process - including laboratory tests and imaging - showing inconclusive results. Acute autonomic neuropathy was eventually diagnosed and successfully treated with intravenous immunoglobulin. The described case illustrates the need for a careful and open-minded approach to patients with hypertension.

Floppy infant syndrome as a first manifestation of LMNA-related congenital muscular dystrophy

LMNA-related congenital muscular dystrophy (L-CMD) is the most severe phenotypic form of skeletal muscle laminopathies. This paper reports clinical presentation of the disease in 15 Polish patients from 13 families with genetically confirmed skeletal muscle laminopathy. In all these patients floppy infant syndrome was the first manifestation of the disease. The genetic diagnosis was established by next generation sequencing (targeted panel or exome; 11 patients) or classic Sanger sequencing (4 patients). In addition to known pathogenic LMNA variants: c.116A > G (p.Asn39Ser), c.745C > T (p.Arg249Trp), c.746G > A (p.Arg249Gln), c.1072G > A (p.Glu358Lys), c.1147G > A (p.Glu383Lys), c.1163G > C (p.Arg388Pro), c.1357C > T (p.Arg453Trp), c.1583C > G (p.Thr528Arg), we have identified three novel ones: c.121C > G (p.Arg41Gly), c.1127A > G (p.Tyr376Cys) and c.1160T > C (p.Leu387Pro). Eleven patients had de novo mutations, 4 - familial. In one family we observed intrafamilial variability of clinical course: severe L-CMD in the male proband, intermediate form in his sister and asymptomatic in their mother. One asymptomatic father had somatic mosaicism. L-CMD should be suspected in children with hypotonia in infancy and delayed motor development, who have poor head control, severe hyperlordosis and unstable and awkward gait. Serum creatine kinase may be high (~1000IU/l). Progression of muscle weakness is fast, leading to early immobilization. In some patients with L-CMD joint contractures can develop with time. MRI shows that the most frequently affected muscles are the serratus anterior, lumbar paraspinal, gluteus, vastus, adductor magnus, hamstrings, medial head of gastrocnemius and soleus. Ultra-rare laminopathies can be a relatively common cause of generalized hypotonia in children. Introduction of wide genome sequencing methods was a breakthrough in diagnostics of diseases with great clinical and genetic variability and allowed approach "from genotype do phenotype". However target sequencing of LMNA gene could be considered in selected patients with clinical picture suggestive for laminopathy.

Frequency of mutations in PRKN, PINK1, and DJ1 in Patients With Early-Onset Parkinson Disease from neighboring countries in Central Europe

INTRODUCTION

Approximately 10% of patients with Parkinson disease (PD) present with early-onset disease (EOPD), defined as diagnosis before 50 years of age. Genetic factors are known to contribute to EOPD, with most commonly observed mutations in PRKN, PINK1, and DJ1 genes. The aim of our study was to analyze the frequency of PRKN, PINK1, and DJ1 mutations in an EOPD series from 4 neighboring European countries: Czech Republic, Germany, Poland, and Ukraine.

METHODS

Diagnosis of PD was made based on UK Brain Bank diagnostic criteria in departments experienced in movement disorders (1 from Czech Republic, 1 from Germany, 9 from Poland, and 3 from Ukraine). EOPD was defined as onset at or before 50 years of age. Of the 541 patients recruited to the study, 11 were Czech, 38 German, 476 Polish, and 16 Ukrainian. All cohorts were fully screened with Sanger sequencing for PRKN, PINK1, and DJ1 and multiplex ligation-dependent probe amplification for exon dosage.

RESULTS

PRKN homozygous or double heterozygous mutations were identified in 17 patients: 1 Czech (9.1%), 1 German (2.6%), 14 Polish (2.9%), and 1 Ukrainian (6.3%). PINK1 homozygous mutations were only identified in 3 Polish patients (0.6%). There were no homozygous or compound heterozygous DJ1 mutations in analyzed subpopulations. One novel variant in PRKN was identified in the Ukrainian series.

CONCLUSION

In the analyzed cohorts, mutations in the genes PRKN, PINK1, and DJ1 are not frequently observed.

Pathogenic Mutations and Putative Phenotype-Affecting Variants in Polish Myofibrillar Myopathy Patients

Myofibrillar myopathies (MFM) are heterogeneous hereditary muscle diseases with characteristic myopathological features of Z-disk dissolution and aggregates of its degradation products. The onset and progression of the disease are variable, with an elusive genetic background, and around half of the cases lacking molecular diagnosis. Here, we attempted to establish possible genetic foundations of MFM by performing whole exome sequencing (WES) in eleven unrelated families of 13 patients clinically diagnosed as MFM spectrum. A filtering strategy aimed at identification of variants related to the disease was used and included integrative analysis of WES data and human phenotype ontology (HPO) terms, analysis of muscle-expressed genes, and analysis of the disease-associated interactome. Genetic diagnosis was possible in eight out of eleven cases. Putative causative mutations were found in the DES (two cases), CRYAB, TPM3, and SELENON (four cases) genes, the latter typically presenting with a rigid spine syndrome. Moreover, a variety of additional, possibly phenotype-affecting variants were found. These findings indicate a markedly heterogeneous genetic background of MFM and show the usefulness of next generation sequencing in the identification of disease-associated mutations. Finally, we discuss the emerging concept of variant load as the basis of phenotypic heterogeneity.

Ethnicity-related DMD Genotype Landscapes in European and Non-European Countries

Objective

Genetic diagnosis and mutation identification are now compulsory for Duchenne (DMD) and Becker muscular dystrophies (BMD), which are due to dystrophin (DMD) gene mutations, either for disease prevention or personalized therapies. To evaluate the ethnic-related genetic assortments of DMD mutations, which may impact on DMD genetic diagnosis pipelines, we studied 328 patients with DMD and BMD from non-European countries.

Methods

We performed a full DMD mutation detection in 328 patients from 10 Eastern European countries (Poland, Hungary, Lithuania, Romania, Serbia, Croatia, Bosnia, Bulgaria, Ukraine, and Russia) and 2 non-European countries (Cyprus and Algeria). We used both conventional methods (multiplex ligation-dependent probe amplification [MLPA] followed by gene-specific sequencing) and whole-exome sequencing (WES) as a pivotal study ran in 28 patients where DMD mutations were already identified by standard techniques. WES output was also interrogated for DMD gene modifiers.

Results

We identified DMD gene mutations in 222 male patients. We identified a remarkable allele heterogeneity among different populations with a mutation landscape often country specific. We also showed that WES is effective for picking up all DMD deletions and small mutations and its adoption could allow a detection rate close to 90% of all occurring mutations. Gene modifiers haplotypes were identified with some ethnic-specific configurations.

Conclusions

Our data provide unreported mutation landscapes in different countries, suggesting that ethnicity may orient genetic diagnosis flowchart, which can be adjusted depending on the mutation type frequency, with impact in drug eligibility.

Lack of miR-378 attenuates muscular dystrophy in mdx mice

The severity of Duchenne muscular dystrophy (DMD), an incurable disease caused by the lack of dystrophin, might be modulated by different factors, including miRNAs. Among them, miR-378 is considered of high importance for muscle biology, but intriguingly, its role in DMD and its murine model (mdx mice) has not been thoroughly addressed so far. Here, we demonstrate that dystrophic mice additionally globally lacking miR-378 (double-KO [dKO] animals) exhibited better physical performance and improved absolute muscle force compared with mdx mice. Accordingly, markers of muscle damage in serum were significantly decreased in dKO mice, accompanied by diminished inflammation, fibrosis, and reduced abundance of regenerating fibers within muscles. The lack of miR-378 also normalized the aggravated fusion of dystrophin-deficient muscle satellite cells (mSCs). RNA sequencing of gastrocnemius muscle transcriptome revealed fibroblast growth factor 1 (Fgf1) as one of the most significantly downregulated genes in mice devoid of miR-378, indicating FGF1 as one of the mediators of changes driven by the lack of miR-378. In conclusion, we suggest that targeting miR-378 has the potential to ameliorate DMD pathology.

Electrophysiological and clinical assessment of dysautonomia in multiple system atrophy (MSA) and progressive supranuclear palsy (PSP): a comparative study

CLINICAL RATIONALE FOR THE STUDY

Autonomic nervous system (ANS) involvement in different parkinsonian syndromes has been frequently discussed. It is well established in multiple system atrophy (MSA), whereas it is less evident in progressive supranuclear palsy (PSP).

AIMS OF THE STUDY

The aims were to assess the presence and pattern of ANS involvement in MSA and PSP using noninvasive tests i.e. the sympathetic skin response (SSR) test and the R-R interval variation (RRIV) test; to analyse the relationship between clinical and electrophysiological abnormalities in both disorders; and to assess whether an autonomic profile might help to differentiate them.

MATERIALS AND METHODS

Clinical and electrophysiological assessments of dysautonomia were performed in 59 patients with MSA (24 cases of MSA-C and 35 cases of MSA-P), these 59 cases including 31 females, mean disease duration 4.2 ± 2.7 years, mean age 60.3 ± 8.4 years, and in 37 patients with PSP (12 females, mean disease duration 4.6 ± 3.6 years, mean age 67.5 ± 6.1 years) and the results were compared to the results obtained from 23 healthy controls matched for age and sex.

RESULTS

Clinical dysautonomia assessed by an Autonomic Symptoms Questionnaire was observed in 97% of the MSA patients and in 84% of the PSP patients. SSR was abnormal in 64% and RRIV was abnormal in 73% of MSA cases. In PSP cases, these figures were 78% and 81% respectively. Dysautonomia was clinically more pronounced in MSA compared to PSP (p < 0.05), whereas electrophysiological testing revealed frequently subclinical ANS damage in PSP patients.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Our results point to the complementary role of electrophysiological tests in the diagnostic work-up of dysautonomia in parkinsonian syndromes.

Whole-exome sequencing identifies novel pathogenic mutations and putative phenotype-influencing variants in Polish limb-girdle muscular dystrophy patients

Background

Limb girdle muscular dystrophies (LGMD) are a group of heterogeneous hereditary myopathies with similar clinical symptoms. Disease onset and progression are highly variable, with an elusive genetic background, and around 50% cases lacking molecular diagnosis.

Methods

Whole exome sequencing (WES) was performed in 73 patients with clinically diagnosed LGMD. A filtering strategy aimed at identification of variants related to the disease included integrative analysis of WES data and human phenotype ontology (HPO) terms, analysis of genes expressed in muscle, analysis of the disease-associated interactome and copy number variants analysis.

Results

Genetic diagnosis was possible in 68.5% of cases. On average, 36.3 rare variants in genes associated with various muscle diseases per patient were found that could relate to the clinical phenotype. The putative causative mutations were mostly in LGMD-associated genes, but also in genes not included in the current LGMD classification (DMD, COL6A2, and COL6A3). In three patients, mutations in two genes were suggested as the joint cause of the disease (CAPN3+MYH7, COL6A3+CACNA1S, DYSF+MYH7). Moreover, a variety of phenotype-influencing variants were postulated, including in patients with an identified already known primary pathogenic mutation.

Conclusions

We hypothesize that LGMD could be better described as oligogenic disorders in which dominant clinical presentation can result from the combined effect of mutations in a set of genes. In this view, the inter- and intrafamilial variability could reflect a specific genetic background and the presence of sets of phenotype-influencing or co-causative mutations in genes that either interact with the known LGMD-associated genes or are a part of the same pathways or structures.

Electronic supplementary material

The online version of this article (10.1186/s40246-018-0167-1) contains supplementary material, which is available to authorized users.

Abnormal spontaneous activity in primary myopathic disorders

INTRODUCTION

Reproducible non-insertional spontaneous activity (SA), with the exception of endplate activity, is an unequivocal sign of abnormality and is one of the most useful findings obtained on electromyography.

METHODS

In this retrospective study we analyzed occurrence and distribution of abnormal SA in 151 patients with genetically confirmed myopathies.

RESULTS

Complex repetitive discharges (CRDs) occurred more frequently than fibrillation potentials (fibs) and positive sharp waves (PSWs) in centronuclear myopathy (CNM) and limb-girdle muscular dystrophy type 2A (LGMD-2A), whereas fibs/PSWs were observed more often in desminopathy and facioscapulohumeral dystrophy (FSHD). Abnormal SA was commonly found in CNM (66.7%) and desminopathy (61.5%), occasionally in Duchenne (DMD) and Becker muscular dystrophy (BMD) (45.2% and 27.6%, respectively), but rarely in FSHD (14.9%) and LGMD-2A (12.0%).

CONCLUSIONS

Abnormal SA probably occurs more frequently in disorders associated with structural changes in muscle fibers. Screening for SA may be a valuable tool for diagnosis of non-myotonic myopathies. Muscle Nerve 56: 427-432, 2017.

Are electrophysiological criteria useful in distinguishing childhood demyelinating neuropathies?

Childhood chronic inflammatory demyelinating polyneuropathy (CIDP) needs to be differentiated from hereditary neuropathy. We aimed to validate existing CIDP nerve conduction study (NCS) criteria in a group of children with demyelinating neuropathies of chronic or subacute onset. Retrospective analysis of clinical and NCS results in 18 children with CIDP, 7 with hereditary neuropathy with pressure palsy (HNPP), and 24 with Charcot-Marie-Tooth 1a (CMT1a). AAN and EFNS electrodiagnostic CIDP criteria were fulfilled in 17 of 18 CIDP, 3 of 7 HNPP, and 23 of 24 CMT1a patients. A distal compound muscle action potential (dCMAP) of >9 ms was observed in 14 of 18 CIDP patients but not in any patients with HNPP. Abnormal median/normal sural SNAP (AMNS) and a 10 m/s difference between conduction velocities (CV) of two corresponding nerves were not observed in any CMT1a patients. NCS in CMT1a, HNPP, and CIDP reflect demyelination. dCMAP duration, sensory AMNS, and a 10 m/s CV difference parameter are most useful in the differential diagnosis of pediatric CIDP.

Efficacy and safety of abobotulinumtoxinA liquid formulation in cervical dystonia: A randomized-controlled trial

BACKGROUND

Approved botulinum toxin A products require reconstitution. AbobotulinumtoxinA solution for injection is a ready-to-use liquid formulation of abobotulinumtoxinA.

OBJECTIVES

The objective of this study was to demonstrate the superior efficacy of abobotulinumtoxinA solution for injection to placebo and to test the noninferior efficacy of abobotulinumtoxinA solution for injection versus abobotulinumtoxinA (dry formulation) in cervical dystonia.

METHODS

This was a phase-3, multicenter, prospective, double-blind, randomized, active, and placebo-controlled study (N = 369). Patients with cervical dystonia were randomized (3:3:1) to abobotulinumtoxinA solution for injection 500 U, abobotulinumtoxinA 500 U, or placebo. Following the double-blind phase, patients received abobotulinumtoxinA solution for injection, open-label, for up to 4 cycles. The primary outcome was change from baseline at week 4 of the Toronto Western Spasmodic Torticollis Rating Scale total score. Secondary measures included change from baseline or cycle baseline in Toronto Western Spasmodic Torticollis Rating Scale scores.

RESULTS

At week 4, both products were superior to placebo (Toronto Western Spasmodic Torticollis Rating Scale total score least square mean decrease from baseline, abobotulinumtoxinA solution for injection 500 U -12.5, abobotulinumtoxinA 500 U -14.0, placebo -3.9; P < .0001 vs placebo). The noninferiority limit of 3 points in the Toronto Western Spasmodic Torticollis Rating Scale total score at week 4 was not met for abobotulinumtoxinA solution for injection versus abobotulinumtoxinA. Toronto Western Spasmodic Torticollis Rating Scale total score reductions were maintained for up to 4 cycles of abobotulinumtoxinA solution for injection open-label follow-up treatment. Safety profiles of abobotulinumtoxinA solution for injection and abobotulinumtoxinA were similar, with dysphagia and injection-site pain the most frequent drug-related adverse events.

CONCLUSIONS

Although the predefined noninferiority criterion was not met, abobotulinumtoxinA solution for injection was similarly effective to freeze-dried abobotulinumtoxinA in reducing Toronto Western Spasmodic Torticollis Rating Scale total scores with a similar safety profile. AbobotulinumtoxinA solution for injection efficacy was maintained with chronic open-label treatment, and this novel formulation may add convenience as well as dosing accuracy to treatment with abobotulinumtoxinA. © 2016 International Parkinson and Movement Disorder Society.

Dopa-responsive dystonia or early-onset Parkinson disease - Genotype-phenotype correlation

OBJECTIVE

Dopa-responsive dystonia (DRD) is a rare form of hereditary movement disorder with onset in childhood, characterized by gait difficulties due to postural dystonia with marked improvement after low doses of levodopa. Mutations in the GCH1 gene are the most common cause of DRD, however, in some cases when the disease is associated with parkinsonism mutations in the PARK2 gene may be identified. The aim of this study was to analyze and compare genotype-phenotype correlation.

MATERIAL/PARTICIPANTS

Four families with inter- and intrafamilial variability of progressive gait dysfunction due to lower limb dystonia occurring in childhood or adolescence were included in the analysis.

METHODS

General and neurological examination was performed for all affected family members and asymptomatic mutation carriers. The molecular analysis encompassed GCH1 and PARK2 genes.

RESULTS

All probands were clinically diagnosed with DRD. The molecular analysis revealed, however, that the dopa-responsive dystonia phenotype was caused by a mutation in the GCH1 gene in three families and in the PARK2 gene in one family. Obtained results allowed to establish the final diagnosis for all families as DYT5a or early-onset Parkinson disease (EO-PD).

CONCLUSIONS

Reported cases confirm that the DRD phenotype may have heterogeneous genetic background and may be caused by point mutations or rearrangements in the GCH1 gene as well as in the PARK2 gene. Differential diagnosis and genetic tests covering the analysis of genes causative for DRD and EO-PD should be obligatory in both disorders diagnostics as DRD, mainly adolescent onset dystonia, may be associated with parkinsonism.

Exome sequencing reveals mutations in MFN2 and GDAP1 in severe Charcot-Marie-Tooth disease

The aim of our study was to characterize electrophysiologically and explain the genetic cause of severe Charcot-Marie-Tooth (CMT) in a 3.5-year-old with asymptomatic parents and a maternal grandfather with a history of mild adult-onset axonal neuropathy. Severity of neuropathy was assessed by Charcot-Marie-Tooth neuropathy score (CMTNS). Whole-exome sequencing was performed using an Illumina TruSeq Exome Enrichment Kit on the HiSeq 1500 with results followed up by Sanger sequencing on an ABI Prism 3500XL (Applied Biosystems, Foster City, CA, USA). Paternity was confirmed using a panel of 15 hypervariable markers. Electrophysiological studies demonstrated severe axonal sensory-motor neuropathy in the proband, mild motor neuropathy in his mother, and mild sensory-motor neuropathy in his grandfather. CMTNS in the proband, his mother, and grandfather was 21, 1, and 12, respectively. On genetic analysis, the boy was found to carry a heterozygous dominant MFN2 T236M mutation transmitted via the maternal line and a de novo GDAP1 H123R mutation. Our findings emphasize the need to search for more than one causative mutation when significant intrafamilial variability of CMT phenotype occurs and underline the role of whole-exome sequencing in the diagnosis of compound forms of CMT disease.

BAG3-related myopathy, polyneuropathy and cardiomyopathy with long QT syndrome

BAG3 belongs to BAG family of molecular chaperone regulators interacting with HSP70 and anti-apoptotic protein Bcl-2. It is ubiquitously expressed with strong expression in skeletal and cardiac muscle, and is involved in a panoply of cellular processes. Mutations in BAG3 and aberrations in its expression cause fulminant myopathies, presenting with progressive limb and axial muscle weakness, and respiratory insufficiency and neuropathy. Herein, we report a sporadic case of a 15-years old girl with symptoms of myopathy, demyelinating polyneuropathy and asymptomatic long QT syndrome. Genetic testing demonstrated heterozygous mutation Pro209Leu (c.626C > T) in exon 3 of BAG3 gene causing severe myopathy and neuropathy, often associated with restrictive cardiomyopathy. We did not find a mutation in any known LQT syndrome genes. Analysis of muscle biopsy revealed profound disintegration of Z-discs with extensive accumulation of granular debris and large inclusions within fibers. We demonstrated profound alterations in BAG3 distribution as the protein localized to long filamentous structures present across the fibers that were positively stained not only for α-actinin but also for desmin and filamin indicating that those disintegrated Z-disc regions contained also other sarcomeric proteins. The mutation caused a decrease in the content of BAG3 and HSP70, and also of α-actinin desmin, filamin and fast myosin heavy chain, confirming its severe effect on the muscle fiber morphology and thus function. We provide further evidence that BAG3 is associated with Z-disc maintenance, and the Pro209Leu mutation may occur worldwide. We also provide a summary of cases associated with this mutation reported so far.

Genomic instability in the PARK2 locus is associated with Parkinson's disease

Parkinson’s disease (PD) is a common neurodegenerative disorder affecting mostly elderly people, although there is a group of patients developing so-called early-onset PD (EOPD). Mutations in the PARK2 gene are a common cause of autosomal recessive EOPD. PARK2 belongs to the family of extremely large human genes which are often localised in genomic common fragile sites (CFSs) and exhibit gross instability. PARK2 is located in the centre of FRA6E, the third most mutation-susceptible CFS of the human genome. The gene encompasses a region of 1.3 Mbp and, among its mutations, large rearrangements of single or multiple exons account for around 50 %. We performed an analysis of the PARK2 gene in a group of 344 PD patients with EOPD and classical form of the disease. Copy number changes were first identified using multiplex ligation probe amplification (MLPA), with their ranges characterised by array comparative genomic hybridisation (aCGH). Exact breakpoints were mapped using direct sequencing. Rearrangements were found in eight subjects, including five deletions and three duplications. Rearrangements were mostly non-recurrent and no repetitive sequences or extended homologies were identified in the regions flanking breakpoint junctions. However, in most cases, 1–3 bp microhomologies were present, strongly suggesting that microhomology-mediated mechanisms, specifically non-homologous end joining (NHEJ) and fork stalling and template switching (FoSTeS)/microhomology-mediated break-induced replication (MMBIR), are predominantly involved in the rearrangement processes in this genomic region.

Two desmin gene mutations associated with myofibrillar myopathies in Polish families

Desmin is a muscle-specific intermediate filament protein which forms a network connecting the sarcomere, T tubules, sarcolemma, nuclear membrane, mitochondria and other organelles. Mutations in the gene coding for desmin (DES) cause skeletal myopathies often combined with cardiomyopathy, or isolated cardiomyopathies. The molecular pathomechanisms of the disease remain ambiguous. Here, we describe and comprehensively characterize two DES mutations found in Polish patients with a clinical diagnosis of desminopathy. The study group comprised 16 individuals representing three families. Two mutations were identified: a novel missense mutation (Q348P) and a small deletion of nine nucleotides (A357_E359del), previously described by us in the Polish population. A common ancestry of all the families bearing the A357_E359del mutation was confirmed. Both mutations were predicted to be pathogenic using a bioinformatics approach, including molecular dynamics simulations which helped to rationalize abnormal behavior at molecular level. To test the impact of the mutations on DES expression and the intracellular distribution of desmin muscle biopsies were investigated. Elevated desmin levels as well as its atypical localization in muscle fibers were observed. Additional staining for M-cadherin, α-actinin, and myosin heavy chains confirmed severe disruption of myofibrill organization. The abnormalities were more prominent in the Q348P muscle, where both small atrophic fibers as well large fibers with centrally localized nuclei were observed. We propose that the mutations affect desmin structure and cause its aberrant folding and subsequent aggregation, triggering disruption of myofibrils organization.

Carpal tunnel syndrome in children

Carpal tunnel syndrome rarely occurs in children. We retrospectively analyzed clinical data of 11 patients aged 5-17 diagnosed with carpal tunnel syndrome at a single pediatric neuromuscular center. Nerve conduction studies were performed according to the American Association of Electrodiagnostic Medicine recommendations. Additional imaging tests of the wrist were performed in 10 patients. In our group of 11 children, carpal tunnel syndrome was idiopathic in only 1 case. In the remaining subjects, it was secondary to congenital bone anomaly (6), hypothyroidism (2), or myopathic contractures (1). In 1 case, metabolic workup revealed an underlying mucopolysaccharidosis. Our results confirm that idiopathic carpal tunnel syndrome is rare in children. Hand clumsiness and thenar hypoplasia rather than sensory complaints are the presenting symptoms. Whenever carpal tunnel syndrome is diagnosed in a child, a thorough differential diagnosis should be made because of the secondary nature of this disease in most pediatric patients.

Novel A18T and pA29S substitutions in α-synuclein may be associated with sporadic Parkinson's disease

OBJECTIVE

Mutations in the α-synuclein-encoding gene SNCA are considered as a rare cause of Parkinson's disease (PD). Our objective was to examine the frequency of the SNCA point mutations among PD patients of Polish origin.

METHODS

Detection of the known SNCA point mutations A30P (c.88G>C), E46K (c.136G>A) and A53T (c.157A>T) was performed either using the Sequenom MassArray iPLEX platform or by direct sequencing of the SNCA exons 2 and 3. As the two novel substitutions A18T (c.52G>A) and A29S (c.85G>T) were identified, their frequency in a control population of Polish origin was assessed and in silico analysis performed to investigate the potential impact on protein structure and function.

RESULTS

We did not observe the previously reported point mutations in the SNCA gene in our 629 PD patients; however, two novel potentially pathogenic substitutions A18T and A29S were identified. Each variant was observed in a single patient presenting with a typical late-onset sporadic PD phenotype. Although neither variant was observed in control subjects and in silico protein analysis predicts a damaging effect for A18T and pA29S substitutions, the lack of family history brings into question the true pathogenicity of these rare variants.

CONCLUSIONS

Larger population based studies are needed to determine the pathogenicity of the A18T and A29S substitutions. Our findings highlight the possible role of rare variants contributing to disease risk and may support further screening of the SNCA gene in sporadic PD patients from different populations.

Long lasting dysautonomia due to botulinum toxin B poisoning: clinical-laboratory follow up and difficulties in initial diagnosis

BACKGROUND

Botulism is an acute form of poisoning caused by one of four types (A, B, E, F) toxins produced by Clostridium botulinum, ananaerobic, spore forming bacillus. Usually diagnosis of botulism is considered in patients with predominant motor symptoms: muscle weakness with intact sensation and preserved mental function.

CASE PRESENTATION

We report a case of 56-year-old Caucasian female with a history of arterial hypertension, who presented with acute respiratory failure and bilateral ptosis misdiagnosed as brainstem ischemia. She had severe external and internal ophtalmoplegia, and autonomic dysfunction with neither motor nor sensory symptoms from upper and lower limbs. Diagnosis of botulinum toxin poisoning was made and confirmed by serum antibody testing in the mouse inoculation test.

CONCLUSIONS

Ophtalmoplegia, autonomic dysfunction and respiratory failure can be caused by botulism. Early treatment and intensive care is essential for survival and recovery. The electrophysiological tests are crucial to correct and rapid diagnosis. Botulism (especially type B) should be considered in any case of acute or predominant isolated autonomic dysfunction.

A novel homozygous mutation in the WNK1/HSN2 gene causing hereditary sensory neuropathy type 2

Hereditary sensory and autonomic neuropathy type 2 is a rare disorder caused by recessive mutations in the WNK1/HSN2 gene located on chromosome 12p13.33. Phenotype of the patients is characterized by severe sensory loss affecting all sensory modalities. We report a novel homozygous Lys179fsX182 (HSN2); Lys965fsX968 (WNK1/HSN2) mutation causing an early childhood onset hereditary sensory and autonomic neuropathy type 2, with acromutilations in upper and lower limbs, and autonomic dysfunction. To the best of our knowledge this is the first genetically proven case of hereditary sensory and autonomic neuropathy type 2 originating from East Europe.

A novel homozygous mutation in the WNK1/HSN2 gene causing hereditary sensory neuropathy type 2

Hereditary sensory and autonomic neuropathy type 2 is a rare disorder caused by recessive mutations in the WNK1/HSN2 gene located on chromosome 12p13.33. Phenotype of the patients is characterized by severe sensory loss affecting all sensory modalities. We report a novel homozygous Lys179fsX182 (HSN2); Lys965fsX968 (WNK1/HSN2) mutation causing an early childhood onset hereditary sensory and autonomic neuropathy type 2, with acromutilations in upper and lower limbs, and autonomic dysfunction. To the best of our knowledge this is the first genetically proven case of hereditary sensory and autonomic neuropathy type 2 originating from East Europe.