Phenotypical characterization of α-galactosidase A gene mutations identified in a large Fabry disease screening program in stroke in the young

Objective

In the Belgian Fabry Study (BeFaS), the prevalence of Fabry disease was assessed in 1000 young patients presenting with stroke, unexplained white matter lesions or vertebrobasilar dolichoectasia. The results of the BeFaS suggested that Fabry disease may play a role in up to 1% of young patients presenting with cerebrovascular disease. However, the clinical relevance was unclear in all cases. We report on detailed phenotyping in subjects identified with α-galactosidase A (α-Gal A) enzyme deficiency or GLA mutations identified in the BeFaS (n = 10), and on the results of family screening in this population.

Methods

Family screening was performed to identify additional mutation carriers. Biochemical and/or clinical evaluation of all subjects (BeFaS index patients and relatives carrying a GLA mutation) was performed.

Results

Genetic family screening revealed 18 additional GLA mutation carriers. Bloodspot α-Gal A enzyme activity was normal in all GLA mutation carriers, even in 2 males with the p.A143T mutation. Plasma Gb3 and lyso-Gb3 levels were normal in all subjects. Elevated Gb3 in urine was detected in 2 subjects. Some classic clinical signs of Fabry disease, like angiokeratoma or cornea verticillata, could not be detected in our population. Cardiac symptoms of Fabry disease were found in 6 out of 10 p.A143T carriers. No signs of cerebrovascular disease were found in the relatives with a GLA mutation.

Conclusions

We could not identify mutations causing the classical clinical phenotype of Fabry disease in our cerebrovascular disease population. Enzyme activity analysis in bloodspots and plasma may fail to identify late-onset variants of Fabry disease. We recommend genetic testing when an atypical, late-onset variant of Fabry disease is suspected in a male cerebrovascular disease patient. However, this may lead to the identification of non-disease causing or controversial genetic variants.     

A novel AIFM1 mutation in a Chinese family with X-linked Charcot–Marie–Tooth disease type 4

X-linked Charcot–Marie–Tooth disease type 4 (CMTX4), caused by AIFM1 (Apoptosis-Inducing Factor, Mitochondrion associated 1) mutations and associated with deafness and cognitive impairment, is a rare subtype of Charcot–Marie–Tooth disease. Here, we report a novel missense variant of AIFM1 in a X-linked recessive Chinese family with childhood-onset, slowly progressive, isolated axonal motor and sensory neuropathy. Calf magnetic resonance imaging revealed fatty infiltration and atrophy severely involving the muscles of peroneal compartment. Pathologies exhibited abnormal mitochondrial morphology and accumulation in axoplasm of nerve fiber and subsarcolemmal area of muscle. A hemizygous variant (c.513G>A, p.Met171Ile) in the family was identified and was classified as likely pathogenic according to the standards and guidelines of the American College of Medical Genetics and Genomics. Our report expands the genetic spectrum of diseases related to AIFM1 mutations and indicates that fatty infiltration and atrophy of muscles in the peroneal compartment may be a feature of CMTX4 in early stage.     

A novel mutation of gap junction protein β 1 gene in X-linked Charcot-Marie-Tooth disease

Introduction: In this study we report a novel mutation in the gap junction protein beta 1 (GJB1) gene of a Chinese X‐linked Charcot–Marie–Tooth disease (CMTX1) family, which has specific electrophysiological characteristics. Methods: Twenty members in the family were studied by clinical neurological examination and GJB1 gene mutation analysis, and 3 patients were studied electrophysiologically. The proband and his mother also underwent sural nerve biopsy. Results: All patients have the CMT phenotype, except for 2 asymptomatic carriers. Electrophysiological examinations showed non‐uniform slowing of motor conduction velocities and partial motor conduction blocks and temporal dispersion. Sural nerve biopsy confirmed a predominantly demyelinating neuropathy, and an Asn2Lys mutation in the amino‐terminal domain was found in 9 members of this family, but not in 25 normal controls in the family. Conclusions: This family represents a novel mutation in the GJB1 form of CMTX1. The mutation in the amino‐terminus has an impact on the electrophysiological characteristics of the disease. Muscle Nerve, 2011     

A novel heterozygous deletion–insertion mutation (2695–2712 del/GTTTGT ins) in exon 18 of the filamin C gene causes filaminopathy in a large Chinese family

Filaminopathy represents a rare subgroup of myofibrillar myopathies caused by mutation in filamin C gene. We present a Chinese family with filaminopathy, characterized by onset at the age of 35–40 years with progressive muscle weakness in all limbs. Mild cardiac symptoms and chronic diarrhea were present in a few patients. Muscle biopsy revealed numerous spheroid bodies and amorphous deposits in the fibers, which were positive for desmin, dysferlin, dystrophin and ubiquitin, but negative for α-actinin and α-synuclein. Ultrastructural analysis revealed inclusions composed of disorganized thin filaments and interspersed electron-dense granules, accumulating in spheroid or cytoplasmic structures. A novel complex mutation of 18-nucleotide deletion and 6-nucleotide insertion was identified in exon 18 of the filamin C gene, resulting in an in-frame 6 amino acid deletion (Lys899-Val904) and a 2 amino acid insertion (Val 899-Cys900) in the seventh Ig-like repeat of filamin C. Our findings expand the genetic spectrum and geographic distribution of filaminopathy.     

A novel mutation of the glycyl-tRNA synthetase (GARS) gene associated with Charcot–Marie–Tooth type 2D in a Chinese family

Abstract

Objective:

To explore the clinical features of a novel glycyl-tRNA synthetase (GARS) gene mutation in a family with Charcot–Marie–Tooth disease type 2D (CMT2D).

Methods:

Exome capture with the next-generation sequencing technique was used to detect gene mutations. The mutations were verified by the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique combined with DNA sequencing.

Results:

In this pedigree, eight members were affected; seven males and one female. The affected members initially manifested with the onset of hand muscle weakness and atrophy in adolescence followed by gradual development of distal lower limb involvement and minor sensory involvement. Electrophysiological studies revealed that this disease mainly involves axonal damage. Genetic detection showed that all affected family members had a heterozygous missense mutation, c.999G>T (p.E333D), of the GARS gene.

Conclusions:

The c.999G>T mutation is a novel mutation of the GARS gene that has not been previously reported. The phenotype of this family is CMT2D, which is first reported in Chinese population.     

A novel mutation in the sodium channel α1 subunit gene in a child with Dravet syndrome in Turkey

Dravet syndrome is a rare epileptic encephalopathy characterized by frequent seizures beginning in the first year of life and behavioral disorders. Mutations in the sodium channel α1 subunit gene are the main cause of this disease. We report two patients with refractory seizures and psychomotor retardation in whom the final diagnosis was Dravet syndrome with confirmed mutations in the sodium channel α1 subunit gene. The mutation identified in the second patient was a novel frame shift mutation, which resulted from the deletion of five nucleotides in exon 24.     

A novel homozygous nonsense mutation in NEFL causes autosomal recessive Charcot–Marie–Tooth disease

The neurofilament light polypeptide (NEFL) gene mutations cause mainly autosomal dominant Charcot–Marie–Tooth disease (CMT) and rarely the recessive forms of CMT. We describe a 13-year-old girl born of consanguineous parents. She presented an early onset of gait disturbance with weakness in lower extremities during the first decade. Nerve conduction velocity of median nerve was 24 m/s and amplitude of compound muscle action potential was 2.2 mV. Sensory nerve action potential was not recordable. Sural nerve biopsy showed severe loss of the large myelinated fibers. Electron microscopy revealed absence of neurofilaments in both myelinated and unmyelinated axons. Genetic analysis identified a novel homozygous nonsense mutation in NEFL c.487G>T (p.Glu163*) as the potential causative mutation in this patient. Our study expands the mutation spectrum of NEFL-related neuropathy.     

PARK1 gene mutation of autosomal dominant Parkinson’s disease family

Studies have shown that PARK1 gene is associated with the autosomal dominant inheritance of Parkinson’s disease. PARK1 gene contains two mutation sites, namely Ala30Pro and Ala53Thr, which are located on exons 3 and 4, respectively. However, the genetic loci of the pathogenic genes remain unclear. In this study, blood samples were collected from 11 members of a family with high prevalence of Parkinson’s disease, including four affected cases, five suspected cases, and two non-affected cases. Point mutation screening of common mutation sites on PARK1 gene exon 4 was conducted using PCR, to determine the genetic loci of the causative gene for Parkinson’s disease. Gene identification and sequencing results showed that a T base deletion mutation was observed in the PARK1 gene exon 4 of all 11 collected samples. It was confirmed that the PARK1 gene exon 4 gene mutation is an important pathogenic mutation for Parkinson’s disease.     

Cerebral vasculopathy in a Chinese family with neurofibromatosis type Ⅰ mutation

Neurofibromatosis type I（NF1） is a hereditary,autosomal dominant,neurocutaneous syndrome that is attributed to NF1 gene mutation.NF1 has been associated with scoliosis,macrocephaly,pseudoarthrosis,short stature,mental retardation,and malignancies.NF1-associated vasculopathy is an uncommon and easily-overlooked presentation.Examination of a Chinese family affected by NF1 combined with cerebral vessel stenosis and/ or abnormality suggested a possible relationship between NF1 and vessel stenosis.To determine which NF1 gene mutation is associated with vascular lesions,particularly cerebral vessel stenosis,we examined one rare family with combined cerebral vessel lesions or maldevelopment.Vascular lesions were detected using transcranial Doppler sonography and digital subtraction angiography in family members.Next,denaturing high-performance liquid chromatography and sequencing were used to screen for NF1 gene mutations.The results revealed a nonsense mutation,c.541C＆gt;T,in the NF1 gene.This mutation truncated the NF1 protein by 2659 aminoacid residues at the C-terminus and co-segregated with all of the patients,but was not present in unaffected individuals in the family.Exceptionally,three novel mutations were identified in unaffected family members,but these did not affect the product of the NF1 gene.Thus the nonsense mutation,c.541C＆gt;T,located in the NF1 gene could constitute one genetic factor for cerebral vessel lesions.     

Abundant neuritic inclusions and microvacuolar changes in a case of diffuse Lewy body disease with the A53T mutation in the α-synuclein gene

We report here a case of diffuse Lewy body disease with the A53T mutation in the -synuclein gene. The proband presented at the age of 41 years with parkinsonism that was poorly responsive to levodopa. She subsequently developed cognitive impairment and moderate dementia, and died at the age of 50. Her father, paternal grandfather and uncle were all reported to have suffered from Parkinsons disease. Staining of tissue sections from the probands brain with hematoxylin-eosin and -synuclein antibodies showed small numbers of Lewy bodies in a few brain regions. This contrasted with large numbers of Lewy neurites and neuroaxonal spheroids in many brain regions. By electron microscopy, Lewy neurites consisted of abnormal filaments and dense granular material. Isolated filaments resembled those previously described in idiopathic Parkinsons disease and dementia with Lewy bodies. They were decorated by antibodies specific for the N and C termini of -synuclein, indicating the presence of the full-length protein. Nucleus accumbens and the lower layers in limbic areas of the cerebral cortex showed prominent vacuolation, with frequent clustering of microvacuoles around Lewy neurites. Nerve cell loss was most extensive in dorsal motor nucleus of the vagus nerve, substantia nigra and nucleus basalis of Meynert. Neurofibrillary tangles and senile plaques were not observed. However, in several brain regions, a few widely scattered tau-positive nerve cell bodies and neurites were present. By electron microscopy, Alzheimer-type paired helical and straight filaments were seen.     

PEN–2 gene mutation in a familial Alzheimer’s disease case

Genetic evidence indicates a central role of cerebral accumulation of β–amyloid (Aβ) in the pathogenesis of Alzheimer’s disease (AD). Beside presenilin 1 and 2, three other recently discovered proteins (Aph 1, PEN 2 and nicastrin) are associated with γ–secretase activity, the enzymatic complex generating Aβ. Alterations in genes encoding these proteins were candidates for a role in AD. The PEN 2 gene was examined for unknown mutations and polymorphisms in sporadic and familial Alzheimer patients. Samples from age–matched controls (n = 253), sporadic AD (SAD, n = 256) and familial AD (FAD, n = 140) were screened with DHPLC methodology followed by sequencing. Scanning the gene identified for the first time a missense mutation (D90N) in a patient with FAD. Three intronic polymorphisms were also identified, one of which had a higher presence of the mutated allele in AD subjects carrying the allele ε4 of apolipoprotein E than controls. The pathogenic role of the PEN–2 D90N mutation in AD is not clear, but the findings might lead to new studies on its functional and genetic role.*These two authors contributed equally to the paper.     

Adenosine A2A receptor gene disruption protects in an α-synuclein model of Parkinson's disease

To investigate the putative interaction between chronic exposure to adenosine receptor antagonist caffeine and genetic influences on Parkinson's disease (PD), we determined whether deletion of the adenosine A(2A) receptor in knockout (KO) mice protects against dopaminergic neuron degeneration induced by a mutant human α-synuclein (hm(2)-αSYN) transgene containing both A53T and A30P. The A(2A) KO completely prevented loss of dopamine and dopaminergic neurons caused by the mutant α-synuclein transgene without altering levels of its expression. The adenosine A(2A) receptor appears required for neurotoxicity in a mutant α-synuclein model of PD. Together with prior studies the present findings indirectly support the neuroprotective potential of caffeine and more specific A(2A) antagonists.     

BAG3 p.Pro209Ser mutation identified in a Chinese family with Charcot–Marie–Tooth disease

Journal of Neurology - Bcl2-associated athanogene 3 (BAG3) gene mutations cause dilated cardiomyopathy and myofibrillar myopathy. Recently, a novel c.625C>T (p.Pro209Ser) mutation in BAG3...     

Confirmation of the GNB4 gene as causal for Charcot–Marie–Tooth disease by a novel de novo mutation in a Czech patient

The association of GNB4 with Charcot–Marie–Tooth (CMT) has recently been described in a publication by Soong et al. (Soong, et al., 2013). Here we present a patient with CMT in whom whole exome sequencing identified the mutation p.Lys57Glu in the GNB4 gene (NM_021629.3:c.169A>G). The patient, now 41 years old, is a sporadic case in the family. At the age of 35 he presented with severe disability (CMT neuropathy score 29), profound muscle atrophies, pes cavus and scoliosis. Previously, the patient was tested for PMP22 duplications/deletions and later also with 64 CMT gene panel, with no causal variant found. Subsequently, whole exome sequencing was performed. The p.Lys57Glu in the GNB4 gene was identified as the most probable causal variant, the mutation is not present in the patient's parents, neither in his unaffected sister, therefore we assume that the mutation arose de novo. Taken together, these findings support the causal and pathogenic character of the variant. Our report provides important evidence that GNB4 should become an established CMT gene and our findings confirm the original publication by Soong et al. (2013).     

A Turkish family with Sj?gren-Larsson syndrome caused by a novel ALDH3A2 mutation

Sjögren-Larsson syndrome (SLS) is an inherited neurocutaneous disorder caused by mutations in the aldehyde dehydrogenase family 3 member A2 (ALDH3A2) gene that encodes fatty aldehyde dehydrogenase. Affected patients display ichthyosis, mental retardation, and spastic diplegia. More than 70 mutations in ALDH3A2 have been discovered in SLS patients. We diagnosed two brothers age of 12 and 20 years with characteristic features of this rare syndrome. Magnetic resonance imaging showed demyelinating disease in both of them. We described a novel homozygous, c. 835 T > A (p.Y279N) mutation in exon 6 in two patients.