Cramp‐fasciculation syndrome (CFS) is a rare muscle hyperexcitability syndrome that presents with muscle cramps, fasciculations, and stiffness, as well as pain, fatigue, anxiety, hyperreflexia, and ...paresthesias. Although familial cases have been reported, a genetic etiology has not yet been identified. We performed whole‐exome sequencing followed by validation and cosegregation analyses on a father‐son pair with CFS. Both subjects manifested other hypersensitivity‐hyperexcitability symptoms, including asthma, gastroesophageal reflux, migraine, restless legs syndrome, tremor, cold hyperalgesia, and cardiac conduction defects. Most symptoms improved with carbamazepine, consistent with an underlying cation channelopathy. We identified a variant in the transient receptor potential ankyrin A1 channel (TRPA1) gene that selectively cosegregated with CFS and the other hypersensitivity‐hyperexcitability symptoms. This variant (c.2755C>T) resulted in a premature stop codon at amino acid 919 (p.Arg919*) in the outer pore of the channel. TRPA1 is a widely distributed, promiscuous plasmalemmal cation channel that is strongly implicated in the pathophysiology of the specific hypersensitivity‐hyperexcitability symptoms observed in these subjects. Thus, we have identified a novel TRPA1 variant that is associated with CFS as part of a generalized hypersensitivity‐hyperexcitability disorder. These findings clarify the diverse functional roles of TRPA1, and underscore the importance of this channel as a potential therapeutic target.
Background: PLA2G6 mutations are known to be responsible for infantile neuroaxonal dystrophy (INAD) and neurodegeneration with brain iron accumulation (NBIA). In addition, novel mutations in PLA2G6 ...have recently been associated with dystonia‐parkinsonism in two unrelated consanguineous families.
Methods: Direct sequencing analysis of the PLA2G6 gene.
Results: Here, we report the segregation of R632W with disease in an Iranian consanguineous dystonia‐parkinsonism pedigree. The identical mutation was previously observed in a patient affected with NBIA.
Conclusion: We conclude that different and even identical PLA2G6 mutations may cause neurodegenerative diseases with heterogeneous clinical manifestations, including INAD, NBIA and dystonia‐parkinsonism.
Neurodegeneration with brain iron accumulation (NBIA) comprises a clinically and genetically heterogeneous group of neurodegenerative diseases characterized by progressive degeneration of the central ...nervous system and high basal ganglia iron deposition. The list of identified causative genes for NBIA syndromes continues to expand and includes one autosomal dominant, one X‐linked, and a number of recessive forms. Mitochondrial membrane protein‐associated neurodegeneration is a recently described NBIA syndrome caused by C19orf12 mutations. In this study, we report two consanguineous families with a homozygous C19orf12 p.Thr11Met mutation. Our patients presented at a later age and had more rapid disease progression, leading to early death in two, than those previously reported. We conclude that C19orf12 mutation is associated with wide phenotypic heterogeneity, and that further research is needed to examine the role of C19orf12 in NBIA and related diseases and to elucidate its protein function as well as other factors that may affect disease progression and expression.
PNPLA6
mutations, known to be associated with the development of motor neuron phenotypes, have recently been identified in families with Boucher–Neuhäuser syndrome. Boucher–Neuhäuser is a rare ...autosomal recessive syndrome characterized by the co-occurrence of cerebellar ataxia, hypogonadotropic hypogonadism, and chorioretinal dystrophy. Gait ataxia in Boucher–Neuhäuser usually manifests before early adulthood, although onset in the third or fourth decade has also been reported. However, given the recent identification of
PNPLA6
mutations as the cause of this condition, the determining factors of age of symptom onset still need to be established. Here, we have identified a sporadic Boucher–Neuhäuser case with late-onset gait ataxia and relatively milder retinal changes due to compound heterozygous
PNPLA6
mutations. Compound heterozygosity was confirmed by cloning and sequencing the patient’s genomic DNA from coding exons 26–29. Furthermore, both mutations (one novel and one known) fell in the phospholipase esterase domain, where most pathogenic mutations seem to cluster. Taken together, we herein confirm
PNPLA6
mutations as the leading cause of Boucher–Neuhäuser syndrome and suggest inquiring about a history of hypogonadism or visual changes in patients presenting with late-onset gait ataxia. We also advocate for neuroophthalmologic evaluation in suspected cases.
We present here the clinical, molecular and biochemical findings from 238 limb-girdle muscular dystrophy type 2A (LGMD2A) patients, representing ∼50% (238 out of 484) of the suspected calpainopathy ...cases referred for the molecular study of the calpain 3 (CAPN3) gene. The mean age at onset of LGMD2A patients was ∼14 years, and the first symptoms occurred between 6 and 18 years of age in 71% of patients. The mean age at which the patients became wheelchair bound was 32.2 years, with 84% requiring the use of a wheelchair between the age of 21 and 40 years. There was no correlation between the age at onset and the time at which the patient became wheelchair bound, nor between the sex of the patient and the risk of becoming wheelchair bound. Of the cases where the CAPN3 gene was not affected, ∼20% were diagnosed as LGMD2I muscular dystrophy, while facioscapulohumeral muscular dystrophy (FSHD) was uncommon in this sample. We identified 105 different mutations in the CAPN3 gene of which 50 have not been described previously. These were distributed throughout the coding region of the gene, although some exons remained free of mutations. The most frequent mutation was 2362AG→TCATCT (exon 22), which was present in 30.7% of the chromosomes analysed (146 chromosomes). Other recurrent mutations described were N50S, 550ΔA, G222R, IVS6-1G→A, A483D, IVS17+1G→T, 2069–2070ΔAC, R748Q and R748X, each of which was found in >5 chromosomes. The type of mutation in the CAPN3 gene does not appear to be a risk factor for becoming dependent on a wheelchair at a determined age. However, in the cases with two null mutations, there were significantly fewer patients that were able to walk than in the group of patients with at least one missense mutation. Despite the fact that the results of phenotyping and western blot might be biased due to multiple referral centres, producing a diagnosis on the basis of the classical phenotype is neither sufficiently sensitive (86.7%) nor specific (69.3%), although western blot proved to be even less sensitive (52.5%) yet more specific (87.8%). In this case LGMD2I was a relevant cause of false-positive diagnoses. Considering both the clinical phenotype and the biochemical information together, the probability of correctly diagnosing a calpainopathy is very high (90.8%). However, if one of the analyses is lacking, the probability varies from 78.3 to 73.7% depending on the information available. When both tests are negative, the probability that the sample comes from a patient with LGMD2A was 12.2%.
Abstract Early-onset Alzheimer's disease (EOAD) is a clinically and genetically heterogeneous condition in which the typical features appear significantly earlier in life (before 65 years). Mutations ...in three genes ( PSEN1 , PSEN2 , and APP ) have been identified in autosomal dominant forms of EOAD. However, in about 50% of Mendelian cases and in most of the sporadic EOAD patients, no mutations have been found. We present clinical characteristics of an Israeli family comprising two affected siblings with EOAD born to neurologically healthy parents who were first cousins (both parents died after 90 years old). Sequence analysis of PSEN1 , PSEN2 , APP , TAU , PGRN , and PRNP failed to reveal any mutations in the affected siblings. Because the disease in this family is consistent with an autosomal recessive mode of inheritance we identified all homozygous regions identical by descent (IBD) in both siblings, by high-density SNP genotyping. We provide here the first catalog of autozygosity in EOAD and suggest that the regions identified are excellent candidate loci for a recessive genetic lesion causing this disease.
In addition to the four well-confirmed genes linked to early-onset Parkinson disease (PD) (SNCA, PARKIN, DJ-1, and PINK1), mutations in the leucine-rich repeat kinase 2 gene (LRRK2) have recently ...been identified in families with autosomal dominant late-onset PD.
To perform mutation analysis of LRRK2 in probands of families showing dominant inheritance of PD and to conduct a case control association study to test the hypothesis that common coding variations might be associated with increased susceptibility to PD.
All 51 LRRK2 coding exons were sequenced in 23 probands and the mutation frequencies were evaluated in 180 neurologically normal control subjects. For the association study the authors genotyped four coding LRRK2 polymorphisms in 250 normal control subjects and 121 patients with PD (predominantly white patients of Canadian origin), 84% of whom had age at onset before 50 years and 42% had a positive family history.
The authors identified three probands with heterozygous LRRK2 mutations: two of them have the known G2019S substitution and one proband has a novel I1371V substitution. Mutation analysis of a large family demonstrated complete segregation of the G2019S with PD. However, there was no association between PD and any of the four polymorphisms at the allelic or genotypic levels (p > 0.17). Furthermore, the authors did not detect a modifying effect for any genotype or of APOE genotypes upon the age at onset in the PD group (p > 0.20).
The results support the prior suggestion that LRRK2 mutations cause PD. The disease in the families reported here presents a phenotype indistinguishable from typical PD. All three families demonstrate a very variable age at onset that is not explained by APOE genotypes. The common coding variations in the LRRK2 gene neither constitute strong PD risk factors nor modify the age at onset; however, the possibility of a modest risk effect remains to be assessed in large datasets.
Background: We and others recently identified the gene underlying PARK8 linked Parkinson’s disease (PD). This gene, LRRK2, contains mutations that cause an autosomal dominant PD, including a ...mutation, G2019S, which is the most common PD causing mutation identified to date. Common genetic variability in genes that contain PD causing mutations has previously been implicated as a risk factor for typical sporadic disease. Methods: We undertook a case-control association analysis of LRRK2 in two independent European PD cohorts using 31 tagging single nucleotide polymorphisms (tSNPs) and five potentially functional SNPs. To assess the structure of this locus in different populations, we have performed linkage disequilibrium (LD) analysis using these variants in a human diversity panel. Results: We show that common genetic variability in LRRK2 is not associated with risk for PD in the European populations studied here. We also show inter-population variability in the strength of LD across this locus. Conclusions: To our knowledge this is the first comprehensive analysis of common variability within LRRK2 as a risk factor for PD.
Background: Autosomal recessive hereditary spastic paraplegia (ARHSP) with thin corpus callosum is a distinct and usually severe form of complex hereditary spastic paraplegia classified as SPG11. ...Recently mutations on SPG11 gene (KIAA1840), which is localized to chromosome 15q13‐q15, were shown to cause the majority of SPG11 cases.
Methods: We analysed the 40 coding exons of this gene in the probands from eight families with complex ARHSP, four of these families had a thin corpus callosum and two has mild thinning.
Results: Three families were identified with novel mutations in the SPG11 gene. One family was of Asian origin with a homozygous nonsense mutation and had a very severe phenotype but only very mild thinning of the corpus callosum. In the other two English families the parents were unrelated and the mutations were compound heterozygotes. In these two families the phenotype was mild and both probands had a thin corpus callosum.
Conclusion: Given the probable mechanism of action of the mutations in the Spatacsin gene, we discuss the probable genotype phenotype correlations in these families. This study confirms the frequent occurrence of Spatacsin mutations in complex ARHSP with genotype phenotype effects and exposes the spectrum of clinical heterogeneity in SPG11.
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