The objective was to test the hypothesis that a described association between homozygosity for a 50bp deletion in the SOD1 promoter 1684bp upstream of the SOD1 ATG and an increased age of onset in SALS can be replicated in additional SALS and control sample sets from other populations. Our second objective was to examine whether this deletion attenuates expression of the SOD1 gene. Genomic DNA from more than 1200 SALS cases from Ireland, Scotland, Quebec and the USA was genotyped for the 50bp SOD1 promoter deletion. Reporter gene expression analysis, electrophoretic mobility shift assays and chromatin immunoprecipitation studies were utilized to examine the functional effects of the deletion. The genetic association for homozygosity for the promoter deletion with an increased age of symptom onset was confirmed overall in this further study (p=0.032), although it was only statistically significant in the Irish subset, and remained highly significant in the combined set of all cohorts (p=0.001). Functional studies demonstrated that this polymorphism reduces the activity of the SOD1 promoter by approximately 50%. In addition we revealed that the transcription factor SP1 binds within the 50bp deletion region in vitro and in vivo. Our findings suggest the hypothesis that this deletion reduces expression of the SOD1 gene and that levels of the SOD1 protein may modify the phenotype of SALS within selected populations.
X-linked adrenoleukodystrophy is a peroxisomial disorder caused by mutations in the ABCD1 gene. Adrenomyeloneuropathy is the second most frequent phenotype (25-46%) of this disease and classically presents in adulthood with spastic paraparesis. Female heterozygotes can be symptomatic, but they are frequently misdiagnosed as having multiple sclerosis.
We report a novel missense mutation in the ABCD1 gene in a 47-year-old French-Canadian female with spastic paraparesis and no confirmed family history of X-linked adrenoleukodystrophy. The mutation is located on exon 1 and causes the amino acid substitution of a valine for an alanine in a region of the protein highly conserved between mouse and man.
Adrenomyeloneuropathy must be considered in the differential diagnosis of spastic paraparesis in men or women. This is an initial report of an ABCD1 gene mutation in the French-Canadian population, which should lead to the recognition of other cases in the future.
Substantial efforts have been deployed in the past decade to identify the genetic causes of amyotrophic lateral sclerosis (ALS), and we hypothesized here that mutations in SORT1 or aberrant SORT1 splicing reduce progranulin level and promote neurodegeneration.
We sequenced the coding exons of SORT1 in a cohort of 112 unrelated individuals with familial ALS. We also tested for aberrant SORT1 splicing by RT-PCR using RNA samples from cell lines expressing six different ALS-associated TARDBP mutations.
We identified one unique missense and two unique silent mutations in our cohort. None are predicted to have functional effects. No aberrant SORT1 splicing event was observed.
SORT1 mutations are not a common cause of familial ALS, and the influence of TARDBP mutations on SORT1 splicing still needs to be clarified.
Hereditary spastic paraplegias (HSPs) are characterized by progressive lower limb spasticity and weakness. Mutations in the SPG3A gene, which encodes the large guanosine triphosphatase atlastin, are the second most common cause of autosomal dominant hereditary spastic paraplegia. In a large SPG3A screen of 70 hereditary spastic paraplegia subjects, a novel in-frame deletion, p.del436N, was identified. Characterization of this deletion showed that it affects neither the guanosine triphosphatase activity of atlastin nor interactions between atlastin and spastin. Interestingly, immunoblot analysis of lymphoblasts from affected patients demonstrated a significant reduction in atlastin protein levels, supporting a loss-of-function disease mechanism.
Recently, chromogranins were reported to interact specifically with mutant forms of superoxide dismutase that are linked to amyotrophic lateral sclerosis (ALS). This interaction led us to analyze the frequencies of sequence variants of the CHGB gene in ALS patients and matched controls from three different countries. Of particular interest was the finding of the P413L CHGB variant present in 10% of ALS patients (n = 705) as compared to 4.5% in controls (n = 751), conferring a 2.2-fold greater relative risk to develop the disease (P
Cites: Regul Pept. 2009 Jan 8;152(1-3):13-2118721831
Thirty-three French-Canadian families with non-dystrophic myotonia were identified. Fifty subjects were recruited and submitted to a complete clinical, electrophysiologic and genetic evaluation. Thirteen mutations were identified in CLCN1 and five mutations were identified in SCN4A. Onset in the lower extremities, presence of tongue myotonia and transient weakness suggested recessive CLCN1 mutations. Lid myotonia, absence of hypertrophy and exacerbation with cold temperature suggested SCN4A mutations. Pain was not a feature of dominant CLCN1 mutations while it could be seen in the others, more frequently in SCN4A mutations. Warm up phenomenon, hand grip myotonia, percussion myotonia, lid lag and hormonal effects were not distinguishing features. Repetitive nerve stimulation and short exercise test showed either a large (>50%) or mild-moderate (10-50%) decrement with recessive CLCN1 mutations while they showed only mild or no decrement with dominant CLCN1 and SCN4A mutations. The French-Canadian population shows wide phenotypic and genotypic heterogeneity in non-dystrophic myotonias.
Essential tremor (ET) is a common neurodegenerative disorder that is characterized by a postural or motion tremor. Despite a strong genetic basis, a gene with rare pathogenic mutations that cause ET has not yet been reported. We used exome sequencing to implement a simple approach to control for misdiagnosis of ET, as well as phenocopies involving sporadic and senile ET cases. We studied a large ET-affected family and identified a FUS p.Gln290(*) mutation as the cause of ET in this family. Further screening of 270 ET cases identified two additional rare missense FUS variants. Functional considerations suggest that the pathogenic effects of ET-specific FUS mutations are different from the effects observed when FUS is mutated in amyotrophic lateral sclerosis cases; we have shown that the ET FUS nonsense mutation is degraded by the nonsense-mediated-decay pathway, whereas amyotrophic lateral sclerosis FUS mutant transcripts are not.
Laboratoire de neurogénétique de la motricité, Centre d'Excellence en Neuromique de l'Université de Montréal, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Hôpital Notre-Dame-CHUM, Montréal, Que., Canada.
Charcot-Marie-Tooth polyneuropathies (CMT) are clinically and genetically heterogeneous. We describe a French-Canadian cluster of 17 recessive CMT cases belonging to 10 families with variable early-onset CMT and scoliosis. The patients demonstrate great intra- and inter-familial variability. Linkage analysis confirmed that all families are linked to CMT4C locus on chromosome 5q32 (multipoint LOD score of 9.06). Haplotype analysis suggests that two SH3TC2 mutations are present in this cohort. The majority of carrier chromosomes, 26 of 34 (76%), carry the c.2860C-->T mutation. Despite extensive sequencing, the other mutation is not yet uncovered. This study demonstrates that the clinical variability observed in CMT4C is due to other factors than the nature of the mutation and that further work is needed to better define the SH3TC2 gene to ensure the identification of all CMT4C mutations.