Novel SOD1 mutation p.V31A identified with a slowly progressive form of amyotrophic lateral sclerosis.

The SOD1 gene encoding the superoxide dismutase 1 (SOD1) protein is mutated in approximately 15% of familial amyotrophic lateral sclerosis (ALS) and 3% of sporadic ALS. We identified a novel mutation in SOD1 in a man who presented at age 49 with lower limb stiffness, and at age 53, a spastic paraparesia with distal muscular atrophy in the lower limbs and fasciculations in the quadriceps. A diagnosis of ALS was established. Eleven years after disease onset his condition continues gradually and slowly to deteriorate. The heterozygous mutation observed in exon 2 resulted in a valine to alanine substitution at position 31 in the ß-barrel domain of the SOD1 protein. Functional analysis in NSC34 cells showed that the overexpression of the mutant form of SOD1(V31A) induced aggregates and decreased cell viability. This mutation is located outside of the regions carrying most of the ALS-related mutations (i.e., the catalytic center, the region of dimerization, and the loops between the ß-strands of the ß-barrel). In conclusion, we identified a novel SOD1 mutation in a patient with slow disease progression and supported the idea that different SOD1 mutations can lead to distinct ALS phenotypes.

A functional tetranucleotide (AAAT) polymorphism in an Alu element in the NF1 gene is associated with mental retardation.

Mental retardation (MR) is frequent in neurofibromatosis type 1 (NF1). Allele 5 of a tetranucleotide polymorphism in an Alu element (GXAlu) localized in intron 27b of the NF1 gene has previously been associated with autism. We considered that the microsatellite GXAlu could also represent a risk factor in MR without autism. We developed a rapid method for genotyping by non-denaturing HPLC and assayed the allelic variation of GXAlu marker on in vitro gene expression in Cos-7 cells. A French population of 157 individuals (68 non syndromic non familial MR (NS-MR) patients diagnosed in the University Hospital of Tours; 89 controls) was tested in a case-control assay. We observed a significant association (χ(2)=7.96; p=0.005) between alu4 carriers (7 AAAT repeats) and MR (OR: 7.86; 95% C.I.: 2.13-28.9). The relative in vitro expression of a reporter gene encoding chloramphenicol acetyl transferase (CAT) was higher for alu4 and alu5, suggesting a regulation effect for these alleles on gene expression in vivo. Our results showed an association with a polymorphism regulating the NF1 gene or other genes during brain development.

Study of the serotonin transporter (SLC6A4) and BDNF genes in French patients with non syndromic mental deficiency.

BACKGROUND: Mental deficiency has been linked to abnormalities in cortical neuronal network connectivity and plasticity. These mechanisms are in part under the control of two interacting signalling pathways, the serotonergic and the brain-derived neurotrophic (BDNF) pathways. The aim of the current paper is to determine whether particular alleles or genotypes of two crucial genes of these systems, the serotonin transporter gene (SLC6A4) and the brain-derived neurotrophic factor gene (BDNF), are associated with mental deficiency (MD). METHODS: We analyzed four functional polymorphisms (rs25531, 5-HTTLPR, VNTR, rs3813034) of the SLC6A4 gene and one functional polymorphism (Val66 Met) of the BDNF gene in 98 patients with non-syndromic mental deficiency (NS-MD) and in an ethnically matched control population of 251 individuals. RESULTS: We found no significant differences in allele and genotype frequencies in the five polymorphisms studied in the SLC6A4 and BDNF genes of NS-MD patients versus control patients. While the comparison of the patterns of linkage disequilibrium (D') in the control and NS-MD populations revealed a degree of variability it did not, however, reach significance. No significant differences in frequencies of haplotypes and genotypes for VNTR/rs3813034 and rs25531/5-HTTLPR were observed. CONCLUSION: Altogether, results from the present study do not support a role for any of the five functional polymorphisms of SLC6A4 and BDNF genes in the aetiology of NS-RM. Moreover, they suggest no epistatic interaction in NS-MD between polymorphisms in BDNF and SLC6A4. However, we suggest that further studies on these two pathways in NS-MD remain necessary.

Transcriptional silencing of the TFPI-2 gene by promoter hypermethylation in choriocarcinoma cells.

Tissue factor pathway inhibitor-2 (TFPI-2), a Kunitz-type serine proteinase inhibitor associated with the extracellular matrix, has been shown to reduce tumor invasion. In the present study we identified the presence of a complete CpG island region spanning exon 1 and the three transcription initiation sites. We demonstrate that DNA demethylation by 5'-aza-2'-deoxycytidine restores TFPI-2 transcription in JAR choriocarcinoma cells. The effect of in vitro DNA methylation on TFPI-2 promoter function was also confirmed with TFPI-2/luciferase promoter constructs. Finally, we determined the precise methylation status of CpG sites of the TFPI-2 promoter in normal and tumor trophoblast cells using the bisulfite genomic sequencing method. We conclude that hypermethylation of the TFPI-2 gene is correlated with transcriptional silencing and that the TFPI-2 gene may be a candidate tumor suppressor gene.