Novel deletion of the E3A ubiquitin protein ligase gene detected by multiplex ligation-dependent probe amplification in a patient with Angelman syndrome.

Angelman syndrome (AS) is a severe neurobehavioural disorder caused by failure of expression of the maternal copy of the imprinted domain located on 15q11-q13. There are different mechanisms leading to AS: maternal microdeletion, uniparental disomy, defects in a putative imprinting centre, mutations of the E3 ubiquitin protein ligase (UBE3A) gene. However, some of suspected cases of AS are still scored negative to all the latter mutations. Recently, it has been shown that a proportion of negative cases bear large deletions overlapping one or more exons of the UBE3A gene. These deletions are difficult to detect by conventional gene-scanning methods due to the masking effect by the non-deleted allele. In this study, we have used for the first time multiplex ligation-dependent probe amplification (MLPA) and comparative multiplex dosage analysis (CMDA) to search for large deletions affecting the UBE3A gene. Using this approach, we identified a novel causative deletion involving exon 8 in an affected sibling. Based on our results, we propose the use of MLPA as a fast, accurate and inexpensive test to detect large deletions in the UBE3A gene in a small but significant percentage of AS patients.

A missense mutation in the coiled-coil domain of the KIF5A gene and late-onset hereditary spastic paraplegia.

BACKGROUND: To our knowledge, up to now, only 2 mutations in the KIF5A gene, a member of the kinesin superfamily, have been identified as the molecular cause of early-onset autosomal dominant hereditary spastic paraparesis (ADHSP). OBJECTIVE: To assess the genetic defect in a family with late-onset ADHSP. PATIENTS AND METHODS: Only the proband agreed to undergo complete neurological testing and mutational analysis. The proband was screened for mutations in the spastin, atlastin, NIPA1, and KIF5A genes, either by denaturing high-performance liquid chromatography or sequence analysis. RESULTS: The history of the family was consistent with ADHSP characterized by late onset of the disease. Mutational analysis results were negative for the spastin, atlastin, and NIPA1 genes but identified a missense mutation (c.1082C>T) in the coiled-coil coding region of the KIF5A gene. CONCLUSIONS: This finding enlarges the phenotypic spectrum of ADHSP linked to KIF5A and enhances the role of that gene in the epidemiology of this disease. We propose that the KIF5A gene should be routinely analyzed in patients with hereditary spastic paraplegia negative for spastin and atlastin mutations.

Two novel mutations in the spastin gene (SPG4) found by DHPLC mutation analysis.

The most common form of autosomal dominant hereditary spastic paraplegia is caused by mutations in the gene encoding spastin (SPG4), a member of the AAA family of ATPases. In the current study, we designed a denaturing high-performance liquid chromatography based protocol for the analysis of the SPG4 gene. Using this method, we detected two novel missense mutations, 1375A > G (R459G) and 1378C > T (R460C), one previously described five bases deletion (1215_1219del) and three polymorphic changes. This study suggests that denaturing high-performance liquid chromatography would be a fast and reliable tool in the investigation of the molecular defects in the SPG4 gene.

Mutational analysis of the ATRX gene by DGGE: a powerful diagnostic approach for the ATRX syndrome.

Molecular defects affecting the ATRX gene lead to the ATRX syndrome (alpha thalassemia/mental retardation syndrome, X-linked), characterized by severe mental retardation, microcephaly, distinct facial dysmorphism, and genital abnormalities, as well as a wide spectrum of other pathological features. Alpha thalassemia is frequent but does not represent a constant characteristic of the syndrome. An expanding phenotype of the ATRX gene (a RAD54 homologue encoding a putative zinc-finger helicase) has been demonstrated as a result of the association of single mutations with specific X-linked mental retardation syndromes. To date, mutational analysis of the gene has been based on direct DNA sequencing or using methods with a lower detection rate. In this paper, we present a broad-range DGGE method for single-step mutation scanning of the entire open reading frame (ORF) and canonical splice sites of the gene. Using this method, we successfully identified five novel sequence changes in the ATRX gene, including four missense mutations (K1733E, R2085C, D2136N, T2169A) and one polymorphism (IVS5+35G>A).