A candidate gene for autoimmune myasthenia gravis.

OBJECTIVE: We sought to identify a causative mutation in a previously reported kindred with parental consanguinity and 5 of 10 siblings with adult-onset autoimmune myasthenia gravis. METHODS: We performed genome-wide homozygosity mapping, and sequenced all known genes in the one region of extended homozygosity. Quantitative and allele-specific reverse transcriptase PCR (RT-PCR) were performed on a candidate gene to determine the RNA expression level in affected siblings and controls and the relative abundance of the wild-type and mutant alleles in a heterozygote. RESULTS: A region of shared homozygosity at chromosome 13q13.3-13q14.11 was found in 4 affected siblings and 1 unaffected sibling. A homozygous single nucleotide variant was found in the 3'-untranslated region of the ecto-NADH oxidase 1 gene (ENOX1). No other variants likely to be pathogenic were found in genes in this region or elsewhere. The ENOX1 sequence variant was not found in 764 controls. Quantitative RT-PCR showed that expression of ENOX1 decreased to about 20% of normal levels in lymphoblastoid cells from individuals homozygous for the variant and to about 50% in 2 unaffected heterozygotes. Allele-specific RT-PCR showed a 55%-60% reduction in the level of the variant transcript in heterozygous cells due to reduced mRNA stability. CONCLUSION: These results indicate that this sequence variant in ENOX1 may contribute to the familial autoimmune myasthenia in these patients.

Aberrant histone acetylation, altered transcription, and retinal degeneration in a Drosophila model of polyglutamine disease are rescued by CREB-binding protein.

Sequestration of the transcriptional coactivator CREB-binding protein (CBP), a histone acetyltransferase, has been implicated in the pathogenesis of polyglutamine expansion neurodegenerative disease. We used a Drosophila model to demonstrate that polyglutamine-induced neurodegeneration is accompanied by a defect in histone acetylation and a substantial alteration in the transcription profile. Furthermore, we demonstrate complete functional and morphological rescue by up-regulation of endogenous Drosophila CBP (dCBP). Rescue of the degenerative phenotype is associated with eradication of polyglutamine aggregates, recovery of histone acetylation, and normalization of the transcription profile. These findings suggest that histone acetylation is an early target of polyglutamine toxicity and indicate that transcriptional dysregulation is an important part of the pathogenesis of polyglutamine-induced neurodegeneration.