Drosophila Models of Polyglutamine Diseases

The fruit fly, Drosophila melanogaster , has been used extensively as an experimental model organism since the beginning of the last century. More recently, the concept of large-scale genetic mutagenesis screens has been applied. In the first such screen, 15 loci spread throughout the genome were identified based on a common phenotype of disruption of embryonic segmentation (1 ). This seminal work led to identification of orthologous genes that are important in human embryonic development. Mutations in these human genes have also been found to lead to congenital malformations. As one example, Waardenburg’s syndrome is a human autosomal dominant disease that results in deafness and pigmentation defects in the eye, and is caused by mutations in the human homolog of the Drosophila paired gene, PAX-3 (2 ). Recently, comparative genomic analysis of the completed Drosophila genome has revealed that more than 60% of human disease genes are represented by Drosophila homologs (3 ,4 ). This further fosters the use of Drosophila as a model organism to study processes relevant to human disease conditions.