Buffering of segmental and chromosomal aneuploidies in Drosophila melanogaster

Chromosomal instability which involves deletion and duplication of chromosomes or chromosome parts is a common feature of cancers, and deficiency screens are commonly used as a method to find genes involved in different biological pathways. Still, how gene expression from whole chromosomes or large chromosomal domains is affected by deficiencies, duplications or chromosome loss is largely unknown. Using expression microarrays of deficiency hemizygotes and a duplication hemizygote we show that expressed genes are significantly buffered when present in a deficiency hemizygote and that the buffering effect is general and not mainly caused by feedback regulation of individual genes. Differentially expressed genes are in general better buffered than ubiquitously expressed genes when present in one copy. When present in three copies, differentially expressed genes are in general less buffered than ubiquitously expressed genes. Furthermore, we show that the 4th chromosome is compensated in response to dose differences. Our results suggest that general mechanisms exist to stimulate and to repress gene expression of aneuploidy regions and on the 4th chromosome this compensation is mediated by POF (Painting of Fourth).

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