Buffering and proteolysis are induced upon segmental haploidy in Drosophila melanogaster.

Aneuploidy, i.e., variation in the number of individual chromosomes (chromosomal aneuploidy) or chromosome segment (segmental aneuploidy) is associated with developmental abnormalities and reduced fitness in all species examined, is the leading cause of miscarriages and mental retardations and a hallmark of cancer. Despite their documented importance in disease the effects of aneuploidies on the transcriptome remains largely unknown. Here we have examined the expression output in seven deficiency heterozygotes as single deficiencies and in all pairwise combinations. The results show that genes in one copy are buffered, i.e., are expressed above the expected 50% expression level compared to wild type and the buffering is general and not influenced by additional haploid regions. Long genes are significantly better buffered than short genes and our analysis suggests that gene length is the primary determinant for the degree of buffering. For short genes the degree of buffering depends on expression level and expression pattern. Furthermore, the results show that in deficiency heterozygotes the expression of genes involved in proteolysis is enhanced and negatively correlates with the degree of buffering. Our results suggest that proteolysis is a general response induced by aneuploidy.

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Lundberg LE, Figueiredo ML, Stenberg P, Larsson J