Drosophila maleless gene counteracts X global aneuploid effects in males

The loss of the entire X chromosome in Drosophila males generates a genome-wide aneuploid effect. We have employed a systems biology approach (microarray) to investigate the global aneuploid effect of the maleless (mle) mutation that disrupts the binding of male specific lethal (MSL) proteins that function in dosage compensation. A large number of the genes (144) that encode a broad spectrum of cellular transport proteins and transcription factors are located mainly in the autosomes of Drosophila melanogaster. We found several such targets to be sensitive to the aneuploid effect and conserved with the X chromosome in primitive Drosophila species and Anopheles gambiae. During evolution, they shifted gradually from their X-chromosomal positions to the autosomes in the species D. melanogaster, suggesting that the counteraction of trans-acting regulatory modifiers and their targets in two separate chromosomes is evolutionarily advantageous. These findings suggest a remarkable and previously unexpected level of complexity favoring natural compensation for the aneuploid effect. We propose that the MSL complex functions in dosage compensation in two separate steps. Initially, X-linked genes including X-linked trans-acting modifiers are hyperactivated in dosage compensated males. Later, these compensated modifiers eventually mitigate inverse aneuploid effects for the equality in expression of their autosomal targets in males and females.

Microarray data are available at the Gene Expression Omnibus (GEO) web deposit of National Centre for Biotechnology Information (NCBI) with the accession number GSE78227.