How organs achieve their appropriate size represents a fundamental question in biology.Chromatin plays an important role in regulating gene expression during development, including the determination of organ size. In Drosophila melanogaster, the wings provide an ideal model system to explore the molecular mechanisms underlying organ growth.

Here, we demonstrate that deficiency of a key chromatin regulator, the histone demethylase dLsd1 leads to reduced wing size due to a decreased cell number. Our work shows that dLsd1 depletion causes cell cycle arrest and apoptosis associated to an increased DNA damage. Through genomic analysis, we show that these phenotypes correlate with increased transposon expression and mobilization. Conversely, administering a reverse transcriptase inhibitor to dLsd1 null mutants results in partial restoration of normal wing size concomitant with reduced transposon mobilization.

In summary, our work shows the critical role of dLsd1 in modulating Drosophila wing size through the suppression of transposon expression and mobility.