Thomassin, H. | bioRxiv Science

bioRxiv2025

Genome-wide screen for deficiencies modifying Cyclin G-induced developmental instability in Drosophila melanogaster.

Despite long-lasting interest and research efforts, the genetic bases of developmental stability - the robustness to developmental noise - and its most commonly used estimator, fluctuating asymmetry (FA), remain poorly understood. The Drosophila melanogaster Cyclin G gene (CycG) encodes a transcriptional cyclin that regulates growth and the cell cycle. Over-expression of a potentially more stable isoform of the protein (deleted of a PEST-rich domain, hereafter called CycG{Delta}P) induces extreme wing size and shape FA (i.e. high developmental noise), indicating a major disruption of developmental stability. Previous attempts to identify the genetic bases of FA have been impeded by the constitutively low level of developmental noise, limiting the power to detect any effect. Here, we leverage the extreme developmental instability induced by overexpression of CycG{Delta}Pto explore the genetic bases of FA: we perform a genome-wide screen for deficiencies that enhance or reduce CycG{Delta}P-induced wing FA. 499 deficiencies uncovering 90% of the euchromatic genome were combined with a recombinant chromosome expressing CycG{Delta}P. We identified 13 and 16 deficiencies that respectively enhance and decrease FA. Analysis of mutants for some genes located in these deficiencies shows that Cyclin G ensures homogeneous growth of organs in synergy with the major morphogens of the wing, Dpp and Wg, as well as the Hippo and InR/TOR pathways. They also reveal that CycG{Delta}P-induced FA involves Larp, a potential direct interactor of Cyclin G, that regulates translation at the mitochondrial membrane. This opens up new research perspectives for understanding developmental stability, suggesting a significant role for mitochondrial activity.

genetics↗

bioRxiv2021

Single amino-acid mutation in the Drosophila melanogaster ribosomal protein uL11: an insight in its transcriptional activity

The ribosomal protein uL11 is located at the basis of the ribosome P-stalk and plays a paramount role in translational efficiency. In addition, no mutant for uL11 is available suggesting that this gene is haplo-insufficient as many other Ribosomal Protein Genes (RPGs). We have previously shown that overexpression of Drosophila melanogaster uL11 enhances the transcription of many RPGs and Ribosomal Biogenesis genes (RiBis) suggesting that uL11 might globally regulate the level of translation through its transcriptional activity. Moreover, uL11 trimethylated on lysine 3 (uL11K3me3) interacts with the chromodomain of the Enhancer of Polycomb and Trithorax Corto, and both proteins co- localize with RNA Polymerase II at many sites on polytene chromosomes. These data have led to the hypothesis that the N-terminal end of uL11, and more particularly the trimethylation of lysine 3, supports the extra-ribosomal activity of uL11 in transcription. To address this question, we mutated the lysine 3 codon using a CRISPR/Cas9 strategy and obtained several lysine 3 mutants. We describe here the first mutants of D. melanogaster uL11. Unexpectedly, the uL11K3A mutant, in which the lysine 3 codon is replaced by an alanine, displays a genuine Minute phenotype known to be characteristic of RPG deletions (longer development, low fertility, high lethality, thin and short bristles) whereas the uL11K3Y mutant, in which the lysine 3 codon is replaced by a tyrosine, is unaffected. In agreement, the rate of translation decreases in uL11K3A but not in uL11K3Y. Co-immunoprecipitation experiments show that the interaction between uL11 and the Corto chromodomain is impaired by both mutations. RNA- seq analysis from wing imaginal discs shows enrichment in the GO categories "glutathione metabolism" for up-regulated genes in both uL11K3A and uL11K3Y mutants and "regulation of transcription" for down-regulated genes in uL11K3A only. Analysis of the cis-regulatory sequences of these genes suggests that uL11 might regulate transcription of target genes in concert with the couple of transcription factors Mad/Med that mediate response to the Bone Morphogenetic Protein (BMP) signaling pathway.

developmental biology↗