A developmental genetic analysis of the lysine demethylase KDM2 mutations in Drosophila melanogaster

Post-translational modification of histones plays essential roles in the transcriptional regulation of genes in eukaryotes. Methylation on basic residues of histones is regulated by histone methyltransferases and histone demethylases, and misregulation of these enzymes has been linked to a range of diseases such as cancer. Histone lysine demethylase 2 (KDM2) family proteins have been shown to either promote or suppress tumorigenesis in different human malignancies. However, the roles and regulation of KDM2 in development are poorly understood, and the exact roles of KDM2 in regulating demethylation remain controversial. Since KDM2 proteins are highly conserved in multicellular animals, we analyzed the KDM2 ortholog in Drosophila. We have observed that dKDM2 is a nuclear protein and its level fluctuates during fly development. We generated three deficiency lines that disrupt the dKdm2 locus, and together with 10 transposon insertion lines within the dKdm2 locus, we characterized the developmental defects of these alleles. The alleles of dKdm2 define three phenotypic classes, and the intragenic complementation observed among these alleles and our subsequent analyses suggest that dKDM2 is not required for viability. In addition, loss of dKDM2 appears to have rather weak effects on histone H3 lysine 36 and 4 methylation (H3K36me and H3K4me) in the third instar wandering larvae, and we observed no effect on methylation of H3K9me2, H3K27me2 and H3K27me3 in dKdm2 mutants. Taken together, these genetic, molecular and biochemical analyses suggest that dKDM2 is not required for viability of flies, indicating that dKdm2 is likely redundant with other histone lysine demethylases in regulating normal development in Drosophila.