Drosophila kdm5 140 Mutant and Ecdysone Hormone Pathway

Science Center, Bent Corridor

The KDM5 family of histone demethylases is important in cancer research as well as research on intellectual disability. These proteins are histone modifiers that remove methyl groups from lysine 4 on histone 3 (H3K4) at the transcriptional start site of actively transcribed genes. In addition to its demethylase activity, KDM5 proteins have other domains that influence transcription. One of these is a PHD motif that binds to H3K4me3 and functions independently of the JmjC domain-encoded demethylase activity. The PHD domains of two mammalian KDM5 proteins, KDM5A and KDM5B, affect the activity and transcription of the estrogen and androgen nuclear receptors respectively, which has been linked to breast and prostate cancer progression. To examine the link between KDM5 and nuclear hormone function, we are using the model organism Drosophila, which encodes a single, essential kdm5 gene. Ecdysone is the steroid hormone in insects that directs postembryonic development. The level of ecdysone spikes between different stages of the Drosophila life cycle and triggers the transcription of many primary and secondary response genes the regulate development through these stages. Ecdysone binds to the EcR/USP nuclear receptor complex in order to initiate transcription of its target genes. Ecdysone also promotes lipid metabolism during different stages of development, providing the energy for growth and metamorphosis. The Drosophila kdm5 null mutant, kdm5 140 , generated within our lab is developmentally delayed and appears to have more lipid accumulation than the wild type. For these reasons we decided to test whether kdm5 140 mutants show defects in the in the ecdysone pathway in order to gain a better understanding of the interaction between KDM5 and nuclear hormones. Results from the Nile Red staining on 3 rd instar larval fat bodies demonstrates elevated levels of lipid accumulation in kdm5 mutants compared to the wild type. Quantitative real-time PCR data collected show a statistically significant decrease in two major ecdysone primary response genes Br-C and E75. These results suggest a possible connection between KDM5 and the ecdysone pathway. Additional data show that EcR expression is similar in UAS- kdm5 RNAI cells and wild type cells, suggesting that KDM5 may not affect of EcR itself, but may affect a different portion of the ecdysone pathway.