Project description:Dictyostelium discoideum is a useful model for studying mechanisms of cisplatin drug sensitivity. Our previous findings, that mutations in sphingolipid-metabolism genes confer cisplatin resistance in D. discoideum and in human cells, raised interest in the resistance mechanisms and their implications for cisplatin chemotherapy. Here we used expression microarrays to monitor physiological changes and to identify pathways that are affected by cisplatin treatment of D. discoideum. We found over 400 genes whose regulation was altered by cisplatin treatment of wild type cells, including groups of genes that participate in cell proliferation and in nucleotide and protein metabolism. These findings show that the cisplatin response is orderly and multifaceted. Transcriptional profiling of two isogenic cisplatin-resistant mutants, impaired in different sphingolipid metabolism steps, showed that the effect of cisplatin treatment was greater than the effect of the mutations, indicating that cisplatin-resistance in the mutants is due to specific abilities to overcome the drug effects rather than to general drug insensitivity. Nevertheless, the mutants exhibited significantly different responses to cisplatin compared to the parent and over 200 genes accounted for that difference. We mutated some of the cisplatin-response genes and found that the mutants had altered drug sensitivity. These findings reveal the power of this system to identify pathways and genes that are affected by drugs and mutations. Our data illustrate how modeling complex cellular responses to drugs in genetically stable and tractable systems can uncover new targets with the potential for improving chemotherapy. Keywords: Dictyostelium discoideum, cisplatin treatment, transcriptional profiles, physiological changes
Project description:ATP-binding cassette (ABC) transporters can translocate a broad spectrum of molecules across the cell membrane including physiological cargo and toxins. ABC transporters are known for the role they play in resistance towards anticancer agents in chemotherapy of cancer patients. There are 68 ABC transporters annotated in the genome of the social amoeba Dictyostelium discoideum. We have characterized more than half of these ABC transporters through a systematic study of mutations in their genes. We have analyzed morphological and transcriptional phenotypes for these mutants during growth and development and found that most of the mutants exhibited rather subtle phenotypes. A few of the genes may share physiological functions, as reflected in their transcriptional phenotypes. Since most of the abc-transporter mutants showed subtle morphological phenotypes, we utilized these transcriptional phenotypes to identify genes that are important for development by looking for transcripts whose abundance was unperturbed in most of the mutants. We found a set of 668 genes that includes many validated D. discoideum developmental genes. We have also found that abcG6 and abcG18 may have potential roles in intercellular signaling during terminal differentiation of spores and stalks. Transcriptional phenotyping during development of abc transporter mutants in Dictyostelium discoideum