Project description:Heat shock proteins (Hsps), in particular Hsp70, play a central role in proteostasis in eukaryotic cells. Due to its chaperone properties, Hsp70 is involved in various processes both after stress and under normal physiological conditions. In contrast to mammals and many Diptera species, members of the Hsp70 family in Drosophila are constitutively synthesized at a low level and undergo dramatic induction after temperature elevation or other forms of stress. In the courtship suppression paradigm used in this study, Drosophila males that have been repeatedly rejected by mated females during courtship are less likely than naive males to court other females. Although numerous genes with known function were identified to play important roles in long-term memory, there is, to the best of our knowledge, no direct evidence implicating Hsp70 in this process. To eliminate this gap, we used D. melanogaster strains containing different hsp70 copy numbers, including strains carrying a deletion of all six hsp70 genes. Our investigations exploring the memory of courtship rejection paradigm demonstrated that a low constitutive level of Hsp70 is required for learning and the formation of short and long-term memories in males. The performed transcriptomic studies demonstrate that males with different hsp70 copy numbers differ significantly in the expression of a few definite groups of genes involved in mating and reproduction, as well as methionine metabolism and immune genes in response to rejection. Specifically, our analysis reveals several major pathways that depend on the presence of hsp70 copies in the genome and apparently participate in memory formation and consolidation, including the cAMP signalling cascade.
Project description:Disruption of learning and memory can occur for a number of reasons including chronic alcohol abuse, head injury, anoxia, and various neurodegenerative disorders such as Alzheimer's disease. An understanding of the basic mechanisms underlying learning and memory is essential for prevention and treatment of such brain disorders. Recent studies unequivocally demonstrated the astonishing similarities in the basic mechanisms of learning and memory between divergent species, indicating that studies of experimentally tractable model organisms with relatively simpler nervous systems are likely to produce valuable information that will facilitate our understanding of learning and memory in higher organisms. We are studying the experience-dependent modification in Drosophila male courtship as a physiologically relevant model of learning and memory. The genome-scale gene-profiling analysis in this model system should provide us the basic information about learning-induced changes in gene expression, which will be the foundation of our future studies to identify genes and genetic pathways specifically involved in the formation of long-term memory. The proposed gene-profiling experiment is designed to identify candidate genes and genetic pathways involved in the formation of long-term memory in the Drosophila courtship conditioning. The specific aims of this project are to: 1) compare gene expression profiles between the naive and trained wild type males using the GeneChip Drosophila Genome 2.0 Arrays and identify genes that are up- or down-regulated in the fly head immediately or 24-hr after the male fly is exposed to the condition where the long-term courtship memory is established (i.e., paired with a mated female for 7 hrs), 2) carry out the same analysis for the per null mutant males, 3) compare the identified genes between the 0 and 24-hr after training as well as the wild type and per mutant males, 4) identify candidate genes which might be involved in the long-term memory formation either upstream or downstream of per, 5) classify the candidate genes according to their putative cellular function and discern the possible genetic pathways necessary for the long-term memory formation. When a male fly is presented with a previously mated female, he will initially court her vigorously but his courtship activity is reduced over time. Subsequently, when paired with a virgin female, the male will display a reduced amount of courtship compared with naïve males with no prior courtship experience. This modification of courtship is called âcourtship conditioningâ. We found that this type of courtship memory lasts at least 5 days when a male is trained with a mated female for 7 hrs. We have also found that the period gene (per) that is involved in circadian rhythm regulation plays a critical role in the formation of long-term, but not short-term, courtship memory. Our hypotheses are 1) the long-lasting memory in 7 h-trained males is accompanied with characteristic temporal changes in gene expression in the brain, 2) per mutant males are defective in regulation of critical genes involved in long-term courtship memory, 3) the memoryârelated changes in gene expression can be detected by comparing total head transcript levels between trained and naïve as well as the wild type and the per mutant males using the Affymetrix microarray. Two fly strains, a wild type Oregon R (OR) and a null mutant allele of per (per01) with the OR background for the second and third chromosomes, will be used. Virgin males and females will be collected without anesthesia within 6 hrs after eclosion and maintained individually in vials until experiments. Mated wild type females will be prepared by crossing to the wild type males the night before they are used for conditioning males. All flies will be raised at 25oC in a 12 h light/12 h dark cycle and the following behavioral experiments will be carried out during daytime. For courtship conditioning, a 3 day-old virgin male (either OR or per01) will be placed with a mated OR female in a conditioning chamber (15 mm x 5 mm in depth) containing fly food. As a control, a virgin male will be introduced into another conditioning chamber without a mated female. Seven hours after the male is introduced into the chamber, he will be anesthetized under CO2 gas or transferred to a new vial. For the anesthetized male, the head will be immediately excised and frozen with liquid nitrogen. The male fly transferred to a new vial will be decapitated 24 hrs after the end of the 7-hr training. Approximately thirty fly heads will be pooled for each of the 8-genotype/treatment groups, i.e., Oregon R 0-hr and 24-hr after conditioning, per01 0-hr and 24-hr after conditioning, in addition to the corresponding four naïve controls. Total RNA will be extracted from the pooled heads using the TRIzol Reagent (Life Technologies) followed by an RNeasy (Qiagen) cleanup step and a DNAase I digestion step. After purification, the RNA will be resuspended in DEPC water and the absorbance will be checked at 260 and 280 nm for determination of sample purity and concentration. The GeneChip Drosophila Genome 2.0 Arrays will be used to quantify the levels of transcripts in each sample.
Project description:Disruption of learning and memory can occur for a number of reasons including chronic alcohol abuse, head injury, anoxia, and various neurodegenerative disorders such as Alzheimer’s disease. An understanding of the basic mechanisms underlying learning and memory is essential for prevention and treatment of such brain disorders. Recent studies unequivocally demonstrated the astonishing similarities in the basic mechanisms of learning and memory between divergent species, indicating that studies of experimentally tractable model organisms with relatively simpler nervous systems are likely to produce valuable information that will facilitate our understanding of learning and memory in higher organisms. We are studying the experience-dependent modification in Drosophila male courtship as a physiologically relevant model of learning and memory. The genome-scale gene-profiling analysis in this model system should provide us the basic information about learning-induced changes in gene expression, which will be the foundation of our future studies to identify genes and genetic pathways specifically involved in the formation of long-term memory. The proposed gene-profiling experiment is designed to identify candidate genes and genetic pathways involved in the formation of long-term memory in the Drosophila courtship conditioning. The specific aims of this project are to: 1) compare gene expression profiles between the naïve and trained wild type males using the GeneChip Drosophila Genome 2.0 Arrays and identify genes that are up- or down-regulated in the fly head immediately or 24-hr after the male fly is exposed to the condition where the long-term courtship memory is established (i.e., paired with a mated female for 7 hrs), 2) carry out the same analysis for the per null mutant males, 3) compare the identified genes between the 0 and 24-hr after training as well as the wild type and per mutant males, 4) identify candidate genes which might be involved in the long-term memory formation either upstream or downstream of per, 5) classify the candidate genes according to their putative cellular function and discern the possible genetic pathways necessary for the long-term memory formation. When a male fly is presented with a previously mated female, he will initially court her vigorously but his courtship activity is reduced over time. Subsequently, when paired with a virgin female, the male will display a reduced amount of courtship compared with naïve males with no prior courtship experience. This modification of courtship is called “courtship conditioning”. We found that this type of courtship memory lasts at least 5 days when a male is trained with a mated female for 7 hrs. We have also found that the period gene (per) that is involved in circadian rhythm regulation plays a critical role in the formation of long-term, but not short-term, courtship memory. Our hypotheses are 1) the long-lasting memory in 7 h-trained males is accompanied with characteristic temporal changes in gene expression in the brain, 2) per mutant males are defective in regulation of critical genes involved in long-term courtship memory, 3) the memory–related changes in gene expression can be detected by comparing total head transcript levels between trained and naïve as well as the wild type and the per mutant males using the Affymetrix microarray. Two fly strains, a wild type Oregon R (OR) and a null mutant allele of per (per01) with the OR background for the second and third chromosomes, will be used. Virgin males and females will be collected without anesthesia within 6 hrs after eclosion and maintained individually in vials until experiments. Mated wild type females will be prepared by crossing to the wild type males the night before they are used for conditioning males. All flies will be raised at 25oC in a 12 h light/12 h dark cycle and the following behavioral experiments will be carried out during daytime. For courtship conditioning, a 3 day-old virgin male (either OR or per01) will be placed with a mated OR female in a conditioning chamber (15 mm x 5 mm in depth) containing fly food. As a control, a virgin male will be introduced into another conditioning chamber without a mated female. Seven hours after the male is introduced into the chamber, he will be anesthetized under CO2 gas or transferred to a new vial. For the anesthetized male, the head will be immediately excised and frozen with liquid nitrogen. The male fly transferred to a new vial will be decapitated 24 hrs after the end of the 7-hr training. Approximately thirty fly heads will be pooled for each of the 8-genotype/treatment groups, i.e., Oregon R 0-hr and 24-hr after conditioning, per01 0-hr and 24-hr after conditioning, in addition to the corresponding four naïve controls. Total RNA will be extracted from the pooled heads using the TRIzol Reagent (Life Technologies) followed by an RNeasy (Qiagen) cleanup step and a DNAase I digestion step. After purification, the RNA will be resuspended in DEPC water and the absorbance will be checked at 260 and 280 nm for determination of sample purity and concentration. The GeneChip Drosophila Genome 2.0 Arrays will be used to quantify the levels of transcripts in each sample. Keywords: other
Project description:I hypothesized that social interactions, such as those involved in reproductive behaviors, would lead to immediate and assayable changes in gene expression that may have important effects on individual reproductive success and fitness through alterations in physiology or via short-term or long-term changes in nervous system function. Experiment Overall Design: Four-day males were exposed or mock-exposed to a virgin female fly for 5 min. Exposed males that courted as well as mock-exposed males were collected for RNA extraction. Three samples for each treatment were hybridized to Affymetrix Drosophila Genome arrays for a total of 6 arrays.
Project description:Space travel presents unlimited opportunities for exploration and discovery, but requires a more complete understanding of the immunological consequences of long-term exposure to the conditions of spaceflight. To understand these consequences better and to contribute to design of effective countermeasures, we used the Drosophila model to compare innate immune responses to bacteria and fungi in flies that were either raised on earth or in outer space aboard the NASA Space Shuttle Discovery (STS-121). Microarrays were used to characterize changes in gene expression that occur in response to infection by bacteria and fungus in drosophila that were either hatched and raised in outer space (microgravity) or on earth (normal gravity).
Project description:To obtain a comprehensive view of genes contributing to long-term memory we performed mRNA sequencing from single Drosophila heads following behavioral training that produces long-lasting memory.