Project description:Songbirds possess one of the most accessible neural systems for the study of brain mechanisms of behavior. However, neuroethological studies in songbirds have been limited by the lack of high-throughput molecular resources and gene manipulation tools. To overcome this limitation, here we generated a resource of full-length cDNAs for gene expression analyses and gene manipulation in songbirds. We constructed 21 regular, normalized, and subtracted full-length cDNA libraries from brains of songbirds in 57 behavioral and developmental conditions in an attempt to clone as much of the brain transcriptome as possible. From these libraries ~14,000 transcripts were isolated, representing an estimated 4,738 genes, or ~40% of the genes expressed in the brain. With these cDNAs, we created a novel draft transcriptome database and large scale songbird brain cDNA microarrays. We used the arrays to reveal a set of 33 genes regulated in brain vocal nuclei by singing behavior. These genes clustered into 4 anatomical and 6 temporal brain expression patterns. Their functions spanned broad range of cellular and molecular categories, including signal transduction, trafficking, structural, and synaptically released molecules. With the full-length cDNAs, we over-expressed proteins of representative singing-regulated genes in vocal nuclei in the absence of singing, using a lentiviral vector system. This resource now allows investigators to comprehensively study molecular neuroethological mechanisms of behavior. Keywords: songbird, zebra finch, transcriptome, learned vocalization, immediate early genes, lentivirus
Project description:Upon starvation, Dictyostelium discoideum cells halt cell proliferation, aggregate into multicellular organisms, form migrating slugs, and undergo morphogenesis into fruiting bodies while differentiating into dormant spores and dead stalk cells. At almost any developmental stage cells can be forced to dedifferentiate when they are dispersed and diluted into nutrient broth. However, migrating slugs can traverse lawns of bacteria for days without dedifferentiating, ignoring abundant nutrients and continuing development. We now show that developing Dictyostelium cells revert to the growth phase only when bacteria are supplied during the first 4 to 6 h of development but that after this time, cells continue to develop regardless of the presence of food. We postulate that the cells' inability to revert to the growth phase after 6 h represents a commitment to development. We show that the onset of commitment correlates with the cells' loss of phagocytic function. By examining mutant strains, we also show that commitment requires extracellular cyclic AMP (cAMP) signaling. Moreover, cAMP pulses are sufficient to induce both commitment and the loss of phagocytosis in starving cells, whereas starvation alone is insufficient. Finally, we show that the inhibition of development by food prior to commitment is independent of contact between the cells and the bacteria and that small soluble molecules, probably amino acids, inhibit development during the first few hours and subsequently the cells become unable to react to the molecules and commit to development. We propose that commitment serves as a checkpoint that ensures the completion of cooperative aggregation of developing Dictyostelium cells once it has begun, dampening the response to nutritional cues that might inappropriately block development.
Project description:Differential expression of Dictyostelium discoideum AX2 upon infection with wt L. pneumophila JR32 vs. uninfected 6h p.i. (timecourse experiment)