Browsing by Subject "behavioral"
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Item Annotation of Expressed Sequence Tags for the East African Cichlid Fish Astatotilapia Burtoni and Evolutionary Analyses of Cichlid ORFs(2008-02) Salzburger, Walter; Renn, Susan C. P.; Steinke, Dirk; Braasch, Ingo; Hofmann, Hans A.; Meyer, Axel; Hofmann, Hans A.The cichlid fishes in general, and the exceptionally diverse East African haplochromine cichlids in particular, are famous examples of adaptive radiation and explosive speciation. Here we report the collection and annotation of more than 12,000 expressed sequence tags (ESTs) generated from three different cDNA libraries obtained from the East African haplochromine cichlid species Astatotilapia burtoni and Metriaclima zebra. Results: We first annotated more than 12,000 newly generated cichlid ESTs using the Gene Ontology classification system. For evolutionary analyses, we combined these ESTs with all available sequence data for haplochromine cichlids, which resulted in a total of more than 45,000 ESTs. The ESTs represent a broad range of molecular functions and biological processes. We compared the haplochromine ESTs to sequence data from those available for other fish model systems such as pufferfish (Takifugu rubripes and Tetraodon nigroviridis), trout, and zebrafish. We characterized genes that show a faster or slower rate of base substitutions in haplochromine cichlids compared to other fish species, as this is indicative of a relaxed or reinforced selection regime. Four of these genes showed the signature of positive selection as revealed by calculating K(a)/K(s) ratios. Conclusion: About 22% of the surveyed ESTs were found to have cichlid specific rate differences suggesting that these genes might play a role in lineage specific characteristics of cichlids. We also conclude that the four genes with a K(a)/K(s) ratio greater than one appear as good candidate genes for further work on the genetic basis of evolutionary success of haplochromine cichlid fishes.Item Functional Assessment of Human 21st Chromosome Orthologs in Caenorhabditis elegans(2020-05) Smith, Sofia; Pierce, JonathanDown syndrome (DS) is a neurodevelopmental disorder caused by having an extra copy of the 21st chromosome. Every person with DS exhibits muscle weakness and ID, though the precise genotype-phenotype is not fully understood. Little is known about the individual genes that make up the human 21st chromosome. In attempting to fill this gap, I have worked with the laboratory of Dr. Jon Pierce to systematically characterize the genes of the 21st chromosome for a potential role in the nervous system or muscle function. To this end, the Pierce lab uses the nematode Caenorhabditis elegans to study orthologs, or equivalent genes, from the human 21st chromosome. The general approach is to identify genes conserved between human and C. elegans and conduct broad, unbiased screens to identify potentially important genes. C. elegans can be a useful model for taking this approach to DS, as it has been used to discover the function of hundreds of genes in the nervous system and muscle in humans and shares orthologs with many of the protein-coding genes on our 21st chromosome. We first conducted a loss-of-function screen, taking the C. elegans genes and systematically knocking them down to observe phenotypic defects. The C. elegans loss-of-function mutants underwent a series of behavioral and pharmacological assays to evaluate phenotypic defects. The loss-of-function screen resulted in the identification of 10 genes thought to be critical for synaptic or motor function. Several of these genes were not previously identified for a contribution to DS. We have since begun a gain-of-function screen using similar behavioral tests to empirically determine which genes are problematic when overexpressed. Preliminary results implicate a few genes in disrupting neuron-to-muscle circuitry. I have also verified transcriptional overexpression in mutants relative to control strains. I aim to uncover the roles of the individual genes involved in DS-associated phenotypes. Establishing which genes contribute to DS could clarify the mechanism for the neuromuscular symptoms associated with DS. Doing so can provide a foundation for other DS researchers and inform efforts toward a more precise mechanism of action. The hope is that these genes might later serve as therapeutic targets for alleviating neuromuscular symptoms in people with DS.Item Social Odors Conveying Dominance and Reproductive information Induce Rapid Physiological and Neuromolecular Changes in a Cichlid Fish(2015-02) Simoes, Jose M.; Barata, Eduardo N.; Harris, Rayna M.; O'Connell, Lauren A.; Hofmann, Hans A.; Oliveira, Rui F.; Harris, Rayna M.; O'Connell, Lauren A.; Hofmann, Hans A.Social plasticity is a pervasive feature of animal behavior. Animals adjust the expression of their social behavior to the daily changes in social life and to transitions between life-history stages, and this ability has an impact in their Darwinian fitness. This behavioral plasticity may be achieved either by rewiring or by biochemically switching nodes of the neural network underlying social behavior in response to perceived social information. Independent of the proximate mechanisms, at the neuromolecular level social plasticity relies on the regulation of gene expression, such that different neurogenomic states emerge in response to different social stimuli and the switches between states are orchestrated by signaling pathways that interface the social environment and the genotype. Here, we test this hypothesis by characterizing the changes in the brain profile of gene expression in response to social odors in the Mozambique Tilapia, Oreochromis mossambicus. This species has a rich repertoire of social behaviors during which both visual and chemical information are conveyed to conspecifics. Specifically, dominant males increase their urination frequency during agonist encounters and during courtship to convey chemical information reflecting their dominance status. Results: We recorded electro-olfactograms to test the extent to which the olfactory epithelium can discriminate between olfactory information from dominant and subordinate males as well as from pre- and post-spawning females. We then performed a genome-scale gene expression analysis of the olfactory bulb and the olfactory cortex homolog in order to identify the neuromolecular systems involved in processing these social stimuli. Conclusions: Our results show that different olfactory stimuli from conspecifics' have a major impact in the brain transcriptome, with different chemical social cues eliciting specific patterns of gene expression in the brain. These results confirm the role of rapid changes in gene expression in the brain as a genomic mechanism underlying behavioral plasticity and reinforce the idea of an extensive transcriptional plasticity of cichlid genomes, especially in response to rapid changes in their social environment.