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Nuclear receptors constitute a large family of transcription factors that are powerful regulators of animal tissue metabolism, homeostasis, tissue maintenance and development. They are particularly attractive for their ability to respond to the binding of hormones, metabolites, xenobiotics and artificially prepared molecules and transmit the interaction with these small lipophylic molecules to specific regulatory potential. In search for nuclear receptors that are likely to be critical for neural tissues in invertebrates and conserved during the evolution of animals, we have identified a close homologue of vertebrate TLX in a planarian Schmidtea mediterranea. Planaria represent very promising biological model systems for studies on tissue maintenance and regeneration. Planaria are able to resorb their tissues and use them as sources of energy during fasting and they re-build their bodies from neoblasts when food is plentiful. Our search in Schmidtea mediterranea's publicly accessible genome sequencing data indicated that planarian genome contains at least one gene with a high degree of similarity to vertebrate TLX. We cloned full length CDS (coding DNA sequence of cDNA) and characterized the gene functionally. This showed that the planarian and vertebrate NR2E1 are highly similar...

Nuclear receptors constitute a large family of transcription factors that are powerful regulators of animal tissue metabolism, homeostasis, tissue maintenance and development. They are particularly attractive for their ability to respond to the binding of hormones, metabolites, xenobiotics and artificially prepared molecules and transmit the interaction with these small lipophylic molecules to specific regulatory potential. In search for nuclear receptors that are likely to be critical for neural tissues in invertebrates and conserved during the evolution of animals, we have identified a close homologue of vertebrate TLX in a planarian Schmidtea mediterranea. Planaria represent very promising biological model systems for studies on tissue maintenance and regeneration. Planaria are able to resorb their tissues and use them as sources of energy during fasting and they re-build their bodies from neoblasts when food is plentiful. Our search in Schmidtea mediterranea's publicly accessible genome sequencing data indicated that planarian genome contains at least one gene with a high degree of similarity to vertebrate TLX. We cloned full length CDS (coding DNA sequence of cDNA) and characterized the gene functionally. This showed that the planarian and vertebrate NR2E1 are highly similar...

Using a high throughput closed respirometry method to measure oxygen consumption, I determined metabolic rates in asexual and sexual Schmidtea mediterranea and Girardia dorotocephala, as a function of temperature, taxon, stressors, reproductive mode, age, regeneration, and specific dynamic action. This study has shown that oxygen consumption can reliably be measured in planaria using optode closed respirometry, and also provided a reliable method for measuring wet mass in planaria, which has been a challenge to researchers in the past. This research revealed that oxygen consumption in S. mediterranea is 1.5-2.1X greater in the sexual strain over the asexual strain at 13-18°C. Within the sexual strain, oxygen consumption is 1.5 -2.2X greater in sexually mature adults over the sexually immature groups (hatchlings, juveniles, and regenerating sexuals). Furthermore, I was able to quantify differences in sexual morphology between these groups exhibiting significant differences in oxygen consumption. The results of this research supports a theory of higher metabolic costs with sexual maturity in S. mediterranea. Therefore, this study has established sexual and asexual S. mediterranea as simple, yet attractive models for investigating energetic costs between sexual and asexual phenotypes. This research also provided quantitative values for specific dynamic action in planaria, with a maximum increase in oxygen consumption of 160% induced by feeding, as well as metabolic relationships in planaria involving temperature, age, and regeneration. These values establish planaria as one of the simplest animal models in which common metabolic patterns, such as SDA and poikilothermic temperature sensitivity, have been demonstrated. Therefore, this research has contributed to the overall knowledge of the basic physiology in this animal, providing the framework for future metabolic studies in planaria involving environmental factors, reproduction, regeneration, development, and aging. Information from this study may supplement interpretation and understanding of modern cellular, molecular, and genomic studies in planaria.