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When being obese is healthy: molecular evolution of genes related to metabolism in cetaceans
Energetic homeostasis is the process responsible for balancing the energy rates ingested and expelled from our organism. In most mammals, there is a strict control of the homeostasis and satiety regulation, through anorexigenic and orexigenic peptides. However, some lineages of mammals have different regulation, being able to not feed during months and also going through periods of intense feeding, apparently without getting satisfaction. Notorious examples of this behavior are migrating whales that perform long migrations. This project aims to investigate the genetic basis of this distinct feeding behavior, that evolved independently in some lineages. Accordingly, we investigated the evolutionary rate in genes involved in the central control of the metabolism (POMC, MC4R, NPY) in mammals, focusing on cetacean lineage, to better understand their evolutionary histories. We performed DNA extraction, PCR and gene sequencing in tissue samples from humpback whale (Megaptera novaeangliae), blue whale (Balaenoptera musculus) and the common bottlenose dolphin (Tursiops truncatus). Also, we retrieved sequences from public databases, such a Ensembl and GeneBank, from a comprehensive set of tetrapod species, including representatives from as many mammalian orders as possible. After that, we performed selection analyses using different models implemented in PAML, and also used different algorithms in Datamonkey and Fitmodel. Positive or relaxing selection was not observed in NPY. For MC4R and POMC, omega value was significantly greater for the cetacean lineage compared to other lineages, indicating an acceleration on their evolutionary rate. Our preliminary results aid to draw a panorama on selection pressure on these genes along evolution and improve our understanding of molecular evolution of metabolic genes in mammalian history, suggesting that some of these genes underwent an accelerated evolution on specific lineages, such as on cetacean lineage.
Key-Words: Cetaceans; Migration; Evolution; Evolutionary Genomics; Bioinformatics.
Funding Agency: FAPESP.
Michelle C. R. Ribeiro, Érica M. S. Souza, Elisa K. S. Ramos, Mariana F. Nery