The pacu (Piaractus mesopotamicus) myoblast cell culture as a model to understand muscle growth regulation in Ostariophysi superorder

Abstract

Whole genome duplication (WGD) events are considered a major feature of the evolution of eukaryotic genomes, providing raw materials in where natural selection can act to promote increasing complexity. Teleost fish have undergone a specific WGD (TSGD) in the base of the lineage, estimated at 450-320 million years ago. Around 15-21% of the TSGD-derived paralogues have been retained due to subfunctionalization and/or neofunctionalization processes. Recent studies have demonstrated differences in paralogues retention between the teleost superorders Ostariophysi and Acanthopterygii, many of them key components of the protein synthesis and myogenesis. However, despite the progresses done in the identification of these lineage-specific paralogues (LSPs), their physiological roles remain unknown in the majority of cases. The pacu (Piaractus mesopotamicus) and the Nile tilapia (Oreochromis niloticus) belong to superorders Ostariophysi and Acanthopterygii, respectively. Both species are economically relevant for the Brazilian aquaculture and, therefore, objects of an intense research to improve their production.Skeletal muscle is the most abundant tissue in teleost fish, representing up to 65% of the total body mass for some species. Fast muscle comprises the bulk of the fillet (up to 90% of the muscle mass) and corresponds to the commercial part of the fish. Muscle growth is strongly dependent of the balance between protein synthesis and degradation, processes regulated by intrinsic and extrinsic signals. Among them, growth factors (such as Igfs) and amino acids have demonstrated to play an essential role in protein synthesis and muscle growth regulation. The fast muscle myoblast culture is arising as a very useful in vitro tool to study the regulation of muscle growth. The cell culture recapitulates all the steps from myogenesis: myoblast commitment, proliferation, fusion and myotube formation. Cell cultures can be manipulated to generate experimental conditions that would allow us to study muscle regulation, growth and development at different levels and under a variety of circumstances. Similarly, cell culture media can be modified to evaluate the role of nutrients or growth factors in the regulation of myogenesis. The myoblast cell culture has been successfully developed in Acanthopterygii and Protacanthopterygii species, what turns many of the assumptions derived from those models very difficult to extrapolate to Ostariophysi species. Therefore, the pacu myoblast culture is an excellent model to understand the regulation of myogenesis and muscle growth in Ostariophysi superorder.During this PhD we intend to compare the expression of LSPs related to protein synthesis between Ostariophysi and Acanthopterygii during muscle development, through the establishment of myoblast cultures from pacu and Nile tilapia. We hypothesized that distinct mechanisms of subfunctionalization and/or neofunctionalization occurred between the teleost superorders Ostariophysi and Acanthopterygii, which promoted a differential retention of LSPs related to protein synthesis. This comparison will allow us to identify subfunctionalization and neofunctionalization events of the LSPs related to protein synthesis and to understand their roles during myogenesis and muscle growth in both lineages. To provide further insight, we will use myoblast cultures to evaluate the effects of Igfs and amino acids treatments in LSPs expression. Our work will contribute to better understand the evolutionary divergence of Ostariophysi and Acanthopterygii superorders and the regulation of myogenesis process in fish, allowing the development of a theoretic framework that may help to improve muscle growth. (AU)