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M.L. Cancela et al.
7.4 Genomic Approaches in Growth and Nutrition
7.4.1 Introduction
One of the main objectives of fish aquaculture is to produce fish with an optimal
growth rate. In the wild, the overall fitness of fish populations, and particularly their
reproductive fitness, depends on the ability of fish to achieve a certain growth rate.
From a physiological point of view, fish growth is a complex process that depends on
other mutually interdependent physiological processes, such as development, nutrition and metabolism. Fish growth is commonly viewed as an increase in fish length
and, in particular, of its muscle mass in parallel to the bone structure and organs.
Skeletal muscle is the most important tissue for growth since it may represent more
than 50% of the body mass of the fish and is the tissue destined for human consumption. Most fish species have the ability to grow continuously throughout their
lifetime (Mommsen 2001). Growth is dependent on the production and development
of muscle fibers and on their metabolic capacity, which in turn depends on food
intake as well as on the supply, transport and utilization of nutrients. Therefore,
tissues directly involved in nutrition, such as the intestine, liver and adipose tissue, play an essential role in skeletal muscle growth. The liver, due to its capacity
to store carbohydrates as glycogen and to use them, to produce glucose by gluconeogenesis and to synthesize and store lipids, is possibly the most important organ
contributing to skeletal muscle metabolism. Since growth is a physiological process with multiple tissue contributions, a global and multidisciplinary approach is
required in order to have a complete view of all the factors contributing to muscle
growth. At the present time, this integrative physiological approach (i.e. Systems
Biology) can be used to integrate all the information obtained from the application
of transcriptomic, proteomic and metabolomic tools and reconstruct the pathways
and functional networks that govern the process of muscle growth.
7.4.2 Transcriptomic Changes in Skeletal Muscle Related
to Muscle Growth
Over the last few years, a growing tendency to use high-throughput technologies to
study muscle growth in fish has been observed. There are already a few transcriptomic studies related to muscle growth and most of them are restricted to salmonid
species. The first approach to study the transcriptome of the growing fish muscle consisted in the analysis of gene expression in transgenic salmon for growth
hormone (GH). Overexpression of GH in white skeletal muscle caused muscle
hyperplasia accompanied by increased expression of genes involved in transcription,
muscle fiber formation and muscle structure, as assessed by substractive hybridization (Hill et al. 2000). A more recent study revealed that transgenic salmon for
GH have a higher number and higher proliferation rates of muscle stem cells that
can be directly stimulated by GH in vitro; both processes are linked to changes
M.L. Cancela et al.
7.4 Genomic Approaches in Growth and Nutrition
7.4.1 Introduction
One of the main objectives of fish aquaculture is to produce fish with an optimal
growth rate. In the wild, the overall fitness of fish populations, and particularly their
reproductive fitness, depends on the ability of fish to achieve a certain growth rate.
From a physiological point of view, fish growth is a complex process that depends on
other mutually interdependent physiological processes, such as development, nutrition and metabolism. Fish growth is commonly viewed as an increase in fish length
and, in particular, of its muscle mass in parallel to the bone structure and organs.
Skeletal muscle is the most important tissue for growth since it may represent more
than 50% of the body mass of the fish and is the tissue destined for human consumption. Most fish species have the ability to grow continuously throughout their
lifetime (Mommsen 2001). Growth is dependent on the production and development
of muscle fibers and on their metabolic capacity, which in turn depends on food
intake as well as on the supply, transport and utilization of nutrients. Therefore,
tissues directly involved in nutrition, such as the intestine, liver and adipose tissue, play an essential role in skeletal muscle growth. The liver, due to its capacity
to store carbohydrates as glycogen and to use them, to produce glucose by gluconeogenesis and to synthesize and store lipids, is possibly the most important organ
contributing to skeletal muscle metabolism. Since growth is a physiological process with multiple tissue contributions, a global and multidisciplinary approach is
required in order to have a complete view of all the factors contributing to muscle
growth. At the present time, this integrative physiological approach (i.e. Systems
Biology) can be used to integrate all the information obtained from the application
of transcriptomic, proteomic and metabolomic tools and reconstruct the pathways
and functional networks that govern the process of muscle growth.
7.4.2 Transcriptomic Changes in Skeletal Muscle Related
to Muscle Growth
Over the last few years, a growing tendency to use high-throughput technologies to
study muscle growth in fish has been observed. There are already a few transcriptomic studies related to muscle growth and most of them are restricted to salmonid
species. The first approach to study the transcriptome of the growing fish muscle consisted in the analysis of gene expression in transgenic salmon for growth
hormone (GH). Overexpression of GH in white skeletal muscle caused muscle
hyperplasia accompanied by increased expression of genes involved in transcription,
muscle fiber formation and muscle structure, as assessed by substractive hybridization (Hill et al. 2000). A more recent study revealed that transgenic salmon for
GH have a higher number and higher proliferation rates of muscle stem cells that
can be directly stimulated by GH in vitro; both processes are linked to changes