228
M.L. Cancela et al.
of genes involved in mitochondrial metabolism, oxidative stress, as well as heat
shock proteins 70 and 90. However, these changes in gene expression have not
been related with changes in muscular growth by hypertrophy. A very interesting
study on the effects of temperature acclimatation was performed in carp (Cyprinus
carpio) using a custom cDNA array containing 13,349 sequences (Gracey et al.
2004). The authors studied 7 tissues and reported that a decrease in temperature
elicits a common basic response in all tissues related to metabolism and an additional, more specific, response related to the function of each tissue. In particular,
skeletal muscle undergoes a down-regulation of genes involved in remodeling of the
contractile system and an up-regulation of genes involved in protein degradation.
Reviews on this topic have been written by Gracey and co-workers (Cossins et al.
2006, Gracey 2007), but the accepted hypothesis about the transcriptional effects
of temperature acclimatation is that the muscle suffers a reduction in activity coupled with protein degradation that leads to atrophy. Using a physiological model
of muscle atrophy in rainbow trout and assessing changes in gene expression with
the GRASP 16 K microarray platform, Salem et al. have identified differentially
expressed genes, representing 1% of the total of the genes present in the microarray
(Salem et al. 2006). During vitellogenesis, trout skeletal muscle suffers a marked
atrophy that is reflected by transcriptional changes that affect different cellular processes, protein degradation being one of the most relevant. This model could be
useful for the identification of genes or gene patterns important for evaluating the
function of skeletal muscle.
The skeletal muscle is the preferred tissue for DNA vaccine administration due to
its easy access and to its high production of expressed antigens. Concerning growth,
expression of elevated amounts of antigens in muscle could cause an activation of
the immune system that could lead to growth defects. Purcell et al. have evaluated
changes in gene expression after DNA vaccination against infectious hematopoietic
necrosis virus (IHNV) using the GRASP 16 K microarray (Purcell et al. 2006).
Vaccination caused a strong immune response as evidenced by the increase in the
expression of genes involved in antigen presentation and viral response in skeletal
muscle. In addition, an increase in the expression of marker genes for leukocytes
was observed sugesting an infiltration of leukocytes in the muscle tissue. Therefore,
microarray analysis of vaccinated skeletal muscle indicates that the activation of
a transcriptional response in this tissue could alter its metabolic and/or functional
status.
7.4.4 Genomic Approaches to the Study of Hepatic Function
In teleost fish, the liver plays a key role in nutrition and metabolism as an important site for the synthesis of energy reserves in the form of lipids, carbohydrates
and proteins. In addition, the liver is essential for the response to fasting by mobilizing energy reserves into the bloodstream and providing nutrients to the tissues
and, therefore, is important for the maintenance of homeostasis. In relation to its
key role in homeostasis, the liver is one of the main targets for metabolic hormones
M.L. Cancela et al.
of genes involved in mitochondrial metabolism, oxidative stress, as well as heat
shock proteins 70 and 90. However, these changes in gene expression have not
been related with changes in muscular growth by hypertrophy. A very interesting
study on the effects of temperature acclimatation was performed in carp (Cyprinus
carpio) using a custom cDNA array containing 13,349 sequences (Gracey et al.
2004). The authors studied 7 tissues and reported that a decrease in temperature
elicits a common basic response in all tissues related to metabolism and an additional, more specific, response related to the function of each tissue. In particular,
skeletal muscle undergoes a down-regulation of genes involved in remodeling of the
contractile system and an up-regulation of genes involved in protein degradation.
Reviews on this topic have been written by Gracey and co-workers (Cossins et al.
2006, Gracey 2007), but the accepted hypothesis about the transcriptional effects
of temperature acclimatation is that the muscle suffers a reduction in activity coupled with protein degradation that leads to atrophy. Using a physiological model
of muscle atrophy in rainbow trout and assessing changes in gene expression with
the GRASP 16 K microarray platform, Salem et al. have identified differentially
expressed genes, representing 1% of the total of the genes present in the microarray
(Salem et al. 2006). During vitellogenesis, trout skeletal muscle suffers a marked
atrophy that is reflected by transcriptional changes that affect different cellular processes, protein degradation being one of the most relevant. This model could be
useful for the identification of genes or gene patterns important for evaluating the
function of skeletal muscle.
The skeletal muscle is the preferred tissue for DNA vaccine administration due to
its easy access and to its high production of expressed antigens. Concerning growth,
expression of elevated amounts of antigens in muscle could cause an activation of
the immune system that could lead to growth defects. Purcell et al. have evaluated
changes in gene expression after DNA vaccination against infectious hematopoietic
necrosis virus (IHNV) using the GRASP 16 K microarray (Purcell et al. 2006).
Vaccination caused a strong immune response as evidenced by the increase in the
expression of genes involved in antigen presentation and viral response in skeletal
muscle. In addition, an increase in the expression of marker genes for leukocytes
was observed sugesting an infiltration of leukocytes in the muscle tissue. Therefore,
microarray analysis of vaccinated skeletal muscle indicates that the activation of
a transcriptional response in this tissue could alter its metabolic and/or functional
status.
7.4.4 Genomic Approaches to the Study of Hepatic Function
In teleost fish, the liver plays a key role in nutrition and metabolism as an important site for the synthesis of energy reserves in the form of lipids, carbohydrates
and proteins. In addition, the liver is essential for the response to fasting by mobilizing energy reserves into the bloodstream and providing nutrients to the tissues
and, therefore, is important for the maintenance of homeostasis. In relation to its
key role in homeostasis, the liver is one of the main targets for metabolic hormones