Muscle fiber differentiation in fish embryos as shown by in situ hybridization of a large repertoire of muscle-specific transcripts.
Journal - Developmental dynamics : an official publication of the American Association of Anatomists (United States )
Skeletal muscles are composed of different fiber types, largely defined by differential expression of protein isoforms involved in myofibrillogenesis or metabolism. To learn more about the gene activations that underlie the differentiation and the diversification of embryonic fish myotomal fibers, we investigated the developmental expression of 25 muscle genes in trout embryos by in situ hybridization of muscle-specific transcripts. The earliest event of muscle differentiation, at approximately the 25-somite stage, was the expression of a variety of muscle-specific genes, including slow-twitch and fast-twitch muscle isoforms. The activation of these muscle genes started in the deep somitic domain, where the slow muscle precursors (the adaxial cells) were initially located, and progressively spread laterally throughout the width of the myotome. This mediolateral progression of gene expression was coordinated with the lateral migration of slow adaxial cells, which specifically expressed the slow myosin light chain 1 and the SLIM1/FHL1 genes. Subsequently, the fast and slow skeletal muscle isoforms precociously expressed in the course of the mediolateral wave of muscle gene activation became down-regulated in the superficial slow fibers and the deep fast fibers, respectively. Finally, several muscle-specific genes, including troponins, a slow myosin-binding protein C, tropomodulins, and parvalbumin started their transcription only in late embryos. Taken together, these findings show in fish embryos that a common myogenic program is triggered in a mediolateral progression in all muscle cells. The acquisition of the slow phenotype involves the additional activation of several slow-specific genes in migrating adaxial muscle cells. These events are followed by sequential gene activations and repressions in fast and slow muscle cells.Copyright 2005 Wiley-Liss, Inc
|ISSN : ||1058-8388|
|Mesh Heading : ||Animals Cell Differentiation DNA, Complementary Down-Regulation Embryo, Nonmammalian Gene Expression Regulation, Developmental In Situ Hybridization Muscle Development Muscle Fibers, Skeletal Myosin Light Chains Oncorhynchus mykiss Organ Specificity Transcription, Genetic Transcriptional Activation Tropomyosin Troponin C genetics genetics metabolism genetics genetics genetics genetics genetics|
|Mesh Heading Relevant : ||genetics embryology genetics cytology metabolism embryology genetics|
Effect of refeeding on IGFI, IGFII, IGF receptors, FGF2, FGF6, and myostatin mRNA expression in rainbow trout myotomal muscle.
Journal - General and comparative endocrinology (United States )
Fish endure long periods of fasting and demonstrate an extensive capacity for rapid and complete recovery after refeeding. The underlying mechanisms through which nutrient intake activates an increase in somatic growth and especially in muscle growth is poorly understood. In this study we examined the expression profile of major muscle growth regulators in trout white muscle 4, 12, and 34 days after refeeding, using real-time quantitative RT-PCR. Mean insulin-like growth factor I (IGFI) mRNA level in muscle increased dramatically 8- and 15-fold, 4 and 12 days, respectively, after refeeding compared to fasted trout. This declined thereafter. Conversely, only a weak but gradual increase in mean insulin-like growth factor II (IGFII) mRNA level was observed during refeeding. Inversely to IGFI, mean IGF receptor Ia (IGFRIa) mRNA level declined after ingestion of food. In contrast, IGF receptor Ib (IGFRIb) mRNA level was not affected by refeeding. Mean fibroblast growth factor 2 (FGF2) mRNA level increased by 2.5-fold both 4 and 12 days after refeeding, whereas fibroblast growth factor 6 (FGF6) and myostatin mRNA levels were unchanged. Subsequent to IGFI and FGF2 gene activation, an increase in myogenin mRNA accumulation was observed at 12 days post-refeeding suggesting that an active differentiation of myogenic cells succeeds their proliferation. In conclusion, among the potential growth factors we examined in this study, IGFI and FGF2 were identified as candidate genes whose expression may contribute to muscle compensatory growth induced by refeeding.
|ISSN : ||0016-6480|
|Mesh Heading : ||Animals Eating Fasting Fibroblast Growth Factor 2 Fibroblast Growth Factors Insulin-Like Growth Factor I Insulin-Like Growth Factor II Muscle, Skeletal Myogenin Oncorhynchus mykiss Proto-Oncogene Proteins RNA, Messenger Reverse Transcriptase Polymerase Chain Reaction Somatomedins physiology biosynthesis biosynthesis biosynthesis cytology growth & development biosynthesis biosynthesis isolation & purification|
|Mesh Heading Relevant : ||physiology biosynthesis metabolism metabolism biosynthesis biosynthesis|