... Myogenesis Myogenic regulatory factor Myogenin Muscle hyperplasia Transgenesis Skeletal muscle formation involves the determination of mesodermal cells into myoblasts and the differentiation of myoblasts into myofibres. These steps depend on the activity of transcription factors in the basic...

... family of myogenic regulatory factors (MRFs) in the transcriptional activation of the muscle program in vertebrates, we examined their expression in the electrocytes of the gymnotiform Sternopygus macrurus . We estimated the number of MRF genes in the S. macrurus genome and our Southern blot analyses...

.... * Author for correspondence (e-mail: iaj@st-andrews.ac.uk ) 17 9 2004 © The Company of Biologists Limited 2004 2004 muscle fibres myogenesis growth myogenic progenitor cell resource polymorphism developmental plasticity fish Arctic charr myogenic regulatory factor Paired box...

... and 25°C. cRNA probes were used to detect transcripts of the myogenic regulatory factors MyoD, Myf-5 and myogenin, and five myosin heavy chain (MyHC) isoforms during development. The genes encoding Myf-5 and MyoD were switched on first in the unsegmented mesoderm, followed by myogenin as the somites...