Myf-5 is transiently expressed in nonmuscle mesoderm and exhibits dynamic regional changes within the presegmented mesoderm and somites I-IV.
Myf-5 is one of four myogenic regulatory factors that play important roles in skeletal muscle development. This study provides detailed analysis of Myf-5 expression during early chick development using an in situ hybridization technique that has been optimized to detect low level Myf-5 transcripts. This facilitated detection of heretofore unrecognized dynamic changes in Myf-5 expression patterns. Myf-5 expression is first detected at stage 3 in the primitive streak and exhibits transient low-level expression in nonmyogenic mesoderm. Myf-5 is later expressed in the presegmented mesoderm (psm) in a reiterating pattern that is coordinated with somitogenesis and also colocalizes with the Notch ligand C-Delta-1. In somites (S) I-IV, Myf-5 expression exhibits dynamic regional changes, and in somites rostral to S IV, Myf-5 is expressed at higher levels in muscle precursors in the dorsomedial somite. Semiquantitative comparison of Myf-5 mRNA levels in the psm and in myotome-containing somites indicates about a 10-fold difference. The expression pattern of Myf-5 differs from that of MyoD, which we find is expressed only in the dorsomedial somite. These data reveal that Myf-5 is expressed at low levels several stages before muscle differentiation occurs and suggest that only a subset of cells that initially express Myf-5 will upregulate its expression and differentiate as muscle.
Department of Biochemistry, University of Washington, Seattle, Washington, 98195, USA.
J C
JC
Kiefer
S D
SD
Hauschka
D000818:Animals; D002642:Chick Embryo; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000235:genetics; D008648:Mesoderm / Q000378:metabolism*; D009124:Muscle Proteins / Q000235:genetics*; D017570:MyoD Protein / Q000235:genetics; D051787:Myogenic Regulatory Factor 5; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015534:Trans-Activators
D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009124:Muscle Proteins; D017570:MyoD Protein; D051787:Myogenic Regulatory Factor 5; D012333:RNA, Messenger; D015534:Trans-Activators; C064045:delta protein