Abstract

A recent publication1 describes a novel mechanism by which a morphogen gradient might be established. These results concern a gradient of FGF8 expression along the longitudinal axis of the chick embryo with a high level of transcripts at the tail, fading off in an anterior direction. Assaying for intron transcripts, it is shown that fgf8 is transcribed only in the tail cells and that the gradient of fgf8 transcripts is produced by growth and mRNA degradation. This possible mechanism of gradient formation can operate only when growth is involved, as is the case in many examples including the longitudinal axis formation of vertebrates, but is not in some other systems. BioEssays 26:705–706, 2004. © 2004 Wiley Periodicals, Inc.