Mesoderm induction in Xenopus laevis distinguishes between the various TGF-beta isoforms.
Induction of mesoderm in ectodermal explants of Xenopus laevis blastula embryos had previously been shown to respond selectively to TGF-beta 2, with TGF-beta s 1 and 5 having no activity in this assay. As TGF-beta s 1, 2, and 3 are frequently coexpressed in tissues, we wished to examine the activity of TGF-beta 3 relative to that of TGF-beta s 1 and 2 in this assay as well as in other in vitro assays. We report here that when the activity of recombinant TGF-beta 3 is normalized to that of TGF-beta 1 in the assay for growth inhibition in CCL-64 cells, it is also equal to that of TGF-beta 1 in assays for stimulation of both anchorage-independent growth of rat NRK cells and chemotaxis of human monocytes. In contrast, in the assay for mesoderm induction, recombinant TGF-beta 3 is 10-fold more active than TGF-beta 2, inducing expression of muscle specific alpha-actin at concentrations as low as 1 ng/ml. These results suggest that more complex systems, in contrast to individual cell types, may respond selectively to the various TGF-beta isoforms and that there might be biological consequences of TGF-beta isoform switching in vivo.
Roberts
A B
AB
Laboratory of Chemoprevention, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
Kondaiah
P
P
Rosa
F
F
Watanabe
S
S
Good
P
P
Danielpour
D
D
Roche
N S
NS
Rebbert
M L
ML
Dawid
I B
IB
Sporn
M B
MB
D000818:Animals; D001483:Base Sequence; D001755:Blastocyst / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D004625:Embryo, Nonmammalian / Q000502:physiology; D006133:Growth Substances / Q000494:pharmacology; D008648:Mesoderm / Q000187:drug effects / Q000502:physiology*; D008969:Molecular Sequence Data; D010957:Plasmids; D015183:Restriction Mapping; D013329:Structure-Activity Relationship; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000494:pharmacology*; D014982:Xenopus laevis
D006133:Growth Substances; D016212:Transforming Growth Factor beta