Int. J. Dev. Biol. 48: 327 - 332 (2004)
doi: 10.1387/ijdb.041838ta
© UPV/EHU Press

Activin-like signaling activates Notch signaling during mesodermal induction

Takanori Abe1, Miho Furue2, Yasufumi Myoishi3, Tetsuji Okamoto3, Akiko Kondow4 and Makoto Asashima*,1, 4, 5

1Department of Biological Science, Graduate School of Science, The University of Tokyo, Japan 2Department of Biochemistry and Molecular Biology, Kanagawa Dental College, Yokosuka, Japan

ABSTRACT Both activin-like signaling and Notch signaling play fundamental roles during early development. Activin-like signaling is involved in mesodermal induction and can induce a broad range of mesodermal genes and tissues from prospective ectodermal cells (animal caps). On the other hand, Notch signaling plays important roles when multipotent precursor cells achieve a specific cell fate. However, the relationship between these two signal pathways is not well understood. Here, we show that activin A induces Delta-1, Delta-2 and Notch expression and then activates Notch signaling in animal caps. Also, in vivo, ectopic activin-like signaling induced the ectopic expression of Delta-1 and Delta-2, whereas inhibition of activin-like signaling abolished the expression of Delta-1 and Delta-2. Furthermore, we show that MyoD, which is myogenic gene induced by activin A, can induce Delta-1 expression. However, MyoD had no effect on Notch expression, and inhibited Delta-2 expression. These results indicated that activin A induces Delta-1, Delta-2 and Notch by different cascades. We conclude that Notch signaling is activated when activin-like signaling induces various tissues from homogenous undifferentiated cells.

Keywords:

Xenopus laevis, activin, Notch signaling, MyoD, mesoderm induction

*Corresponding author e-mail: asashi@bio.c.u-tokyo.ac.jp