In vivo analysis using variants of zebrafish BMPR-IA: range of action and involvement of BMP in ectoderm patterning.
It has been an intriguing problem whether the polypeptide growth factors belonging to the transforming growth factor-beta (TGF-beta) superfamily function as direct and long-range signaling molecules in pattern formation of the early embryo. In this study, we examined the mechanism of signal propagation of bone morphogenetic protein (BMP) in the ectodermal patterning of zebrafish embryos, in which BMP functions as an epidermal inducer and a neural inhibitor. To estimate the effective range of zbmp-2, we first performed whole-mount in situ hybridization analysis. The zbmp-2-expressing domain and the neuroectoderm, marked by otx-2 expression, were complementary, suggesting that BMP has a short-range effect in vivo. Moreover, mosaic experiments using a constitutively active form of a zebrafish BMP type I receptor (CA-BRIA) demonstrated that the cell-fate conversion, revealed by ectopic expression of gata-3 and repression of otx-2, occurred in a cell-autonomous manner, denying the involvement of the relay mechanism. We also found that zbmp-2 was induced cell autonomously within the transplanted cells in the host ectoderm, suggesting that BMP cannot influence even the neighboring cells. This result is consistent with the observation that there is no gap between the expression domains of zbmp-2 and otx-2. Taken together, we propose that, in ectodermal patterning, BMP exerts a direct and cell-autonomous effect to fate uncommitted ectodermal cells to become epidermis.
Nikaido
M
M
Department of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
Tada
M
M
Takeda
H
H
Kuroiwa
A
A
Ueno
N
N
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019521:Body Patterning / Q000502:physiology*; D055396:Bone Morphogenetic Protein 2; D052005:Bone Morphogenetic Protein Receptors, Type I; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D004475:Ectoderm / Q000502:physiology*; D004625:Embryo, Nonmammalian; D004627:Embryonic Induction / Q000502:physiology; D018398:Homeodomain Proteins; D008648:Mesoderm; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009474:Neurons; D051857:Otx Transcription Factors; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017978:Receptors, Growth Factor / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta; D014982:Xenopus laevis / Q000235:genetics; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics; D029961:Zebrafish Proteins
D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D051857:Otx Transcription Factors; D017978:Receptors, Growth Factor; D011994:Recombinant Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D029961:Zebrafish Proteins; C497662:otx2b protein, zebrafish; D017346:Protein Serine-Threonine Kinases; D052005:Bone Morphogenetic Protein Receptors, Type I