Asymmetric p38 activation in zebrafish: its possible role in symmetric and synchronous cleavage.
Cleavage is one of the initial steps of embryogenesis, and is characterized by a series of symmetric and synchronous cell divisions. We showed that p38 MAP kinase (p38) is asymmetrically activated on one side of the blastodisc during the early cleavage period in zebrafish (Danio rerio) embryos. When a dominant negative (DN) form of p38 was uniformly expressed, blastomere cleavage was impaired on one side of the blastodisc, resulting in the formation of blastomeres with a large mass of cytoplasm and an enlarged nucleus on the affected side. The area affected by the DN-p38 expression did not correlate with the initial cleavage plane, but coincided with the side where dharma/bozozok, a dorsal-specific zygotic gene, was expressed (Yamanaka et al. 1998). Furthermore, UV irradiation and removal of the vegetal yolk mass before the first cleavage, both of which inhibit the initiation of the dorsalizing signals, abolished the asymmetric p38 activation. Our findings suggest that asymmetric p38 activation is required for symmetric and synchronous cleavage, and may be regulated by the same machinery that controls the initiation of dorsalizing signals.
Fujii
R
R
Division of Molecular Oncology, Biomedical Research Center (C-7), Osaka University Graduate School of Medicine, Suita, Osaka 565-0871 Japan.
Yamashita
S
S
Hibi
M
M
Hirano
T
T
D000818:Animals; D001757:Blastomeres / Q000166:cytology / Q000201:enzymology; D001973:Bromodeoxyuridine / Q000032:analysis; D002455:Cell Division / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology; D003001:Cloning, Molecular; D004530:Egg Yolk / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000201:enzymology; D004789:Enzyme Activation / Q000502:physiology / Q000528:radiation effects; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D017403:In Situ Hybridization; D008156:Luciferases / Q000235:genetics; D008870:Microtubules / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D014466:Ultraviolet Rays; D015027:Zebrafish; D048051:p38 Mitogen-Activated Protein Kinases
D012333:RNA, Messenger; D008156:Luciferases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D001973:Bromodeoxyuridine