Cyclin D and cdk4 are required for normal development beyond the blastula stage in sea urchin embryos.
cdk4 mRNA and protein are constitutively expressed in sea urchin eggs and throughout embryonic development. In contrast, cyclin D mRNA is barely detectable in eggs and early embryos, when the cell cycles consist of alternating S and M phases. Cyclin D mRNA increases dramatically in embryos at the early blastula stage and remains at a constant level throughout embryogenesis. An increase in cdk4 kinase activity occurs concomitantly with the increase in cyclin D mRNA. Ectopic expression of cyclin D mRNA in eggs arrests development before the 16-cell stage and causes eventual embryonic death, suggesting that activation of cyclin D/cdk4 in cleavage cell cycles is lethal to the embryo. In contrast, blocking cyclin D or cdk4 expression with morpholino antisense oligonucleotides results in normal development of early gastrula-stage embryos but abnormal, asymmetric larvae. These results suggest that in sea urchins, cyclin D and cdk4 are required for normal development and perhaps the patterning of the developing embryo, but may not be directly involved in regulating entry into the cell cycle.
Moore
Jennifer C
JC
Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Sumerel
Jan L
JL
Schnackenberg
Bradley J
BJ
Nichols
Jason A
JA
Wikramanayake
Athula
A
Wessel
Gary M
GM
Marzluff
William F
WF
D000595:Amino Acid Sequence; D000818:Animals; D001755:Blastocyst; D003001:Cloning, Molecular; D056741:Cyclin D; D051358:Cyclin-Dependent Kinase 4; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D016213:Cyclins / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger / Q000378:metabolism; D012617:Sea Urchins / Q000196:embryology* / Q000235:genetics
D056741:Cyclin D; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016213:Cyclins; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases