Runx-dependent expression of PKC is critical for cell survival in the sea urchin embryo.
BACKGROUND
Runx transcription factors play critical roles in the developmental control of cell fate and contribute variously as oncoproteins and tumor suppressors to leukemia and other cancers. To discover fundamental Runx functions in the cell biology of animal development, we have employed morpholino antisense-mediated knockdown of the sea urchin Runx protein SpRunt-1. Previously we showed that embryos depleted of SpRunt-1 arrest development at early gastrula stage and underexpress the conventional protein kinase C SpPKC1.


RESULTS
We report here that SpRunt-1 deficiency leads to ectopic cell proliferation and extensive apoptosis. Suppression of the apoptosis by pharmacological inhibition of caspase-3 prevents the ectopic proliferation and rescues gastrulation, indicating that many of the overt defects obtained by knockdown of SpRunt-1 are secondary to the apoptosis. Inhibition or knockdown of SpPKC1 also causes apoptosis, while cell survival is rescued in SpRunt-1 morphant embryos coinjected with SpPKC1 mRNA, suggesting that the apoptosis associated with SpRunt-1 deficiency is caused by the deficit in SpPKC1 expression. Chromatin immunoprecipitation indicates that SpRunt-1 interacts physically with SpPKC1 in vivo, and cis-regulatory analysis shows that this interaction activates SpPKC1 transcription.


CONCLUSIONS
Our results show that Runx-dependent activation of SpPKC1 is essential for maintaining protein kinase C activity at levels conducive to cell survival during embryogenesis.
Dickey-Sims
Carrie
C
Stowers Institute for Medical Research, 1000 E, 50th Street, Kansas City, Missouri 64110, USA. ced@stowers-institute.org
Robertson
Anthony J
AJ
Rupp
Dawn E
DE
McCarthy
John J
JJ
Coffman
James A
JA
D000818:Animals; D001483:Base Sequence; D002470:Cell Survival / Q000502:physiology*; D050657:Core Binding Factor alpha Subunits / Q000172:deficiency* / Q000235:genetics / Q000502:physiology*; D004625:Embryo, Nonmammalian / Q000166:cytology*; D005775:Gastrula / Q000166:cytology / Q000502:physiology; D017353:Gene Deletion; D016376:Oligonucleotides, Antisense; D011493:Protein Kinase C / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D012617:Sea Urchins / Q000196:embryology* / Q000235:genetics
D050657:Core Binding Factor alpha Subunits; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D011493:Protein Kinase C