Cells differentiating into neuroectoderm undergo apoptosis in the absence of functional retinoblastoma family proteins.
The retinoblastoma (RB) protein is present at low levels in early mouse embryos and in pluripotent P19 embryonal carcinoma cells; however, the levels of RB rise dramatically in neuroectoderm formed both in embryos and in differentiating cultures of P19 cells. To investigate the effect of inactivating RB and related proteins p107 and p130, we transfected P19 cells with genes encoding mutated versions of the adenovirus E1A protein that bind RB and related proteins. When these E1A-expressing P19 cells were induced to differentiate into neuroectoderm, there was a striking rise in the expression of c-fos and extensive cell death. The ultrastructural and biochemical characteristics of the dying cells were indicative of apoptosis. The dying cells were those committed to the neural lineages because neurons and astrocytes were lost from differentiating cultures. Cell death was dependent on the ability of the E1A protein to bind RB and related proteins. Our results suggest that proteins of the RB family are essential for the development of the neural lineages and that the absence of functional RB activity triggers apoptosis of differentiating neuroectodermal cells.
Slack
R S
RS
Department of Medicine, University of Ottawa, Ontario, Canada.
Skerjanc
I S
IS
Lach
B
B
Craig
J
J
Jardine
K
K
McBurney
M W
MW
D017500:Adenovirus E1A Proteins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D001253:Astrocytes / Q000473:pathology; D018236:Carcinoma, Embryonal; D002454:Cell Differentiation; D004249:DNA Damage; D004475:Ectoderm; D005786:Gene Expression Regulation / Q000187:drug effects; D005814:Genes, Viral / Q000235:genetics; D051379:Mice; D009132:Muscles / Q000196:embryology; D009420:Nervous System / Q000187:drug effects / Q000196:embryology* / Q000473:pathology / Q000648:ultrastructure; D009474:Neurons / Q000473:pathology; D009687:Nuclear Proteins / Q000378:metabolism; D010750:Phosphoproteins; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D016160:Retinoblastoma Protein / Q000378:metabolism*; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D017384:Sequence Deletion; D013234:Stem Cells / Q000502:physiology; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D017500:Adenovirus E1A Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011506:Proteins; D016760:Proto-Oncogene Proteins c-fos; C489485:Rbl1 protein, mouse; C493838:Rbl2 protein, mouse; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D014212:Tretinoin