Study of the gonocyte cell cycle in irradiated TP53 knockout mouse foetuses and newborns.
OBJECTIVE
To investigate the role of p53 in gonocyte cell-cycle arrest in rodents with or without radiation exposure.


METHODS
Pregnant p53 (+/-) mice, mated with p53 (-/-) males, were exposed to (137)Cs gamma-rays at day 18 postcoitum (p.c.) at doses ranging from 1.5 Gy to 3 Gy. The gonocyte cell cycle was studied in p53 (-/-) male foetuses and newborns after BrdU incorporation and DAPI staining, and compared with those of p53 wild-type animals.


RESULTS
The proliferation of gonocytes in wild-type mice is normally arrested between day 16 p.c. and birth, a period when p53 is strongly expressed in gonocytes; p53 high expression is prolonged in all gonocytes after 3 Gy irradiation. In p53 (-/-) mice, this period of gonocyte cell-cycle arrest is not modified, compared with wild-type mice. It is also prolonged after a 3 Gy exposure.


CONCLUSIONS
Two hypotheses are proposed. Either p53 is not involved in the control of gonocyte cell-cycle arrest in control and irradiated mice, or its role is redundant in this process.
Département de Radiobiologie et Radiopathologie, DSV/LRCG/CEA, BP 6, 92265 Fontenay-aux-Roses cedex, France.
S G
SG
Moreno
B
B
Dutrillaux
H
H
Coffigny
D000818:Animals; D000831:Animals, Newborn; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002453:Cell Cycle / Q000528:radiation effects*; D005333:Fetus / Q000528:radiation effects; D016158:Genes, p53; D005838:Genotype; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008938:Mitosis; D016133:Polymerase Chain Reaction; D011836:Radiation Tolerance; D051381:Rats; D013997:Time Factors
D001973:Bromodeoxyuridine