Analysis of the genetic interactions between Cyclin A1, Atm and p53 during spermatogenesis.
OBJECTIVE
To analyze the functional interactions of Cyclin with p53 and Atm in spermatogenesis and DNA double-strand break repair.


METHODS
Two lines of double knockout mice were generated. Spermatogenesis and double strand break repair mechanisms were analyzed in Cyclin A1 (Ccna1); p53- and Ccna1; Atm-double knockout mice.


RESULTS
The block in spermatogenesis observed in Cyclin A1-/- (Ccna1-/-) testes at the mid-diplotene stage is associated with polynucleated giant cells. We found that Ccna1-deficient testes and especially the giant cells accumulate unrepaired DNA double-strand breaks, as detected by immunohistochemistry for phosphorylated H2AX. In addition, the giant cells escape from apoptosis. The development of giant cells occurred in meiotic prophase I, because testes lacking ATM, which are known to develop spermatogenic arrest earlier than prophase I, do not develop giant cells in the absence of cyclin A1. Cyclin A1 interacted with p53 and phosphorylated p53 in complex with CDK2. Interestingly, p53-deficiency significantly increased the number of giant cells in Ccna1-deficient testes. Gene expression analyses of a panel of DNA repair genes in the mutant testes revealed that none of the genes examined were consistently misregulated in the absence of cyclin A1.


CONCLUSIONS
Ccna1-deficiency in spermatogenesis is associated with defects in DNA double-strand break repair, which is enhanced by loss of p53.
Baumer
Nicole
N
Department of Medicine, Hematology and Oncology, University of Munster, Domagkstr. 3, D-48129 Munster, Germany.
Sandstede
Marie-Luise
ML
Diederichs
Sven
S
Kohler
Gabriele
G
Readhead
Carol
C
Ji
Ping
P
Zhang
Feng
F
Bulk
Etmar
E
Gromoll
Jorg
J
Berdel
Wolfgang E
WE
Serve
Hubert
H
Muller-Tidow
Carsten
C
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D019925:Cyclin A / Q000235:genetics* / Q000378:metabolism; D056750:Cyclin A1; D019926:Cyclin B; D056765:Cyclin B2; D004247:DNA / Q000235:genetics; D004260:DNA Repair / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D013091:Spermatogenesis / Q000235:genetics* / Q000502:physiology; D013737:Testis / Q000166:cytology / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
C503747:Ccna1 protein, mouse; C503759:Ccnb2 protein, mouse; D018797:Cell Cycle Proteins; D019925:Cyclin A; D056750:Cyclin A1; D019926:Cyclin B; D056765:Cyclin B2; D004268:DNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D004247:DNA; D064007:Ataxia Telangiectasia Mutated Proteins; C576325:Atm protein, mouse; D017346:Protein Serine-Threonine Kinases