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Molecular and Cellular Biology, October 1999, p. 7061-7075, Vol. 19, No. 10
Curriculum in Genetics and Molecular
Biology,1 Department of
Medicine,2 Department of
Pathology,4 and Department of Radiation
Oncology,3 University of North Carolina at
Chapel Hill, Chapel Hill, North Carolina 27599
Received 2 February 1999/Returned for modification 31 March
1999/Accepted 22 June 1999
BRCA1 is a nuclear phosphoprotein expressed in a broad spectrum of
tissues during cell division. The inheritance of a mutant BRCA1 allele dramatically increases a woman's lifetime
risk for developing both breast and ovarian cancers. A number of mouse lines carrying mutations in the Brca1 gene have been
generated, and mice homozygous for these mutations generally die before
day 10 of embryonic development. We report here the survival of a small
number of mice homozygous for mutations in both the p53 and
Brca1 genes. The survival of these mice is likely due to
additional unknown mutations or epigenetic effects. Analysis of the
Brca1
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Copyright © 1999, American Society for Microbiology. All rights reserved.
Growth Retardation, DNA Repair Defects, and Lack of
Spermatogenesis in BRCA1-Deficient Mice
/
p53
/
animals
indicates that BRCA1 is not required for the development of most organ
systems. However, these mice are growth retarded, males are infertile
due to meiotic failure, and the mammary gland of the female mouse is
underdeveloped. Growth deficiency due to loss of BRCA1 was more
thoroughly examined in an analysis of primary fibroblast lines obtained
from these animals. Like p53
/
fibroblasts,
Brca1
/
p53
/
cells
proliferate more rapidly than wild-type cells; however, a high level of
cellular death in these cultures results in reduced overall growth
rates in comparison to p53
/
fibroblasts.
Brca1
/
p53
/
fibroblasts are
also defective in transcription-coupled repair and display increased
sensitivity to DNA-damaging agents. We show, however, that after
continued culture, and perhaps accelerated by the loss of BRCA1 repair
functions, populations of Brca1
/
p53
/
fibroblasts with increased growth rates can
be isolated. The increased survival of BRCA1-deficient fibroblasts in
the absence of p53, and with the subsequent accumulation of additional
growth-promoting changes, may mimic the events that occur during
malignant transformation of BRCA1-deficient epithelia.
*
Corresponding author. Mailing address: University of
North Carolina at Chapel Hill, 7007 Thurston-Bowles Bldg., CB#7248,
Chapel Hill, NC 27599. Phone: (919) 962-2153. Fax: (919) 966-7524. E-mail: Treawouns{at}aol.com.
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