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Molecular and Cellular Biology, September 2006, p. 6983-6992, Vol. 26, No. 18
0270-7306/06/$08.00+0 doi:10.1128/MCB.00796-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
11 Isoform
Genetics of Development and Disease Branch, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, 10/9N105, 10 Center Drive, Bethesda, Maryland 20892,1 Department of Pathology, College of Medicine, Chosun University, Gwangju 501-759,2 Division of Radiation and Nuclear Medicine, National Cancer Center, Goyang, Gyeonggi 411-769, South Korea3
Received 5 May 2006/ Returned for modification 18 June 2006/ Accepted 30 June 2006
Alternative splicing in the BRCA1 locus generates multiple protein products including BRCA1-
11, which is identical to the BRCA1 full-length isoform (BRCA1-FL) except for the absence of exon 11. Mutation analysis using gene targeting to create null mutations or disrupt BRCA-FL has provided much of our understanding of BRCA1 functions; however, targeted mutation of specific short forms of BRCA1 has not been reported. To understand the physiologic functions of BRCA1-
11, we used a knock-in approach that blocks alternative splicing between exons 10 and 12 to prevent the formation of this form of BRCA1. We showed that homozygous mutant mice (Brca1FL/FL) were born at a Mendelian ratio without obvious developmental defects. However, the majority of Brca1FL/FL female mice showed mammary gland abnormalities and uterine hyperplasia after one year of age with spontaneous tumor formation. Cultured Brca1FL/FL cells exhibited abnormal centrosome amplification and reduction of G1 population that was accompanied by accumulation of cyclin E and cyclin A. Accumulation of cyclin E was also found in epithelial layers of dilated ducts and hyperproliferative lobular regions in the mammary glands of Brca1FL/FL mice. These observations provide evidence that BRCA1 splicing variants are involved in BRCA1 functions in modulating G1/S transition, centrosome duplication, and repressing tumor formation.
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