Year: 2015
Type: dissertation
Abstract: Fanconi anemia (FA) is a genetic disorder caused by biallelic mutations in one of the 15 known FA genes. FA-D1 is identical to BRCA2 and is in fact the same gene. The FA-D1/BRCA2 gene is known to be involved in cellular pathways such as homologous recombination repair of double strand DNA breaks, stabilization of nascent DNA strands at stalled replication forks and also in telomere maintenance and integrity. In the Icelandic population a germline mutation 999del5 in the BRCA2 gene is known to increase breast cancer predisposition as well as other cancer types. \n \nThe aim of this study was to analyze differences in chromosomal stability and telomere maintenance between different BRCA2 genotypes. Human lymphocyte cell lines of different BRCA2 genotypes (wild-type BRCA2+/+, heterozygous BRCA2+/- and homozygous BRCA2-/- of FA-D1 origin) were used and analyzed for chromosomal stability either untreated or after treatment with Mitomycin C, a DNA crosslinking agent. Chromosomes were harvested and chromosomal abnormalities analyzed using solid Leishman staining on metaphase spreads and dysfunctional telomeres were analyzed using PNA-FISH method, also on metaphase spreads. Results showed that the homozygous BRCA2-/- cell line showed significantly increased DNA breaks and chromosomal end-to-end fusions compared to the heterozygous BRCA2+/- and/or wild-type BRCA2+/+ cell lines after Mitomycin C treatment, but no difference was found between the wild-type BRCA2+/+ and the heterozygous BRCA2+/- cell lines. Significant stepwise increase was found in telomere dysfunction after Mitomycin C treatment in regard to the BRCA2 genotype, starting from the wild-type BRCA2 cell lines with the lowest frequency of telomere signal loss from chromosome ends and interstitial telomere sequences to the highest frequency in the homozygous BRCA2 cell line. These results support that BRCA2 has a role in keeping genetic integrity and telomere maintenance, indicating that BRCA2s role in telomere maintenance might be of a more delicate nature than homologous recombination repair of DSB since the 999del5 germline mutation seems to have a greater impact on telomere dysfunction than chromosomal abnormalities. Therefore possible dysfunctional telomere maintenance among BRCA2 mutation carriers may be resulted from BRCA2 haploinsufficiency.
Source: Skemman
Author: Hörður Bjarnason
Language: English
Topic: DNA Repair Mechanisms
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2596460688