A study published in the November issue of Nature Genetics provides an example for a faster route to cancer, involving a mutation in a single copy of a susceptibility gene. Hans Joenje and colleagues examine the genetic basis of inherited cases of Fanconi anemia, a rare genetic disorder characterized by congenital defects, progressive bone marrow failure and cancer susceptibility. The authors find that a gene associated with disease is located on the X chromosome. This is significant because males carry only one copy of the gene, and females - despite having two copies of the gene - will have only one active copy in each cell. This gene may also be important in sporadic cases of cancer, since a single 'hit' (mutation) may be sufficient to promote cancer formation, as opposed to the traditional 'two hits' needed to inactivate tumor suppressor genes carried on other chromosomes.
Previously, the disease was thought to be unlinked to the sex chromosomes. Males inheriting the newly identified mutation will be at higher risk for disease, given that they carry only one copy of the X chromosome, and would therefore express only the mutant protein. The authors also show that one copy of this gene is inactivated in some cell types in females though a process known as X-inactivation, such that female carriers of the mutation may express either the normal or mutant protein in any given cell. There may be selection against cells carrying only mutant protein, which are likely to have genomic instability and be prone to cancer transformation.
Hans Joenje (VU University Medical Center, Amsterdam, The Netherlands)
Tel: +31 20 444 8270 / +31 20 444 8273, E-mail: email@example.com
Also available online.
(C) Nature Genetics press release.
Message posted by: Trevor M. D'Souza
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