Mutant mouse provides insights into breast cancer

Dec 11, 2006

By discovering a mutant mouse that is highly susceptible to mammary tumors, Cornell researchers have found a novel potential link between genetic defects in DNA replication (copying) and breast cancer.

The mouse contains a mutation in a gene essential for replicating DNA in both humans and mice that increases the rate of flawed copies of genetic material, leading to mouse breast cancers.

In a paper published in Nature Genetics online (and upcoming in the Dec. 27 print issue), the Cornell geneticists report that by extensively testing hundreds of mice pedigrees, they found a mutant line of mice called Chaos3 that had a 20-fold increase in a hallmark for cancer called genomic instability -- a blanket term for an elevation in the number of mutations, chromosomal aberrations or loss of integrity of genetic information that occur when DNA replicates. While the Chaos3 mice appear normal in every way, the females are highly predisposed to mammary tumors.

"It's known that most cancers, by the time you look at them, have genomic instability in some form or another," said John Schimenti, a genetics professor in Cornell's Departments of Biomedical Sciences, and Molecular Biology and Genetics and the paper's senior author. "Our research demonstrated that genomic instability is probably leading to these cancers."

Schimenti and colleagues found that in the Chaos3 mice, the DNA codings in a gene called Mcm4 were partially impaired. The Mcm4 gene is one of six related Mcm genes that play essential roles in replication and were originally discovered at Cornell in baker's yeast (S. cerevisiae). The genes have remained largely unchanged throughout evolution and are evident in archaebacteria, yeast, mammals and more. It is unknown why the impaired Mcm4 genes in the Chaos3 mice led exclusively to breast cancer, Schimenti said.

Mcm4 is essential for DNA replication and thus cell growth, according to Schimenti. Partially impaired Mcm4 genes, however, allow Chaos3 mice to live normal lives but greatly increase the rate of faulty DNA replications and genomic instability.

"It's insidious because there is no warning that one might have this cancer predisposing allele [DNA codings at a given site] because the mice live normally," said Schimenti, who is also director of the Center for Vertebrate Genomics.

The researchers plan to study further the other Mcm genes to see if they, too, play a role in cancers.

The Mcm genes were discovered by Cornell professor of molecular biology Bik Tye, while the pathology of the mouse tumors was performed by Ana Alcaraz, a veterinarian in Cornell's Section of Anatomic Pathology in the Department of Biomedical Sciences.

Source: Cornell University

Explore further: Researchers map 'switches' that shaped the evolution of the human brain

add to favorites email to friend print save as pdf

Related Stories

New nanodevice defeats drug resistance

Mar 02, 2015

Chemotherapy often shrinks tumors at first, but as cancer cells become resistant to drug treatment, tumors can grow back. A new nanodevice developed by MIT researchers can help overcome that by first blocking ...

We're all mammals – so why do we look so different?

Feb 23, 2015

It is easy to distinguish a mouse from a cow. But for members of the same class of mammal, where do such differences begin? In 2011, scientists discovered there were differences in cow and mice blastocysts, the ti ...

Evolving a bigger brain with human DNA

Feb 19, 2015

The size of the human brain expanded dramatically during the course of evolution, imparting us with unique capabilities to use abstract language and do complex math. But how did the human brain get larger ...

A gene that shaped the evolution of Darwin's finches

Feb 11, 2015

Researchers from Princeton University and Uppsala University in Sweden have identified a gene in the Galápagos finches studied by English naturalist Charles Darwin that influences beak shape and that played ...

Recommended for you

Mutation in APC2 gene causes Sotos features

6 hours ago

Sotos syndrome is a congenital syndrome that is characterized by varying degrees of mental retardation and a large head circumference etc. It is known that 90% of Sotos syndrome patients have mutations in ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.