The researchers believe their discovery could lead to improved therapy and diagnosis in other colon cancers.
The gene, discovered by researchers at the University of Iowa and colleagues from the Johns Hopkins Oncology Center in Baltimore, Maryland, USA, and the Mayo Clinic in Minneapolis, USA, is the second known to cause juvenile polyposis (JP). Taken together, the two mutations cause nearly half of the cases of the condition.
The new gene, which codes for a protein called 'bone morphogenetic protein receptor 1A' (BMPR1A), was discovered using genetic linkage studies that compare the inheritance of specific DNA markers from different chromosomes in families with the disease.
Using four families and the Human Genome Project, the researchers isolated the gene to chromosome 10, and then BMPR1A, which is a cousin of the first gene associated with JP.
In the families, they found that those who had the disease also had the gene mutations, but it was missing in those without JP.
|Bone morphogenetic protein receptor 1A is associated with JP.|
Each family had a different mutation, but they all had a shortened protein that could not do its job in the BMP biochemical pathway.
However, lead researcher, Dr James Howe, Associate Professor of Surgery at Iowa University, believes there are more genes that cause the condition, and he will continue searching for them.
Writing in the June issue of Nature Genetics, Dr Howe said, "There is another Iowa family that is large enough for linkage analysis who don't have mutations in either of the two identified genes. They might represent the large group of JP patients who just have polyps in the colon. If we're lucky, a single gene will explain these remaining cases."
The researchers will now develop a mouse model for JP to pursue genetic linkage studies and investigate gene expression patterns, which could help test pharmacological agents designed to treat the condition - or even colon cancer.
Dr Howe said because JP abnormalities occurred in the layer beneath the lining of the colon, understanding how the polyps and cancers developed could expose a new cause of colon cancer in the generation population.
"This understanding might also suggest new targets for therapy and for diagnosis," he commented.
He added that the gene discovery gave doctors a better way of screening patients with a family history of the disease before symptoms appear.
"It is very helpful to be able to pay more attention to those people with the genetic mutation for JP who are at high risk for developing cancer. Also, it is reasonable to substantially reduce expensive and uncomfortable screening for those people who don't have the mutation," he said.
"In this condition, colorectal cancer can be prevented by screening and aggressive removal of polyps," Howe concluded.
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