Chromosome Research On Flies Yields Insights Into Human Diseases

Dr. Shelagh Campbell, from the U of A's Department of Biological Sciences, is a basic researcher who studies how normal cell cycles are regulated, by analyzing genes that are responsible for repairing DNA damage that offer insights into human diseases like cancer and A-T.

A-T is a progressive, degenerative disease that affects a startling number of body systems. Children with A-T appear normal at birth but at around the age of two, some of the first signs--walking and balance is wobbly caused by ataxia or lack of muscle control--start appearing.

"Kids are often misdiagnosed with cerebral palsy but what distinguishes A-T is it gets worse," said Campbell. "Sadly, many of the people with A-T end up in wheelchairs and most die young (I think there is a fair range).

Soon after the onset of A-T, children lose their ability to write and speech becomes slow and slurred. Reading eventually becomes impossible because eye movements are too hard to control. Other features of the debilitating disease include mild diabetes, premature graying of the hair, difficulty swallowing causing choking and drooling and slowed growth. Children with A-T also tend to be more predisposed to developing cancer. Ironically, the disease carries with it sensitivity to radiation, which means A-T patients cannot tolerate the therapeutic radiation usually given to cancer patients.

That's where Campbell hopes to apply her work. Scientists already know that the A-T protein (ATM) is fundamental to repairing DNA damage so she and her research team are studying ATM mutants, which behave as cells do when they are damaged.

In a recent issue of the journal, "Current Biology," Campbell describes how they examined ATM mutants for signs of locomotor defects in mutant and control flies and found the average climbing ability to be lower for the mutant males. Aside from locomotor defects, the mutants recapitulated major symptoms of the disease, A-T, including sensitivity to ionizing radiation and chromosome instability.

"If you want to study a conserved biological process, it makes sense to do it in a system where you can do all these genetic tricks," said Campbell of being able to create mutant proteins and manipulate such factors as temperature. "We have an excellent model for investigating the basic mechanisms of chromosome structural maintenance involving ATM, allowing us to study how ATM works in a meaningful developmental context."

Although a cure seems to be a long way off, using this system to understand more about how ATM works will offer more clues to treating the disease, said Campbell. "There are some serious efforts being made for treatment of A-T and what we learn may also make it easier to screen for known carriers," she said. "My hope is by fully understanding how ATM functions, at least we can look at improving the quality of life for those unfortunate to receive mutant alleles from both their parents. That's the million dollar question--how does ATM work, and we're slowly getting closer to understanding it."