Research Roundup

A new column will periodically summarize projects that have been singled out by the Schools. The notes below are from releases prepared by Franklin Hoke of the School of Medicine's Office of Public Affairs.--Ed.

Mobile Elements in 'Junk DNA'

About 95 percent of the human genome is estimated to be non-coding, meaning that it appears to play no direct role in producing the proteins that constitute the body and conduct its life processes. Among these vast stretches of genetic material--once erroneously referred to as junk DNA--are about 100,000 sequences known as long interspersed nuclear elements, or L1 elements. Most L1 sequences are thought to be inert, but two have been shown previously by researchers at Penn to be active and mobile, capable of jumping from one location in the genome to another where they then randomly reinsert themselves.

Now, using several innovative assay techniques, the Penn group has raised the number of known active L1 elements to seven. Based on the new findings (May issue of Nature Genetics), they estimate that as many as 30 to 60 active L1 elements may reside in the total human genome. L1's purpose is unclear, but tantalizing clues suggest an important role of some kind: "There are sequences in these elements that are similar to sequences in certain bacteria, so from an evolutionary point of view they are very old," notes Dr. Haig H. Kazazian, Jr., chairman of genetics and senior author on the study. "And they have expanded in the last 50 million years or so, especially in mammals. We suspect they may be a key force for diversification during evolution--a mechanism, perhaps, for increasing the plasticity of the genome."

Limiting Damage after Brain Trauma

Of the nearly half-a-million people discharged from hospitals each year after treatment for head injuries, some 20 percent will suffer continuing disabilities. Hoping to find a therapy that might help people more fully recover, Dr. Grant Sinson, assistant professor of neurosurgery, injected nerve growth factor (NGF) over a 14-day period directly into the site of injury in an experimental model of brain injury in the rat. According to the study (March Journal of Neurosurgery) this led to marked improvements in post-traumatic memory of tasks learned prior to the injury--the amnesia that so often accompanies head injury was significantly attenuated, and apoptosis of the neurons was reduced dramatically. "These data are the first anywhere to show that a unique treatment such as this trophic-factor therapy can limit trauma-induced apoptotic cell death in the brain," said Dr. Tracy K. McIntosh, a professor of neurosurgery and director of the Head Injury Center at Penn and in whose laboratory Sinson performed his experiments. Beneficial effects of the treatment persisted even after administration of NGF was ended.

To Guam for ALS, Alzheimer's, Parkinson's

In 1945, just after World War II's end and only a few years after 37-year-old baseball player Lou Gehrig died in 1941 of amytrophic lateral sclerosis (ALS), military physicians stationed on the Pacific island of Guam identified a new neuro-degenerative disease, eventually named Lytico-Bodig, that appeared to combine some of the most fearsome symptoms of ALS, Alzheimer's, and Parkinson's diseases. Further study showed the disease struck Guam's minority Chamorro population at rates about 100 times higher than the U.S. incidence rates for the better known neurological diseases. Study has continued in the decades since, but answers have been elusive.

Now 35 scientists from six institutions have a cooperative grant from the National Institute on Aging to attack again the problem of the mysterious Guamanian disease--and, they hope, provide a critical boost to science's still-limited understanding of ALS, Alzheimer's, and Parkinson's. PennMed's Drs. Virginia M.-Y. Lee and John Q. Trojanowski ( see story in this issue) are among the eight principal investigators. The overall project is led by Drs. W.C. Wiederholt, California/San Diego, and Ulla-Katrina Craig at the University of Guam.


Volume 44 Number 1
July 15, 1997

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