Medical Discovery News
By Drs. David Niesel and Norbert Herzog
Many think their genetic information is permanent, that whatever we inherit from our parents gene-wise is what we are stuck with — that genes don’t change. But that’s not the case. Genes can not only change throughout our lives, but they can move or jump from one place in the genome to another. Science shows these jumping genes are linked to certain diseases in humans, but they may have positive effects as well.
Most genes are located in the same place on the same chromosomes in everyone. But small pieces of DNA called retrotransposons, or jumping genes, can relocate to other parts of the genome. In their new locations, they can stay silent, create their own products, or alter the activity of nearby genes. Jumping genes have been implicated in some cancers and neurological disorders.
Autopsies of people with schizophrenia showed their brains had more of these jumping genes than other people. Furthermore, the more a schizophrenic had been exposed to environmental factors known to influence schizophrenia, the more jumping genes they had. Schizophrenia is a condition that can cause hallucinations, delusions and cognitive defects and occurs in about 1 percent of people. A number of genes and environmental factors are associated with developing schizophrenia.
One such jumping gene called LINE-1 retrotransposon (L1) is particularly abundant in brain stem cells that form into neurons. It is estimated that the human genome has over 500,000 copies of L1. Most of these copies are defective, but about 100 are active and able to produce additional L1 that can jump to other locations. People with a form of autism called Rett syndrome and those with a neurological motor disease called Louis-Bar syndrome have increased L1. Now, scientists have documented that schizophrenics also have increased L1.
Scientists wanted to know whether the increased L1 levels were due to environmental factors or the development of schizophrenia. First, they injected pregnant mice with a molecule that simulates a viral infection. The offspring of these mice had elevated levels of L1 in their brains. In other experiments, they exposed monkeys to a hormone that raises the risk for schizophrenia, and they also had increased L1. This study revealed that in schizophrenia, L1 reinserts into genes involved in synaptic function, the transmission of signals between neurons. This would disrupt the communication between brain cells.
This new study did not reveal whether elevated and relocated L1 is a cause or an effect of schizophrenia and other neuropsychiatric diseases. But it has raised an intriguing question: do these jumping genes also play a normal role in the developing brain and in the variety of cognitive skill levels humans and other animals display?
For example, inbred mice raised in the exact same environment should be identical, yet they can behave differently. As it turns out, jumping genes seem to be responsible for the differences scientists observe by generating diversity in brain cells, which may be important in brain development. Additionally, they may allow the brain to be more adaptable to new situations. If L1 is in just the right place, does it contribute to mental genius, like that of Albert Einstein, Wolfgang Amadeus Mozart and Leonardo da Vinci?
Medical Discovery News is a weekly radio and print broadcast highlighting medical and scientific breakthroughs hosted by professor emeritus Norbert Herzog and professor David Niesel, biomedical scientists at the University of Texas Medical Branch at Galveston. Learn more at www.medicaldiscoverynews.com.