Scientists at the Albert Einstein College of Medicine of Yeshiva University have observed for the first time that gene expression can occur in the form of discrete "pulses" of gene activity.
The researchers used pioneering microscopy techniques, developed by Dr. Robert Singer and colleagues at Einstein, that for the first time allow scientists to directly watch the behavior of a single gene in real time. Their findings appeared in the current issue of Current Biology.
When a gene is expressed or "turned on," genetic information is transferred from DNA into RNA. This process, known as transcription, is crucial for translating the gene's message into a functional protein. Diseases such as cancer can result when genes turn on at the improper time or in the wrong part of the body.
Researchers customarily use microarrays (also known as "gene chips") to assess gene expression in tumors and other tissues. But with millions of cells involved, microarrays reflect only "average" gene expression. Just how a gene is transcribed in a single cell--continuously, intermittently or some other way--has largely been a mystery.
Now, in observing a gene that plays a major role in how an organism develops, the Einstein researchers observed a phenomenon that until now has been indirectly observed and only in bacteria: pulses of transcription that turn on and off at irregular intervals. Dr. Singer and his co-workers used a fluorescent marker that sticks to the gene only when it is active. Under a microscope, this fluorescent marker appears when the gene turns on, then disappears (gene "off") and then appears again (gene "on").
The focus of the study was a gene important in the life cycle of the social amoeba Dictyostelium, thousands of which sometimes aggregate into a single slug-like mass. This developmental gene plays a major role in transforming the "slug" into a stalk-like structure called a fruiting body, which releases new amoebae.