饥饿的“记忆”可通过基因遗传

During the winter of 1944, the Nazis¹ blocked food supplies to the western Netherlands, creating a period of widespread famine（饥荒） and devastation². The impact of starvation on expectant mothers produced one of the first known epigenetic（后生的） "experiments" -- changes resulting from external rather than genetic³ influences -- which suggested that the body's physiological⁵ responses to hardship could be inherited. The underlying⁶ mechanism⁷, however, remained a mystery. In a paper published recently in the journal Cell, Dr. Oded Rechavi, Dr. Leah Houri-Ze'ev, and Dr. Sarit Anava of Tel Aviv University's Faculty⁸ of Life Sciences and Sagol School of Neuroscience, Prof. Oliver Hobert and Dr. Sze Yen⁹ Kerk of Columbia University Medical Center and the Howard Hughes Medical Institute, and Dr. Wee Siong Sho Goh and Dr. Gregory J. Hannon of the Cold Spring Harbor Laboratory and the Howard Hughes Medical Institute, explore a genetic mechanism that passes on the body's response to starvation to subsequent generations of worms, with potential implications for humans also exposed to starvation and other physiological challenges, such as anorexia¹⁰ nervosa（神经性厌食症）.   "There are possibly several different genetic mechanisms¹¹ that enable inheritance of traits in response to changes in the environment. This is a new field, so these mechanisms are only now being discovered," said Dr. Rechavi. "We identified a mechanism called 'small RNA inheritance' that enables worms to pass on the memory of starvation to multiple generations."   Does RNA have a memory?   RNA molecules¹² are produced from DNA¹³ templates in response to the needs of specific cells. "Messenger" RNA molecules (mRNAs) contain instructions for the production of proteins, which service cells and allow them to function. But other RNA molecules have different regulatory functions. Small RNAs are one species of these regulatory RNAs -- short molecules that regulate gene⁴ expression, mostly by shutting genes¹⁴ off, but sometimes by turning them on.   Dr. Rechavi first became interested in studying starvation-induced epigenetic responses following a discovery made as a post doctorate¹⁵ in Prof. Hobert's lab at Columbia University Medical Center in New York. "Back then, we found that small RNAs were inherited, and that this inheritance affected¹⁶ antiviral immunity^{17#p#分页标题#e#} in worms. It was obvious that this was only the tip of the iceberg," he said.   In the course of the new study, worms (C.elegans nematodes) were starved early in their development. They responded by producing small RNAs, which function by regulating genes through a process that is known as RNA interference (RNAi). The researchers discovered that the starvation-responsive small RNAs target genes that are involved in nutrition. More important, the starvation-induced small RNAs were inherited by at least three subsequent generations of worm specimens¹⁸.