The Immortality of the Germ Line: The Neverending Story

This is a short review concerning the problem of germ line “immortality,” which was already formulated by A. Weismann at the end of the 19th century. Over the following years, it attracted the attention of many gerontologists, who tried to understand the mechanisms of infinite transfer of genetic information from generation to generation with the help of germ cells, which, in contrast to somatic cells, avoid aging in this way. However, it remained unclear how the germ cells of women, which are in fact a population of non-dividing cells (it is similar to stationary phase aging non-subcultured cell culture), provide the mentioned immortality of the germ line. Distinguished Russian gerontologist Zh.A. Medvedev, who passed away recently, published in 1981 his brilliant work “On the Immortality of the Germ Line: Genetic and Biochemical Mechanisms. A Review,” the main points of which are relevant up to today. His paper just discusses the possible mechanisms of such “immortality.” They are analyzed in detail in the current article and can be reduced mainly to the existence of a number of barriers that, in most cases, do not allow progeny to emerge from “old” germ cells (although certain “rejuvenating” processes in the gametes still go). Therefore, children are “born young.” Some alternative approaches to explaining the immortality of the germ line are also considered. Special attention is paid to the “parental age effect” and the role of eggs and sperm cells in this phenomenon.