Back to immortality: the restoration of embryonic telomere length during induced pluripotency

The dichotomy of cell fates in the soma versus the germline has attracted the interest of researchers since the birth of cell biology in the 19th century. The German naturalist August Weismann proposed that hereditary information was transported via a perpetual continuum of germline cells while somatic cells played a subservient role of providing support to the reproductive cells, and then being discarded each generation. Weismann suggested that since there is a pattern in nature of ‘use it or lose it’ (i.e., the loss of vision in crayfish confined to the darkness of caves), natural selection led to the loss of the capacity for indefinite replication in somatic cells where it was no longer required. He designated these dichotomous phenotypes cellular ‘immortality’ and ‘mortality’ [1–3]. It took Leonard Hayflick’s careful studies 80 years later to convince the scientific community that Weismann’s prediction was correct and that human somatic cells are in fact mortal in vitro [4–6].