Molecular insights into the transgenerational inheritance of stress memory

There is accumulating evidence to show that environmental stressors can regulate a variety of phenotypes
in descendants through germline-mediated epigenetic inheritance. Studies of model organisms exposed to
environmental cues (e.g., diet, heat stress, toxins) indicate that altered DNA methylations, histone modifications, or non-coding RNAs in the germ cells are responsible for the transgenerational effects. In addition,
it has also become evident that maternal provision could provide a mechanism for the transgenerational
inheritance of stress adaptations that result from ancestral environmental cues. However, how the signal of
environmentally-induced stress response transmits from the soma to the germline, which may influence
offspring fitness, remains largely elusive. Small RNAs could serve as signaling molecules that transmit
between tissues and even across generations. Furthermore, a recent study revealed that neuronal mitochondrial perturbations induce a transgenerational induction of the mitochondrial unfolded protein
response mediated by a Wnt-dependent increase in mitochondrial DNA levels. Here, we review recent work
on the molecular mechanism by which parental experience can affect future generations and the importance of soma-to-germline signaling for transgenerational inheritance.