Here, we show that active elimination of unfit cells is required to
maintain tissue health during development and adulthood. We
identify a gene (azot), whose expression is confined to suboptimal
or misspecified but morphologically normal and viable cells.
When tissues become scattered with suboptimal cells, lack of
azot increases morphological malformations and susceptibility
to random mutations and accelerates age-dependent tissue
degeneration. On the contrary, experimental stimulation of azot
function is beneficial for tissue health and extends lifespan.
Therefore, elimination of less fit cells fulfils the criteria for a hallmark
of aging (Lo´ pez-Otı´n et al., 2013)