Somatic nuclear blebbing may indicate proliferating germ cells but does not indicate organismal aging in Caenorhabditis elegans

Abnormal nuclear morphology is suggested to be a hallmark of aging. One type of such abnormalities is nuclear blebbing, but little is known about whether and how nuclear blebbing participates in animal aging. What regulates nuclear blebbing is also unknown. In this study, we show that the frequency of nuclear blebbing in the hypodermis increases during aging in wild-type C. elegans. These nuclear blebs are enveloped by the nuclear lamina, the inner and the outer nuclear membrane, and 42% of them contain chromatin. Detachment of a bleb from the nucleus is rare but does happen, thereby generating cytoplasmic chromatin. Cytoplasmic chromatin-containing lysosomes juxtaposing the nucleus are detected in old worms. Therefore, nuclear blebbing contributes to the age-associated chromatin loss. However, the frequency of nuclear blebbing does not correlate with the rate of aging in C. elegans. Old age does not necessarily induce nuclear blebbing, neither does starvation, heat stress, or oxidative stress. Intriguingly, we find that proliferation of germ cells promotes nuclear blebbing. HighlightsO_LINuclear blebs accumulate in the hypodermis during C. elegans aging C_LIO_LINuclear blebbing contributes to chromatin loss C_LIO_LIThe frequency of nuclear blebbing does not correlate with the rate of aging C_LIO_LIProliferating germ cells promote nuclear blebbing in the hypodermis C_LI