The microRNA miR-235 couples blast-cell quiescence to the nutritional state

The coordination of stem- and blast-cell behaviours, such as self-renewal, differentiation and quiescence, with physiological changes underlies growth, regeneration and tissue homeostasis. Germline stem and somatic blast cells in newly hatched Caenorhabditis elegans larvae can suspend postembryonic development, which consists of diverse cellular events such as migration, proliferation and differentiation, until the nutritional state becomes favourable (termed L1 diapause). Although previous studies showed that the insulin/insulin-like growth factor (IGF) signalling (IIS) pathway regulates this developmental quiescence, the detailed mechanism by which the IIS pathway enables these multipotent cells to respond to nutrient availability is unknown. Here we show in C. elegans that the microRNA (miRNA) miR-235, a sole orthologue of mammalian miR-92 from the oncogenic miR-17-92 cluster, acts in the hypodermis and glial cells to arrest postembryonic developmental events in both neuroblasts and mesoblasts. Expression of mir-235 persists during L1 diapause, and decreases upon feeding in a manner dependent on the IIS pathway. Upregulation of one of the miR-235 targets, nhr-91, which encodes an orthologue of mammalian germ cell nuclear factor, is responsible for defects caused by loss of the miRNA. Our findings establish a novel role of a miR-92 orthologue in coupling blast-cell behaviours to the nutritional state.