Non-apoptotic caspase activation sustains ovarian somatic stem cell functions by modulating Hedgehog-signalling and autophagy.

There is increasing evidence associating the activity of caspases with the regulation of basic cellular functions beyond apoptosis. Accordingly, the dysregulation of these novel non-apoptotic functions often sits at the origin of neurological disorders, metabolic defects, autoimmunity, and cancer. However, the molecular interplay between caspases and the signalling networks active in non-apoptotic cellular scenarios remains largely unknown. Our work show that non-apoptotic caspase activation is critical to modulate Hedgehog-signalling and autophagy in ovarian somatic cells from both Drosophila and humans under moderate stress. We also demonstrate that these novel caspase functions are key to sustain stem cell proliferation and differentiation without inducing apoptosis. Finally, we molecularly link these caspase-dependent effects to the fine-tuning of the Hedgehog-receptor, Patched. Together, these findings confer a pro-survival role to the caspases, as opposed to the widely held apoptotic function assigned to these enzymes.