Interlocked transcription factor feedback loops maintain and restore touch sensation
The sense of touch relies on the continuous function of specialized mechanosensory circuits, but the underlying molecular mechanisms remain poorly understood. Here, we report that the conserved transcription factors (TFs) CFI-1 (ARID3) and EGL-5 (HOXA7) jointly maintain in adult C. elegans the molecular identity of two key interneuron types, securing information processing within a mechanosensory circuit. Toggling between normal and low levels of CFI-1 or EGL-5 in adults generated digital-like (ON/OFF) effects both on touch-evoked escape response and interneuron identity. Strikingly, reintroduction of CFI-1 following its prolonged depletion restored escape response defects. Mechanistically, we identified two network motifs, a double-positive CFI-1/EGL-5 feedback loop and positive CFI-1 autoregulation, which together "lock-in" the interneuron identity programs. We propose that these interlocked motifs not only maintain robust escape responses throughout life, but are also essential for the restorability of adult-onset touch defects. Altogether, this work illuminates the molecular principles that maintain adult neuron identity and circuit function, and offers biomedically relevant insights into the restorability of neuronal and behavioral defects caused by mutations or variation in TF-encoding genes.