A volatile morphogen directly activates RyR1 to regulate epimorphic regeneration in vertebrates

Volatile small‐molecule morphogens have been used for systemic control of morphogenesis since the early twentieth century. Genetic and pharmacological evidence has linked these compounds to several bioelectric conduits, including inward-rectifier K+ channels and proton pumps, yet additional effectors are likely to participate in the global regulation of pattern formation. Missense mutations in the type 1 ryanodine receptor (RyR1), an endoplasmic-reticulum Ca2+ release channel, underlie a spectrum of congenital myopathies that often present with defective tissue repair. Whether volatile morphogens engage RyR1 directly, however, has remained unclear. Here we show that isoflurane and related volatiles potently gate wild-type RyR1 purified from vertebrate muscle and reconstituted into planar bilayers. Systematic alanine scanning identified a single conserved residue whose substitution abolishes isoflurane-evoked Ca2+ flux, delimiting a probable binding pocket within the transmembrane core. Axolotls engineered to carry the isoflurane-insensitive RyR1 variant failed to enter the characteristic 48-h proliferative pause that normally follows systemic exposure to the morphogen, and regenerated amputated limbs with unperturbed kinetics. These findings indicate that RyR1 activation is required for the in vivo suppression of epimorphic outgrowth. Live-imaging of blastema cells expressing a genetically encoded Ca2+ sensor revealed that isoflurane elicits rapid, RyR1-dependent Ca2+ transients that precede transcriptional down-regulation of fgf8 and msx1. Newly synthesized RyR1 agonists that engage the same site reproduced both the Ca2+ signature and the reversible halt in distal pattern elaboration. We propose that direct chemical gating of RyR1 constitutes an actionable node in the circuitry that times vertebrate regeneration, offering a molecular foothold for clinical modulation of wound repair and congenital repair deficiencies.