In summary, our results demonstrate that miR-31 inhibits pTreg-cell generation through directly targeting Gprc5a, a retinoic acid-inducible protein and promotes autoimmunity, therefore, providing the first in vivo genetic evidence that miR-31 and its novel target Gprc5a are critical intrinsic factors for controlling physiological and pathological immune responses regulated by pTreg cells. The gene discussed is GPRC5A; the disease is Autoimmunity.