To investigate how miR-31 influences thyroid tumorigenesis and dedifferentiation process in BRAFV600E-driven thyroid cancer, Zhang et al. (60) crossed TPO-CreERT2 (33), BrafCA (29) and miR-31f/f (61) mice to generate the transgenic line TPO-CreERT2/BrafCA/miR-31f/f. The gene discussed is TPO; the disease is thyroid gland carcinoma.