Several of the genes downregulated in Dmdo/Dmdo mice at P4, including Ptprq, Gfi1, Kcna10 and Slc26a5 (prestin), cause deafness when mutated7, 8, 9, 10 and some of the unique characteristics of mice null for these genes are replicated in the diminuendo mouse, such as the short outer hair cells of prestin mutants6, 9, and the delay in hair cell stereocilia differentiation seen in Ptprq functional nulls11. Here, GFI1 is linked to deafness.