To deepen the understanding of the effect of the ZNF687 mutation on bone metabolism, we generated a knock-in mouse model harboring the c.2810C>G (P937R) mutation detected in GCT/PDB patients.14,20 The mutation has been introduced through site-directed mutagenesis in the targeting vector containing arms of the homologous Zfp687 mouse gene, exploiting the 80.4% nucleotide homology between the human and mouse genes, even higher (84%) at exon 6, where the mutation is located (Fig. S1a, b). The gene discussed is ZNF687; the disease is granular cell tumor.