CNS‐specific LoF of Med27 resulted in severe brain structural defects, with the most prominent feature being cerebellar agenesis (Figure 4), consistent with the homogenous cerebellar abnormalities observed in MED27 patients.[9, 11] Given that these mice were not viable after birth, we generated cerebellum‐specific LoF Med27 mice, which successfully recapitulated the progressive motor deficits and cerebellar atrophy phenotypes seen in MED27 patients (Figure 5; Figures S6–S9, Supporting Information). This evidence concerns the gene MED27 and Cerebellar atrophy.