Comparing these four models suggests that at least one gene in the region that is trisomic in both Ts1Cje and Ts65Dn mice but is not trisomic in Ts1Rhr mice (Sod1 to Setd4 and Ripk4 to Zbtb21) contributes to cerebellar hypoplasia. The gene discussed is ZBTB21; the disease is Cerebellar hypoplasia.