CCDC88A and Hypsarrhythmia: In fact, GIV expression is highest in the brain, along with testis, across primary mouse tissues (185), and the main phenotype of mice lacking GIV is brain developmental defects that mimic the progressive encephalopathy with edema, hypsarrhythmia, and optic atrophy–like syndrome (183, 184), which results in premature death several weeks after birth in mice (186, 187, 188).