For example zebrafish potassium channel tetramerization domain containing 13 (kctd13) was shown to have a dose-dependent affect in producing macrocephaly (knockdown) and microcephaly (overexpression) that supports a role for KCTD13 copy number variants causing head size phenotypes (Golzio et al., 2012). This evidence concerns the gene KCTD13 and microcephaly.