The equilibrium of WT1 isoform ratio is a key factor of the functions of this gene in different tissues, as evident for example by Frasier syndrome where a bi-allelic point mutation in the splice donor of exon 9 results in disturbance of WT1+/+/WT1+/− and WT1−/+/WT1−/− ratios, leading to major complications such as male pseudo-hermaphroditism and progressive glomerulopathy [48,49]. This evidence concerns the gene WT1 and Frasier syndrome.