For example, truncating mutations in exons prior to exon 8, which contains the Ocrl1 translation initiation start site, leads to preservation of >50% enzyme activity and the milder phenotype of Dent 2 while mutations after exon 8 lead to <20% enzyme activity and the more severe phenotype of Lowe syndrome (Sakakibara et al., 2022). This evidence concerns the gene OCRL and oculocerebrorenal syndrome.