Similar to data observed in the NUDT21 CNV patient lymphoblasts, NUDT21 loss of function also results in the 3′ UTR shortening of MECP2 in human neurons, as well as other genes strongly regulated by NUDT21 in cancer-cell-line assays, such as VMA21 and PAK1 (Figure 6Aii-iv; Chu et al., 2019; Gennarino et al., 2015; Masamha et al., 2014). Here, PAK1 is linked to cancer.