RB1 and X-linked syndromic intellectual disability: Additional imaging markers predicting clinically relevant gene expression have also been identified, such as Ki-67 (Li et al. 2017), alpha thalassemia/mental retardation syndrome X-linked (ATRX) (Li et al. 2018a), branched-chain amino acid transaminase 1  (BCAT1) (Cho et al. 2017), platelet-derived growth factor receptor alpha (PDGFRA) (Hu et al. 2017), phosphatase and tensin homolog deleted on chromosome 10 (PTEN) (Zinn et al. 2017), retinoblastoma 1 (RB1) (Hu et al. 2017), and CD3 RNA expression (Narang et al. 2017).