1To identify novel candidate intellectual disability genes, we performed a meta-analysis on 2,637 de novo 2 mutations, identified from the exomes of 2,104 ID trios. Statistical analyses identified 10 novel candidate 3 ID genes, including DLG4, PPM1D, RAC1, SMAD6, SON, SOX5, SYNCRIP, TCF20, TLK2 and TRIP12. In 4 addition, we show that these genes are intolerant to non-synonymous variation, and that mutations in 5 these genes are associated with specific clinical ID phenotypes. 6