IL1RAPL1 have recently been found in affected individuals with single non-recurrent truncating variants in FAM47B, SATL1 and SAGE1, respectively (Table 3). Taken together, the results from 6 of the 19 genes with a single nonrecurrent truncating variant remain compatible with involvement in the causation of mental retardation (SYP, ZNF711, ARSF, ZNF183, VSIG4, and USP9X), whereas 13 others have one or more inconsistencies. To evaluate these six genes further, we sequenced their complete coding sequences in a further 914 male index subjects from XLMR-affected families and 1,129 male controls (Supplementary Table 2 online).
