RAPGEF4 and autism: Several candidate autism susceptibility genes [15] were hypermethylated (P <0.05) in the HMFA, including Shank3, Cacana1g, Gtf2i, Rapgef4, and Nbea in male offspring and Ext1, Ube3a, Erbb4, Grip1, Grm8, Reeln, Shank3, and Rbfox1 in female offspring (Additional file 2: Table S2 and Additional file 3: Table S3).