B2M and autism: For normalization of gene expression, the following reference genes were selected for the various brain regions: 1) ACG: RPL13A, GAPDH and ACTB; 2) MC: B2M, RPL13A, GAPDH and ACTB; 3) THL: B2M, HPRT1 and GAPDH. The chosen reference genes for each brain region did not show any significant difference in expression between the control and autism groups.