Table 3.

Summary of evidence for potential ASD-specific methylation biomarkers.

Gene	Genetic evidence	Methylation reference	Diagnostic method	Tissue	Samplesa	Largest effect sizeb	Expression	Protein	Other data
OXTR	Weak	(95)	DSM-IV, ADI-R	PBLs	20/20	+23%	No	No	Endophenotyped
					10/10c	+38.9%
				Temporal cortex	10/10c	+41.6%c	yes	No
GAD1	Weak	(113)	Not given	Cerebellum	10/10	+3%e	Yesf	No	Animal models, MECP2 binding
EN2	Minimal	(120)	DSM-IV	Cerebral cortex	13/13	+10–20%g	Yes	Yes
RELN	Strong	(113)	Not given	Cerebellum	10/10	Not quantifiable	Yes	Yes	MECP2 binding
MECP2	Syndromic	(127, 128)	ADI-R, ADOS	Frontal cortex	14/14	+12%, +10%h	Yes	Yes	Animal model

For abbreviations and references see the main text.

^aCases/controls.

^b% methylation difference, cases minus controls.

^cMales only.

^dMethylation correlated to endophenotype.

^eHydoxymethylation only.

^fIn Purkinje neurons and cerebellum.

^gMethylation and hydroxymethylation.

^hTwo separate sets of MECP2 CpG sites regions measured.