TABLE I. Molecular mechanisms and genes implicated in autism map onto a limited number of steps in neurodevelopment. *We refer readers to https://gene.sfari.org/autdb/Welcome.do for references regarding each gene mutation.

Molecular mechanisms implicated by mutation	Gene/mutation*	Neurodevelopmental step (from Figure 1)
Regulation of gene expression	Multiple highly recurrent, large CNVs, MeCP2, MBD5, CHD3, CHD7, CHD8, EHMT1, FOXP2	Neuronal morphogenesis; Axon and dendrite growth and branching. Experience-dependent synapse modification; Synaptic plasticity
Pre-mRNA splicing	A2BP1/FOX1	Many
Protein localization, translation, turnover	FMR1, CYFIP1, NHE6I9, UBE3A	Neuronal morphogenesis; Axon and dendrite growth and branching; Experience-dependent synapse modification; Synaptic plasticity
Synaptic transmission	CACNA1C, CACNA1H, RIMS3, SYN1, GRIK2	Experience-dependent synapse modification; Synaptic plasticity
Cell signaling	TSC1/2, PTEN, MAPK3, MET, PTCHD1, RELN	Neuronal morphogenesis; Axon and dendrite growth and branching. Experience-dependent synapse modification; Synaptic plasticity
Synaptic scaffolding and cytoskeletal proteins	AHI1, SHANK2/3	Experience-dependent synapse modification. Synaptic plasticity
Neuronal cell adhesion	CNTNAP2, NLGN3, NLGN4X, IL1RAPL1, NRXN1, CNTN4	Neuronal morphogenesis, Axon and dendrite growth and branching; Experience-dependent synapse modification; Synaptic plasticity