The name is absent

Autism prodrome 46 of 89

cases compared to controls. The genes encoding neuronal cell-adhesion molecules are
NRXN1 (Kim et al., 2008), CNTN4 (Roohi et al., 2009), NLGN1 and ASTN2 and the
genes involved in the ubiquitin pathways including UBE3A, PARK2, RFWD2 and
FBXO40.

In addition to CNVs that normally affect multiple genes, a small number of
cases with ASD are associated withmutations in a single gene. The direct sequencing
approach has identified several coding mutations associated with autism including
genes encoding neuroligins and their associated proteins that are important in synaptic
function (Durand et al., 2007; Jamain et al., 2003; Laumonnier et al., 2004; Szatmari
et al., 2007). There are different type of mutations, including frame shift mutations,
missense mutations, small deletions and translocations disrupting the following genes:
Neuroligin 4 (NLGN4) (Jamain et al., 2003; Laumonnier et al., 2004; Yan et al.,
2005), NLGN3, NLGN4Y (Jamain et al., 2003; Yan et al., 2005), Neurexin 1 (NRXN1)
(Kim et al., 2008; Szatmari et al., 2007; Yan et al., 2008), SHANK3 (Durand et al.,
2007; Moessner et al., 2007), PTEN (Butler et al., 2005; Buxbaum et al., 2007;
Goffin, Hoefsloot, Bosgoed, Swillen, & Fryns, 2001; Herman et al., 2007; Orrico et
al., 2009) and CNTNAP2 (Arking et al., 2008; Bakkaloglu et al., 2008). Single gene
mutations are also the cause of several syndromes in which ASD is observed at higher
than expected frequencies, including Rett syndrome caused by mutations in the
MECP2 gene and fragile X syndrome caused by mutation in the FMR1 gene.

There is also some evidence for contribution of epigenetic modifications (with
no change in DNA sequence) to ASD (Hogart, Nagarajan, Patzel, Yasui, & Lasalle,
2007; Jiang et al., 2004), however the manner and extent of epigenetic involvement
remains to be defined. Epigenetic modifications including cytosine methylation and
post-translational modification of histones provide a mechanism for modulation of

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