In this study, we compared the expression profile of SHEDs from idiopathic autistic patients with those of nonaffected controls. We showed that the group of DEGs is enriched by genes expressed in brain, ASD candidate genes, genes that harbor mutations identified by exome studies and DEGs found in ASD brain. We also found a great overlap with the ontological categories found in previous expression studies on ASD lymphocytes/ LCL [Abrahams & Geschwind, 2008], such as GTPase regulator activity, protochaderin genes and alternative splicing. Moreover, functional annotation analysis in the present data set revealed enrichment of a considerable number of other biological functions and signaling pathways that were already related to ASD, namely: pathways involved in cytoskeleton dynamics, such as axonal guidance signaling and regulation of actin-based motility by Rho [Anitha et al., 2008; Hu et al., 2009a; Melin et al., 2006; Sbacchi et al., 2010]; the protein synthesis-related pathways mTOR and PTEN signaling [Cuscó et al., 2009; Gkogkas et al., 2013; Kelleher & Bear, 2008; Neves-Pereira et al., 2009]; RNA editing and alternatively spliced genes [Abrahams & Geschwind, 2008; Smith & Sadee, 2011; Talebizadeh et al., 2006; Voineagu et al., 2011]; and cell adhesion molecules [Betancur, Sakurai, & Buxbaum, 2009; Morrow et al., 2008; Wang et al., 2009]. Therefore, SHEDs' transcriptome revealed deregulation of several candidate genes, pathways and biological systems previously pointed out as associated with ASD, suggesting that these cells are a good alternative to study ASD. Although our second set of controls were composed by males and females, which can be considered a limitation of this study, specially considering the sexual bias in ASD, the results found in DS2 analysis were consistent to those found in DS1.
A consistent result in our analysis was the differentially expression of AR-regulated genes, which was found in all data sets tested. It is also of note that a significant number of such DEGs had been previously suggested to be ASD candidate genes. Alteration in AR signaling supports the “extreme male brain” theory for ASD [Baron-Cohen, Knickmeyer, & Belmonte, 2005] and could explain the sexual bias seen in these disorders. Moreover, alteration in androgen metabolism and signaling in ASD patients have been suggested by other global expression studies [Hu et al., 2009a,b; Sarachana, Zhou, Chen, Manji, & Hu, 2010]. However, none of these studies presented any deregulated upstream molecule possibly interacting with this pathway. Analysis of DS1 suggests that CHD8, which is known to interact with AR to mediate its transcriptional regulation activity, is a possible upstream regulator of such pathway. Involvement of CHD8 in ASD pathology is becoming evident with the recent findings of exome studies [Neale et al., 2012; O'Roak et al., 2012a,b; Sanders et al., 2012; Talkowski et al., 2012]. We believe that investigation of CHD8 and AR interaction should be further explored to uncover the functional implications of CHD8 mutations in ASD etiology.
In summary, our results suggest that despite our lack of knowledge about the mutational mechanism in the studied ASD patients, their altered genomes lead to expression deregulation in shared pathways that could be detected even with a small sample size. Our work also showed that SHEDs are an alternative cell type to explore deregulation of biological systems in ASD patients. We do not expect that SHEDs will substitute the use of neuronal-derived stem cells, such as from induced pluripotent stem cells, for functional analysis. However, as SHEDs are obtained noninvasively and require less manipulation, they represent a good option to identify new pathways and gene interactions in ASD,