Supplementary Material for: Differential Expression of <b><i>SLC9A9</i></b> and Interacting Molecules in the Hippocampus of Rat Models for Attention Deficit/Hyperactivity Disorder

<i>SLC9A9</i> [solute carrier family 9, member 9, also known as Na<sup>+</sup>/H<sup>+</sup> exchanger member 9 (NHE9)], has been implicated in human attention deficit/hyperactivity disorder (ADHD), autism, and rat studies of hyperactivity and inattentiveness. <i>SLC9A9</i> is a membrane protein that regulates the luminal pH of the recycling endosome. We recently reported the interactions of <i>SLC9A9</i> with two molecules: calcineurin homologous protein <i>(CHP)</i> and receptor for activated C-kinase 1 <i>(RACK1)</i>. We also reported two novel <i>SLC9A9</i> mutations and abnormal gene expression profiles in the brains of an inattentive type rat model of ADHD (WKY/NCrl rat). In this study, we further examined the expression and relationship of <i>SLC9A9</i> and 9 additional genes <i>(CHP, RACK1, CaM, PPP3R1, PPP1R10, PKCm, CaMKI, NR2B, PLCb1)</i> that may directly or indirectly interact with <i>SLC9A9</i> in the hippocampus of the WKY/NCrl rat and the spontaneously hypertensive rat (SHR) model of the combined type of ADHD. We found that the expression levels of these genes were significantly correlated, suggesting that they may be coregulated. Principal component analysis identified two main factors that accounted for 94% of the expression variance of the 10 genes. Significant differences were found for both factors across the 3 different rat strains. The two ADHD rat models (WKY/NCrl and SHR), although different from each other in adulthood, showed similar profiles in adolescence. Both models were significantly different from WKY/NHsd control rats at both ages. The expression abnormalities of each gene were evaluated and their roles in cell signaling processes such as calcium signaling and protein phosphorylation are discussed. Our results suggest that abnormalities in <i>SLC9A9</i>-mediated signaling pathways could contribute to the ADHD phenotype of two rat models (WKY/NCrl and SHR/NCrl), and that the perturbation of the <i>SLC9A9</i> network is age-dependent.