An investigation on the alterations in Wnt signaling in ADHD across developmental stages
Natalie Monet Walter, Cristine Marie Yde Ohki, Michelle Rickli, Lukasz Smigielski, Susanne Walitza, Edna Grünblatt
Abstract
The canonical Wnt signaling pathway plays a vital role in the developmental processes of the Central Nervous System throughout both prenatal and postnatal stages, as well as in maintaining homeostasis during adulthood. Its complex intracellular cascade involves the participation of key proteins (i.e., GSK3β and β-catenin) to activate the transcription of Wnt target genes. These genes subsequently control processes like cell proliferation, maturation, and the determination of cell fate. Previous studies suggest that this pathway can also be associated with Attention-Deficit Hyperactivity Disorder (ADHD), a neurodevelopmental disorder with multifactorial etiology. This study aimed to clarify if and at what developmental stage the Wnt pathway is altered in ADHD. Accordingly, we carried out proteomic and functional assessments of the Wnt pathway using Western Blot and reporter assays, respectively. These assessments were performed at the induced pluripotent stem cell (iPSC), neural stem cell (NSC), and neuronal phases. IPSCs were generated from somatic cells retrieved from 5 controls and 5 patients diagnosed with ADHD. As opposed to the developmental stage of iPSCs, ADHD NSCs showed alterations in the protein expression of both GSK3β and β-catenin, suggesting increased Wnt activity in the ADHD group. Moreover, Wnt reporter assays confirmed higher Wnt activity in ADHD NSCs. Our molecular findings in NSCs correlated with genetic predisposition to ADHD and clinical traits displayed by their respective donors. In conclusion, these results suggest that a crucial cellular pathway is disrupted in patient-specific NSCs, potentially explaining the developmental deficits clinically exhibited by ADHD patients.