Genetic variants of the adenylyl cyclase encoding gene ADCY2 in neurodevelopmental disorders

• Applicant: Professorin Dr. Meliha Karsak
• Subject Area: Human Genetics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 538522774

Neurodevelopmental disorders (NDD) constitute a heterogeneous group of early-onset diseases, the cause of which can currently be found in just around 40% of cases. We have now identified de novo alterations in the adenylyl cyclase 2 (AC2) coding gene ADCY2 in three unrelated NDD patients with unknown cause and we would thus like to investigate in this project whether ADCY2 is a novel monogenic NDD disease gene. AC2 is involved in the biosynthesis of cyclic adenosine 3'-5' monophosphate (cAMP) and it mediates G-protein coupled receptor (GPCR) signaling via G-protein activation. Control of intracellular cAMP concentration is a critical factor in signal transduction and, if dysfunctional, can result in an inappropriate response of the cell to external factors. AC2 is particularly expressed in the nervous system, making it plausible that a dysfunction of the protein leads to neuronal disease. In our preliminary work, we have examined the three de novo variants and found gain-of-function effects after direct activation in vitro. In this project, we will analyze additional variants identified via GeneMatcher. In addition to direct activation, we will test the physiologically more relevant indirect AC2 activation by a GPCR ligand, measuring cAMP production in the cell via a biosensor. In addition, we will investigate an ADCY2 variant associated with psychiatric disorders. Since the regulation of AC2 activity is possible via small-molecules, the enzyme represents a therapeutically interesting target. Therefore, we will use known adenylyl cyclase inhibitors to reduce the high basal cAMP levels in the cell. In addition, we will select 1000 substances from a molecule library of about 12.500 molecules by virtual screening and search experimentally for new AC2 inhibitors or activators. To determine the molecular effects of de novo mutations on human neurodevelopment in an in vitro model, we will use human neural organoids with an appropriately edited ADCY2 gene. In these cells we will 1. verify the gain-of-function effect seen after transient transfection, 2. investigate effects of known and new inhibitors, 3. characterize morphological structures and maturation stages of the organoids, 4. determine the transcriptomes of individual cell populations by single cell RNA sequencing in organoids of different developmental time points and analyze quantitative differences in cell type compositions. Our hypothesis is that ADCY2 NDD variants are the cause of disease and lead to alterations in neuronal development and function that are caused by altered cAMP levels. Thus, our investigation with inhibitors represent a novel therapeutic and translational approach.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Christian Kubisch