Zoodsma, J.D., Keegan, E., Moody, G.R., Napoli, A.J., Burgess, H.A., Wollmuth, L.P., & Sirotkin, H.I. Disruption of grin2B, an ASD-associated gene, produces social deficits in zebrafish. July 7, 2022, Preprint (Version 1) available at Research Square, DOI: doi.org/10.21203/rs.3.rs-1766152/v1
Autism Spectrum Disorder (ASD), like many neurodevelopmental disorders, has complex and varied etiologies. Advances in genome sequencing have identified multiple candidate genes associated with ASD, including dozens of missense and nonsense mutations in the NMDAR subunit GluN2B, encoded by GRIN2B. NMDARs are glutamate-gated ion channels with key synaptic functions in excitatory neurotransmission. How alterations in these proteins impact neurodevelopment is poorly understood, in part because knockouts of GluN2B in rodents are lethal. Here, we demonstrate that zebrafish GluN2B displays similar structural and functional properties to human GluN2B. Using CRISPR-Cas9, we generated fish lacking all functional GluN2B (grin2B -/- ) and surprisingly found that they survive into adulthood. Given the prevalence of social deficits in ASD, we assayed social preference in the grin2B -/- fish. Wild-type fish develop a strong social preference by 3 weeks post fertilization (wpf). In contrast, grin2B -/- fish at this age exhibit significantly reduced social preference. This phenotype is specific for GluN2B and not due to general NMDAR dysfunction, as frameshift mutations in other NMDAR subunits do not generate social deficits. Notably, the lack of GluN2B does not result in a broad disruption of neurodevelopment, as grin2B -/- larvae do not show alterations in spontaneous or photic-evoked movements, are capable of prey capture, and exhibit learning capabilities. Whole-brain imaging of grin2B -/- larvae revealed a reduction in inhibitory neurons in the subpallium, a region linked to ASD in humans, but showed that overall brain size and E/I balance in grin2B -/- is comparable to wild-type. Together, these findings highlight the specific role of GluN2B in ASD etiologies and establishing a disease-relevant in vivo model for future studies.
NMDA receptors; GluN2B, Autism Spectrum Disorders; social behaviors