PRRG4 Brain-Specific Conditional Knockout Mice Display Autism Spectrum Disorder-Like Behaviors.

Background: Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized primarily by social deficits and repetitive behaviors. The mechanisms of ASD are complex and are not yet fully understood, although many ASD risk genes and mouse models have been reported. It has been suggested that deletion of PRRG4 (proline-rich and Gla domain 4) deletion may contribute to autism symptoms in patients with WAGR (Wilms' tumor, aniridia, gonadoblastoma, mental retardation) syndrome. The mouse model with PRRG4 gene deletion has not been reported so far. This study investigated whether brain-specific conditional knockout of PRRG4 induces ASD-like symptoms in mice by crossing the PRRG4fl/fl mice with Emx1-Cre mice, which express Cre in the cerebral cortex and hippocampus.

Results: The PRRG4 brain-specific knockout (PRRG4fl/fl-Cre+, PRRG4-CKO) mice exhibited social deficits, repetitive behaviors, and anxiety-like symptoms compared to PRRG4fl/fl control mice according to the results of various behavioral tests. PRRG4 knockout led to the increase in total dendritic length, branching, and dendritic spine density in the pyramidal neurons of the cerebral cortex and hippocampus, as well as enhanced levels of synaptic proteins including SYP and PSD95. Immunoprecipitation experiment with PRRG4 antibodies showed dramatic decreased interaction of PRRG4 and MAGI2 proteins in brain tissues from PRRG4-CKO mice compared to PRRG4fl/fl control mice. GST-RBD pull-down assay showed a significant decrease in RhoA-GTP levels in the cerebral cortex and hippocampus of PRRG4-CKO mice.

Conclusions: Brain-specific conditional knockout of the PRRG4 in mice leads to ASD-like symptoms. PRRG4 protein may regulate dendritic and synaptic development in mice by activating RhoA through interaction with MAGI2. These findings provide evidence for a comprehensive understanding of PRRG4 function in vivo and support the association between PRRG4 loss and ASD phenotypes observed in WAGR syndrome.