MARK2 variants cause autism spectrum disorder via the downregulation of WNT/β-catenin signaling pathway

MARK2, a member of the evolutionarily conserved PAR1/MARK serine/threonine kinase family, has been identified as a novel risk gene for autism spectrum disorder (ASD) based on the enrichment of de novo loss-of-function (Lof) variants in large-scale sequencing studies of ASD individuals. However, the features shared by affected individuals and the molecular mechanism of MARK2 variants during early neural development remained unclear. Here, we report 31 individuals carrying heterozygous MARK2 variants and presenting with ASD, other neurodevelopmental disorders, and typical facial dysmorphisms. Lof variants predominate (81%) in affected individuals, while computational analysis and in vitro transfection assay also point to MARK2 loss resulting from missense variants. Using patient-derived and CRISPR-engineered isogenic induced pluripotent stem cells (iPSCs), and Mark2+/- (HET) mice, we show that MARK2 loss leads to systemic neurodevelopmental deficits, including anomalous polarity in neural rosettes, imbalanced proliferation and differentiation in neural progenitor cells (NPCs), abnormal cortical development and ASD-like behaviors in mice. Further using RNA-Seq and lithium treatment, we link MARK2 loss to the downregulated WNT/β-catenin signaling pathway and identify lithium as a potential drug for treating MARK2-related ASD.