Developmental and behavioral phenotypes in a new mouse model of DDX3X syndrome

Abstract

BackgroundMutations in the X-linked gene DDX3X account for ~2% of intellectual disability in females, often co-morbid with behavioral problems, motor deficits, and brain malformations. DDX3X encodes an RNA helicase with emerging functions in corticogenesis and synaptogenesis. MethodsWe generated a Ddx3x haploinsufficient mouse (Ddx3x+/-) with construct validity for DDX3X loss-of-function mutations. We used standardized batteries to assess developmental milestones and adult behaviors, as well as magnetic resonance imaging and immunostaining of cortical projection neurons to capture early postnatal changes in brain development. ResultsDdx3x+/- mice show physical, sensory, and motor delays that evolve into behavioral anomalies in adulthood, including hyperactivity, anxiety-like behaviors, cognitive impairments, and motor deficits. Motor function further declines with age. These behavioral changes are associated with a reduction in brain volume, with some regions (e.g., cortex and amygdala) disproportionally affected. Cortical thinning is accompanied by defective cortical lamination, indicating that Ddx3x regulates the balance of glutamatergic neurons in the developing cortex. ConclusionsThese data shed new light on the developmental mechanisms driving DDX3X syndrome and support face validity of this novel pre-clinical mouse model.