HNRNPU and microcephaly: We systematically explore both of these challenges by focusing on the neurodevelopmental disorder caused by variants in HNRNPU. De novo loss-of-function variants in HNRNPU have been found to cause a neurodevelopmental syndrome, with patients exhibiting developmental delay (∼95%), intellectual disability (52%), craniofacial dysmorphism (54–95%) including microcephaly (14–20%) and seizures (83–95%).5