Microdeletions in the 1q44 locus encompassing HNRNPU and other genes, as well as point mutations in HNRNPU, result in brain disorders, including early-onset seizures, severe intellectual disability, and lower penetrance microcephaly, a thin corpus callosum, dysmorphic facial features, and hypotonia15–21 (reviewed by ref. 22). The gene discussed is HNRNPU; the disease is brain disorder.