SUMMARY Genes disrupted in schizophrenia may be revealed by de novo mutations in affected persons from otherwise healthy families. Furthermore, during normal brain development, genes are expressed in patterns specific to developmental stage and neuroanatomical structure. We identified de novo mutations in persons with schizophrenia, then mapped the responsible genes onto transcriptome profiles of normal human brain tissues from age 13 weeks gestation to adulthood. In the dorsolateral and ventrolateral prefrontal cortex during fetal development, genes harboring damaging de novo mutations in schizophrenia formed a network significantly enriched for transcriptional co-expression and protein interaction. The 50 genes in the network function in neuronal migration, synaptic transmission, signaling, transcriptional regulation, and transport. These results suggest that disruptions of fetal prefrontal cortical neurogenesis are critical to the pathophysiology of schizophrenia. These results also support the feasibility of integrating genomic and transcriptome analyses to map critical neurodevelopmental processes in time and space in the brain.

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Massively parallel sequencing of targeted regions, exomes, and complete genomes has begun to dramatically increase the pace of discovery of genes responsible for human disorders. Here we describe how exome sequencing in conjunction with homozygosity mapping led to rapid identification of the causative allele for nonsyndromic hearing loss DFNB82 in a consanguineous Palestinian family. After filtering out worldwide and population-specific polymorphisms from the whole exome sequence, only a single deleterious mutation remained in the homozygous region linked to DFNB82. The nonsense mutation leads to an early truncation of the G protein signaling modulator GPSM2, a protein that is essential for maintenance of cell polarity and spindle orientation. In the mouse inner ear, GPSM2 is localized to apical surfaces of hair cells and supporting cells and is most highly expressed during embryonic development. Identification of GPSM2 as essential to the development of normal hearing suggests dysregulation of cell polarity as a mechanism underlying hearing loss.

Normal vision in Drosophila requires NINAC, a class III myosin. Class III myosins are hybrid motor-signaling molecules, with an Nterminal kinase domain, highly conserved head and neck domains, and a class III-specific tail domain. In Drosophila rhabdomeres, NINAC interacts with actin filaments and with a PDZ scaffolding protein to organize the phototransduction machinery into a signaling complex. Recessive null mutations in Drosophila NINAC delay termination of the photoreceptor response and lead to progressive retinal degeneration. Here, we show that normal hearing in humans requires myosin IIIA, the human homolog of NINAC. In an extended Israeli family, nonsyndromic progressive hearing loss is caused by three different recessive, loss-of-function mutations in myosin IIIA. Of 18 affected relatives in Family N, 7 are homozygous and 11 are compound heterozygous for pairs of mutant alleles. Expression of mammalian myosin IIIA is highly restricted, with the strongest expression in retina and cochlea. The involvement of homologous class III myosins in both Drosophila vision and human hearing is an evolutionary link between these sensory systems.