Pharmacological and anatomical evidence suggests that abnormal glutamate neurotransmission may be associated with the pathophysiology of schizophrenia and mood disorders. Medial temporal lobe structural alterations have been implicated in schizophrenia and to a lesser extent in mood disorders. To comprehensively examine the ionotropic glutamate receptors in these illnesses, we used in situ hybridization to determine transcript expression of N-methyl-D-aspartate (NMDA), a-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA), and kainate receptor subunits in the medial temporal lobe of subjects with schizophrenia, bipolar disorder (BD), or major depression (MDD). We used receptor autoradiography to assess changes in glutamate receptor binding in the same subjects. Our results indicate that there are region-and disorder-specific abnormalities in the expression of ionotropic glutamate receptor subunits in schizophrenia and mood disorders. We did not find any changes in transcript expression in the hippocampus. In the entorhinal cortex, most changes in glutamate receptor expression were associated with BD, with decreased GluR2, GluR3, and GluR6 mRNA expression. In the perirhinal cortex we detected decreased expression of GluR5 in all three diagnoses, of GluR1, GluR3, NR2B in both BD and MDD, and decreased NR1 and NR2A in BD and MDD, respectively. Receptor binding showed NMDA receptor subsites particularly affected in the hippocampus, where MK801 binding was reduced in schizophrenia and BD, and MDL105,519 and CGP39653 binding were increased in BD and MDD, respectively. In the hippocampus AMPA and kainate binding were not changed. We found no changes in the entorhinal and perirhinal cortices. These data suggest that glutamate receptor expression is altered in the medial temporal lobe in schizophrenia and the mood disorders. We propose that disturbances in glutamate-mediated synaptic transmission in the medial temporal lobe are important factors in the pathophysiology of these severe psychiatric illnesses.

Control of growth determines the size and shape of organs. Localized signals known as 'organizers' and members of the Pax family of proto-oncogenes are both elements in this control. Pax proteins have a conserved DNA-binding paired domain, which is presumed to be essential for their oncogenic activity. We present evidence that the organizing signal Notch does not promote growth in eyes of D. melanogaster through either Eyeless (Ey) or Twin of eyeless (Toy), the two Pax6 transcription factors. Instead, it acts through Eyegone (Eyg), which has a truncated paired domain, consisting of only the C-terminal subregion. In humans and mice, the sole PAX6 gene produces the isoform PAX6(5a) by alternative splicing; like Eyegone, this isoform binds DNA though the C terminus of the paired domain. Overexpression of human PAX6(5a) induces strong overgrowth in vivo, whereas the canonical PAX6 variant hardly effects growth. These results show that growth and eye specification are subject to independent control and explain hyperplasia in a new way.

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