The selective down-regulation of RELN and GAD(67) in prefrontal cortex of patients with schizophrenia and bipolar disorder who have psychosis is consistent with the hypothesis that these parameters are vulnerability factors in psychosis; this plus the loss of the correlation between these 2 parameters that exists in nonpsychotic subjects support the hypothesis that these changes may be liability factors underlying psychosis.

Postmortem prefrontal cortices (PFC) (Brodmann's areas 10 and 46), temporal cortices (Brodmann's area 22), hippocampi, caudate nuclei, and cerebella of schizophrenia patients and their matched nonpsychiatric subjects were compared for reelin (RELN) mRNA and reelin (RELN) protein content. In all of the brain areas studied, RELN and its mRNA were significantly reduced (Ϸ50%) in patients with schizophrenia; this decrease was similar in patients affected by undifferentiated or paranoid schizophrenia. To exclude possible artifacts caused by postmortem mRNA degradation, we measured the mRNAs in the same PFC extracts from ␥-aminobutyric acid (GABA) A receptors ␣ 1 and ␣ 5 and nicotinic acetylcholine receptor ␣ 7 subunits. Whereas the expression of the ␣ 7 nicotinic acetylcholine receptor subunit was normal, that of the ␣ 1 and ␣ 5 receptor subunits of GABA A was increased when schizophrenia was present. RELN mRNA was preferentially expressed in GABAergic interneurons of PFC, temporal cortex, hippocampus, and glutamatergic granule cells of cerebellum. A protein putatively functioning as an intracellular target for the signaltransduction cascade triggered by RELN protein released into the extracellular matrix is termed mouse disabled-1 (DAB1) and is expressed at comparable levels in the neuroplasm of the PFC and hippocampal pyramidal neurons, cerebellar Purkinje neurons of schizophrenia patients, and nonpsychiatric subjects; these three types of neurons do not express RELN protein. In the same samples of temporal cortex, we found a decrease in RELN protein of Ϸ50% but no changes in DAB1 protein expression. We also observed a large (up to 70%) decrease of GAD67 but only a small decrease of GAD65 protein content. These findings are interpreted within a neurodevelopmental͞vulnerability ''twohit'' model for the etiology of schizophrenia.

During embryonic development of brain laminated structures, the protein Reelin, secreted into the extracellular matrix of the cortex and hippocampus by Cajal-Retzius (CR) cells located in the marginal zone, contributes to the regulation of migration and positioning of cortical and hippocampal neurons that do not synthesize Reelin. Soon after birth, the CR cells decrease, and they virtually disappear during the following 3 weeks. Despite their disappearance, we can quantify Reelin mRNA (approximately 200 amol͞g of total RNA) and visualize it by in situ hybridization, and we detect the translated product of this mRNA by immunocytochemistry preferentially in ␥-aminobutyric acid (GABA)ergic neurons of adult rat cortex and hippocampus. In adult rat cerebellum, Reelin is expressed in glutamatergic neurons (granule cells). The translated product of this mRNA is readily exported from the granule cell somata to the parallel fibers, where it has been detected by electron microscopy in axon terminals located presynaptically to Purkinje cell dendrites.

Aging and exposure to environmental toxins including MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) are strong risk factors for developing Parkinson's disease (PD), a common neurologic disorder characterized by selective degeneration of midbrain dopaminergic (DAergic) neurons and astrogliosis. Aging and PD impair the subventricular zone (SVZ), one of the most important brain regions for adult neurogenesis. Because inflammation and oxidative stress are the hallmarks of aging and PD, we investigated the nature, timing, and signaling mechanisms contributing to aging-induced SVZ stem/neuroprogenitor cell (NPC) inhibition in aging male mice and attempted to determine to what extent manipulation of these pathways produces a functional response in the outcome of MPTP-induced DAergic toxicity. We herein reveal an imbalance of Nrf2-driven antioxidant/anti-inflammatory genes, such as Heme oxygenase1 in the SVZ niche, starting by middle age, amplified upon neurotoxin treatment and associated with an exacerbated proinflammatory SVZ microenvironment converging to dysregulate the Wingless-type MMTV integration site (Wnt)/␤-catenin signaling, a key regulatory pathway for adult NPCs. In vitro experiments using coculture paradigms uncovered aged microglial proinflammatory mediators as critical inhibitors of NPC proliferative potential. We also found that interruption of PI3K (phosphatidylinositol3-kinase)/Akt and the Wnt/Fzd/␤-catenin signaling cascades, which switch glycogen synthase kinase 3␤ (GSK-3␤) activation on and off, were causally related to the impairment of SVZ-NPCs. Moreover, a synergy between dysfunctional microglia of aging mice and MPTP exposure further inhibited astrocyte proneurogenic properties, including the expression of key Wnts components. Last, pharmacological activation/antagonism studies in vivo and in vitro suggest the potential that aged SVZ manipulation is associated with DAergic functional recovery.

Histological and behavioral traits are associated with reelin (Reln) haplo-insufficiency in heterozygous reeler mouse (rl+/-). These phenotypic traits are an approximately 50% decrease of brain Reln mRNA and Reln protein, an accumulation of nicotinamide-adenine dinucleotide phosphate-diaphorase (NADPH-d)-positive neurons in subcortical white matter, an age-dependent decrease in prepulse inhibition of startle (PPI), and neophobic behavior on the elevated plus-maze. Possible analogies between these rl+/- phenotypic traits and signs of psychosis vulnerability are discussed.

The A2AR is largely coexpressed with D2Rs and enkephalin mRNA in the striatum where it modulates dopaminergic activity. Activation of the A 2AR antagonizes D2R-mediated behavioral and neurochemical effects in the basal ganglia through a mechanism that may involve direct A 2AR-D2R interaction. However, whether the D2R is required for the A2AR to exert its neural function is an open question. In this study, we examined the role of D 2Rs in A2AR-induced behavioral and cellular responses, by using genetic knockout ( However, the direct receptor-receptor antagonistic model does not adequately explain recent findings that activation of the A 2A R exerts a tonic excitatory effect on c-fos expression in dopaminedepleted animals and on D 2 R antagonist-(haloperidol)-induced phosphorylation of dopamine-and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) in striatum (19). For example, the A 2A R agonist CGS21680 induced c-fos expression in the 6-hydroxyThis paper was submitted directly (Track II) to the PNAS office.Abbreviations: A2AR, A2A adenosine receptor; CGS21680, 2-4-(2-carboxyethyl)phenethylamino-5Ј-N-ethylcarboxamidoadenosine; CSC, 8-(3-chlorostyryl)caffeine; D2R, D2 dopamine receptor; DARPP-32, dopamine-and cAMP-regulated phosphoprotein of 32 kDa; DPCPX, 8-cyclopentyl-1,3-dipropylxanthyne; KO, knockout; PD, Parkinson's disease; WT, wild type; GABA, ␥-aminobutyric acid. † To whom reprint requests should be addressed.

We have recently isolated stem cells deriving from the olfactory bulbs of adult patients undergoing particularly invasive neurosurgery. After improving our experimental conditions, we have now obtained neural stem cells according to clonal analysis. The cells can be expanded, established in continuous cell lines and differentiated into the three classical neuronal phenotypes (neurons, astrocytes, and oligodendrocytes). Also, after exposition to leukemia inhibitory factor, we are able to improve the number of neurons, an ideal biological source for transplantation in various neurodegenerative disorders. Stem

Reelin regulates telencephalic and cerebellar lamination during mammalian development and is expressed in several structures of the adult brain; however, only traces of reelin were believed to be in peripheral tissues. Because reelin structurally resembles extracellular matrix proteins, and because many of these proteins are expressed in blood, we hypothesized that reelin also might be detectable in the circulation. Reelin (420 kDa) and two reelin-like immunoreactive bands (310 and 160 kDa) are expressed in serum and platelet-poor plasma of rats, mice, and humans, but these three bands were not detectable in serum of homozygous reeler (rl͞rl) mice. Reelin plasma levels in heterozygous (rl͞؉) mice were half of those in wild-type littermates. Western blotting and immunocytochemistry using antireelin mAbs indicated that reelinlike immunoreactivity was expressed in a subset of chromaffin cells within the rat adrenal medulla and in a subset of cells coexpressing ␣-melanocyte-stimulating hormone within the pituitary pars intermedia. However, surgical removal of adrenal or pituitary failed to decrease the amount of reelin (420-kDa band) expressed in serum. Adult liver expressed one-third of the reelin mRNA concentration expressed in adult mouse cerebral cortex. Full-length reelin protein was detectable in liver extracts in situ; acutely isolated liver cells also secreted full-length reelin in vitro. Liver appears to be a prime candidate to produce and maintain the circulating reelin pool. It now becomes relevant to ask whether circulating reelin has a physiologic role on one or more peripheral target tissues.disabled-1 ͉ reeler ͉ serum