Neurodevelopmental changes may underlie the brain dysfunction seen in schizophrenia. While advances have been made in our understanding of the genetics of schizophrenia, little is known about how non-genetic factors interact with genes for schizophrenia. The present analysis of genes potentially associated with schizophrenia is based on the observation that hypoxia prevails in the embryonic and fetal brain, and that interactions between neuronal genes, molecular regulators of hypoxia, such as hypoxia-inducible factor 1 (HIF-1), and intrinsic hypoxia occur in the developing brain and may create the conditions for complex changes in neurodevelopment. Consequently, we searched the literature for currently hypothesized candidate genes for susceptibility to schizophrenia that may be subject to ischemia-hypoxia regulation and/or associated with vascular expression. Genes were considered when at least two independent reports of a significant association with schizophrenia had appeared in the literature. The analysis showed that more than 50% of these genes, particularly AKT1, BDNF, CAPON, CCKAR, CHRNA7, CNR1, COMT, DNTBP1, GAD1, GRM3, IL10, MLC1, NOTCH4, NRG1, NR4A2/NURR1, PRODH, RELN, RGS4, RTN4/NOGO and TNF, are subject to regulation by hypoxia and/or are expressed in the vasculature. Future studies of genes proposed as candidates for susceptibility to schizophrenia should include their possible regulation by physiological or pathological hypoxia during development as well as their potential role in cerebral vascular function.

Several malformation syndromes with abnormal cortical development have been recognized. Specific causative gene defects and characteristic electroclinical patterns have been identified for some. X-linked periventricular nodular heterotopia is mainly seen in female patients and is often associated with focal epilepsy. FLN1 mutations have been reported in all familial cases and in about 25% of sporadic patients. A rare recessive form of periventricular nodular heterotopia owing to ARGEF2 gene mutations has also been reported in children with microcephaly, severe delay, and early-onset seizures. Lissencephaly-pachygyria and subcortical band heterotopia represent a malformative spectrum resulting from mutations of either the LIS1 or the DCX (XLIS) gene. LIS1 mutations cause a more severe malformation posteriorly. Most children have severe developmental delay and infantile spasms, but milder phenotypes are on record, including posterior subcortical band heterotopia owing to mosaic mutations of LIS1. DCX mutations usually cause anteriorly predominant lissencephaly in male patients and subcortical band heterotopia in female patients. Mutations of the coding region of DCX were found in all reported pedigrees and in about 50% of sporadic female patients with subcortical band heterotopia. Mutations of XLIS have also been found in male patients with anterior subcortical band heterotopia and in female patients with normal brain magnetic resonance imaging. The thickness of the band and the severity of pachygyria correlate with the likelihood of developing severe epilepsy. Autosomal recessive lissencephaly with cerebellar hypoplasia, accompanied by severe delay, hypotonia, and seizures, has been associated with mutations of the reelin (RELN) gene. X-linked lissencephaly with corpus callosum agenesis and ambiguous genitalia in genotypic males is associated with mutations of the ARX gene. Affected boys have severe delay and infantile spasms with suppression-burst electroencephalograms. Early death is frequent. Carrier female patients can have isolated corpus callosum agenesis. Schizencephaly has a wide anatomoclinical spectrum, including focal epilepsy in most patients. Familial occurrence is rare. Initial reports of heterozygous mutations in the EMX2 gene have not been confirmed. Among several syndromes featuring polymicrogyria, bilateral perisylvian polymicrogyria shows genetic heterogeneity, including linkage to chromosome Xq28 in some pedigrees, autosomal dominant or recessive inheritance in others, and an association with chromosome 22q11.2 deletion in some patients. About 65% of patients have severe epilepsy. Recessive bilateral frontoparietal polymicrogyria has been associated with mutations of the GPR56 gene.

The rapidly emerging science of epigenetics and epigenomic medicine promises to reveal novel insights into the susceptibility to and the onset and progression of epileptic disorders. Epigenetic regulatory mechanisms are now implicated in orchestrating aspects of neural development (e.g., cell fate specification and maturation), homeostasis and stress responses (e.g., immediate early gene transcription), and neural network function (e.g., excitation-inhibition coupling and activity-dependent plasticity). These same neurobiological processes are responsible for determining the heterogeneous features of complex epileptic disease states. Thus, we highlight recent evidence that is beginning to elucidate the specific roles played by epigenetic mechanisms, including DNA methylation, histone code modifications and chromatin remodeling, noncoding RNAs and RNA editing, in human epilepsy syndromes and in the process of epileptogenesis. The highly integrated layers of the epigenome are responsible for the cell type specific and exquisitely environmentally responsive deployment of genes and functional gene networks that underlie the molecular pathophysiology of epilepsy and its associated comorbidities, including but not limited to neurotransmitter receptors (e.g., GluR2, GLRA2, and GLRA3), growth factors (e.g., BDNF), extracellular matrix proteins (e.g., RELN), and diverse transcriptional regulators (e.g., CREB, c-fos, and c-jun). These important observations suggest that future epigenetic studies are necessary to better understand, classify, prevent, and treat epileptic disorders.

Analysis of the molecular basis of neuronal migration in the mammalian CNS relies critically on the discovery and identification of genetic mutations that affect this process. Here, we report the detailed cerebellar phenotype caused by a new autosomal recessive neurological mouse mutation, scrambler (gene symbol scm). The scrambler mutation results in ataxic mice that exhibit several neuroanatomic defects reminiscent of reeler. The most obvious of these lies in the cerebellum, which is small and lacks foliation. Granule cells, although normally placed in an internal granule cell layer, are greatly reduced in number ( approximately 20% of normal). Purkinje cells are also reduced in number, and the majority are located ectopically in deep cerebellar masses. There is a small population of Purkinje cells ( approximately 5% of the total) that occupy a Purkinje cell layer between the molecular and granule cell layers. Despite this apparent disorganization of Purkinje cells, zebrin-positive and zebrin-negative parasagittal zones can be delineated. The ectopic masses of Purkinje cells are bordered by the extracellular matrix protein tenascin and by processes containing glial fibrillary acidic protein. Antibodies specific for these proteins also identify a novel midline raphe structure in both scrambler and reeler cerebellum that is not present in wild-type mice. Thus, in many respects, the scrambler cerebellum is identical to that of reeler. However, the scrambler locus has been mapped to a site distinct from that of reelin (Reln), the gene responsible for the reeler defect. Here we find that there are normal levels of Reln mRNA in scrambler brain and that reelin protein is secreted normally by scrambler cerebellar cells. These findings imply that the scrambler gene product may function in a molecular pathway critical for neuronal migration that is tightly linked to, but downstream of, reelin.

Cajal-Retzius (CR) cells of the developing neocortex secrete Reelin (Reln), a glycoprotein involved in neuronal migration. CR cells selectively express p73, a p53 family member implicated in cell survival and apoptosis. Immunocytochemistry in prenatal human telencephalon reveals a complex sequence of migration waves of p73- and Reln-immunoreactive (IR) neurons into the cortical marginal zone (MZ). At early preplate stages, p73/Reln-IR cells arise in distinct sectors of the telencephalon, including cortical primordium and ganglionic eminences. After the appearance of the cortical plate, further p73/Reln-IR cells originate in the medial periolfactory forebrain. In addition, p73 marks a novel cell population that appears at the choroid-cortical junction or cortical hem before the emergence of the dorsal hippocampus. A pronounced mediolateral gradient in the density of p73/Reln-IR neurons in the neocortical MZ at 8 gestational weeks suggests that a subset of CR cells migrate tangentially from cortical hem and taenia tecta into neocortical territory. This hypothesis is supported by the absence of p73-transcripts in prospective neocortex of p73-/-mice at embryonic day 12 (E12), whereas they are present in cortical hem and taenia tecta. In the p73-/- preplate, Reln is faintly expressed in a calretinin-positive cell population, not present in this form in the E12 wild-type cortex. At P2, Reln-IR CR cells are undetectable in the p73-/- cortex, whereas Reln-expression in interneurons is unchanged. Our results point to a close association between p73 and Reln in CR cells of the developing neocortex, with a partial dissociation in early preplate and basal telencephalon, and to a p73-mediated role of the cortical hem in neocortical development.

Epigenetic genome modifications such as DNA methylation appear to be involved in various diseases. Here, we suggest that the levels of DNA methylation at the BssHII methylation-sensitive restriction enzyme sites in the human REELIN (RELN) gene in the forebrain vary among individuals. Interestingly, although a statistically significant correlation between the levels of DNA methylation in RELN and age was detected in healthy individuals, no such correlations were seen in either schizophrenic or bipolar patients. In addition, reverse correlations between DNA methylation levels and RELN expression were also detected in postmortem brain RNA and on in vitro assay. These data suggest the possibility that epigenetic aberration from the normal DNA methylation status of RELN may confer susceptibility to psychiatric disorders.

A polymorphic trinucleotide repeat (CGG/GCC) within the human Reelin gene (RELN) was examined as a candidate gene for autism spectrum disorders (ASDs). This gene encodes a large extracellular matrix protein that orchestrates neuronal positioning during corticogenesis. The CGG-repeat within the 5' untranslated region of RELN exon 1 was examined in 126 multiple-incidence families. The number of CGG repeats varied from three to 16 in affected individuals and controls, with no expansion or contraction observed during maternal (n = 291) or paternal (n = 287) transmissions in families with autistic probands. Although the frequencies of the RELN alleles and genotypes in affected children were not different from those in the comparison group, a family-based association test (FBAT) showed that the larger RELN alleles >> or = 11 repeats) were transmitted more often than expected to affected children (S = 43, E(S) = 34.5, P = 0.035); this was particularly the case for the 13-repeat RELN allele (S = 22, E(S) = 16, P = 0.034). Affected sib-pair (ASP) analysis found no evidence of excess sharing of RELN alleles in affected siblings. The impact of genotypes with large alleles >> or = 11 repeats) on the phenotypes in individuals with ASD was analyzed by ANOVA in a subset of the families for which results of the Autism Diagnostic Interview-Revised were available. Children with large RELN alleles did not show any difference in scores for questions related to the core symptoms of autistic disorder, but there was a tendency for children with at least one large RELN allele to have an earlier age at first phrase (chi(2) = 3.538, P = 0.06). Thus, although the case-control and affected sib-pair findings did not support a role for RELN in susceptibility to ASD, the more powerful family-based association study demonstrated that RELN alleles with larger numbers of CGG repeats may play a role in the etiology of some cases of ASD, especially in children without delayed phrase speech.

Grid2(Lc) (Lurcher), Grid2(ho) (hot-foot), Rora(sg) (staggerer), nr (nervous), Agtpbp1(pcd) (Purkinje cell degeneration), Reln(rl) (reeler), and Girk2(Wv) (Weaver) are spontaneous mutations with cerebellar atrophy, ataxia, and deficits in motor coordination tasks requiring balance and equilibrium. In addition to these signs, the Dst(dt) (dystonia musculorum) spinocerebellar mutant displays dystonic postures and crawling. More recently, transgenic models with human spinocerebellar ataxia mutations and alterations in calcium homeostasis have been shown to exhibit cerebellar anomalies and motor coordination deficits. We describe neurochemical characteristics of these mutants with respect to regional brain metabolism as well as amino acid and biogenic amine concentrations, uptake sites, and receptors.

Novel target discovery is warranted to improve treatment in adult T-cell acute lymphoblastic leukemia (T-ALL) patients. We provide a comprehensive study on mutations to enhance the understanding of therapeutic targets and studied 81 adult T-ALL patients. NOTCH1 exhibitedthe highest mutation rate (53%). Mutation frequencies of FBXW7 (10%), WT1 (10%), JAK3 (12%), PHF6 (11%), and BCL11B (10%) were in line with previous reports. We identified recurrent alterations in transcription factors DNM2, and RELN, the WNT pathway associated cadherin FAT1, and in epigenetic regulators (MLL2, EZH2). Interestingly, we discovered novel recurrent mutations in the DNA repair complex member HERC1, in NOTCH2, and in the splicing factor ZRSR2. A frequently affected pathway was the JAK/STAT pathway (18%) and a significant proportion of T-ALL patients harboured mutations in epigenetic regulators (33%), both predominantly found in the unfavourable subgroup of early T-ALL. Importantly, adult T-ALL patients not only showed a highly heterogeneous mutational spectrum, but also variable subclonal allele frequencies implicated in therapy resistance and evolution of relapse. In conclusion, we provide novel insights in genetic alterations of signalling pathways (e.g. druggable by γ-secretase inhibitors, JAK inhibitors or EZH2 inhibitors), present in over 80% of all adult T-ALL patients, that could guide novel therapeutic approaches.

Lissencephalies are congenital malformations responsible for epilepsy and mental retardation in children. A number of distinct lissencephaly syndromes have been characterized, according to the aspect and the topography of the cortical malformation, the involvement of other cerebral structures and the identified genetic defect. A mutation in TUBA1A, coding for alpha 1 tubulin, was recently identified in a mutant mouse associated with a behavioural disorder and a disturbance of the laminar cytoarchitectony of the isocortex and the hippocampus. Mutations of TUBA1A were subsequently found in children with mental retardation and brain malformations showing a wide spectrum of severities. Here we describe four fetuses with TUBA1A mutations and a prenatal diagnosis of major cerebral dysgeneses leading to a termination of pregnancy due to the severity of the prognosis. The study of these fetuses at 23, 25, 26 and 35 gestational weeks shows that mutations of TUBA1A are associated with a neuropathological phenotypic spectrum which consistently encompasses five brain structures, including the neocortex, hippocampus, corpus callosum, cerebellum and brainstem. Less constantly, abnormalities were also identified in basal ganglia, olfactory bulbs and germinal zones. At the microscopical level, migration abnormalities are suggested by abnormal cortical and hippocampal lamination, and heterotopic neurons in the cortex, cerebellum and brainstem. There are also numerous neuronal differentiation defects, such as the presence of immature, randomly oriented neurons and abnormal axon tracts and fascicles. Thus, the TUBA1A phenotype is distinct from LIS1, DCX, RELN and ARX lissencephalies. Compared with the phenotypes of children mutated for TUBA1A, these prenatally diagnosed fetal cases occur at the severe end of the TUBA1A lissencephaly spectrum. This study emphasizes the importance of neuropathological examinations in cases of lissencephaly for improving our knowledge of the distinct pathogenetic and pathophysiological mechanisms.

The malformations of the cerebral cortex represent a major cause of developmental disabilities, severe epilepsy and reproductive disadvantage. The advent of high-resolution MRI techniques has facilitated the in vivo identification of a large group of cortical malformation phenotypes. Several malformation syndromes caused by abnormal cortical development have been recognised and specific causative gene defects have been identified. Periventricular nodular heterotopia (PNH) is a malformation of neuronal migration in which a subset of neurons fails to migrate into the developing cerebral cortex. X-linked PNH is mainly seen in females and is often associated with focal epilepsy. FLNA mutations have been reported in all familial cases and in about 25% of sporadic patients. A rare recessive form of PNH due ARGEF2 gene mutations has also been reported in children with microcephaly, severe delay and early seizures. Lissencephaly-pachygyria and subcortical band heterotopia (SBH) are disorders of neuronal migration and represent a malformative spectrum resulting from mutations of either LIS1 or DCX genes. LIS1 mutations cause a more severe malformation in the posterior brain regions. Most children have severe developmental delay and infantile spasms, but milder phenotypes are on record, including posterior SBH owing to mosaic mutations of LIS1. DCX mutations usually cause anteriorly predominant lissencephaly in males and SBH in female patients. Mutations of DCX have also been found in male patients with anterior SBH and in female relatives with normal brain magnetic resonance imaging. Autosomal recessive lissencephaly with cerebellar hypoplasia, accompanied by severe delay, hypotonia, and seizures, has been associated with mutations of the reelin (RELN) gene. X-linked lissencephaly with corpus callosum agenesis and ambiguous genitalia in genotypic males is associated with mutations of the ARX gene. Affected boys have severe delay and seizures with suppression-burst EEG. Early death is frequent. Carrier female patients can have isolated corpus callosum agenesis. Among several syndromes featuring polymicrogyria, bilateral perisylvian polymicrogyria shows genetic heterogeneity, including linkage to chromosome Xq28 in some pedigrees, autosomal dominant or recessive inheritance in others, and an association with chromosome 22q11.2 deletion in some patients. About 65% of patients have severe epilepsy. Recessive bilateral frontoparietal polymicrogyria has been associated with mutations of the GPR56 gene. Epilepsy is often present in patients with cortical malformations and tends to be severe, although its incidence and type vary in different malformations. It is estimated that up to 40% of children with drug-resistant epilepsy have a cortical malformation. However, the physiopathological mechanisms relating cortical malformations to epilepsy remain elusive.

Schizophrenia is a common and complex mental disorder. Hereditary factors are important for its etiology, but despite linkage signals reported to several chromosomal regions in different populations, final identification of predisposing genes has remained a challenge. Utilizing a large family-based schizophrenia study sample from Finland, we have identified several linked loci: 1q32.2-q42, 2q, 4q31, 5q and 7q22. In this study, an independent sample of 352 nuclear schizophrenia families (n=1626) allowed replication of linkage on 7q21-32. In a sample of 245 nuclear families (n=1074) originating from the same geographical region as the families revealing the linkage, SNP and microsatellite association analyses of the four regional candidate genes, GRM3, RELN, SEMA3A and VGF, revealed no significant association to the clinical diagnosis of schizophrenia. Instead, quantifiable trait component analyses with neuropsychological endophenotypes available from 186 nuclear families (n=861) of the sample showed significant association to RELN variants for traits related to verbal (P=0.000003) and visual working memory (P=0.002), memory (P=0.002) and executive functioning (P=0.002). Trait-associated allele-positive subjects scored lower in the tests measuring working memory (P=0.0004-0.0000000004), memory (P=0.02-0.0001) and executive functioning (P=0.001). Our findings suggest that allelic variants of RELN contribute to the endophenotypes of schizophrenia.

Reelin is the protein defective in reeler mutant mice [I. Bar, C. Lambert de Rouvroit, I. Royaux, D.B. Krizman, C. Dernoncourt, D. Ruelle, M.C. Beckers, A.M. Goffinet, A YAC contig containing the reeler locus with preliminary characterization of candidate gene fragments, Genomics 26 (1995) 543-549; G. D'Arcangelo, G.G. Miao, S.C. Chen, H.D. Soares, J.I. Morgan, T. Curran, A protein related to extracellular matrix proteins deleted in the mouse mutant reeler, Nature 374 (1995) 719-723; S. Hirotsune, T. Takahara, N. Sasaki, K. Hirose, A. Yoshiki, T. Ohashi, M. Kusakabe, Y. Murakami, M. Muramatsu, S. Watanabe, K. Nakao, M. Katsuki, Y. Hayashizaki, The reeler gene encodes a protein with an EGF-like motif expressed by pioneer neurons, Nature Genet. 10 (1995) 77-83]. In the Orleans allele of reeler (symbol: Reln[rl-Orl]), a 220 nucleotide deletion is present in the 3' region of the Reelin message, resulting in a frame shift with production of a predicted protein amputated from its C-terminal amino acids. In this study, we first show that the predicted truncated protein indeed exists in Orleans reeler mice, using several anti-Reelin antibodies. Three antibodies are directed against epitopes located in the N-terminal region of the protein, namely: monoclonal antibody CR-50 [M. Ogawa, T. Miyata, K. Nakajima, K. Yagyu, M. Seike, K. Ikenaka, H. Yamamoto, K. Mikoshiba, The reeler gene-associated antigen on Cajal-Retzius neurons is a crucial molecule for laminar organization of cortical neurons, Neuron 14 (1995) 899-912] (epitope region between Reelin residues 251-407), monoclonal antibody G10 (epitope located between amino acids 199 and 244) and the polyclonal antipeptide rp4 (positions 381-399). A fourth antibody, antipeptide rp5, reacts with the C-terminal (3443-3461) Reelin sequence. In normal embryos, all four antibodies stained cells in the marginal zone with features of Cajal-Retzius cells. While N-terminal specific antibodies detected Reelin immunoreactivity in mouse embryos homozygous for the reeler-Orleans mutation, no staining was obtained with the rp5 antibody, showing the presence of a truncated protein. Moreover, although Reelin could be detected at the surface of living Cajal-Retzius cells of normal mice, it was not revealed after vital staining of embryonic cortex from Orleans reeler mice. These results indicate that the C-terminal region of Reelin is essential for its secretion and suggest that the Orleans reeler phenotype is due to defective Reelin secretion rather than to secretion of an inactive protein.

Gastric cancer (GC) is an important cause of morbidity and mortality worldwide. In addition to environmental factors, genetic factors also play an important role in GC etiology, as demonstrated by the fact that only a small proportion of individuals exposed to the known environmental risk factors develop GC. Molecular studies have provided evidence that GC arises not only from the combined effects of environmental factors and susceptible genetic variants but also from the accumulation of genetic and epigenetic alterations that play crucial roles in the process of cellular immortalization and tumorigenesis. This review is intended to focus on the recently described basic aspects that play key roles in the process of gastric carcinogenesis. Genetic variation in the genes DNMT3A, PSCA, VEGF, and XRCC1 has been reported to modify the risk of developing gastric carcinoma. Several genes have been newly associated with gastric carcinogenesis, both through oncogenic activation (MYC, SEMA5A, BCL2L12, RBP2 and BUBR1) and tumor suppressor gene inactivation mechanisms (KLF6, RELN, PTCH1A, CLDN11, and SFRP5). At the level of gastric carcinoma treatment, the HER-2 tyrosine kinase receptor has been demonstrated to be a molecular target of therapy.

Reelin (Reln) is a glycoprotein that in postnatal and adult mammalian brain is believed to be secreted from telencephalic GABAergic interneurons and cerebellar glutamatergic granule neurons into the extracellular matrix. To address the question of whether Reln neurosecretion occurs via a regulated or a constitutive process, we exposed postnatal rat cerebellar granule neurons (CGNs) maintained in culture for 7-9 days to: (i) 100 microM N-methyl-D-aspartate (NMDA) in a Mg(+2)-free medium to stimulate NMDA-selective glutamate receptors and Ca(2+)-dependent neurotransmitter release, (ii) 50 mM KCl to depolarize the cells and elicit Ca(2+)-dependent exocytosis, (iii) 10-100 microM nicotine to activate excocytosis by nicotinic receptors present in these cells, (iv) 10 microM 1,2,3,4-tetrahydro-6-nitro-2, 3-dioxo-benzo[f]quinoxaline-7-sulfonamide in combination with 10 microM dizocilpine to block alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid- and NMDA-preferring glutamate receptors activated by endogenously released glutamate, or (v) EGTA (5 mM) to virtually eliminate extracellular Ca(2+) and block Ca(2+)-dependent exocytosis. Although, CGNs express and secrete Reln (measured by quantitative immunoblotting), none of the above-mentioned conditions that control regulated exocytosis alters the stores or the rate of Reln release. In contrast, application of either: (i) a Reln antisense oligonucleotide (5'-GCAATGTGCAGGGAAATG-3') (10 microM) that reduces Reln biosynthesis or (ii) brefeldin A (5 x 10(-5) M), an inhibitor of the traffic of proteins between the endoplasmic reticulum and the Golgi network, sharply curtail the rate of Reln secretion. Because, in subcellular fractionation studies, we have shown that Reln is not contained in synaptic vesicles, these data suggest that Reln secretion from CGNs does not require Ca(2+)-dependent exocytosis, but probably is related to a Reln pool stored in Golgi secretory vesicles mediating a constitutive secretory pathway.

Detailed classification of brain malformations such as lissencephaly has led to the positional cloning of genes required for normal neuronal migration and the identification of unique molecular pathways governing brain structure. While classical magnetic resonance imaging (MRI) patterns of lissencephaly involve primarily the cerebral cortex, malformations in this spectrum can be associated with significant cerebellar underdevelopment and have recently been referred to as lissencephaly with cerebellar hypoplasia (LCH). The phenotypic features of 34 children were found to define 6 subtypes of LCH. Two of these (LCHa and LCHb) were associated with mutation in the LIS1, DCX and RELN genes, respectively. Gene mutations that exemplify four additional classes (LCHc, d, e and f) remained to be determined. Phenotypic features included small head circumference, cortical malformation ranging from agyria to simplification of the gyral pattern and from near normal cortical thickness to marked thickening of the cortical gray matter. Cerebellar manifestations ranged from midline hypoplasia to diffuse volume reduction and disturbed foliation. We conclude that LCH is within the spectrum of DCX and LIS1 mutations, that LCH associated with RELN mutation is distinguished by the severity of cerebellar and hippocampal involvement, and that several distinctive patterns indicate additional genetic mutations that can produce LCH.

No specific gene has been identified for any major psychiatric disorder, including schizophrenia, in spite of strong evidence supporting a genetic basis for these complex and devastating disorders. There are several likely reasons for this failure, ranging from poor study design with low statistical power to genetic mechanisms such as polygenic inheritance, epigenetic interactions, and pleiotropy. Most study designs currently in use are inadequate to uncover these mechanisms. However, to date, genetic studies have provided some valuable insight into the causes and potential therapies for psychiatric disorders. There is a growing body of evidence suggesting that the understanding of the genetic etiology of psychiatric illnesses, including schizophrenia, will be more successful with integrative approaches considering both genetic and epigenetic factors. For example, several genes including those encoding dopamine receptors (DRD2, DRD3, and DRD4), serotonin receptor 2A (HTR2A) and catechol-O-methyltransferase (COMT) have been implicated in the etiology of schizophrenia and related disorders through meta-analyses and large, multicenter studies. There is also growing evidence for the role of DRD1, NMDA receptor genes (GRIN1, GRIN2A, GRIN2B), brain-derived neurotrophic factor (BDNF), and dopamine transporter (SLC6A3) in both schizophrenia and bipolar disorder. Recent studies have indicated that epigenetic modification of reelin (RELN), BDNF, and the DRD2 promoters confer susceptibility to clinical psychiatric conditions. Pharmacologic therapy of psychiatric disorders will likely be more effective once the molecular pathogenesis is known. For example, the hypoactive alleles of DRD2 and the hyperactive alleles of COMT, which degrade the dopamine in the synaptic cleft, are associated with schizophrenia. It is likely that insufficient dopaminergic transmission in the frontal lobe plays a role in the development of negative symptoms associated with this disorder. Antipsychotic therapies with a partial dopamine D2 receptor agonist effect may be a plausible alternative to current therapies, and would be effective in symptom reduction in psychotic individuals. It is also possible that therapies employing dopamine D1/D2 receptor agonists or COMT inhibitors will be beneficial for patients with negative symptoms in schizophrenia and bipolar disorder. The complex etiology of schizophrenia, and other psychiatric disorders, warrants the consideration of both genetic and epigenetic systems and the careful design of experiments to illumine the genetic mechanisms conferring liability for these disorders and the benefit of existing and new therapies.

Reelin, a large glycoprotein secreted by telencephalic GABAergic neurons, plays an important role in neuronal guidance embryonically and in synaptic plasticity postnatally. The reeler heterozygous mouse (+/rl) appears superficially normal but has been of interest as an animal model for psychosis since the discovery that reelin is 50% down-regulated in postmortem psychotic brain. Brain abnormalities in +/rl are similar to psychotic brain and include a reduction in glutamic acid de carboxylase 67 (GAD67), dendritic arbors and spine density in cortex and hippocampus, and abnormalities in synaptic function including long-term potentiation (LTP). In spite of these abnormalities, behavioral abnormalities in +/rl are subtle and controversial. Recent findings indicate that the reelin (RELN) and GAD67 promoters are hypermethylated in GABAergic neurons of psychotic postmortem brain and that DNA methyltransferase 1 (DNMT1) is up-regulated. Hypermethlyation of RELN and GAD67 promoters can be induced by treating mice with methionine, and these mice display brain and behavioral abnormalities similar to +/rl. Thus, an animal model that combines genetic heterozygocity with epigenesis holds promise for understanding the role of Reelin down-regulation in psychosis.

Collapsin response mediator protein 1 (CRMP1) is one of the CRMP family members that mediates signal transduction of axon guidance molecules. Here, we show evidence that CRMP1 is involved in Reelin (Reln) signaling to regulate neuronal migration in the cerebral cortex. In crmp1-/- mice, radial migration of cortical neurons was retarded. This phenotype was not observed in the sema3A-/- and crmp1+/-;sema3A+/- cortices. However, CRMP1 was colocalized with disabled-1 (Dab1), an adaptor protein in Reln signaling. In the Reln(rl/rl) cortex, CRMP1 and Dab1 were expressed at a higher level, yet tyrosine phosphorylated at a lower level. Loss of crmp1 in a dab1 heterozygous background led to the disruption of hippocampal lamination, a Reeler-like phenotype. In addition to axon guidance, CRMP1 regulates neuronal migration by mediating Reln signaling.

Genetic studies indicate that chromosome 7q is likely to contain an autism susceptibility locus (AUTS1). We have followed a positional candidate gene approach to identify relevant gene(s) and report here the analysis of reelin (RELN), a gene located under our peak of linkage. Screening RELN for DNA changes identified novel missense variants absent in a large control group; however, the low frequency of these mutations does not explain the relatively strong linkage results on 7q. Furthermore, analysis of a previously reported triplet repeat polymorphism and intragenic single nucleotide polymorphisms, using the transmission disequilibrium test, provided no evidence for association with autism in IMGSAC and German singleton families. The analysis of RELN suggests that it probably does not play a major role in autism aetiology, although further analysis of several missense mutations is warranted in additional affected individuals.

Ductal adenocarcinoma of the pancreas is the fourth leading cause of cancer death and is usually diagnosed late. Intraductal papillary mucinous neoplasms are an increasingly recognized precursor to invasive ductal adenocarcinoma of the pancreas. Identifying the alterations in DNA methylation that arise during intraductal papillary mucinous neoplasm development may facilitate the development of markers that could be used to differentiate intraductal papillary mucinous neoplasms from non-neoplastic pancreatic cystic lesions. Surgically resected intraductal papillary mucinous neoplasms and adjacent ductal adenocarcinomas were microdissected from 50 patients. Normal pancreas was also obtained from 27 patients with intraductal papillary mucinous neoplasms or pancreatic adenocarcinomas and 10 patients with well-differentiated pancreatic endocrine neoplasms. Methylation-specific PCR was performed on isolated DNA for seven genes (SPARC, SARP2, TSLC1, RELN, TFPI2, CLDN5, UCHL1) known to be commonly aberrantly methylated in pancreatic ductal adenocarcinomas. The mean percentage of genes methylated in invasive ductal adenocarcinomas arising in association with an intraductal papillary mucinous neoplasm (mean+/-s.d., 81+/-17%) was significantly higher than that in noninvasive-intraductal papillary mucinous neoplasms (57+/-26%, P=0.007) or peritumoral normal epithelial cells (22+/-17%, P<0.0001). Carcinomas (intraductal papillary mucinous neoplasms with carcinoma in situ or their associated infiltrating adenocarcinoma) had significantly more methylated genes (71+/-19%) than low-grade (low and moderate dysplasia) intraductal papillary mucinous neoplasms (44+/-26%, P<0.0001). The mean percentage of genes methylated in histologically normal pancreatic ductal cells from patients with ductal neoplasia (22+/-17%) was significantly higher than in normal ductal cells from patients with well-differentiated pancreatic endocrine neoplasms (4+/-7%, P=0.002). Thus, aberrant DNA methylation increases with histologic grades of intraductal papillary mucinous neoplasm. Low-level aberrant methylation in the normal ductal cells is more prevalent in patients with ductal neoplasia than in controls without ductal neoplasms and may contribute to carcinogenesis. The detection of aberrant methylation in pancreatic cystic lesions could facilitate the diagnosis of intraductal papillary mucinous neoplasms.

Neurofibrillary tangles comprised of highly phosphorylated tau proteins are a key component of Alzheimer's disease pathology. Mice lacking Reelin (Reln), double-knockouts lacking the VLDL receptor (VLDLR) and ApoE receptor2 (ApoER2), and mice lacking disabled-1 (Dab1) display increased levels of phosphorylated tau. Because Reln binds to recombinant ApoE receptors, assembly of a Reln/ApoE-receptor/Dab1 (RAD) complex may initiate a signal transduction cascade that controls tau phosphorylation. Conversely, disruption of this RAD complex may increase tau phosphorylation and lead to neurodegeneration. To substantiate this concept, we mated Reln-deficient mice to ApoE-deficient mice and found that in the absence of Reln, tau phosphorylation increased as the amount of ApoE decreased. Paralleling the change in tau phosphorylation levels, we found that GSK-3beta activity increased in Reln-deficient mice and further increased in mice lacking both Reln and ApoE. CDK-5 activity was similar in mice lacking Reln, ApoE, or both. GSK-3beta and CDK-5 activity increased in Dab1-deficient mice, independent of ApoE levels. Further supporting the idea that increased tau phosphorylation results primarily from increased kinase activity, the activity of two phosphatases was similar in all conditions tested. These data support a novel, ligand-mediated signal transduction cascade--initiated by the assembly of a RAD complex that suppresses kinase activity and controls tau phosphorylation.

Reelin (Reln) is a protein involved in migration of newborn neurons during development. Reln mutations produce the reeler phenotype in mice, which is characterized by a defect in brain lamination, and autosomal recessive lissencephaly in humans. Reln expression persists in adult brain, but little is known about its function. We used reeler mice to investigate the effects of Reln deficiency on neurogenesis and the response to injury in the adult brain. Newborn neurons were decreased in number in the dentate gyrus and rostral migratory stream of reeler, compared to wild-type, mice. This was due, at least in part, to impaired cell migration. In addition, reeler mice showed increased susceptibility to ischemic brain injury. Cerebral infarcts from middle cerebral artery occlusion were larger in reeler than in wild-type mice, and associated neurobehavioral abnormalities were more severe. The brains of reeler mice also showed larger excitotoxic lesions after the intracerebral injection of N-methyl-D-aspartate. Finally, despite the fact that reeler mice had larger cerebral infarcts, the ischemia-induced enhancement of neurogenesis observed in wild-type mice was attenuated. These findings suggest that, in addition to its neurodevelopmental effects, Reln deficiency continues to influence neurogenesis and ischemic neuronal injury in the adult brain.

Lissencephaly is traditionally divided into 2 distinct pathologic forms: classic (type I) and cobblestone (type II). To date, mutations in 4 genes, LIS1, DCX, RELN, and ARX, have been associated with distinct type I lissencephaly syndromes. Each of these genes has been shown to play a role in normal cell migration, consistent with the presumed pathogenesis of type I lissencephaly. Based on these data, we hypothesized that all forms of radiographically defined type I lissencephaly independent of genotype would be pathologically similar. To test this hypothesis, we examined brains from 16 patients, including 15 lissencephalic patients and one patient with subcortical band heterotopia. Of these 16 patients, 6 had LIS1 deletions, 2 had DCX mutations, and 2 had ARX mutations. In addition, 6 patients had no defined genetic defect, although the patient with subcortical band heterotopia exhibited the same pattern of malformation expected with an XLIS mutation. In all cases, the cortex was thickened; however, the topographic distribution of the cortical pathology varied, ranging from frontal- to occipital-biased pathology to diffuse involvement of the neocortex. Although brains with LIS1 deletions exhibited the classic 4-layer lissencephalic architecture, patients with DCX and ARX mutations each had unique cytoarchitectural findings distinct from LIS1. Furthermore, 2 of the 5 patients with no known genetic defect showed a fourth type of histopathology characterized by a 2-layered cortex. Interestingly, the 2 brains with the fourth type of lissencephaly showed profound brainstem and cerebellar abnormalities. In summary, we identified at least 4 distinct histopathologic subtypes of lissencephaly that stratify with the underlying genetic defect. Based on these data, a new classification for lissencephaly is proposed that incorporates both pathologic and genetic findings.