In reeler mutant mice, which are deficient in reelin (Reln), the lamination of the cerebral cortex is disrupted. Reelin signaling induces phosphorylation of LIM kinase 1, which phosphorylates the actin-depolymerizing protein cofilin in migrating neurons. Conditional cofilin mutants show neuronal migration defects. Thus, both reelin and cofilin are indispensable during cortical development. To analyze the effects of cofilin phosphorylation on neuronal migration we used in utero electroporation to transfect E14.5 wild-type cortical neurons with pCAG-EGFP plasmids encoding either a nonphosphorylatable form of cofilin 1 (cofilin(S3A)), a pseudophosphorylated form (cofilin(S3E)) or wild-type cofilin 1 (cofilin(WT)). Wild-type controls and reeler neurons were transfected with pCAG-EGFP. Real-time microscopy and histological analyses revealed that overexpression of cofilin(WT) and both phosphomutants induced migration defects and morphological abnormalities of cortical neurons. Of note, reeler neurons and cofilin(S3A)- and cofilin(S3E)-transfected neurons showed aberrant backward migration towards the ventricular zone. Overexpression of cofilin(S3E), the pseudophosphorylated form, partially rescued the migration defect of reeler neurons, as did overexpression of Limk1. Collectively, the results indicate that reelin and cofilin cooperate in controlling cytoskeletal dynamics during neuronal migration.

A single nucleotide polymorphism (rs7341475) in RELN has recently been shown to be associated with schizophrenia (SZ) in an Ashkenazi Jewish (AJ) case--control study specifically in women by Shifman et al. We have replicated this association in women in another large independent Ashkenazi Jewish collection (721 cases, 259 female; 1455 controls, 834 female) and confirmed that it applies to both SZ and schizoaffective disorder. Furthermore, we explore the effects of this polymorphism through quantitative trait loci analysis of nine SZ related factors providing information on sex-specific genotype--phenotype correlations.

The effect of exogenously administered manganese (Mn) on developmental neurogenesis in the hippocampal dentate gyrus was examined in male mice after maternal exposure to MnCl(2) (0, 32, 160, or 800 ppm as Mn in diet) from gestational day 10 to day 21 after delivery on weaning. Immunohistochemistry was performed to monitor neurogenesis and interneuron subpopulations on postnatal days (PNDs) 21 and 77 (adult stage). Reelin-synthesizing γ-aminobutyric acid (GABA)ergic interneurons increased in the hilus with ≥ 160 ppm on weaning to sustain to PND 77 at 800 ppm. Apoptosis in the neuroblast-producing subgranular zone increased with 800 ppm and TUC4-expressing immature granule cells decreased with 800 ppm on weaning, whereas at the adult stage, immature granule cells increased. On PND 21, transcript levels increased with Reln and its receptor gene Lrp8 and decreased with Dpysl3 coding TUC4 in the dentate gyrus, confirming immunohistochemical results. Double immunohistochemistry revealed a sustained increase of reelin-expressing and NeuN-lacking or weakly positive immature interneurons and NeuN-expressing mature neurons in the hilus through to the adult stage as examined at 800 ppm. Brain Mn concentrations increased at both PNDs 21 and 77 in all MnCl(2)-exposed groups. These results suggest that Mn targets immature granule cells causing apoptosis and neuronal mismigration. Sustained increases in immature reelin-synthesizing GABAergic interneurons may represent continued aberration in neurogenesis and following migration to cause an excessive response for overproduction of immature granule cells through to the adult stage. Sustained high concentration of Mn in the brain may be responsible for these changes.

The autism spectrum disorders (ASD) comprise a broad group of behaviorally related neurodevelopmental disorders affecting as many as 1 in 68 children. The hallmarks of ASD consist of impaired social and communication interactions, pronounced repetitive behaviors and restricted patterns of interests. Family, twin and epidemiological studies suggest a polygenetic and epistatic susceptibility model involving the interaction of many genes; however, the etiology of ASD is likely to be complex and include both epigenetic and environmental factors. 5-hydroxymethylcytosine (5hmC) is a novel environmentally sensitive DNA modification that is highly enriched in post-mitotic neurons and is associated with active transcription of neuronal genes. Here, we used an established chemical labeling and affinity purification method coupled with high-throughput sequencing technology to generate a genome-wide profile of striatal 5hmC in an autism mouse model (Cntnap2(-/-) mice) and found that at 9 weeks of age the Cntnap2(-/-) mice have a genome-wide disruption in 5hmC, primarily in genic regions and repetitive elements. Annotation of differentially hydroxymethylated regions (DhMRs) to genes revealed a significant overlap with known ASD genes (e.g. Nrxn1 and Reln) that carried an enrichment of neuronal ontological functions, including axonogenesis and neuron projection morphogenesis. Finally, sequence motif predictions identified associations with transcription factors that have a high correlation with important genes in neuronal developmental and functional pathways. Together, our data implicate a role for 5hmC-mediated epigenetic modulation in the pathogenesis of autism and represent a critical step toward understanding the genome-wide molecular consequence of the Cntnap2 mutation, which results in an autism-like phenotype.

Neuronal migration disorders are human (or animal) diseases that result from a disruption in the normal movement of neurons from their original birth site to their final destination during early development. As a consequence, the neurons remain somewhere along their migratory route, their location depending on the pathological mechanism and its severity. The neurons form characteristic abnormalities, which are morphologically classified into several types, such as lissencephaly, heterotopia, and cobblestone dysplasia. Polymicrogyria is classified as a group of malformations that appear secondary to post-migration development; however, recent findings of the underlying molecular mechanisms reveal overlapping processes in the neuronal migration and post-migration development stages. Mutations of many genes are involved in neuronal migration disorders, such as LIS1 and DCX in classical lissencephaly spectrum, TUBA1A in microlissencephaly with agenesis of the corpus callosum, and RELN and VLDLR in lissencephaly with cerebellar hypoplasia. ARX is of particular interest from basic and clinical perspectives because it is critically involved in tangential migration of GABAergic interneurons in the forebrain and its mutations cause a variety of phenotypes ranging from hydranencephaly or lissencephaly to early-onset epileptic encephalopathies, including Ohtahara syndrome and infantile spasms or intellectual disability with no brain malformations. The recent advances in gene and genome analysis technologies will enable the genetic basis of neuronal migration disorders to be unraveled, which, in turn, will facilitate genotype-phenotype correlations to be determined.

Recent studies have suggested that lymphatics help to restore heart function after cardiac injury^1-6. Here we report that lymphatics promote cardiac growth, repair and cardioprotection in mice. We show that a lymphoangiocrine signal produced by lymphatic endothelial cells (LECs) controls the proliferation and survival of cardiomyocytes during heart development, improves neonatal cardiac regeneration and is cardioprotective after myocardial infarction. Embryos that lack LECs develop smaller hearts as a consequence of reduced cardiomyocyte proliferation and increased cardiomyocyte apoptosis. Culturing primary mouse cardiomyocytes in LEC-conditioned medium increases cardiomyocyte proliferation and survival, which indicates that LECs produce lymphoangiocrine signals that control cardiomyocyte homeostasis. Characterization of the LEC secretome identified the extracellular protein reelin (RELN) as a key component of this process. Moreover, we report that LEC-specific Reln-null mouse embryos develop smaller hearts, that RELN is required for efficient heart repair and function after neonatal myocardial infarction, and that cardiac delivery of RELN using collagen patches improves heart function in adult mice after myocardial infarction by a cardioprotective effect. These results highlight a lymphoangiocrine role of LECs during cardiac development and injury response, and identify RELN as an important mediator of this function.

Purpose: Sarcomatoid renal cell carcinoma (SRCC) ranks among the most aggressive clinicopathologic phenotypes of RCC. However, the paucity of high-quality, genome-wide molecular examinations of SRCC has hindered our understanding of this entity.Experimental Design: We interrogated the mutational, copy number, and transcriptional characteristics of SRCC and compared these data with those of nonsarcomatoid RCC (RCC). We evaluated whole-exome sequencing, single-nucleotide polymorphism, and RNA sequencing data from patients with SRCC (n = 65) and RCC (n = 598) across different parent RCC subtypes, including clear-cell RCC, papillary RCC, and chromophobe RCC subtypes.Results: SRCC was molecularly discrete from RCC and clustered according to its parent RCC subtype, though with upregulation of TGFβ signaling across all subtypes. The epithelioid (E-) and spindled (S-) histologic components of SRCC did not show differences in mutational load among cancer-related genes despite a higher mutational burden in S-. Notably, sarcomatoid clear-cell RCC (SccRCC) showed significantly fewer deletions at 3p21-25, a lower rate of two-hit loss for VHL and PBRM1, and more mutations in PTEN, TP53, and RELN compared with ccRCC. A two-hit loss involving VHL predicted for ccRCC and a better prognosis, whereas mutations in PTEN, TP53, or RELN predicted for SccRCC and worse prognosis.Conclusions: SRCC segregates by parent subtype, and SccRCC has a fundamentally different early molecular pathogenesis, usually lacking the classic 3p21-25 deletion and showing distinctive mutational and transcriptional profiles. These features prompt a more precise molecular classification of RCC, with diagnostic, prognostic, and therapeutic implications. Clin Cancer Res; 23(21); 6686-96. ©2017 AACRSee related commentary by Bergerot et al., p. 6381.

The mechanisms underlying the neurodevelopmental deficits associated with CHARGE syndrome, which include cerebellar hypoplasia, developmental delay, coordination problems, and autistic features, have not been identified. CHARGE syndrome has been associated with mutations in the gene encoding the ATP-dependent chromatin remodeler CHD7. CHD7 is expressed in neural stem and progenitor cells, but its role in neurogenesis during brain development remains unknown. Here we have shown that deletion of Chd7 from cerebellar granule cell progenitors (GCps) results in reduced GCp proliferation, cerebellar hypoplasia, developmental delay, and motor deficits in mice. Genome-wide expression profiling revealed downregulated expression of the gene encoding the glycoprotein reelin (Reln) in Chd7-deficient GCps. Recessive RELN mutations have been associated with severe cerebellar hypoplasia in humans. We found molecular and genetic evidence that reductions in Reln expression contribute to GCp proliferative defects and cerebellar hypoplasia in GCp-specific Chd7 mouse mutants. Finally, we showed that CHD7 is necessary for maintaining an open, accessible chromatin state at the Reln locus. Taken together, this study shows that Reln gene expression is regulated by chromatin remodeling, identifies CHD7 as a previously unrecognized upstream regulator of Reln, and provides direct in vivo evidence that a mammalian CHD protein can control brain development by modulating chromatin accessibility in neuronal progenitors.

SMARCC2 (BAF170) is one of the invariable core subunits of the ATP-dependent chromatin remodeling BAF (BRG1-associated factor) complex and plays a crucial role in embryogenesis and corticogenesis. Pathogenic variants in genes encoding other components of the BAF complex have been associated with intellectual disability syndromes. Despite its significant biological role, variants in SMARCC2 have not been directly associated with human disease previously. Using whole-exome sequencing and a web-based gene-matching program, we identified 15 individuals with variable degrees of neurodevelopmental delay and growth retardation harboring one of 13 heterozygous variants in SMARCC2, most of them novel and proven de novo. The clinical presentation overlaps with intellectual disability syndromes associated with other BAF subunits, such as Coffin-Siris and Nicolaides-Baraitser syndromes and includes prominent speech impairment, hypotonia, feeding difficulties, behavioral abnormalities, and dysmorphic features such as hypertrichosis, thick eyebrows, thin upper lip vermilion, and upturned nose. Nine out of the fifteen individuals harbor variants in the highly conserved SMARCC2 DNA-interacting domains (SANT and SWIRM) and present with a more severe phenotype. Two of these individuals present cardiac abnormalities. Transcriptomic analysis of fibroblasts from affected individuals highlights a group of differentially expressed genes with possible roles in regulation of neuronal development and function, namely H19, SCRG1, RELN, and CACNB4. Our findings suggest a novel SMARCC2-related syndrome that overlaps with neurodevelopmental disorders associated with variants in BAF-complex subunits.

Cure rates of children and adults with acute myeloid leukaemia (AML) remain unsatisfactory partly due to chemotherapy resistance. We investigated the genetic basis of AML in 107 primary cases by sequencing 670 genes mutated in haematological malignancies. SETBP1, ASXL1 and RELN mutations were significantly associated with primary chemoresistance. We identified genomic alterations not previously described in AML, together with distinct genes that were significantly overexpressed in therapy-resistant AML. Defined gene mutations were sufficient to explain primary induction failure in only a minority of cases. Thus, additional genetic or molecular mechanisms must cause primary chemoresistance in paediatric and adult AML.

REELIN (RELN) is a large (420 kDa) glycoprotein that in adulthood is mostly synthesized in GABAergic neurons of corticolimbic structures. Upon secretion in the extracellular matrix (ECM), RELN binds to VLDL, APOE2, and α3β2 Integrin receptors located on dendritic shafts and spines of postsynaptic pyramidal neurons. Reduced levels of RELN expression in the adult brain induce cognitive impairment and dendritic spine density deficits. RELN supplementation recovers these deficits suggesting a trophic action for RELN in synaptic plasticity. We and others have shown that altered RELN expression in schizophrenia (SZ) and bipolar (BP) disorder patients is difficult to reconcile with classical Mendelian genetic disorders and it is instead plausible to associate these disorders with altered epigenetic homeostasis. Support for the contribution of altered epigenetic mechanisms in the down-regulation of RELN expression in corticolimbic structures of psychotic patients includes the concomitant increase of DNA-methyltransferases and the increased levels of the methyl donor S-adenosylmethionine (SAM). It is hypothesized that these conditions lead to RELN promoter hypermethylation and a reduction in RELN protein amounts in psychotic patients. The decreased synthesis and release of RELN from GABAergic corticolimbic neurons could serve as a model to elucidate the epigenetic pathophysiological mechanisms acting at pyramidal neuron dendrites that regulate synaptic plasticity and cognition in psychotic and non-psychotic subjects.

OBJECTIVE

To estimate diagnostic yield and genotype-phenotype correlations in a cohort of 811 patients with lissencephaly or subcortical band heterotopia.

METHODS

We collected DNA from 756 children with lissencephaly over 30 years. Many were tested for deletion 17p13.3 and mutations of LIS1, DCX, and ARX, but few other genes. Among those tested, 216 remained unsolved and were tested by a targeted panel of 17 genes (ACTB, ACTG1, ARX, CRADD, DCX, LIS1, TUBA1A, TUBA8, TUBB2B, TUBB, TUBB3, TUBG1, KIF2A, KIF5C, DYNC1H1, RELN, and VLDLR) or by whole-exome sequencing. Fifty-five patients studied at another institution were added as a validation cohort.

RESULTS

The overall mutation frequency in the entire cohort was 81%. LIS1 accounted for 40% of patients, followed by DCX (23%), TUBA1A (5%), and DYNC1H1 (3%). Other genes accounted for 1% or less of patients. Nineteen percent remained unsolved, which suggests that several additional genes remain to be discovered. The majority of unsolved patients had posterior pachygyria, subcortical band heterotopia, or mild frontal pachygyria.

CONCLUSIONS

The brain-imaging pattern correlates with mutations in single lissencephaly-associated genes, as well as in biological pathways. We propose the first LIS classification system based on the underlying molecular mechanisms.

Array-based profiling studies have shown implication of aberrant gene expression patterns in epileptogenesis. We have performed transcriptome analysis of hippocampal tissues resected from patients with MTLE-HS using RNAseq approach. Healthy tissues from tumour margins obtained during tumour surgeries were used as non-epileptic controls. RNA sequencing was performed using standard protocols on Illumina HiSeq 2500 platform. Differential gene expression analysis of the RNAseq data revealed 56 significantly regulated genes in MTLE patients. Gene cluster analysis identified 3 important hubs of genes mostly linked to, neuroinflammation and innate immunity, synaptic transmission and neuronal network modulation which are supportive of intrinsic severity hypothesis of pharmacoresistance. This study identified various genes like FN1 which is central in our analysis, NEUROD6, RELN, TGFβR2, NLRP1, SCRT1, CSNK2B, SCN1B, CABP1, KIF5A and antisense RNAs like AQP4-AS1 and KIRREL3-AS2 providing important insight into the understanding of the pathophysiology or genomic basis of drug refractory epilepsy due to MTS.

Recent advances in schizophrenia and bipolar disorder research suggest that a dysfunction of GABAergic neurotransmission that is operative in telencephalic structures may be an important dynamic mechanism associated with psychosis. We propose that this dysfunction is probably mediated by the hypermethylation of glutamic acid decarboxylase (GAD67), reelin and other gene promoters expressed in GABAergic neurons. A pharmacological strategy that reduces the hypermethylation of GABAergic promoters is to administer drugs (i.e., valproate [VPA]) that induce DNA demethylation by facilitating chromatin remodeling. The enhanced clinical efficacy of atypical antipsychotics when co-administered with VPA prompted us to investigate whether this increased drug efficacy is related to a modification of GABAergic promoter methylation via chromatin remodeling. Our previous and present results strongly suggest that when associated with VPA, clozapine or sulpiride, but not haloperidol or olanzapine, facilitate chromatin remodeling. This molecular remodeling may contribute to the induction of reelin (RELN) and GAD(67) (GAD1) promoter demethylation, and may reverse the downregulation of various GABAergic mRNAs and proteins detected in the telencephalon of patients with schizophrenia or bipolar disorders.

BACKGROUND

A recent genome-wide association study linked a common variant in RELN (rs7341475G) with risk for schizophrenia in women. In the largest neuroimaging intermediate phenotype study reported so far, we evaluated the effect of rs7341475 on an extended array of different neuroscientific measures.

METHODS

Brain structure was evaluated with voxel-based morphometry and diffusion tensor imaging. Brain function during working memory was examined with functional magnetic resonance imaging. The RELN expression was determined in postmortem brain tissue of the dorsolateral prefrontal cortex and hippocampus. A total of 736 datasets were examined (voxel-based morphometry: n = 230, diffusion tensor imaging: n = 93, functional magnetic resonance imaging: n = 308, RELN expression: n = 105).

RESULTS

Our analyses did not provide evidence for a significant main effect of gene or gene x sex interaction effect on any of the examined measures.

CONCLUSIONS

This study does not suggest a significant impact of rs7341475 on brain structure, function, and RELN expression, arguing that this single nucleotide polymorphism and others linked with it do not affect brain measures related to the biology of schizophrenia.

The 22q11.2 microdeletion is one of the highest genetic risk factors for schizophrenia. It is not well understood which interactions of deleted genes in 22q11.2 regions are responsible for the pathogenesis of schizophrenia, but catechol-O-methytransferase (COMT) is among the candidates. Df1/+ mice are 22q11.2 deletion syndrome (22q11DS) model mice with a hemizygous deletion of 18 genes in the 22q11-related region. Df1/+ mice showed enhanced response to the dopamine D1 agonist, SKF38393, and the N-methyl-D-aspartate antagonist, MK801, which can be normalized by a GABA(A) receptor agonist, bretazenil, or a GABA(A) α2/α3 receptor agonist, SL651498. Here, we demonstrated the curing effects of virus-mediated reintroduction of Comt to the prefrontal cortex (PFC) in Df1/+ mice. In contrast, both Comt overexpression and Comt inhibition caused an abnormal responsiveness to Bretazenil, a GABA(A) receptor agonist in control mice. Comt overexpression increased MK801-induced interneuronal activation and GABA release in the PFC. The expression levels of GABA-related genes such as Gabrb2 (GABA(A)receptor β2), Gad2 (glutamic acid decarboxylase 65 (Gad65)) and Reln (Reelin) correlate with a Comt expression level in PFC. Our data suggest that Comt-mediated regulation of GABAergic system might be involved in the behavioral pathogenesis of Df1/+ mice.

The present study genotyped four SNPs (rs736707, rs2229864, rs362691, and rs2073559) of the Reelin gene (RELN) in 165 autistic trios, 67 sporadic autistic children and 283 healthy controls with Chinese Han pedigree. Both case-control analysis and transmission disequilibrium test (TDT) found no evidence of significant association. The results do not support previous positive findings and suggest that the four single-nucleotide polymorphisms (SNP) of RELN are unlikely to be associated with childhood autism in Chinese Han population.

Reelin protein (RELN) level is reduced in the cerebral cortex and cerebellum of subjects with autism. RELN is synthesized and secreted by a subpopulation of neurons in the developing cerebral cortex termed Cajal-Retzius (CR) cells. These cells are abundant in the marginal zone during cortical development, many die after development is complete, but a small population persists into adulthood. In adult brains, RELN is secreted by the surviving CR cells, by a subset of GABAergic interneurons in layer I, and by pyramidal cells and GABAergic interneurons in deeper cortical layers. It is widely believed that decreased RELN in layer I of the cerebral cortex of subjects with autism may result from a decrease in the density of RELN expressing neurons in layer I; however, this hypothesis has not been tested. We examined RELN expression in layer I of the adult human cortex and found that 70% of cells express RELN in both control and autistic subjects. We quantified the density of neurons in layer I of the superior temporal cortex of subjects with autism and age-matched control subjects. Our data show that there is no change in the density of neurons in layer I of the cortex of subjects with autism, and therefore suggest that reduced RELN expression in the cerebral cortex of subjects with autism is not a consequence of decreased numbers of RELN-expressing neurons in layer I. Instead reduced RELN may result from abnormal RELN processing, or a decrease in the number of other RELN-expressing neuronal cell types.

Pontocerebellar hypoplasias (PCH) are characterized by lack of development and/or early neurodegeneration of cerebellum and brainstem. We report five patients referred for PCH, showing atypical clinical and magnetic resonance imaging (MRI) features suggestive of defects in the Reelin pathway. We screened for mutations in RELN or VLDLR and compared the phenotype of these patients with that of previously reported patients. All patients had profound cerebellar hypoplasia on MRI with peculiar cerebellar morphology, associated with flattened pons and neocortical abnormalities. Patient 1 had profound motor and intellectual disability with moderate lissencephaly suggestive of RELN mutations and was shown to harbor a splicing homozygous RELN mutation. The four other patients had a milder phenotype consistent with CARMQ1 (cerebellar ataxia and mental retardation with or without quadrupedal locomotion). These patients showed mild simplification or thickening of cortical gyration and had VLDLR mutations. Reelin signaling regulates neuronal migration in the developing mammalian brain. VLDLR is a key component of the Reelin pathway. Our patients had a very small and dysplatic cerebellar vermis that should suggest the involvement of these genes. Moreover, differences in clinical severity, involvement of the cerebellar hemispheres, together with the severity of the neocortical defect, enables RELN-mutated patients to be distinguished from VLDLR-mutated patients.

Reelin is an extracellular signaling protein that plays an important role in the development of the central nervous system. Post-mortem studies have shown lower reelin protein levels in the brains of patients with schizophrenia and bipolar disorder compared with controls. Genetic studies have also shown that mutations in the reelin gene (RELN) increase the risk for schizophrenia and bipolar disorder. We evaluated whether an RELN gene variant, rs362719, which has been associated with increased susceptibility to bipolar disorder, is also associated with susceptibility to schizophrenia. We included 405 Chinese Han schizophrenia patients and 390 controls in our study. The polymorphism was genotyped by PCR and RFLP methods. We found a significant difference in allele frequency distribution (P< 0.05) between schizophrenia patients and controls. The frequency of the A allele was significantly higher in schizophrenia patients than in healthy controls. The effect of SNP rs362719 on allele distribution was significant in female (P < 0.05) but not in male participants (P = 0.473). Besides the gender factor, demographic and clinical characteristics of the rs362719 genotype groups were also analyzed using the chi-square test, but no significant differences were found. We conclude that rs362719 of the RELN gene is associated with susceptibility to schizophrenia in Chinese Han, possibly through a gender-specific mechanism. Further studies will be needed to confirm this genetic risk factor for schizophrenia.

Reelin, an extracellular protein that signals through the Dab1 adapter protein, and Lis1 regulate neuronal migration and cellular layer formation in the brain. Loss of Reelin and reduction in Lis1 activity in mice or humans results in the disorganization of cortical structures. Lis1, the product of the Pafah1b1 gene associates with Alpha1 (the product of the Pafah1b3 gene) and Alpha2 (the product of the Pafah1b2 gene) to form the Pafah1b heterotrimeric complex. This complex interacts biochemically and genetically with the Reelin pathway, however, the role of Alpha1 and Alpha2 in brain development is poorly understood. We previously demonstrated that compound mutations of Pafah1b1 with genes in Reelin pathway result in layering defects and the appearance of hydrocephalus in double mutant mice. Here, we generate triple mouse mutants to investigate the effect of individual Pafah1b Alpha subunits on cellular layer formation and hydrocephalus. We found that Pafah1b3 mutations exacerbate the layering defects, whereas Pafah1b2 mutations strongly suppress the hydrocephalus phenotype of compound mutant mice. The data indicate that the two Pafah1b Alpha subunits have profoundly different effects on brain development and interact in a significantly different manner with the Reelin signaling pathway.

Executive functions such as set-shifting and maintenance are cognitive processes that rely on complex neurodevelopmental processes. Although neurodevelopmental processes are mainly studied in animal models and in neuropsychiatric disorders, the underlying genetic basis for these processes under physiological conditions is poorly understood. We aimed to investigate the association between genetic variants of the Reelin (RELN) gene and cognitive set-shifting in healthy young individuals. The relationship between 12 selected single nucleotide polymorphisms (SNPs) of the RELN gene and cognitive set-shifting as measured by perseverative errors using the modified card sorting test (MCST) was analysed in a sample of N=98 young healthy individuals (mean age in years: 22.7 ± 0.19). Results show that in individual MANCOVA analyses two of five significant SNPs (rs2711870: F(2,39)=7.14; p=0.0019; rs2249372: F(2,39)=6.97; p=0.002) withstood Bonferroni correction for multiple testing (corrected p-value: p=0.004). While haplotype analyses of the RELN gene showed significant associations between three haplotypes and perseverative error processing in various models of inheritance (adjusted for age, gender, BDI, MWTB IQ), the GCT haplotype showed the most robust finding with a recessive model of inheritance (p=2.32 × 10(-5)) involving the functional SNP rs362691 (Leu-Val amino acid change). Although our study strongly suggests the involvement of the RELN gene in cognitive set-shifting and maintenance, our study requires further exploration as well as replication of the findings in larger samples of healthy individuals and in clinical samples with neuropsychiatric disorders.

BACKGROUND

After neonatal ventral hippocampal lesions (NVHLs), adult rats exhibit evidence of neural processing deficits relevant to schizophrenia, including reduced prepulse inhibition (PPI) of acoustic startle and impaired sensory processing. In intact rats, the regulation of PPI by the ventral hippocampus (VH) is mediated via interactions with medial prefrontal cortex (mPFC) and nucleus accumbens (NAC). We assessed PPI, auditory-evoked responses and expression of 7 schizophrenia-related genes in mPFC and NAC, in adult rats after sham- or real NVHLs.

METHODS

Male inbred Buffalo (BUF) rat pups (d7; n=36) received either vehicle or ibotenic acid infusion into the VH. PPI and auditory-evoked dentate gyrus local field potentials (LFPs) were measured on d56 and d66, respectively. Brains were processed for RT-PCR measures of mPFC and NAC Comt, Erbb4, Grid2, Ncam1, Slc1a2, Nrg1 and Reln.

RESULTS

NVHL rats exhibited significant deficits in PPI (p=0.005) and LFPs (p<0.015) proportional to lesion size. Sham vs. NVHL rats did not differ in gene expression levels in mPFC or NAC. As we previously reported, multiple gene expression levels were highly correlated within- (mean r's≈0.5), but not across-brain regions (mean r's≈0). However, for three genes--Comt, Slc1a2 and Ncam1--after NVHLs, expression levels became significantly correlated, or "coupled," across the mPFC and NAC (p's<0.03, 0.002 and 0.05, respectively), and the degree of "coupling" increased with VH lesion size.

CONCLUSIONS

After NVHLs that disrupt PPI and auditory processing, specific gene expression levels suggest an abnormal functional coupling of the mPFC and NAC. This model of VH-mPFC-NAC network dysfunction after NVHLs may have implications for understanding the neural basis for PPI- and related sensory processing deficits in schizophrenia patients.

Malformations of cortical development (MCD) represent a major cause of developmental disabilities and severe epilepsy. Advances in imaging and genetics have improved the diagnosis and classification of these conditions. Up to now, eight genes have been involved in different types of MCD. Lissencephaly-pachygyria and subcortical band heterotopia (SBH) 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. DCX mutations usually cause anteriorly predominant lissencephaly in males and SBH in female patients. Additional forms are X-linked lissencephaly with corpus callosum agenesis and ambiguous genitalia associated with mutations of the ARX gene. Lissencephaly with cerebellar hypoplasia (LCH) encompass heterogeneous disorders named LCH types a to d. LCHa is related to mutation in LIS1 or DCX, LCHb with mutation of the RELN gene, and LCHd could be related to the TUBA1A gene. Polymicrogyria encompasses a wide range of clinical, etiological, and histological findings. Among several syndromes, recessive bilateral fronto-parietal polymicrogyria has been associated with mutations of the GPR56 gene. Bilateral perisylvian polymicrogyria has been associated with mutations in the SRPX2 gene in a few individuals and with linkage to chromosome Xq28 in a some other families. X-linked bilateral periventricular nodular heterotopia (PNH) consists of PNH with focal epilepsy in females and prenatal lethality in males. Filamin A (FLNA) mutations have been reported in some families and in sporadic patients. It is possible to infer the most likely causative gene by brain imaging studies and other clinical findings.