Variations in genes regulating neuronal migration predict reduced prefrontal cognition in schizophrenia and bipolar subjects from mediterranean Spain: A preliminary study

Clinical analysis of PAFAH1B1 gene variants in pediatric patients with epilepsy

PURPOSE

PAFAH1B1, also known as LIS1, is associated with type I lissencephaly in humans, which is a severe developmental brain disorder believed to result from abnormal neuronal migration. Our objective was to characterize the genotypes and phenotypes of PAFAH1B1-related epilepsy.

METHODS

We conducted a comprehensive analysis of the medical histories, magnetic resonance imaging findings, and video-electroencephalogram recordings of 11 patients with PAFAH1B1 variants at the Neurology Department of Beijing Children's Hospital from June 2017 to November 2022.

RESULTS

The age of onset of epilepsy ranged from 2 months to 4 years, with a median onset age of 5 months. Among these 11 patients (comprising 6 boys and 5 girls), all were diagnosed with lissencephaly type 1. Predominantly, generalized tonic-clonic and spasm seizures characterized PAFAH1B1-related epilepsy. Additionally, 10 out of the 11 patients exhibited severe developmental disorders. All patients exhibited de novo variants, with three individuals displaying 17p13.3 deletions linked to haploinsufficiency of PAFAH1B1. Four variants were previously unreported. Notably, three patients with 17p13.3 deletions displayed developmental delay and drug resistant epilepsy, whereas the single patient with mild developmental delay, Intelligence Quotient (IQ) 57 and well-controlled seizures had a splicing-site variant.

CONCLUSION

The severity of the phenotype in patients with PAFAH1B1 variants ranged from drug-responsive seizures to severe epileptic encephalopathy. These observations underscore the clinical heterogeneity of PAFAH1B1-related disorders, with most patients exhibiting developmental disorders. Moreover, the severity of epilepsy appears to be linked to genetic variations.

Chronic inflammation, neuroglial dysfunction, and plasmalogen deficiency as a new pathobiological hypothesis addressing the overlap between post-COVID-19 symptoms and myalgic encephalomyelitis/chronic fatigue syndrome

After five waves of coronavirus disease 2019 (COVID-19) outbreaks, it has been recognized that a significant portion of the affected individuals developed long-term debilitating symptoms marked by chronic fatigue, cognitive difficulties ("brain fog"), post-exertional malaise, and autonomic dysfunction. The onset, progression, and clinical presentation of this condition, generically named post-COVID-19 syndrome, overlap significantly with another enigmatic condition, referred to as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Several pathobiological mechanisms have been proposed for ME/CFS, including redox imbalance, systemic and central nervous system inflammation, and mitochondrial dysfunction. Chronic inflammation and glial pathological reactivity are common hallmarks of several neurodegenerative and neuropsychiatric disorders and have been consistently associated with reduced central and peripheral levels of plasmalogens, one of the major phospholipid components of cell membranes with several homeostatic functions. Of great interest, recent evidence revealed a significant reduction of plasmalogen contents, biosynthesis, and metabolism in ME/CFS and acute COVID-19, with a strong association to symptom severity and other relevant clinical outcomes. These bioactive lipids have increasingly attracted attention due to their reduced levels representing a common pathophysiological manifestation between several disorders associated with aging and chronic inflammation. However, alterations in plasmalogen levels or their lipidic metabolism have not yet been examined in individuals suffering from post-COVID-19 symptoms. Here, we proposed a pathobiological model for post-COVID-19 and ME/CFS based on their common inflammation and dysfunctional glial reactivity, and highlighted the emerging implications of plasmalogen deficiency in the underlying mechanisms. Along with the promising outcomes of plasmalogen replacement therapy (PRT) for various neurodegenerative/neuropsychiatric disorders, we sought to propose PRT as a simple, effective, and safe strategy for the potential relief of the debilitating symptoms associated with ME/CFS and post-COVID-19 syndrome.

Abnormalities in Cortical GABAergic Interneurons of the Primary Motor Cortex Caused by Lis1 (Pafah1b1) Mutation Produce a Non-drastic Functional Phenotype

LIS1 (PAFAH1B1) plays a major role in the developing cerebral cortex, and haploinsufficient mutations cause human lissencephaly type 1. We have studied morphological and functional properties of the cerebral cortex of mutant mice harboring a deletion in the first exon of the mouse Lis1 (Pafah1b1) gene, which encodes for the LisH domain. The Lis1/sLis1 animals had an overall unaltered cortical structure but showed an abnormal distribution of cortical GABAergic interneurons (those expressing calbindin, calretinin, or parvalbumin), which mainly accumulated in the deep neocortical layers. Interestingly, the study of the oscillatory activity revealed an apparent inability of the cortical circuits to produce correct activity patterns. Moreover, the fast spiking (FS) inhibitory GABAergic interneurons exhibited several abnormalities regarding the size of the action potentials, the threshold for spike firing, the time course of the action potential after-hyperpolarization (AHP), the firing frequency, and the frequency and peak amplitude of spontaneous excitatory postsynaptic currents (sEPSC’s). These morphological and functional alterations in the cortical inhibitory system characterize the Lis1/sLis1 mouse as a model of mild lissencephaly, showing a phenotype less drastic than the typical phenotype attributed to classical lissencephaly. Therefore, the results described in the present manuscript corroborate the idea that mutations in some regions of the Lis1 gene can produce phenotypes more similar to those typically described in schizophrenic and autistic patients and animal models.

Interneuron Heterotopia in the Lis1 Mutant Mouse Cortex Underlies a Structural and Functional Schizophrenia-Like Phenotype

LIS1 is one of the principal genes related to Type I lissencephaly, a severe human brain malformation characterized by an abnormal neuronal migration in the cortex during embryonic development. This is clinically associated with epilepsy and cerebral palsy in severe cases, as well as a predisposition to developing mental disorders, in cases with a mild phenotype. Although genetic variations in the LIS1 gene have been associated with the development of schizophrenia, little is known about the underlying neurobiological mechanisms. We have studied how the Lis1 gene might cause deficits associated with the pathophysiology of schizophrenia using the Lis1/sLis1 murine model, which involves the deletion of the first coding exon of the Lis1 gene. Homozygous mice are not viable, but heterozygous animals present abnormal neuronal morphology, cortical dysplasia, and enhanced cortical excitability. We have observed reduced number of cells expressing GABA-synthesizing enzyme glutamic acid decarboxylase 67 (GAD67) in the hippocampus and the anterior cingulate area, as well as fewer parvalbumin-expressing cells in the anterior cingulate cortex in Lis1/sLis1 mutants compared to control mice. The cFOS protein expression (indicative of neuronal activity) in Lis1/sLis1 mice was higher in the medial prefrontal (mPFC), perirhinal (PERI), entorhinal (ENT), ectorhinal (ECT) cortices, and hippocampus compared to control mice. Our results suggest that deleting the first coding exon of the Lis1 gene might cause cortical anomalies associated with the pathophysiology of schizophrenia.

Clinical Phenotypes Associated to Engrailed 2 Gene Alterations in a Series of Neuropediatric Patients

The engrailed homeobox protein (EN) plays an important role in the regionalization of the neural tube. EN distribution regulates the cerebellum and midbrain morphogenesis, as well as retinotectal synaptogenesis. In humans, the EN1 and EN2 genes code for the EN family of transcription factors. Genetic alterations in the expression of EN2 have been related to different neurologic conditions and more particularly to autism spectrum disorders (ASD). We aimed to study and compare the phenotypes of three series of patients: (1) patients with encephalic structural anomalies (ESA) and abnormalities in the genomic (DNA) and/or transcriptomic (RNAm) of EN2 (EN2-g), (2) ESA patients having other gene mutations (OG-g), and (3) ESA patients free of these mutations (NM-g).

Subjects and Methods: We have performed a descriptive study on 109 patients who suffer from mental retardation (MR), cerebral palsy (CP), epilepsy (EP), and behavioral disorders (BD), showing also ESA in their encephalic MRI. We studied genomic DNA and transcriptional analysis (cDNA) on EN2 gene (EN2), and in other genes (OG): LIS1, PTAFR, PAFAH1B2, PAFAH1B3, FGF8, PAX2, D17S379, D17S1866, and SMG6 (D17S5), as a routine genetic diagnosis in ESA patients.

Results: From 109 patients, fifteen meet the exclusion criteria. From the remaining 94 patients, 12 (12.8%) showed mutations in EN2 (EN2-g), 20 showed mutations in other studied genes (OG-g), and 62 did not showed any mutation (NM-g). All EN2-g patients, suffered from MR, nine EP, seven BD and four CP. The proportions of these phenotypes in EN2-g did not differ from those in the OG-g, but it was significantly higher when comparing EN2-g with NM-g (MR: p = 0.013; EP: p = 0.001; BD: p = 0.0001; CP: p = 0.07, ns). Groups EN2-g and OG-g showed a 100 and a 70% of comorbidity, respectively, being significantly (p = 0.04) greater than NM-group (62.9%).

Conclusion: Our series reflects a significant effect of EN2 gene alterations in neurodevelopmental abnormalities associated to ESA. Conversely, although these EN2 related anomalies might represent a predisposition to develop brain diseases, our results did not support direct relationship between EN2 mutations and specific clinical phenotypes.

Primary Cilia as a Possible Link between Left-Right Asymmetry and Neurodevelopmental Diseases

Cilia have multiple functions in the development of the entire organism, and participate in the development and functioning of the central nervous system. In the last decade, studies have shown that they are implicated in the development of the visceral left-right asymmetry in different vertebrates. At the same time, some neuropsychiatric disorders, such as schizophrenia, autism, bipolar disorder, and dyslexia, are known to be associated with lateralization failure. In this review, we consider possible links in the mechanisms of determination of visceral asymmetry and brain lateralization, through cilia. We review the functions of seven genes associated with both cilia, and with neurodevelopmental diseases, keeping in mind their possible role in the establishment of the left-right brain asymmetry.

The dysregulated brain: consequences of spatial and temporal brain complexity for bipolar disorder pathophysiology and diagnosis

Increasingly, evidence has been accumulating emphasizing the importance of looking at bipolar disorder (BD) from a neurodevelopmental and transdimensional perspective to better understand its origins and its course. In this overview article, the problems facing pathophysiological psychiatric research in BD are addressed and interpreted in the light of brain complexity. Brain complexity can be split into spatial complexity, which constitutes the physiological levels of the central nervous system (i.e., the genetic, molecular, cellular, neuronal circuit and phenomenological levels), and temporal complexity, that is, neurodevelopment. The consequences of this consideration are discussed and suggestions for clinical practice and pathophysiological psychiatric research are made.

Neurodevelopmental origins of bipolar disorder: iPSC models

Bipolar disorder (BP) is a chronic neuropsychiatric condition characterized by pathological fluctuations in mood from mania to depression. Adoption, twin and family studies have consistently identified a significant hereditary component to BP, yet there is no clear genetic event or consistent neuropathology. BP has been suggested to have a developmental origin, although this hypothesis has been difficult to test since there are no viable neurons or glial cells to analyze, and research has relied largely on postmortem brain, behavioral and imaging studies, or has examined proxy tissues including saliva, olfactory epithelium and blood cells. Neurodevelopmental factors, particularly pathways related to nervous system development, cell migration, extracellular matrix, H3K4 methylation, and calcium signaling have been identified in large gene expression and GWAS studies as altered in BP. Recent advances in stem cell biology, particularly the ability to reprogram adult somatic tissues to a pluripotent state, now make it possible to interrogate these pathways in viable cell models. A number of induced pluripotent stem cell (iPSC) lines from BP patient and healthy control (C) individuals have been derived in several laboratories, and their ability to form cortical neurons examined. Early studies suggest differences in activity, calcium signaling, blocks to neuronal differentiation, and changes in neuronal, and possibly glial, lineage specification. Initial observations suggest that differentiation of BP patient-derived neurons to dorsal telencephalic derivatives may be impaired, possibly due to alterations in WNT, Hedgehog or Nodal pathway signaling. These investigations strongly support a developmental contribution to BP and identify novel pathways, mechanisms and opportunities for improved treatments.

The clinical implications of cognitive impairment and allostatic load in bipolar disorder

BACKGROUND

Allostatic load (AL) relates to the neural and bodily "wear and tear" that emerge in the context of chronic stress. This paper aims to provide clinicians with a comprehensive overview of the role of AL in patophysiology of bipolar disorder (BD) and its practical implications.

METHODS

PubMed searches were conducted on English-language articles published from 1970 to June 2011 using the search terms allostatic load, oxidative stress, staging, and bipolar disorder cross-referenced with cognitive impairment, comorbidity, mediators, prevention.

RESULTS

Progressive neural and physical dysfunction consequent to mood episodes in BD can be construed as a cumulative state of AL. The concept of AL can help to reconcile cognitive impairment and increased rates of clinical comorbidities that occur over the course of cumulative BD episodes.

CONCLUSIONS

Data on transduction of psychosocial stress into the neurobiology of mood episodes converges to the concept of AL. Mood episodes prevention would not only alleviate emotional suffering, but also arrest the cycle of AL, cognitive decline, physical morbidities and, eventually, related mortality. These objectives can be achieved by focusing on effective prophylaxis from the first stages of the disorder, providing mood-stabilizing agents and standardized psychoeducation and, potentially, addressing cognitive deficits by the means of specific medication and neuropsychological interventions.

Neurocognitive impairment across the bipolar spectrum

Bipolar disorder is a severe mental illness that affects nearly 4.4% of the general population when bipolar spectrum disorders are taken into account. Neurocognitive impairment is thought to be a core deficit of this illness since it is present during euthymia. In fact, 40-60% of euthymic patients present with neurocognitive disturbances. Not only the clinical factors but also disturbances in neurocognition can influence the functional outcome of BD patients. Hence, further research is needed in order to clarify the relationship between these variables. Despite the growing body of evidence that has emerged during the last decade, no unique neurocognitive profile has been proposed yet for either BD subtype. The majority of the studies recluted heterogeneous samples (including both bipolar I and II) or focused on BD-I patients only. The aim of this review is to give an overall picture of the main neurocognitive disturbances found in the bipolar spectrum and particularly in BD-II, where the findings are more ambiguous. An extensive review of all the literature has been done regarding this subtype (from 1980 until July 2009). Data available until now suggest that deficits are present across the bipolar spectrum (BD-I and BD-II), but they seem slightly more severe in BD-I. The extent to which either subtype share-or not-some similarities is still unknown. More studies are required but it would also be interesting to reach a consensus in the neuropsychological assessment of BD to facilitate comparisons between the different studies.

Bipolar disorder and dementia: where is the link?

Cognitive disorders appearing in the course of bipolar disease have been identified, and recent studies have defined the neuropsychological characteristics of this pathology, which includes attention, executive function, memory and language disorders. However, questions remain concerning the appearance of dementia symptoms over the course of bipolar disorder in certain patients: is it a chance association or is there a connection between bipolar disorders and dementia? If the latter hypothesis is considered, what is the nature of the dementia, which might be considered as a dementia specific to bipolar disorder? Current clinical, neuropsychological and cerebral imaging data are inconclusive, but similarities with frontotemporal dementia might be highlighted. Functional imaging studies might provide answers as well as more specific tests in neuropsychology. The cause of cognitive damage in bipolar disease also raises questions concerning a neurodevelopmental or neurodegenerative process, because several factors seem to influence cognition and these two processes might occur simultaneously. Long-term studies are necessary to determine whether cognitive deterioration in bipolar disease is stable or progressive. There might also be different neurobiological subgroups of patients with bipolar disease.

A 2-year naturalistic study on cognitive functioning in bipolar disorder

OBJECTIVE

Cognitive alterations in bipolar disorder may reflect genetic influence. However, to what degree mood, medication, thyroid function and other factors impact on longitudinal cognitive functioning remains unclear.

METHOD

A group of patients with bipolar (spectrum) disorder (n = 76) underwent two monthly cognitive assessments over a 2-year period in a prospective, repeated measures design. Regression models were used to investigate associations with predictors, corrected for multiple testing.

RESULTS

Patients with bipolar disorder performed worse than healthy controls (n = 61) on all cognitive domains tested. Effect sizes were small, with a maximum of -0.36 for sustained attention. However, cognitive performance varied substantially over the 2-year follow-up, co-varying with subjective cognitive complaints and impacting on functioning. Alterations in sustained attention and motor speed were the only impairments that were invariant over time. Predictors had very limited explanatory power on temporal variation in cognition. Use of second-generation antipsychotics was associated with the largest negative effects on cognition, which were evident in the areas of motor speed and basic information processing (-0.35 < β < -0.5).

CONCLUSION

Cognitive function in bipolar disorder varies significantly over time, largely independent of clinical factors. The temporal stability of sustained attention is the exception, suggesting it may represent a possible candidate intermediary phenotype.

Chromosome 8p as a potential hub for developmental neuropsychiatric disorders: implications for schizophrenia, autism and cancer

Defects in genetic and developmental processes are thought to contribute susceptibility to autism and schizophrenia. Presumably, owing to etiological complexity identifying susceptibility genes and abnormalities in the development has been difficult. However, the importance of genes within chromosomal 8p region for neuropsychiatric disorders and cancer is well established. There are 484 annotated genes located on 8p; many are most likely oncogenes and tumor-suppressor genes. Molecular genetics and developmental studies have identified 21 genes in this region (ADRA1A, ARHGEF10, CHRNA2, CHRNA6, CHRNB3, DKK4, DPYSL2, EGR3, FGF17, FGF20, FGFR1, FZD3, LDL, NAT2, NEF3, NRG1, PCM1, PLAT, PPP3CC, SFRP1 and VMAT1/SLC18A1) that are most likely to contribute to neuropsychiatric disorders (schizophrenia, autism, bipolar disorder and depression), neurodegenerative disorders (Parkinson's and Alzheimer's disease) and cancer. Furthermore, at least seven nonprotein-coding RNAs (microRNAs) are located at 8p. Structural variants on 8p, such as copy number variants, microdeletions or microduplications, might also contribute to autism, schizophrenia and other human diseases including cancer. In this review, we consider the current state of evidence from cytogenetic, linkage, association, gene expression and endophenotyping studies for the role of these 8p genes in neuropsychiatric disease. We also describe how a mutation in an 8p gene (Fgf17) results in a mouse with deficits in specific components of social behavior and a reduction in its dorsomedial prefrontal cortex. We finish by discussing the biological connections of 8p with respect to neuropsychiatric disorders and cancer, despite the shortcomings of this evidence.

Relationship between psychosocial adjustment and executive function in patients with bipolar disorder and schizophrenia in remission: the mediating and moderating effects of insight

OBJECTIVES

The aims of this study were to examine the relationships between executive function and psychosocial adjustment, and the mediating and moderating effects of insight on the association between executive function and psychosocial adjustment in patients with bipolar disorder and schizophrenia in clinical remission.

METHODS

The level of psychosocial adjustment was assessed in 96 subjects with bipolar disorder and 96 subjects with schizophrenia who were in remitted state. The association between executive function and psychosocial adjustment and the mediating and moderating effects of insight were examined by multiple regression analysis models and the Goodman test.

RESULTS

The results indicated that executive function had direct effect on psychosocial adjustment in both subjects with bipolar disorder and schizophrenia. However, the mediating effect of insight on the association between executive function and psychosocial adjustment was only found in subjects with schizophrenia, but not in subjects with bipolar disorder. No moderating effect of insight on the association between executive function and psychosocial adjustment was found in subjects with schizophrenia or bipolar disorder.

CONCLUSIONS

The results of this study indicated that executive function has an important role in psychosocial adjustment in both patients with bipolar disorder and schizophrenia. Meanwhile, insight has a different role in the association between executive function and psychosocial adjustment between patients with bipolar disorder and schizophrenia.

Neuropsychological profile in bipolar disorder: a preliminary study of monotherapy lithium-treated euthymic bipolar patients evaluated at a 2-year interval

OBJECTIVE

To investigate the cognitive impairment of a sample of euthymic bipolar patients treated with lithium monotherapy at baseline in a 2-year longitudinal study.

METHOD

Fifteen DSM-IV-TR bipolar out-patients and 15 healthy-matched controls were cognitively assessed twice over a 2-year follow-up. All patients underwent lithium monotherapy on the first evaluation, and they were euthymic in both evaluations. Cognitive assessment was performed by means of a neuropsychological test battery tapping into the main cognitive domains (executive function, attention, processing speed, verbal memory and visual memory).

RESULTS

Repeated measures multivariate analysis of variance showed that the bipolar disorder group was cognitively impaired in the executive domain, attention and processing speed, and such deficits were maintained over time.

CONCLUSION

Our results showed that executive dysfunction is the main long-term neuropsychological deficit of bipolar disorder. Also, the persistence of these deficits did not seem to be influenced by any clinical or pharmacological variables.

Longitudinal brain changes in early-onset psychosis

Progressive losses of cortical gray matter volumes and increases in ventricular volumes have been reported in patients with childhood-onset schizophrenia (COS) during adolescence. Longitudinal studies suggest that the rate of cortical loss seen in COS during adolescence plateaus during early adulthood. Patients with first-episode adolescent-onset schizophrenia show less marked progressive changes, although the number of studies in this population is small. Some studies show that, although less exaggerated, progressive changes are also present in nonschizophrenia early-onset psychosis. The greater loss of brain tissue seen in COS, even some years after the first episode, as compared to adolescent- or adult-onset schizophrenia may be due to variables such as sample bias (more severe, treatment refractory sample of childhood-onset patients studied), a process uniquely related to adolescent development in COS, differential brain effects of drug treatment in this population, clinical outcome, or interactions among these variables. Findings from both cross-sectional studies of first-episode patients and longitudinal studies in COS and adolescent onset support the concept of early-onset schizophrenia as a progressive neurodevelopmental disorder with both early and late developmental abnormalities. Future studies should look for correlates at a cellular level and for pathophysiological explanations of volume changes in these populations. The association of risk genes involved in circuitries associated with schizophrenia and their relationship to developmental trajectories is another promising area of future research.

Prenatal ultrasound scanning and the risk of schizophrenia and other psychoses

BACKGROUND

Prenatal ultrasound exposure has been associated with increased prevalence of left-hand or mixed-hand preference, and has been suggested to affect the normal lateralization of the fetal brain. Atypical lateralization is more common in patients with schizophrenia. We evaluated possible associations of prenatal ultrasound with schizophrenia and other psychoses.

METHODS

We identified a cohort of individuals born in Sweden 1973-1978. During this period, one Swedish hospital (Malmö University Hospital) performed prenatal ultrasound on a routine basis, and all individuals born at that hospital were considered exposed to ultrasound. Children born at hospitals where ultrasound was not used routinely or selectively were considered unexposed. We used Poisson regression analysis to estimate the effect of ultrasound exposure on the incidence of schizophrenia and other psychoses.

RESULTS

In all, 370,945 individuals were included in the study, of whom 13,212 were exposed to ultrasound. The exposed group demonstrated a tendency toward a higher risk of schizophrenia (among men, crude incidence rate ratio = 1.58 [95% confidence interval = 0.99-2.51]; among women, 1.26 [0.62-2.55]). However, men and women born in several of the 7 tertiary level hospitals without ultrasound scanning also had higher risks of schizophrenia compared with those born in other hospitals. For other psychoses there were no differences between groups.

CONCLUSIONS

No clear associations between prenatal ultrasound exposure and schizophrenia or other psychoses were found. Other factors related to place of birth might have influenced the results.

Lissencephaly 1 linking to multiple diseases: mental retardation, neurodegeneration, schizophrenia, male sterility, and more

Lissencephaly 1 (LIS1) was the first gene implicated in the pathogenesis of type-1 lissencephaly. More than a decade of research by multiple laboratories has revealed that LIS1 is a key node protein, which participates in several pathways, including association with the molecular motor cytoplasmic dynein, the reelin signaling pathway, and the platelet-activating factor pathway. Mutations in LIS1-interacting proteins, either in human, or in mouse models has suggested that LIS1 might play a role in the pathogenesis of numerous diseases such as male sterility, schizophrenia, neuronal degeneration, and viral infections.

The DISC locus in psychiatric illness

The DISC locus is located at the breakpoint of a balanced t(1;11) chromosomal translocation in a large and unique Scottish family. This translocation segregates in a highly statistically significant manner with a broad diagnosis of psychiatric illness, including schizophrenia, bipolar disorder and major depression, as well as with a narrow diagnosis of schizophrenia alone. Two novel genes were identified at this locus and due to the high prevalence of schizophrenia in this family, they were named Disrupted-in-Schizophrenia-1 (DISC1) and Disrupted-in-Schizophrenia-2 (DISC2). DISC1 encodes a novel multifunctional scaffold protein, whereas DISC2 is a putative noncoding RNA gene antisense to DISC1. A number of independent genetic linkage and association studies in diverse populations support the original linkage findings in the Scottish family and genetic evidence now implicates the DISC locus in susceptibility to schizophrenia, schizoaffective disorder, bipolar disorder and major depression as well as various cognitive traits. Despite this, with the exception of the t(1;11) translocation, robust evidence for a functional variant(s) is still lacking and genetic heterogeneity is likely. Of the two genes identified at this locus, DISC1 has been prioritized as the most probable candidate susceptibility gene for psychiatric illness, as its protein sequence is directly disrupted by the translocation. Much research has been undertaken in recent years to elucidate the biological functions of the DISC1 protein and to further our understanding of how it contributes to the pathogenesis of schizophrenia. These data are the main subject of this review; however, the potential involvement of DISC2 in the pathogenesis of psychiatric illness is also discussed. A detailed picture of DISC1 function is now emerging, which encompasses roles in neurodevelopment, cytoskeletal function and cAMP signalling, and several DISC1 interactors have also been defined as independent genetic susceptibility factors for psychiatric illness. DISC1 is a hub protein in a multidimensional risk pathway for major mental illness, and studies of this pathway are opening up opportunities for a better understanding of causality and possible mechanisms of intervention.

Cognitive impairment in schizoaffective disorder: a comparison with non-psychotic bipolar and healthy subjects

OBJECTIVE

Only a few studies have examined specifically the neuropsychological performance of schizoaffective patients.

METHOD

The sample consisted of 34 euthymic DSM-IV schizoaffective patients, who were compared with 41 euthymic bipolar patients without history of psychotic symptoms and 35 healthy controls. Euthymia was defined by a score of 6 or less at the Young Mania Rating Scale and a score of 8 or less at the Hamilton Depression Rating Scale for at least 6 months. Patients were compared with several clinical, occupational, and neuropsychological variables such as executive function, attention, verbal and visual memory and the two groups were contrasted with 35 healthy controls on cognitive performance. The three groups were compared using mancova after checking the potential role of several co-variables.

RESULTS

Schizoaffective patients showed greater impairment than controls and bipolar patients, in several domains, including verbal memory, executive function, and attentional measures. Bipolar patients without history of psychosis performed similar to the controls except for verbal fluency.

CONCLUSION

Schizoaffective disorder carries more neurocognitive impairment than non-psychotic bipolar disorder and more occupational difficulties.

Developmental mechanisms and experimental models to understand forebrain malformative diseases

The development of the central nervous system can be divided into a number of phases, each of which can be subject of genetic or epigenetic alterations that may originate particular developmental disorders. In recent years, much progress has been made in elucidating the molecular and cellular mechanisms by which the vertebrate forebrain develops. Therefore, our understanding of major developmental brain disorders such as cortical malformations and neuronal migration disorders has significantly increased. In this review, we will describe the major stages in forebrain morphogenesis and regionalization, with special emphasis on developmental molecular mechanisms derailing telencephalic development with subsequent damage to cortical function. Because animal models, mainly mouse, have been fundamental for this progress, we will also describe some characteristic mouse models that have been capital to explore these molecular mechanisms of malformative diseases of the human brain. Although most of the genes involved in the regulation of basic developmental processes are conserved among vertebrates, the extrapolation of mouse data to corresponding gene expression and function in humans needs careful individual analysis in each functional system.

Neuroanatomical phenotypes in the reeler mouse

The reeler mouse (Reln) has been proposed as a neurodevelopmental model for certain neurological and psychiatric conditions and has been studied by qualitative histochemistry and electron microscopy. Using magnetic resonance microscopy (MRM), we have quantitated for the first time the neuromorphology of Reln mice at a resolution of 21.5 microm. The neuroanatomical phenotypes of heterozygous and homozygous mutant Reln mice were compared to those of wild type (WT) littermates using morphometry and texture analysis. The cortical, hippocampal, and cerebellar phenotypes of the heterozygous and homozygous mutant Reln mice were confirmed, and new features were revealed. The Reln(rl/rl) mice possessed a smaller brain, and both Reln(rl/+) and Reln(rl/rl) mice had increased ventricles compared to WT controls. Shape differences were found between WT and Reln(rl/rl) brains, specifically in cerebellum, olfactory bulbs, dorsomedial frontal and parietal cortex, certain regions of temporal and occipital lobes, as well as in the lateral ventricles and ventral hippocampus. These findings suggest that certain brain regions may be more severely impacted by the Reln mutation than others. Gadolinium-based active staining demonstrated that layers of the hippocampus were disorganized in Reln(rl/rl) mice and differences in thickness of these layers were identified between WT and Reln(rl/rl) mice. The intensity distributions characteristic to the dorsal, middle, and ventral hippocampus were altered in the Reln(rl/rl), especially in the ventral hippocampus. These differences were quantified using skewness and modeling the intensity distributions with a Gaussian mixture. Our results suggest that structural features of Reln(rl/rl) brain most closely phenocopy those of patients with Norman-Roberts lissencephaly.