Recent studies indicate that long interspersed nuclear element-1 (L1) are mobilized in the genome of human neural progenitor cells and enhanced in Rett syndrome and ataxia telangiectasia. However, whether aberrant L1 retrotransposition occurs in mental disorders is unknown. Here, we report high L1 copy number in schizophrenia. Increased L1 was demonstrated in neurons from prefrontal cortex of patients and in induced pluripotent stem (iPS) cell-derived neurons containing 22q11 deletions. Whole-genome sequencing revealed brain-specific L1 insertion in patients localized preferentially to synapse-and schizophrenia-related genes. To study the mechanism of L1 transposition, we examined perinatal environmental risk factors for schizophrenia in animal models and observed an increased L1 copy number after immune activation by poly-I:C or epidermal growth factor. These findings suggest that hyperactive retrotransposition of L1 in neurons triggered by environmental and/or genetic risk factors may contribute to the susceptibility and pathophysiology of schizophrenia.

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Given the complexity and heterogeneity of the genomic architecture underlying schizophrenia, molecular analyses of these patients with defined and large effect-size genomic defects could provide valuable clues. We established human-induced pluripotent stem cells from two schizophrenia patients with the 22q11.2 deletion (two cell lines from each subject, total of four cell lines) and three controls (total of four cell lines). Neurosphere size, neural differentiation efficiency, neurite outgrowth, cellular migration and the neurogenic-to-gliogenic competence ratio were significantly reduced in patient-derived cells. As an underlying mechanism, we focused on the role of DGCR8, a key gene for microRNA (miRNA) processing and mapped in the deleted region. In mice, Dgcr8 hetero-knockout is known to show a similar phenotype of reduced neurosphere size (Ouchi et al., 2013). The miRNA profiling detected reduced expression levels of miRNAs belonging to miR-17/92 cluster and miR-106a/b in the patient-derived neurospheres. Those miRNAs are reported to target p38α, and conformingly the levels of p38α were upregulated in the patient-derived cells. p38α is known to drive gliogenic differentiation. The inhibition of p38 activity by SB203580 in patient-derived neurospheres partially restored neurogenic competence. Furthermore, we detected elevated expression of GFAP, a gliogenic (astrocyte) marker, in postmortem brains from schizophrenia patients without the 22q11.2 deletion, whereas inflammation markers (IL1B and IL6) remained unchanged. In contrast, a neuronal marker, MAP2 expressions were decreased in schizophrenia brains. These results suggest that a dysregulated balance of neurogenic-to-gliogenic competence may underlie neurodevelopmental disorders such as schizophrenia.

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Disturbances of lipid metabolism have been implicated in psychiatric illnesses. We previously reported an association between the gene for fatty acid binding protein 7 (FABP7) and schizophrenia. Furthermore, we identified and reported several rare non-synonymous polymorphisms of the brain-expressed genes FABP3, FABP5 and FABP7 from schizophrenia and autism spectrum disorder (ASD), diseases known to part share genetic architecture. Here, we conducted further studies to better understand the contribution these genes make to the pathogenesis of schizophrenia and ASD. In postmortem brains, we detected altered mRNA expression levels of FABP5 in schizophrenia, and of FABP7 in ASD and altered FABP5 in peripheral lymphocytes. Using a patient cohort, comprehensive mutation screening identified six missense and two frameshift variants from the three FABP genes. The two frameshift proteins, FABP3 E132fs and FABP7 N80fs, formed cellular aggregates and were unstable when expressed in cultured cells. The four missense mutants with predicted possible damaging outcomes showed no changes in intracellular localization. Examining ligand binding properties, FABP7 S86G and FABP7 V126L lost their preference for docosahexaenoic acid to linoleic acid. Finally, mice deficient in Fabp3, Fabp5 and Fabp7 were evaluated in a systematic behavioral test battery. The Fabp3 knockout (KO) mice showed decreased social memory and novelty seeking, and Fabp7 KO mice displayed hyperactive and anxiety-related phenotypes, while Fabp5 KO mice showed no apparent phenotypes. In conclusion, disturbances in brain-expressed FABPs could represent an underlying disease mechanism in a proportion of schizophrenia and ASD sufferers.

SummaryModeling of neurological diseases using induced pluripotent stem cells (iPSCs) derived from the somatic cells of patients has provided a means of elucidating pathogenic mechanisms and performing drug screening. T cells are an ideal source of patient-specific iPSCs because they can be easily obtained from samples. Recent studies indicated that iPSCs retain an epigenetic memory relating to their cell of origin that restricts their differentiation potential. The classical method of differentiation via embryoid body formation was not suitable for T cell-derived iPSCs (TiPSCs). We developed a neurosphere-based robust differentiation protocol, which enabled TiPSCs to differentiate into functional neurons, despite differences in global gene expression between TiPSCs and adult human dermal fibroblast-derived iPSCs. Furthermore, neurons derived from TiPSCs generated from a juvenile patient with Parkinson's disease exhibited several Parkinson's disease phenotypes. Therefore, we conclude that TiPSCs are a useful tool for modeling neurological diseases.

The neural cell recognition molecule NB-3, also referred to as contactin-6, is expressed prominently in the developing nervous system after birth and its deficiency has been shown to cause impairment in motor coordination. Here, we investigated the contribution of NB-3 to cerebellar development, focusing on lobule 3 where NB-3 was expressed in granule cells but not in Purkinje cells. In the developing molecular layer, the neural cell recognition molecules TAG-1, L1, and NB-3 formed distinct expression zones from the external granule cell layer to the internal granule cell layer (IGL), respectively. The NB-3-immunoreactive zone did not overlap with TAG-1-immunoreactive zone. By contrast, the L1-immunoreactive zone overlapped with both the TAG-1- and NB-3-immunoreactive zones. NB-3-positive puncta overlapped with vesicular glutamate transporter 1, a presynaptic marker and were apposed close to metabotropic glutamate receptor 1A, a postsynaptic marker, indicating that NB-3 is localized presynaptically at glutamatergic synapses between parallel fibers and Purkinje cells. In NB-3 knockout mice, L1 immunoreactive signals were increased in the IGL at postnatal day (P) 5, suggesting the increase in the number of immature granule cells of the IGL. In addition, the density of parallel fiber synaptic terminals was reduced in NB-3 knockout mice relative to wild-type mice at P5 to P10. In parallel with these findings, caspase-dependent cell death was significantly increased in the NB- 3-deficient cerebellum at P15. Collectively, our results indicate that NB-3 deficiency affects synapse formation during postnatal cerebellar development.

BackgroundTo ensure reliable sources of energy and raw materials, the utilization of sustainable biomass has considerable advantages over petroleum-based energy sources. Photosynthetic algae have attracted attention as a third-generation feedstock for biofuel production, because algae cultivation does not directly compete with agricultural resources, including the requirement for productive land and fresh water. In particular, cyanobacteria are a promising biomass feedstock because of their high photosynthetic capability.ResultsIn the present study, the expression of the flv3 gene, which encodes a flavodiiron protein involved in alternative electron flow (AEF) associated with NADPH-coupled O2 photoreduction in photosystem I, was enhanced in Synechocystis sp. PCC6803. Overexpression of flv3 improved cell growth with corresponding increases in O2 evolution, intracellular ATP level, and turnover of the Calvin cycle. The combination of in vivo13C-labeling of metabolites and metabolomic analysis confirmed that the photosynthetic carbon flow was enhanced in the flv3-overexpressing strain.ConclusionsOverexpression of flv3 improved cell growth and glycogen production in the recombinant Synechocystis sp. PCC6803. Direct measurement of metabolic turnover provided conclusive evidence that CO2 incorporation is enhanced by the flv3 overexpression. Increase in O2 evolution and ATP accumulation indicates enhancement of the AEF. Overexpression of flv3 improves photosynthesis in the Synechocystis sp. PCC6803 by enhancement of the AEF.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-014-0183-x) contains supplementary material, which is available to authorized users.