A loss-of-function variant in SUV39H2 identified in autism-spectrum disorder causes altered H3K9 trimethylation and dysregulation of protocadherin ß-cluster genes in the developing brain.

Recent evidence has documented the potential roles of histone-modifying enzymes in autism-spectrum disorder (ASD). Aberrant histone H3 lysine 9 (H3K9) dimethylation resulting from genetic variants in histone methyltransferases is known for neurodevelopmental and behavioral anomalies. However, a systematic examination of H3K9 methylation dynamics in ASD is lacking. Here we resequenced nine genes for histone methyltransferases and demethylases involved in H3K9 methylation in individuals with ASD and healthy controls using targeted next-generation sequencing. We identified a novel rare variant (A211S) in the SUV39H2, which was predicted to be deleterious. The variant showed strongly reduced histone methyltransferase activity in vitro. In silico analysis showed that the variant destabilizes the hydrophobic core and allosterically affects the enzyme activity. The Suv39h2-KO mice displayed hyperactivity and reduced behavioral flexibility in learning the tasks that required complex behavioral adaptation, which is relevant for ASD. The Suv39h2 deficit evoked an elevated expression of a subset of protocadherin ß (Pcdhb) cluster genes in the embryonic brain, which is attributable to the loss of H3K9 trimethylation (me3) at the gene promoters. Reduced H3K9me3 persisted in the cerebellum of Suv39h2-deficient mice to an adult stage. Congruently, reduced expression of SUV39H1 and SUV39H2 in the postmortem brain samples of ASD individuals was observed, underscoring the role of H3K9me3 deficiency in ASD etiology. The present study provides direct evidence for the role of SUV39H2 in ASD and suggests a molecular cascade of SUV39H2 dysfunction leading to H3K9me3 deficiency followed by an untimely, elevated expression of Pcdhb cluster genes during early neurodevelopment.

Cooperation of LIM domain-binding 2 (LDB2) with EGR in the pathogenesis of schizophrenia.

Genomic defects with large effect size can help elucidate unknown pathologic architecture of mental disorders. We previously reported on a patient with schizophrenia and a balanced translocation between chromosomes 4 and 13 and found that the breakpoint within chromosome 4 is located near the LDB2 gene. We show here that Ldb2 knockout (KO) mice displayed multiple deficits relevant to mental disorders. In particular, Ldb2 KO mice exhibited deficits in the fear-conditioning paradigm. Analysis of the amygdala suggested that dysregulation of synaptic activities controlled by the immediate early gene Arc is involved in the phenotypes. We show that LDB2 forms protein complexes with known transcription factors. Consistently, ChIP-seq analyses indicated that LDB2 binds to > 10,000 genomic sites in human neurospheres. We found that many of those sites, including the promoter region of ARC, are occupied by EGR transcription factors. Our previous study showed an association of the EGR family genes with schizophrenia. Collectively, the findings suggest that dysregulation in the gene expression controlled by the LDB2-EGR axis underlies a pathogenesis of subset of mental disorders.

Role of an Atypical Cadherin Gene, Cdh23 in Prepulse Inhibition, and Implication of CDH23 in Schizophrenia.

We previously identified quantitative trait loci (QTL) for prepulse inhibition (PPI), an endophenotype of schizophrenia, on mouse chromosome 10 and reported Fabp7 as a candidate gene from an analysis of F2 mice from inbred strains with high (C57BL/6N; B6) and low (C3H/HeN; C3H) PPI levels. Here, we reanalyzed the previously reported QTLs with increased marker density. The highest logarithm of odds score (26.66) peaked at a synonymous coding and splice-site variant, c.753G>A (rs257098870), in the Cdh23 gene on chromosome 10; the c.753G (C3H) allele showed a PPI-lowering effect. Bayesian multiple QTL mapping also supported the same variant with a posterior probability of 1. Thus, we engineered the c.753G (C3H) allele into the B6 genetic background, which led to dampened PPI. We also revealed an e-QTL (expression QTL) effect imparted by the c.753G>A variant for the Cdh23 expression in the brain. In a human study, a homologous variant (c.753G>A; rs769896655) in CDH23 showed a nominally significant enrichment in individuals with schizophrenia. We also identified multiple potentially deleterious CDH23 variants in individuals with schizophrenia. Collectively, the present study reveals a PPI-regulating Cdh23 variant and a possible contribution of CDH23 to schizophrenia susceptibility.

Lipid Pathology of the Corpus Callosum in Schizophrenia and the Potential Role of Abnormal Gene Regulatory Networks with Reduced Microglial Marker Expression.

Structural changes in the corpus callosum have been reported in schizophrenia; however, the underlying molecular mechanism remains unclear. As the corpus callosum is high in lipid content, we analyzed the lipid contents of the corpora callosa from 15 patients with schizophrenia and 15 age- and sex-matched controls using liquid chromatography coupled to tandem mass spectrometry and identified lipid combinations associated with schizophrenia. Real-time quantitative polymerase chain reaction analyses using extended samples (schizophrenia, n = 95; control, n = 91) showed low expression levels of lipid metabolism-related genes and their potential upstream transcription factors in schizophrenia. Subsequent pathway analysis identified a gene regulatory network where nuclear factor of activated T cells 2 (NFATC2) is placed most upstream. We also observed low gene expression levels of microglial markers, inflammatory cytokines, and colony-stimulating factor 1 receptor (CSF1R), which is known to regulate the density of microglia, in the corpus callosum in schizophrenia. The interactions between CSF1R and several genes in the presently identified gene network originating from NFATC2 have been reported. Collectively, this study provides evidence regarding lipid abnormalities in the corpora callosa of patients with schizophrenia and proposes the potential role of impaired "NFATC2-relevant gene network-microglial axis" as its underlying mechanism.

Peroxisome proliferator-activated receptor α as a novel therapeutic target for schizophrenia.

BACKGROUND: The pathophysiology of schizophrenia, a major psychiatric disorder, remains elusive. In this study, the role of peroxisome proliferator-activated receptor (PPAR)/retinoid X receptor (RXR) families, belonging to the ligand-activated nuclear receptor superfamily, in schizophrenia, was analyzed. METHODS: The PPAR/RXR family genes were screened by exploiting molecular inversion probe (MIP)-based targeted next-generation sequencing (NGS) using the samples of 1,200 Japanese patients with schizophrenia. The results were compared with the whole-genome sequencing databases of the Japanese cohort (ToMMo) and the gnomAD. To reveal the relationship between PPAR/RXR dysfunction and schizophrenia, Ppara KO mice and fenofibrate (a clinically used PPARα agonist)-administered mice were assessed by performing behavioral, histological, and RNA-seq analyses. FINDINGS: Our findings indicate that c.209-2delA, His117Gln, Arg141Cys, and Arg226Trp of the PPARA gene are risk variants for schizophrenia. The c.209-2delA variant generated a premature termination codon. The three missense variants significantly decreased the activity of PPARα as a transcription factor in vitro. The Ppara KO mice exhibited schizophrenia-relevant phenotypes, including behavioral deficits and impaired synaptogenesis in the cerebral cortex. Oral administration of fenofibrate alleviated spine pathology induced by phencyclidine, an N-methyl-d-aspartate (NMDA) receptor antagonist. Furthermore, pre-treatment with fenofibrate suppressed the sensitivity of mice to another NMDA receptor antagonist, MK-801. RNA-seq analysis revealed that PPARα regulates the expression of synaptogenesis signaling pathway-related genes. INTERPRETATION: The findings of this study indicate that the mechanisms underlying schizophrenia pathogenesis involve PPARα-regulated transcriptional machinery and modulation of synapse physiology. Hence, PPARα can serve as a novel therapeutic target for schizophrenia.

A potential role of fatty acid binding protein 4 in the pathophysiology of autism spectrum disorder.

Autism spectrum disorder is a neurodevelopmental disorder characterized by difficulties in social communication and interaction, as well as repetitive and characteristic patterns of behaviour. Although the pathogenesis of autism spectrum disorder is unknown, being overweight or obesity during infancy and low weight at birth are known as risks, suggesting a metabolic aspect. In this study, we investigated adipose tissue development as a pathophysiological factor of autism spectrum disorder by examining the serum levels of adipokines and other metabolic markers in autism spectrum disorder children (n = 123) and typically developing children (n = 92) at 4-12 years of age. Among multiple measures exhibiting age-dependent trajectories, the leptin levels displayed different trajectory patterns between autism spectrum disorder and typically developing children, supporting an adipose tissue-dependent mechanism of autism spectrum disorder. Of particular interest, the levels of fatty acid binding protein 4 (FABP4) were significantly lower in autism spectrum disorder children than in typically developing subjects, at preschool age (4-6 years old: n = 21 for autism spectrum disorder and n = 26 for typically developing). The receiver operating characteristic curve analysis discriminated autism spectrum disorder children from typically developing children with a sensitivity of 94.4% and a specificity of 75.0%. We re-sequenced the exons of the FABP4 gene in a Japanese cohort comprising 659 autism spectrum disorder and 1000 control samples, and identified two rare functional variants in the autism spectrum disorder group. The Trp98Stop, one of the two variants, was transmitted to the proband from his mother with a history of depression. The disruption of the Fabp4 gene in mice evoked autism spectrum disorder-like behavioural phenotypes and increased spine density on apical dendrites of pyramidal neurons, which has been observed in the postmortem brains of autism spectrum disorder subjects. The Fabp4 knockout mice had an altered fatty acid composition in the cortex. Collectively, these results suggest that an 'adipo-brain axis' may underlie the pathophysiology of autism spectrum disorder, with FABP4 as a potential molecule for use as a biomarker.

LDB2 locus disruption on 4p16.1 as a risk factor for schizophrenia and bipolar disorder.

We had previously reported the case of a male patient with schizophrenia, having de-novo balanced translocation. Here, we determined the exact breakpoints in chromosomes 4 and 13. The breakpoint within chromosome 4 was mapped to a region 32.6 kbp upstream of the LDB2 gene encoding Lim domain binding 2. Variant screening in LDB2 revealed a rare novel missense variant in patients with psychiatric disorder.

VLDL-specific increases of fatty acids in autism spectrum disorder correlate with social interaction.

BACKGROUND: Abnormalities of lipid metabolism contributing to the autism spectrum disorder (ASD) pathogenesis have been suggested, but the mechanisms are not fully understood. We aimed to characterize the lipid metabolism in ASD and to explore a biomarker for clinical evaluation. METHODS: An age-matched case-control study was designed. Lipidomics was conducted using the plasma samples from 30 children with ASD compared to 30 typical developmental control (TD) children. Large-scale lipoprotein analyses were also conducted using the serum samples from 152 children with ASD compared to 122 TD children. Data comparing ASD to TD subjects were evaluated using univariate (Mann-Whitney test) and multivariate analyses (conditional logistic regression analysis) for main analyses using cofounders (diagnosis, sex, age, height, weight, and BMI), Spearman rank correlation coefficient, and discriminant analyses. FINDINGS: Forty-eight significant metabolites involved in lipid biosynthesis and metabolism, oxidative stress, and synaptic function were identified in the plasma of ASD children by lipidomics. Among these, increased fatty acids (FAs), such as omega-3 (n-3) and omega-6 (n-6), showed correlations with clinical social interaction score and ASD diagnosis. Specific reductions of very-low-density lipoprotein (VLDL) and apoprotein B (APOB) in serum of ASD children also were found by large-scale lipoprotein analysis. VLDL-specific reduction in ASD was correlated with APOB, indicating VLDL-specific dyslipidaemia associated with APOB in ASD children. INTERPRETATION: Our results demonstrated that the increases in FAs correlated positively with social interaction are due to VLDL-specific degradation, providing novel insights into the lipid metabolism underlying ASD pathophysiology. FUNDING: This study was supported mainly by MEXT, Japan.

Betaine supplementation is associated with the resilience in mice after chronic social defeat stress: a role of brain-gut-microbiota axis.

BACKGROUND: The brain-gut-microbiota axis plays a role in the pathogenesis of stress-related psychiatric disorders; however, its role in the resilience versus susceptibility after stress remains unclear. Dietary nutrient betaine is suggested to affect the gut microbiome. Here, we examined whether betaine supplementation can affect anhedonia-like phenotype in mice subjected to chronic social defeat stress (CSDS). METHODS: CSDS was performed during betaine supplementation. Sucrose preference test and 16S rRNA analysis of fecal samples were performed. RESULTS: CSDS did not produce an anhedonia-like phenotype in the betaine-treated mice, but did induce an anhedonia-like phenotype in water-treated mice. Furthermore, CSDS treatment did not alter the plasma levels of interleukin-6 (IL-6) of betaine-treated mice whereas CSDS caused higher plasma levels of IL-6 in water-treated mice. Betaine supplementation ameliorated the abnormal diversity and composition of the microbiota in the host gut after CSDS. At the genus level, CSDS caused marked increases in the several bacteria of water-treated mice, but not betaine-treated mice. CSDS increased levels of short-chain fatty acids (i.e., succinic acid and acetic acid) in feces from water-treated mice, but not betaine-treated mice. Interestingly, there are positive correlations between short-chain fatty acids (i.e., succinic acid, acetic acid, butyric acid) and several bacteria among the groups. LIMITATIONS: Specific microbiome were not determined. CONCLUSIONS: These findings suggest that betaine supplementation contributed to resilience to anhedonia in mice subjected to CSDS through anti-inflammation action. Therefore, it is likely that betaine could be a prophylactic nutrient to prevent stress-related psychiatric disorders.

Evaluation of the role of fatty acid-binding protein 7 in controlling schizophrenia-relevant phenotypes using newly established knockout mice.

Dampened prepulse inhibition (PPI) is a consistent observation in psychiatric disorders, including schizophrenia and qualifies as a robust endophenotype for genetic evaluation. Using high PPI C57BL/6NCrlCrlj (B6Nj) and low PPI C3H/HeNCrlCrlj (C3HNj) inbred mouse strains, we have previously reported a quantitative trait locus (QTL) for PPI at chromosome 10 and identified Fabp7 as a candidate gene for regulating PPI and schizophrenia pathogenesis using Fabp7-deficient mice (B6.Cg-Fabp7 KO). Here, considering a possibility of carryover of residual genetic materials from embryonic stem (ES) cells used in generating knockout (KO) mice, we set out to re-address the genotype-phenotype correlation in a uniform genetic background. By generating a new Fabp7 KO mouse model in C57BL/6NCrl (B6N) background using the CRISPR-Cas9 nickase system, we evaluated the impact of Fabp7 ablation on schizophrenia-related behavioral phenotypes. To our surprise, we found no significant differences in PPI or any of the schizophrenia-related behavioral scores, as observed in our previous B6.Cg-Fabp7 KO mice. We identified several C3H/He mouse strain-specific alleles within the interval of chromosome 10-QTL, which are shared with 129/Sv mouse strains. These alleles, derived from 129/Sv ES cells, were retained in the B6.Cg-Fabp7 KO, despite multiple backcrossing and are thought to be responsible for the dampened PPI. In summary, our study demonstrates a precise genotype-phenotype relation for Fabp7 loss-of-function in a uniform B6N background, and raises the necessity of further analysis of the effects of genomic variants flanking the Fabp7 interval on phenotypes.

Enhanced carbonyl stress induces irreversible multimerization of CRMP2 in schizophrenia pathogenesis.

Enhanced carbonyl stress underlies a subset of schizophrenia, but its causal effects remain elusive. Here, we elucidated the molecular mechanism underlying the effects of carbonyl stress in iPS cells in which the gene encoding zinc metalloenzyme glyoxalase I (GLO1), a crucial enzyme for the clearance of carbonyl stress, was disrupted. The iPS cells exhibited significant cellular and developmental deficits, and hyper-carbonylation of collapsing response mediator protein 2 (CRMP2). Structural and biochemical analyses revealed an array of multiple carbonylation sites in the functional motifs of CRMP2, particularly D-hook (for dimerization) and T-site (for tetramerization), which are critical for the activity of the CRMP2 tetramer. Interestingly, carbonylated CRMP2 was stacked in the multimer conformation by irreversible cross-linking, resulting in loss of its unique function to bundle microtubules. Thus, the present study revealed that the enhanced carbonyl stress stemmed from the genetic aberrations results in neurodevelopmental deficits through the formation of irreversible dysfunctional multimer of carbonylated CRMP2.

Excess hydrogen sulfide and polysulfides production underlies a schizophrenia pathophysiology.

Mice with the C3H background show greater behavioral propensity for schizophrenia, including lower prepulse inhibition (PPI), than C57BL/6 (B6) mice. To characterize as-yet-unknown pathophysiologies of schizophrenia, we undertook proteomics analysis of the brain in these strains, and detected elevated levels of Mpst, a hydrogen sulfide (H2 S)/polysulfide-producing enzyme, and greater sulfide deposition in C3H than B6 mice. Mpst-deficient mice exhibited improved PPI with reduced storage sulfide levels, while Mpst-transgenic (Tg) mice showed deteriorated PPI, suggesting that "sulfide stress" may be linked to PPI impairment. Analysis of human samples demonstrated that the H2 S/polysulfides production system is upregulated in schizophrenia. Mechanistically, the Mpst-Tg brain revealed dampened energy metabolism, while maternal immune activation model mice showed upregulation of genes for H2 S/polysulfides production along with typical antioxidative genes, partly via epigenetic modifications. These results suggest that inflammatory/oxidative insults in early brain development result in upregulated H2 S/polysulfides production as an antioxidative response, which in turn cause deficits in bioenergetic processes. Collectively, this study presents a novel aspect of the neurodevelopmental theory for schizophrenia, unraveling a role of excess H2 S/polysulfides production.

Investigation of betaine as a novel psychotherapeutic for schizophrenia.

BACKGROUND: Betaine is known to act against various biological stresses and its levels were reported to be decreased in schizophrenia patients. We aimed to test the role of betaine in schizophrenia pathophysiology, and to evaluate its potential as a novel psychotherapeutic. METHODS: Using Chdh (a gene for betaine synthesis)-deficient mice and betaine-supplemented inbred mice, we assessed the role of betaine in psychiatric pathophysiology, and its potential as a novel psychotherapeutic, by leveraging metabolomics, behavioral-, transcriptomics and DNA methylation analyses. FINDINGS: The Chdh-deficient mice revealed remnants of psychiatric behaviors along with schizophrenia-related molecular perturbations in the brain. Betaine supplementation elicited genetic background-dependent improvement in cognitive performance, and suppressed methamphetamine (MAP)-induced behavioral sensitization. Furthermore, betaine rectified the altered antioxidative and proinflammatory responses induced by MAP and in vitro phencyclidine (PCP) treatments. Betaine also showed a prophylactic effect on behavioral abnormality induced by PCP. Notably, betaine levels were decreased in the postmortem brains from schizophrenia, and a coexisting elevated carbonyl stress, a form of oxidative stress, demarcated a subset of schizophrenia with "betaine deficit-oxidative stress pathology". We revealed the decrease of betaine levels in glyoxylase 1 (GLO1)-deficient hiPSCs, which shows elevated carbonyl stress, and the efficacy of betaine in alleviating it, thus supporting a causal link between betaine and oxidative stress conditions. Furthermore, a CHDH variant, rs35518479, was identified as a cis-expression quantitative trait locus (QTL) for CHDH expression in postmortem brains from schizophrenia, allowing genotype-based stratification of schizophrenia patients for betaine efficacy. INTERPRETATION: The present study revealed the role of betaine in psychiatric pathophysiology and underscores the potential benefit of betaine in a subset of schizophrenia. FUND: This study was supported by the Strategic Research Program for Brain Sciences from AMED (Japan Agency for Medical Research and Development) under Grant Numbers JP18dm0107083 and JP19dm0107083 (TY), JP18dm0107129 (MM), JP18dm0107086 (YK), JP18dm0107107 (HY), JP18dm0107104 (AK) and JP19dm0107119 (KH), by the Grant-in-Aid for Scientific Research on Innovative Areas from the MEXT under Grant Numbers JP18H05435 (TY), JP18H05433 (AH.-T), JP18H05428 (AH.-T and TY), and JP16H06277 (HY), and by JSPS KAKENHI under Grant Number JP17H01574 (TY). In addition, this study was supported by the Collaborative Research Project of Brain Research Institute, Niigata University under Grant Numbers 2018-2809 (YK) and RIKEN Epigenetics Presidential Fund (100214-201801063606-340120) (TY).

Thiosulfate promotes hair growth in mouse model.

The present study describes the hair growth-promoting effects of sodium thiosulfate (STS), a widely used compound, in mice. STS accelerated hair growth in the "telogen model", suggesting that it stimulates telogen hair follicles to reenter the anagen phase of hair growth. In the same model, STS potentiated hair growth in an additive manner with minoxidil (MXD), a drug used for the treatment of androgenic alopecia. Furthermore, in the "anagen model", STS promoted hair growth, probably by promoting hair follicle proliferation. Since STS elevated the skin surface temperature, its hair growth-promoting activity may be partly due to vasorelaxation, similar to MXD. In addition, STS is known to generate a gaseous mediator, H2S, which has vasorelaxation and anti-inflammatory/anti-oxidative stress activities. Therefore, STS and/or provisionally its metabolite, H2S, may aid the hair growth process. Collectively, these results suggest that salts of thiosulfate may represent a novel and beneficial remedy for hair loss.

Quantitative evaluation of incomplete preweaning lethality in mice by using the CRISPR/Cas9 system.

Various molecular biology techniques implementing genome editing have made it possible to generate mouse mutants for nearly all known genes; as a result, the International Mouse Phenotyping Consortium (IMPC) database listing the phenotypes of genetically modified mice has been established. Among mouse phenotypes, lethality is crucial to evaluate the importance of genes in mouse survival. Although many genes are reported to show "preweaning lethality, incomplete penetrance" in the IMPC database, the survival rates of homozygous knockout mice are highly variable. Here, we propose the lethal allele index (LAI), the ratio of the observed number of mice with homozygous knockout (KO) to the theoretically predicted number of homozygous KO mice, as a simple quantitative indicator of preweaning lethality. Among the mice mutants registered as incompletely lethal in IMPC, the LAI calculated from the genotypes of F1 mice tended to be lower in disease-related genes, and correlated with the frequency of loss-of-function (LOF) alleles in humans. In genome-edited mice using CRISPR/Cas9, the number of mice with homozygous frameshift alleles seemed to be associated with lethality. We edited the Ehd1 gene in cell lines as well as mice using CRISPR/Cas9, and found that the genotype distribution was significantly different. The LAI calculated from these data was similar to the value calculated from the IMPC data. These findings support the potential usefulness of the LAI as an index of preweaning lethality in genome-edited mice.

A spontaneous and novel Pax3 mutant mouse that models Waardenburg syndrome and neural tube defects.

BACKGROUND: Genes responsible for reduced pigmentation phenotypes in rodents are associated with human developmental defects, such as Waardenburg syndrome, where patients display congenital deafness along with various abnormalities mostly related to neural crest development deficiency. OBJECTIVE: In this study, we identified a spontaneous mutant mouse line Rwa, which displays variable white spots on mouse bellies and white digits and tail, on a C57BL/6N genetic background. Curly tail and spina bifida were also observed, although at a lower penetrance. These phenotypes were dominantly inherited by offspring. We searched for the genetic mechanism of the observed phenotypes. METHODS: We harnessed a rapid mouse gene mapping system newly developed in our laboratories to identify a responsible gene. RESULTS: We detected a region within chromosome 1 as a probable locus for the causal mutation. Dense mapping using interval markers narrowed the locus down to a 670-kbp region, containing four genes including Pax3, a gene known to be implicated in the types I and III Waardenburg syndrome. Extensive mutation screening of Pax3 detected an 841-bp deletion, spanning the promoter region and intron 1 of the gene. The defective allele of Pax3, named Pax3Rwa, lacked the first coding exon and co-segregated perfectly with the phenotypes, confirming its causal nature. The genetic background of Rwa mice is almost identical to that of inbred C57BL/6N. CONCLUSION: These results highlight Pax3Rwa mice as a beneficial tool for analyzing biological processes involving Pax3, in particular the development and migration of neural crest cells and melanocytes.

Human nonsense-mediated mRNA decay factor UPF2 interacts directly with eRF3 and the SURF complex.

Nonsense-mediated mRNA decay (NMD) is an mRNA degradation pathway that regulates gene expression and mRNA quality. A complex network of macromolecular interactions regulates NMD initiation, which is only partially understood. According to prevailing models, NMD begins by the assembly of the SURF (SMG1-UPF1-eRF1-eRF3) complex at the ribosome, followed by UPF1 activation by additional factors such as UPF2 and UPF3. Elucidating the interactions between NMD factors is essential to comprehend NMD, and here we demonstrate biochemically and structurally the interaction between human UPF2 and eukaryotic release factor 3 (eRF3). In addition, we find that UPF2 associates with SURF and ribosomes in cells, in an UPF3-independent manner. Binding assays using a collection of UPF2 truncated variants reveal that eRF3 binds to the C-terminal part of UPF2. This region of UPF2 is partially coincident with the UPF3-binding site as revealed by electron microscopy of the UPF2-eRF3 complex. Accordingly, we find that the interaction of UPF2 with UPF3b interferes with the assembly of the UPF2-eRF3 complex, and that UPF2 binds UPF3b more strongly than eRF3. Together, our results highlight the role of UPF2 as a platform for the transient interactions of several NMD factors, including several components of SURF.

Investigation of the fatty acid transporter-encoding genes SLC27A3 and SLC27A4 in autism.

The solute carrier 27A (SLC27A) gene family encodes fatty acid transport proteins (FATPs) and includes 6 members. During fetal and postnatal periods of development, the growing brain requires a reliable supply of fatty acids. Because autism spectrum disorders (ASD) are now recognized as disorders caused by impaired early brain development, it is possible that functional abnormalities of SLC27A genes may contribute to the pathogenesis of ASD. Here, we confirmed the expression of SLC27A3 and SLC27A4 in human neural stem cells derived from human induced pluripotent stem cells, which suggested their involvement in the developmental stage of the central nervous system. Additionally, we resequenced the SLC27A3 and SLC27A4 genes using 267 ASD patient and 1140 control samples and detected 47 (44 novel and 29 nonsynonymous) and 30 (17 novel and 14 nonsynonymous) variants for the SLC27A3 and SLC27A4, respectively, revealing that they are highly polymorphic with multiple rare variants. The SLC27A4 Ser209 allele was more frequently represented in ASD samples. Furthermore, we showed that a SLC27A4 Ser209 mutant resulted in significantly higher fluorescently-labeled fatty acid uptake into bEnd3 cells, a mouse brain capillary-derived endothelial cell line, compared with SLC27A4 Gly209, suggesting that the functional change may contribute to ASD pathophysiology.