Role of the cytoplasmic isoform of RBFOX1/A2BP1 in establishing the architecture of the developing cerebral cortex
© Hamada et al. 2015
Received: 25 June 2015
Accepted: 10 October 2015
Published: 20 October 2015
RBFOX1 (also known as FOX1 or A2BP1) regulates alternative splicing of a variety of transcripts crucial for neuronal functions. Physiological significance of RBFOX1 during brain development is seemingly essential since abnormalities in the gene cause autism spectrum disorder (ASD) and other neurodevelopmental and neuropsychiatric disorders such as intellectual disability, epilepsy, attention deficit hyperactivity disorder, and schizophrenia. RBFOX1 was also shown to serve as a “hub” in ASD gene transcriptome network. However, the pathophysiological significance of RBFOX1 gene abnormalities remains to be clarified.
To elucidate the pathophysiological relevance of Rbfox1, we performed a battery of in vivo and in vitro analyses of the brain-specific cytoplasmic isoform, Rbfox1-iso2, during mouse corticogenesis. In vivo analyses were based on in utero electroporation, and the role of Rbfox1-iso2 in cortical neuron migration, neurogenesis, and morphology was investigated by morphological methods including confocal laser microscope-assisted time-lapse imaging. In vitro analyses were carried out to examine the morphology of primary cultured mouse hippocampal neurons.
Silencing of Rbfox1-iso2 in utero caused defects in the radial migration and terminal translocation of cortical neurons during corticogenesis. Time-lapse imaging revealed that radial migration was apparently impaired by dysregulated nucleokinesis. Rbfox1-iso2 also regulated neuronal network formation in vivo since axon extension to the opposite hemisphere and dendritic arborization were hampered by the knockdown. In in vitro analyses, spine density and mature spine number were reduced in Rbfox1-iso2-deficient hippocampal neurons.
Impaired Rbfox1-iso2 function was found to cause abnormal corticogenesis during brain development. The abnormal process may underlie the basic pathophysiology of ASD and other neurodevelopmental disorders and may contribute to the emergence of the clinical symptoms of the patients with RBFOX1 gene abnormalities.
KeywordsRbfox1 Neuronal migration Axon growth Synapse formation Corticogenesis
RNA-binding Fox1 (Rbfox1), also known as Fox-1 or ataxin-2-binding protein 1 (A2BP1), was first identified as a binding partner for ataxin-2 . Rbfox1 is dominantly expressed in the neuronal tissues, muscle, and heart and has been reported to play a pivotal role in alternative splicing of genes critical for neuronal development such as calcitonin/calcitonin gene-related peptide, CaV1.2 voltage-gated calcium channels, and N-methyl-d-aspartate (NMDA) receptor 1 [2–5].
Accumulating clinical reports strongly suggest the involvement of RBFOX1 in various neurodevelopmental disorders. Fluorescence in situ hybridization (FISH), array comparative genomic hybridization (aCGH), and genome-wide linkage studies (GWAS) have been demonstrated that RBFOX1 is associated with autism spectrum disorder (ASD) and other neuropsychiatric disorders including intellectual disabilities (IDs), epilepsy, attention deficit hyperactivity disorder (ADHD), and schizophrenia [6–15]. In addition, RBFOX1 target transcripts predicted by bioinformatics are significantly overlapping with genes implicated in ASD . Furthermore, RBFOX1 was found to serve as a “hub” in gene transcriptome networks based on the weighed gene coexpression network analysis and microarray profiling of postmortem ASD patient brains . Interestingly, abnormal reduction of RBFOX1 expression in a subset of ASD patient brains was correlated with altered splicing of its predicted targets including two ASD-related genes (GRIN1 and MEF2C), although the pathophysiological relevance of the splicing variation remains to be elucidated . In addition, massive splicing changes were detected in 48 genes in a group of ASD patient brains where downregulation of RBFOX1 was estimated .
In this report, we focused on an Rbfox-1 isoform, Rbfox1-iso2, which is distributed dominantly in the cytoplasm of cortical neurons [19, 20], and analyzed its function in brain development. While Rbfox1-iso2 appeared not to be involved in neuronal cell proliferation, its deficiency caused defects in migration, axon growth, and dendrite development of excitatory neurons during corticogenesis. The results obtained here indicate that Rbfox1-iso2 may play a crucial role in cerebral cortex development independently of the nuclear isoform Rbfox1-iso1, and functional defects of Rbfox1-iso2 may be related to the etiology of ASD and neurodevelopmental disorders with the gene abnormalities.
We followed the Fundamental Guidelines for Proper Conduct of Animal Experiments and Related Activity in Academic Research Institution under the jurisdiction of the Ministry of Education, Culture, Sports, Science and Technology, and all of the protocols for animal handling and treatment were reviewed and approved by the Animal Care and Use Committee of Institute for Developmental Research, Aichi Human Service Center (approval number, M10).
Mouse (m)Rbfox1-iso2(A2BP1-A030) and Rbfox1-iso1(A2BP1-A016) cDNAs in pCS-MT vector with Myc-tag were supplied by Dr. S. Kawamoto (NIH, MD)[19, 21] and constructed into pCAG-Myc vector (Addgene Inc., Cambridge, MA). pCAG-PACKmKO1 and pβAct-EGFP were gifts from Drs. F. Matsuzaki (RIKEN, Kobe, Japan)  and S. Okabe (Univ. Tokyo, Japan) , respectively. pCAG-histone 2B (H2B)-EGFP was used to label chromosomes. pCAG-M-Cre was from Dr S. Miyagawa (Univ. Osaka, Japan) , and pCALNL (loxP-neomycin-loxP)-GFP was made from pCALNL-DsRed (Addgene Inc.). The following target sequences were inserted into pSuper-puro RNAi vector (OligoEngine, Seattle, WA): mRbfox1-iso1, GACTAGGAGCCATGCTGAT (1098-1106 in mRbfox1-iso1) ; mRbfox1-iso2, GATGAAATTTCTTGTAACA (1018-1036 in mRbfox1-iso2); mRbfox1-iso1/2, GTAAAATCGAGGTTAATAA (548-566 in mRbfox1-iso1). Numbers indicate the positions from translational start sites. We named these vectors as pSuper-mRbfox1-iso1, pSuper-mRbfox1-iso2, and pSuper-mRbfox1-iso1/2. For the control RNAi experiments, we used pSuper-H1.shLuc, a shRNA designed against luciferase (CGTACGCGGAATACTTCGA)  as well as pSuper vector, both of which had no effects on the phenotypes analyzed here. To make an RNAi-resistant version of mRbfox1-iso2, mRbfox1-iso2R, silent mutations were introduced in the target sequence as underlined (GACGAGATCAGCTGCAATA in mRbfox1-iso2).
Polyclonal anti-A2BP1(Rbfox1) and anti-Sept11 were generated as described [20, 26]. Polyclonal rabbit antibodies for green fluorescent protein (GFP) and red fluorescent protein (RFP) were from MBL (Nagoya, Japan) and Rockland Immunochemicals (Gilbertsville, PA), respectively. Anti-GFP (Chicken) was purchased from AVES Labs (Tigard, OR). Rabbit polyclonal anti-Ki67 was from Thermo Scientific Japan (Yokohama, Japan).
Cell culture, transfection, western blotting, and immunofluorescence
COS7 and mouse primary neurons were cultured essentially as described [27, 28]. Transfection was done with Lipofectamine 2000 (Life Technologies Japan, Tokyo). Western blotting was carried out as described . We used Sept11, a ubiquitously expressed cytoskeletal protein , as a loading control. Immunofluorescence analyses were performed with Alexa Fluor 488- or 568-labeled IgG (Life Technologies Japan) as a secondary antibody . Fluorescent images were obtained using FV-1000 confocal laser microscope (Olympus, Tokyo, Japan).
In utero electroporation and time-lapse imaging
Pregnant ICR mice were purchased from SLC Japan (Shizuoka, Japan). In utero electroporation was performed essentially as described . Each RNAi vector (1 μg) was electroporated with GFP vector (0.5 μg) in a total volume of 1 μl. Live-imaging analyses were performed essentially as described .
Quantitative analysis of neuronal migration
The coronal sections of cerebral cortices containing the labeled cells were classified into five bins and the intermediate zone (IZ) as described previously .
EdU incorporation experiments
pCAG-H2B-EGFP vector was electroporated in utero into embryos with pSuper vector (control) or pSuper-mRbfox1-iso2 at embryonic day (E)14. Forty hours after electroporation, pregnant mice were given an intraperitoneal injection of 5-ethynyl-2′-deoxyuridine (EdU) at 25 mg/kg body weight. One hour after injection, brains were fixed with 4 % paraformaldehyde and frozen sections were made. GFP and EdU were detected with anti-GFP and Alexa Fluor555 azide (Life Technologies Japan), respectively. When the ratio of EdU/Ki67/GFP-triple-positive cells to EdU/GFP-double-positive ones was determined, EdU injection was done at 24 h after electroporation. Brains were then sectioned after 24 h and subjected to detection for EdU, Ki67, and GFP.
Quantitative analysis of axon growth
RFP signal intensity of the callosal axons was measured in a 170 × 200 μm rectangle on both the ipsilateral (green) and contralateral (white) sides at the positions indicated in Fig. 5a (left panel). The ratio of the axonal RFP signals in the contralateral side to the corresponding ipsilateral side was calculated.
Quantitative analysis of spine morphologies
Transfected neurons were immunostained with anti-GFP and chosen randomly. For morphology analyses, we took 0.5 μm z-series stacks to generate image projections and obtained images with FV-1000 confocal microscope. For density analyses, spines were defined as 0.5–6-μm lengths, with or without a head, and measured by counting the number of protrusions in 10-μm length of primary dendrites. Spine density was first averaged per neuron, and means from multiple individual neurons were calculated. Morphological assessments of spine density and shape were conducted blindly.
Stereological tools used for cell counting and quantification
ImageJ software was used for the analyses within the brain slices such as cell counting, axon extension into contralateral cortex (Fig. 5c), dendritic length, and Sholl test. Axon elongation analyses (Fig. 5a) were performed using Adobe Photoshop software.
Results were expressed as means ± SD. When data were obtained from only two groups, Student’s and Welch’s t test were used for comparison. Sholl radii or branch orders were analyzed using two-way repeated measures ANOVA with multiple comparisons made using the Tukey-Kramer least significant difference (LSD) test. For other experiments, the rate of cell scores were initially analyzed using the one-way analysis of variance (ANOVA). Subsequently, Tukey-Kramer least significant difference (LSD) test was applied to absolute values as a post hoc test of multiple comparisons. The level of statistical significance was considered to be p < 0.05. Statistical analysis was performed using Statcel3 software (OMS Inc., Tokorozawa, Japan).
Roles of Rbfox1-iso2 in neuronal positioning during corticogenesis
pCAG-EGFP was electroporated in utero with pSuper-H1.shLuc control or pSuper-mRbfox1-RNAi vectors into ventricular zone (VZ) progenitor cells of mice brains at E14.5, and localization of the transfected cells and their progeny was visualized at postnatal day (P) 3. While control neurons were positioned normally at the superficial layer (bin 1; layers II~III) of cortical plate (CP), a considerable portion of cells transfected with pSuper-mRbfox1-iso2 or pSuper-mRbfox1-iso1/2 remained in the lower zone of CP and intermediate zone (IZ) (Fig. 1b, c). To examine the specific role of mRbfox1-iso2, we hereafter used pSuper-mRbfox1-iso2 throughout the study. It should be noted that many mRbfox1-iso2-deficient neurons reached the superficial layer (Fig. 1b, c). Transfection efficiency may explain the result; mRbfox1-iso2 was incompletely knocked down in neurons incorporating low amount of the RNAi vector. Rescue experiments were then performed to rule out off-target effects by the use of mRbfox1-iso2R that was resistant to pSuper-mRbfox1-iso2 (Fig. 1d). When pSuper-mRbfox1-iso2 was coelectroporated with pCAG-Myc-mRbfox1-iso2R, the positional defects were rescued at P3 (Fig. 1e, f), indicating that the abnormal positioning observed was indeed caused by reduced expression of mRbfox1-iso2. When we analyzed the effects of mRbfox1-iso2-knockdown on the neuronal migration at E17, positioning defects were detected at this stage; while most control neurons were migrating in CP, many mRbfox1-iso2-deficient neurons were still in IZ (Fig. 1g). We then examined the long-term effects at P7 and P16 and found that many mRbfox1-iso2-deficient cells did not make it to the correct target destination (layers II–IV) at these time points. These results suggest that efficient mRbfox1-iso2-silencing caused defects in the radial migration of cortical neurons.
Since cell morphology is closely associated with migration, we looked into the shape of mRbfox1-iso2-deficient neurons with abnormal positioning at E17.5 (Fig. 1g). Consequently, the deficient neurons transformed smoothly into bipolar status in the upper IZ and had apparently normal bipolar morphology in CP (Fig. 1g; E17.5), suggesting that mRbfox1-iso2 is not directly involved in neuronal morphology before and during migration. However, it should be noted that we here analyzed fixed cells and the obtained results are considered as snapshots at the time point.
Time-lapse imaging of migration of mRbfox1-iso2-deficient neurons in cortical slices
It is notable that many mRbfox1-iso2-deficient cells still crossed IZ and moved into CP. We thus monitored the migration of such cells in CP. While control cells showed smooth locomotion in CP (Fig. 2d, control panels, Additional file 3: Video 3), the deficient cells exhibited characteristic migration defects (Fig. 2d, iso2 panels, e and Additional file 4: Video 4). While the deficient cells maintained apparently normal bipolar shape during radial migration (Fig. 2f, g), the distance between the nucleus and the preceding centrosome (N-C distance) was abnormally longer, suggestive of the impaired nucleokinesis (Fig. 2h). Nucleokinesis is the process of translocation of the nucleus into the proximal leading process during radial migration and dependent on the microtubule dynamics . Although dynamic changes of the microtubule function significantly affect the radial migration profile and we showed the N-C distance abnormality (Fig. 2h), cell shapes in snapshot data do not satisfactorily reveal changes in the microtubule dynamics and thus time-lapse imaging analyses are very useful. Collectively, mRbfox1-iso2 may be involved in the crossing over the IZ-CP border after multipolar-bipolar transition in the upper IZ and subsequent radial migration in CP. We suppose that the migration defects observed depend on the degree of knockdown; while migration defects might take place at the IZ-CP border when the RNAi effect is strong, the aberrant migration phenotype might be observed in CP after crossing the border when the RNAi effect is relatively weak.
Involvement of mRbfox1-iso2 in the terminal translocation of cortical neurons
Role of mRbfox1-iso2 in the proliferation of neuronal progenitor and stem cells
We further looked into the effects of mRbfox1-iso2-silencing on the proliferation of neuronal progenitor and stem cells by triple staining for EdU, GFP, and Ki67, a marker for all active phases of the cell cycle except the quiescent G0 state. In this analysis, cells still in proliferating after EdU incorporation could be identified as EdU/Ki67-double-positive while neurons that differentiated after EdU incorporation would be EdU-positive but Ki67-negative. Consequently, between control and mRbfox1-iso2-deficient cells, no statistical differences were observed in the ratio of EdU/Ki67/GFP-triple-positive cells to EdU/GFP-double-positive cells, indicating that mRbfox1-iso2-deficient progenitor and stem cells differentiated to neuronal cells at a rate similar to the control cells (Fig. 4c, d).
Taken together with the result that mRbfox1 was limitedly expressed in CP and upper IZ but not VZ/SVZ during corticogenesis , we concluded that the positioning defects by mRbfox1-iso2-silencing resulted from abnormal neuron migration.
mRbfox1-iso2 regulates axon elongation and dendrite development in vivo
Involvement of mRbfox1-iso2 in spine morphology in vitro
ASD is highly heritable, and the genetic basis has been pursued intensively using genetic and genomic analyses, which have identified a variety of genetic causes that account for ~20 % of ASD cases, including genetic copy number variation (CNV), syndromic forms of ASD, and single-gene and metabolic disorders .
RBFOX1 has been shown to play a central “hub” role in the ASD gene transcriptome network . mRbfox1 functions as an RNA splicing factor and is expressed in differentiated and migrating neurons in developing mouse cerebral cortex and is excluded from cells in proliferative zones based on both in situ hybridization (E15)  and immunohistochemistry (E17) . Since cell biological relevance of RBFOX1 in the brain development has been enigmatic, we carried out comprehensive in vivo and in vitro analyses to obtain information to understand the etiology of ASD and other neurodevelopmental disorders in which RBFOX1 gene abnormalities are involved. While there are seven RBFOX1 mRNA variants encoding total six isoforms (variants 4 and 6 both encode isoform 4) based on the NCBI database (http://www.ncbi.nlm.nih.gov/gene/54715), we here focused on the brain-specific cytosolic isoform, Rbfox1-iso2. Inclusion and exclusion of exon A53 result in Rbfox1-iso1 and Rbfox1-iso2, respectively, with different amino acid sequences at the C-terminal regions owning to a frame shift . While Rbfox1-iso1 is the major Rbfox1 isoform residing in the nucleus, Rbfox1-iso2 is a relatively minor isoform which distributes in the cytoplasm [19, 20]. It is most likely that the specific distribution of Rbfox1-iso1 and Rbfox1-iso2 in the nucleus and cytosol, respectively, should be attributable to the C-terminal sequence difference.
When mRbfox1-iso2 was silenced in utero and the phenotypes were examined, defects in radial migration, terminal translocation, axon elongation to the contralateral cortex, and dendritic arbor formation were observed. These results imply functional impairment of the cytoskeleton system in the deficient neurons. In this context, FLNA-encoding actin-binding protein FilaminA and RHOA-encoding small GTPase RhoA have been reported to be downstream splicing candidates for RBFOX1 . In addition, RBFOX1 is possible to regulate expression of DCX encoding microtubule-binding protein and CDK5R1 encoding regulatory subunit of CDK5 kinase . On the other hand, cell cycle (proliferation) of VZ/SVZ cells was not affected by mRbfox1-knockdown, consistent with the observation that mRbfox1 is predominantly expressed in neurons but not in progenitor and stem cells in the proliferative zone.
It is also notable that in vitro experiments strongly suggest that Rbfox1-iso2 serves as a regulator for spine morphology and dynamics; immature (stubby) spine was increased when mRbfox1-iso2 was silenced in primary cultured hippocampal neurons. Since neurodevelopmental disorders such as ASD and schizophrenia are thought to be “synapse” diseases, these results suggest a crucial role of Rbfox1-iso2 in not only the developing but also the adult brain. Together with the report that mRbfox1-expressing neurons were distributed throughout the cortex when the cortical formation completed , RBFOX1 gene abnormalities may influence the clinical features of ASD and other neurodevelopmental disorders in the adult stage through disruption of synapse functions [6–8].
RBFOX1-downregulation has been shown in a subset of ASD patient brains, leading to splicing changes of genes encoding various proteins essential for cytoskeleton, scaffolding, synaptic transmission, ion channels, and transcription regulation . Meanwhile, further intensive analyses are required to address this issue, since no significant difference in RBFOX1 expression in lymphoblastoid cell lines has been reported between ASD cases and controls sibs . While RBFOX1 gene abnormalities may form common pathophysiological background in the patients, aberrant splicing is possible to occur in a manner which depends on the genetic background of each patient and might be related to the pathophysiology of divergent clinical symptoms in ASD. In either case, it seems to be crucial to find not only yet unidentified splicing targets but also environmental and/or genetic modification factors which may explain the complexity of etiology and clinical symptoms of ASD involving RBFOX1 gene abnormalities.
Considering that splicing and transcription occur in the nucleus, Rbfox1-iso2 is supposed to exert its function through shuttling between the nucleus and cytoplasm as in the case of a group of splicing factors called heterogeneous nuclear ribonucleoproteins (hnRNPs) . Interestingly, hnRNPs are known to have additional cytoplasmic roles in mRNA-transport, mRNA-localization, mRNA-turnover, and regulation of translation [40, 41]. It is thus tempting to speculate that Rbfox1-iso2 participates in cytoplasmic events as well as RNA splicing in the nucleus. It should be noted that similar but not identical phenotypes were obtained in the neuronal cell migration and morphology when mRbfox1-iso1 was knocked down.1 The phenotype difference in the two isoforms might be explained by their distinct functions, such as yet unidentified cytoplasmic role of Rbfox1-iso2, based on the different localization and/or C-terminal amino acid structure. On the other hand, transient nuclear distribution of Rbfox1-iso2 by shuttling might be important for its RNA splicing function and explain the phenotype similarity to Rbfox1-iso1.
From the observations in this study, mRbfox1-iso2 was shown to be involved in the regulation of various processes essential for the cortical development. A variety of aberrant phenotypes observed during corticogenesis (defects in migration, axon growth, and dendrite arborization) and in vitro analyses (defects in spine morphology) may be the consequence of the impaired splicing events in affected neurons and could account for the emergence of the various clinical symptoms of ASD and other disorders such as ADHD, ID, epilepsy, and schizophrenia, where RBFOX1 gene abnormalities are involved. Molecular aspects of impaired splicing events in Rbfox1-deficient neurons remain to be clarified. Aberrant phenotypes observed in this study are also supposed to be involved in the various clinical symptoms of ASD and other neurodevelopmental disorders. Further intensive studies to elucidate the molecular bases of physiological and pathophysiological roles of mRbfox1 isoforms are essential to understand the commonality and diversity of the abovementioned disorders.
Gene abnormalities in RBFOX1, encoding an mRNA-splicing factor, have been shown to cause ASD and other neurodevelopmental and psychiatric disorders such as ID, ADHD, and schizophrenia. Notably, RBFOX1 was recently found to serve as a “hub” in ASD gene transcriptome networks by a sophisticated system biology approach, strongly suggesting the key role of this gene in the pathophysiology common to the above disorders. Since the physiological role of RBFOX1 in cortical development is still largely unknown, it is essential to elucidate the function in corticogenesis for understanding the pathophysiological significance of the molecule in ASD and related disorders.
To elucidate the pathophysiological relevance of RBFOX1, we focused on the cytoplasmic isoform of Rbfox1 (Rbfox1-iso2) and examined its role during mouse corticogenesis in vivo and in vitro. Knockdown of Rbfox1-iso2 in vivo caused defects in the initiation and maintenance of radial migration and the completion of terminal translocation of cortical neurons. Rbfox1-iso2 was also found to regulate synapse network formation since axon growth and dendritic arborization were abrogated when this molecule was silenced in vivo. In vitro experiments revealed that spine density and mature spine number were reduced in Rbfox1-iso2-deficient primary cultured hippocampal neurons. Abnormal phenotypes observed were similar but not the same as those in the nuclear isoform Rbfox1-iso1-deficient neurons.
Consequently, we found an essential role of a cytosolic isoform of Rbfox1, Rbfox1-iso2, in the cortical development. Functional abnormalities in Rbfox1-iso2-deficient neurons may induce structural and functional defects of the cerebral cortex and consequently contribute to the clinical symptoms of ASD and other neurodevelopmental and psychiatric disorders with RBFOX1 gene abnormalities.
The experimental results will be described elsewhere.
Attention deficit hyperactivity disorder
Autism spectrum disorder
Primitive cortical zone
This work was supported in part by grants from Ministry of Education, Science, Technology, Sports and Culture of Japan (No. 24390271, 25122722, 25670488), a grant-in-aid of the Practical Research Project for Rare/Intractable Diseases from Japan Agency for Medical Research and Development (AMED), and grants from the 24th General Assembly of the Japanese Association of Medical Science and Takeda Science Foundation.
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- Shibata H, Huynh DP, Pulst SM. A novel protein with RNA-binding motifs interacts with ataxin-2. Hum Mol Gen. 2000;9:1303–13.View ArticlePubMedGoogle Scholar
- Lee JA, Tang ZZ, Black DL. An inducible change in Fox-1/A2BP1 splicing modulates the alternative splicing of downstream neuronal target exons. Genes Dev. 2009;23:2284–93.PubMed CentralView ArticlePubMedGoogle Scholar
- Gehman LT, Stoilov P, Maguire J, Damianov A, Lin C-H, Shiue L, et al. The splicing regulator Rbfox1 (A2BP1) controls neuronal excitation in the mammalian brain. Nat Genet. 2011;43:706–11.PubMed CentralView ArticlePubMedGoogle Scholar
- Zhou HL, Baraniak AP, Lou H. Role for Fox-1/Fox-2 in mediating the neuronal pathway of calcitonin/calcitonin gene-related peptide alternative RNA processing. Mol Cell Biol. 2007;27:830–41.PubMed CentralView ArticlePubMedGoogle Scholar
- Tang ZZ, Zheng S, Nikolic J, Black DL. Developmental control of CaV1.2 L-type calcium channel splicing by fox proteins. Mol Cell Biol. 2009;29:4757–65.PubMed CentralView ArticlePubMedGoogle Scholar
- Bhalla K, Phillips HA, Crawford J, McKenzie OLD, Mulley JC, Eyre H, et al. The de novo chromosome 16 translocations of two patients with abnormal phenotypes (mental retardation and epilepsy) disrupt the A2BP1 gene. J Hum Genet. 2004;49:308–11.View ArticlePubMedGoogle Scholar
- Elia J, Gai X, Xie HM, Perin JC, Geiger E, Glessner JT, et al. Rare structural variants found in attention-deficit hyperactivity disorder are preferentially associated with neurodevelopmental genes. Mol Psychiatry. 2009;15:637–46.PubMed CentralView ArticlePubMedGoogle Scholar
- Xu B, Roos JL, Levy S, van Rensburg EJ, Gogos JA, Karayiorgou M. Strong association of de novo copy number mutations with sporadic schizophrenia. Nat Genet. 2008;40:880–5.View ArticlePubMedGoogle Scholar
- Hamshere ML, Green EK, Jones IR, Jones L, Moskvina V, Kirov G, et al. Genetic utility of broadly defined bipolar schizoaffective disorder as a diagnostic concept. Br J Psychiatry. 2009;195:23–9.PubMed CentralView ArticlePubMedGoogle Scholar
- Bucan M, Abrahams BS, Wang K, Glessner JT. Genome-wide analyses of exonic copy number variants in a family-based study point to novel autism susceptibility genes. PLoS Genet. 2009.
- Gai X, Xie HM, Perin JC, Takahashi N, Murphy K, Wenocur AS, et al. Rare structural variation of synapse and neurotransmission genes in autism. Mol Psychiatry. 2012;17:402–11.PubMed CentralView ArticlePubMedGoogle Scholar
- Pinto D, Pagnamenta AT, Klei L, Anney R, Merico D, Regan R, et al. Functional impact of global rare copy number variation in autism spectrum disorders. Nature. 2010;466:368–72.PubMed CentralView ArticlePubMedGoogle Scholar
- Sanders SJ, Ercan-Sencicek AG, Hus V, Luo R, Murtha MT, Moreno-De-Luca D, et al. Multiple recurrent de novo CNVs, including duplications of the 7q11.23 Williams syndrome region, are strongly associated with autism. Neuron. 2011;70:863–85.PubMed CentralView ArticlePubMedGoogle Scholar
- Buxbaum JD, Silverman J, Keddache M, Smith CJ, Hollander E, Ramoz N, et al. Linkage analysis for autism in a subset families with obsessive-compulsive behaviors: evidence for an autism susceptibility gene on chromosome 1 and further support for susceptibility genes on chromosome 6 and 19. Mol Psychiatry. 2004;9:144–50.View ArticlePubMedGoogle Scholar
- International Molecular Genetic Study of Autism Consortium (IMGSAC). A genomewide screen for autism: strong evidence for linkage to chromosomes 2q, 7q, and 16p. Am J Hum Genet. 2001;69:570–81.View ArticleGoogle Scholar
- Zhang C, Frias MA, Mele A, Ruggiu M, Eom T, Marney CB, et al. Integrative modeling defines the nova splicing-regulatory network and its combinatorial controls. Science. 2010;329:439–43.PubMed CentralView ArticlePubMedGoogle Scholar
- Voineagu I, Wang X, Johnston P, Lowe JK, Tian Y, Horvath S, et al. Transcriptomic analysis of autistic brain reveals convergent molecular pathology. Nature. 2011;474:380–4.PubMed CentralView ArticlePubMedGoogle Scholar
- Weyn-Vanhentenryck SM, Mele A, Yan Q, Sun S, Farny N, Zhang Z, et al. HITS-CLIP and integrative modeling define the Rbfox splicing-regulatory network linked to brain development and autism. Cell Reports. 2014;6:1139–52.PubMed CentralView ArticlePubMedGoogle Scholar
- Nakahata S, Kawamoto S. Tissue-dependent isoforms of mammalian Fox-1 homologs are associated with tissue-specific splicing activities. Nucleic Acids Res. 2005;33:2078–89.PubMed CentralView ArticlePubMedGoogle Scholar
- Hamada N, Ito H, Iwamoto I, Mizuno M, Morishita R, Inaguma Y, et al. Biochemical and morphological characterization of A2BP1 in neuronal tissue. J Neurosci Res. 2013;91:1303–11.View ArticlePubMedGoogle Scholar
- Kim KK, Kim YC, Adelstein RS, Kawamoto S. Fox-3 and PSF interact to activate neural cell-specific alternative splicing. Nucleic Acids Res. 2011;39:3064–78.PubMed CentralView ArticlePubMedGoogle Scholar
- Konno D, Shioi G, Shitamukai A, Mori A, Kiyonari H, Miyata T, et al. Neuroepithelial progenitors undergo LGN-dependent planar divisions to maintain self-renewability during mammalian neurogenesis. Nat Cell Biol. 2007;10:93–101.View ArticlePubMedGoogle Scholar
- Kawabata I, Umeda T, Yamamoto K, Okabe S. Electroporation-mediated gene transfer system applied to cultured CNS neurons. Neuroreport. 2004;15:971–5.View ArticlePubMedGoogle Scholar
- Koresawa Y, Miyagawa S, Ikawa M, Matsunami K, Yamada M, Shirakura R, et al. Synthesis of a new Cre recombinase gene based on optimal codon usage for mammalian systems. J Biochem. 2000;127:367–72.View ArticlePubMedGoogle Scholar
- Nishitsuji H, Ikeda T, Miyoshi H, Ohashi T, Kannagi M, Masuda T. Expression of small hairpin RNA by lentivirus-based vector confers efficient and stable gene-suppression of HIV-1 on human cells including primary non-dividing cells. Microbes Infect. 2004;6:76–85.View ArticlePubMedGoogle Scholar
- Hanai N, Nagata K-I, Kawajiri A, Shiromizu T, Saitoh N, Hasegawa Y, et al. Biochemical and cell biological characterization of a mammalian septin, Sept11. FEBS Lett. 2004;568:83–8.View ArticlePubMedGoogle Scholar
- Nagata K-I, Ito H, Iwamoto I, Morishita R, Asano T. Interaction of a multi-domain adaptor protein, vinexin, with a Rho-effector, Rhotekin. Med Mol Morphol. 2009;42:9–15.View ArticlePubMedGoogle Scholar
- Shinoda T, Ito H, Sudo K, Iwamoto I, Morishita R, Nagata K-I. Septin 14 is involved in cortical neuronal migration via interaction with septin 4. Mol Biol Cell. 2010;21:1324–34.PubMed CentralView ArticlePubMedGoogle Scholar
- Ito H, Morishita R, Shinoda T, Iwamoto I, Sudo K, Okamoto K, et al. Dysbindin-1, WAVE2 and Abi-1 form a complex that regulates dendritic spine formation. Mol Psychiatry. 2010;15:976–86.View ArticlePubMedGoogle Scholar
- Tabata H, Nakajima K. Efficient in utero gene transfer system to the developing mouse brain using electroporation: visualization of neuronal migration in the developing cortex. Neuroscience. 2001;103:865–72.View ArticlePubMedGoogle Scholar
- Inaguma Y, Hamada N, Tabata H, Iwamoto I, Mizuno M, Nishimura YV, et al. SIL1, a causative cochaperone gene of Marinesco-Sjogren syndrome, plays an essential role in establishing the architecture of the developing cerebral cortex. EMBO Mol Med. 2014;6:414–29.PubMed CentralView ArticlePubMedGoogle Scholar
- Uchino S, Hirasawa T, Tabata H, Gonda Y, Waga C, Ondo Y, et al. Inhibition of N-methyl-d-aspartate receptor activity resulted in aberrant neuronal migration caused by delayed morphological development in the mouse neocortex. Neuroscience. 2010;169:609–18.View ArticlePubMedGoogle Scholar
- Tsai L-H, Gleeson JG. Nucleokinesis in neuronal migration. Neuron. 2005;46:383–8.View ArticlePubMedGoogle Scholar
- Nadarajah B, Brunstrom JE, Grutzendler J, Wong RO, Pearlman AL. Two modes of radial migration in early development of the cerebral cortex. Nat Neurosci. 2001;4:143–50.View ArticlePubMedGoogle Scholar
- Friocourt G, Kanatani S, Tabata H, Yozu M, Takahashi T, Antypa M, et al. Cell-autonomous roles of ARX in cell proliferation and neuronal migration during corticogenesis. J Neurosci. 2008;28:5794–805.View ArticlePubMedGoogle Scholar
- Berg JM, Geschwind DH. Autism genetics: searching for specificity and convergence. Genome Biol. 2012;13:247.PubMed CentralView ArticlePubMedGoogle Scholar
- Hammock EAD, Levitt P. Developmental expression mapping of a gene implicated in multiple neurodevelopmental disorders, A2bp1 (Fox1). Dev Neurosci. 2011;33:64–74.PubMed CentralView ArticlePubMedGoogle Scholar
- Fogel BL, Wexler E, Wahnich A, Friedrich T, Vijayendran C, Gao F, et al. RBFOX1 regulates both splicing and transcriptional networks in human neuronal development. Hum Mol Gen. 2012;21:4171–86.PubMed CentralView ArticlePubMedGoogle Scholar
- Prandini P, Zusi C, Malerba G, Itan, Pignatti PF, Trabetti E. Analysis of RBFOX1 gene expression in lymphoblastoid cell lines of Italian discordant autism spectrum disorders sib-pairs. Mol Cell Probes. 2014;28:242–5.View ArticlePubMedGoogle Scholar
- Shyu AB, Wilkinson MF. The double lives of shuttling mRNA binding proteins. Cell. 2000;102:135–8.View ArticlePubMedGoogle Scholar
- Dreyfuss G, Kim VN, Kataoka N. Messenger-RNA-binding proteins and the messages they carry. Nat Rev Mol Cell Biol. 2002;3:195–205.View ArticlePubMedGoogle Scholar