Pcdhβ deficiency affects hippocampal CA1 ensemble activity and contextual fear discrimination

Clustered protocadherins (Pcdhs), a large group of adhesion molecules, are important for axonal projections and dendritic spread, but little is known about how they influence neuronal activity. The Pcdhβ cluster is strongly expressed in the hippocampus, and in vivo Ca2+ imaging in Pcdhβ-deficient mice revealed altered activity of neuronal ensembles but not of individual cells in this region in freely moving animals. Specifically, Pcdhβ deficiency increased the number of large-size neuronal ensembles and the proportion of cells shared between ensembles. Furthermore, Pcdhβ-deficient mice exhibited reduced repetitive neuronal population activity during exploration of a novel context and were less able to discriminate contexts in a contextual fear conditioning paradigm. These results suggest that one function of Pcdhβs is to modulate neural ensemble activity in the hippocampus to promote context discrimination

Snf2h Primes UL Neuron Production

Alterations in the homeostasis of either cortical progenitor pool, namely the apically located radial glial (RG) cells or the basal intermediate progenitors (IPCs) can severely impair cortical neuron production. Such changes are reflected by microcephaly and are often associated with cognitive defects. Genes encoding epigenetic regulators are a frequent cause of intellectual disability and many have been shown to regulate progenitor cell growth, including our inactivation of the Smarca1 gene encoding Snf2l, which is one of two ISWI mammalian orthologs. Loss of the Snf2l protein resulted in dysregulation of Foxg1 and IPC proliferation leading to macrocephaly. Here we show that inactivation of the closely related Smarca5 gene encoding the Snf2h chromatin remodeler is necessary for embryonic IPC expansion and subsequent specification of callosal projection neurons. Telencephalon-specific Smarca5 cKO embryos have impaired cell cycle kinetics and increased cell death, resulting in fewer Tbr2+ and FoxG1+ IPCs by mid-neurogenesis. These deficits give rise to adult mice with a dramatic reduction in Satb2C upper layer neurons, and partial agenesis of the corpus callosum. Mice survive into adulthood but molecularly display reduced expression of the clustered protocadherin genes that may further contribute to altered dendritic arborization and a hyperactive behavioral phenotype. Our studies provide novel insight into the developmental function of Snf2h-dependent chromatin remodeling processes during brain development

Dysregulated protocadherin-pathway activity as an intrinsic defect in induced pluripotent stem cell-derived cortical interneurons from subjects with schizophrenia.

We generated cortical interneurons (cINs) from induced pluripotent stem cells derived from 14 healthy controls and 14 subjects with schizophrenia. Both healthy control cINs and schizophrenia cINs were authentic, fired spontaneously, received functional excitatory inputs from host neurons, and induced GABA-mediated inhibition in host neurons in vivo. However, schizophrenia cINs had dysregulated expression of protocadherin genes, which lie within documented schizophrenia loci. Mice lacking protocadherin-α showed defective arborization and synaptic density of prefrontal cortex cINs and behavioral abnormalities. Schizophrenia cINs similarly showed defects in synaptic density and arborization that were reversed by inhibitors of protein kinase C, a downstream kinase in the protocadherin pathway. These findings reveal an intrinsic abnormality in schizophrenia cINs in the absence of any circuit-driven pathology. They also demonstrate the utility of homogenous and functional populations of a relevant neuronal subtype for probing pathogenesis mechanisms during development

A POS-based preordering approach for English-to-Arabic statistical machine translation

In this work, we present a POS-based preordering approach that tackles both long- and short-distance reordering phenomena. Syntactic unlexicalized reordering rules are automatically extracted from a parallel corpus using only word alignment and a source-side language tagging. The reordering rules are used in a deterministic manner; this prevents the decoding speed from being bottlenecked in the reordering procedure. A new approach for both rule filtering and rule application is used to ensure a fast and efficient reordering. The tests performed on the IWSLT2016 English-to-Arabic evaluation benchmark show a noticeable increase in the overall Blue Score for our system over the baseline PSMT system

Somatic mutations of synaptic cadherin (CNR family) transcripts in the nervous system

　中枢神経系と免疫系はともに、未知の環境に対して柔軟に対応できるという点で類似している。しかし、それを担う遺伝子の数には限りがある。これらを可能にする免疫系の分子メカニズムとしては、免疫グロブリンやT細胞受容体をコードする遺伝子の体細胞における再構成や免疫グロブリンにおける体細胞突然変異が知られている。また、抗原に対してより親和性の高い細胞が選択されることが知られている。一方、中枢神経系の機能には、複雑なネットワークつくる多様な神経細胞と可塑的な変化が重要な役割を担うと考えられるが、中枢神経系の多様性をもたらす分子メカニズムは明かとはいえない。　近年、チロシンリン酸化酵素であるFynと結合する分子として同定された多様化したCNRファミリーはシナプスに局在するカドヘリン様の接着分子ある。CNRファミリーは遺伝子構造の解析から可変領域と定常領域とからなり、免疫グロブリンやT細胞受容体の遺伝子構造と似ていることが明らかとなった。彼は、シナプスに発現するCNRファミリー遺伝子の発現メカニズムに免疫系類似の体細胞における変化があるか否かについて中枢神経系の発生にしたがい検討した。はじめにCNRファミリー遺伝子の発現メカニズムを解析する目的でC57BL/6（B6）とDBA/2（D2）の系統の異なるマウスの雑種1代目（F1）の大脳皮質を用いてCNRの転写産物の解析をおこなった。B6とD2とでは、CNR3の遺伝子の可変領域に1つ、定常領域に3つの異なる塩基配列がある。F1マウスの細胞は、B6由来の染色体とD2由来の染色体をそれぞれ1対ずつ持つことになるので通常ならばCNR3の転写産物は可変領域、定常領域ともにB6由来あるいはD2由来のCis型となる。しかし、生後60日目のF1マウスのCNR3転写産物をシークエンス解析した結果、約10％が可変領域がB6由来で定常領域がD2由来あるいはその逆のTrans型として発現していることを明かにした。また、Trans型の転写産物は、胎生15日目（E15）、生後1日目（P1）、生後60日目（P60）と発生が進むにつれて増加することがわかった。　同時に、彼はCNR3転写産物をシークエンス解析することで体細胞突然変異の有無についての検討をおこなった。P60の大脳皮質から抽出したCNR3転写産物には一塩基あたり2.6×10-3という高頻度の塩基置換が検出され、同じくP60の大脳皮質から抽出したE-カドヘリンの転写産物1.3×10-3との比較においても統計学的にも有意に高かった。P60において検出した高頻度の塩基置換が体細胞突然変異であるならば、脳の発生に伴い変異の頻度が変化することが予想された。E15、P1を解析したところ、1.7×10-3、2.4×10-3と発生に伴って増加することが明らかとなった。突然変異は、AからG、TからCへの塩基置換が多く、塩基置換の傾向はランダムではなかった。特に、CNR3の3’末端側の非翻訳領域にあるCU繰り返し配列はgerm lineのDNA配列では6回であるのに対し、P60のCNR3転写産物では約70％が7回のCU繰り返しに変わるという高頻度の変化を認めた。また、Cis型とTrans型の転写産物における突然変異率の比較ではTrans型の方がCis型にくらべて有意に突然変異率が高いことがわかった。これらの結果から、CNR遺伝子の転写産物に体細胞突然変異が起きていることが強く示され、突然変異の起こるメカニズムとTrans型のできるメカニズムに関連があることが示唆された。　興味深いことに、アミノ酸置換を伴う変異率は細胞外領域のEC1ドメインでのみ高頻度で起きているということである。EC1ドメインは、クラシカルなカドヘリンではホモフィリックな細胞接着に重要であることが示されており、CNRでは大脳皮質の層構造形成に重要なReelinと結合することから機能的にも重要な役割を果たしていると考えられている。よって、EC1ドメインのアミノ酸置換はCNRの機能に影響を与えるものと考えられる。一方、その他のドメインではアミノ酸置換を伴う変異率は発生が進むにつれて減少する。このことから、EC1ドメインでアミノ酸置換をおこしたもののうち、他のドメインではアミノ酸置換の少ないCNRが脳の発生に伴って選択されている可能性が示唆された。　本研究は、シナプスで発現するCNR遺伝子の転写産物に体細胞突然変異が起きてることをはじめて示し、何らかの選択機構が働いている可能性を示唆した。CNR遺伝子の転写産物の体細胞突然変異はCNRがシナプスに局在することから神経ネットワークの可塑的な変化を担う分子メカニズムとして興味深い

CTCF Is Required for Neural Development and Stochastic Expression of Clustered Pcdh Genes in Neurons

The CCCTC-binding factor (CTCF) is a key molecule for chromatin conformational changes that promote cellular diversity, but nothing is known about its role in neurons. Here, we produced mice with a conditional knockout (cKO) of CTCF in postmitotic projection neurons, mostly in the dorsal telencephalon. The CTCF-cKO mice exhibited postnatal growth retardation and abnormal behavior and had defects in functional somatosensory mapping in the brain. In terms of gene expression, 390 transcripts were expressed at significantly different levels between CTCF-deficient and control cortex and hippocampus. In particular, the levels of 53 isoforms of the clustered protocadherin (Pcdh) genes, which are stochastically expressed in each neuron, declined markedly. Each CTCF-deficient neuron showed defects in dendritic arborization and spine density during brain development. Their excitatory postsynaptic currents showed normal amplitude but occurred with low frequency. Our results indicate that CTCF regulates functional neural development and neuronal diversity by controlling clustered Pcdh expression

Isoform requirement of clustered protocadherin for preventing neuronal apoptosis and neonatal lethality

Summary: Clustered protocadherin is a family of cell-surface recognition molecules implicated in neuronal connectivity that has a diverse isoform repertoire and homophilic binding specificity. Mice have 58 isoforms, encoded by Pcdhα, β, and γ gene clusters, and mutant mice lacking all isoforms died after birth, displaying massive neuronal apoptosis and synapse loss. The current hypothesis is that the three specific γC-type isoforms, especially γC4, are essential for the phenotype, raising the question about the necessity of isoform diversity. We generated TC mutant mice that expressed the three γC-type isoforms but lacked all the other 55 isoforms. The TC mutants died immediately after birth, showing massive neuronal death, and γC3 or γC4 expression did not prevent apoptosis. Restoring the α- and β-clusters with the three γC alleles rescued the phenotype, suggesting that along with the three γC-type isoforms, other isoforms are also required for the survival of neurons and individual mice

CTCF loss induces giant lamellar bodies in Purkinje cell dendrites

Abstract CCCTC-binding factor (CTCF) has a key role in higher-order chromatin architecture that is important for establishing and maintaining cell identity by controlling gene expression. In the mature cerebellum, CTCF is highly expressed in Purkinje cells (PCs) as compared with other cerebellar neurons. The cerebellum plays an important role in motor function by regulating PCs, which are the sole output neurons, and defects in PCs cause motor dysfunction. However, the role of CTCF in PCs has not yet been explored. Here we found that the absence of CTCF in mouse PCs led to progressive motor dysfunction and abnormal dendritic morphology in those cells, which included dendritic self-avoidance defects and a proximal shift in the climbing fibre innervation territory on PC dendrites. Furthermore, we found the peculiar lamellar structures known as “giant lamellar bodies” (GLBs), which have been reported in PCs of patients with Werdnig-Hoffman disease, 13q deletion syndrome, and Krabbe disease. GLBs are localized to PC dendrites and are assumed to be associated with neurodegeneration. They have been noted, however, only in case reports following autopsy, and reports of their existence have been very limited. Here we show that GLBs were reproducibly formed in PC dendrites of a mouse model in which CTCF was deleted. GLBs were not noted in PC dendrites at infancy but instead developed over time. In conjunction with GLB development in PC dendrites, the endoplasmic reticulum was almost absent around the nuclei, the mitochondria were markedly swollen and their cristae had decreased drastically, and almost all PCs eventually disappeared as severe motor deficits manifested. Our results revealed the important role of CTCF during normal development and in maintaining PCs and provide new insights into the molecular mechanism of GLB formation during neurodegenerative disease