Asami Oguro-Ando

Contactins in the neurobiology of autism

Autism is a disease of brain plasticity. Inspiring work of Willem Hendrik Gispen on neuronal plasticity has stimulated us to investigate gene defects in autism and the consequences for brain development. The central process in the pathogenesis of autism is local dendritic mRNA translation which is dependent on axodendritic communication. Hence, most autism-related gene products (i) are part of the protein synthesis machinery itself, (ii) are components of the mTOR signal transduction pathway, or (iii) shape synaptic activity and plasticity. Accordingly, prototype drugs have been recognized that interfere with these pathways. The contactin (CNTN) family of Ig cell adhesion molecules (IgCAMs) harbours at least three members that have genetically been implicated in autism: CNTN4, CNTN5, and CNTN6. In this chapter we review the genetic and neurobiological data underpinning their role in normal and abnormal development of brain systems, and the consequences for behavior. Although data on each of these CNTNs are far from complete, we tentatively conclude that these three contactins play roles in brain development in a critical phase of establishing brain systems and their plasticity. They modulate neuronal activities, such as neurite outgrowth, synaptogenesis, survival, guidance of projections and terminal branching of axons in forming neural circuits. Current research on these CNTNs concentrate on the neurobiological mechanism of their developmental functions. A future task will be to establish if proposed pharmacological strategies to counteract ASD-related symptomes can also be applied to reversal of phenotypes caused by genetic defects in these CNTN genes.

Increased CYFIP1 dosage alters cellular and dendritic morphology and dysregulates mTOR.

Rare maternally inherited duplications at 15q11-13 are observed in ~1% of individuals with an autism spectrum disorder (ASD), making it among the most common causes of ASD. 15q11-13 comprises a complex region, and as this copy number variation encompasses many genes, it is important to explore individual genotype–phenotype relationships. Cytoplasmic FMR1-interacting protein 1 (CYFIP1) is of particular interest because of its interaction with Fragile X mental retardation protein (FMRP), its upregulation in transformed lymphoblastoid cell lines from patients with duplications at 15q11-13 and ASD and the presence of smaller overlapping deletions of CYFIP1 in patients with schizophrenia and intellectual disability. Here, we confirm that CYFIP1 is upregulated in transformed lymphoblastoid cell lines and demonstrate its upregulation in the post-mortem brain from 15q11-13 duplication patients for the first time. To investigate how increased CYFIP1 dosage might predispose to neurodevelopmental disease, we studied the consequence of its overexpression in multiple systems. We show that overexpression of CYFIP1 results in morphological abnormalities including cellular hypertrophy in SY5Y cells and differentiated mouse neuronal progenitors. We validate these results in vivo by generating a BAC transgenic mouse, which overexpresses Cyfip1 under the endogenous promotor, observing an increase in the proportion of mature dendritic spines and dendritic spine density. Gene expression profiling on embryonic day 15 suggested the dysregulation of mammalian target of rapamycin (mTOR) signaling, which was confirmed at the protein level. Importantly, similar evidence of mTOR-related dysregulation was seen in brains from 15q11-13 duplication patients with ASD. Finally, treatment of differentiated mouse neuronal progenitors with an mTOR inhibitor (rapamycin) rescued the morphological abnormalities resulting from CYFIP1 overexpression. Together, these data show that CYFIP1 overexpression results in specific cellular phenotypes and implicate modulation by mTOR signaling, further emphasizing its role as a potential convergent pathway in some forms of ASD.

A current view on contactin-4, -5, and -6 : Implications in neurodevelopmental disorders

Abstract Contactins (Cntns) are a six‐member subgroup of the immunoglobulin cell adhesion molecule superfamily (IgCAMs) with pronounced brain expression and function. Recent genetic studies of neuropsychiatric disorders have pinpointed contactin‐4 (CNTN4), contactin‐5 (CNTN5) and contactin‐6 (CNTN6) as candidate genes in neurodevelopmental disorders, particularly in autism spectrum disorders (ASDs), but also in intellectual disability, schizophrenia (SCZ), attention‐deficit hyperactivity disorder (ADHD), bipolar disorder (BD), alcohol use disorder (AUD) and anorexia nervosa (AN). This suggests that they have important functions during neurodevelopment. This suggestion is supported by data showing that neurite outgrowth, cell survival and neural circuit formation can be affected by disruption of these genes. Here, we review the current genetic data about their involvement in neuropsychiatric disorders and explore studies on how null mutations affect mouse behavior. Finally, we highlight to role of protein–protein interactions in the potential mechanism of action of Cntn4, ‐5 and ‐6 and emphasize that complexes with other membrane proteins may play a role in neuronal developmental functions. Graphical abstract Figure. No Caption available. HighlightsContactin‐4, ‐5, and ‐6 have been implicated in neurodevelopmental disorders by genetic studies.Null mutation of contactin‐4, ‐5 and ‐6 cause developmental abnormalities in specific and distinct brain systems.The mode of action of contactin‐4, ‐5 and ‐6 involves the formation of functional heterodimeric complexes.

JAKMIP1, a Novel Regulator of Neuronal Translation, Modulates Synaptic Function and Autistic-like Behaviors in Mouse.

Autism spectrum disorder (ASD) is a heritable, common neurodevelopmental disorder with diverse genetic causes. Several studies have implicated protein synthesis as one among several of its potential convergent mechanisms. We originally identified Janus kinase and microtubule-interacting protein 1 (JAKMIP1) as differentially expressed in patients with distinct syndromic forms of ASD, fragile X syndrome, and 15q duplication syndrome. Here, we provide multiple lines of evidence that JAKMIP1 is a component of polyribosomes and an RNP translational regulatory complex that includes fragile X mental retardation protein, DEAD box helicase 5, and the poly(A) binding protein cytoplasmic 1. JAKMIP1 loss dysregulates neuronal translation during synaptic development, affecting glutamatergic NMDAR signaling, and results in social deficits, stereotyped activity, abnormal postnatal vocalizations, and other autistic-like behaviors in the mouse. These findings define an important and novel role for JAKMIP1 in neural development and further highlight pathways regulating mRNA translation during synaptogenesis in the genesis of neurodevelopmental disorders.

Genetic mapping in mice reveals the involvement of Pcdh9 in long-term social and object recognition and sensorimotor development

BACKGROUND Quantitative genetic analysis of basic mouse behaviors is a powerful tool to identify novel genetic phenotypes contributing to neurobehavioral disorders. Here, we analyzed genetic contributions to single-trial, long-term social and nonsocial recognition and subsequently studied the functional impact of an identified candidate gene on behavioral development. METHODS Genetic mapping of single-trial social recognition was performed in chromosome substitution strains, a sophisticated tool for detecting quantitative trait loci (QTL) of complex traits. Follow-up occurred by generating and testing knockout (KO) mice of a selected QTL candidate gene. Functional characterization of these mice was performed through behavioral and neurological assessments across developmental stages and analyses of gene expression and brain morphology. RESULTS Chromosome substitution strain 14 mapping studies revealed an overlapping QTL related to long-term social and object recognition harboring Pcdh9, a cell-adhesion gene previously associated with autism spectrum disorder. Specific long-term social and object recognition deficits were confirmed in homozygous (KO) Pcdh9-deficient mice, while heterozygous mice only showed long-term social recognition impairment. The recognition deficits in KO mice were not associated with alterations in perception, multi-trial discrimination learning, sociability, behavioral flexibility, or fear memory. Rather, KO mice showed additional impairments in sensorimotor development reflected by early touch-evoked biting, rotarod performance, and sensory gating deficits. This profile emerged with structural changes in deep layers of sensory cortices, where Pcdh9 is selectively expressed. CONCLUSIONS This behavior-to-gene study implicates Pcdh9 in cognitive functions required for long-term social and nonsocial recognition. This role is supported by the involvement of Pcdh9 in sensory cortex development and sensorimotor phenotypes.

Developmental role of the cell adhesion molecule Contactin-6 in the cerebral cortex and hippocampus

ABSTRACT The gene encoding the neural cell adhesion molecule Contactin-6 (Cntn6 a.k.a. NB-3) has been implicated as an autism risk gene, suggesting that its mutation is deleterious to brain development. Due to its GPI-anchor at Cntn6 may exert cell adhesion/receptor functions in complex with other membrane proteins, or serve as a ligand. We aimed to uncover novel phenotypes related to Cntn6 functions during development in the cerebral cortex of adult Cntn6−/− mice. We first determined Cntn6 protein and mRNA expression in the cortex, thalamic nuclei and the hippocampus at P14, which decreased specifically in the cortex at adult stages. Neuroanatomical analysis demonstrated a significant decrease of Cux1+ projection neurons in layers II-IV and an increase of FoxP2+ projection neurons in layer VI in the visual cortex of adult Cntn6−/− mice compared to wild-type controls. Furthermore, the number of parvalbumin+ (PV) interneurons was decreased in Cntn6−/− mice, while the amount of NPY+ interneurons remained unchanged. In the hippocampus the delineation and outgrowth of mossy fibers remained largely unchanged, except for the observation of a larger suprapyramidal bundle. The observed abnormalities in the cerebral cortex and hippocampus of Cntn6−/− mice suggests that Cntn6 serves developmental functions involving cell survival, migration and fasciculation. Furthermore, these data suggest that Cntn6 engages in both trans- and cis-interactions and may be involved in larger protein interaction networks.

Association of Cell Adhesion Molecules Contactin-6 and Latrophilin-1 Regulates Neuronal Apoptosis

[This corrects the article on p. 143 in vol. 9, PMID: 28018171.].

Toll-interacting protein pathway: degradation of an ubiquitin-binding protein.

The nine neurodegenerative disorders including Huntington disease (HD) are caused by the expansion of a trinucleotide CAG repeats (polyQ), which are located within the coding of the affected gene. Previous studies suggested that a gain of toxic function by polyQ repeats is widely thought to have a major role in pathogenesis. PolyQ-expanded htt induced ubiquitinated aggregates cause cell death in neuronal cells. Using a HD cellular model, we demonstrate that Tollip protects cells against the toxicity of polyQ-expanded htt and also protects cells from death (Oguro, Kubota, Shimizu, Ishiura, & Atomi, 2011). Tom1 which belongs to the VHS domain-containing protein family is also found to be directly binding to ubiquitin chains and Tollip (Katoh et al., 2004; Yamakami, Yoshimori, & Yokosawa, 2003). Tollip recruits misfolded protein to aggresome via late endosome. The cell system can be used to determine if your protein of interest is controlled under a part of Tollip pathway or not among other cell homeostatic systems: molecular chaperons, autophagy, and endoplasmic reticulum (ER)-associated degradation (ERAD). Tollip can be used for polyQ cell toxicity sensor by detecting microtubule-dependent trafficking and aggresome colocalization of aggregated protein.

CD38 is Required for Dendritic Organization in Visual Cortex and Hippocampus

Morphological screening of mouse brains with known behavioral deficits can give great insight into the relationship between brain regions and their behavior. Oxytocin- and CD38-deficient mice have previously been shown to have behavioral phenotypes, such as restrictions in social memory, social interactions, and maternal behavior. CD38 is reported as an autism spectrum disorder (ASD) candidate gene and its behavioral phenotypes may be linked to ASD. To address whether these behavioral phenotypes relate to brain pathology and neuronal morphology, here we investigate the morphological changes in the CD38-deficient mice brains, with focus on the pathology and neuronal morphology of the cortex and hippocampus, using Nissl staining, immunohistochemistry, and Golgi staining. No difference was found in terms of cortical layer thickness. However, we found abnormalities in the number of neurons and neuronal morphology in the visual cortex and dentate gyrus (DG). In particular, there were arborisation differences between CD38-/- and CD38+/+ mice in the apical dendrites of the visual cortex and hippocampal CA1 pyramidal neurons. The data suggest that CD38 is implicated in appropriate development of brain regions important for social behavior.

S.12.04 Deletion of contactin-4 leads to cognitive rigidity and aberrant cortex development in mice

Cognitive rigidity is a defining characteristic of various psychiatric disorders, such as autism spectrum disorders (ASD) and anorexia nervosa (AN). For instance, reversal learning is considered a core component of cognitive rigidity, a behavioral domain affected in both ASD and AN. Genetic factors that are implicated in both these disorders, such as the contactin-4 (CNTN4) gene, may be particularly relevant to understand how rigidity is mediated [1]. Here, we performed an extensive developmental behavioral and morphological characterization of Cntn4-knockout mice [2]. Cognitive rigidity was assessed in adulthood using the set-shifting task, a mouse analog of the Wisconsin Card Sorting Test. This task includes intra-dimensional (affective) and extra-dimensional (attentional) set-shifting [3]. We found that mice lacking the Cntn4 gene made significantly more errors before reaching the criterion for intra-dimensional set-shifting compared to wild type mice. In contrast, no effect was found on extra-dimensional set-shifting. Moreover, no genotype effects were detected in the longitudinal assessment of general health measures and other behavioral domains. Brain morphology analyses revealed a significant reduction of cortical layer thickness in the motor cortex, but not in nonfrontal areas, including somatosensory cortex and visual cortex. Our results in Cntn4-knockout mice confirm a specific role for this gene in the regulation of cognitive rigidity. Taken together, these findings suggest that this mouse model is highly suitable to examine neurobiological underpinnings of cognitive rigidity in neurodevelopmental disorders. Ultimately, this approach may lead to the development of therapeutic strategies with cross-diagnostic relevance.