Correlations of Behavioral Deficits with Brain Pathology Assessed through Longitudinal MRI and Histopathology in the R6/2 Mouse Model of HD

Huntington's disease (HD) is caused by the expansion of a CAG repeat in the huntingtin (HTT) gene. The R6/2 mouse model of HD expresses a mutant version of exon 1 HTT and develops motor and cognitive impairments, a widespread huntingtin (HTT) aggregate pathology and brain atrophy. Despite the vast number of studies that have been performed on this model, the association between the molecular and cellular neuropathology with brain atrophy, and with the development of behavioral phenotypes remains poorly understood. In an attempt to link these factors, we have performed longitudinal assessments of behavior (rotarod, open field, passive avoidance) and of regional brain abnormalities determined through magnetic resonance imaging (MRI) (whole brain, striatum, cortex, hippocampus, corpus callosum), as well as an end-stage histological assessment. Detailed correlative analyses of these three measures were then performed. We found a gender-dependent emergence of motor impairments that was associated with an age-related loss of regional brain volumes. MRI measurements further indicated that there was no striatal atrophy, but rather a lack of striatal growth beyond 8 weeks of age. T2 relaxivity further indicated tissue-level changes within brain regions. Despite these dramatic motor and neuroanatomical abnormalities, R6/2 mice did not exhibit neuronal loss in the striatum or motor cortex, although there was a significant increase in neuronal density due to tissue atrophy. The deposition of the mutant HTT (mHTT) protein, the hallmark of HD molecular pathology, was widely distributed throughout the brain. End-stage histopathological assessments were not found to be as robustly correlated with the longitudinal measures of brain atrophy or motor impairments. In conclusion, modeling pre-manifest and early progression of the disease in more slowly progressing animal models will be key to establishing which changes are causally related. © 2013 Rattray et al

Molecular neuroanatomy: mouse-human homologies and the landscape of genes implicated in language disorders

The distinctiveness of brain structures and circuits depends on interacting gene products, yet the organization of these molecules (the "transcriptome") within and across brain areas remains unclear. High-throughput, neuroanatomically-specific gene expression datasets such as the Allen Human Brain Atlas (AHBA) and Allen Mouse Brain Atlas (AMBA) have recently become available, providing unprecedented opportunities to quantify molecular neuroanatomy. This dissertation seeks to clarify how transcriptomic organization relates to conventional neuroanatomy within and across species, and to introduce the use of gene expression data as a bridge between genotype and phenotype in complex behavioral disorders. The first part of this work examines large-scale, regional transcriptomic organization separately in the mouse and human brain. The use of dimensionality reduction methods and cross-sample correlations both revealed greater similarity between samples drawn from the same brain region. Sample profiles and differentially expressed genes across regions in the human brain also showed consistent anatomical specificity in a second human dataset with distinct sampling properties. The frequent use of mouse models in clinical research points to the importance of comparing molecular neuroanatomical organization across species. The second part of this dissertation describes three comparative approaches. First, at genome scale, expression profiles within homologous brain regions tended to show higher similarity than those from non-homologous regions, with substantial variability across regions. Second, gene subsets (defined using co-expression relationships or shared annotations), which provide region-specific, cross-species molecular signatures were identified. Finally, brain-wide expression patterns of orthologous genes were compared. Neuron and oligodendrocyte markers were more correlated than expected by chance, while astrocyte markers were less so. The localization and co-expression of genes reflect functional relationships that may underlie high-level functions. The final part of this dissertation describes a database of genes that have been implicated in speech and language disorders, and identifies brain regions where they are preferentially expressed or co-expressed. Several brain structures with functions relevant to four speech and language disorders showed co-expression of genes associated with these disorders. In particular, genes associated with persistent developmental stuttering showed stronger preferential co-expression in the basal ganglia, a structure of known importance in this disorder

Different pathways of molecular pathophysiology underlie cognitive and motor tauopathy phenotypes in transgenic models for Alzheimer’s disease and frontotemporal lobar degeneration

Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. Acknowledgments From the Berlin Laboratory, we thank Ingo Voigt for performing the injections of the two constructs into the oocytes, Bettina Seelhorst for her extensive technical assistance, Anna Thoma for taking specific care of the animals, and John Horn, Charite Core Facility for electron microscopy for performing expert analyses in ultra-cryosections with immunogold technique. Expert comments on the manuscript from Silke Frahm-Barske (Berlin) are also acknowledged. Special thanks to Bob Switzer at NeuroScience Associates Inc. for embedding, sectioning and staining mouse brains. This work was funded by TauRx Therapeutics, Singapore. C.R.H. and C.M.W. declare that they are officers in TauRx Therapeutics Ltd.Peer reviewedPublisher PD

Relationships between Gene Expression and Brain Wiring in the Adult Rodent Brain

We studied the global relationship between gene expression and neuroanatomical connectivity in the adult rodent brain. We utilized a large data set of the rat brain “connectome” from the Brain Architecture Management System (942 brain regions and over 5000 connections) and used statistical approaches to relate the data to the gene expression signatures of 17,530 genes in 142 anatomical regions from the Allen Brain Atlas. Our analysis shows that adult gene expression signatures have a statistically significant relationship to connectivity. In particular, brain regions that have similar expression profiles tend to have similar connectivity profiles, and this effect is not entirely attributable to spatial correlations. In addition, brain regions which are connected have more similar expression patterns. Using a simple optimization approach, we identified a set of genes most correlated with neuroanatomical connectivity, and find that this set is enriched for genes involved in neuronal development and axon guidance. A number of the genes have been implicated in neurodevelopmental disorders such as autistic spectrum disorder. Our results have the potential to shed light on the role of gene expression patterns in influencing neuronal activity and connectivity, with potential applications to our understanding of brain disorders. Supplementary data are available at http://www.chibi.ubc.ca/ABAMS

Neuropsühhiaatriliste endofenotüüpide seos IgLON adhesioonimolekulidega hiire ajus

Väitekirja elektrooniline versioon ei sisalda publikatsioonePsühhiaatriliste häirete multifaktoriaalse patogeneesi mõistmine on suur väljakutse. Neuropsühhiaatriliste häirete modelleerimine loommudelites annab võimaluse uurida, kuidas närviringete düsfunktsionaalsus põhjustab patoloogiliste fenotüüpide avaldumist. Erinevad ülegenoomsed assotsiatsiooniuuringud (GWAS) ning ekspressiooniuuringud on näidanud IgLON perekonda kuuluvate adhesioonimolekulide (Lsamp, Ntm, Opcml, Negr1, IgLON 5) seost inimese neuropsühhiaatriliste häiretega ning käitumiskatsed Lsamp ja Ntm puudulike hiirtega on näidanud IgLON molekulide osalust emotsionaalse ja sotsiaalse käitumise kujunemises. Funktsionaalsed uuringud on näidanud, et IgLON valgud osalevad närviringete kujunemisel ja toimimisel nii arenevas kui ka täiskasvanud ajus. On teada, et tsütoskeleti dünaamilised ümberkorraldused arenevates neuronites on aluseks neuraalsete ringete kujunemisele, kuid IgLON perekonna molekulide roll arenevate neuronite tsütoskeleti reguleerimises on olnud siiani teadmata. Käesoleva töö eesmärk oli selgitada Lsamp ja Ntm vaheliste vastastoimete ja Negr1 mõju aju struktuurile ja funktsioonidele, kasutades vastavate geenide suhtes mutantseid hiiremudeleid. Analüüsisime neuropsühhiaatriliste häiretega seotud morfoloogilisi, anatoomilisi ja käitumuslikke parameetreid Lsamp−/−, Ntm−/−, Lsamp−/−Ntm−/− ja Negr1−/− hiirtes. Mitmetasandiline lähenemine aitab selgitada, kuidas aju struktuursed kõrvalekalded mõjutavad käitumist. Näitasime, et Lsamp ja Ntm mõjutavad varajast neuriitide väljakasvu ja rakkude jagunemist ning apoptoosi teineteisest sõltuvalt ning samasugused vastasmõjud on jälgitavad ka mutanthiirte käitumuslikes reaktsioonides. Leidsime, et Negr1−/− hiirtel on kõrvalekalded neuritogeneesis, neuroanatoomias ja et nende hipokampuses on vähem inhibitoorseid neuroneid, mis võivad olla sellele hiireliinile iseloomuliku puuduliku sotsiaalse ja tunnetusliku käitumise põhjuseks. Lisaks näitavad käesoleva väitekirja tulemused, et IgLON adhesioonimolekulide toime võib olla sõltumatu rakkudevahelisest adhesioonist. Meie uurimistulemused aitavad mõista, kuidas IgLON adhesioonivalgud, mille geenipiirkonnad on olulised riskilookused paljudele psühhiaatrilistele häiretele, reguleerivad närviringete kujunemist, mõjutades neuronite morfoloogiat ja omadusi ning aju anatoomiat. Neid neuronaalseid muutusi, mis seostuvad muutustega käitumises, võib vaadata kui psühhiaatriliste häiretega seotud endofenotüüpe. Oleme näidanud erinevate IgLON puudulikkusega hiiremudelite sobivust psühhiaatriliste häirete modelleerimiseks ning nende mudelite edasine uurimine aitab neuropsühhiaatriliste häirete kujunemist paremini mõista.Understanding the multifactorial pathogenesis of neuropsychiatric disorders is a considerable challenge. Modelling neuropsychiatric disorders in animals provides us a medium to explore the endophenotypes of these disorders to understand how malfunctioning neuronal circuits manifest as pathological phenotypes. Several genome wide association studies (GWAS) and expression studies have linked IgLON superfamily of cell adhesion molecules (Lsamp, Ntm, Opcml, Negr1, IgLON 5) with neuropsychiatric disorders in humans. Analyses of Lsamp and Ntm deficient mice have shown that these genes are involved in patterning of emotional and social behavior. During development, IgLON cell adhesion molecules assist fundamental neuronal communication and the establishment of circuits through morphological changes in the developing neurons, driven by dynamic rearrangements of the cytoskeleton. The role of IgLON molecules in cytoskeletal regulation during development has remained unknown until now. The goal of the present study was to address the effect of interaction between Lsamp and Ntm and the impact of Negr1 on brain structure and function using deletional mouse models. We studied morphological, anatomical and behavioral parameters related to endophenotypes of neuropsychiatric disorders in Lsamp−/−, Ntm−/−, Lsamp−/−Ntm−/− and Negr1−/− mice. This approach allowed us to gain insight into how structural alterations in the brain can influence manifestations at the behavioral level. We showed that Lsamp and Ntm adhesion molecules interact mutually with each other to coordinate early neurite sprouting, proliferation and apoptosis, which manifest at behavior in adult. Our observation on Negr1−/− mice revealed alterations in neuritogenesis and neuroanatomy, and reduced number of inhibitory interneurons in the hippocampus that may underlie the aberrant social and cognitive behavior. Additionally, we propose that the function of IgLON molecules can exhibit through cell autonomous mechanisms during initiation of neurite sprouting independent of cell-adhesion functions. Our findings expand the understanding of how IgLONs, which are candidate genes for a wide spectrum of psychiatric disorders, are involved in the regulation of neuronal circuits at the level of neuronal morphology and neuronal properties, and how they consequently impact the structural anatomy of the brain. These neuronal alterations that manifest as behavioral alterations can be viewed as endophenotypes of neuropsychiatric disorders. We have demonstrated the suitability of IgLON-deficient mice as models for psychiatric disorders. The future investigation of these models enables better understanding of the pathogenesis and treatment of neuropsychiatric disordershttps://www.ester.ee/record=b524318

Co-expression Profiling of Autism Genes in the Mouse Brain

Autism spectrum disorder (ASD) is one of the most prevalent and highly heritable neurodevelopmental disorders in humans. There is significant evidence that the onset and severity of ASD is governed in part by complex genetic mechanisms affecting the normal development of the brain. To date, a number of genes have been associated with ASD. However, the temporal and spatial co-expression of these genes in the brain remain unclear. To address this issue, we examined the co-expression network of 26 autism genes from AutDB (http://mindspec.org/autdb.html), in the framework of 3,041 genes whose expression energies have the highest correlation between the coronal and sagittal images from the Allen Mouse Brain Atlas database (http://mouse.brain-map.org). These data were derived from in situ hybridization experiments conducted on male, 56-day old C57BL/6J mice co-registered to the Allen Reference Atlas, and were used to generate a normalized co-expression matrix indicating the cosine similarity between expression vectors of genes in this database. The network formed by the autism-associated genes showed a higher degree of co-expression connectivity than seen for the other genes in this dataset (Kolmogorov–Smirnov P = 5×10−28). Using Monte Carlo simulations, we identified two cliques of co-expressed genes that were significantly enriched with autism genes (A Bonferroni corrected P<0.05). Genes in both these cliques were significantly over-expressed in the cerebellar cortex (P = 1×10−5) suggesting possible implication of this brain region in autism. In conclusion, our study provides a detailed profiling of co-expression patterns of autism genes in the mouse brain, and suggests specific brain regions and new candidate genes that could be involved in autism etiology

Mapping Genetically Controlled Neural Circuits of Social Behavior and Visuo-Motor Integration by a Preliminary Examination of Atypical Deletions with Williams Syndrome

In this study of eight rare atypical deletion cases with Williams-Beuren syndrome (WS; also known as 7q11.23 deletion syndrome) consisting of three different patterns of deletions, compared to typical WS and typically developing (TD) individuals, we show preliminary evidence of dissociable genetic contributions to brain structure and human cognition. Univariate and multivariate pattern classification results of morphometric brain patterns complemented by behavior implicate a possible role for the chromosomal region that includes: 1) GTF2I/GTF2IRD1 in visuo-spatial/motor integration, intraparietal as well as overall gray matter structures, 2) the region spanning ABHD11 through RFC2 including LIMK1, in social cognition, in particular approachability, as well as orbitofrontal, amygdala and fusiform anatomy, and 3) the regions including STX1A, and/or CYLN2 in overall white matter structure. This knowledge contributes to our understanding of the role of genetics on human brain structure, cognition and pathophysiology of altered cognition in WS. The current study builds on ongoing research designed to characterize the impact of multiple genes, gene-gene interactions and changes in gene expression on the human brain

Geometry Processing of Conventionally Produced Mouse Brain Slice Images

Brain mapping research in most neuroanatomical laboratories relies on conventional processing techniques, which often introduce histological artifacts such as tissue tears and tissue loss. In this paper we present techniques and algorithms for automatic registration and 3D reconstruction of conventionally produced mouse brain slices in a standardized atlas space. This is achieved first by constructing a virtual 3D mouse brain model from annotated slices of Allen Reference Atlas (ARA). Virtual re-slicing of the reconstructed model generates ARA-based slice images corresponding to the microscopic images of histological brain sections. These image pairs are aligned using a geometric approach through contour images. Histological artifacts in the microscopic images are detected and removed using Constrained Delaunay Triangulation before performing global alignment. Finally, non-linear registration is performed by solving Laplace's equation with Dirichlet boundary conditions. Our methods provide significant improvements over previously reported registration techniques for the tested slices in 3D space, especially on slices with significant histological artifacts. Further, as an application we count the number of neurons in various anatomical regions using a dataset of 51 microscopic slices from a single mouse brain. This work represents a significant contribution to this subfield of neuroscience as it provides tools to neuroanatomist for analyzing and processing histological data.Comment: 14 pages, 11 figure