Non-syndromic intellectual disability (NS-ID) is a widespread neurodevelopmental disorder in which the major phenotypic manifestation is low IQ. Given the known genetic overlaps between the two conditions, it was hypothesize that autosomal recessive NS-ID (NS-ARID) genes may also play a role in autism. In this thesis, autism probands with CNVs overlapping NS-ARID genes were screened for additional mutations by sequencing. In addition, TRAPPC9 was identified as a novel cause of NS-ARID in two unrelated consanguineous families. TRAPPC9 (NIBP) is believed to function in the NF-kB pathway and the TRAPP complex. Multiple probands with developmental delays and CNVs overlapping TRAPPC9 were also identified. A potential mechanism for the CNV-related phenotype is that TRAPPC9 may be partially paternally imprinted in brain, and overlapping CNVs may cause loss of regulation. Identification of genes for autism and ID will translate into earlier diagnosis and better clinical care for this population in the future.

Non-syndromic intellectual disability (NS-ID) is a widespread neurodevelopmental disorder in which the major phenotypic manifestation is low IQ. Given the known genetic overlaps between the two conditions, it was hypothesize that autosomal recessive NS-ID (NS-ARID) genes may also play a role in autism. In this thesis, autism probands with CNVs overlapping NS-ARID genes were screened for additional mutations by sequencing. In addition, TRAPPC9 was identified as a novel cause of NS-ARID in two unrelated consanguineous families. TRAPPC9 (NIBP) is believed to function in the NF-kB pathway and the TRAPP complex. Multiple probands with developmental delays and CNVs overlapping TRAPPC9 were also identified. A potential mechanism for the CNV-related phenotype is that TRAPPC9 may be partially paternally imprinted in brain, and overlapping CNVs may cause loss of regulation. Identification of genes for autism and ID will translate into earlier diagnosis and better clinical care for this population in the future.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 162-189). Also available in print.

Neurodegenerative disorders are a group of age-related conditions resulting in neuronal cell death and protein accumulation. It is estimated that around 5-10% of these cases are genetically mediated. Most commonly this is by pathogenic single nuclear variants (SNVs), though combinations of rare variants (termed oligogenic variation), copy-number variation (CNVs), somatic mutations in nuclear DNA, and somatically acquired mitochondrial DNA variants have all been hypothesised to increase disease risk or cause disease. Firstly, using a combination of exome sequencing and array genotyping on 1511 post-mortem brain samples within the MRC Brain Bank, we detected 61 monogenic cases of disease, 349 brains carrying disease risk factors, and identified that variants in GRN and PRPH may increase the risk of developing dementia with lewy bodies (DLB) and Alzheimer’s disease (AD) respectively. Secondly, we detected a previously unknown systematic bias in the interpretation of oligogenic interactions with implications for our understanding of disease mechanisms and coexistent clinical diagnostic utility. Thirdly, we detected a novel copy-number gain in LAMA5 associated with Creutzfeldt-Jakob disease (CJD), and fourthly, we determine that at least 1% of the population carry high level somatic protein-coding mutations affecting at least 10% of cells within the brain. Subsequently, additional focussed deep-sequencing studies revealed that several regions of the brain are likely to contain clones of low-level somatic mutations that are pathogenic when present in the germline, and that age-related clonal mutations that arise in blood are present at high levels within the aging brain and are associated with Lewy Body pathology. Finally, using transgenic mice that over express human α-synuclein and which either accrue or transmit mtDNA mutations, we determine that the presence of mtDNA mutations exacerbate some phenotypic traits of Lewy body disorders, and may reduce the volume of critical neuroanatomical brain regions whilst paradoxically reducing α-synuclein accumulation. Taken together, these data enable the first genetically stratified brain tissue resource in the UK, describe new disease genetic risk factors (both SNVs and CNVs) for neurodegenerative disorders, and also help define the somatic genetic architecture of the human brain. In addition, we describe the in vivo interaction between mutations in the mitochondrial genome and a progressive neurodegenerative disorder in mice.

Orientador: Iscia Teresinha Lopes Cendes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-17T11:06:08Z (GMT). No. of bitstreams: 1 Secolin_Rodrigo_D.pdf: 5866562 bytes, checksum: 5079bfd5d88341ce619480ba6e19fb16 (MD5) Previous issue date: 2011 / Resumo: Fatores genéticos têm sido descritos para diversas doenças do sistema nervoso central. Uma etapa importante na identificação de genes responsáveis por estas doenças são os estudos de mapeamento genético. Além disso, devido às novas tecnologias de aquisição de dados de genótipos dos indivíduos, é necessário o estudo e desenvolvimento de programas de processamento de grande quantidade de dados para as análises estatísticas. Os objetivos deste trabalho foram: 1) criar uma interface entre os equipamentos de aquisição de dados de genótipos e os programas estatísticos, por meio de programas de processamento de dados; 2) aplicar e avaliar os modelos estatísticos em amostras de famílias segregando três doenças neuro-psiquiátricas: epilepsia do lobo temporal mesial (ELTM), polimicrogiria perisylviana bilateral congênita (PPBC) e transtorno afetivo bipolar (TAB). A interface foi desenvolvida a partir de um algoritmo lógico, o qual adiciona a matriz dos dados dos genótipos provenientes dos equipamentos em uma matriz representativa dos dados das famílias. Este algoritmo, denominado JINGLEFIX, foi programado em linguagem de computador PERL e ambiente R e utilizado posteriormente nos estudos de mapeamento genético da ELTM, PPBC e TAB. Análise de segregação foi realizada em 148 famílias nucleares com ELTM, com um total de 698 indivíduos, visto que esta síndrome não possui padrão de herança conhecido. Uma família, segregando PPBC com um total de 15 indivíduos e um padrão conhecido de herança ligada ao X dominante, foi submetida à análise paramétrica de ligação por meio do pacote de programas LINKAGE, utilizando 18 marcadores microssátelites na região candidata Xq27-Xq28. Análise não paramétrica de ligação realizada em uma amostra de 74 famílias segregando TAB, totalizando 411 indivíduos, por meio do teste de transmissão de desequilíbrio de ligação (TDT), utilizando 21 single nucleotide polymosphisms (SNPs) para 21 regiões candidatas. A análise de segregação revelou a presença de um gene de maior efeito com um padrão autossômico dominante, além da presença de genes de menor efeito influenciando no fenótipo da ELTM. O posterior mapeamento genômico da ELTM, utilizando os parâmetros definidos na análise de segregação, revelou ligação genética na região 18p11. A análise paramétrica de ligação genética levou ao mapeamento da região Xq27 para a família com PPBC, diferente da região candidata previamente descrita. Esta diferença pode ser explicada pelo tipo de amostra familiar utilizada pelos dois estudos. Em relação ao TAB, a análise não paramétrica identificou a região candidata 3p22. Posterior estudo de refinamento da região 3p21-3p22 utilizando 94 SNPs adicionais e estudo de expressão gênica identificou o gene ITGA9 como possível gene de susceptibilidade para o TAB. Comparando o poder estatístico entre as análises, foi observado maior poder estatístico na análise paramétrica utilizando uma ou poucas famílias, com um número grande de indivíduos por família; enquanto que o poder estatístico foi maior nas análises não paramétricas utilizando múltiplas famílias de tamanhos moderados e estruturas variadas. Conclui-se que o algoritmo de processamento de dados e a adequada aplicação dos modelos estatísticos são fundamentais para sucesso do mapeamento genético das regiões e dos genes responsáveis pelas doenças neuro-psiquiátricas estudadas / Abstract: Genetic factors have been described for several central nervous system diseases. A main step for disease gene identification is genetic mapping study. In addition, due new genotype acquire technology, the development of genotype processing data software is required. The objectives of this work were: 1) to generate interface between genotype equipment and statistical software by processing data algorithm; 2) to apply and evaluate statistical models in family sample segregating three neurological diseases: mesial temporal lobe epilepsy (MTLE), bilateral perysilvian polymicrogyria (BPP) and bipolar affective disorder (BPAD). Data interface was developed from a logic algorithm, which adds a genotype matrix data from equipment to a family data matrix. This algorithm, called JINGLEFIX, was implemented in PERL computer language and R environment. In addition, this software was used in genetic mapping study for MTLE, BPP and BPAD. Segregation analysis was performed in 148 nuclear MTLE pedigrees, with a total of 698 individuals, since this syndrome has not known inheritance pattern. One BPP pedigree with known X-linked dominant pattern of inheritance, with a total of 15 individuals, was submitted to parametric linkage analysis by LINKAGE package, using 18 microsatellite markers on candidate region Xq27-Xq28. Non-parametric linkage analysis was performed from 74 BPAD families, with a total of 411 individuals, by transmission disequilibrium test (TDT) and using 21 single nucleotide polymorphisms (SNPs) for 21 candidate regions. Segregation analysis revealed a major effect gene with an autosomal dominant pattern of inheritance and minor gene effect, which could influence MTLE phenotype. Further whole genome analysis mapped the putative MTLE major gene on 18p11. Parametric linkage analysis mapped Xq27 locus for BPP, a different region compared to the Xq28 previous described. This difference could be explained to sample type used by the two studies. Non-parametric linkage for BPAD identified the candidate region on 3p22. Further studies using 94 additional SNPs on 3p21-3p22 and gene expression analysis identified ITGA9 as susceptibility gene for BPAD. A comparison of statistical power between statistical analyses showed a high statistical power for parametric linkage analysis from one or a few large families; whereas a high statistical power was observed for non-parametric linkage analysis using several moderate size families. The conclusion of this study is that data processing algorithm and adequate statistical model applying are fundamental tools for successful of genetic mapping of complex diseases / Doutorado / Neurociencias / Doutor em Ciências

No description available.

The mammalian brain is a complex organ, the result of a very specific and regulated differentiation process. Although there are many different cell types in the mammalian brain, neurons make up the bulk of the tissue. Neurons come from the divisions of radial glial progenitors (RGPs), which are columnar stem cells in the developing brain. These cells undergo two types of division: symmetric or asymmetric. Symmetric divisions expand the stem cell population, resulting in two new RGPs. Symmetric divisions are critical for ensuring the stem cell population is not depleted too quickly in development. Asymmetric divisions are neurogenic, producing one RGP and one cell that will either differentiate into one neuron, or an intermediate progenitor (IP) that will divide again and produce two to four neurons (Shitamukai, Konno, and Matsuzaki 2011). Several factors have been linked to this determination, including mitotic spindle orientation, centrosomal inheritance, and exposure to proliferative factors, like sonic hedgehog and Notch (Chenn and McConnell 1995; Gaiano and Fishell 2002; Han 2016). This work will focus on spindle orientation, which has been linked to cell fate in many contexts (Lancaster and Knoblich 2012; Williams and Fuchs 2013; Chenn and McConnell 1995). Spindle orientationmust be tightly controlled in order to expand the RGP cell population in early development, then, with more randomized spindles, to shift to producing neural precursors during cortical expansion (Götz and Huttner 2005). While the exact mechanism is still unknown, the orientation of the mitotic spindle relative to the ventricular surface at the time of division affects what type of division occurs (Lancaster and Knoblich 2012). A related process in RGP neural production is interkinetic nuclear migration (INM), in which the RGP nucleus travels apically and basally in a cell-cycle dependent manner (Noctor et al. 2001; Sauer 1935; Hu et al. 2013). The RGP only divides when the nucleus reaches the apical surface; why this occurs is still not known. INM ensures that only a small population of RGPs is dividing in a controlled manner, allowing for cells to interpret polarity cues and orientthe spindle while dividing. One protein that is important to multiple processes in neuronal development is Kif1A. Kif1A is a kinesin motor that has been shown to be critical for INM, in particular for transporting the nucleus basally after division. When Kif1A expression is reduced using shRNA, RGPs fail to migrate away from the ventricular surface, but continue to go through the cell cycle at a normal rate (Carabalona, Hu, and Vallee 2016). Additionally, RGPs that lack Kif1A also exhibit more horizontal and symmetric divisions. This indicates that Kif1a is involved in asymmetric, oblique divisions that produce neurons. Thus, without Kif1a, RGPs produce fewer neurons, instead expanding the RGP cell population. Another kinesin that may be involved in spindle orientation is Kif13B. Kif13B is in the same kinesin-3 subfamily as Kif1A. While structurally very similar to Kif1A, it does have distinct features. It contains a CAP-gly domain, used for binding to the plus end of microtubules. This domain is absent from other kinesin-3 family members, including the most closely related,Kif13A. Kif13B has been shown to be critical for spindle orientation in polarized Drosophila S2 cells, as well as in neuroblasts (Carabalona, Hu, and Vallee 2016; Siegrist and Doe 2005). Kif13B functions to anchor the mitotic spindle to other factors at the cell cortex during mitosis. This occurs through direct interaction with Discs large (Dlg1), which then connects to other factors at the cell membrane, including G?i, LGN, and NuMA. This is a critical process to ensure daughter cells are properly specified. Many of these factors, including LGN and NuMA have been identified as important spindle regulators in RGP divisions as well. Kif13B binds to Dlg1 and to 14-3-3 ?, which is bound to 14-3-3 ?, bound to NudE and Dynein, connecting the Kif13B to Dynein (Lu and Prehoda 2013). Kif13B, as a kinesin, moves along microtubules towards the plus end. Dynein moves in the opposite direction, towards the minus end. The connection of two opposing motors moving in opposite directions may serve to put tension on the spindle and prevent it from freely moving within the cell. When Kif13B is knocked down or removed in cells, the spindle orients randomly in the cell, not in line with LGN or NuMA at the cell cortex (Siegrist and Doe 2005; Lu and Prehoda 2013). This indicates that in mammalian systems, it likely is important for maintaining orientation, and its loss in RGPs would result in random orientation as well. This would result in more neurogenic divisions in RGPs, which is the opposite of the effect seen with Kif1a shRNA. By using in utero electroporation of embryonic rat brains as well as a mouse model ofKif13b knockout in RGPs, I have shown that Kif13B and Kif1A have opposing roles in neurogenesis. This difference can be traced to an alteration of IP production, which Kif1A shRNA decreases, and Kif13b shRNA increases. This can be further traced to the opposing effects on spindle orientation of dividing RGPs. Kif1a shRNA results in more horizontal spindle angles while Kif13b shRNA or deletion results in more random spindle angles. While the kinesin-3 family members are very similar in structure, there are key differences between them. Kif1A has a cargo binding domain at its C terminus, the pleckstrin homology (PH) domain. Kif13B contains a CAP-gly domain. This difference in tail domains would presumably allow Kif13B to bind to microtubule plus ends, while Kif1A would dissociate from the spindle. This difference, therefore, could explain why these two very similar kinesins appear to be performing the opposite roles in spindle orientation. This work provides evidence for a novel mechanism of regulation of neuron production in the mammalian cortex.

No description available.

In Drosophila, the functionally conserved transcription factor, doublesex (dsx), is pivotal to the specification of sexual identity in both males and females. One of its key dedicated roles involves regulating the development of a sexually dimorphic nervous system (NS) that underlies both male and female reproductive behaviours. Specific inhibition of the function of dsx-expressing neurons in males and females results in a global disruption of these sex-specific behavioural outputs. However, little is known about the functional organisation of this dsx circuit that encodes the potential to display these behaviours. Such investigations require the generation of a novel transgenic tool, capable of separating the function of dsx in the NS from that of the body. To achieve this, I generated a novel split-GAL4 dsx^GAL4-DBD hemidriver by ends in homologous recombination. Coupling the novel tool with the pan-neuronal elav^VP16-AD hemidriver, revealed spatial restriction of dsx^GAL4-DBD/elav^VP16-AD expression to dsx neurons only; enabling the realisation of novel patterns of dsx-expression in the peripheral NS. Next, the ability to elicit male-specific behavioural outputs upon activation of all dsx neurons formed the basis of a large behavioural screen aimed at parsing dsx circuitry into functionally distinct clusters. I utilised the novel dsx^GAL4-DBD hemidriver to screen a large collection of extant enhancer trap lines (ET^VP16-AD), for the elicitation of distinct sub-behaviours of male courtship. Here, I show that the activity of dsx-expressing clusters in: i) the brain (dsx-pC1, -pC2 and -pC3 collectively) regulate the early steps of male courtship (initiation, orientation and wing extension), ii) the pro- and mesothoracic ganglia (dsx-TN1 and -TN2) regulate the middle steps of male courtship (wing extension and possibly courtship song) and iii) the abdominal ganglia (dsx-Abg) regulate the late steps of male courtship (abdominal curling, attempted copulation and copulation). These data establish functional correlations between dsx clusters in distinct neuroanatomical foci and specific sub-behaviours of the courtship repertoire. Furthermore, the novel intersectional tool primed a collaborative study on female post-copulatory behaviours. We identified key sensory neurons in the female reproductive tract involved in initiating post-mating behaviours. Subsequent functional interrogations of dsx circuitry in the central NS revealed a subset of dsx-expressing neurons in the Abg that mediate changes in the female behavioural repertoire after mating. Characterisation of this relatively simple neural circuitry sheds light on the organisation of the fly brain. Ultimately, future studies will define principles of neural circuit operation, which may be similarly conserved in the nervous systems of higher animals.

published_or_final_version / abstract / Anatomy / Master / Master of Philosophy