85 research outputs found

    An outline of polar spaces: basics and advances

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    This paper is an extended version of a series of lectures on polar spaces given during the workshop and conference 'Groups and Geometries', held at the Indian Statistical Institute in Bangalore in December 2012. The aim of this paper is to give an overview of the theory of polar spaces focusing on some research topics related to polar spaces. We survey the fundamental results about polar spaces starting from classical polar spaces. Then we introduce and report on the state of the art on the following research topics: polar spaces of infinite rank, embedding polar spaces in groups and projective embeddings of dual polar spaces

    The co-occurrence of autistic and ADHD dimensions in adults: an etiological study in 17 770 twins

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    Autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD) often occur together. To obtain more insight in potential causes for the co-occurrence, this study examined the genetic and environmental etiology of the association between specific ASD and ADHD disorder dimensions. Self-reported data on ASD dimensions social and communication difficulties (ASDsc), and repetitive and restricted behavior and interests (ASDr), and ADHD dimensions inattention (IA), and hyperactivity/impulsivity (HI) were assessed in a community sample of 17 770 adult Swedish twins. Phenotypic, genetic and environmental associations between disorder dimensions were examined in a multivariate model, accounting for sex differences. ASDr showed the strongest associations with IA and HI in both sexes (rp 0.33 to 0.40). ASDsc also correlated moderately with IA (females rp 0.29 and males rp 0.35) but only modestly with HI (females rp 0.17 and males rp 0.20). Genetic correlations ranged from 0.22 to 0.64 and were strongest between ASDr and IA and HI. Sex differences were virtually absent. The ASDr dimension (reflecting restricted, repetitive and stereotyped patterns of behavior, interests and activities) showed the strongest association with dimensions of ADHD, on a phenotypic, genetic and environmental level. This study opens new avenues for molecular genetic research. As our findings demonstrated that genetic overlap between disorders is dimension-specific, future gene-finding studies on psychiatric comorbidity should focus on carefully selected genetically related dimensions of disorders

    Genomic plasticity of the MHC class I A region in rhesus macaques: extensive haplotype diversity at the population level as revealed by microsatellites

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    The Mamu-A genes of the rhesus macaque show different degrees of polymorphism, transcription level variation, and differential haplotype distribution. Per haplotype, usually one “major” transcribed gene is present, A1 (A7), in various combinations with “minor” genes, A2 to A6. In silico analysis of the physical map of a heterozygous animal revealed the presence of similar Mamu-A regions consisting of four duplication units, but with dissimilar positions of the A1 genes on both haplotypes, and in combination with different minor genes. Two microsatellites, D6S2854 and D6S2859, have been selected as potential tools to characterize this complex region. Subsequent analysis of a large breeding colony resulted in the description of highly discriminative patterns, displaying copy number variation in concert with microsatellite repeat length differences. Sequencing and segregation analyses revealed that these patterns are unique for each Mamu-A haplotype. In animals of Indian, Burmese, and Chinese origin, 19, 15, or 9 haplotypes, respectively, could be defined, illustrating the occurrence of differential block duplications and subsequent rearrangements by recombination. The haplotypes can be assigned to 12 unique combinations of genes (region configurations). Although most configurations harbor two transcribed A genes, one or three genes per haplotype are also present. Additionally, haplotypes lacking an A1 gene or with an A1 duplication appear to exist. The presence of different transcribed A genes/alleles in monkeys from various origins may have an impact on differential disease susceptibilities. The high-throughput microsatellite technique will be a valuable tool in animal selection for diverse biomedical research projects

    Bioenergetic status modulates motor neuron vulnerability and pathogenesis in a zebrafish model of spinal muscular atrophy

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    Degeneration and loss of lower motor neurons is the major pathological hallmark of spinal muscular atrophy (SMA), resulting from low levels of ubiquitously-expressed survival motor neuron (SMN) protein. One remarkable, yet unresolved, feature of SMA is that not all motor neurons are equally affected, with some populations displaying a robust resistance to the disease. Here, we demonstrate that selective vulnerability of distinct motor neuron pools arises from fundamental modifications to their basal molecular profiles. Comparative gene expression profiling of motor neurons innervating the extensor digitorum longus (disease-resistant), gastrocnemius (intermediate vulnerability), and tibialis anterior (vulnerable) muscles in mice revealed that disease susceptibility correlates strongly with a modified bioenergetic profile. Targeting of identified bioenergetic pathways by enhancing mitochondrial biogenesis rescued motor axon defects in SMA zebrafish. Moreover, targeting of a single bioenergetic protein, phosphoglycerate kinase 1 (Pgk1), was found to modulate motor neuron vulnerability in vivo. Knockdown of pgk1 alone was sufficient to partially mimic the SMA phenotype in wild-type zebrafish. Conversely, Pgk1 overexpression, or treatment with terazosin (an FDA-approved small molecule that binds and activates Pgk1), rescued motor axon phenotypes in SMA zebrafish. We conclude that global bioenergetics pathways can be therapeutically manipulated to ameliorate SMA motor neuron phenotypes in vivo
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