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"CHROMOSOME"
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Down syndrome
Explains this genetic abnormality, its characteristics and how scientists are studying and treating it.
Book
Walking along chromosomes with super-resolution imaging, contact maps, and integrative modeling
Chromosome organization is crucial for genome function. Here, we present a method for visualizing chromosomal DNA at super-resolution and then integrating Hi-C data to produce three-dimensional models of chromosome organization. Using the super-resolution microscopy methods of OligoSTORM and OligoDNA-PAINT, we trace 8 megabases of human chromosome 19, visualizing structures ranging in size from a few kilobases to over a megabase. Focusing on chromosomal regions that contribute to compartments, we discover distinct structures that, in spite of considerable variability, can predict whether such regions correspond to active (A-type) or inactive (B-type) compartments. Imaging through the depths of entire nuclei, we capture pairs of homologous regions in diploid cells, obtaining evidence that maternal and paternal homologous regions can be differentially organized. Finally, using restraint-based modeling to integrate imaging and Hi-C data, we implement a method-integrative modeling of genomic regions (IMGR)-to increase the genomic resolution of our traces to 10 kb.
Journal Article
Sex differences in psychiatric disorders: what we can learn from sex chromosome aneuploidies
The study of sexual dimorphism in psychiatric and neurodevelopmental disorders is challenging due to the complex interplay of diverse biological, psychological, and social factors. Males are more susceptible to neurodevelopmental disorders including intellectual disability, autism spectrum disorder, and attention-deficit activity disorder. Conversely, after puberty, females are more prone to major depressive disorder and anxiety disorders compared to males. One major biological factor contributing to sex differences is the sex chromosomes. First, the X and Y chromosomes have unique and specific genetic effects as well as downstream gonadal effects. Second, males have one X chromosome and one Y chromosome, while females have two X chromosomes. Thus, sex chromosome constitution also differs between the sexes. Due to this complexity, determining genetic and downstream biological influences on sexual dimorphism in humans is challenging. Sex chromosome aneuploidies, such as Turner syndrome (X0) and Klinefelter syndrome (XXY), are common genetic conditions in humans. The study of individuals with sex chromosome aneuploidies provides a promising framework for studying sexual dimorphism in neurodevelopmental and psychiatric disorders. Here we will review and contrast four syndromes caused by variation in the number of sex chromosomes: Turner syndrome, Klinefelter syndrome, XYY syndrome, and XXX syndrome. Overall we describe an increased rate of attention-deficit hyperactivity disorder and autism spectrum disorder, along with the increased rates of major depressive disorder and anxiety disorders in one or more of these conditions. In addition to contributing unique insights about sexual dimorphism in neuropsychiatric disorders, awareness of the increased risk of neurodevelopmental and psychiatric disorders in sex chromosome aneuploidies can inform appropriate management of these common genetic disorders.
Journal Article
Female predisposition to TLR7-driven autoimmunity: gene dosage and the escape from X chromosome inactivation
Women develop stronger immune responses than men, with positive effects on the resistance to viral or bacterial infections but magnifying also the susceptibility to autoimmune diseases like systemic lupus erythematosus (SLE). In SLE, the dosage of the endosomal Toll-like receptor 7 (TLR7) is crucial. Murine models have shown that TLR7 overexpression suffices to induce spontaneous lupus-like disease. Conversely, suppressing TLR7 in lupus-prone mice abolishes SLE development. TLR7 is encoded by a gene on the X chromosome gene, denoted TLR7 in humans and Tlr7 in the mouse, and expressed in plasmacytoid dendritic cells (pDC), monocytes/macrophages, and B cells. The receptor recognizes single-stranded RNA, and its engagement promotes B cell maturation and the production of pro-inflammatory cytokines and antibodies. In female mammals, each cell randomly inactivates one of its two X chromosomes to equalize gene dosage with XY males. However, 15 to 23% of X-linked human genes escape X chromosome inactivation so that both alleles can be expressed simultaneously. It has been hypothesized that biallelic expression of X-linked genes could occur in female immune cells, hence fostering harmful autoreactive and inflammatory responses. We review here the current knowledge of the role of TLR7 in SLE, and recent evidence demonstrating that TLR7 escapes from X chromosome inactivation in pDCs, monocytes, and B lymphocytes from women and Klinefelter syndrome men. Female B cells where TLR7 is thus biallelically expressed display higher TLR7-driven functional responses, connecting the presence of two X chromosomes with the enhanced immunity of women and their increased susceptibility to TLR7-dependent autoimmune syndromes.
Journal Article
The carriers : what the fragile X gene reveals about family, heredity, and scientific discovery
\"Fragile X syndrome is a genetic condition that causes a range of neurodevelopmental problems including learning disabilities and cognitive impairment. Boys with the condition are more likely to be born fully affected by it, while women who are seemingly unaffected carriers have an increased risk of giving birth to an affected child. Recent research indicates that Fragile X syndrome is highly unusual in the world of genetic disorders, in that carriers, who were previously thought to show no symptoms at all, are in fact affected in their own ways: into adulthood, they can develop personality and emotional changes, tremors, and difficulty walking. The title characters in The Carriers, then, are the previous generations--mothers and grandparents--of fully affected Fragile X patients. This book aims to tell the stories of how families are affected by this genetic disorder over generations, as well as the initial science that discovered it and the current science that's teaching us how Fragile X is affecting silent carriers in ways that weren't previously recognized. Understanding psychiatric symptoms in premutation carriers is complicated by the fact that many are caring for children with Fragile X syndrome and fathers with the tremor/ataxia symptom (difficulty walking). This story particularly highlights women, who are often the carriers in question and also the genetic researchers achieving scientific breakthroughs\"-- Provided by publisher.
Book
Genetic data and the law : a critical perspective on privacy protection
\"Research using genetic data raises various concerns relating to privacy protection. Many of these concerns can also apply to research that uses other personal data, but not with the same implications for failure. The norms of exclusivity associated with a private life go beyond the current legal concept of personal data to include genetic data that relates to multiple identifiable individuals simultaneously and anonymous data that could be associated with any number of individuals in different, but reasonably foreseeable, contexts. It is the possibilities and implications of association that are significant, and these possibilities can only be assessed if one considers the interpretive potential of data. They are missed if one fixates upon its interpretive pedigree or misunderstands the meaning and significance of identification. This book demonstrates how the public interest in research using genetic data might be reconciled with the public interest in proper privacy protection\"-- Provided by publisher.
Book
Chromosomes in the flow to simplify genome analysis
Nuclear genomes of human, animals, and plants are organized into subunits called chromosomes. When isolated into aqueous suspension, mitotic chromosomes can be classified using flow cytometry according to light scatter and fluorescence parameters. Chromosomes of interest can be purified by flow sorting if they can be resolved from other chromosomes in a karyotype. The analysis and sorting are carried out at rates of 102–104 chromosomes per second, and for complex genomes such as wheat the flow sorting technology has been ground-breaking in reducing genome complexity for genome sequencing. The high sample rate provides an attractive approach for karyotype analysis (flow karyotyping) and the purification of chromosomes in large numbers. In characterizing the chromosome complement of an organism, the high number that can be studied using flow cytometry allows for a statistically accurate analysis. Chromosome sorting plays a particularly important role in the analysis of nuclear genome structure and the analysis of particular and aberrant chromosomes. Other attractive but not well-explored features include the analysis of chromosomal proteins, chromosome ultrastructure, and high-resolution mapping using FISH. Recent results demonstrate that chromosome flow sorting can be coupled seamlessly with DNA array and next-generation sequencing technologies for high-throughput analyses. The main advantages are targeting the analysis to a genome region of interest and a significant reduction in sample complexity. As flow sorters can also sort single copies of chromosomes, shotgun sequencing DNA amplified from them enables the production of haplotype-resolved genome sequences. This review explains the principles of flow cytometric chromosome analysis and sorting (flow cytogenetics), discusses the major uses of this technology in genome analysis, and outlines future directions.
Journal Article