Topic
Chromosome 21
About: Chromosome 21 is a research topic. Over the lifetime, 4736 publications have been published within this topic receiving 206655 citations. The topic is also known as: chr21 & Homo sapiens chromosome 21.
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Ohio State University1, St. Jude Children's Research Hospital2, University of Nebraska Medical Center3, Children's Hospital of Philadelphia4, Children's Mercy Hospital5, Children's Hospital Los Angeles6, University of Minnesota7, Oregon Health & Science University8, Anschutz Medical Campus9, University of Iowa10, Wake Forest University11, University of Mississippi Medical Center12, University of North Carolina at Chapel Hill13, University of Michigan14, University of Texas Southwestern Medical Center15, University of Florida16, University of Nebraska Omaha17, All Children's Hospital18, Medical College of Wisconsin19, American College of Medical Genetics20, University of Alabama at Birmingham21
TL;DR: The results suggest that the abnormal mitosis involves specific chromosomes dependent on the number of chromosomes aberrantly distributed, raising provocative questions regarding the mitotic mechanism.
Abstract: Children with acute lymphoblastic leukemia (ALL) and high hyperdiploidy (>50 chromosomes) are considered to have a relatively good prognosis. The specific extra chromosomes are not random; extra copies of some chromosomes occur more frequently than those of others. We examined the extra chromosomes present in high hyperdiploid ALL to determine if there were a relation of the specific extra chromosomes and modal number (MN) and if the extra chromosomes present could differentiate high hyperdiploid from near-triploid and near-tetraploid cases. Karyotypes of 2,339 children with ALL and high hyperdiploidy at diagnosis showed a distinct nonrandom sequential pattern of gain for each chromosome as MN increased, with four groups of gain: chromosomes 21, X, 14, 6, 18, 4, 17, and 10 at MN 51-54; chromosomes 8, 5, 11, and 12 at MN 57-60; chromosomes 2, 3, 9,16, and 22 at MN 63-67; chromosomes 1, 7 13, 15, 19, and 20 at MN 68-79, and Y only at MN >or=80. Chromosomes gained at lower MN were retained as the MN increased. High hyperdiploid pediatric ALL results from a single abnormal mitotic division. Our results suggest that the abnormal mitosis involves specific chromosomes dependent on the number of chromosomes aberrantly distributed, raising provocative questions regarding the mitotic mechanism. The patterns of frequencies of tetrasomy of specific chromosomes differs from that of trisomies with the exception of chromosome 21, which is tetrasomic in a high frequency of cases at all MN. These results are consistent with different origins of high hyperdiploidy, near-trisomy, and near-tetrasomy.
81 citations
TL;DR: In this article, the authors investigated if autoimmunity in DS is promoted by the reduction of pGE owing to dysregulation of AIRE, and they assessed the expression of the AIRE and of several peripheral tissue-restricted Ag genes by quantitative PCR in thymus samples from 19 DS subjects and 21 euploid controls.
Abstract: Down syndrome (DS), or trisomy of chromosome 21, is the most common genetic disorder associated with autoimmune diseases. Autoimmune regulator protein (AIRE), a transcription factor located on chromosome 21, plays a crucial role in autoimmunity by regulating promiscuous gene expression (pGE). To investigate if autoimmunity in DS is promoted by the reduction of pGE owing to dysregulation of AIRE, we assessed the expression of AIRE and of several peripheral tissue-restricted Ag genes by quantitative PCR in thymus samples from 19 DS subjects and 21 euploid controls. Strikingly, despite the 21 trisomy, AIRE expression was significantly reduced by 2-fold in DS thymuses compared with controls, which was also confirmed by fluorescent microscopy. Allele-specific quantification of intrathymic AIRE showed that despite its lower expression, the three copies are expressed. More importantly, decreased expression of AIRE was accompanied by a reduction of pGE because expression of tissue-restricted Ags, CHRNA1, GAD1, PLP1, KLK3, SAG, TG, and TSHR, was reduced. Of interest, thyroid dysfunction (10 cases of hypothyroidism and 1 of Graves disease) developed in 11 of 19 (57.9%) of the DS individuals and in none of the 21 controls. The thymuses of these DS individuals contained significantly lower levels of AIRE and thyroglobulin, to which tolerance is typically lost in autoimmune thyroiditis leading to hypothyroidism. Our findings provide strong evidence for the fundamental role of AIRE and pGE, namely, central tolerance, in the predisposition to autoimmunity of DS individuals.
80 citations
TL;DR: The study of over 700 species, from algae to humans, reveals that specific DNA sequences, have an optimal territory within the centromere-telomere field, and predictions can be made concerning gene organization, gene function and chromosome evolution.
Abstract: The study of over 700 species, from algae to humans, reveals that specific DNA sequences, have an optimal territory within the centromere-telomere field. These DNA sequences have maintained their territory within the chromosome field for millions of years irrespective of variation in arm length, of change in chromosome type and of species evolution. Some of these DNA sequences have been isolated biochemically or analysed at the molecular level. They include, e.g., the proximal heterochromatic segments, the genes for ribosomal RNA, and the telomeric heterochromatin. Order prevails in the eukaryotic chromosome.
This order allows classification of genes, rearrangements and chromosomes on a genetic basis. Genes are classified as centrons, medons and telons. Rearrangements are classified as: conservative, discordant, disruptive, destructive and incompatible. Chromosomes are also classified depending on their length, arm size and number. These chromosome properties and features now acquire an organizatory meaning which they lacked previously.
The available molecular information supports the evidence from the field. The study of the split gene reveals that it is the relative position of the DNA sequences which determines their function.
On the basis of the chromosome field, predictions can be made concerning gene organization, gene function and chromosome evolution.
80 citations
TL;DR: The identification and preliminary characterization of mice carrying a chromosomal rearrangement of the Ts65Dn genome whereby the marker chromosome has been translocated to Chromosome 12 (MMU12) forming a Robertsonian chromosome are described and it is concluded that this new model of Down syndrome offers reproductive advantages without sacrificing the integrity of theTs 65Dn model.
Abstract: The segmental trisomy model, Ts65Dn, has been a valuable resource for the study of the molecular and developmental processes associated with the pathogenesis of Down syndrome. However, male infertility and poor transmission of the small marker chromosome, T(1716)65Dn, carrying the distal end of mouse Chromosome 16 (MMU16) are limiting factors in the efficient production of these animals for experimental purposes. We describe here the identification and preliminary characterization of mice, designated Ts[Rb(12.1716)]2Cje, carrying a chromosomal rearrangement of the Ts65Dn genome whereby the marker chromosome has been translocated to Chromosome 12 (MMU12) forming a Robertsonian chromosome. This stable rearrangement confers fertility in males and increases the frequency of transmitted segmental trisomy through the female germline. We confirm retention of a dosage imbalance of human Chromosome 21 (HSA21)-homologous genes from App to the telomere and expression levels similar to Ts65Dn within the triplicated region. In addition, we characterized the dendritic morphology of granule cells in the fascia dentata in Ts[Rb(12.1716)]2Cje and 2N control mice. Quantitative confocal microscopy revealed decreased spine density on the dendrites of dentate granule cells and significantly enlarged dendritic spines affecting the entire population in Ts[Rb(12.1716)]2Cje as compared to 2N controls. These findings document that the structural dendritic spine abnormalities are similar to those previously observed in Ts65Dn mice. We conclude that this new model of Down syndrome offers reproductive advantages without sacrificing the integrity of the Ts65Dn model.
80 citations
TL;DR: This work investigated the chromosomal location of papaya’s small male specific region of the hermaphrodite Y (Yh) chromosome (MSY) and its genomic features, which resulted in the largest collection of contiguous genomic DNA sequences of a Y chromosome in flowering plants.
Abstract: Sex chromosomes in Xowering plants evolved recently and many of them remain homomorphic, including those in papaya. We investigated the chromosomal location of papaya's small male speciWc region of the hermaphrodite Y (Y h ) chromosome (MSY) and its genomic features. We conducted chromosome Xuorescence in situ hybridization mapping of Y h -speciWc bacterial artiWcial chromosomes (BACs) and placed the MSY near the centromere of the papaya Y chromosome. Then we sequenced Wve MSY BACs to examine the genomic features of this specialized region, which resulted in the largest collection of contigu- ous genomic DNA sequences of a Y chromosome in Xow- ering plants. Extreme gene paucity was observed in the papaya MSY with no functional gene identiWed in 715 kb MSY sequences. A high density of retroelements and local sequence duplications were detected in the MSY that is suppressed for recombination. Location of the papaya MSY near the centromere might have provided recombination suppression and fostered paucity of genes in the male spe- ciWc region of the Y chromosome. Our Wndings provide critical information for deciphering the sex chromosomes in papaya and reference information for comparative stud- ies of other sex chromosomes in animals and plants.
80 citations