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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TL;DR: There is at least a twofold increase in expression of the DHFR-TS gene, and this may explain the ability of the pyrimethamine-resistant lines to grow in increased amounts of the drug.
Abstract: We selected lines of Plasmodium chabaudi that are resistant to high levels of the antifolate drug pyrimethamine and have shown that rearrangement and duplication of a portion of chromosome 7 has occurred in the resistant lines. This chromosomal duplication results in an increase in the chromosome number from 14 to 15: two derived chromosomes (450 kilobases and 1.1 megabases) were smaller than the original chromosome 7 (1.3 megabases), so that essentially only a 200-kilobase region was duplicated. This region contained the DHFR-TS gene and the closely linked Hsp70 gene. We have macrorestriction mapped chromosome 7 from the pyrimethamine-susceptible line (DS) and also the duplicated chromosome 7s in the resistant line. From these maps, we have proposed a process for the karyotype changes. Sequencing of the DHFR gene from the parent and derived chromosomes showed that there were no mutations in the coding sequence. As a result of the duplication of the DHFR-TS gene, there is at least a twofold increase in expression of the DHFR-TS gene, and this may explain the ability of the pyrimethamine-resistant lines to grow in increased amounts of the drug.
67 citations
TL;DR: Altered abnormalities in the tangential and radial expansion of the cerebral cortex during fetal development in the trisomy 16 (Ts16) mouse, a model for humantrisomy 21 (Down syndrome), resulted in a reduction of final telencephalic size and a decrease of radial cortical units in the mature brain.
Abstract: We have studied abnormalities in the tangential and radial expansion of the cerebral cortex during fetal development in the trisomy 16 (Ts16) mouse, a model for human trisomy 21 (Down syndrome). Slowed tangential expansion of the neuroepithelium in Ts16 resulted in a reduction of final telencephalic size and is predicted to decrease the number of radial cortical units in the mature brain. In addition, radial growth of the Ts16 cortex was delayed at the time of peak cortical neurogenesis in normal mice, but by embryonic day 18 the cortex reached normal thickness. Because mouse chromosome 16 shares many genes with human chromosome 21, abnormalities in Ts16 brain development may parallel abnormalities in trisomy 21.
67 citations
TL;DR: It is suggested that effective development of gene–phenotype correlations in DS requires a serious and continuous effort to assimilate broad categories of information on chromosome 21 genes, plus the creation of more versatile mouse models.
Abstract: Recent genomic sequence annotation suggests that the long arm of human chromosome 21 encodes more than 400 genes. Because there is no evidence to exclude any significant segment of 21q from containing genes relevant to the Down syndrome (DS) cognitive phenotype, all genes in this entire set must be considered as candidates. Only a subset, however, is likely to make critical contributions. Determining which these are is both a major focus in biology and a critical step in efficient development of therapeutics. The subtle molecular abnormality in DS, the 50% increase in chromosome 21 gene expression, presents significant challenges for researchers in detection and quantitation. Another challenge is the current limitation in understanding gene functions and in interpreting biological characteristics. Here, we review information on chromosome 21-encoded proteins compiled from the literature and from genomics and proteomics databases. For each protein, we summarize their evolutionary conservation, the complexity of their known protein interactions and their level of expression in brain, and discuss the implications and limitations of these data. For a subset, we discuss neurologically relevant phenotypes of mouse models that include knockouts, mutations, or overexpression. Lastly, we highlight a small number of genes for which recent evidence suggests a function in biochemical/cellular pathways that are relevant to cognition. Until knowledge deficits are overcome, we suggest that effective development of gene–phenotype correlations in DS requires a serious and continuous effort to assimilate broad categories of information on chromosome 21 genes, plus the creation of more versatile mouse models. © 2006 Wiley-Liss, Inc.
67 citations
TL;DR: A comprehensive physical map of overlapping YACs, a dense linkage map and an almost complete long-range restriction map have been produced much earlier than expected, helping to characterize both genes and their impact in health and disease.
66 citations
TL;DR: In this article, the EBI/GeneBank database using nonhuman hair keratin associated protein (KAP) gene sequences as a query resulted in the identification of two human KAP gene domains on chromosome 21, one of which, located at 21q22.1, has recently been characterized.
66 citations