Diabetes and heat shock protein.
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Animals↗
Biomedical subjects
J Fantes
Publications and source records attributed to J Fantes.
Isolation of anonymous DNA markers for human chromosome 22q11 from a flow-sorted library, and mapping using hybrids from patients with DiGeorge syndrome.
DiGeorge syndrome (DGS) is a human developmental defect of the structures derived from the third and fourth pharyngeal pouches. It apparently arises due to deletion of 22q11. We describe a strategy for the isolation of DNA probes for this region. A deleted chromosome 22, which includes 22q11, was flow-sorted from a lymphoblastoid cell line of a patient with cat eye syndrome and used as the source of DNA. A DNA library was constructed from this chromosome by cloning into the EcoR1 site of the vector Lambda gt10. Inserts were amplified by PCR and mapped using a somatic cell hybrid panel of this region. Out of 32 probes, 14 were mapped to 22q11. These probes were further sublocalised within the region by dosage analysis of DGS patients, and by the use of two new hybrid cell lines which we have produced from DGS patients. One of these lines (7939B662) contains the altered human chromosome segregated from its normal homologue. This chromosome 22 contains an interstitial deletion in 22q11, and will be useful for localising further probes to the DGS region.
Base Sequence↗
Lambda CM8, a human sequence with putative centromeric function, does not map to the centromere but is present in one to two copies at 9qter.
A DNA fragment isolated from a human genomic library, was reported to be present at all human centromeres and present at 16-32 copies per genome. Reintroduction of this DNA into mammalian cells as a concatenated phage clone gave rise to dicentric chromosomes which gave rise to a new, stable, chromosome. Taken together these observations could mean that this DNA is part of a native centromere. We have reexamined the location and copy number of this sequence and find it to be present at 1-2 copies per genome with a single site of in situ hybridisation at 9qter.
Blotting, Southern↗
Functional reintroduction of human telomeres into mammalian cells.
Telomeric sequences of eukaryotes consist of short tandem repeats organized in arrays of variable length in which the guanine-rich strand runs 5'----3' toward the chromosomal end. The terminal repeats in yeast are the only elements necessary for telomere function in this organism. To test whether mammalian terminal repeats can function after reintroduction into a mammalian cell, a repeat-containing terminal fragment from a human chromosome was electroporated into a hamster-human hybrid cell line. In 6 of 27 independent transformants analyzed, the introduced sequences were found at the ends of chromosomes, based on all available criteria. Terminal restriction-fragment heterogeneity and the survival of these chromosomes demonstrate that these telomeres are functional. Cytogenetic evidence from one of these cell lines suggests that chromosome breakage with healing at the integration site is the mechanism responsible for the terminal location.
Animals↗
Oligonucleotide-primed in situ DNA synthesis (PRINS): a method for chromosome mapping, banding, and investigation of sequence organization.
Oligonucleotides were annealed to complementary sequences in fixed human metaphase chromosomes and extended with DNA polymerase. The newly synthesized fragments were labeled by incorporating bio-11-dUTP instead of TTP, and the sites of synthesis were detected by immunocytochemistry, using fluorochromes as the reporter molecules. We have obtained clear localization with oligonucleotides from alphoid (centromeric sequences), simple sequence (satellite) DNAs, a variety of Alu-dispersed repeated sequences, and oligonucleotides derived from the Tetrahymena and Trypanosoma telomere-specific sequences. The simple sequence and alphoid oligonucleotides gave results at least comparable to those obtained using the whole molecule as a probe for in situ hybridization, whereas the Alu oligonucleotides produced a diversity of results which depended on the absolute length and location of the oligonucleotide within the Alu sequence. The telomere-specific oligomers also produced a variety of results. The G-rich Trypanosoma oligomer and its complementary C-rich sequence produced strong telomeric signals and some interstitial signals on mouse chromosomes, but only weak telomeric signals on human chromosomes. The G-rich Tetrahymena oligomer produced detectable telomeric signals on human chromosomes. The technique appears to be a valuable extension of present tools for mapping and examining the organization of DNA sequences within chromosomes.
Animals↗
The structure of a subterminal repeated sequence present on many human chromosomes.
All telomeres which have been studied consist of an array of simple G/C rich repeats. Human telomeres were shown to share sequence similarity with those of lower eukaryotes by cross-hybridization and human telomeric sequences have been cloned by complementation of telomere function in yeast. Analysis of human telomeric sequences cloned in this way is described here. The terminal part of the cloned human telomeric DNA consists of an array of simple repeats, principally of the sequence TTAGGG and derivatives. The very terminal part consists of yeast-type telomeric repeats which suggests that the human telomeric sequences have acted as a primer for the addition of additional telomeric repeats in the yeast. Subterminal sequences are shared between a number of clones and in situ data shows that these subterminal sequences are present at several different chromosomal ends. Related sequences are present at internal as well as telomeric positions. Differences in the hybridization patterns of subterminal sequences in somatic compared to germ-line tissues are described which indicate differential modification of these sequences during development.
Base Composition↗
Automatic detection of fragile X chromosomes using an X centromere probe.
In order to score for the fragile X syndrome, blood samples are prepared with absorption stain labeling by in situ hybridisation of the X chromosome centromeres. Metaphases are located, digitised at high resolution, and segmented fully automatically. A three stage adaptive classification scheme for labeled X chromosomes is then applied. This consists of a simple box classifier to identify plausible X and false positive X chromosomes, followed by a quadratic discriminant classifier that is re-trained for each sample. The modal number of X chromosomes is then determined for each sample and used to refine the classification. A simple fragile site detector is applied to the distal portion of the detected X chromosome long arms. From the results we estimate computer and operator time requirements for a screening system in which the operator reviews only the apparently fragile X chromosomes detected by the computer.
Biotin↗
Use of an alphoid satellite sequence to locate the X chromosome automatically, with particular reference to identification of the fragile X.
An alphoid DNA sequence primarily located on the X chromosome was labeled with biotin and hybridized in situ to preparations of metaphase chromosomes derived from fragile X-affected individuals; hybridization sites were detected immunologically. Labeled X chromosomes were located automatically in digitized images of metaphase cells by searching for the concurrence of a pronounced peak in the longitudinal density profile with the centromere in medium-sized chromosomes having a suitable centromeric index. Approximately 70% of the X chromosomes were detected by a simple classifier; this rate is similar to the automatic classification rate obtained with G-banded metaphases. The frequency of detection of the fragile X site obtained when scored directly from the microscope using this new preparation technique did not differ significantly from the frequency obtained in the same sample by means of a conventional technique. The frequency obtained by visual scoring of digitized images was slightly higher, but not significantly so.
Chromosome Mapping↗
Karyotype and chromosomal banding pattern in Heteropeza pygmaea.
The chromosomes of somatic and germ line cells of female embryos produced by paedogenesis were studied. The haploid set in somatic cells consists of one long submetacentric chromosome, one large acrocentric, one medium metacentric and two small acrocentrics. The length vs arm index karyogram makes it possible to distinguish all but the two pairs of small acrocentric chromosomes. --Atempts were made to develope a method for banding pattern visualization. The best result was obtained using trypsin which induced banding in the chromosomes of the somatic cells and occasionally also the germ line cells. The resulting banding patterns were frequently not identical in members of a chromosome pair. There was also a variation between metaphases within an embryo as well as from different embryos. Some tentative explanations for these results are discussed.
Animals↗