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Molecular cytogenetic evidence for amplification of chromosome-specific alphoid sequences at enlarged C-bands on chromosome 6.

We have characterized variant centromeric regions of chromosome 6 segregating in two families. The heteromorphism, 6ph+, stains negatively with G- and Q-banding and darkly with C-banding. The variant C-band regions measure two to three times the length of their homologues. The centromeric regions of the variant chromosome 6 and its homologue are not significantly elongated by adding 5-azacytidine to culture. We determined that the amount of the alphoid centromeric repeat 308 (DZ61), which is chromosome 6 specific, is amplified two- to threefold in the genomes of individuals with the 6ph+ variants. In situ hybridization localized the increase in 308 repeats to the 6ph+ region. These results suggest an association between amplification of chromosome-specific alphoid sequences and enlargement of specific C-band regions.

Centromere↗

[Unusual chromosomal rearrangement. An autosomal telomeric translocation on a multicentury satellited Y (Yqs) chromosome].

A new born male infant with craniostenosis and minor phenotypic malformations was found to have a satellited Yq chromosome with, translocated on its satellite, a segment from the terminal part of the long arm of a presumed autosome 14. The rearrangement is de novo since the propositus' father has a non-rearranged satellited Y chromosome and he is, furthermore, a member of a family line in which a Yqs is transmitted in patrilineary fashion since 1668. Such and autosomal translocation on a satellited Y chromosome is a very rare event, because the abnormality makes up a double rearrangement on the same arm of a chromosome, with a three-century interval between the two phenomenons. A presumed partial trisomy 14q is associated with the clinical picture of the case.

Craniosynostoses↗

Joining of recombination signals on the der 14q- chromosome in T-cell acute leukemia with t(10;14) chromosome translocation.

Sequence analysis of the translocation breakpoint junctions on the der(14q-) chromosome in six patients carrying a t(10;14) chromosome translocation revealed that the breakpoint occurred 5' to the HOX11 protooncogene at the breakpoint cluster region. HOX11 coding sequence was not effected. The translocation resulted in the joining of the V-(D)-J recombination signals 5' to the T-cell receptor D delta 2 segment on chromosome 14 with chromosome 10 at a location within a heptamer-like sequence. At the breakpoint junctions, the insertion of extra nucleotides, N-nucleotides, including P-nucleotides, was evident. The mechanism involved in this process is discussed.

Base Sequence↗

A computer-based videodensitometric system for studying banded human chromosomes illustrated by the analysis of the normal morphology of chromosome 18.

A computer-based, high-resolution, high-speed system is described for the digitization of television images of human G-banded chromosomes, on-line directly from a microscope. The digitized data are processed by a computer to determine the total length and centromere index of individual chromosomes and to obtain an integrated density profile representing the band pattern. The density profile is reduced by the computer to a series of dark and light bands, each with a defined position, width, and density. The results are displayed by the computer on a television monitor in a form that simulates routine laboratory preparations and that allows cytogenetic inspection. The system is easy to operate, and it includes a wide range of options for operator interaction to ensure reliability. The results of the computer analysis of the no. 18 chromosomes from five cells from each of 10 different persons demonstrated the usefulness of the system for detecting, measuring, and analyzing individual bands in human populations and its application to establishing band patterns of chromosomes in different states of contraction.

Azure Stains↗

[The physical mapping of human chromosomes. The use of the polymerase chain reaction on unique DNA sequences with a known location on chromosome 3].

16 pairs of oligonucleotide primers, complementary to unique DNA sequences of human chromosome 3, were synthesized. For 10 of these, fragments of expected length were generated in polymerase chain reaction (PCR). These fragments may be used as markers for detailed physical mapping of this chromosome. The above primers were used in PCR in order to analyse a hybrid mice-human cell line which contained presumably a fragment of human chromosome 3. The presence of human DNA in the hybrid line has been shown, but no ultimate evidence was received to confirm its location in human chromosome 3. By means of primers, complementary to the butyrylcholinesterase gene (BCHE), pools of clones from the yeast total library of human DNA were analysed, and then the pool and later the individual [correction of undividual] clone, containing a fragment of BCHE gene, were identified.

Base Sequence↗

Overrepresentation of small supernumerary marker chromosomes (sSMC) from chromosome 6 origin in cases with multiple sSMC.

Small supernumerary marker chromosomes (sSMC) in human are defined as additional centric derivatives smaller than chromosome 20. In the majority of the cases only one sSMC is present, leading to a more or less stable karyotype of 47,XX,+mar or 47,XY,+mar. In approximately 1.4% of sSMC cases two or up to seven markers of different chromosomal origin are reported. According to the literature a sSMC(6) was present in 33% of the patients with multiple sSMC while sSMC(6) are observed in <1% of cases with a single sSMC. Currently there is no explanation for this striking observation. Here we report on one more unique case with two sSMC, one derived from #5 and the other from #6. Using microdissection/reverse painting, subcentromere-specific multicolor FISH (subcenM-FISH) and multicolor banding (MCB), they could be described as min or r(6)(::p11.1 --> q11.1::) and r(5)(::p11.1 approximately 12 --> q10::q10 --> p11.1 approximately 12::), respectively. Reversed array CGH using the DNA of the microdissected sSMC as probe confirmed the FISH results and enabled the rapid mapping of the breakpoints.

Base Sequence↗

Breakpoint analysis of the pericentric inversion distinguishing human chromosome 4 from the homologous chromosome in the chimpanzee (Pan troglodytes).

The study of breakpoints that occurred during primate evolution promises to yield valuable insights into the mechanisms underlying chromosome rearrangements in both evolution and pathology. Karyotypic differences between humans and chimpanzees include nine pericentric inversions, which may have potentiated the parapatric speciation of hominids and chimpanzees 5-6 million years ago. Detailed analysis of the respective chromosomal breakpoints is a prerequisite for any assessment of the genetic consequences of these inversions. The breakpoints of the inversion that distinguishes human chromosome 4 (HSA4) from its chimpanzee counterpart were identified by fluorescence in situ hybridization (FISH) and comparative sequence analysis. These breakpoints, at HSA4p14 and 4q21.3, do not disrupt the protein coding region of a gene, although they occur in regions with an abundance of LINE and LTR-elements. At 30 kb proximal to the breakpoint in 4q21.3, we identified an as yet unannotated gene, C4orf12, that lacks an homologous counterpart in rodents and is expressed at a 33-fold higher level in human fibroblasts as compared to chimpanzee. Seven out of 11 genes that mapped to the breakpoint regions have been previously analyzed using oligonucleotide-microarrays. One of these genes, WDFY3, exhibits a three-fold difference in expression between human and chimpanzee. To investigate whether the genomic architecture might have facilitated the inversion, comparative sequence analysis was used to identify an approximately 5-kb inverted repeat in the breakpoint regions. This inverted repeat is inexact and comprises six subrepeats with 78 to 98% complementarity. (TA)-rich repeats were also noted at the breakpoints. These findings imply that genomic architecture, and specifically high-copy repetitive elements, may have made a significant contribution to hominoid karyotype evolution, predisposing specific genomic regions to rearrangements.

Animals↗

Regional chromosomal assignments for four members of the MADS domain transcription enhancer factor 2 (MEF2) gene family to human chromosomes 15q26, 19p12, 5q14, and 1q12-q23.

The MEF2 genes belong to the MADS box family of transcription factors and encode proteins that bind as homo- and heterodimers to a consensus CTA(T/A)4TAG/A sequence, which is present in the regulatory regions of numerous muscle-specific and growth-inducible genes. Sequence analysis of human MEF2 cDNA clones suggests that they arose from alternatively spliced transcripts of four different genes, termed MEF2A-D. We have mapped the MEF2 genes to human chromosomal regions by identifying unique sequences in the MEF2 cDNA clones and using these sequences as PCR primers on the DNA of human-rodent hybrid clone panels that are informative for different regions of the human genome. PCR primers were also used to identify individual YAC clones for two of the genes, MEF2A and MEF2C, and a PCR product was used to identify cosmid clones for MEF2B. Genetic and physical mapping information available from genome databases on markers contained within YAC and cosmid clones provided independent assignments for those genes. Inter-Alu PCR painting probes of YAC clones were used as probes for high-resolution chromosomal regional assignment by fluorescence in situ hybridization. The localization of MEF2A to chromosome 15q26, MEF2B to 19p12, MEF2C to 5q14, and MEF2D to 1q12-q23 verifies the existence of at least four distinct loci for members of this gene family.

Alternative Splicing↗

Fibroadenoma of the breast showing a translocation (6;14), a ring chromosome and two markers involving parts of chromosome 11.

The cytogenetic findings of a recurrent fibroadenoma of a 25-year-old woman are reported. Of 58 metaphases karyotyped after G-banding, 27 showed an apparently normal karyotype and 31 the karyotype 48,XX,del(6)(q21),r(11)(?) + der(11)x2,der(14)t(6;14)(q21;q32). By fluorescence in situ hybridization studies using a chromosome 11 specific painting probe, we were able to show that the two marker chromosomes and the ring contained chromosome 11 DNA.

Adult↗

Evolutionary breakpoints through a high-resolution comparative map between porcine chromosomes 2 and 16 and human chromosomes.

This study reports a high-resolution comparative map between human chromosomes and porcine chromosomes 2 (SSC2) and 16 (SSC16), pointing out new homologies and evolutionary breakpoints. SSC2 is of particular interest because of the presence of several important QTLs. Among 226 porcine ESTs selected according to their expected localization, 151 were RH mapped and ordered on SSC2. This study confirmed the extensive conservation between SSC2 and HSA11 and HSA19 and refined the homology with HSA5 (three blocks defined). Furthermore the SSC2q pericentromeric region was shown to be homologous to another human chromosome (HSA1). A complex organization of these syntenies was demonstrated on SSC2q. Our strategy led us to improve also the SSC16 RH map by adding 45 markers. Two-color fluorescence in situ hybridization of markers representative of each synteny confirmed block order. Finally, 29 breakpoints were identified in both species, and porcine BACs containing two breakpoints were isolated.

Animals↗

A complex chromosome rearrangement involving chromosome 8, 11, and 12 analyzed by conventional cytogenetic investigations, fluorescence in situ hybridisation, and spectral karyotyping.

We report on a 29-year-old woman with a history of five spontaneous abortions and a balanced complex chromosome rearrangement (CCR) involving break points between chromosomes 8, 11, and 12. Fluorescence in situ hybridisation (FISH) in combination with giemsa trypsin banding techniques were essential for the identification of the breakpoints. In addition, the results were confirmed by 24-colour FISH using the spectral karyotyping system (SKY). The karyotype was 46,XX,t(8;11;12)(8qter-->8p10::12p10-->12pter;11pter--> 11q14::8p10-->8pter;12qter-->12p10::11q14-->11qter). Application of SKY facilitated detection of all three chromosomes involved and supported the localisation of the breakpoints by a single time and sample saving investigation.

Abortion, Spontaneous↗

Highly complex chromosomal rearrangement of chromosome 9 in a case of chronic myeloid leukemia.

A 63-year-old man with chronic myeloid leukemia (CML) was found to have a new complex Philadelphia translocation. All of the bone marrow cells had a rearrangement of a five-way translocation, t(9;22;10;12;1), involving a single chromosome 9. The patient went into blast crisis two years after initial diagnosis and the karyotype remained unchanged. He died in blast crisis 10 months later. We believe this case is a unique 5-way translocation in which four chromosomes were translocated to a single chromosome.

Chromosomes, Human, Pair 1↗

Radiation-induced chromosome aberrations analysed by two-colour fluorescence in situ hybridization with composite whole chromosome-specific DNA probes and a pancentromeric DNA probe.

Fluorescence in situ hybridization with composite whole chromosome-specific DNA probes for human chromosomes 1, 4 and 12 and a degenerate alpha-satellite pancentromeric DNA probe labelled with digoxigenin was used to measure symmetrical translocations and dicentrics induced in vitro by 137Cs gamma-rays (0-6.0 Gy) in peripheral lymphocytes. Despite subtracting our mean background translocation frequency of 0.0016 per cell (11,411 cells scored from 11 individuals) from induced frequencies, about 1.3-1.8-fold more translocations were found than dicentrics at a given dose. Translocation frequencies determined only in stable cells agree well with total translocation frequencies determined also in cells containing additional unstable chromosomal changes. The linear quadratic calibration curve generated for total stable translocations is based on approx. 17,000 cells. The suitability of this curve for biological dosimetry of human radiation exposure can now be evaluated in comparison with dose estimates based on a conventional dicentric dose-response curve.

Cesium Radioisotopes↗

Significant differences in the frequency of transcriptional units, types and numbers of repetitive elements, GC content, and the number of CpG islands between a 1010-kb G-band genomic segment on chromosome 9q31.3 and a 1200-kb R-band genomic segment on chromosome 3p21.3.

We determined the nucleotide sequence of the entire 1,010,525-bp insert contained in CEPH YAC clone 867e8. This human genomic segment was derived from chromosome 9q31.3 and corresponds to a G-band region. We compared this segment, in terms of structure, with a previously characterized 1,201,033-bp sequence in CEPH YAC936c1 that had come from a portion of human chromosome 3p21.3 corresponding to an R-band region. The two segments were significantly different with respect to the frequency of transcriptional units, the types and numbers of repetitive elements present, their GC content, and the number of CpG islands. Alu elements, GC content, and CpG islands all showed positive correlations with the abundance of exons, but the distribution of LINE1s did not. These observations might reflect an influence of the first three of these features on the functions or expression of genes in the respective regions. In addition to a novel gene (F36) lying at the centromeric end of the 9q segment, we found a cluster of placenta-specific genes within a small section (about 400 kb) on the telomeric side of YAC867e8. This cluster consisted of four apparently unrelated ESTs and two genes, pregnancy-associated plasma protein-A (PAPP-A) and a novel gene (tentatively named EST-YD1). Our characterization of the two chromosomal regions provided evidence that genes are not evenly distributed throughout the human genome, and that gene richness is correlated with the GC content and with the frequency of either Alu elements or CpG islands.

Alu Elements↗

Application of fluorescence in situ hybridization techniques in clinical genetics: use of two alphoid repeat probes detecting the centromeres of chromosomes 13 and 21 or chromosomes 14 and 22, respectively.

Two cloned DNA fragments, one derived from an alpha satellite subfamily common to chromosomes 13 and 21, and the other derived from a similar subfamily common to chromosomes 14 and 22, have been used as biotinylated probes in in situ hybridization studies. Under high stringency conditions, chromosome specific centromeric labelling can be obtained. The applications of this technique in clinical situations are illustrated on metaphases from a fetus with trisomy 21, a fetus with trisomy 13, and a child with clinical features of cat-eye syndrome.

Centromere↗

Improving the comparative map of porcine chromosome 9 with respect to human chromosomes 1, 7 and 11.

Conserved segments have been identified by ZOO-FISH between pig chromosome 9 (SSC9) and human chromosomes 1, 7 and 11. To assist in the identification of positional candidate genes for QTL on SSC9, the comparative map was further developed. Primers were designed from porcine EST sequence homologous to genes in regions of human chromosomes 1, 7 and 11. Porcine ESTs were then physically assigned using the INRA somatic cell hybrid panel (INRASCHP) and the high-resolution radiation hybrid panel (IMpRH). Seventeen genes (PEPP3, RAB7L1, FNBP2, MAPKAPK2, GNAI1, ABCB1, STEAP, AKAP9, CYP51A1, SGCE, ROBO4, SIAT4C, GLUL, CACNA1E, PTGS2, C1orf16 and ETS1) were mapped to SSC9, while GUSB, CPSF4 and THG-1 were assigned to SSC3.

Animals↗

Human chromosomal heteromorphisms in Delhi newborns. II. Analysis of C-band size heteromorphisms in chromosomes 1, 9 and 16.

Quantitative analysis of C-band size heteromorphisms in chromosomes 1,9 and 16 was carried out in 200 Delhi newborns (100 males and 100 females). The percent size heteromorphisms for chromosomes 1,9 and 16 showed nonsignificant differences between the sexes. Homozygous size level combinations showed higher incidence than the heterozygous combinations for all the three chromosome pairs studied in both sexes. Our results are compared with other reported studies and the possible role of these heteromorphisms in ethnic/racial variation and in developmental disturbances is discussed.

Chromosome Banding↗