Showing papers on "Heterochromatin published in 1987"
TL;DR: It is hypothesize that the structure of mouse satellite DNA is an important feature of centromeric heterochromatin condensation, and that satellite does not comprise a single block but is distributed throughout the centromere region.
184 citations
TL;DR: Interphase chromosome organization in four different Drosophila melanogaster tissues, covering three to four levels of polyteny, has been analyzed to provide insights into chromosome growth and substructure and also suggest an unexpected parallel with diploid chromatin organization.
Abstract: Interphase chromosome organization in four different Drosophila melanogaster tissues, covering three to four levels of polyteny, has been analyzed. The results are based primarily on three-dimensional reconstructions from unfixed tissues using a computer-based data collection and modeling system. A characteristic organization of chromosomes in each cell type is observed, independent of polyteny, with some packing motifs common to several or all tissues and others tissue-specific. All chromosomes display a right-handed coiling chirality, despite large differences in size and degree of coiling. Conversely, in each cell type, the heterochromatic centromeric regions have a unique structure, tendency to associate, and intranuclear location. The organization of condensed nucleolar chromatin is also tissue-specific. The tightly coiled prothoracic gland chromosomes are arrayed in a similar fashion to the much larger salivary gland chromosomes described previously, having polarized orientations, nonintertwined spatial domains, and close packing of the arms of each autosome, whereas hindgut and especially the unusually straight midgut chromosomes display striking departures from these regularities. Surprisingly, gut chromosomes often appear to be broken in the centric heterochromatin. Severe deformations of midgut nuclei observed during gut contractions in living larvae may account for their unusual properties. Finally, morphometric measurements of chromosome and nuclear dimensions provide insights into chromosome growth and substructure and also suggest an unexpected parallel with diploid chromatin organization.
120 citations
TL;DR: Recent advances in banding technology and in sequencing DNA replication using isotype-labeled nucleotides and BrdU have rendered the metaphase chromosomes amenable for investigations, and the terms “euchromatin” and “heterochromatic” are discussed.
Abstract: Publisher Summary This chapter discusses the terms “euchromatin” and “heterochromatin” that have long been familiar for expressing primarily the state of chromatin condensation during the cell cycle. The term “heterochromatin,” in particular, has been used to describe such chromatin or chromosome segments that did not go through the uncoiling process toward the end of mitosis and so remained condensed throughout interphase. Usually this condensed state of chromatin results in a heteropyknotic property. On the other hand, the chromatin that uncoils in the subsequent interphase is considered euchromatin. The earlier studies on different chromatintypes were based on the staining variation in interphase nuclei. Similar studies using metaphase chromosomes were limited to those species where the heterochromatic segments were recognizable from the staining differences by conventional methods. However, recent advances in banding technology and in sequencing DNA replication using isotype-labeled nucleotides and BrdU have rendered the metaphase chromosomes amenable for such investigations. In metaphase chromosomes, the regions stained by the C-banding method and the latereplicating X chromosome (in females) are regarded as heterochromatic. The remaining regions are referred to as “euchromatic.”
93 citations
TL;DR: A survey of 51 species from Nicotiana subgg.Tabacum, Rustica andPetunioides has shown that evolution was accompanied by a five-fold variation in nuclear DNA amounts, however, this variation was not directly correlated with the changes in chromosome number.
Abstract: A survey of 51 species fromNicotiana subgg.Tabacum, Rustica andPetunioides has shown that evolution was accompanied by a five-fold variation in nuclear DNA amounts. This variation, however, was not directly correlated with the changes in chromosome number. Drastic rearrangement of karyotypes is characteristic for the evolution ofNicotiana spp. Significant gain or loss in nuclear DNA has often accompanied such changes, but DNA variation has also occurred without significant changes in karyotype arrangements.—The distribution of nuclear DNA is discontinuous inNicotiana, species cluster into DNA groups with consistently regular increments in the mean DNA amounts. The discontinuities are viewed as “steady states” in terms of genomic balance and biological fitness.—Changes in the amount of nuclear DNA and in the heterochromatin are compared with the morphological, chromosomal and adaptive changes which accompanied speciation in 14 subgeneric sections. The evolutionary significance of DNA variation is discussed.
87 citations
TL;DR: The fluorochrome and Giemsa chromosome banding patterns and the Ag-NOR histochemical staining of Sinapis alba are described and two major types of heterochromatin can be distinguished.
Abstract: The fluorochrome and Giemsa chromosome banding patterns and the Ag-NOR histochemical staining ofSinapis alba are described. Two major types of heterochromatin can be distinguished, one of which contains GC-rich DNA. The observations are discussed as they relate to the known satellite DNAs ofS. alba. — A simple air-drying technique for producing spreads of plant mitotic chromosomes is presented. Different materials and staining techniques were tested showing that the method has wide applications.
73 citations
TL;DR: In this paper, the karyotypes of 14 species of Anura from 9 genera of the suborders Amphicoela, Aglossa, Opisthocoela and Anomocoela were analyzed with various banding techniques and conventional cytogenetic methods.
Abstract: The karyotypes of 14 species of Anura from 9 genera of the suborders Amphicoela, Aglossa, Opisthocoela and Anomocoela were analysed with various banding techniques and conventional cytogenetic methods. The 18S + 28S and 5S ribosomal RNA genes were localized by means of in situ hybridization. No Q-, R- and G-banding patterns in the euchromatic segments of the metaphase chromosomes could be demonstrated in any of the species; this does not seem to be caused by a higher degree of spiralization of the amphibian chromosomes, but by the special DNA organization in these organisms. In most karyotypes, constitutive heterochromatin is present at centromeres, telomeres and nucleolus organizer regions (NORs), but rarely in interstitial positions. The heterochromatic regions are either quinacrine positive and mithramycin negative or vice versa. All species examined possess only one homologous pair of NORs: these display the brightest mithramycin fluorescence in the karyotypes. Many specimens exhibited unequal labelling of the two NORs both after silver and mithramycin staining as well as after in situ hybridization with 3H-18S + 28S rRNA. In four species, between one and six chromosome pairs with homologous 5S rRNA sites could be identified. The 5S rRNA genes and the 18S + 28S rRNA genes are closely linked in two species. In the male meiosis of the Amphicoela and Opisthocoela, there are intersitial, subterminal and terminal chiasmata in the bivalents, whereas only terminal chiasmata are observed in the bivalents of the Aglossa and Anomocoela. No heteromorphic sex-specific chromosomes could be demonstrated in any of the species. The differential staining techniques revealed that the chromosomal structure in these four suborders is largely the same as in the highly evolved anuran suborders Procoela and Diplasiocoela.
70 citations
Journal Article•
TL;DR: Results are interesting because nickel(II), which is thought to be the ultimate carcinogen of nickel compounds, binds poorly to DNA, is weakly mutagenic, but induces chromosome damage, probably because of its interaction with nuclear proteins in heterochromatin.
Abstract: Chromosomal aberrations were studied in Chinese hamster ovary cells and in C3H10T½ cells following treatment with NiCl2, crystalline NiS, and CaCrO4. All three compounds caused an increase in chromosomal aberrations in a concentration- and time-dependent fashion. The chromosomal aberrations induced by NiCl2, and crystalline NiS occurred predominantly in heterochromatic regions of the chromosomes. Additionally, treatment of cells with crystalline NiS and to a smaller extent long-term treatment with NiCl2 caused a preferential effect on the condensation state of the heterochromatic long arm of the X-chromosome in hamster cells. In contrast, treatment of cells with CaCrO4 did not induce aberrations preferentially in heterochromatin. These results are interesting because nickel(II), which is thought to be the ultimate carcinogen of nickel compounds, binds poorly to DNA, is weakly mutagenic, but induces chromosome damage, probably because of its interaction with nuclear proteins in heterochromatin. Chromate binds to DNA, is mutagenic, and interacts with chromatin randomly.
65 citations
TL;DR: Chicken chromosomes were identified up to No. 18 by a sequential counterstain-enhanced fluorescence technique and a heterochromatin characterization was performed; in general, the microchromosomes were GC-rich, but with high degree of variation.
Abstract: Chicken chromosomes were identified up to No. 18 by a sequential counterstain-enhanced fluorescence technique. A heterochromatin characterization of macro- and microchromosomes was performed; in general, the microchromosomes were GC-rich, but with a high degree of variation. The NORs are localized on chromosome No. 17.
60 citations
TL;DR: Elevation of extracellular magnesium levels prevented the effects of nickel on heterochromatin and inhibited cell transformation, but did not substantially reduce the DNA damage induced by nickel in euchromatic regions.
Abstract: Raising the extracellular level of magnesium ions inhibited nickel-induced DNA strand breaks, DNA-protein crosslinks, sister chromatid exchanges, chromosomal aberrations and cell transformation. Carcinogenic nickel ions preferentially damaged centromeres and other heterochromatic regions of Chinese hamster ovary cell chromosomes. Elevation of extracellular magnesium levels prevented the effects of nickel on heterochromatin and inhibited cell transformation, but did not substantially reduce the DNA damage induced by nickel in euchromatic regions. This study suggests that heterochromatic DNA damage may be important to the nickel-induced neoplastic transformation process.
59 citations
TL;DR: Perturbations in the replication of heterochromatic regions during tissue culture may be the cause of chromosome alterations observed in regenerated hexaploid oat plants (Avena sativa L.).
Abstract: Perturbations in the replication of heterochromatic regions during tissue culture may be the cause of chromosome alterations observed in regenerated hexaploid oat plants (Avena sativa L.). An idiog...
53 citations
TL;DR: The observed variation in the content of repetitive DNA together with genetical, biological and geological data, support the hypothesis that Artemia living in the New World are derived from ancestral species that evolved in the Mediterranean area.
Abstract: The genus Artemia (Crustacea, Phyllopoda) is widely distributed all over the world as a result partly of natural colonization and partly of spread by birds and man. Artemia offers a very interesting model for speciation studies, since the genus comprises both bisexual sibling species and parthenogenetic populations, exhibiting different chromosome numbers (diploidy, heteroploidy and polyploidy). The finding of the clustered repetitive AluI DNA family in the heterochromatin of A. franciscana can provide a useful tool for investigating the relationship between the members of the genus Artemia at the molecular level. Sixteen strains of Artemia, comprising sibling species and parthenogenetic populations, were analysed for the presence of AluI repetitive DNA by dot-blot hybridization. The observed variation in the content of repetitive DNA together with genetical, biological and geological data, support the hypothesis that Artemia living in the New World are derived from ancestral species that evolved in the Mediterranean area.
TL;DR: This report presents C-banded karyotypes for 17 North American species, and discusses with respect to the chromosomal distribution of constitutive heterochromatin, euchromatic rearrangements, and interspecific C- band differences.
Abstract: Development of the C-banding procedure has enabled identification of the amount and location of constitutive heterochromatin (C-bands) in the karyotypes of many species. One group of mammals that has received considerable attention in this regard is the rodents. C-band data are currently available for species belonging to a number of rodent groups including the following familiar ones: sciurids, geomyids, heteromyids, New World cricetids, Old World cricetids, Eurasian murids, Australian murids and octodontids. Patton and Sherwood (1983) summarized chromosomal evolution among rodents and indicated that the following four categories of C-band variation have been observed: (a) differences in the amount of centromeric heterochromatin, (b) variability in the number of autosomal heterochromatic short arms, (c) presence or absence of telomeric or interstitial autosomal C-bands, and (d) variation in sex chromosome heterochromatin. The family Arvicolidae (voles, lemmings, and muskrats) is taxonomically diverse, containing more than 120 species. This group occurs in the temperate regions of North America and Eurasia, includes species that occupy a wide array of habitats, and has attracted considerable interest from classical taxonomists, population biologists, and behaviorists. However, the approximately 40 species of New World arvicolids have received little attention from comparative cytogeneticists utilizing differential staining procedures. Detailed banding data have been reported for fewer than 15 species (Judd, 1980; Judd et al., 1980; Modi, 1986; Nadler et al., 1976; Rausch and Rausch, 1975; Zenzes and Voiculescu, 1975) and no comprehensive statements regarding chromosomal evolution have been made. This report presents C-banded karyotypes for 17 North American species. These data are tabulated along with information from the literature concerning additional New World and Old World species, and are discussed with respect to the chromosomal distribution of constitutive heterochromatin, euchromatic rearrangements, and interspecific C-band differences.
TL;DR: The similarity of the results obtained with the three probes suggests that heterogeneous Sau3A repeats share the same chromosomal localizations and that the two analyzed genomic sectors may not contain significant amounts of repetitive DNAs other than the Sau2A family.
Abstract: The Sau3A family is a human, clustered, highly repetitive, GC-rich DNA family. In situ hybridization studies with a plasmid carrying a Sau3A monomer as a probe have shown that Sau3A sequences are preferentially concentrated in the heterochromatic regions of human acrocentric chromosomes (D and G groups, both in pericentromeric regions and in cytological satellites) and in pericentromeric heterochromatin of chromosome 1. The same chromosomal locations were observed by using as probes two recombinant phages which carry Sau3A-positive genomic sectors. The two sectors differfor the relative proportions of monomer and multiples of Sau3A repeats, which show different extents of homology to the cloned monomer, and for the presence, in one of the two, of a samll amount of an unrelated repeat (alphoid DNA). The similarity of the results obtained with the three probes suggests that heterogeneous Sau3A repeats share the same chromosomal localizations and that the two analyzed genomic sectors may not contain significant amounts of repetitive DNAs other than the Sau3A family. A comparison between the chromosomal locations of Sau3A and EcoRI families of repeats has confirmed that each family is characterized by specific chromosomal locations and that single heterochromatic regions may contain both.
Journal Article•
TL;DR: Alphoid repeats from specific chromosomes are similar in that there is no evidence for their transcription in lymphoblasts and fibroblasts, and it is demonstrated the possibility that all of these sequences are late replicating.
Abstract: The alphoid DNA family is composed of tandemly repeated sequences whose organization is chromosome specific Under stringent conditions of hybridization, subsets of these sequences localize specifically to the centromeric region of a given chromosome The alphoid clone, 308 (D6Z1), is a 3-kb BamHI DNA fragment that is repeated at the centromere of chromosome 6 Sequences homologous to 308 are organized as 2-kb BamHI repeats on X We used 308 to screen a 2-kb BamHI genomic library and obtained the cloned homologue, XC, which hybridizes, in situ, to the centromere of X These probes provide a means of analyzing the centromeric region on two different human chromosomes The complete nucleotide sequence of 308 shows that it is composed of 20 variant 173-bp repeats The organization of the 173-bp monomers is not a repetitious but a symmetric pattern, and an inversion is present The chromosome specificity of 308 to chromosome 6 is determined by the entire 3-kb sequence and not by an amplified 173-bp monomer, because the divergence among the 173-bp units on chromosome 6 is as great as that between monomers on chromosomes 6 and X Therefore, the organization of monomers is specific for a chromosome, and the monomers themselves are not specific Analysis of the sequence data from these two alphoid sequences and other published sequences shows that some chromosomes have sequences that are more homologous than others These subsets of alphoid sequences reflect the latters' chromosomal distribution and evolution By using probes 308 and XC, we found that alphoid repeats from specific chromosomes are similar in that there is no evidence for their transcription in lymphoblasts and fibroblasts, and we demonstrated the possibility that all of these sequences are late replicating
TL;DR: In situ hybridization of cloned satellite DNA sequences may be used as a new general approach to analysis of chromosome heteromorphisms in man, indicating that constitutive heterochromatin of human chromosomes has a variable amount of alphasatellite DNA sequences.
Abstract: The cloned alpha-satellite DNA sequences were used to evaluate the specificity and possible variability of repetitive DNA in constitutive heterochromatin of human chromosomes. Five probes with high specificity to individual chromosomes (chromosomes 3, 11, 17, 18, and X) were in situ hybridized to metaphase chromosomes of different individuals. The stable position of alpha-satellite DNA sequences in heterochromatic regions of particular chromosomes was found. Therefore, the chromosome-specific alpha-satellite DNA sequences may be used as molecular markers for heterochromatic regions of certain human chromosomes. The homologous chromosomes of many individuals were characterized by cytologically visible heteromorphisms of hybridization intensity with chromosome-specific alpha-satellite DNA sequences. A special analysis of hybridization between homologues with morphological differences provided the evidence for a high resolution power of the in situ hybridization technique for evaluation of chromosome heteromorphisms. The approaches for detection of heteromorphisms in cases without morphological differences between homologues are discussed. The results obtained indicate that constitutive heterochromatin of human chromosomes has a variable amount of alphasatellite DNA sequences. In situ hybridization of cloned satellite DNA sequences may be used as a new general approach to analysis of chromosome heteromorphisms in man.
TL;DR: In situ hybridization experiments demonstrate the wide distribution of (CA/GT)n repeats within the genome of Drosophila hydei and a possible biological role of ( CA/ GT)n sequences, which has been the subject of controversy among various investigators, is their involvement in the control of the rate of transcription.
Abstract: In situ hybridization experiments demonstrate the wide distribution of (CA/GT)n repeats within the genome of Drosophila hydei. (CA/GT)n sequences are evenly distributed in the euchromatin of autosomes and the X chromosome but are not present in most of the heterochromatin of the sex chromosomes. Both sex chromosomes carry one large block of (CA/GT)n. At least part of this (CA/GT)n cluster in the Y chromosome is transcribed in a strandspecific manner and at a high rate in primary spermatocyte nuclei. Also, in polytene chromosomes, specific transcription of (CA/GT)n sequences is found in certain puffs as demonstrated by transcript in situ hybridization. The X chromosomal euchromatin carries approximately twice as much (CA/GT)n over its entire length as the autosomes. These observations are discussed with respect to the mechanisms of dosage compensation and position-effect variegation. A possible biological role of (CA/GT)n sequences, which has been the subject of controversy among various investigators, is their involvement in the control of the rate of transcription.
TL;DR: It is noteworthy, however, that the heterochromatin associated with NORs is not attacked by any of the enzymes the authors used, while regions believed to contain AT-rich DNA (DA-DAPI positive) are digested by Hae III that cleaves the GG↓CC base sequence target.
Abstract: Fixed mitotic chromosomes of A. tornosi have been analysed by means of C-banding, DA-DAPI and Chromomicin A3 fluorescence, as well as by digestion in situ with Alu I, Hae III, Hinf I and Hind III restriction endonucleases. From the results obtained at least nine types of chromatin can be distinguished in A. tornosi. Some C-band positive areas (constitutive heterochromatin) which show a characteristic fluorescence pattern are digested by specific endonucleases, whilst others are undigested. C-band negative areas (euchromatin) are digested by some restriction endonucleases but not by others. Regions digested are supposed to contain highly repetitive DNAs. It is noteworthy, however, that the heterochromatin associated with NORs is not attacked by any of the enzymes we used, while regions believed to contain AT-rich DNA (DA-DAPI positive) are digested by Hae III that cleaves the GG decreases CC base sequence target.
TL;DR: The main conclusions are that this phylogeny is compatible with the occurrence during evolution of simple chromosome rearrangements — inversions, fusions, reciprocal translocation, acquisition or loss of heterochromatin — and that it is entirely consistent with the known primate phylogeny based on physical morphology and molecular evolution.
Abstract: The karyotypes of man and of the closely related Pongidae — chimpanzee, gorilla, and orangutan — differ by a small number of well known rearrangements, mainly pericentric inversions and one fusion which reduced the chromosome number from 48 in the Pongidae to 46 in man. Dutrillaux et al. (1973, 1975, 1979) reconstructed the chromosomal phylogeny of the entire primate order. More and more distantly related species were compared thus moving backward in evolution to the common ancestors of the Pongidae, of the Cercopithecoidae, the Catarrhini, the Platyrrhini, the Prosimians, and finally the common ancestor of all primates. Descending the pyramid it becomes possible to assign the rearrangements that occurred in each phylum, and the one that led to man in particular. The main conclusions are that this phylogeny is compatible with the occurrence during evolution of simple chromosome rearrangements — inversions, fusions, reciprocal translocation, acquisition or loss of heterochromatin — and that it is entirely consistent with the known primate phylogeny based on physical morphology and molecular evolution. If heterochromatin is not taken into account, man has in common with the other primates practically all of his chromosomal material as determined by chromosome banding. However, it is arranged differently, according to species, on account of chromosome rearrangements. This interpretation has been confirmed by comparative gene mapping, which established that the same chromosome segments, identified by banding, carry the same genes (Finaz et al., 1973; Human Gene Mapping 8, 1985). A remarkable observation made by Dutrillaux is that different primate phyla seem to have adopted different chromosome rearrangements in the course of evolution: inversions for the Pongidae, Robertsonian fusions for the lemurs, etc. This observation may raise many questions, among which is that of an organized evolution. Also, the breakpoints of chromosomal rearrangements observed during evolution, in human chromosomal diseases, and after ionizing irradiation do not seem to be distributed at random. Chromosomal rearrangements observed in evolution are known to be harmful in humans, leading to complete or partial sterility through abnormal offspring in the heterozygous state but not in the homozygous state. They then become a robust reproductive barrier capable of creating new species, far more powerful than gene mutations advocated by neo-Darwinism. The homozygous state may be achieved especially through inbreeding, which must have played a major role during primate evolution. Whether new species derive from unique individuals or couples (Adam and Eve), or through a “populational” process, remains a matter for discussion.
TL;DR: A critical analysis of this parameter of cell cycle suggests that the sequence of centromere separation is influenced by repetitive DNA present in the pericentric region, and one property of repetitive DNA in the centromeric region appears to be the maintenance of diploidy.
Abstract: The centromeres of a mitotic cell at the meta-anaphase junction separate in a non-random, genetically controlled sequence before anaphase migration ensues. In several, but not all, of the organisms studied so far it appears that the timing of separation of a centromere into two visible units depends upon the quantity of pericentric heterochromatin. A critical analysis of this parameter of cell cycle suggests that the sequence of centromere separation is influenced by repetitive DNA present in the pericentric region. In those cases with qualitatively uniform repetitive DNA in centromeric regions, the chromosomes carrying lesser quantities separate earlier than those with greater amounts. However, the overall pattern of separation may be determined by interactions between both quantitative and qualitative parameters of the repetitive DNA. It has been suggested that repetitive DNA has no transcriptional properties. It is probably only a structural component which acts as a site for the accumulation of protein molecules synthesized by some locus not present in the centromeric region. These proteins accumulate to saturate the centromeric repetitive DNA resulting in a (trilaminar) structure called the kinetochore. The longer the stretch to be saturated, the larger would be the kinetochore-like structure. Once saturated, the centromere splits into two subunits. Premature separation results in a lack of saturation and formation of an 'immature' kinetochore. This may lead to chromosome malsegregation. Thus, indirectly, one property of repetitive DNA in the centromeric region appears to be the maintenance of diploidy.
TL;DR: Three patients with 45,X/46,XYnf mosaicism were investigated by Southern hybridization using both X- and Y-specific DNa probes, indicating structural heterogeneity of the marker chromosome and providing further information on the relative position of DNa sequences detectected by DNA probes 50f2, M1A, and pDP105.
Abstract: Three patients with 45,X/46,XYnf mosaicism were investigated by Southern hybridization using both X- and Y-specific DNa probes. Our patients seem to be hemizygous for the X chromosomal loci tested. Single-copy and low-copy repeated Y chromosomal sequences assigned to the short arm, centromere, and euchromatin of the long arm have been detected in our patients, suggesting the Y chromosomal origin of the marker chromosome both in male and female cases studied. Densitometry of autoradiographs revealed a double dose of Yp-specific fragments of the DXYS1 locus. None of the patients tested showed either the 3.4- or the 2.1-kb Hae III malespecific repeated DNa sequences. It seems likely that the Ynf is a pseudodicentric chromosome with duplication of Yp and euchromatic Yq sequences, the Yq heterochromatin being lost. Our findings indicate structural heterogeneity of the marker chromosome and in addition provide further information on the relative position of DNa sequences detectected by DNA probes 50f2, M1A, and pDP105.
TL;DR: The chromatin structure of six diploids species ofCostus was analysed using conventional Giemsa staining, C-banding and DAPI/CMA fluorochromes to mean that the greater part of the condensed chromatin has an euchromatic nature whereas two types of well localized heterochromatin occur in a small proportion.
Abstract: The chromatin structure of six diploids species ofCostus was analysed using conventional Giemsa staining, C-banding and DAPI/CMA fluorochromes. The interphase nuclei in all the species show an areticulate structure and the prophase chromosomes show large blocks of proximal condensed chromatin. After banding procedures, each chromosome exhibits only centromeric dot-like DAPI+/CMA− C-bands whereas the satellites (one pair at each karyotype) are weakly stained after C-banding and show a DAPI−/CMA+ fluorescence. Two chromocentres show bright fluorescence with CMA and weak staining after C-banding whereas the others chromocentres show only a small fraction of DAPI+ heterochromatin. These results were interpreted to mean that the greater part of the condensed chromatin has an euchromatic nature whereas two types of well localized heterochromatin occur in a small proportion. The Z-stage analysis suggests that heterochromatin and condensed euchromatin decondense at different times. The chromosome number and morphology of all species are given and the implications of the condensed euchromatin are discussed.
TL;DR: It is concluded that--as has already been shown for insects and amphibians--also in mammals, constitutive heterochromatin is transcribed in its decondensed state but is genetically inactive when forming chromocenters at interphase.
TL;DR: The results obtained by treating the metaphase chromosomes of Pan troglodytes, Pan paniscus, and Gorilla gorilla with the restriction enzyme AluI suggest the presence, in great apes, of some highly repetitive DNA sequences different from the human satellites I-IV.
Abstract: Restriction endonucleases have recently been proved to be active on fixed chromatin, producing differences in staining of metaphase chromosomes. In this paper we show the results obtained by treating the metaphase chromosomes of Pan troglodytes, Pan paniscus, and Gorilla gorilla with the restriction enzyme AM. These results demonstrate qualitative differences in the telomeric heterochromatin between Pan and Gorilla despite the fact that these areas appear homogeneous in the two genera by the C-banding method. The results found with individual chromosomes in the different species also appear relevant, in the light of the evolutionary relationships between these nonhuman primates and man. Lastly, the results suggest the presence, in great apes, of some highly repetitive DNA sequences different from the human satellites I IV.
TL;DR: Pairing frequencies within rye and wheat genomes were correlated in all groups of lines and Lines without wheat chromosome 3B showed reduced pairing in both genomes, while lines with an additional pair of 5R chromosomes substituted for group-5 wheat chromosomes showed improved pairing of the rye genome but not of the wheat genome.
Abstract: Among 38 lines of tetraploid triticale analyzed at meiosis, the number of paired arms per rye chromosome ranged from 1.14 to 1.76 and from 1.46 to 1.96 per wheat chromosome. The frequency of cells without univalents ranged from 22 to 90%. Pairing frequencies within rye and wheat genomes were correlated in all groups of lines. Lines without wheat chromosome 3B showed reduced pairing in both genomes, while lines with an additional pair of 5R chromosomes substituted for group-5 wheat chromosomes showed improved pairing of the rye genome but not of the wheat genome. In the rye genome, the chromosome arms that carry major blocks of telomeric heterochromatin paired with an average of 25.1% lower frequency than the arms without the telomeric heterochromatin, the difference being attributed to the difference in arm length and not to the presence of heterochromatic blocks. In the wheat genome, chromosome arms IBS, 5AS, and 5BS and chromosomes 4A and 7B paired with significantly lower frequency than the remaining a...
TL;DR: There is a correlation between fragile sites, deletion sites, and karyotypic changes in the X chromosome of the Indian mole rat, Nesokia indica, and the mechanism by which fragile sites influence reproductive performance is unclear.
Abstract: Folate-sensitive fragile sites have been demonstrated on the X chromosome of the Indian mole rat, Nesokia indica (subfamily Murinae), utilizing peripheral blood lymphocyte cultures. All normal female individuals expressed fragile sites on the constitutive heterochromatic long arm of one of their two X chromosomes (heterozygous expression); in contrast, no fragile sites were found on the single X chromosome of normal males. Preferential transmission of the maternal fragile X to the daughters is therefore suggested. Four sites have been detected so far: fra Xq1, fra Xq2, fra Xq3, and fra Xc (centromeric). It is significant that their location corresponds to the regions where constitutive heterochromatic deletions occur that result in a variety of polymorphic X chromosomes in natural populations of Nesokia. Thus there is a correlation between fragile sites, deletion sites, and karyotypic changes. In individuals that did not reproduce in the laboratory, there were more fragile sites on both X chromosomes of the females (homozygous/double heterozygous expression) and also on the X of the males (hemizygous expression). This difference in fragile site expression from the normal situation could be attributed to one or more new mutations. However, the mechanism by which fragile sites influence reproductive performance is unclear.
TL;DR: The results suggest that centromeres of Indian muntjac chromosomes contain at least four different types of repetitive DNA that are distinct from each other and different from those of other chromosomes.
Abstract: The longitudinal differentiation of metaphase chromosomes of the Indian muntjac was studied by digestion with restriction enzymes, in situ hybridization with cloned DNA probes and distamycin A plus DAPI (4′-6-diamidino-2-phenylindole) fluorescence staining. The centromeric regions of chromosomes 3 and 3 + X of a male Indian muntjac cell line were distinct from each other and different from those of other chromosomes. Digestion with a combination of EcoRI* and Sau3A revealed a pattern corresponding to that of C-banding. Digestion with AluI, EcoRII or RsaI yielded a band specific to the centromeric region only in chromosomes 3 and 3 + X. Furthermore, HinfI digestion yielded only a band at the centromeric region of chromosome 3, whereas DA-DAPI staining revealed a single band limited to the extreme end of the C-band heterochromatin of the short arm of 3 + X. These results suggest that centromeres of Indian muntjac chromosomes contain at least four different types of repetitive DNA. Such diversity in heterochromatin was also confirmed by in situ hybridization using specific DNA probes isolated and cloned from highly repetitive DNA families. Heterozygosity between chromosome homologs was revealed by restriction enzyme banding. Evidence is presented for the presence of nucleolus organizer regions (NORs) on the long arm of chromosome 1 as well as on the secondary constrictions of 3 and 3 + X.
TL;DR: The evidence suggests that induction of single-strand breaks in DNA may be a general feature in the evolution of differentiated somatic cells and the selective advantage of the endogenously produced DNA strand breaks may be to provide an additional mechanism that prevents the differentiated cell from replicating its genome in the absence of an appropriate proliferative signal.
Abstract: During the differentiation of the clonally distributed lymphocytes of mouse and man into mature resting B and T cells, their DNA becomes tightly packed into dense heterochromatin masses and exhibits very little transcriptional activity; it also becomes extensively nicked, containing some 3000–4000 single-strand breaks per diploid genome The nuclear matrix is sparse and poorly organized and there are but trace amounts of the matrix-linked enzyme DNA topoisomerase II; the nucleus of these small cells is surrounded by a thin rim of cytoplasm The resting cell can thus be considered (by analogy to a sperm cell) as a vector for transporting tightly packed and relatively inert genetic information to all parts of the body When the lymphocyte is stimulated to enter a proliferative cycle by binding of appropriately presented antigen or mitogen to relevant membrane receptors, the cell enlarges, due to increased synthesis of protein; the dense heterochromatin is pulled out into very small clumps, as a result of an enormous growth in size as well as complexity of the nuclear matrix, and a great increase in transcriptional activity occurs We have identified four nuclear matrix antigens that are very widely conserved in the evolution of eucaryotes and that occupy distinctive domains in interphase nuclei Of particular interest is antigen P1, detected in organisms ranging from algae to mammals By virtue of its location at the interface between nuclear envelope and chromatin, we propose that it plays a major and evolutionarily conserved role in chromatin organization and orientation in all eucaryotic cell types Prior to these events, the DNA strand breaks are rejoined by a mechanism dependent on poly(ADP ribose) synthetase; rejoining of the breaks is required in order for the cells to enter the S phase of the cell cycle Under certain experimental conditions, the induction of DNA topoisomerase II is clearly seen to precede DNA replication; topoisomerase II may be involved in some of the nuclear changes of blastogenesis The evidence suggests that induction of single-strand breaks in DNA may be a general feature in the evolution of differentiated somatic cells The selective advantage of the endogenously produced DNA strand breaks may be to provide an additional mechanism that prevents the differentiated cell from replicating its genome in the absence of an appropriate proliferative signal
TL;DR: Analysis of C-banded and distamycin A/DAPI-stained diakineses revealed a trefoil-like XY bivalent, which was interpreted to be the result of an interstitial chiasma occurring in the paired short arms of the X and the Y.
Abstract: Both light and electron microscopy were used to study the pairing behavior of the sex chromosomes of the harvest mouse, Micromys minutus, in surface-spread pachytene spermatocytes. The XY pairing pattern is very exceptional in that the site of synaptic initiation is located interstitially in the short arms of the X and the Y, next to their centromeric regions. From this tiny euchromatic site, synapsis proceeds unidirectionally along the homologous heterochromatic short arms of the X and the Y toward the ends of the chromosomes. After pairing of the short arm is concluded, synapsis begins between the nonhomologous long arms of the X and the Y in the immediate vicinity of the centromeres and progresses unidirectionally toward the end of the long arm of the Y. A synaptic complex develops between the constitutive heterochromatin of the long arm of the Y and the euchromatin of the long arm of the X. Analysis of C-banded and distamycin A/DAPI-stained diakineses revealed a trefoil-like XY bivalent, which was interpreted to be the result of an interstitial chiasma occurring in the paired short arms of the X and the Y. A conspicuous, electron-dense body, about 1 micron in diameter, was found closely associated with the centromeres of the X and the Y in numerous pachytene spermatocytes. A review of the literature showed that comparable XY-associated bodies have been found in only eight other mammals to date.
Journal Article•
TL;DR: Autoantibodies to 2 types of DNA binding protein complexes, the nuclear lamina and p70/p80 (Ku), were identified in sera of patients with collagen vascular diseases and may be useful probes for studying both chromatin organization and the causes of autoimmune diseases such as systemic lupus erythematosus.
Abstract: Certain DNA binding proteins are thought to organize the mammalian genome into distinct 3 dimensional structures, each characteristic of a given differentiated state. Autoantibodies to 2 types of DNA binding protein complexes, the nuclear lamina and p70/p80 (Ku), were identified in sera of patients with collagen vascular diseases. The intranuclear distribution, DNA binding, and behavior during mitosis of these antigens were examined using autoimmune sera and murine monoclonal antibodies. In vivo, the antigens have different intranuclear distributions and solubility characteristics. However, both antigens appear to reversibly bind to DNA during interphase and to rapidly dissociate from DNA during mitosis. Although the binding affinity of p70/p80 to DNA is heterogeneous, the interaction between p70/p80 and DNA in vitro is stable over 2 h or more. The rapid dissociation of p70/p80 from DNA during mitosis may therefore be mediated by a modification in either chromatin structure or in the p70/p80 antigen itself. Other proteins that reversibly interact with DNA, such as the lamins and nuclear pores, may have a role in the organization of DNA into transcribable euchromatin and nontranscribable heterochromatin. Autoantibodies to these proteins, and possibly those reactive with p70/p80, or other DNA binding proteins may be useful probes for studying both chromatin organization and the causes of autoimmune diseases such as systemic lupus erythematosus.
TL;DR: Chromomycin A3 banding of the chromosomes of three species of Cervidae allows the demonstration of both centromeric constitutive heterochromatin and R-banding patterns useful for identifying all the chromosome of a given karyotype.
Abstract: Chromomycin A3 banding of the chromosomes of three species of Cervidae (red deer, fallow deer, roe deer) allows the demonstration of both centromeric constitutive heterochromatin and R-banding patterns useful for identifying all the chromosomes of a given karyotype. In all three species significant amounts of chromomycin-bright heterochromatin are present at the centromeres of all autosomes. The X chromosomes of all investigated species contained appreciable amounts of centromeric heterochromatin. AgNO3 staining was applied sequentially to detect the location of active nucleolus organizer regions (NORs). The distribution of NORs was reasonably conservative in the investigated species.