Mithramycin and DIPI: a pair of fluorochromes specific for GC-and AT-rich DNA respectively

Egr-1 mediates low-dose arecoline induced human oral mucosa fibroblast proliferation via transactivation of Wnt5a expression

Background

Arecoline is an alkaloid natural product found in the areca nut that can induce oral submucous fibrosis and subsequent development of cancer. However, numerous studies have shown that arecoline may inhibit fibroblast proliferation and prevent collagen synthesis.

Results

High doses of arecoline (> 32 μg/ml) could inhibit human oral fibroblast proliferation, while low doses of arecoline (< 16 μg/ml) could promote the proliferation of human oral fibroblasts. Wnt5a was found to be both sufficient and necessary for the promotion of fibroblast proliferation. Egr-1 could mediate the expression of Wnt5a in fibroblasts, while NF-κB, FOXO1, Smad2, and Smad3 did not. Treatment with siRNAs specific to Egr-1, Egr inhibitors, or Wnt5a antibody treatment could all inhibit arecoline-induced Wnt5a upregulation and fibroblast proliferation.

Conclusions

Egr-1 mediates the effect of low dose arecoline treatment on human oral mucosa fibroblast proliferation by transactivating the expression of Wnt5a. Therefore, Egr inhibitors and Wnt5a antibodies are potential therapies for treatment of oral submucosal fibrosis and oral cancer.

A combined banding method that allows the reliable identification of chromosomes as well as differentiation of AT- and GC-rich heterochromatin

Сonstitutive heterochromatin areas are revealed by differential staining as C-positive chromosomal regions. These C-positive bands may greatly vary by location, size, and nucleotide composition. CBG-banding is the most commonly used method to detect structural heterochromatin in animals. The difficulty in identification of individual chromosomes represents an unresolved problem of this method as the body of the chromosome is stained uniformly and does not have banding pattern beyond C-bands. Here, we present the method that we called CDAG for sequential heterochromatin staining after differential GTG-banding. The method uses G-banding followed by heat denaturation in the presence of formamide with consecutive fluorochrome staining. The new technique is valid for the concurrent revealing of heterochromatin position due to differential banding of chromosomes and heterochromatin composition (AT-/GC-rich) in animal karyotyping.

Egr-1 transactivates WNT5A gene expression to inhibit glucose-induced β-cell proliferation

Selective β-cell loss is a characteristic of type 2 diabetes mellitus (T2DM). Inhibition of glucose-stimulated β-cell proliferation is one of the in vivo results of the lipotoxicity of saturated fatty acids (SFAs). However, the mechanism by which lipotoxicity inhibits β-cell proliferation is still unclear. In this study, we found palmitate, a saturated fatty acid, inhibited the β-cell proliferation induced by high glucose through the induction of Wnt5a expression in vitro and in vivo. We also found that Wnt5a was both sufficient and necessary for inhibition of β-cell proliferation. Additionally, Egr-1, but not NF-κB, FOXO1, Smad2, Smad3, SP1 or SP3 mediated the expression of Wnt5a. Deletion and site-directed mutagenesis of the WNT5A promoter revealed that activation of WNT5A gene transcription depends primarily on a putative Egr-binding sequence between nucleotides -52 to -44, upstream of the transcription start site. Furthermore, Egr-1 bound directly to this sequence in response to palmitate treatment, both in vitro and in vivo. Moreover, after mice islets were treated with Egr inhibitors, the expression of Wnt5a decreased significantly and the glucose-induced β-cell proliferation inhibited by palmitate was resumed. These findings establish Wnt5a as an Egr-1 target gene in β-cells, uncovering a novel Egr-1/Wnt5a pathway by which saturated free fatty acids block glucose-induced β-cell proliferation. Our study lends support for the potential of Egr-1 inhibitors or Wnt5a antibodies as therapeutics for the treatment of T2DM.

Reprogramming of fibroblast nuclei in cloned bovine embryos involves major structural remodeling with both striking similarities and differences to nuclear phenotypes of in vitro fertilized embryos

Nuclear landscapes were studied during preimplantation development of bovine embryos, generated either by in vitro fertilization (IVF), or generated as cloned embryos by somatic cell nuclear transfer (SCNT) of bovine fetal fibroblasts, using 3-dimensional confocal laser scanning microscopy (3D-CLSM) and structured illumination microscopy (3D-SIM). Nuclear landscapes of IVF and SCNT embryonic nuclei were compared with each other and with fibroblast nuclei. We demonstrate that reprogramming of fibroblast nuclei in cloned embryos requires changes of their landscapes similar to nuclei of IVF embryos. On the way toward the 8-cell stage, where major genome activation occurs, a major lacuna, enriched with splicing factors, was formed in the nuclear interior and chromosome territories (CTs) were shifted toward the nuclear periphery. During further development the major lacuna disappeared and CTs were redistributed throughout the nuclear interior forming a contiguous higher order chromatin network. At all stages of development CTs of IVF and SCNT embryonic nuclei were built up from chromatin domain clusters (CDCs) pervaded by interchromatin compartment (IC) channels. Quantitative analyses revealed a highly significant enrichment of RNA polymerase II and H3K4me3, a marker for transcriptionally competent chromatin, at the periphery of CDCs. In contrast, H3K9me3, a marker for silent chromatin, was enriched in the more compacted interior of CDCs. Despite these striking similarities, we also detected major differences between nuclear landscapes of IVF and cloned embryos. Possible implications of these differences for the developmental potential of cloned animals remain to be investigated. We present a model, which integrates generally applicable structural and functional features of the nuclear landscape.

Transcription factors Sp1 and Hif2α mediate induction of the copper-transporting ATPase (Atp7a) gene in intestinal epithelial cells during hypoxia

Genes with G/C-rich promoters were up-regulated in the duodenal epithelium of iron-deficient rats including those encoding iron (e.g. Dmt1 and Dcytb) and copper (e.g. Atp7a and Mt1) metabolism-related proteins. It was shown previously that an intestinal copper transporter (Atp7a) was co-regulated with iron transport-related genes by a hypoxia-inducible transcription factor, Hif2α. In the current study, we sought to test the role of Sp1 in transcriptional regulation of Atp7a expression during iron deprivation/hypoxia. Initial studies in IEC-6 cells showed that mithramycin, an Sp1 inhibitor, reduced expression of Atp7a and iron transport-related genes (Dmt1, Dcytb, and Fpn1) and blocked their induction by CoCl2, a hypoxia mimetic. Consistent with this, overexpression of Sp1 increased endogenous Atp7a mRNA and protein expression and stimulated Atp7a, Dmt1, and Dcytb promoter activity. Site-directed mutagenesis and functional analysis of a basal Atp7a promoter construct revealed four functional Sp1 binding sites that were necessary for Hif2α-mediated induction of promoter activity. Furthermore, chromatin immunoprecipitation (ChIP) assays confirmed that Sp1 specifically interacts with the Atp7a promoter in IEC-6 cells and in rat duodenal enterocytes. This investigation has thus revealed a novel aspect of Atp7a gene regulation in which Sp1 may be necessary for the HIF-mediated induction of gene transcription during iron deficiency/hypoxia. Understanding regulation of Atp7a expression may help further clarify the physiological role of copper in the maintenance of iron homeostasis. Furthermore, this Sp1/Hif2α regulatory mechanism may have broader implications for understanding the genetic response of the intestinal epithelium to maintain whole-body iron homeostasis during states of deficiency.

Imaging DNA with fluorochrome bearing metals

Molecules that fluoresce upon binding DNA are widely used in assaying and visualizing DNA in cells and tissues. However, using light to visualize DNA in animals is limited by the attenuation of light transmission by biological tissues. Moreover, it is now clear that DNA is an important mediator of dead cell clearance, coagulation reactions, and an immunogen in autoimmune lupus. Attaching metals (e.g., superparamagnetic nanoparticles, gadolinium ions, radioactive metal ions) to DNA-binding fluorochromes provides a way of imaging DNA in whole animals, and potentially humans, without light. Imaging metal-bearing, DNA-binding fluorochromes and their target DNA by magnetic resonance imaging may shed light on the many key roles of DNA in health and disease beyond the storage of genetic information.

Whole genome amplification in large neurons of the terrestrial slug Limax

The brain of gastropod mollusks contains giant neurons whose nuclei are enlarged with a large amount of genomic DNA. Such DNA is produced by repeated endoreplication. We have previously demonstrated that the frequency of the neuronal DNA endoreplication is correlative to the body growth of the adult land slug and to the increase in the amount of transcripts within the neuron. However, it has long been controversial whether the neuronal DNA endoreplication entails whole genome amplification (polyploidy), or whether only the necessary genomic loci are amplified (polyteny, polysomy, or cis-amplification by unequal recombination). In the present study, we adopted two modern techniques - quantitative genomic PCR and 5'-bromodeoxyuridine labeling - to distinguish between these two possibilities. Our results demonstrated that multiple genomic loci were amplified to the same extent irrespective of the transcriptional activities at these loci. Moreover, the visceral giant cell, the biggest neuron in the slug's brain, was estimated to contain approximately 10 000-times as much genomic DNA as the haploid amount. The 5'-bromodeoxyuridine-labeling experiments also revealed a uniform DNA synthesis within the nucleus. These results strongly support the idea that the giant neurons contain a polyploid genome rather than a locus-specific amplified genome.

Detailed interrogation of trypanosome cell biology via differential organelle staining and automated image analysis

BACKGROUND

Many trypanosomatid protozoa are important human or animal pathogens. The well defined morphology and precisely choreographed division of trypanosomatid cells makes morphological analysis a powerful tool for analyzing the effect of mutations, chemical insults and changes between lifecycle stages. High-throughput image analysis of micrographs has the potential to accelerate collection of quantitative morphological data. Trypanosomatid cells have two large DNA-containing organelles, the kinetoplast (mitochondrial DNA) and nucleus, which provide useful markers for morphometric analysis; however they need to be accurately identified and often lie in close proximity. This presents a technical challenge. Accurate identification and quantitation of the DNA content of these organelles is a central requirement of any automated analysis method.

RESULTS

We have developed a technique based on double staining of the DNA with a minor groove binding (4'', 6-diamidino-2-phenylindole (DAPI)) and a base pair intercalating (propidium iodide (PI) or SYBR green) fluorescent stain and color deconvolution. This allows the identification of kinetoplast and nuclear DNA in the micrograph based on whether the organelle has DNA with a more A-T or G-C rich composition. Following unambiguous identification of the kinetoplasts and nuclei the resulting images are amenable to quantitative automated analysis of kinetoplast and nucleus number and DNA content. On this foundation we have developed a demonstrative analysis tool capable of measuring kinetoplast and nucleus DNA content, size and position and cell body shape, length and width automatically.

CONCLUSIONS

Our approach to DNA staining and automated quantitative analysis of trypanosomatid morphology accelerated analysis of trypanosomatid protozoa. We have validated this approach using Leishmania mexicana, Crithidia fasciculata and wild-type and mutant Trypanosoma brucei. Automated analysis of T. brucei morphology was of comparable quality to manual analysis while being faster and less susceptible to experimentalist bias. The complete data set from each cell and all analysis parameters used can be recorded ensuring repeatability and allowing complete data archiving and reanalysis.

Ring-like distribution of constitutive heterochromatin in bovine senescent cells

Background

Cells that reach “Hayflick limit” of proliferation, known as senescent cells, possess a particular type of nuclear architecture. Human senescent cells are characterized by the presence of highly condensed senescent associated heterochromatin foci (SAHF) that can be detected both by immunostaining for histone H3 three-methylated at lysine 9 (H3K9me3) and by DAPI counterstaining.

Methods

We have studied nuclear architecture in bovine senescent cells using a combination of immunofluorescence and 3D fluorescent in-situ hybridization (FISH).

Results

Analysis of heterochromatin distribution in bovine senescent cells using fluorescent in situ hybridization for pericentric chromosomal regions, immunostaining of H3K9me3, centromeric proteins CENP A/B and DNA methylation showed a lower level of heterochromatin condensation as compared to young cells. No SAHF foci were observed. Instead, we observed fibrous ring-like or ribbon-like heterochromatin patterns that were undetectable with DAPI counterstaining. These heterochromatin fibers were associated with nucleoli.

Conclusions

Constitutive heterochromatin in bovine senescent cells is organized in ring-like structures.

DNA binding sites target nuclear NFATc1 to heterochromatin regions in adult skeletal muscle fibers

We have previously demonstrated that Ca²+/calcineurin-dependent dephosphorylation of the transcription factor nuclear factor of activated T cells subtype 1 (NFATc1) during repetitive skeletal muscle activity causes NFAT nuclear translocation and concentration in subnuclear NFAT foci. We now show that NFAT nuclear foci colocalize with heterochromatin regions of intense staining by DAPI or TO-PRO-3 that are present in the nucleus prior to NFATc1 nuclear entry. Nuclear NFATc1 also colocalizes with the heterochromatin markers trimethyl-histone H3 (Lys9) and heterochromatin protein 1α. Mutation of the NFATc1 DNA binding sites prevents entry and localization of NFATc1 in heterochromatin regions. However, fluorescence in situ hybridization shows that the NFAT-regulated genes for slow and fast myosin heavy chains are not localized within the heterochromatin regions. Fluorescence recovery after photobleaching shows that within a given nucleus, NFATc1 redistributes relatively rapidly (t(¹/₂) < 1 min) between NFAT foci. Nuclear export of an NFATc1 mutant not concentrated in NFAT foci is accelerated following nuclear entry during fiber activity, indicating buffering of free nuclear NFATc1 by NFATc1 within the NFAT foci. Taken together, our results suggest that NFAT foci serve as nuclear storage sites for NFATc1, allowing it to rapidly mobilize to other nuclear regions as required.

An intriguing Y chromosome in Heteromys anomalus (Rodentia, Heteromyidae)

The mitotic chromosomes of the pocket mouse Heteromys anomalus (Rodentia, Heteromyidae) from Venezuela were analyzed by means of conventional staining and various banding techniques. The karyotype of this species is distinguished by a Y chromosome with exceptional banding properties. The very large heterochromatic Y long arm shows a remarkable bright quinacrine fluorescence, but only moderate or dull fluorescence when labeled with other AT base pair-specific fluorochromes. The implications of these findings are discussed.

Structure-specific DNA-binding proteins as the foundation for three-dimensional chromatin organization

Any functions of tandem repetitive sequences need proteins that specifically bind to them. Telomere-binding TRF2/MTBP attaches telomeres to the nuclear envelope in interphase due to its rod-domain-like motif. Interphase nuclei organized as a number of sponge-like ruffly round chromosome territories that could be rotated from outside. SAF-A/hnRNP-U and p68-helicase are proteins suitable to do that. Their location in the interchromosome territory space, ATPase domains, and the ability to be bound by satellite DNAs (satDNA) make them part of the wires used to help chromosome territory rotates. In case of active transcription p68-helicase can be involved in the formation of local "gene expression matrices" and due to its satDNA-binding specificity cause the rearrangement of the local chromosome territory. The marks of chromatin rearrangement, which have to be heritable, could be provided by SAF-A/hnRNP-U. During telophase unfolding the proper chromatin arrangement is restored according to these marks. The structural specificity of both proteins to the satDNAs provides a regulative but relatively stable mode of binding. The structural specificity of protein binding could help to find the "magic" centromeric sequence. With future investigations of proteins with the structural specificity of binding during early embryogenesis, when heterochromatin formation goes on, the molecular mechanisms of the "gene gating" hypothesis (Blobel, 1985) will be confirmed.

Specific interaction of mouse major satellite with MAR-binding protein SAF-A

A DNA-binding activity specific to the major mouse satellite (satMa) has been detected in a nuclear matrix protein extract by electrophoretic mobility shift assays (EMSA) after fractionation by ion exchange chromatography. An antibody raised against the satMa-protein complexes recovered from preparative EMSA recognizes on Western blots one major polypeptide with an apparent molecular mass of 120 kDa. The protein also has a similar affinity for a matrix-associated region (MAR) fragment. We demonstrate that the protein is a murine homologue of SAF-A which has been shown to bind selectively to MARs and is responsible for the satMa-binding activity in the chromatographic fractions. SatMa has significant homology to the mouse minor satellite fragments, but its binding of SAF-A shows much less affinity. No protected regions of significant length were found by footprinting, but multiple T residues scattered within the satMa sequence are protected, indicating that the whole fragment is involved in the binding to SAF-A. Combined immunofluorescence (SAF-A) and FISH (satMa) with in situ nuclear matrix procedures reveal that SAF-A and satMa colocalize. SAF-A appears as bright dots in interphase nuclei, presumably associated with MARs, predominantly surrounding and covering heterochromatic areas. A scheme based on morphological observations and biochemical data of SAF-A double satMa/MAR specificity is discussed.

Characterization of the selective staining of DNA on gels using two fluorochromes

Ethidium bromide (EB) and 4'-6-diamidino-2-phenylindole (DAPI) are both well-known fluorochromes for detecting DNA fragments. EB binds to DNA by intercalation and DAPI binds in the DNA minor groove. We previously developed a staining method using both EB and DAPI that is selective for AT-rich DNA fragments. Using this double-staining method, AT-rich DNA fragments are visualized as bluish-white fluorescent bands. To further characterize this method, a series of synthetic DNA fragments were designed with systematic variations in the length, AT content, and DNA sequence pattern. The staining properties of these fragments were determined in the presence of DAPI and EB, and the following results were obtained. (i) In a series of fragments with three AT base pairs followed by one GC base pair, the stained DNA fragments exhibited different fluorescent colors and varied from bluish (more DAPI staining) to pinkish (less DAPI staining) in the order 5'-AAA-3', 5'-AAT-3', 5'-ATA-3', 5'-TTA-3'. (ii) In fragments with constant AT content, the blue fluorescent color increased with increasing number of A (or T) nucleotides, due to increased DAPI binding. The blue color was saturated when the number of A (or T) nucleotides was 12 or greater. (iii) The fluorescent color of the stained DNA fragments changed in the order of red-orange, pink, pinkish-white, white, bluish-white, blue as the AT content increased from 0 to 100%. Thus, the fluorescent color of DNA fragments stained with DAPI and EB depends on base composition and nucleotide sequence, suggesting that individual stained DNA fragments may have characteristic and specific fluorescent colors. The fluorescent color emitted by specific stained DNA fragments in the presence of EB and DAPI can be analyzed with a high degree of sensitivity and resolution using the XYZ colorimetric system.

DAPI: a DNA-specific fluorescent probe

DAPI (4',6-diamidino-2-phenylindole) is a DNA-specific probe which forms a fluorescent complex by attaching in the minor grove of A-T rich sequences of DNA. It also forms nonfluorescent intercalative complexes with double-stranded nucleic acids. The physicochemical properties of the dye and its complexes with nucleic acids and history of the development of this dye as a biological stain are described. The application of DAPI as a DNA-specific probe for flow cytometry, chromosome staining, DNA visualization and quantitation in histochemistry and biochemistry is reviewed. The mechanisms of DAPI-nucleic acid complex formation including minor groove binding, intercalation and condensation are discussed.

Chromosome banding in Amphibia. XII. Restriction endonuclease banding

Fixed metaphase chromosomes of several species of Amphibia were treated with various restriction endonucleases and subsequently stained with Giemsa. Metaphases of man and chicken were examined in parallel under the same experimental conditions for comparison. The restriction enzymes always induce subsets of the C-banding patterns present in the amphibian karyotypes. The heterochromatic regions can be either resistant or sensitive to the restriction enzyme. The modified C-banding patterns revealed by different restriction endonucleases in the karyotype of the same species can be either extremely dissimilar or almost completely congruent. Correspondingly, the action of the same restriction enzyme on the karyotypes of different species may vary greatly. There is only rarely a correlation between the type of C-banding patterns produced by different restriction endonucleases and their specific base pair recognition sequences. In contrast to mammalian and avian chromosomes, restriction enzymes induce no multiple G-banding patterns in amphibian chromosomes. This is attributed to the difference in organization of the DNA in the genomes of poikilothermic vertebrates. The possible mechanisms of restriction endonuclease banding and the various uses of this technique for amphibian chromosomes are discussed.

Chromosome banding in amphibia. XI. Constitutive heterochromatin, nucleolus organizers, 18S + 28S and 5S ribosomal RNA genes in Ascaphidae, Pipidae, Discoglossidae and Pelobatidae

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.

Detecting abnormal human chromosome constitutions by dual laser flow cytogenetics

Our custom dual laser chromosome sorter has been used to characterize and isolate metaphase human chromosomes rapidly for gene mapping purposes. Herein, we tested how well this system could detect unknown abnormal human chromosome constitutions. These results were compared to those of conventional cytogenetic analyses by banding and photomicrography. The sorter was used to analyze each cell line stained with two different stain pairs: DIPI-chromomycin and Hoechst-chromomycin. In 20 min, two histograms representing 2 X 10(5) chromosomes each were collected for each stain pair. A blind study of 11 samples by flow analysis demonstrated excellent concordance between the abnormal chromosomes detected and the diagnoses of Giemsa-banded karyotypes. Aneuploidy was identified by changes in the number of chromosomes in each histogram peak, while rearrangements such as deletions and translocations caused shifts in the histogram peak positions. The direction and distance of histogram peak shifts are directly related to alterations in chromosome size and banding pattern. We conclude that dual-laser flow analysis may provide a rapid approach to the screening and diagnosis of chromosome abnormalities.

Intensity heteromorphisms of human chromosome 15p by DA/DAPI technique

We suggest that the short arms of human chromosome 15 (15p) exhibit intensity heteromorphisms by DA/DAPI technique. A method for classification of variable intensities is proposed. The different intensities can be classified into at least five classes. They are: negative, pale, medium, intense, and brilliant. Therefore we suggest that 15p is not always positive by DA/DAPI technique. The present findings reveal that the heteromorphism on 15p is far greater than previously thought.

Site-specific carcinogen binding to DNA in polytene chromosomes

Treatment of Chironomus polytene chromosomes with the ultimate carcinogen benzo[a]pyrene diol epoxide I or in vivo administration of the parent hydrocarbon to larvae indicates that the carcinogen interacts with the genome in a nonrandom manner. Visualization of the carcinogen-DNA binding sites by immunofluorescence reveals that, in vivo, some sites are preferentially modified. The combined effects of DNA sequence, chromatin structure, and gene localization may lead to selective targeting of carcinogens to specific genomic regions. In polytene chromosomes the targeting effect is amplified, thereby making these chromosomes a uniquely suitable system for visualizing and studying site-specific interactions of carcinogens with the genome.

Spot-blot analysis of sorted chromosomes assigns a fructose intolerance disease locus to chromosome 9

The aldolase B gene was mapped to chromosome 9 using a rapid gene mapping system. This system uses a dual-laser sorter to identify and separate metaphase human chromosomes stained with either DIPI-chromomycin or Hoechst-chromomycin. Chromosome panels were constructed from a normal cell line by sorting 22 chromosome fractions directly onto nitrocellulose filters. Twelve labeled gene probes hybridized to the sorted chromosomal DNA fractions predicted by previous chromosome assignments. Eighteen newly cloned genes have been mapped using the same protocol.

Chromosomal R-banding with a monoclonal antidouble-stranded DNA antibody

A monoclonal anti-DNA antibody (HB2) specific for poly dG- poly dC nucleotides was used to stain metaphasic lymphocyte or amniotic cell human chromosomes. HB2 fixation was revealed using either a peroxidase- or a rhodamine-labeled anti-mouse immunoglobulin antiserum. The staining pattern of the chromosomes was dependent on the HB2 concentration: R-banding could be observed at high antibody dilution. Previous trypsinization of metaphasic preparations demonstrated a precise and reproducible typical R-banding independent of the HB2 concentration. This technique appears to be an interesting alternative to other R-banding procedures. The specificity of the antibody allows a better understanding of the biochemical mechanism of R-banding.

Application of 7-amino-actinomycin D for the fluorescence microscopical analysis of DNA in cells and polytene chromosomes

The cytochemical properties of a guanine-specific synthetic fluorescent analogue of actinomycin D, 7-amino-actinomycin D, have been studied in fixed and living preparations of L cells and polytene chromosomes of salivary glands of Chironomus thummi thummi and Drosophila lummei (Hackman). 7-Amino-actinomycin D has been shown to bind to DNA-containing structures, thereby inducing in them a bright red fluorescence. No specific fluorescence has been found in RNA-containing structures treated with this fluorescent probe. The fluorescence pattern of some regions of polytene chromosomes with a known nucleotide composition was analysed. It has been established that 7-amino-actinomycin D induces a very weak fluorescence in GC-poor chromosome regions of the Drosophila lummei toromere structure. Data indicating a nonlinear dependence between the fluorescence intensity of a stained chromosome region and the GC content in its DNA have been obtained. The influence of DNA nucleotide composition in a chromosome region on the fluorescence of 7-amino-actinomycin D is discussed. In combination with quinacrine staining and the Feulgen fluorescence reaction, treatment with 7-amino-actinomycin D provides useful information about the distribution of GC base pairs in the chromosome region under study.

Chromosome banding in Amphibia. IX. The polyploid karyotypes of Odontophrynus americanus and Ceratophrys ornata (Anura, Leptodactylidae)

The somatic and meiotic chromosomes of the South American leptodactylid toads Odontophrynus americanus, Ceratophyrys ornata, and C. cranwelli were analysed both with conventional staining and differential banding techniques. The karyotypes of O. americanus were tetraploid; those of C. ornata octaploid. Ceratophrys cranwelli is a diploid species whose karyotype displays great similarities with that of C. ornata. The high frequency of multivalent pairing configurations in the meioses of O. americanus and C. ornata indicate that these animals were of autopolyploid origin. The conventionally stained somatic chromosomes of O. americanus can be arranged into sets of four similar chromosomes (quartets); those of C. ornata, into sets of eight similar chromosomes (octets). The banding patterns revealed heterogeneity within some quartets of O. americanus, dividing each of them into two pairs of homologous chromosomes. In analogy, some octets of C. ornata can be subdivided into two quartets of chromosomes with homologous bands. These structural heterogeneities within the quartets and octets are interpreted as a "diploidization" of the polyploid karyotypes. Diploidization leads to genomes that are polyploid with respect to the amount of genetic material and diploid with respect to chromosomal characteristics and the level of gene expression. In tetraploid O. americanus, the number of nucleolus organizer regions (NORs) and their DNA content is proportional to the degree of ploidy. In contrast, up to eight NORs have been deleted in the octoploid C. ornata. These NOR losses are discussed as a possible reason for the reduction of genetic activity in polyploid genomes.

Chromosome banding in Amphibia. VIII. An unusual XY/XX-sex chromosome system in Gastrotheca riobambae (Anura, Hylidae)

The mitotic and meiotic chromosomes of the marsupial frog Gastrotheca riobambae were analysed with various banding techniques. The karyotype of this species is distinguished by considerable amounts of constitutive heterochromatin and unusual, heteromorphic XY sex chromosomes. The Y chromosome is considerably larger than the X chromosome and almost completely heterochromatic. The analysis of the banding patterns obtained with GC- and AT-base-pair-specific fluorochromes shows that the constitutive heterochromatin in the Y chromosome consists of at least three different structural categories. The only nucleolus organizer region (NOR) of the karyotype is localized in the short arm of the X chromosome. This causes a sex-specific difference in the number of NOR: female animals have two NORs in diploid cells, male animals one. No cytological indications were found for the inactivation of one of the two X chromosomes in the female cells. In male meiosis, the heteromorphic sex chromosomes form a characteristic sex-bivalent by pairing their telomeres in an end-to-end arrangement. The significance of the XY/XX sex chromosomes of G. riobambae for the study of X-linked genes in Amphibia, the evolution of sex chromosomes and their specific DNA sequences, and the significance of the meiotic process of sex chromosomes are discussed.

G-band-like structures and centromeric asymmetry in the BrdU containing mouse chromosomes

Mouse cell cultured in the presence of BrdU or BrdC for one replication cycle were stained in a 4Na-EDTA Giemsa solution which stains BrdU-containing chromatin preferentially (Takayama and Tachibana, 1980). With this treatment clear bands (B-bands) were revealed along the length of the chromosomes. The B-banding patterns were identical with the G-banding patterns of this species except for the centromeric region in which lateral asymmetry of Giemsa staining was seen. The concomitant occurrence of the lateral asymmetry with the B-banding supports the assumption that the B-bands visualized by the present technique reflect the BrdU-rich chromatin regions differentially localized along the chromosomes. Most of the chromosomes constituting the mouse karyotype showed their own characteristics appearance of the asymmetry, but in some of them the asymmetry was not clear and the Y did not show any specific, centromeric staining. The marked coincidence of the B- and G-banding patterns seems to provide evidence of the involvement of AT-rich chromatin in the induction of positive G-bands. The present technique also seems quite useful to analyze chromosomes of some species in which ordinary G-banding techniques have been known to bring about only unsatisfactory results.

Investigations of fading of immunofluorescence objects

Fading of immunofluorescent objects was influenced by attenuation of fluorescence intensity whether by attenuation of excitation, post-fixation or counterstaining. In comparison with the wide-band excitation, narrow-band excitation had an influence on the fading rate via the attenuation of the excitation intensity only. Compared with aqueously immersed objects we obtained only half of the intensity and a quite stronger decrease of fluorescence with dry objects or objects embedded with fast-hardening medium. Addition of thiosulphate to embedding medium had no effect on fading. In opposite literature we found in our immunofluorescence specimen after addition of dithionite an extremely increased fading rate.

On the structure and polymorphism of the human chromosome no. 15

Chromosome preparations from 67 randomly selected healthy individuals were consecutively stained with silver, mithramycin, pentamidine-DAPI, and quinacrine mustard. In the short arm of the chromosome 15 up to six regions, which were highly polymorphic, apparently independently of each other, could be detected by the given methods. The frequency of occurrence of each individual polymorphic feature in the population investigated ranges from 70% to 87%. They appear randomly and independently of each other.

A synopsis of the human Y chromosome

Phenotypic features and functions known to depend on the presence of the Y chromosome or the H-Y antigen are discussed in relation to structural anomalies of the Y chromosome and other abnormalities of sexual and somatic development. Recent knowledge about molecular organization of constitutive heterochromatin in relation to the human Y is presented. An attempt is made at assigning different functions, genes and DNA sequences to different regions of the Y chromosome.

The organization of DNA in the mitotic and polytene chromosomes of Sciara corprophila

The organization of DNA in the mitotic metaphase and polytene chromosomes of the fungus gnat, Sciara coprophila, has been studied using base-specific DNA ligands, including anti-nucleoside antibodies. The DNA of metaphase and polytene chromosomes reacts with AT-specific probes (quinacrine, DAPI, Hoechst 33258 and anti-adenosine) and to a somewhat lesser extent with GC-specific probes (mithramycin, chromomycin A3 and anti-cytidine). In virtually every band of the polytene chromosomes chromomycin A3 fluorescence is almost totally quenched by counterstaining with the AT-specific ligand methyl green. This indicates that GC base pairs in most bands are closely interspersed with AT base pairs. The only exceptions are band IV-8A3 and the nucleolus organizer on the X. In contrast, quinacrine and DAPI fluorescence in every band is only slightly quenched by counterstaining with the GC-specific ligand actinomycin D. Thus, each band contains a moderate proportion of AT-rich DNA sequences with few interspersed GC base pairs. - The C-bands in mitotic and polytene chromosomes can be visualized by Giemsa staining after differential extraction of DNA and those in polytene chromosomes by the use of base-specific fluorochromes or antibodies without prior extraction of DNA. C-bands are located in the centromeric region of every chromosome, and the telomeric region of some. The C-bands in the polytene chromosomes contain AT-rich DNA sequences without closely interspered GC base pairs and lack relatively GC-rich sequences. However, one C-band in the centromeric region of chromosome IV contains relatively GC-rich sequences with closely interspersed AT base pairs. - C-bands make up less than 1% of polytene chromosomes compared to nearly 20% of mitotic metaphase chromosomes. The C-bands in polytene chromosomes are detectable with AT-specific or GC-specific probes while those in metaphase chromosomes are not. Thus, during polytenization there is selective replication of highly At-rich and relatively GC-rich sequences and underreplication of the remainder of the DNA sequences in the constitutive heterochromatin.

Specific fluorescent bands on chromosomes produced by acridine orange after prestaining with base specific non-fluorescent DNA ligands

Metaphase chromosomes stained with acridine orange exhibit uniform yellow-green fluorescence. Chromosome preparations treated with the non-fluorescent A-T specific antibiotic distamycinA prior to acridine orange staining exhibit longitudinal fluorescent banding patterns similar to those produced by a number of fluorescent R-band techniques. Similarly, chromosome preparations treated with the non-fluorescent G-C specific antibiotic actinomycin D followed by acridine orange staining exhibit "Hoechst-type" banding patterns. Interactions of various ligand-DNA combinations in solution indicate that the base pair specific antibiotics induce banding patterns by selectively altering acridine orange binding sites in chromosomal regions rich in the particular base pair for which the antibiotic exhibits specificity.

Energy transfer and binding competition between dyes used to enhance staining differentiation in metaphase chromosomes

The ability of electronic energy transfer and direct binding competition between pairs of dyes to enhance contrast in human or bovine metaphase chromosome staining patterns is illustrated, and the relative effectiveness of these two mechanism compared. The existence of energy transfer between quinacrine or 33258 Hoechst and 7-amino-actinomycin D in doubly stained chromosomes is demonstrated directly by microfluorometry. The ability of the dyes 7-amino-actinomycin D, methyl green, or netropsin, acting as counterstains, to displace quinacrine, 33258 Hoechst, or chromomycin A3 from chromosomes, is estimated by quantitative analysis of energy transfer data, by photobleaching of the counterstains, or by selective removal of counterstains by appropriate synthetic polynucleotides. Effects on the fluorescence of soluble 33258 Hoechst-DNA complexes due to energy transfer or binding displacement, by actinomycin D or netropsin, respectively, are further differentiated by nanosecond fluorescence decay measurements. Examples are presented of dye combinations for which (a) energy transfer is the primary mechanism operative, (b) binding competition exists, with consequences reinforcing those due to energy transfer, or (c) binding competition is the most important interaction. These analyses of mechanisms responsible for contrast enhancement in doubly stained chromosomes are used to derive information about the relationship between chromosome composition and banding patterns.

Isolation, properties and cellular distribution of D1, a chromosomal protein of Drosophila

The protein D1 was obtained from nuclei of Drosophila melanogaster embryos and purified by perchloric acid fractionation and preparative gel electrophoresis. In nuclei its amount is approximately 1% of the amount of DNA by weight. D1 is soluble in 5% perchloric acid and extractable from nuclei by solutions of moderate ionic strength (0.35 M NaCl). Amino acid analysis shows that it is rich in both basic (20%) and acidic (27%) aminoacids. In all these properties D1 resembles HMG proteins (high mobility group; Johns et al., 1975) of vertebrates; however, its apparent molecular weight (approximately 50,000) is much higher. The distribution of D1 in salivary gland polytene chromosomes was investigated by immunofluorescence. Two levels of fluorescence intensity were observed: 1) Very bright fluorescence at chromosomal positions 81F, 83E, 101F, 102C and 102F; these sites are shown, by double labeling techniques, to coincide with quinacrine bright sites. 2) Medium to low fluorescence at many sites widely distributed throughout all chromosomes. In order to interpret these results and to relate them to the in vivo distribution of D1, we have investigated the pattern of immunofluorescence staining as a function of the methods of chromosome preparation and salivary gland fixation. The immunological specificity of the anti-D1 serum was studied by comparing its reactivity with D. melanogaster and D. virilis chromosome spreads and whole salivary glands, and by using reagents that minimize non-specific antibody interactions. We conclude that D1 is widely distributed throughout cytoplasm and nucleus, present in many chromomeres but most abundant in chromosomal sites that contain the AT-rich satellite DNA of density 1.672. This distribution, together with available evidence about the nucleotide sequences present in this satellite, suggests that D1 binds preferentially to chromatin containing sequences AATAT and/or AATATAT.

Chromosome banding in amphibia. IV. Differentiation of GC- and AT-rich chromosome regions in Anura

The chromosomes of 26 species of Anura from variously highly envolved groups were analysed with the fluorescent GC-specific antibiotics mithramycin and chromomycin A3 as well as with the AT-specific quinacrine. The mithramycin- and chromomycin A3-stainings generally resulted in a pattern of the constitutive heterochromatin opposite to the one obtained with quinacrine stain. The weaker a heterochromatic region fluoresces with quinacrine, the stronger is the intensity of the fluorescence achieved with mithramycin and chromomycin A3. Some of the telomeric and interstitial heterochromatic regions, however, exhibit no enhanced fluorescence with any of the fluorochromes. The nucleolar constrictions of the nucleolus organizer regions (NORs) displayed the brightest mithramycin- and chromomycin A3-fluorescence in the karyotypes and interphase nuclei of all species examined. The contrast of the brightly fluorescing GC-rich heterochromatin and of the NORs is considerably enhanced, when the non-fluorescent AT-specific oligopeptide distamycin A is employed as a counterstain. No banding patterns were observed with the fluorochromes in the euchromatic regions of the metaphase chromosomes; this attributed to the strong spiralization of the anuran chromosomes. A cytochemical classification of the various chromatin types in the anuran chromosomes is discussed on the basis of the differential labelings found on the constitutive heterochromatin by means of the fluorochromes.

Simultaneous production of Q and R bands after staining with chromomycin A3 or olivomycin

Human and mouse chromosomes, stained with either chromomycin A3 or olivomycin, which bind preferentially to G - C-rich DNA (where G is guanosine and C is cytosine), exhibit a Q or a reverse banding pattern, depending on the wavelength used for excitation. The two complementary banding patterns can be observed in the same metaphase simply by changing the combination of excitation filters. These data suggest, therefore, that in addition to base composition, other factors are involved in the production of chromosome banding by chromomycin A3 and olivomycin.