Methyl green is a substitute for distamycin A in the formation of distamycin A/DAPI C-bands

Karyotypic and Molecular Analysis of Pterygoplichthys pardalis (Castelnau 1855) from the Lower Amazon River

Pterygoplichthys pardalis is an armored catfish native to South America and an important resource for the ornamental fish industry. Recently, several exotic populations have been introduced into rivers on five continents. Despite its commercial and environmental importance, P. pardalis is poorly studied from a genetic perspective. In this study, we analyzed the karyotype of P. pardalis from the Amazon River and molecular variations in the mitochondrial gene Cytochrome oxidase I (COI) between native and exotic populations. The karyotype presented diploid number 2n = 52 and NF = 100 without cytogenetic variation between males and females. Nucleolus organizer regions (Ag-NOR) in the distal region of the long arm of pair 12 coincided with the 18S hybridization signal, whereas 5S was syntenic to this chromosome but localized in the short arm. The constitutive heterochromatin was restricted in the distal regions of pairs 4, 12, 25, and 26. Telomeric probes showed only distal hybridization signals. The karyotype of P. pardalis diverged from that of its congeners, and COI molecular variation revealed four haplotypes. The Philippine population revealed the greatest diversity with three haplotypes, while haplotype H1 was the most abundant and observed in both native and exotic populations. This new genetic data contributes to species management and provides useful information from an aquaculture perspective.

The ancestral chromosomes of Dromiciops gliroides (Microbiotheridae), and its bearings on the karyotypic evolution of American marsupials

Background

The low-numbered 14-chromosome karyotype of marsupials has falsified the fusion hypothesis claiming ancestrality from a 22-chromosome karyotype. Since the 14-chromosome condition of the relict Dromiciops gliroides is reminecent of ancestrality, its interstitial traces of past putative fusions and heterochromatin banding patterns were studied and added to available marsupials’ cytogenetic data. Fluorescent in situ hybridization (FISH) and self-genomic in situ hybridization (self-GISH) were used to detect telomeric and repetitive sequences, respectively. These were complemented with C-, fluorescent banding, and centromere immunodetection over mitotic spreads. The presence of interstitial telomeric sequences (ITS) and diploid numbers were reconstructed and mapped onto the marsupial phylogenetic tree.

Results

No interstitial, fluorescent signals, but clearly stained telomeric regions were detected by FISH and self-GISH. Heterochromatin distribution was sparse in the telomeric/subtelomeric regions of large submetacentric chromosomes. Large AT-rich blocks were detected in the long arm of four submetacentrics and CG-rich block in the telomeric regions of all chromosomes. The ancestral reconstructions both ITS presence and diploid numbers suggested that ITS are unrelated to fusion events.

Conclusion

Although the lack of interstitial signals in D. gliroides’ karyotype does not prove absence of past fusions, our data suggests its non-rearranged plesiomorphic condition.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-016-0270-8) contains supplementary material, which is available to authorized users.

Comparative cytogenetic study of three Macrolophus species (Heteroptera, Miridae)

Macrolophus pygmaeus (Rambur, 1839) (Insecta, Heteroptera, Miridae) is a predator of key vegetable crop pests applied as a biocontrol agent in the Mediterranean region. Macrolophus pygmaeus and Macrolophus melanotoma (A. Costa, 1853) are cryptic species with great morphological similarity which results in their misidentification and negative consequences for the conservation of their populations on greenhouse and outdoor crops. In order to find out specific markers for their separation we studied the karyotype, male meiosis and heterochromatin composition of these species and additionally of a third species (as a reference one), Macrolophus costalis Fieber, 1858. We demonstrate here that all the three species share achiasmate male meiosis and sex chromosome pre-reduction. On the other hand, the species differ in karyotype, with 2n=28 (26+XY) in Macrolophus pygmaeus, 2n=27 (24+X1X2Y) in Macrolophus costalis, and 2n=34 (32+XY) in Macrolophus melanotoma, and heterochromatin distribution and composition. In addition, the species differ in sperm morphology: sperm cells of Macrolophus costalis are significantly longer with longer head and tail than those of Macrolophus melanotoma and Macrolophus pygmaeus, whereas sperm cells of Macrolophus melanotoma have a longer tail than those of Macrolophus pygmaeus. All these characters can be used as markers to identify the species, in particular the cryptic species Macrolophus melanotoma and Macrolophus pygmaeus.

Zebrafish chromosome banding

Banding techniques were carried out on metaphase chromosomes of zebrafish (Danio rerio) embryos. The karyotypes with the longest chromosomes consist of 12 metacentrics, 26 submetacentrics, and 12 subtelocentrics (2n = 50). All centromeres are C-band positive. Eight chromosomes have a pericentric C-band in each arm and 22 chromosomes have one in the longest arm. Two chromosomes have a slightly heterochromatic long arm and five chromosomes have an Ag-NOR at the terminal end of the long arm. Other banding patterns and sex chromosomes could not be revealed.

Continuous occurrence of intra-individual chromosome rearrangements in the peach potato aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae)

Analysis of the holocentric mitotic chromosomes of the peach-potato aphid, Myzus persicae (Sulzer), from clones labelled 50, 51 and 70 revealed different chromosome numbers, ranging from 12 to 14, even within each embryo, in contrast to the standard karyotype of this species (2n = 12). Chromosome length measurements, combined with fluorescent in situ hybridization experiments, showed that the observed chromosomal mosaicisms are due to recurrent fragmentations of chromosomes X, 1 and 3. Contrary to what has generally been reported in the literature, X chromosomes were frequently involved in recurrent fragmentations, in particular at their telomeric ends opposite to the nucleolar organizer region. Supernumerary B chromosomes have been also observed in clones 50 and 51. The three aphid clones showed recurrent fissions of the same chromosomes in the same regions, thereby suggesting that the M. persicae genome has fragile sites that are at the basis of the observed changes in chromosome number. Experiments to induce males also revealed that M. persicae clones 50, 51 and 70 are obligately parthenogenetic, arguing that the reproduction by apomictic parthenogenesis favoured the stabilization and inheritance of the observed chromosomal fragments.

Comparative cytogenetic study on two species of the genus Entedon Dalman, 1820 (Hymenoptera, Eulophidae) using DNA-binding fluorochromes and molecular and immunofluorescent markers

Karyotypes of Entedon cionobius Thomson, 1878 and Entedon cioni Thomson, 1878 (Hymenoptera: Eulophidae) were studied using DNA-binding ligands with different base specificity (propidium iodide, chromomycin A3, methyl green and DAPI; all these ligands, except for the last one, were used for the first time in parasitic wasps), C-banding, fluorescence in situ hybridization (FISH) with a 45S rDNA probe and 5-methylcytosine immunodetection. Female karyotypes of both species contain five pairs of relatively large metacentric chromosomes and a pair of smaller acrocentric chromosomes (2n = 12). As in many other Hymenoptera, males of both Entedon Dalman, 1820 species have haploid chromosome sets (n = 6). Fluorochrome staining revealed chromosome-specific banding patterns that were similar between the different fluorochromes, except for the CMA3- and PI-positive and DAPI-negative band in the pericentromeric regions of the long arms of both acrocentric chromosomes. The obtained banding patterns were virtually identical in both species and allowed for the identification of each individual chromosome. C-banding revealed a pattern similar to DAPI staining, although centromeric and telomeric regions were stained more intensively using the former technique. FISH detected a single rDNA site in the same position on the acrocentric chromosomes as the bright CMA3-positive band. Immunodetection of 5-methylcytosine that was performed for the first time in the order Hymenoptera revealed 5-methylcytosine-rich sites in the telomeric, centromeric and certain interstitial regions of most of the chromosomes.

Karyotype analysis of four jewel-beetle species (Coleoptera, Buprestidae) detected by standard staining, C-banding, AgNOR-banding and CMA3/DAPI staining

The male karyotypes of Acmaeodera pilosellae persica Mannerheim, 1837 with 2n=20 (18+neoXY), Sphenoptera scovitzii Faldermann, 1835 (2n=38-46), Dicerca aenea validiuscula Semenov, 1895 - 2n=20 (18+Xyp) and Sphaerobothris aghababiani Volkovitsh et Kalashian, 1998 - 2n=16 (14+Xyp) were studied using conventional staining and different chromosome banding techniques: C-banding, AgNOR-banding, as well as fluorochrome Chromomycin A3 (CMA3) and DAPI. It is shown that C-positive segments are weakly visible in all four species which indicates a small amount of constitutive heterochromatin (CH). There were no signals after DAPI staining and some positive signals were discovered using CMA3 staining demonstrating absence of AT-rich DNA and presence of GC-rich clusters of CH. Nucleolus organizing regions (NORs) were revealed using Ag-NOR technique; argentophilic material mostly coincides with positive signals obtained using CMA3 staining.

Composition and epigenetic markers of heterochromatin in the aphid Aphis nerii (Hemiptera: Aphididae)

A detailed karyotype analysis of the oleander aphid Aphis nerii focusing on the distribution, molecular composition and epigenetic modifications of heterochromatin was done in order to better understand the structure and evolution of holocentric/holokinetic chromosomes in aphids. The female karyotype (2n = 8) consisted of 3 pairs of autosomes and a pair of X chromosomes that were the longest elements in the karyotype and carried a single, terminally located nucleolar organizer region. Males showed 2n = 7 chromosomes due to the presence of a single X chromosome. Heterochromatin was located in the X chromosomes only and consisted of 4 satellite DNAs that have been identified. A. nerii constitutive heterochromatin was enriched in mono-, di- and tri-methylated H3 histones and HP1 proteins but, interestingly, it lacked DNA methylation that was widespread in euchromatic chromosomal regions. These results suggest that aphid heterochromatin is assembled and condensed without any involvement of DNA methylation.

Karyotypes, male meiosis and comparative FISH mapping of 18S ribosomal DNA and telomeric (TTAGG) n repeat in eight species of true bugs (Hemiptera, Heteroptera)

Eight species belonging to five true bug families were analyzed using DAPI/CMA3-staining and fluorescence in situ hybridization (FISH) with telomeric (TTAGG)n and 18S rDNA probes. Standard chromosomal complements are reported for the first time for Deraeocoris rutilus (Herrich-Schäffer, 1838) (2n=30+2m+XY) and Deraeocoris ruber(Linnaeus, 1758) (2n=30+2m+XY) from the family Miridae. Using FISH, the location of a 18S rDNA cluster was detected in these species and in five more species: Megaloceroea recticornis (Geoffroy, 1785) (2n=30+XY) from the Miridae; Oxycarenus lavaterae (Fabricius, 1787) (2n=14+2m+XY) from the Lygaeidae s.l.; Pyrrhocoris apterus (Linnaeus, 1758) (2n=22+X) from the Pyrrhocoridae; Eurydema oleracea (Linnaeus, 1758) (2n=12+XY) and Graphosoma lineatum (Linnaeus, 1758) (2n=12+XY) from the Pentatomidae. The species were found to differ with respect to location of a 18S rRNA gene cluster which resides on autosomes in Oxycarenus lavaterae and Pyrrhocoris apterus, whereas it locates on sex chromosomes in other five species. The 18S rDNA location provides the first physical landmark of the genomes of the species studied. The insect consensus telomeric pentanucleotide (TTAGG)n was demonstrated to be absent in all the species studied in this respect, Deraeocoris rutilus, Megaloceroea recticornis, Cimex lectularius Linnaeus, 1758 (Cimicidae), Eurydema oleracea, and Graphosoma lineatum, supporting the hypothesis that this motif was lost in early evolution of the Heteroptera and secondarily replaced with another motif (yet unknown) or the alternative telomerase-independent mechanisms of telomere maintenance. Dot-blot hybridization analysis of the genomic DNA from Cimex lectularius, Nabis sp. and Oxycarenus lavaterae with (TTAGG)n and six other telomeric probes likewise provided a negative result.

Cytogenetic and molecular analysis of the holocentric chromosomes of the potato aphid Macrosiphum euphorbiae (Thomas, 1878)

Cytogenetic and molecular investigations on the holocentric chromosomes of the aphid Macrosiphum euphorbiae (Thomas, 1878)have been carried out using silver staining and C-banding (followed by chromomycin A3 and DAPI staining) in order to improve our knowledge about the structure of aphid chromosomes. The C-banding pattern is peculiar since only the two X chromosomes and a single pair of autosomes presented heterochromatic bands. Silver staining and FISH with the 28S rDNA probe localized the rDNA genes on one telomere of each X chromosome that were also brightly fluorescent after chromomycin A3 staining of C-banded chromosomes, whereas all other heterochromatic bands were DAPI positive. Interestingly, a remarkable nucleolar organizing region (NOR) heteromorphism was present making the two X chromosomes easily distinguishable. Southern blotting and FISH assessed the presence of the (TTAGG)n repeat at the ends of all the Macrosiphum euphorbiae chromosomes. Karyotype analysis showed that all males possessed the X chromosome with the larger amount of rDNA suggesting a non-Mendelian inheritance of the two X chromosomes.

Analysis of heterochromatic epigenetic markers in the holocentric chromosomes of the aphid Acyrthosiphon pisum

Monomethylated-K9 H3 histones (Me9H3) and heterochromatin protein 1 (HP1) are reported as heterochromatin markers in several eukaryotes possessing monocentric chromosomes. In order to confirm that these epigenetic markers are evolutionarily conserved, we sequenced the HP1 cDNA and verified the distribution of Me9H3 histones and HP1 in the holocentric chromosomes of the aphid Acyrthosiphon pisum. Sequencing indicates that A. pisum HP1 cDNA (called ApHP1) is 1623 bp long, including a 170 bp long 5'UTR and a 688 bp long 3'UTR. The ApHP1 protein consists of 254 amino acidic residues, has a predicted molecular mass of 28 kDa and a net negative charge. At the structural level, it shows an N terminal chromo domain and a chromo shadow domain at the C terminus linked by a short hinge region. At the cytogenetic level, ApHP1 is located exclusively in the heterochromatic regions of the chromosomes. The same heterochromatic regions were labelled after immuno-staining with antibodies against Me9H3 histones, confirming that Hp1 and Me9H3 co-localize at heterochromatic chromosomal areas. Surprisingly, aphid heterochromatin lacks DNA methylation and methylated cytosine residues were mainly spread at euchromatic regions. Finally, the absence of DNA methylation is observed also in aphid rDNA genes that have been repeatedly described as mosaic of methylated and unmethylated units in vertebrates.

X-linked heterochromatin distribution in the holocentric chromosomes of the green apple aphid Aphis pomi

Chromatin organization in the holocentric chromosomes of the green apple aphid Aphis pomi has been investigated at a cytological level after C-banding, NOR, Giemsa, fluorochrome staining and fluorescent in situ hybridization (FISH). C-banding technique showed that heterochromatic bands are exclusively located on X chromosomes. This data represents a peculiar feature that clearly contradicts the equilocal distribution of heterochromatin typical of monocentric chromosomes. Moreover, silver staining and FISH carried out with a 28S rDNA probe localized rDNA genes on one telomere of each X chromosome; CMA3 staining reveals that these silver positive telomeres are the only GC-rich regions among A. pomi heterochromatin, whereas all other C-positive bands are DAPI positive thus containing AT-rich DNA.

Cytogenetic and molecular characterization of the MBSAT1 satellite DNA in holokinetic chromosomes of the cabbage moth, Mamestra brassicae (Lepidoptera)

Digestion of Mamestra brassicae DNA with DraI produced a prominent fragment of approximately 200 bp and a ladder of electrophoretic bands with molecular weights which are a multiple of 200 bp. Southern blotting revealed that this ladder is composed of DNA fragments that are multimers of the 200-bp DraI band suggesting that DraI isolated a satellite that has been called Mamestra brassicae satellite DNA1 (MBSAT1). MBSAT1 is the first satellite DNA isolated in Lepidoptera. In-situ DraI digestion of chromosome spreads, together with fluorescent in-situ hybridization, showed that MBSAT1 sequences are clustered in heterochromatin of the sex chromosomes, Z and W. MBSAT1 was 234 bp long with an AT content of 60.7%. The curvature-propensity plot suggested a curvature in the MBSAT1 structure.

Cytogenetic characterization of telomeres in the holocentric chromosomes of the lepidopteran Mamestra brassicae

Telomeres of the Mamestra brassica holocentric chromosomes were studied by Southern blotting, in-situ hybridization and Bal31 assay evidencing the presence of the telomeric (TTAGG)n repeat. Successively, molecular analysis of telomeres showed that TRAS1 transposable elements were present at the subtelomeric regions of autosomes but not in the NOR-bearing telomeres of the Z and W sex chromosomes. TRAS1 appeared to be transcriptionally active and non-methylated, as evaluated by RT-PCR and digestion with MspI and HpaII. Finally, dot-blotting experiments showed that the 2.8 +/- 0.5% of the M. brassicae genome consists of TRAS1.

Cytogenetic analysis of the pufferfish Tetraodon fluviatilis (Osteichthyes)

Because of their compact genome, pufferfish (Tetraodontiformes) have been proposed as a model for the study of the vertebrate genome. The genome of pufferfish is peculiar as it has the structural complexity of the genomes of higher vertebrates, but has small introns and lacks large clusters of highly repetitive sequences. Despite such interest, information about the genetics of pufferfish is still scanty. To fill this gap, we have performed a cytogenetic analysis of the pufferfish, Tetraodon fluviatilis, which can be maintained in an aquarium for a long time and, unlike the pufferfish, Fugu rubripes, it is not difficult to obtain. Karyotype analysis shows that T. fluviatilis has 2n = 42 with two metacentric chromosomes, four submetacentrics, two subtelocentrics and 34 acrocentrics. C-banding, followed by DAPI staining, showed that heterochromatin is essentially AT-rich and is located at centromeres. Staining of the same metaphase plates with CMA3 showed the presence of four heterochromatic regions located on two pairs of submetacentric chromosomes. Silver staining and FISH with a 28S rDNA probe showed that these GC-rich regions are nucleolar organizing regions (NORs). Finally, regardless of the technique used, no difference in the chromosome complement was found between males and females.

Specific heterochromatic banding of metaphase chromosomes using nuclear yellow

The bis-benzimidazole compound nuclear yellow (NY) belongs to the same chemical family as the DNA binding fluorochromes Hoechst 33258 and Hoechst 33342. Spectroscopic studies of NY alone and in the presence of calf thymus DNA show high DNA binding affinity and behavior similar to the Hoechst fluorochromes above. Mitotic metaphase chromosomes from Balb/c mice stained with NY show C-banding and weak G/Q-banding, both of them disappearing after distamycin A (DA) or methyl green (MG) counterstaining. The same staining of human metaphase chromosomes from lymphocyte cultures, however, reveal only faint G/Q-banding (NY) and a characteristic DA-DAPI-like banding (NY-DA, NY-MG). Image analysis of NY stained human chromosomes, confirms that NY is suitable for studying polymorphisms affecting size in the pericentromeric heterochromatin of pairs 1, 9 and 16, and shows significant enhancement of NY fluorescence induced by DA in DA-DAPI heterochromatin. Our spectroscopic and cytological results show that NY, either alone or counterstained with DA or MG, can be used for DNA cytochemistry and chromosome banding. Possible mechanisms for the banding patterns induced by NY are discussed.

Analysis of constitutive heterochromatin of Aotus (Cebidae, Primates) by restriction enzyme and fluorochrome bands

The current classification of genus Aotus includes nine species, four of which occur above the Amazon River and five below it. The position of several of these taxa as a valid species has been questioned. Recently, we described the chromosomal constitution of a population in the state of Rondonia, Brazil, whose karyotype typically presented a considerable accumulation of constitutive heterochromatin. To best characterize these heterochromatins, in this work we subjected the metaphases of these animals to banding using AluI, HaeIII, HinfI, RsaI, DdeI, MboI and MspI restriction enzymes and CMA3 and DAPI fluorochromes. The banded metaphases were also submitted to sequential C-banding. RsaI, DdeI and MboI enzymes showed, in all chromosomes, a banding pattern of C type, similar to that obtained using barium hydroxide. This banding was also seen with AluI, HinfI and MspI, but with reduction or elimination of the C-bands in the chromosome pairs 1, 3-7 and 9. MspI also reduced the C-band of pairs 11, 16-21 and 23. HaeIII induced intermediate bands between G and C. Considering the data of the different bands produced, it was possible to characterize at least three distinct types of constitutive heterochromatin in Aotus from Rondonia: (a) centromeric bands, (b) bands of the heterochromatic short arms and (c) interstitial bands.

Heterochromatin heterogeneity in the holocentric X chromatin of Megoura viciae (Homoptera, Aphididae)

Holocentric chromosomes, prepared by spreading embryo cells obtained from Megoura viciae parthenogenetic females, have been C-banded, enzymatically digested in situ using the specific endonucleases DdeI (C↓TNAG), DraI (TTT↓AAA), Tru9I (TT↓AA), and CfoI (GCG↓C), and subsequently stained with Giemsa, DAPI, CMA3, and AgNO3. We observed that the X chromosome had the best defined banding patterns. In the M. viciae X chromosome there is a certain amount of heterogeneity in heterochromatic DNA composition. In fact, the GC-rich NOR-associated heterochromatin differs from other heterochromatic bands that are characterized by AT-rich DNAs. Our data also indicate that, in M. viciae holocentric chromosomes, all heterochromatic blocks are accessible to in situ enzyme attack, the only limit to the digestion being the presence or absence of recognition targets. This is an interesting point, since, in monocentric chromosomes, it is well known that in situ endonuclease digestion is heavily affected not only by DNA base composition but also by chromatin compactness that may limit enzyme accessibility to their specific targets. Key words : heterochromatin, holocentric chromosomes, aphids.

Sex dependent transmission of Beckwith-Wiedemann syndrome associated with a reciprocal translocation t(9;11)(p11.2;p15.5)

Beckwith-Wiedemann syndrome (BWS), a disorder associated with neonatal hypoglycaemia, increased growth potential, and predisposition to Wilms's tumour (WT) and other malignancies, has been mapped to 11p15. The association with 11p15 duplications of paternal origin, of balanced translocations and inversions with breakpoints within 11p15.4-p15.5 of maternal origin, and the demonstration of uniparental paternal 11p15 isodisomy in some sporadic cases point towards the involvement of genomic imprinting. In agreement with this, we show the paternal origin of a de novo 9;11 translocation in a phenotypically normal mother, whose carrier daughter developed BWS. This supports the fact that BWS associated with balanced chromosome mutations is transmitted in the same sex dependent pattern as non-cytogenetic forms of familial BWS.

Hypomethylation of human heterochromatin detected by restriction enzyme nick translation

Using the restriction enzymes MspI and HpaII in the nick translation procedure it has been shown that decondensation of the paracentric heterochromatin of chromosome 9 during human spermatogenesis is associated with hypomethylation of the DNA sequences in this domain. Somatic cells treated with 5'-azacytidine also showed decondensation of centromeric heterochromatin. In this instance, however, hypomethylation is detected both in the extended heterochromatin at the centromeres and in the euchromatin of the chromosome arms.

The organisation of repetitive DNA sequences on human chromosomes with respect to the kinetochore analysed using a combination of oligonucleotide primers and CREST anticentromere serum

The spatial relationship between the families of repetitive DNAs present at the centromeres of human chromosomes and the position of the kinetochore was examined by combining immunocytochemistry with the PRINS oligonucleotide primer extension technique. Heterochromatic domains were decondensed with 5'-azacytidine to facilitate this study. Using this approach our results clearly show that the alphoid DNA sequences are closely associated with the kinetochore of human chromosomes. Simple-sequence satellite DNAs occupy separate, non-overlapping domains within the centromere. These two major families are separated by a third, relatively low-copy repetitive DNA family, SAU-3A. Pulse-field gel electrophoresis was employed to analyse the centromeric domain of human chromosome no. 9 in more detail and the results although preliminary support the conclusions drawn from the immunocytochemistry/PRINS approach.

Antibodies to defined histone epitopes reveal variations in chromatin conformation and underacetylation of centric heterochromatin in human metaphase chromosomes

Unfixed metaphase chromosome preparations from human lymphocyte cultures were immunofluorescently labelled using antibodies to defined histone epitopes. Both mouse monoclonal antibody HBC-7, raised against the N-terminal region of H2B, and rabbit serum R5/12, which recognizes H4 acetylated at Lys-12, gave non-uniform labelling patterns, whereas control antibodies against total histone fractions H4 and H1 produced homogeneous fluorescence. HBC-7 bound approximately uniformly to the bulk of the chromosomes, but the major heterochromatic domains of chromosomes 1, 9, 15, 16 and the Y showed significantly brighter fluorescence. Serum R5/12 indicated an overall reduction in acetylation of H4 in metaphase chromosomes compared with interphase nuclei, although some specific chromosomal locations had considerably elevated acetylation levels. Acetylation levels in the major heterochromatic domains appeared extremely low. To investigate further the differences noted in heterochromatin labelling, metaphases from cultures grown in the presence of various agents known to induce undercondensation of the major heterochromatic domains were similarly immunolabelled. Decondensed heterochromatin no longer exhibited higher than normal immunofluorescence levels with HBC-7. The higher resolution afforded by "stretching" the centromeric heterochromatin of chromosomes 1, 9 and 16 confirmed the low level of H4 acetylation in these domains. We consider the implications of these observations in relation to chromatin conformation and activity.

Persistence of two Y chromosomes through meiotic prophase and metaphase I in an XYY man

Studies of spermatogenesis in an XYY male, presenting at a subfertility clinic, confirm the tendency for the germ cells to lose the second Y chromosome but for some XYY cells to reach metaphase I (MI). Light microscope studies of MI revealed the presence of YY bivalents and EM studies of microspread, silver-stained pachytene stages showed 30% of the cells to have two Y chromosomes; 13 out of 16 of these showing a YY synaptonemal complex. Strikingly, the Y axes show only partial synapsis; in no case was synapsis of the long arm heterochromatic regions apparent.

Chromosome studies and fertility treatment in women with ovarian failure

In vitro fertilization and embryo transfer or gamete (or zygote) intra-Fallopian transfer after ovum donation were performed in 16 patients with primary or secondary amenorrhea, associated with chromosome abnormalities. The patients showed the wide range of (mostly X) chromosome abnormalities characteristic for women with primary or premature ovarian failure. Four of these patients became pregnant and three of them have delivered healthy infants with a normal karyotype. This pregnancy rate is far superior to the accepted fertility figure in these patients. When these results were compared with the fertility treatment results of three other groups of women with absent ovarian function (1. ovarian dysgenesis; 2. surgical castration; 3. premature menopause) but with a normal 46,XX karyotype, no difference in treatment efficiency could be detected. These results offer a promising approach for the treatment of infertility in agonadal patients with chromosome aberrations.

Deleted Yq in the sterile son of a man with a satellited Y chromosome (Yqs)

Disturbed spermatogenesis and azoospermia are reported in a man with a deleted Y chromosome. The anomalous Y chromosome appears in the karyotype as a small metacentric marker. In situ hybridisation using three different Y specific DNA probes shows that deletion at Yq11 has resulted in loss of all distal heterochromatin. The sterility of the patient indicates loss also of the azoospermia factor (AZF) located at the Yq distal euchromatic/heterochromatic interface. Microspread and air dried meiotic preparations show a severe impairment of spermatogenesis but rare cells are seen to be progressing to the late prophase stage. The testicular histology shows most of the seminiferous tubules to be completely hyalinised. The father and a fertile brother of the proband show a satellited Y chromosome (Yqs) in their karyotypes. The case appears to be the first of its kind reported in which a father with a satellited Y chromosome has produced a son carrying a different Y chromosome anomaly. The possible derivation of the one from the other is discussed.

A cytogenetic and molecular analysis of five variant Philadelphia translocations in chronic myeloid leukemia

Three patients had complex translocations involving 9q34, 22q11, and a third chromosome (Xq11, 7q11.2, or 15q11.2). Two patients had apparently simple variant Philadelphia (Ph) translocations, t(19;22) and t(11;22), with no obvious involvement of chromosome 9, and the Ph was masked in the t(11;22). In situ hybridization studies showed transposition of the abl gene from chromosome 9q34 to the breakpoint cluster region (bcr) of chromosome 22 in all five patients; this was confirmed by rearrangements of the bcr gene in leukemic DNA. In situ hybridization also showed that the bcr-3' and c-sis probes consistently translocated to recipient chromosomes X, 1, 7, 11, and 15, whereas IgC lambda remained on chromosome 22q. These results confirm that association of abl and bcr is a consistent feature of chronic myeloid leukemia irrespective of the cytogenetic presentation and support the conclusion of Hagemeijer that all simple variant Ph translocations are, in fact, complex and involve at least three chromosomes.

Supernumary marker chromosomes in a mentally retarded population identified as inv dup(15)

Bisattelited supernumary chromosomes, identified as inv dup(15)s, were detected at a prevalence of 8/1000 among institutionalized, mentally retarded (non-Down syndrome) males. This finding suggests that the inv dup(15) contributes significantly to the etiology of mental retardation among institutionalized individuals.

Interstitial deletion and ring chromosome derived from 16q

An interstitial deletion of 16q was identified in an infant with failure to thrive, dysmorphic facies, and congenital heart defects. The mother of this infant had a similar deletion of 16q with ring formation of a fragment presumed to be derived from the deleted portion of 16q. We discuss these cases and compare them to other reports of 16q deletions.

Cat-eye syndrome with different marker chromosomes in a mother and daughter

Except for atypical eye findings in the daughter, a mother and daughter with bisatellited marker chromosomes had abnormalities consistent with cat-eye syndrome. The mother's marker chromosome (mar number 1) is derived from one 22 and another acrocentric, possibly also a 22; the daughter's marker (mar number 2) may be an iso-dicentric, inv-dup (22) derivative of mar number 1. The mother has a tertiary trisomy translocation chromosome composed of at least one and perhaps two copies of 22pter----q11.2, whereas the daughter clearly has a secondary trisomy 22pter----q11.2 isochromosome, confirming this region as a cause of cat-eye syndrome. Results of hybridization using a unique sequence probe localized to 22q11 are consistent with the interpretation that both ends of both marker chromosomes are derived from 22.

Simultaneous production of R-bands and either replication patterns or sister chromatid differentiation

The dye triplet chromomycin/methyl green/DAPI and some related dye combinations were applied to bromodeoxyuridine (BrdU)-substituted and non-substituted chromosomes. In both kinds of chromosome preparations, tri-staining followed by observation at pH 7 resulted in well defined R-bands (excitation wavelength 436 nm) and a mixed DA-DAPI/Q-banding pattern (360 nm). Two approaches have given satisfactory expression both of reverse bands and of the differential BrdU-substitution present in metaphase chromosomes: (1) direct tri-staining at pH 7 and mounting of the preparations at pH 11; or (2) pretreatment of the preparations with Hoechst 33258 plus UV and hot buffer followed by tri-staining and mounting at pH 7. These methods should prove useful for routine chromosome analysis and, in combination with BrdU-labelling, in studies of chromosome structure and replication.