Individual and age-related characteristics of the mitotic condensation of human Y chromosome

Three types of contraction (steady, speeding and slowing) of fluorescent (f) and nonfluorescent (nf) parts of the human Y chromosome were revealed in the spiralization interval limited by reper chromosome 3 length from 16.6 to 2.9 mkm. On the basis of regression analysis it was shown that in the initial phase of the spiralization interval studied the f-block was condensed more rapidly than the nf-region; then the speed of contraction of the latter exceeded that of the former. A decline of the Y chromosome condensation in relation to ageing was revealed. A possible chromosome segregation disturbance in gametogenesis due to senescent changes of heterochromatic regions is discussed.     

Differential spiralization along mammalian mitotic chromosomes

Morphology of chromosomes replicating in the presence of 5-bromodeoxyuridine was studied using long-term cultures of Chinese hamster cells (line Blld-ii-FAF28). The cytological effect of the analog administered in various concentrations, at different stages of the S period, and during one and two successive mitotic cycles was studied. — The main cytological manifestation of the BUdR action consisted in spiralization delay of certain chromosome regions. The degree of the delay was dependent on the time interval between the introduction of the agent and mitosis, as well as on the agent's concentration. With prolongation of the interval, the spiralization delay diminished and disappeared being therefore always observable only in late replicating chromosome regions. Increased concentration of BUdR (in the range of 25 to 400 g/ml) produced enhancement of the delay of chromosome spiralization. — After two successive reproduction cycles in the presence of BUdR, a great number of metaphases contained chromosomes the sister chromatids of which showed unequal spiralization delay. Autoradiography of ³H-BUdR distribution showed that the sister chromatid with a more pronounced underspiralization corresponds to the chromatid incorporating BUdR into both strands of the DNA molecule. — Mechanisms of the effect observed, as well as chemical influence on chromosome spiralization as a usefull tool of displaying linear chromosome differentiation, are discussed.     

Relation between the size of C-segments and corresponding euchromatic regions of human chromosomes 1, 9 and 16 during their mitotic condensation

The nature of associations between the length of C-segments and the corresponding euchromatic regions of chromosomes 1, 9, and 16 in the process of their mitotic condensation has been studied. Their statistically significant linear nature in the range of chromosome 2 condensation from 11 to 4 micron has been established. Within the interval of 6.5-8.5 micron the above association is less significant, at the same time minimal variability of C-segment length is observed as compared to other stages of mitotic condensation. It is recommended to define the absolute size of C-segments in chromosomes 1, 9 and 16 by measuring their dimensions in metaphase plates with chromosome 2 length from 6.5 to 8.5 micron. The regressional correction of the results of C-segment measurements or approximation of values depending on the statistical significance of linear regression equation coefficient has been demonstrated.     

Effects of distamycin A on human leukocytes in vitro.

Distamycin A, an oligopeptide antibiotic, supplied at various concentrations for 24 h to human leukocytes in culture, has induced the appearance on some chromosomes of specific areas lacking spiralization. In particular, the centromeric regions of chromosomes 1, 3 and one C-group chromosome and the distal part of the long arm of the Y chromosome were despiralized. The possible nature of these regions is discussed.     

Change in the microchromosome number in the process of macrochromosome spiralization in Gallus domesticus

A correlation of mitotic spiralization of macrochromosomes with a change in the number of microchromosomes is detected. A wave character of microchromosomes variability during spiralization of macrochromosomes is suggested to be due to reversible despiralization of microchromosomes, which is probably a result of the colchicin treatment. Metaphase plates where the range of chromosome 1 length is from 10.5 to 12mu are recommended to calculate the number of microchromosomes.     

Fine Mapping of Satellite DNA Sequences along the Y Chromosome of Drosophila Melanogaster: Relationships between Satellite Sequences and Fertility Factors

The entirely heterochromatic Y chromosome of Drosophila melanogaster contains a series of simple sequence satellite DNAs which together account for about 80% of its length. Molecular cloning of the three simple sequence satellite DNAs of D. melanogaster (1.672, 1.686 and 1.705 g/ml) revealed that each satellite comprises several distinct repeat sequences. Together 11 related sequences were identified and 9 of them were shown to be located on the Y chromosome. In the present study we have finely mapped 8 of these sequences along the Y by in situ hybridization on mitotic chromosome preparations. The hybridization experiments were performed on a series of cytologically determined rearrangements involving the Y chromosome. The breakpoints of these rearrangements provided an array of landmarks along the Y which have been used to localize each sequence on the various heterochromatic blocks defined by Hoechst and N-banding techniques. The results of this analysis indicate a good correlation between the N-banded regions and 1.705 repeats and between the Hoechst-bright regions and the 1.672 repeats. However, the molecular basis for banding does not appear to depend exclusively on DNA content, since heterochromatic blocks showing identical banding patterns often contain different combinations of satellite repeats. The distribution of satellite repeats has also been analyzed with respect to the male fertility factors of the Y chromosome. Both loop-forming (kl-5, kl-3 and ks-1) and non-loop-forming (kl-2 and ks-2) fertility genes contain substantial amounts of satellite DNAs. Moreover, each fertility region is characterized by a specific combination of satellite sequences rather than by an homogeneous array of a single type of repeat.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bends in human mitotic metaphase chromosomes, including a bend marking the X-inactivation center.

Bends in mitotic metaphase chromosomes are not distributed randomly throughout the karyotype. The frequency of bends at centromeres is positively correlated with the relative length of the chromosomes and negatively correlated with the centromere index (more bends in metacentrics, fewer in acrocentrics). The frequency of bends in the noncentromeric regions (except at Xq13-Xq21) is positively correlated with the relative length of chromosome arms. A bend at Xq13.3 to Xq21.1 was more frequent than a bend in any other region of the karyotype, centromeric or noncentromeric. It was observed in one member of the X-chromosome pair in 63% of 46,XX cells. In contrast, it was observed in only 2% of 46,XY cells. RBG-staining showed that this specific bend is confined to the lyonized X chromosome. These observations in cells from normal subjects were confirmed using G-banding and RBG-staining on cells from nine subjects with different X-chromosome abnormalities and on metaphases from amniotic fluid cell and lymphocyte cultures. The "center for Barr body condensation" has been localized to the region between Xq11.2 and Xq21.1. The functional and structural relationship is unclear, but we believe this highly specific bend may represent a visible manifestation of the condensation process; it could represent the first folded (and last unfolded) position, upon or around which the rest of the chromosome condenses. The late replication of this region may also be a factor. The smallest region of overlap (SRO) for the X-chromosome inactivation center and the specific chromosome bend is Xq13.3 to Xq21.1.     

A standard cytogenetic map for Anopheles sundaicus (Diptera: Culicidae) and evidence for chromosomal differentiation in populations from Thailand and Indonesia.

A standard photographic map of polytene chromosomes of Anopheles sundaicus was constructed from ovarian nurse cells and is described herein. Polytene chromosomes of wild specimens collected from 9 different geographical areas in Thailand and Indonesia have been analyzed. Specimens from these populations appear to share banding patterns with standard gene arrangements, except for some specimens from Purworejo, in Central Java, and South Tapanuli and Asahan, both of North Sumatra, which exhibited distinct banding patterns at the tip of chromosome X (Xb) compared with the standard sequence (Xa). Moreover, some specimens collected from Asahan, North Sumatra, consistently showed distinct loosely diffuse bands in zone 19 of chromosome arm 2R (2Rb) compared with the standard banding patterns (2Ra). The existence of the 2Rb pattern correlates perfectly with the presence of an extra block of centromeric heterochromatin in autosome 2 as revealed by mitotic karyotype analysis (2n = 6). These cytological differences have led to the recognition of 3 distinct forms, viz., A, B, and C, within the taxon An. sundaicus. In addition, forms A and C show a normal size for chromosome Y, (Y1), while form B has a relatively larger type of chromosome Y, (Y2). Form A is widely distributed in Thailand and Indonesia, while form B has been found in North Sumatra and Central Java. Form C, however, has been found only in Asahan, North Sumatra. Key words : Anopheles sundaicus, polytene chromosome map, mitotic karyotype, chromosomal differentiation.     

Characteristics of the morphology and mitotic condensation of human Y chromosomes with structural rearrangements

Parameters of the length and mitotic condensation were investigated in the following cases of Y-chromosome aberrations: isodicentric Y(q), Y-chromosome without heterochromatic block, and Y-chromosome with satellites. In the Ydic we revealed some differences between f-block, that is located near the inactive kinetochore, and the block near the active centromere. Satellites exert no influence on the mitotic function of Y chromosome, presumably owing to the presence of C-heterochromatic material. With the absence of heterochromatic region, a decline in condensation of the non-fluorescent segment was observed in addition to a simultaneous increase in its length. The mechanism of functioning of the structural heterochromatin is discussed.     

白鱀豚的核型及其C－带核型的研究

采用常规的白细胞培养技术及ＢＳＧＣ－带技术分析了白豚的核型、Ｃ－带核型。结果是：白豚的染色体数目２ｎ＝４４,其核型由１２条中部着丝点染色体、１８条亚中部着丝点染色体、４条亚端部着丝点染色体、８条端部着丝点染色体和２条性染色体所组成。染色体臂数（ＮＦ）雌性为７６,雄性为７５。Ｃ－带异染色质呈现出很深的着色区,主要分布在染色体臂上,着丝点区则几乎没有。Ｃ－带异染色质的量约为总染色质量的１２％。这一结果表明白豚与海生豚类的核型、Ｃ－带核型有较明显的相似性。     

Deacetylation and methylation at histone H3 lysine 9 (H3K9) coordinate chromosome condensation during cell cycle progression

Interphasic chromatin condenses into the chromosomes in order to facilitate the correct segregation of genetic information. It has been previously reported that the phosphorylation and methylation of the N-terminal tail of histone H3 are responsible for chromosome condensation. In this study, we demonstrate that the deacetylation and methylation of histone H3 lysine 9 (H3K9) are required for proper chromosome condensation. We confirmed that H3K9ac levels were reduced, whereas H3K9me3 levels were increased in mitotic cells, via immunofluorescence and Western blot analysis. Nocodazole treatment induced G2/M arrest but co-treatment with TSA, an HDAC inhibitor, delayed cell cycle progression. However, the HMTase inhibitor, AdoX, had no effect on nocodazole-induced G2/M arrest, thereby indicating that sequential modifications of H3K9 are required for proper chromosome condensation. The expression of SUV39H1 and SETDB1, H3K9me3-responsible HMTases, are specifically increased along with H3K9me3 in nocodazole-arrested buoyant cells, which suggests that the increased expression of those proteins is an important step in chromosome condensation. H3K9me3 was highly concentrated in the vertical chromosomal axis during prophase and prometaphase. Collectively, the results of this study indicate that sequential modifications at H3K9 are associated with correct chromosome condensation, and that H3K9me3 may be relevant to the condensation of chromosome length.     

Alpha and beta heterochromatin in polytene chromosome 2 ofDrosophila melanogaster

The formation of alpha and beta heterochromatin in chromosomes of Drosophila melanogaster was studied in salivary glands (SGs) and pseudonurse cells (PNCs). In SGs of X0, XY, XYY, XX and XXY individuals the amounts of alpha heterochromatin were similar, suggesting that the Y chromosome does not substantially contribute to alpha heterochromatin formation. Pericentric heterochromatin developed a linear sequence of blocks in PNCs, showing morphology of both alpha and beta heterochromatin. In situ hybridization with Rsp sequences (H _o clone) revealed that the most proximal heterochromatic segment of the mitotic map (region h39) formed a polytenized block in PNCs. Dot analysis showed that the clone had a hybridization rate with PNC-DNA very close to that with DNA from mainly diploid head cells, whereas the homologous SG-DNA was dramatically underrepresented. A similar increase of DNA representation in PNC was found for AAGAC satellite DNA. The mitotic region h44 was found not to polytenize in the SG chromosome, whereas in PNC chromosome 2 this region was partly polytenized and presented as an array of several blocks of alpha and beta heterochromatin. The mapping of deficiencies with proximal breakpoints in the most distal heterochromatin segments h35 in arm 2L and h46 in 2R showed that the mitotic eu-heterochromatin transitions were located in SG chromosomes distally to the polytene 40E and 41C regions, respectively. Thus, the transition zones between mitotic hetero- and euchromatin are located in banded polytene euchromatin. A scheme for dynamic organization of pericentric heterochromatin in nuclei with polytene chromosomes is proposed. Received: 17 November 1995; in revised form: 10 April 1996 / Accepted: 18 September 1996     

Evidence for a highly differentiated sex chromosome heteromorphism in the salamander Necturus maculosus (Rafinesque)

The mitotic chromosomes of the neotenic (sensu Gould, 1977, and Alberch et al., 1979) salamander Necturus maculosus (Rafinesque) have been examined using a C-band technique to demonstrate the distribution of heterochromatin. The C-banded mitotic chromosomes provide evidence of a highly differentiated XY male/XX female sex chromosome heteromorphism, in which the X and Y chromosomes differ greatly in size and morphology, and in the amount and distribution of C-band heterochromatin. The X chromosome represents one of the largest biarmed chromosomes in the karyotype and is indistinguishable from similar sized autosomes on the basis of C-band heterochromatin. The Y chromosome, on the other hand, is diminutive, morphologically distinct from all other chromosomes of the karyotype, and is composed almost entirely of C-band heterochromatin. The discovery of an X/Y chromosome heteromorphism in this species is consistent with the observation by King (1912) of a heteromorphic spermatogenic bivalent. Karyological and phylogenetic implications are discussed.     

First evidence of sex chromosome pre-reduction in male meiosis in the Miridae bugs (Heteroptera)

The karyotype and male meiosis of Macrolophus costalis Fieber (Insecta, Heteroptera, Miridae) were studied using C-banding, AgNOR-banding and DNA sequence specific fluorochrome staining. The chromosome formula of the species is 2n = 28(24+X1X2X3Y). Male meiotic prophase is characterized by a prominent condensation stage. At this stage, two sex chromosomes, "X" and Y are positively heteropycnotic and always appeared together, while in autosomal bivalents homologous chromosomes were aligned side by side along their entire length, that is, meiosis is achiasmatic. At metaphase I, "X" and Y form a pseudobivalent and orient to the opposite poles. At early anaphase I, the "X" chromosome disintegrates into three separate small chromosomes, X1, X2, and X3. Hence both the autosomes and sex chromosomes segregate reductionally in the first anaphase, and separate equationally in the second anaphase. This is the first evidence of sex chromosome pre-reduction in the family Miridae. Data on C-heterochromatin distribution and its composition in the chromosomes of this species are discussed.     

Telomeric chromosome fusion in cells with micronuclei under the combined action of hyperthermia and hypothermia and halogenated analogs of thymidine]

The reaction of cells with micronuclei in respect of the induction of specific dicentric chromosomes with halogenated analogs of thymidine at various temperatures was studied. The positive correlation between the temperature and frequency of dicentrics was shown for all halogenated analogs of thymidine. The minimum frequency of dicentrics was found in the case when used 5-iododeoxyuridine and hypothermia (34 degrees C). The using of 5-bromodeoxyuridine at different temperatures displayed the intermediate results. The maximum level of dicentrics discovered under action of 5-chlorodeoxyuridine and hyperthermia (40 degrees C). In the former case the depression of mitotic chromosome condensation of micronuclei registered, in the latter one the chromosomes with portions of delayed spiralization were not found.     

Cytogenetics of the chinese giant salamander,Andrias davidianus (Blanchard): the evolutionary significance of cryptobranchoid karyotypes

Cytogenetic aspects of the cryptobranchid salamander Andrias davidianus of western China have been studied, including chromosome number and morphology, C-band patterns, meiosis, and the chromosomal localization of ribosomal 5S RNA genes. Our data regarding chromosome number (2n=60) and general chromosome morphology largely confirm the results of Morescalchi et al. (1977). The karyotype consists of 16 pairs of macrochromosomes that decrease gradually in relative length to 14 pairs of microchromosomes. Telocentric chromosomes are a conspicuous feature of the karyotype, representing more than half the genome. Differential staining reveals that all of the chromosomes, except four pairs of microchromosomes, have C-band heterochromatin in their centromeric regions, the amount varying irrespective of chromosome size. Faint bands of interstitial and telomeric C-band heterochromatin are found in mitotic chromosomes but are not seen in meiotic preparations. In C-banded mitotic preparations from a female, one of the smallest macrochromosome pairs is heteromorphic in respect to C-band heterochromatin and centromere position. In situ hybridization of an iodinated 5S RNA probe to meiotic chromosome preparations reveals that this repeated gene is clustered near the telomeric region of chromosome 7, a medium size telocentric, a location corresponding to a band of heterochromatin. Studies of spermatocytes indicate that the process of meiosis in A. davidianus closely resembles that of more advanced salamanders, and that the microchromosomes are meiotically stable. The significance of microchromosomes and chromosome morphology in the reorganization of salamander genomes during evolution is discussed on the basis of cytogenetic data available for A. davidianus and various other primitive and advanced salamanders.     

Karyomorphology of four species in Ancylostemon,Briggsiopsis and Lysionotus (Gesneriaceae)

Reported in the present paper are chromosome numbers and karyotypes of three genera of the Gesneriaceae, i.e. Ancylostemon Craib. , Briggsiopsis (Franch.) K. Y. Pan and Lysionotus D. Don. The former two genera are endemic to China. The karyotype of Ancylostemon aureus (Franch.) Burtt is formulated as 2n = 34 = 20m(1sat) + 14sm, with the same chromosome number as its allied species A. convexus Craib. This species is characterized by the interphase nucleus of complex chromocenter type and the proximal type of chromosomes in the mitotic prophase. The chromosome number of the monospecific genus Briggsiopsis is 2n = 34, the same as the lowest chromosome number reported in Briggsia. The karyotype of Briggsiopsis, which is formulated as 2n = 25m + 6sm + 3st, also seems to be primitive among the species of the two genera. Briggsiopsis is characterized by the interphase nucleus of simple-complex chromocenter type and the interstitial-gradient type of chromosomes in the mitotic prophase. The chromosome number of Lysionotus carnosus Hemsl. is the lowest reported in this genus. Its karyotype is formulated as 2n= 30 = 21m + 5sm + 3st + lt. Lysionotus serratus var. pterocaulis, with the karyotype being formulated as 2n= 32 = 2lm + 10sm + lt, has the same chromosome number as var. serratus. These two species show a remarkable differentiation of karyotypes and are characterized by the interphase nuclei of simple-complex chromocenter type and the gradient type of chromosomes in the mitotic prophase. _ .     

The karyotype of the South American rodent Kunsia tomentosus (Lichtenstein, 1830).

Chromosomal analysis of Kunsia tomentosus showed a karyotype with 2n = 44, constituted by 21 pairs of acrocentric autosomes. The X chromosome was a median acrocentric, between pairs 3 and 4 in size, and the Y chromosome was a small acrocentric (between pairs 19 and 20). Five pairs with nucleolus organizer regions were located at the short arms. C-banding showed blocks of constitutive heterochromatin occurring in the centromeres of all autosomes and of the X chromosome. The Y chromosome was entirely heterochromatic. In order to identify possible homologies, karyotypes of Kunsia and Scapteromys, the phyletically related taxa, were compared. No autosome shared by either genus was found by G-band comparisons. The C-band patterns and those produced by Alu I, Mbo I, Rsa I and Hae III restriction endonucleases were also different. The results of FISH indicated a different composition of the telomeric regions of the chromosomes of both taxa, since in Scapteromys the probes hybridized in both telomeres, and in Kunsia this hybridization only occurred in one of the telomeres. These differences also occurred in the localization and number of nucleolus organizer regions.     

Effects of DAPI on human leukocytes in vitro.

DAPI (4'-6-diamidino-2-phenylindole), a fluorochrome specific for AT-rich DNA, was supplied for 24 h at various concentrations to human leukocytes in culture. This treatment caused the appearance on the chromosomes of specific areas lacking spiralization. In particular, the centromeric regions of chromosomes 1,9, and 16, a short region on the long arm of chromosomes 1 and 2, and the distal heterochromatic part of the long arm of the Y chromosome were despiralized. The despiralization pattern of DAPI is compared with those previously obtained with Hoechst 33258 and Distamycin A.