Q-, C-, and G-banding patterns in the germ-line and somatic chromosomes of Miastor sp. (Diptera: cecidomyidae)

Q-, C-, and G-banding patterns are described for the germ-line and somatic chromosomes of Miastor sp. The chromosome number in the germ line is 36, which is 3 less than that previously reported for the same cultured line 18 years ago. There are 8 chromosome groups: 8 large acrocentrics, 11 large and medium submetacentrics, 4 medium metacentrics, 4 medium subtelocentrics, 6 medium telocentrics, one medium acrocentric, one small submetacentric, and one small telocentric. All 8 large acrocentrics have a Q-band and an interstitial C-band in the short arm, suggesting that these chromosomes are at least partially homologous (or homeologous) and that the germ line originally was polyploid. Only one other germ-line chromosome, the small submetacentric, has a Q-band and an interstitial C-band. In somatic cells there are 8 chromosomes, 28 chromosomes having been eliminated during early cleavage. Three of the four pairs of somatic chromosomes are heteromorphic, despite the indications of a polyploid origin of the germ-line chromosomes and despite the presence of somatic pairing. Furthermore, there is a great deal of restriction on which chromosomes are retained in somatic cells, and it may be that the same 8 chromosomes are retained by all embryos. The G-banding pattern is not as clear as the other two banding patterns. The findings are discussed in relation to observations in other cecidomyids, and a model for the evolution of the chromosome system of Miastor is presented.     

Chromosomal banding pattern and idiogram of the cotton rat,Sigmodon arizonae (Rodentia,Muridae)

A procedure for obtaining G-bands on chromosomes of mammals is outlined. The procedure was utilized in an investigation of the idiogram and banding pattern of the mitotic chromosomes of the cotton rat, Sigmodon arizonae. The diploid number of this species is 22, and each pair of homologues is easily separated on the basis of size, centromeric position, and banding pattern. The autosomes are represented by four pairs of large submetacentric chromosomes, three pairs of medium to small submetacentric chromosomes, two pairs of large subtelocentric chromosomes and one pair of small acrocentric chromosomes. The X chromosome is acrocentric and averages from 5.42% to 5.46% of the haploid female complement. The Y chromosome is a minute acrocentric and easily separated from the smallest acrocentric autosome. The usefulnes of Sigmodon arizonae as a laboratory animal for cytogenetic studies is substantiated.     

Observations on the extent and temporal stability of latitudinal clines for alcohol dehydrogenase allozymes and four chromosome inversions in Drosophila melanogaster

The chromosomes of embryos within thelytokous females of Forda spp. were studied, in samples from galls on Pistacia in the Middle East, and from roots of Poaceae in the Middle East, Europe and North America. The nuclei of oogonial cells, oocytes and early cleavage stages have consistently more chromosomes than the nuclei of dividing cells in the somatic tissues of young embryos from the same mothers. Elimination of the extra germ line chromosomes apparently occurs in late cleavage. In F. marginata Koch the germ line chromosome number varies from 25 to 40 in different populations and the somatic cell number varies from 17 to 20; in F. formicaria the germ line has 21–23 chromosomes and somatic nuclei have 18 or 20. In both species variation occurs between samples from galls on Pistacia as well as between populations on roots of Poaceae. The numbers and relative sizes of the eliminated chromosomes also differ between populations. Comparable phenomena in other insects are briefly discussed.     

Karyotype of the Snow Sculpin <Emphasis Type="Italic">Myoxocephalus brandti</Emphasis> Steindachner (Cottidae) from Peter the Great Bay,Sea of Japan

The karyotype of the snow sculpin Myoxocephalus brandti, 2n = 44, NF = 46, from Peter the Great Bay was studied. Two-armed chromosomes were presented by one pair of metacentric chromosomes of medium size; one-armed chromosomes included two pairs of large subtelocentric chromosomes and a pair of large acrocentric chromosomes. Ag-NOR-staining in the telomere vicinity revealed nucleolus-organizing regions in one metacentric chromosome and in one medium size acrocentric chromosome in one of the fishes, in two homological small acrocentric chromosomes in three fishes, and in one acrocentric chromosome of average size in six fishes. No difference between the male and female karyotypes and any type of variability was revealed. The karyotypes of the snow sculpin M. brandti and the frog sculpin M. stelleri were compared. Their distinctions and similarities were displayed.Original Russian Text Copyright ¢ 2005 by Biologiya Morya, Ryazanova.     

Photoreversible inhibition by ultraviolet light of germ line development in Smittia sp. (Chironomidae, Diptera)

Pole cell formation in embryos of the parthenogenetic midge, Smittia sp., can be delayed or inhibited by irradiation of the posterior egg pole with ultraviolet light (uv). This leaves the schedule of nuclear divisions and chromosome eliminations virtually unaffected. However, uv irradition delays the precocious migration to the posterior pole of one nucleus, which normally becomes included in the first pole cell. This effect is photoreversible, i.e., mitigated by application of blue light after uv. Photoreversibility indicates that a nucleic acid component is involved as an effective target. During normal development of Smittia a number of chromosomes are eliminated during mitosis V, not only from somatic nuclei but also in the germ line. In the latter, this mitosis takes place during the first gonial division in the larva. After uv irradiation, the first pole cell nucleus has undergone supernumerary mitoses before pole cell formation and, as a result, is driven into mitosis V precociously as the pole cell divides. This is frequently associated with chromosome elimination from pole cells, which in turn is correlated with subsequent disappearance of already formed pole cells. Adults derived from embryos without pole cells do not form ovaries. Pole cell formation, pole cell preservation, and ovary development are separately inhibited by uv, and inhibition of each step is photoreversible. The results are discussed in the context of germ cell determination, protection against chromosome elimination, and the role of chromosomes limited to the germ line.     

Homologous banding patterns in the polytene chromosomes from the larval salivary glands and ovarian nurse cells of Anopheles stephensi liston (Culicidae)

A comparison of the banding patterns of two homologous polytene chromosome arms from the larval salivary gland and ovarian nurse cell complement of Anopheles stephensi is presented. The homologous chromosomes from the somatic larval salivary glands and germ-line derived ovarian nurse cells have essentially the same band-interband organisation. An analysis of the ³H-uridine labelling patterns of a small chromosome segment from the two tissues indicates that germ-line polytene chromosomes are not radically different from somatic polytene chromosomes in their patterns of gene expression.     

Physical mapping of the 5S ribosomal RNA genes in Arabidopsis thaliana by multi-color fluorescence in situ hybridization with cosmid clones

The 5S ribosomal RNA genes were mapped to mitotic chromosomes of Arabidopsis thaliana by fluorescence in situ hybridization (FISH). In the ecotype Landsberg erecta, hybridization signals appeared on three pairs of chromosomes, two of which were metacentric and the other acrocentric. Hybridization signals on one pair of metacentric chromosomes were much stronger than those on the acrocentric and the other pair of metacentric chromosomes, probably reflecting the number of copies of the genes on the chromosomes. Other ecotypes, Columbia and Wassilewskija, had similar chromosomal distribution of the genes, but the hybridization signals on one pair of metacentric chromosomes were very weak, and detectable only in chromosomes prepared from young flower buds. The chromosomes and arms carrying the 5S rDNA were identified by multi-color FISH with cosmid clones and a centromeric 180 bp repeat as co-probes. The metacentric chromosome 5 and its L arm carries the largest cluster of the genes, and the short arm of acrocentric chromosome 4 carries a small cluster in all three ecotypes. Chromosome 3 had another small cluster of 5S rRNA genes on its L arm. Chromosomes 1 and 2 had no 5S rDNA cluster, but they are morphologically distinguishable; chromosome 1 is metacentric and 2 acrocentric. Using the 5S rDNA as a probe, therefore, all chromosomes of A. thaliana could be identified by FISH. Chromosome 1 is large and metacentric; chromosome 2 is acrocentric carrying 18S-5.8S-25S rDNA clusters on its short arm; chromosome 3 is metacentric carrying a small cluster of 5S rDNA genes on its L arm; chromosome 4 is acrocentric carrying both 18S-5.8S-25S and 5S rDNAs on its short (L) arm; and chromosome 5 is metacentric carrying a large cluster of 5S rDNA on its L arm.     

Chromosomal changes in cell lines from mouse tumors induced by nickel sulfide and methylcholanthrene

Rhabdomyosarcomas were induced in mice by intramuscular injections of crystalline nickel sulfide and 3-methylcholanthrene. At early passage, karyotypes were performed by G-banding for four nickel sulfide cell lines and for three 3-methylcholanthrene cell lines. Six cell lines were near-diploid and one nickel sulfide line was near-tetraploid. Three of the nickel sulfide cell lines were characterized by a rearranged marker chromosome which was present in a majority of the cells of each line. The rearrangements leading to the formation of marker chromosomes were different in each nickel sulfide cell line but involved chromosome 4 in two of the nickel sulfide cell lines. Extra copies of chromosome 15 were present in two nickel sulfide cell lines. Possible rearrangement and/or gene activation was examined for the c-mos oncogene on chromosome 4 and the c-myc oncogene on chromosome 15, but no alteration or activation was observed. None of the 3-methylcholanthrene cell lines contained rearranged marker chromosomes; however, one MCA cell line did contain large numbers of double minutes. In all cell lines, minichromosomes (small atypical acrocentric chromosomes) were observed that contained distinct centromeric regions but no other G-positive bands.Abbreviations DHFR dihydrofolate reductase - MCA 3-methylcholanthrene - NS nickel sulfide     

Chromatin diminution and early cleavage in Parascaris univalens (Nematoda)

Summary In Parascaris developmental commitment to the germ line and somatic lineages is indicated by the orientation of the mitotic spindle in blastomeres, the topology of cells in the embryo, and chromatin diminution in presomatic blastomeres. Using three different experimental techniques: transient pressure treatment, application of cytochalasin B, and isolation of blastomeres, we have succeeded in uncoupling several developmental processes during cleavage of P. univalens. The following results were obtained: (1) Following mitotic nondisjunction we observed identical behavior of all chromatids in each blastomere. Thus chromosome differentiation by differential replication does not occur. (2) Chromosome fragments obtained by pressure treatment of egg cells underwent chromatin diminution. Thus this process does not require an intact germ-line chromosome. However, chromosomes immobilized on a monopolar spindle did not undergo chromatin diminution. Thus diminution appears to require segregation of chromatids. (3) Blastomeres that completely lacked chromosomes as a result of mitotic nondisjunction underwent normal early cleavage divisions. (4) Pressure treatment or prolonged treatment with cytochalasin B caused egg cells or germ line blastomeres to lose their germ line quality, as deduced from the coincident occurrence of symmetrical (presomatic-like) cleavage and chromatin diminution. (5) Isolated blastomeres from 2-cell embryos, i.e. 1/2 blastomeres, usually cleaved according to their prospective fates in the whole embryo. However, in some partial embryos derived from such blastomeres, chromatin diminution was delayed for either one or two cleavage mitoses. An activation model as an alternative to a prelocalization model is presented, which can account for early blastomere topogenesis and chromatin diminution.     

FISH analysis comparing genome organization in the domestic horse (Equus caballus) to that of the Mongolian wild horse (E. przewalskii)

Przewalski's wild horse (E. przewalskii, EPR) has a diploid chromosome number of 2n = 66 while the domestic horse (E. caballus, ECA) has a diploid chromosome number of 2n = 64. Discussions about their phylogenetic relationship and taxonomic classification have hinged on comparisons of their skeletal morphology, protein and mitochondrial DNA similarities, their ability to produce fertile hybrid offspring, and on comparison of their chromosome morphology and banding patterns. Previous studies of GTG-banded karyotypes suggested that the chromosomes of both equids were homologous and the difference in chromosome number was due to a Robertsonian event involving two pairs of acrocentric chromosomes in EPR and one pair of metacentric chromosomes in ECA (ECA5). To determine which EPR chromosomes were homologous to ECA5 and to confirm the predicted chromosome homologies based on GTG banding, we constructed a comparative gene map between ECA and EPR by FISH mapping 46 domestic horse-derived BAC clones containing genes previously mapped to ECA chromosomes. The results indicated that all ECA and EPR chromosomes were homologous as predicted by GTG banding, but provide new information in that the EPR acrocentric chromosomes EPR23 and EPR24 were shown to be homologues of the ECA metacentric chromosome ECA5.     

G-banding of germ line limited chromosomes in Acricotopus lucidus (Diptera,Chironomidae)

The germ line limited (K) chromosomes of Acricotopus lucidus (Diptera, Chironomidae) were stained for G-banding on gonial mitoses, along with the somatic (S) chromosomes. Nine different types of K chromosomes could be distinguished by the G-banding pattern and other cytological criteria. Various combinations of K chromosomes were found in the complements of different individuals and cells: some Ks were missing and others were present up to as many as five times. No two animals were completely alike in the composition of their gonial chromosome complement. Thus none of the different K types can be essential. These results are discussed in view of the complex chromosome cycle of the Orthocladiinae.     

The mobile nature of acrocentric elements illustrated by three unusual chromosome variants

Variant chromosomes are polymorphic in areas that are rich in repeat sequences such as the pericentromeric regions or in the acrocentric short arm regions. The dynamic nature of these regions is evident in the polymorphisms they exhibit. In this paper three unusual variants are described: a chromosome 21 with additional material on its short arm, a chromosome 7 with an insertion in the short arm and a chromosome 2 with satellites at the end of the long arm. All three variants were shown to involve acrocentric elements using special banding techniques and fluorescence in situ hybridization. The 21 variant was found to be a tricentric with a 21 and two 15 alpha-, two classical and three acrocentric beta-satellite signals interspersed by AgNOR-positive regions. The telomeres were present at the two terminal ends. The insertion on chromosome 7 was found to be C-band positive and to contain acrocentric beta-satellite DNA. However, acrocentric alpha-satellite, classical satellite, whole-chromosome-painting or all-telomeres sequence probes did not hybridize to the insertion. The satellited region of chromosome 2 had two C-bands, a small positive all-centromeres probe signal, and two signals for the beta-satellite probe. Sandwiched between the beta-satellite sequences was an AgNOR-positive region. The telomeres were present at the two ends of the satellited chromosome 2. Chromosome 2 subtelomeric probes hybridized to the terminal ends of the short and long arm of chromosome 2. The common thread in these three variants is the involvement of acrocentric short arm elements. The acrocentric short arm elements are shown to move to other acrocentric or nonacrocentric chromosomes and relocate to both terminal and interstitial positions. The integrations are stable and heritable. Received: 23 September 1997 / Accepted: 23 February 1998     

Normal Female Germ Cell Differentiation Requires the Female X Chromosome to Autosome Ratio and Expression of Sex-Lethal in DROSOPHILA MELANOGASTER

In somatic cells of Drosophila, the ratio of X chromosomes to autosomes (X:A ratio) determines sex and dosage compensation. The present paper addresses the question of whether germ cells also use the X:A ratio for sex determination and dosage compensation. Triploid female embryos were generated which, through the loss of an unstable ring-X chromosome, contained some germ cells of 2X;3A constitution in their ovaries. Such germ cells were shown to differentiate along one of two alternative pathways: a minority developed into normal female oocytes and eggs; the majority developed into abnormal multicellular cysts. An X:A ratio of 1 is, therefore, required in female germ cell development, at least in the mature ovary after stem cell division. Abnormal development of female germ cells was also observed when 2X;2A germ cells which were homozygous or trans-heterozygous for mutant alleles at the Sex-lethal locus were transplanted into normal female host embryos at the blastoderm stage. Germ cells homozygous for amorphic alleles failed to give rise to normal eggs. Instead, they formed multicellular cysts, very similar to those formed by 2X;3A cells. Zygotic Sxl+ activity is, therefore, also necessary for the development of normal female germ cells. No abnormalities were detected in transplanted germ cells from female embryos whose mothers had been homozygous for the mutation daughterless. When normal XY germ cells were transplanted into female embryos, no traces of such cells could be found in the adult ovary. XY germ cells seem, therefore, not to develop as far as 2X;3A or Sxl homozygous cells in a female gonad. This indicates that neither 2X;3A nor Sxl homozygous germ cells are equivalent to normal XY germ cells.     

Chromosome elimination in sciarid flies

The programmed elimination of part of the genome through chromosome loss or chromatin diminution constitutes an exceptional biological process found to be present in several diverse groups of organisms. The occurrence of this phenomenon during early embryogenesis is generally correlated to somatic versus germ-line differentiation. A most outstanding example of chromosome elimination and genomic imprinting is found in sciarid flies, where whole chromosomes of exclusive parental origin are selectively eliminated at different developmental stages. Three types of tissue-specific chromosome elimination events occur in sciarids. During early cleavages, one or two X paternal chromosomes is/are discarded from somatic cells of embryos which then develop as females or males respectively. Thus, the sex of the embryo is determined by the number of eliminated paternal X chromosomes. In germ cells, instead, a single paternal X chromosome is eliminated in embryos of both sexes. In addition, while female meiosis is orthodox, male meiosis is highly unusual as the whole paternal chromosome set is discarded from spermatocytes. As a consequence, only maternally derived chromosomes are included in the functional sperm. This paper reviews current cytological and molecular knowledge on the tissue-specific cell mechanisms evolved to achieve chromosome elimination in sciarids.     

CpG islands detected by self-primed in situ labeling (SPRINS)

We have studied the distribution and methylation of CpG islands on human chromosomes, using the novel technique of self-primed in situ labeling (SPRINS). The SPRINS technique is a hybrid of the two techniques primed in situ labeling (PRINS) and nick translation in situ. SPRINS detects chromosomal DNA breaks, as in nick translation in situ, and not annealed primers, as is the case in PRINS. We analyzed in situ-generated DNA breaks induced by the restriction enzymes HpaII and MspI. These restriction enzymes enable the detection of chromosomal CpG islands. Both HpaII- and MspI-SPRINS produce a banding pattern resembling R-banding, indicating a higher level of CpG islands in R-positive bands than in R-negative bands. Our SPRINS banding observations also indicate differences in sequence copy number in the satellites of homologous acrocentric chromosomes. Furthermore, a comparison of homologous HpaII-SPRINS-banded X chromosomes of females from lymphocyte cultures grown without methotrexate or bromodeoxyuridine revealed methylation difference between them. The same comparison of homologous X chromosomes from the cell line GM01202D, which has four X chromosomes, one active and three inactive, revealed the active X chromosome to be hypermethylated. Received: 5 February 1998; in revised form: 8 May 1998 / Accepted: 11 May 1998     

Identification of the linkage group of the Z sex chromosomes of the sand lizard (Lacerta agilis,Lacertidae) and elucidation of karyotype evolution in lacertid lizards

The sand lizard (Lacerta agilis, Lacertidae) has a chromosome number of 2n?=?38, with 17 pairs of acrocentric chromosomes, one pair of microchromosomes, a large acrocentric Z chromosome, and a micro-W chromosome. To investigate the process of karyotype evolution in L. agilis, we performed chromosome banding and fluorescent in situ hybridization for gene mapping and constructed a cytogenetic map with 86 functional genes. Chromosome banding revealed that the Z chromosome is the fifth largest chromosome. The cytogenetic map revealed homology of the L. agilis Z chromosome with chicken chromosomes 6 and 9. Comparison of the L. agilis cytogenetic map with those of four Toxicofera species with many microchromosomes (Elaphe quadrivirgata, Varanus salvator macromaculatus, Leiolepis reevesii rubritaeniata, and Anolis carolinensis) showed highly conserved linkage homology of L. agilis chromosomes (LAG) 1, 2, 3, 4, 5(Z), 7, 8, 9, and 10 with macrochromosomes and/or macrochromosome segments of the four Toxicofera species. Most of the genes located on the microchromosomes of Toxicofera were localized to LAG6, small acrocentric chromosomes (LAG11–18), and a microchromosome (LAG19) in L. agilis. These results suggest that the L. agilis karyotype resulted from frequent fusions of microchromosomes, which occurred in the ancestral karyotype of Toxicofera and led to the disappearance of microchromosomes and the appearance of many small macrochromosomes.     

Haplo-diploid locust embryos arising by accidental thelytoky in Chortoicetes terminifera investigated by G-banding

Two mosaic sibling embryos of the Australian plague locust, Chortoicetes terminifera are reported with haploid and diploid cell lines in widely differing proportions. One small chromosome pair involved in the two cases has alternative morphology and a B-chromosome is present in one. In addition, G-banding identifies two medium-sized chromosome pairs and alternative states of a second small pair. Using these markers it is clear that both diploid cell lines are homozygous for the chromosomes of the corresponding haploid line. These embryos have thus developed by accidental parthenogenesis from haploid cells, some of which were duplicated by endomitosis after development began.     

Differential staining of plant chromosomes with Giemsa

Simple Giemsa staining techniques for revealing banding patterns in somatic chromosomes of plants are described. The value of the methods in the recognition of heterochromatin was demonstrated using five monocotyledonous and two dicotyledonous species. In Trillium grandiflorum the stronger Giemsa stained chromosome segments were shown to be identical with the heterochromatic regions (H-segments) revealed by cold treatment. Preferential staining of H-segments was also observed in chromosomes from three species of Fritillaria and in Scilla sibirica. Under suitable conditions the chromosomes of Vicia faba displayed a characteristic banding pattern and the bands were identified as heterochromatin. The Giemsa techniques proved to be more sensitive than Quinacrine fluorescence in revealing a longitudinal differentiation of the chromosomes of Crepis capillaris, where plants with and without B-chromosomes were examined. Again all chromosome types had their characteristic bands but there was no difference in Giemsa staining properties between the B-chromosomes and those of the standard complement.     

The chromosomes of the nine-banded armadillo,Dasypus novemcinctus

Summary The chromosomes of the nine-banded armadillo, Dasypus novemcinctus, were studied using cultured peripheral leukocytes, tissue cells and direct preparation of male germ cells.The diploid number was found to be 64 in the blood and tissue cells, the haploid number was 32 in the testicular preparations.The autosomes can be divided into six groups, according to their size and the position of the centromere. Group A contains two pairs of large metacentrics, Groups B and C contain together 18 pairs of acrocentric chromosomes, the distinguishing feature being a gradual decrease in size. Group D is composed of six pairs of small metacentric chromosomes with almost medial centromeres. One prominentld satellited chromosome constitutes a ready marker element of this groud and of the karyotype. It is not entirely certain whether this satellitey chromosome has a homologue or not. Five pairs of small acrocentrics constitute Group E. These are almost indistinguishable from one another.Buccal smears showed a typical sex chromatin body in interphase nuclei of epithelial cells from female animals similar to that observed in some other mammals. A sex difference was also noted on examination of peripheral blood films, typical drumsticks being present on polymorphonuclear leukocytes from female armadillos.