Cytoplasmic protrusions in insect cells during mitosis in vitro.
Explore the source record for details and available documents.
Animals↗
SEARCH · Search PubMed
Results for “Chromosomes, Insect”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The culture of cells from insects and ticks. I. Cultivation of dipteran cells in vitro.
Explore the source record for details and available documents.
Animals↗
Analysis of cells from established insect cell lines. I. Introduction.
Explore the source record for details and available documents.
Animals↗
Evolution of Antennapedia-class homeobox genes.
Antennapedia (Antp)-class homeobox genes are involved in the determination of pattern formation along the anterior-posterior axis of the animal embryo. A phylogenetic analysis of Antp-class homeodomains of the nematode, Drosophila, amphioxus, mouse, and human indicates that the 13 cognate group genes of this gene family can be divided into two major groups, i.e., groups I and II. Group I genes can further be divided into subgroups A (cognate groups 1-2), B (cognate group 3), and C (cognate groups 4-8), and group II genes can be divided into subgroups D (cognate groups 9-10) and E (cognate groups 11-13), though this classification is somewhat ambiguous. Evolutionary distances among different amino acid sequences suggest that the divergence between group I and group II genes occurred approximately 1000 million years (MY) ago, and the five different subgroups were formed by approximately 600 MY ago, probably before the divergence of Pseudocoelomates (e.g., nematodes) and Coelomates (e.g., insects and chordates). Our results show that the genes that are phylogenetically close are also closely located in the chromosome, suggesting that the colinearity between the gene expression and gene arrangement was generated by successive tandem gene duplications and that the gene arrangement has been maintained by some sort of selection.
Animals↗
Accumulation of transposable elements in the heterochromatin and on the Y chromosome of Drosophila simulans and Drosophila melanogaster.
The elements of the transposon families G, copia, mdg 1, 412, and gypsy that are located in the heterochromatin and on the Y chromosome have been identified by the Southern blotting technique in Drosophila simulans and D. melanogaster populations. Within species, the abundance of such elements differs between transposon families. Between species, the abundance in the heterochromatin and on the Y chromosome of the elements of the same family can differ greatly suggesting that differences within a species are unrelated to structural features of elements. By shedding some new light on the mechanism of accumulation of transposable elements in the heterochromatin, these data appear relevant to the understanding of the long-term interaction between transposable elements and the host genome.
Animals↗
Sequence-specific targeting of MSL complex regulates transcription of the roX RNA genes.
In Drosophila, dosage compensation is controlled by the male-specific lethal (MSL) complex consisting of at least five proteins and two noncoding RNAs, roX1 and roX2. The roX RNAs function in targeting MSL complex to the X chromosome, and roX transgenes can nucleate spreading of the MSL complex into flanking chromatin when inserted on an autosome. An MSL-binding site (DHS, DNaseI hypersensitive site) has been identified in each roX gene. Here, we investigate the functions of the DHS using transgenic deletion analyses and reporter assays. We find that MSL interaction with the DHS counteracts constitutive repression at roX1, resulting in male-specific expression of roX1 RNA. Surprisingly, the DHS is not required for initiation of cis spreading of MSL complex, instead local transcription of roX RNAs correlates with extensive spreading.
Animals↗
Genetically determined asynapsis, spermatogenic degeneration, and infertility in men.
We report a family in which azoospermia and infertility affected two sibs whose parents were first cousins once removed. Meiotic cells of the proband, who had the chromosomal complement of a normal male (46,XY), exhibited asynapsis, defective synaptonemal complex (SC) formation, chiasma failure, and degeneration of prophase spermatocytes with asynapsis. Based on these observations, we suggest that the meiotic abnormalities and infertility in this family comprise a trait with an autosomal recessive mode of inheritance. Review of published cases of infertile men with normal chromosomal complements and disturbed meiosis suggests that genetically determined asynapsis and desynapsis similar to that established in plant and insect species also occur in humans. In humans, asynapsis appears to be inherited as an autosomal recessive. The mode of inheritance of desynapsis is not clear; X-linked recessive or autosomal dominant has been suggested in one family. Studies by us and by others reported in the literature suggest that the mode of action of genes that affect synapsis and cause a reduction in the numbers of visible chiasmata at diakinesis is dissimilar to that of the action of genes that cause defective meiotic recombination, defective repair of induced damage to DNA in somatic cells, and chromosome instability.
Adult↗
A novel cDNA from Drosophila encoding a protein with similarity to mammalian cysteine-rich secretory proteins, wasp venom antigen 5, and plant group 1 pathogenesis-related proteins.
The CAP protein family is made up of a group of secreted proteins that share sequence similarity. Members of this family are found in animals, plants, and fungi, and their shared sequence similarity suggests that members share a common, but as yet unknown, molecular function. As a first step in defining the function of CAP family proteins, an 878 bp partial cDNA encoding a novel member of the CAP family was cloned by the polymerase chain reaction (PCR) from total RNA of adult Drosophila. The cDNA contained the complete coding sequence for a protein 256 amino acids in length, as well as the complete 3' untranslated region (UTR) and a portion of the 5' UTR. The protein, named Antigen 5-related (Agr), was most similar in sequence to antigen 5 (Ag5), a CAP family member found in social wasps and ants. The corresponding Agr RNA is about 1 kb in length and is present at all stages of development, with highest levels observed in adults. Agr RNA is transcribed from a single gene that is located within region 12F of the X chromosome. The identification of Agr in Drosophila expands the number of known CAP family members to well over four dozen. Further studies of Agr and the gene which encodes this protein using the Drosophila model system may help provide important insight into the molecular functioning of this little known, but increasingly significant protein family.
Amino Acid Sequence↗
Chromosomal localization of a highly repeated EcoRI DNA fragment in Megoura viciae (Homoptera, Aphididae) by nick translation and fluorescence in situ hybridization.
To investigate the genome of the aphid Megoura viciae at molecular level, we have studied total DNA by agarose gel electrophoresis after cleavage with different restriction endonucleases. EcoRI digestion produced a highly repeated DNA fragment, about 600 pb long. The contribution of this EcoRI element to the total genome of M. viciae was estimated at about 6% by means of densitometric scanning of agarose gel photographs. The chromosomal localization of this fragment, investigated by fluorescent in situ hybridization (FISH), constantly showed one large and two narrower fluorescent bands located on the X chromosome, all corresponding to C-positive heterochromatic areas. These results are in full accordance with the data obtained by in situ nick translation experiments carried out after EcoRI digestion, and clearly demonstrate that a substantial amount of M. viciae heterochromatin consists of EcoRI fragments which are mainly located on the X chromosome. Using the EcoRI restriction fragment as a molecular probe may be a practical tool for the investigation of taxonomic and evolutionary relationships in this group of insects.
Animals↗
Spontaneous excision of BAC vector sequences from bacmid-derived baculovirus expression vectors upon passage in insect cells.
Repeated baculovirus infections in cultured insect cells lead to the generation of defective interfering viruses (DIs), which accumulate at the expense of the intact helper virus and compromise heterologous protein expression. In particular, Autographa californica multicapsid nucleopolyhedovirus (AcMNPV) DIs are enriched in an origin of viral DNA replication (ori) not associated with the homologous regions (hrs). This non-hr ori is located within the coding sequence of the non-essential p94 gene. We investigated the effect of a deletion of the AcMNPV non-hr ori on the heterologous protein expression levels following serial passage in Sf21 insect cells. Using homologous ET recombination in E. coli, deletions within the p94 gene were made in a bacterial artificial chromosome (BAC) containing the entire AcMNPV genome (bacmid). All bacmids were equipped with an expression cassette containing the green fluorescent protein gene and a gene encoding the classical swine fever virus E2 glycoprotein (CSFV-E2). For the parental (intact) bacmid only, a strong accumulation of DIs with reiterated non-hr oris was observed. This was not observed for the mutants, indicating that removal of the non-hr ori enhanced the genetic stability of the viral genome upon passaging. However, for all passaged viruses it was found that the entire BAC vector including the expression cassette was spontaneously deleted from the viral genome, leading to a rapid decrease in GFP and CSFV-E2 production. The rationale for the (intrinsic) genetic instability of the BAC vector in insect cells and the implications with respect to large-scale production of proteins with bacmid-derived baculoviruses are discussed.
Animals↗
Extraordinary number of gene rearrangements in the mitochondrial genomes of lice (Phthiraptera: Insecta).
The arrangement of genes in the mitochondrial (mt) genomes of most insects is the same, or near-identical, to that inferred to be ancestral for insects. We sequenced the entire mt genome of the small pigeon louse, Campanulotes bidentatus compar, and part of the mt genomes of nine other species of lice. These species were from six families and the three main suborders of the order Phthiraptera. There was no variation in gene arrangement among species within a family but there was much variation in gene arrangement among the three suborders of lice. There has been an extraordinary number of gene rearrangements in the mitochondrial genomes of lice!
Animals↗
Genetic mosaic analysis of the equatorial-less mutation in Drosophila melanogaster.
eql (equatorial-less) is a recessive lethal mutation on the second chromosome of Drosophila melanogaster. J. Campos-Ortega found that eql clones in somatic mosaic flies have reduced numbers of photoreceptor cells, and he suggested that only the R1, R6, and R7 photoreceptor cells were missing in this mutant. These photoreceptor cells help to define the inverted orientation of ommatidial facets along the equatorial midline of the fly eye, hence the mutation was named "equatorial-less." We have conducted a detailed analysis of the eql mutation, by serial section reconstruction of eql clones marked with bw- or w- in somatic mosaic flies. We found that all photoreceptor cell types (R1-R8) could be deleted by the eql mutation, and in rare cases the number of photoreceptor cells was increased. The apparent lack of photoreceptor cell type specificity was confirmed by our analysis of genetically mosaic facets, which indicated that no single photoreceptor cell, or subset of photoreceptor cells, was uniquely required to express eql+. Rather, eql appears to function in all photoreceptor cells, and possibly in all eye precursor cells. The distribution of photoreceptor cell numbers in w eql facets was consistent with the hypothesis that each photoreceptor cell was deleted independently of the others. The eql gene is located on the right arm of chromosome 2 at map location 2-104.5 +/- 0.7 and lies between the polytene chromosome bands 59D8 and 60A7.
Animals↗
mgl-1, a mouse homologue of the Drosophila tumor-suppressor gene l(2)gl, maps to chromosome 11.
Explore the source record for details and available documents.
Animals↗
Chorion gene amplification in Drosophila: A model for metazoan origins of DNA replication and S-phase control.
The mechanisms controlling duplication of the metazoan genome are only beginning to be understood. It is still unclear what organization of DNA sequences constitutes a chromosomal origin of DNA replication, and the regulation of origin activity during the cell cycle has not been fully revealed. We review recent results that indicate that chorion gene amplification in follicle cells of the Drosophila ovary is a model for investigating metazoan replication. Evaluation of cis sequence organization and function suggests that chorion loci share attributes with other replicons and provides insights into metazoan origin structure. Moreover, recent results indicate that chorion origins respond to S-phase control, but escape mechanisms that inhibit other origins from firing more than once in a cell cycle. Several identified genes that mediate amplification are critical for the cell cycle control of replication initiation. It is likely that further genetic screens for mutations that disrupt amplification will identify the cadre of proteins associated with origins and the regulatory pathways that control their activity. Furthermore, the recent development of methods to detect amplification in situ has uncovered new aspects of its developmental control. Examining this control will reveal links between developmental pathways and the cell cycle machinery. Visualization of amplifying chorion genes with high resolution also represents an opportunity to evaluate the influence of nuclear and chromosome structure on origin activity. The study of chorion amplification in Drosophila, therefore, provides great potential for the genetic and molecular dissection of metazoan replication.
Animals↗
Sister chromatid exchanges in mammalian meiotic chromosomes.
Meiotic cells have been, and remain, a relatively difficult tissue in which to study SCEs. Experimental evaluations have had to contend with various problems unique to germ cells, i.e., poor in vitro growth, unusual cytotoxicities (from BrdUrd), trying chromosome morphologies, and confusion between chromosome label patterns generated by SCEs, COs, and replication kinetics. Nevertheless, BrdUrd differential staining techniques in insects and rodents have progressed to the point where SCE frequencies can be reliably determined. In the described Armenian hamster system, SCEs may be directly resolved in selected primary spermatocyte bivalents and indirectly assessed in secondary spermatocyte cells. SCE frequencies determined from spermatogonial, primary spermatocyte, and secondary spermatocyte cells are in good agreement. The system should be applicable for studies of possible mechanistic similarities between SCE and CO exchange, and for evaluating genotoxic effects. Experimental evidence in Drosophila (33) argues against a very close molecular relationship between these forms of breakage and recombination. However, it is likely that new information can be gained from cells in which normal SCE and CO frequencies and distributions can be characterized, and from studies of the consequences to these events after various mutagenic perturbations to premeiotic and meiotic DNA.
Animals↗
Molecular analysis of cubitus interruptus (ci) mutations suggests an explanation for the unusual ci position effects.
The cubitus interruptus (ci) locus of Drosophila melanogaster is located proximally on chromosome 4. In ci mutants cubital wing veins are interrupted or absent. We have cloned this locus using a gypsy element associated with the ci1 mutation. Analysis of all extant ci mutations reveals that they contain conspicuous molecular alterations within a 13.7 kb region. Of the four homozygous viable mutations, three (ci1, ci361, ciw) have single insertions, while one (ci57g) has a small deletion, all located within a more restricted 1 kb region. The dominant mutations, ciD and Ce2 each contain two insertions within the 13.7 kb region. All these molecular alterations are located upstream of a transcript previously associated with the ciD mutation and thought to derive from a segment polarity gene. We induced revertants of the dominant ci phenotype (wing vein interruption) in ciD and found molecular alterations in this transcript (the ci+ transcript) in two revertant alleles, thereby demonstrating this transcript's involvement in the ci phenotype. The locations of the molecular alterations, together with the results of the ciD reversion experiment, provide a connection between the dominant and recessive ci mutations and argue that all are likely to be alleles of the same complex locus, ci, not two separate loci as previously proposed. The ci phenotype of dominant and recessive mutations can be explained by inappropriate expression of the ci+ transcript in the posterior wing compartment where the cubital vein is affected, while loss of ci+ function generates recessive lethality. Lack of repression of ci+ transcription, through a pairing-dependent, trans-acting silencer element, can explain the unusual position effects associated with ci (the Dubinin effect).
Animals↗
POPULATION CYTOLOGY OF BRITISH GRASSHOPPERS. I. CHIASMA VARIATION IN CHORTHIPPUS BRUNNEUS, CHORTHIPPUS PARALLELUS AND OMOCESTUS VIRIDULUS.
Explore the source record for details and available documents.
Animals↗
Multiplication of 28S rDNA and NOR activity in chromosome evolution among ants of the Myrmecia pilosula species complex.
Chromosomal localization of rDNA in samples of five taxa of the Mymecia pilosula species complex (Hymenoptera: Formicidae: Myrmeciinae) with 2n = 3 (M. croslandi), 8 (M. imaii), 10 (M. banksi), 18 (M. haskinsorum), and 27 (M. pilosula) was carried out by fluorescence in situ hybridization (FISH) using cloned M. croslandi rDNA (pMc.r2) including the coding region for 28S rRNA. Results show that (1) the 28S rDNA in the genome of these ants is repetitive and is localized in pericentromeric C-bands, (2) the number of chromosomes carrying rDNA is two in M. croslandi, M. imaii and M. banksi, six in M. haskinsorum and ten in M. pilosula, and (3) only one or two clusters of rRNA genes generate nucleoli in each species. We suggest that the rDNA in the ancestral stock of the M. pilosula complex was localized originally in a pericentromeric C-band, and multiplied by chance with time during saltatory increases in C-banding following episodes of centric fission. Most rDNA multiplied on various chromosomes seems to be inactivated and eliminated from the genome, together with C-bands, by AM-inversion or centric fusion, with the remnant rDNAs dispersed in the genome by centric fission and AM-inversion.
Animals↗