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D M Glover

Publications and source records attributed to D M Glover.

At least 91 records · Page 5Linked to original sources
PubMed1991

Mitosis in the Drosophila embryo--in and out of control.

Increasing levels of regulation act upon mitosis as the Drosophila embryo develops. The first 13 rapid cycles in the syncytial embryo rely on maternal gene products and lack feedback regulation to monitor the completion of S phase. Such regulation is introduced together with a G2 phase in cycle 14, and the network of universal mitotic regulators comes under the overall control of string, a cdc25 homologue, whose transcription is activated within mitotic domains.

Animals↗
PubMed1991

Source apportionment with site specific source profiles.

A receptor modeling study was performed to identify and apportion the sources of PM10 mass in Granite City, Illinois, an area of historic TSP nonattainment. Samples of the ambient aerosol were collected using a dichotomous sampler. Each sample was analyzed by x-ray fluorescence and instrumental neutron activation analysis. To begin the study, a factor analysis was performed. Two different chemical mass balance (CMB) analyses were then made. The first CMB analysis used only source profiles available from the literature while the second included twelve source profiles developed from dust samples collected in Granite City. Both CMB analyses used 20 of the 33 analyzed elements since many of the source profiles in the literature did not include the other thirteen elements. The results from both sets of CMB analyses were grouped by the predominate wind direction at the site during the time each sample was taken to identify the direction of each source relative to the sampler. It was found that regional sources were the primary contributors to the fine fraction while the coarse fraction was composed of material from local industries. These sources were generally the ones identified during the Regional Air Pollution Study previously conducted in the area. However, the emission profiles from these sources were observed to have changed between the studies. It was also found that the use of the locally generated profiles greatly improved the results of the CMB analysis.

Air↗
PubMed1991

Chromosome tangling and breakage at anaphase result from mutations in lodestar, a Drosophila gene encoding a putative nucleoside triphosphate-binding protein.

We describe a Drosophila maternal-effect gene, lodestar, mutations in which cause chromatin bridges at anaphase. lodestar maps to cytological position 84D13-14, and we identified the lodestar gene in germ-line transformation experiments by the ability of a genomic fragment to restore fertility to females homozygous for lodestar mutations. lodestar encodes a potential nucleoside triphosphate binding protein, which is a novel member of the D-E-A-H box family of proteins. Antibodies raised against the lodestar gene product detect a protein that undergoes cell cycle-dependent changes in distribution in the embryo. The protein is cytoplasmic at interphase, and rapidly enters the nucleus early in prophase. It is restricted to the region enclosed by the spindle envelope during metaphase and anaphase; but by telophase, the lodestar protein is contained entirely within the reforming nucleus.

Amino Acid Sequence↗
PubMed1991

polo encodes a protein kinase homolog required for mitosis in Drosophila.

We show that mutation in polo leads to a variety of abnormal mitoses in Drosophila larval neuroblasts. These include otherwise normal looking mitotic spindles upon which chromosomes appear overcondensed; normal bipolar spindles with polyploid complements of chromosomes; bipolar spindles in which one pole can be unusually broad; and monopolar spindles. We have cloned the polo gene from a mutant allele carrying a P-element transposon and sequenced cDNAs corresponding to transcripts of the wild-type locus. The sequence shows that polo encodes a 577-amino-acid protein with an amino-terminal domain homologous to a serine-threonine protein kinase. polo transcripts are abundant in tissues and developmental stages in which there is extensive mitotic activity. The transcripts show no obvious spatial pattern of distribution in relation to the mitotic domains of cellularized embryos but are specifically concentrated in dividing cells in larval discs and brains. In the cell cycles of both syncytial and cellularized embryos, the polo kinase undergoes cell cycle-dependent changes in its distribution: It is predominantly cytoplasmic during interphase; it becomes associated with condensed chromosomes toward the end of prophase; and it remains associated with chromosomes until telophase, whereupon it becomes cytoplasmic.

Amino Acid Sequence↗
PubMed1990

Towards a physical map of the Drosophila melanogaster genome: mapping of cosmid clones within defined genomic divisions.

A physical map of the D. melanogaster genome is being constructed, in the form of overlapping cosmid clones that are assigned to specific polytene chromosome sites. A master library of ca. 20,000 cosmids is screened with probes that correspond to numbered chromosomal divisions (ca. 1% of the genome); these probes are prepared by microdissection and PCR-amplification of individual chromosomes. The 120 to 250 cosmids selected by each probe are fingerprinted by Hinfl digestion and gel electrophoresis, and overlaps are detected by computer analysis of the fingerprints, permitting us to assemble sets of contiguous clones (contigs). Selected cosmids, both from contigs and unattached, are then localized by in situ hybridization to polytene chromosomes. Crosshybridization analysis using end probes links some contigs, and hybridization to previously cloned genes relates the physical to the genetic map. This approach has been used to construct a physical map of the 3.8 megabase DNA in the three distal divisions of the x chromosome. The map is represented by 181 canonical cosmids, of which 108 clones in contigs and 32 unattached clones have been mapped individually by in situ hybridization to chromosomes. Our current database of in situ hybridization results also includes the beginning of a physical map for the rest of the genome: 162 cosmids have been assigned by in situ hybridization to 129 chromosomal subdivisions elsewhere in the genome, representing 5 to 6 megabases of additional mapped DNA.

Animals↗
PubMed1990

One of the protein phosphatase 1 isoenzymes in Drosophila is essential for mitosis.

Drosophila has four loci encoding type 1 protein serine/threonine phosphatases (PP1s). Here we describe mutations in one of these genes, at 87B on chromosome 3. Mutants die at the larval-pupal boundary with little or no imaginal cell proliferation. Neuroblasts are delayed in progress through mitosis and show defective spindle organization, abnormal sister chromatid segregation, hyperploidy, and excessive chromosome condensation. Germline transformation of mutant flies with the wild-type PP1 87B gene restores normal mitosis, viability, and fertility. These results show that PP1 activity is required for mitotic progression and that the other loci cannot supply sufficient activity to complement loss of expression of the PP1 87B gene. Alternatively, the PP1 87B product may have a distinct specialized function in mitosis.

Alleles↗
PubMed1990

The A- and B-type cyclins of Drosophila are accumulated and destroyed in temporally distinct events that define separable phases of the G2-M transition.

We show that the sequence of Drosophila cyclin B has greater identity with B-type cyclins from other animal phyla than with Drosophila cyclin A, suggesting that the two cyclins have distinct roles that have been maintained in evolution. Cyclin A is not detectable in unfertilized eggs and is present at low levels prior to cellularization of the syncytial embryo. In contrast, the levels of cyclin B remain uniformly high throughout these developmental stages. In cells within cellularized embryos and the larval brain, cyclin A accumulates to peak levels in prophase and is degraded throughout the period in which chromosomes are becoming aligned on the metaphase plate. The degradation of cyclin B, on the other hand, does not occur until the metaphase-anaphase transition. In cells arrested at c-metaphase by treating with microtubule destabilizing drugs to prevent spindle formation, cyclin A has been degraded in the arrested cells, whereas cyclin B is maintained at high levels. These observations suggest that cyclin A has a role in the G2-M transition that is independent of spindle formation, and that entry into anaphase is a key requirement for the degradation of cyclin B.

Amino Acid Sequence↗
PubMed1990

Complementation of fission yeast cdc2ts and cdc25ts mutants identifies two cell cycle genes from Drosophila: a cdc2 homologue and string.

We have exploited the universality of the molecular mechanisms that control entry into mitosis to clone the Drosophila melanogaster homologues of fission yeast Schizosaccharomyces pombe cell division control (cdc) genes by the complementation of temperature sensitive mutations. The Drosophila genes were expressed in S.pombe as cDNAs from the SP6 promoter. Successful recovery of complementing plasmids required that we first 'adapt' pooled plasmids from a Drosophila embryonic cDNA library for propagation in fission yeast by introducing an ars1-LEU2 DNA fragment into the vector. This library was introduced into S.pombe cdc2 and cdc25 mutants, and plasmids isolated carrying cDNAs that complement these mutations. The gene that encodes the Drosophila cdc2 homologue maps to a single locus in the Drosophila genome at 31E on chromosome 2. It is expressed maternally to provide mRNA in syncytial embryos, and appears to be zygotically expressed in mitotically active regions of the cellularized embryo. We have isolated two different cDNAs that complement cdc25-22. One corresponds to a transcript of string, previously described as the Drosophila homologue of cdc25, and the other to a gene that has not been previously characterized.

Amino Acid Sequence↗
PubMed1990

A neuropeptide precursor in cerebellum: proenkephalin exists in subpopulations of both neurons and astrocytes.

The adult rat cerebellum has minimal enkephalin immunoreactivity and is devoid of opiate-binding activity. Using novel monoclonal antibodies to the mammalian enkephalin precursor, we describe the immunofluorescent detection of proenkephalin, in the absence of mature enkephalin peptides, in subpopulations of rat cerebellar neurons and astrocytes. In cryostat sections, neurons that express proenkephalin include Golgi cells, macroneurons within deep cerebellar nuclei and a subpopulation of Purkinje cells. Proenkephalin messenger RNA and protein are present in subpopulations of both grey and white matter astrocytes, but not Bergmann glia. In dissociated glial culture, proenkephalin is expressed in process-bearing astrocytes, apparently in association with a subset of intermediate filaments. Proenkephalin within astrocytes is not seen until the second postnatal week and increases through to adulthood. Neuropeptide gene expression adds to the growing range of neuronal-type properties glial cells can display.

Animals↗
PubMed1990

Two distinct mechanisms localise cyclin B transcripts in syncytial Drosophila embryos.

We demonstrate that two independent mechanisms act on maternally derived cyclin B transcripts to concentrate the transcripts at the posterior pole of the Drosophila oocyte and at the cortex of the syncytial embryo. The cortical accumulation occurs because the cyclin B transcript is concentrated around nuclei and comigrates with them to the cortex. The perinuclear localisation of the transcript is blocked by inhibitors of microtubule polymerisation and the transcript colocalises with microtubular structures during the cell cycle, suggesting that the transcript is associated either directly or indirectly with microtubules. Neither microtubules nor actin filaments are required to maintain the posterior concentration of cyclin B transcripts. Instead, this seems to depend on the association of the transcripts with a component of the posterior cytoplasm. The distribution pattern of the transcript at the posterior pole throughout embryogenesis and in a variety of mutant embryos suggests that this component is associated with polar granules.

Animals↗
PubMed1990

Mutations at the asp locus of Drosophila lead to multiple free centrosomes in syncytial embryos, but restrict centrosome duplication in larval neuroblasts.

Mutations at abnormal spindle result in abnormally long and wavy microtubules in the meiotic spindles of males. Some of these spindles have a single pole and take the form of unopposed hemi-spindles. Unfertilised eggs produced by homozygous asp females may have either no nuclei, or a small number of large nuclei, consistent with there also being an effect upon female meiosis. Such eggs also display free centrosomes and independent arrays of microtubules. Embryos that have this phenotype are also present among the progeny of fertilised homozygous asp females, together with embryos that undergo varying degrees of aberrant morphogenesis, developing a variety of abnormal cuticle patterns. This latter category shows asynchronous mitoses prior to cellularisation, and has abnormal arrays of spindle microtubules. Such embryos can develop large areas that are either devoid of or have a reduced number of nuclei, in which there are centrosomes that have dissociated from the mitotic spindles. Neuroblasts in the brains of homozygous asp larvae display a high mitotic index, and have condensed chromosomes aligned as if blocked at metaphase. Immunostaining reveals that many cells contain a single centrosome connected to the metaphase chromosomes by microtubules in a hemi-spindle-like structure.

Alleles↗
PubMed1989

PCR amplification of DNA microdissected from a single polytene chromosome band: a comparison with conventional microcloning.

A novel alternative to microcloning for the production of region specific chromosomal DNA is described. In this method, 'microamplification', single bands are dissected from polytene chromosomes and digested with Sau3A. Oligonucleotide adaptors are ligated to these fragments to provide convenient priming sites for polymerase chain reaction amplification. In this way, as much as 1 microgram of DNA can be amplified from a single band. Probes made from PCR amplified DNA from two such dissections have been used to probe cloned DNA form a 100 kb chromosome walk. Whereas conventional microcloning has generated cloned EcoRI fragments corresponding to 3-4 kb of the walk, the PCR probes cover greater than 90% of this chromosomal region. Thus microamplification is significantly more effective than microcloning in providing probes for establishing chromosomal walks.

Animals↗
PubMed1989

Cloning and chromosomal localization of Drosophila cDNA encoding the catalytic subunit of protein phosphatase 1 alpha. High conservation between mammalian and insect sequences.

A 1.2-kb clone containing the full coding sequence of a protein phosphatase 1 catalytic subunit has been isolated from a Drosophila head cDNA library. It encodes a polypeptide of 302 amino acids with a molecular mass of 34.5 kDa. The predicted protein sequence is 92% identical (94% similar) to rabbit protein phosphatase 1 alpha (PP-1 alpha) demonstrating strict conservation of the phosphatase catalytic subunit over a considerable evolutionary distance. Abundant 1.6-kb and 2.5-kb mRNA transcripts were detected throughout Drosophila development. The clone hybridised to four sites on Drosophila salivary gland polytene chromosomes. The major site is at 87B6-12 on the right arm of chromosome 3. In addition, there are three secondary sites, one on the same chromosome at 96A2-5 and two on the X chromosome at 9C1-2 and 13C1-2. Isolation of a further cDNA clone, hybridising to 9C1-2 and encoding part of the catalytic subunit 88% similar to Drosophila PP-1 alpha, proves the existence of at least two transcriptionally active genes for protein phosphatase 1.

Amino Acid Sequence↗
PubMed1989

Centrosomes, and not nuclei, initiate pole cell formation in Drosophila embryos.

An injection of aphidicolin into early Drosophila embryos inhibits DNA synthesis and nuclear division, while centrosome replication and many other aspects of the mitotic cycle continue. If aphidicolin is injected at nuclear cycle 7-8, the normal migration of nuclei to the embryo cortex is completely inhibited. In most of these embryos, however, centrosomes continue to migrate in a coordinated manner to the cortex, where they reorganize tubulin, actin, and the overlying plasma membrane. Remarkably, the centrosomes that migrate to the posterior pole of such embryos initiate pole cell formation in the absence of nuclei. These observations demonstrate that centrosomes alone are able to direct a major reorganization of the cortical cytoskeleton when they arrive at the surface of the embryo. They also suggest that the coordinated movement of nuclei to the embryo cortex is mediated by forces acting on the centrosome rather than on the nucleus itself.

Actins↗
PubMed1989

The promoters and spacers in the rDNAs of the melanogaster species subgroup of Drosophila.

The spacer sequences of rDNAs of members of the melanogaster species subgroup of Drosophila (melanogaster, simulans, mauritiana, teissieri, and yakuba) have been compared. The external transcribed spacers (ETSs; the region encoding the 5' end of the primary transcript, upstream from the 18S sequences) are highly conserved between in D. melanogaster, D. simulans and D. mauritiana, whereas the more distantly related D. yakuba and D. teissieri differ in having apparent deletions of 22 and 27 bp, respectively, in this region. The divergence of nucleotide sequence upstream from the transcription start points is consistent with the established phylogeny of the five species. The sequences between bp positions -47 and +24 from the primary transcription start point show extremely little variation between each species. This is also the case for sequences between the approximate bp positions -140 to -125 and -85 to -70. This could indicate a functional importance not only of the sequences next to the transcription start point, but also of these upstream regions. An array of 240-bp repeats can be found at a comparable distance upstream from the transcription start point in each species. Matrix homology comparisons indicate that for each species not only is the sequence at the primary transcription start point duplicated within the 240-bp repeats as previously reported for D. melanogaster, but that this is part of a longer interrupted duplication which includes a region of strong similarity with the sequence between the approximate positions -105 to -65. This region is contained within one of the regions upstream from the transcription start point that is strongly conserved between the species. This sequence may therefore have functional significance not only for the transcription of the rRNA precursor, but also for transcription of the so-called NTS sequences which is now known to occur. The 240-bp arrays are themselves highly conserved within a species indicating that homogenisation mechanisms are operative. The divergence of these arrays between species is consistent with the phylogenetic tree. The 3' sequences of the primary transcription unit, now known to be RNA-processing sites, are also highly similar between the species. Immediately downstream from these sites there is little homology between the rDNA of the different species, until 95-bp tandem arrays are reached in each case.

Animals↗