Drosophila Telomere Transposons: Genetically Active Elements in Heterochromatin

In Drosophilatwo non-LTR retrotransposons, HeT-Aand TART, offer a novel experimental system for the study of heterochromatin. These elements, found only in heterochromatin, form Drosophilatelomeres by repeated transposition onto chromosome ends. Their transposition yields arrays of repeats larger and more irregular than the repeats produced by telomeras; nevertheless, the transpositions are, in principle, equivalent to the telomere-building action of telomerase. The identification of the HeT-Apromoter has given the first view of the molecular structure of a promoter active in heterochromatin. These telomere-specific elements are unusual in having a large amount of non-coding sequence. Like many other heterochromatic sequences, the HeT-Anon-coding sequence has a repetitive organization strongly conserved within the species, although the sequence itself can undergo significant change between species (atypical example of concerted evolution). Such heterochromatic sequences could be important for the cell, perhaps as docking stations for essential proteins. This revised version was published online in July 2006 with corrections to the Cover Date.     

Immunolcocalization of actin in intact and DNA—and histone—depleted nuclei and chromosomes of allium cepa

The presence of actin in eukaryotic nuclei and chromosomes,and especially in higher plant nuclei and chromosomes,has not been well established.We detected actin in meristematic cells of Allium cepa with indirect immunofluorescence technique and observed bright fluorescence in the intact nuclei and chromosomes,indicating that actin is present in the nuclei and chromosomes of the higher plant.We labeld sections of the meristematic cells of A.cepa with immunogold technique,gold parti cles were concentrated in condensed chromatin and nucleoli,confirming the results of the immunofluoresence observations.We traeated the nuclei and chromosomes of A.cepa with DNase I and 2M NaCl and obtained DNA-and histone-depleted nuclei and chromosomes.Indirect immunofluorescence tests showed that the DNA-and histonedepleted nuclei and chromosomes reacted positively with the anti-actin antibodies.These results demonstrate that the anti-actin antibodies.These results demonstrate that actin exists not only in intact nuclei and chromosomes,but also in DNA-and histone-depleted nuclei and chrmosomes of the plant.In addition,our immuno-fluorescence tests indicate that tropomyosin is present in the nuclei and chromosomes of A.cepa.     

Chromatin structure during the prereplicative phases in the life cycle of mammalian cells

The object of this study was to determine the kinetics of chromosome decondensation during the G₁ period of the HeLa cell cycle. HeLa cells synchronized in the G₁ period following the reversal of mitotic block were fused with Colcemid-arrested mitotic HeLa cells at 1.5, 3, 5, and 7 h after the reversal of N₂O block. The resulting prematurely condensed chromosomes (PCC) were classified into six categories depending on the degree of their condensation. The frequency of occurrence of each category was plotted as a function of time after mitosis. The results of this study indicate that the process of chromosome decondensation, initiated during the telophase of mitosis continues throughout the G₁ period without any interruption, thus the chromatin reaches an ultimate state of decondensation by the end of G₁ period, when DNA synthesis is initiated.     

Cytogenetics of the Anopheles gambiae complex in Sudan, with special reference to An. arabiensis: relationships with East and West African populations

The species composition of malaria vector mosquitoes belonging to the Anopheles gambiae complex (Diptera: Culicidae) from >40 localities in Sudan, representing most ecological situations, was determined by analysis of ovarian polytene chromosomes. Of 2162 females, 93% were identified as An. arabiensis Patton and 7% were An. gambiae Giles sensu stricto. No hybrids were found between the two species. Anopheles arabiensis occurred in all but two sites, whereas An. gambiae s.s. was effectively limited to the southernmost, more humid localities. For chromosomal paracentric inversions, the degree of polymorphism was low in An. gambiae s.s. (inversions 2La, 2Rb and 2Rd), higher in An. arabiensis (inversions Xe, 2Ra, b, bc, d1, s; 3Ra, d). Anopheles gambiae samples from Sudan were all apparently panmictic, i.e. they did not show restricted gene flow such as observed among West African populations (interpreted as incipient speciation). Chromosomal inversion patterns of An. gambiae in southern Sudan showed characteristics of intergrading Savanna/Forest populations similar to those observed in comparable eco-climatic situations of West Africa. Anopheles arabiensis was polymorphic for inversion systems recorded in West Africa (2Ra, 2Rb, 2Rdl, 3Ra) and for a novel 2Rs polymorphism, overlapping with inversion systems 2Rb and 2Rd1. Samples carrying the 2Rs inversion were mostly from Khashm-el-Girba area in central-eastern Sudan. In the great majority of the samples all polymorphic inversions were found to be in Hardy-Weinberg equilibrium. Sudan populations of An. arabiensis should therefore be considered as generally panmictic. Anopheles arabiensis shows more inversion polymorphism in west than in east African populations. Sudan populations have more evident similarities with those from westwards than those from eastwards of the Great Rift Valley. The possible influence of the Rift on evolution of An. arabiensis is discussed.     

Characterizations of the murine mesenchymal cell line expressing GFP

We established and characterized a murine mesenchymal stem cell line from the bone marrow of a transgenic C57BL mouse that ubiquitously expressed green fluorescent protein (GFP). Immunostaining revealed the presence of several markers common for mesenchymal stem cells (MSCs). The cells expressed specific fibroblast proteins, such as smooth muscle actin, which is localized in stress fibrils, and vimentin, a major protein of intermediate filaments in connective tissue cells. These proteins are responsible for the ability to differentiate into adipocytes or osteoblasts under appropriate conditions. The MSC karyotype was unstable. At the 6th passage cells, were aneuploid and genetically heterogeneous. The number of chromosomes ranged from near 2n to 8n. 80% of cells had chromosome numbers between 50 and 85 without a well-defined modal class. Differential G-staining of metaphase spreads showed variability in the copy numbers of individual chromosomes and presence of random chromosome rearrangements, such as ectopic associations of nonhomologous chromosomes. All cells analyzed contained a single dicentric marker chromosome. Some cells also had mini-chromosomes regarded as indicators of gene amplification. We suppose that the karyotypic instability of MSCs that express GFP is provoked by the insertion of foreign GFP transgenes into the murine genome. These cells could be useful for the study of genomic alterations during the spontaneous oncogenic transformation of stem cells.     

Synthetic biology and metabolic engineering of actinomycetes for natural product discovery

Actinomycetes are one of the most valuable sources of natural products with industrial and medicinal importance. After more than half a century of exploitation, it has become increasingly challenging to find novel natural products with useful properties as the same known compounds are often repeatedly re-discovered when using traditional approaches. Modern genome mining approaches have led to the discovery of new biosynthetic gene clusters, thus indicating that actinomycetes still harbor a huge unexploited potential to produce novel natural products. In recent years, innovative synthetic biology and metabolic engineering tools have greatly accelerated the discovery of new natural products and the engineering of actinomycetes. In the first part of this review, we outline the successful application of metabolic engineering to optimize natural product production, focusing on the use of multi-omics data, genome-scale metabolic models, rational approaches to balance precursor pools, and the engineering of regulatory genes and regulatory elements. In the second part, we summarize the recent advances of synthetic biology for actinomycetal metabolic engineering including cluster assembly, cloning and expression, CRISPR/Cas9 technologies, and chassis strain development for natural product overproduction and discovery. Finally, we describe new advances in reprogramming biosynthetic pathways through polyketide synthase and non-ribosomal peptide synthetase engineering. These new developments are expected to revitalize discovery and development of new natural products with medicinal and other industrial applications.     

Nonrandom Representation of Sex-Biased Genes on Chicken Z Chromosome

Several lines of evidence suggest that the X chromosome of various animal species has an unusual complement of genes with sex-biased or sex-specific expression. However, the study of the X chromosome gene content in different organisms provided conflicting results. The most striking contrast concerns the male-biased genes, which were reported to be almost depleted from the X chromosome in Drosophila but overrepresented on the X chromosome in mammals. To elucidate the reason for these discrepancies, we analysed the gene content of the Z chromosome in chicken. Our analysis of the publicly available expressed sequence tags (EST) data and genome draft sequence revealed a significant underrepresentation of ovary-specific genes on the chicken Z chromosome. For the brain-expressed genes, we found a significant enrichment of male-biased genes but an indication of underrepresentation of female-biased genes on the Z chromosome. This is the first report on the nonrandom gene content in a homogametic sex chromosome of a species with heterogametic female individuals. Further comparison of gene contents of the independently evolved X and Z sex chromosomes may offer new insight into the evolutionary processes leading to the nonrandom genomic distribution of sex-biased and sex-specific genes. Electronic Supplementary Material Electronic Supplementary material is available for this article at and accessible for authorised users. [Reviewing Editor: Dr. Manyuan Long]     

An alternative to radiation hybrid mapping for large-scale genome analysis in barley

The presence of a monosomic gametocidal chromosome (GC) in a barley chromosome addition line of common wheat generates structural aberrations in the barley chromosome as well as in the wheat chromosomes of gametes lacking the GC. A collection of structurally aberrant barley chromosomes is analogous to a panel of radiation hybrid (RH) mapping and is valuable for high-throughput physical mapping. We developed 90 common wheat lines (GC lines) containing aberrant barley 7H chromosomes induced by a gametocidal chromosome, 2C. DNAs isolated from these GC lines provided a panel of 7H chromosomal fragments in a wheat genetic background, comparable with RH mapping panels in mammals. We used this 7H GC panel and the methodology for RH mapping to physically map PCR-based barley markers, SSRs and AFLPs, onto chromosome 7H, relying on polymorphism between the 7H chromosome and the wheat genome. We call this method GC mapping. This study describes a novel adaptation and combination of methods of inducing chromosomal rearrangements to produce physical maps of markers. The advantages of the presented method are similar to RH mapping in that non-polymorphic markers can be used and the mapping panels can be relatively easily obtained. In addition, mapping results are cumulative when using the same mapping set with new markers. The GC lines will be available from the National Bioresources Project-KOMUGI (). Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.