Showing papers on "Polytene chromosome published in 2015"
TL;DR: A convergence of molecular analysis with direct observation thus reveals the architecture of interphase chromosomes and establishes the conservation of TADs between polytene and diploid cells of Drosophila.
129 citations
TL;DR: It is proposed that Scm is a key mediator connecting PRC1, PRC2, and transcriptional silencing, and combined with previous structural and genetic analyses, this results strongly suggest thatScm coordinates PcG complexes and polymerizes to produce broad domains of Pcg silencing.
Abstract: The Polycomb group (PcG) proteins are key regulators of development in Drosophila and are strongly implicated in human health and disease. How PcG complexes form repressive chromatin domains remains unclear. Using cross-linked affinity purifications of BioTAP-Polycomb (Pc) or BioTAP-Enhancer of zeste [E(z)], we captured all PcG-repressive complex 1 (PRC1) or PRC2 core components and Sex comb on midleg (Scm) as the only protein strongly enriched with both complexes. Although previously not linked to PRC2, we confirmed direct binding of Scm and PRC2 using recombinant protein expression and colocalization of Scm with PRC1, PRC2, and H3K27me3 in embryos and cultured cells using ChIP-seq (chromatin immunoprecipitation [ChIP] combined with deep sequencing). Furthermore, we found that RNAi knockdown of Scm and overexpression of the dominant-negative Scm-SAM (sterile α motif) domain both affected the binding pattern of E(z) on polytene chromosomes. Aberrant localization of the Scm-SAM domain in long contiguous regions on polytene chromosomes revealed its independent ability to spread on chromatin, consistent with its previously described ability to oligomerize in vitro. Pull-downs of BioTAP-Scm captured PRC1 and PRC2 and additional repressive complexes, including PhoRC, LINT, and CtBP. We propose that Scm is a key mediator connecting PRC1, PRC2, and transcriptional silencing. Combined with previous structural and genetic analyses, our results strongly suggest that Scm coordinates PcG complexes and polymerizes to produce broad domains of PcG silencing.
72 citations
TL;DR: The data show that Y degeneration proceeds quickly after sex chromosomes become established through genomic and epigenetic changes, and are consistent with the idea that the evolution of sex-linked chromatin is influenced by its ancestral configuration.
Abstract: Sex chromosomes evolve distinctive types of chromatin from a pair of ancestral autosomes that are usually euchromatic. In Drosophila, the dosage-compensated X becomes enriched for hyperactive chromatin in males (mediated by H4K16ac), while the Y chromosome acquires silencing heterochromatin (enriched for H3K9me2/3). Drosophila autosomes are typically mostly euchromatic but the small dot chromosome has evolved a heterochromatin-like milieu (enriched for H3K9me2/3) that permits the normal expression of dot-linked genes, but which is different from typical pericentric heterochromatin. In Drosophila busckii, the dot chromosomes have fused to the ancestral sex chromosomes, creating a pair of ‘neo-sex’ chromosomes. Here we collect genomic, transcriptomic and epigenomic data from D. busckii, to investigate the evolutionary trajectory of sex chromosomes from a largely heterochromatic ancestor. We show that the neo-sex chromosomes formed <1 million years ago, but nearly 60% of neo-Y linked genes have already become non-functional. Expression levels are generally lower for the neo-Y alleles relative to their neo-X homologs, and the silencing heterochromatin mark H3K9me2, but not H3K9me3, is significantly enriched on silenced neo-Y genes. Despite rampant neo-Y degeneration, we find that the neo-X is deficient for the canonical histone modification mark of dosage compensation (H4K16ac), relative to autosomes or the compensated ancestral X chromosome, possibly reflecting constraints imposed on evolving hyperactive chromatin in an originally heterochromatic environment. Yet, neo-X genes are transcriptionally more active in males, relative to females, suggesting the evolution of incipient dosage compensation on the neo-X. Our data show that Y degeneration proceeds quickly after sex chromosomes become established through genomic and epigenetic changes, and are consistent with the idea that the evolution of sex-linked chromatin is influenced by its ancestral configuration.
38 citations
TL;DR: It is shown that Cap-H2 localizes to interband regions on polytene chromosomes and co-localizes with Mrg15 at regions of active transcription across the genome, consistent with a model in whichMrg15 acts as a loading factor to facilitate Cap- H2 binding to chromatin and mediate changes in chromatin organization.
Abstract: The spatial organization of the genome within the eukaryotic nucleus is a dynamic process that plays a central role in cellular processes such as gene expression, DNA replication, and chromosome segregation. Condensins are conserved multi-subunit protein complexes that contribute to chromosome organization by regulating chromosome compaction and homolog pairing. Previous work in our laboratory has shown that the Cap-H2 subunit of condensin II physically and genetically interacts with the Drosophila homolog of human MORF4-related gene on chromosome 15 (MRG15). Like Cap-H2, Mrg15 is required for interphase chromosome compaction and homolog pairing. However, the mechanism by which Mrg15 and Cap-H2 cooperate to maintain interphase chromatin organization remains unclear. Here, we show that Cap-H2 localizes to interband regions on polytene chromosomes and co-localizes with Mrg15 at regions of active transcription across the genome. We show that co-localization of Cap-H2 on polytene chromosomes is partially dependent on Mrg15. We have identified a binding motif within Cap-H2 that is essential for its interaction with Mrg15, and have found that mutation of this motif results in loss of localization of Cap-H2 on polytene chromosomes and results in partial suppression of Cap-H2-mediated compaction and homolog unpairing. Our data are consistent with a model in which Mrg15 acts as a loading factor to facilitate Cap-H2 binding to chromatin and mediate changes in chromatin organization.
19 citations
TL;DR: A high‐quality photomap of the polytene chromosomes from ovarian nurse cells of An.
Abstract: Anopheles atroparvus (Diptera: Culicidae) is one of the main malaria vectors of the Maculipennis group in Europe. Cytogenetic analysis based on salivary gland chromosomes has been used in taxonomic and population genetic studies of mosquitoes from this group. However, a high-resolution cytogenetic map that could be used in physical genome mapping in An. atroparvus is still lacking. In the present study, a high-quality photomap of the polytene chromosomes from ovarian nurse cells of An. atroparvus was developed. Using fluorescent in situ hybridization, 10 genes from the five largest genomic supercontigs on the polytene chromosome were localized and 28% of the genome was anchored to the cytogenetic map. The study established chromosome arm homology between An. atroparvus and the major African malaria vector Anopheles gambiae, suggesting a whole-arm translocation between autosomes of these two species. The standard photomap constructed for ovarian nurse cell chromosomes of An. atroparvus will be useful for routine physical mapping. This map will assist in the development of a fine-scale chromosome-based genome assembly for this species and will also facilitate comparative and evolutionary genomics studies in the genus Anopheles.
18 citations
TL;DR: It is demonstrated that, even after the larval salivary glands have completed what is perceived to be one of their major biological functions – glue secretion during pupariation – they remain dynamic and physiologically active up until the execution phase of PCD.
Abstract: A central function of the Drosophila salivary glands (SGs), historically known for their polytene chromosomes, is to produce and then release during pupariation the secretory glue used to affix a newly formed puparium to a substrate. This essential event in the life history of Drosophila is regulated by the steroid hormone ecdysone in the late-larval period. Ecdysone triggers a cascade of sequential gene activation that leads to glue secretion and initiates the developmentally-regulated programmed cell death (PCD) of the larval salivary glands, which culminates 16 h after puparium formation (APF). We demonstrate here that, even after the larval salivary glands have completed what is perceived to be one of their major biological functions – glue secretion during pupariation – they remain dynamic and physiologically active up until the execution phase of PCD. We have used specific metabolic inhibitors and genetic tools, including mutations or transgenes for shi, Rab5, Rab11, vha55, vha68-2, vha36-1, syx1A, syx4, and Vps35 to characterize the dramatic series of cellular changes occurring in the SG cells between pupariation and 7–8 h APF. Early in the prepupal period, they are remarkably active in endocytosis, forming acidic vacuoles. Midway through the prepupal period, there is abundant late endosomal trafficking and vacuole growth, which is followed later by vacuole neutralization and disappearance via membrane consolidation. This work provides new insights into the function of Drosophila SGs during the early- to mid-prepupal period.
16 citations
TL;DR: This study provided the first detailed description, nomenclature, and idiograms for the mitotic chromosomes of Cx.
Abstract: The genome assembly of southern house mosquito Cx. quinquefasciatus is represented by a high number of supercontigs with no order or orientation on the chromosomes. Although cytogenetic maps for the polytene chromosomes of this mosquito have been developed, their utilization for the genome mapping remains difficult because of the low number of high-quality spreads in chromosome preparations. Therefore, a simple and robust mitotic-chromosome-based approach for the genome mapping of Cx. quinquefasciatus still needs to be developed. In this study, we performed physical mapping of 37 genomic supercontigs using fluorescent in situ hybridization on mitotic chromosomes from imaginal discs of 4th instar larvae. The genetic linkage map nomenclature was adopted for the chromosome numbering based on the direct positioning of 58 markers that were previously genetically mapped. The smallest, largest, and intermediate chromosomes were numbered as 1, 2, and 3, respectively. For idiogram development, we analyzed and described in detail the morphology and proportions of the mitotic chromosomes. Chromosomes were subdivided into 19 divisions and 72 bands of four different intensities. These idiograms were used for mapping the genomic supercontigs/genetic markers. We also determined the presence of length polymorphism in the q arm of sex-determining chromosome 1 in Cx. quinquefasciatus related to the size of ribosomal locus. Our physical mapping and previous genetic linkage mapping resulted in the chromosomal assignment of 13% of the total genome assembly to the chromosome bands. We provided the first detailed description, nomenclature, and idiograms for the mitotic chromosomes of Cx. quinquefasciatus. Further application of the approach developed in this study will help to improve the quality of the southern house mosquito genome.
16 citations
TL;DR: The in situ proximity ligation assay (PLA) provides a sensitive means to determine whether proteins and other factors have bound to chromosomes in close proximity to each other, and thus may interact and corroborate proposed interactions of the MSL complex with both CLAMP and TopoII.
Abstract: In Drosophila, the male-specific lethal (MSL) complex specifically targets the male X chromosome and participates in a twofold increase in expression output leading to functional dosage compensation. The complex includes five proteins and two non-coding RNAs (ncRNAs). A number of additional associated factors have also been identified. However, the components' roles and interactions have not been fully elucidated. The in situ proximity ligation assay (PLA) provides a sensitive means to determine whether proteins and other factors have bound to chromosomes in close proximity to each other, and thus may interact. Thus, we modified, tested, and applied the assay to probe interactions of MSL complex components on polytene chromosomes. We show that in situ PLA can detect and map both protein-protein and protein-ncRNA interactions on polytene chromosomes at high resolution. We further show that all five protein components of the MSL complex are in close proximity to each other, and the ncRNAs roX1 and roX2 bind the complex in close proximity to MLE. Our results also indicate that JIL1, a histone H3 Ser10 kinase enriched on the male X chromosome, interacts with MSL1 and MSL2, but not MSL3 of the MSL complex. In addition, we corroborate proposed interactions of the MSL complex with both CLAMP and TopoII.
11 citations
TL;DR: Potential mechanisms by which replication fork inhibition can be achieved and the consequences this has on genome stability and copy number control are discussed.
Abstract: There are many layers of regulation governing DNA replication to ensure that genetic information is accurately transmitted from mother cell to daughter cell. While much of the control occurs at the level of origin selection and firing, less is known about how replication fork progression is controlled throughout the genome. In Drosophila polytene cells, specific regions of the genome become repressed for DNA replication, resulting in underreplication and decreased copy number. Importantly, underreplicated domains share properties with common fragile sites. The Suppressor of Underreplication protein SUUR is essential for this repression. Recent work established that SUUR functions by directly inhibiting replication fork progression, raising several interesting questions as to how replication fork progression and stability can be modulated within targeted regions of the genome. Here we discuss potential mechanisms by which replication fork inhibition can be achieved and the consequences this has on genome stability and copy number control.
11 citations
TL;DR: A whole chromosome probe was generated from a specific heterochromatic B chromosome occurring in cells of the characidae fish Moenkhausia sanctaefilomenae, suggesting a possible intra-specific origin of these B chromosomes.
Abstract: B chromosomes are dispensable genomic elements found in different groups of animals and plants. In the present study, a whole chromosome probe was generated from a specific heterochromatic B chromosome occurring in cells of the characidae fish Moenkhausia sanctaefilomenae (Steindachner, 1907). The chromosome painting probes were used in fluorescence in situ hybridization (FISH) experiments for the assessment of metaphase chromosomes obtained from individuals from three populations of Moenkhausia sanctaefilomenae. The results revealed that DNA sequences were shared between a specific B chromosome and many chromosomes of the A complement in all populations analyzed, suggesting a possible intra-specific origin of these B chromosomes. However, no hybridization signals were observed in other B chromosomes found in the same individuals, implying a possible independent origin of B chromosome variants in this species. FISH experiments using 18S rDNA probes revealed the presence of non-active ribosomal genes in some B chromosomes and in some chromosomes of the A complement, suggesting that at least two types of B chromosomes had an independent origin. The role of heterochromatic segments and ribosomal sequences in the origin of B chromosomes were discussed.
9 citations
TL;DR: It is shown that, similar to achiasmate chromosomes, heterologous chromosomes can be connected by chromatin threads, suggesting a mechanism for how heterochromatic homology establishes these unusual biorientation patterns.
Abstract: One essential role of the first meiotic division is to reduce chromosome number by half. Although this is normally accomplished by segregating homologous chromosomes from each other, it is possible for a genome to have one or more chromosomes that lack a homolog (such as compound chromosomes), or have chromosomes with multiple potential homologs (such as in XXY females). These configurations complete meiosis but engage in unusual segregation patterns. In Drosophila melanogaster females carrying two compound chromosomes, the compounds can accurately segregate from each other, a process known as heterologous segregation. Similarly, in XXY females, when the X chromosomes fail to cross over, they often undergo secondary nondisjunction, where both Xs segregate away from the Y. Although both of these processes have been known for decades, the orientation mechanisms involved are poorly understood. Taking advantage of the recent discovery of chromosome congression in female meiosis I, we have examined a number of different aberrant chromosome configurations. We show that these genotypes complete congression normally, with their chromosomes bioriented at metaphase I arrest at the same rates that they segregate, indicating that orientation must be established during prometaphase I before congression. We also show that monovalent chromosomes can move out on the prometaphase I spindle, but the dot 4 chromosomes appear required for this movement. Finally, we show that, similar to achiasmate chromosomes, heterologous chromosomes can be connected by chromatin threads, suggesting a mechanism for how heterochromatic homology establishes these unusual biorientation patterns.
TL;DR: Targeting of Suppressor of Under-Replication and HP1GAL4DBD results in delayed replication of appropriate euchromatic regions and underreplication at these regions starts early, much like in the absence of the fusion proteins; however, replication completion is significantly delayed.
Abstract: We analyze how artificial targeting of Suppressor of Under-Replication (SUUR) and HP1 proteins affects DNA replication in the “open,” euchromatic regions. Normally these regions replicate early in the S phase and display no binding of either SUUR or HP1. These proteins were expressed as fusions with DNA-binding domain of GAL4 and recruited to multimerized UAS integrated in three euchromatic sites of the polytene X chromosome: 3B, 8D, and 18B. Using PCNA staining as a marker of ongoing replication, we showed that targeting of SUURGAL4DBD and HP1GAL4DBD results in delayed replication of appropriate euchromatic regions. Specifically, replication at these regions starts early, much like in the absence of the fusion proteins; however, replication completion is significantly delayed. Notably, delayed replication was insufficient to induce underreplication. Recruitment of SUURGAL4DBD and HP1GAL4DBD had distinct effects on expression of a mini-white reporter, found near UAS. Whereas SUURGAL4DBD had no measurable influence on mini-white expression, HP1GAL4DBD targeting silenced mini-white, even in the absence of functional SU(VAR)3-9. Furthermore, recruitment of SUURGAL4DBD and HP1GAL4DBD had distinct effects on the protein composition of target regions. HP1GAL4DBD but not SUURGAL4DBD could displace an open chromatin marker, CHRIZ, from the tethering sites.
01 Jul 2015
TL;DR: In this article, the Suppressor of Underreplication protein (SUUR) is used to inhibit replication fork progression in Drosophila polytene cells, resulting in underreplication and decreased copy number.
Abstract: There are many layers of regulation governing DNA replication to ensure that genetic information is accurately transmitted from mother cell to daughter cell. While much of the control occurs at the level of origin selection and firing, less is known about how replication fork progression is controlled throughout the genome. In Drosophila polytene cells, specific regions of the genome become repressed for DNA replication, resulting in underreplication and decreased copy number. Importantly, underreplicated domains share properties with common fragile sites. The Suppressor of Underreplication protein SUUR is essential for this repression. Recent work established that SUUR functions by directly inhibiting replication fork progression, raising several interesting questions as to how replication fork progression and stability can be modulated within targeted regions of the genome. Here we discuss potential mechanisms by which replication fork inhibition can be achieved and the consequences this has on genome stability and copy number control.
TL;DR: It is shown that the region responsible for X-chromosome attachment interacts with nuclear lamina stronger in nurse cells, then in salivary glands cells in Anopheles messeae Fall, and in follicle epithelium cells in imaginal disсs cells in 3D-FISH experiments.
Abstract: Spatial organization of a chromosome in a nucleus is very important in biology but many aspects of it are still generally unresolved. We focused on tissue-specific features of chromosome architecture in closely related malaria mosquitoes, which have essential inter-specific differences in polytene chromosome attachments in nurse cells. We showed that the region responsible for X-chromosome attachment interacts with nuclear lamina stronger in nurse cells, then in salivary glands cells in Anopheles messeae Fall. The inter-tissue differences were demonstrated more convincingly in an experiment of two distinct chromosomes interposition in the nucleus space of cells from four tissues. Microdissected DNA-probes from nurse cells X-chromosome (2BC) and 3R chromosomes (32D) attachment regions were hybridized with intact nuclei of nurse cells, salivary gland cells, follicle epithelium cells and imaginal disсs cells in 3D-FISH experiments. We showed that only salivary gland cells and follicle epithelium cells have no statistical differences in the interposition of 2BC and 32D. Generally, the X-chromosome and 3R chromosome are located closer to each other in cells of the somatic system in comparison with nurse cells on average. The imaginal disсs cell nuclei have an intermediate arrangement of chromosome interposition, similar to other somatic cells and nurse cells. In spite of species-specific chromosome attachments there are no differences in interposition of nurse cells chromosomes in An. messeae and An. atroparvus Thiel. Nurse cells have an unusual chromosome arrangement without a chromocenter, which could be due to the special mission of generative system cells in ontogenesis and evolution.
TL;DR: A new standard cytogenetic photomap of the polytene chromosomes for C. quinquefasciatus can serve as a reference for studying other vector species of C. pipiens complex and will help to resolve their taxonomic relationships.
Abstract: Background
Southern house mosquito Culex quinquefasciatus belongs to the C. pipiens cryptic species complex, with global distribution and unclear taxonomy. Mosquitoes of the complex can transmit human and animal pathogens, such as filarial worm, West Nile virus and avian malarial Plasmodium. Physical gene mapping is crucial to understanding genome organization, function, and systematic relationships of cryptic species, and is a basis for developing new vector control strategies. However, physical mapping was not established previously for Culex due to the lack of well-structured polytene chromosomes.
TL;DR: The examination of its transcriptional activity demonstrated the presence of at least one intact active copy in the genome, showing a differential level of expression between sexes as well as during embryonic development.
Abstract: Sex chromosomes have many unusual features relative to autosomes. The in depth exploration of their structure will improve our understanding of their origin and divergence (degeneration) as well as the evolution of genetic sex determination pathways which, most often are attributed to them. In Tephritids, the structure of Y chromosome, where the male-determining factor M is localized, is largely unexplored and limited data concerning its sequence content and evolution are available. In order to get insight into the structure and organization of the Y chromosome of the major olive insect pest, the olive fly Bactrocera oleae, we characterized sequences from a Pulse Field Gel Electrophoresis (PFGE)-isolated Y chromosome. Here, we report the discovery of the first olive fly LTR retrotransposon with increased presence on the Y chromosome. The element belongs to the BEL-Pao superfamily, however, its sequence comparison with the other members of the superfamily suggests that it constitutes a new family that we termed Achilles. Its ~7.5 kb sequence consists of the 5’LTR, the 5’non-coding sequence and the open reading frame (ORF), which encodes the polyprotein Gag-Pol. In situ hybridization to the B. oleae polytene chromosomes showed that Achilles is distributed in discrete bands dispersed on all five autosomes, in all centromeric regions and in the granular heterochromatic network corresponding to the mitotic sex chromosomes. The between sexes comparison revealed a variation in Achilles copy number, with male flies possessing 5–10 copies more than female (CI range: 18–38 and 12–33 copies respectively per genome). The examination of its transcriptional activity demonstrated the presence of at least one intact active copy in the genome, showing a differential level of expression between sexes as well as during embryonic development. The higher expression was detected in male germline tissues (testes). Moreover, the presence of Achilles-like elements in different species of the Tephritidae family suggests an ancient origin of this element.
TL;DR: Findings show that chromosome arms IIL and IIR correspond to Muller elements B and C, respectively, directly contrasting the current homology assignments in D. willistoni and constituting a major reassignment of the scaffolds to chromosome II arms.
Abstract: Drosophila willistoni is a geographically widespread Neotropical species. The genome of strain Gd-H4-1 from Guadeloupe Island (Caribbean) was sequenced in 2007 as part of the 12 Drosophila Genomes Project. The assembled scaffolds were joined based on conserved linkage and assigned to polytene chromosomes based on a handful of genetic and physical markers. This paucity of markers was particularly striking in the metacentric chromosome II, comprised two similarly sized arms, IIL and IIR, traditionally considered homologous to Muller elements C and B, respectively. In this paper we present the cytological mapping of 22 new gene markers to increase the number of markers mapped by in situ hybridization and to test the assignment of scaffolds to the polytene chromosome II arms. For this purpose, we generated, by polymerase chain reaction amplification, one or two gene probes from each scaffold assigned to the chromosome II arms and mapped these probes to the Gd-H4-1 strain’s polytene chromosomes by nonfluorescent in situ hybridization. Our findings show that chromosome arms IIL and IIR correspond to Muller elements B and C, respectively, directly contrasting the current homology assignments in D. willistoni and constituting a major reassignment of the scaffolds to chromosome II arms.
01 Jan 2015
TL;DR: The alterations found in D. melanogaster were caused by joint action of the components of each and changed in the cycle, in phenotype, in the behavior of individuals in each stage and fragmentation in the polytene chromosomes.
Abstract: Drosophila melanogaster o fruit fl y is considered an organims of great importance in genetics and developmental biology to present a short life cycle that facilitates the advancement of various tests and trials. Objective: Evaluate the effect of disinfectants in reproductive rate in D. melanogaster. Methodology: culture media were performed in normal and experimental dilutions: 1:2 (treatment 1), 1:10 (treatment 2) and 75 microliters spraying (treatment 3), with three repetitions were evaluated until the fourth generation , salivary gland assemblies for identifi cation of polytene chromosomes were made and the data obtained by analysis of variance with multifactorial ANOVA were analyzed. Results: reduction was found in the survival rate (IS), changes in the cycle, in phenotype, in the behavior of individuals in each stage and fragmentation in the polytene chromosomes. The most signifi cant changes were observed in treatment 1 showed a confi dence level of 95% (P <0.05). Conclusion: The alterations found in D. melanogaster were caused by joint action of the components of each
TL;DR: It is reported that SUUR protein, an established marker of late replication in salivary gland polytene chromosomes, does not always colocalize with late-replicating regions in nurse cells, and chromosome 4 may represent a special domain of the genome, as it replicates on its own schedule which is uncoupled from the rest of the chromosomes.
Abstract: Drosophila cell lines are used extensively to study replication timing, yet data about DNA replication in larval and adult tissues are extremely limited. To address this gap, we traced DNA replication in polytene chromosomes from nurse cells of Drosophila melanogaster otu mutants using bromodeoxyuridine incorporation. Importantly, nurse cells are of female germline origin, unlike the classical larval salivary glands, that are somatic. In contrast to salivary gland polytene chromosomes, where replication begins simultaneously across all puffs and interbands, replication in nurse cells is first observed at several specific chromosomal regions. For instance, in the chromosome 2L, these include the regions 31B-E and 37E and proximal parts of 34B and 35B, with the rest of the decondensed chromosomal regions joining replication process a little later. We observed that replication timing of pericentric heterochromatin in nurse cells was shifted from late S phase to early and mid stages. Curiously, chromosome 4 may represent a special domain of the genome, as it replicates on its own schedule which is uncoupled from the rest of the chromosomes. Finally, we report that SUUR protein, an established marker of late replication in salivary gland polytene chromosomes, does not always colocalize with late-replicating regions in nurse cells.
TL;DR: Important differences were found in the band sequences of polytene chromosomes, and in the number and the arrangement of active regions between the two populations, raising the possibility that the Malawian population could constitute a distinct new species of anhydrobiotic chironomid.
Abstract: The African chironomid Polypedilum vanderplanki Hinton, 1951 is the only chironomid able to withstand almost complete desiccation in an ametabolic state known as anhydrobiosis. The karyotypes of two allopatric populations of this anhydrobiotic chironomid, one from Nigeria and another from Malawi, were described according to the polytene giant chromosomes. The karyotype from the Nigerian population was presented as the reference chromosome map for Polypedilum vanderplanki. Both populations, Nigerian and Malawian, showed the same number of chromosomes (2n=8), but important differences were found in the band sequences of polytene chromosomes, and in the number and the arrangement of active regions between the two populations. Such important differences raise the possibility that the Malawian population could constitute a distinct new species of anhydrobiotic chironomid.
19 Feb 2015
TL;DR: Two distinct groups were found among the specimens of C. striatipennis indicated cryptic diversity in this species that needs further examination, consistent with phylogenetic analysis that revealed that all three species formed monophyletic clades with strong support.
Abstract: The larvae of the family Chironomidae are important components of freshwater ecosystems. However, taxonomic knowledge of these insects is poorly developed in Thailand. In this study we examined multiple character sets for species identifi cation of the larval stage of three Chironomid species, Chironomus striatipennis, C. javanus and Kiefferulus tainanus. Specimens were collected from Maha Sarakham and Roi Et Province, Thailand.The morphological characters of these species agreed with previously published descriptions from other geographic regions. Cytological examinations revealed that C. striatipennis has four polytene chromosomes with the arm combinations of AE, CD, BF and G. The nucleolar organizer and Balbiani Ring were located on the chromosome arm G. C. javanus has four polytene chromosomes, but arm combinations could not be determined due to the poor quality of the chromosomes except for arm G. K. tinanus has four chromosomes,and chromosome arm G was connected to chromosome E. DNA barcoding based on mitochondrial cytochrome c oxidase subunit I (COI) sequences perfectly differentiated these species. The results are consistent with phylogenetic analysis that revealed that all three species formed monophyletic clades with strong support. However, two distinct groups were found among the specimens of C. striatipennis indicated cryptic diversity in this species that needs further examination.
TL;DR: The morphology and diagnostic characters for all life stages except the egg are given, and the polytene chromosomes are compared with those of other members of the Simulium (Nevermannia) vernum group.
Abstract: Simulium (Nevermannia) berchtesgadense nov. spec. is described from the Alps of southeastern Germany. The morphology and diagnostic characters for all life stages except the egg are given, and the polytene chromosomes are compared with those of other members of the Simulium (Nevermannia) vernum group. The species is chromosomally similar to Simulium (Nevermannia) cryophilum cytoform 'A' but differs morphologically in each life stage. Bionomic information and the associated simuliid fauna are presented.
TL;DR: The study of variability of polytene chromosomes of Chironomids in water with different factors of pollution is given in the article and the influence of mobile elements and repetitive DNA sequences on genome instability is explained.
Abstract: The study of variability of polytene chromosomes of Chironomids in water with different factors of pollution is given in the article. Special attention is drawn towards the reaction of Chironomid genome affected by radiation of Chernobyl region and heavy metals. Two types of reorganizations are discussed: inherited chromosomes, transmitted from year to year, from population to population, and somatic rare chromosomes covering small regions and influencing the duration of life of one generation. In polytene chromosomes, there are unique transcribing structures: nucleolar organizer (NOR) and Balbiani rings (BRs), which are significant for cell functioning. Functional alternations of these structures affected by radiation and chemical pollution are considered. The influence of mobile elements and repetitive DNA sequences on genome instability is explained. The genome alteration of a population can be considered adaptive, since it was necessary for species preservation during pollution.
TL;DR: It is shown that MESR4 is a nuclear protein essential for embryonic development and a novel chromatin‐binding protein required for proper expression of genes including those regulated by the EGFR signaling pathway during development.
Abstract: Misexpression Suppressor of Ras 4 (MESR4), a plant homeodomain (PHD) finger protein with nine zinc-finger motifs has been implicated in various biological processes including the regulation of fat storage and innate immunity in Drosophila. However, the role of MESR4 in the context of development remains unclear. Here it is shown that MESR4 is a nuclear protein essential for embryonic development. Immunostaining of polytene chromosomes using anti-MESR4 antibody revealed that MESR4 binds to numerous bands along the chromosome arms. The most intense signal was detected at the 39E-F region, which is known to contain the histone gene cluster. P-element insertions in the MESR4 locus, which were homozygous lethal during embryogenesis with defects in ventral ectoderm formation and head encapsulation was identified. In the mutant embryos, expression of Fasciclin 3 (Fas3), an EGFR signal target gene was greatly reduced, and the level of EGFR signal-dependent double phosphorylated ERK (dp-ERK) remained low. However, in the context of wing vein formation, genetic interaction experiments suggested that MESR4 is involved in the EGFR signaling as a negative regulator. These results suggested that MESR4 is a novel chromatin-binding protein required for proper expression of genes including those regulated by the EGFR signaling pathway during development. genesis 53:701-708, 2015. © 2015 Wiley Periodicals, Inc.
TL;DR: Based upon the detailed chromosome map of polytene chromosomes of the eurybiont species Endochironomus albipennis Meigen, 1830, the localization of the centromere regions using a C-banding technique is defined.
Abstract: Based upon the detailed chromosome map of polytene chromosomes of the eurybiont species Endochironomus albipennis Meigen, 1830, the localization of the centromere regions using a C-banding technique is defined. Chromosomal polymorphism in populations from two water bodies in the Volga region has been studied, 17 sequences are described. Polytene chromosomes of Endochironomus sp. (2n=6), having larvae morphologically similar to those of Endochironomus albipennis Meigen, 1830 (2n=6) are described for the first time.
TL;DR: The species-specific organization of the constitutive heterochromatin can be used as an additional cytogenetic marker for species differentiation.
Abstract: The constitutive heterochromatin of two homosequential sibling species, Chironomus riparius and Chironomus piger, was studied The salivary gland chromosomes of both species were analyzed using three staining methods: orcein and C band staining combined with DAPI and CMA3 fluorochrome staining Both species have the chromosome set 2n = 8, with the same banding pattern and chromosome arm combinations: AB, CD, EF, G, but they differed in number and distribution of heterochromatic bands, AT-rich sequences (DAPI+) and GC-rich sequences (CMA3+) In the polytene chromosomes of C piger, C-bands were found in centromeres only They contain two types of repetitive DNA sequences: DAPI+ (very weak) and CMA3+ sequences However, the polytene chromosomes of C riparius have many interstitial heterochromatic bands in addition to the centromeric heterochromatin Some of these bands contain both AT-rich and GC-rich sequences, while others are either AT-rich (DAPI+) or GC-rich (CMA3+) Therefore, these closely related species differ both in the content and localization of constitutive heterochromatin The species-specific organization of the constitutive heterochromatin can be used as an additional cytogenetic marker for species differentiation
TL;DR: The frequency of contacts of centromere and telomere regions of polytene chromosomes in the karyotype of a midge Prodiamesa olivacea has been analyzed and the fact of non-random frequency ofCentromere regions contacts has been confirmed by statistical methods.
Abstract: The frequency of contacts of centromere and telomere regions of polytene chromosomes in the karyotype of a midge Prodiamesa olivacea has been analyzed. The fact of non-random frequency of centromere regions contacts has been confirmed by statistical methods. These data are consistent with the diploid number of chromosomes equal to 10. The species has been announced as a “transitional form”, evolving towards reduction of the chromosome number.
01 Jan 2015
TL;DR: It is proposed that the role of roX RNAs is to prevent the binding of the MSL-complex to heterochromatin and the sequence analysis showed that in the absence of ro X RNAs, the MSl-complex has an affinity for regions enriched in Hoppel transposable elements and repeats in general.
Abstract: Long non-coding RNAs contribute to dosage compensation in both mammals and Drosophila by inducing changes in the chromatin structure of the X-chromosome In Drosophila melanogaster, roX1 and roX2 are long non-coding RNAs that together with proteins form the male-specific lethal (MSL) complex, which coats the entire male X-chromosome and mediates dosage compensation by increasing its transcriptional output Studies on polytene chromosomes have demonstrated that when both roX1 and roX2 are absent, the MSL-complex becomes less abundant on the male X-chromosome and is relocated to the chromocenter and the 4thchromosome Here we address the role of roX RNAs in MSL-complex targeting and the evolution of dosage compensation in Drosophila We performed ChIP-seq experiments which showed that MSL-complex recruitment to high affinity sites (HAS) on the X-chromosome is independent of roX and that the HAS sequence motif is conserved in D simulans Additionally, a complete and enzymatically active MSL-complex is recruited to six specific genes on the 4thchromosome Interestingly, our sequence analysis showed that in the absence of roX RNAs, the MSL-complex has an affinity for regions enriched in Hoppel transposable elements and repeats in general We hypothesize that roX mutants reveal the ancient targeting of the MSL-complex and propose that the role of roX RNAs is to prevent the binding of the MSL-complex to heterochromatin
TL;DR: The advances in the study of Drosophila salivary gland chromosome are reviewed, and an attempt is made to systematically and effectively introduce this model system into genetics teaching practice in order to steer and inspire students' interest in genetics.
Abstract: Drosophila salivary gland polytene chromosome, one of the three classical chromosomes with remarkable characteristics, has been used as an outstanding model for a variety of genetic studies since 1934. The greatest contribution of this model to genetics has been providing extraordinary angle of view in studying interphase chromosome structure and gene expression regulation. Additionally, it has been extensively used to understand some special genetic phenomena, such as dosage compensation and position-effect variegation. In this paper, we briefly review the advances in the study of Drosophila salivary gland chromosome, and try to systematically and effectively introduce this model system into genetics teaching practice in order to steer and inspire students' interest in genetics.