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Chromosomes are intricately folded and packaged in the cell nucleus and interact with the nuclear envelope. This complex nuclear architecture has a profound effect on how the genome works and how the cells function. The main goal of review is to highlight recent studies on the effect of chromosome-nuclear envelope interactions on chromatin folding and function in the nucleus. The data obtained suggest that chromosome-nuclear envelope attachments are important for the organization of nuclear architecture in various organisms. A combination of experimental cell biology methods with computational modeling offers a unique opportunity to explore the fundamental relationships between different aspects of 3D genome organization in greater details. This powerful interdisciplinary approach could reveal how the organization and function of the genome in the nuclear space is affected by the chromosome-nuclear envelope attachments and will enable the development of novel approaches to regulate gene expression.

Infestation of bee colonies and apiaries by representatives of the genus Nosema, microsporidian protozoans of European honeybees (Apis mellifera L.), causing nosemosis, in Tomsk Province was investigated. In 2012—2015, nosemosis was detected in 32 out of 124 honeybee colonies (31.3 %) and in 20 out of 64 studied apiaries (25.8 %). The maximal infestation rate of bee colonies and apiaries constituted more than 40 % in 2014—2015. N. apis pathogen was registered in 84.4 % of infected bee colonies (16 apiaries); N. ceranae was identified in 9.4 % of infected bee colonies (2 apiaries); and co-infection (N. apis and N. ceranae) was detected in 6.3 % of infected bee colonies (2 apiaries). The reasons of the spreading of the nosemosis, such as climatic conditions, control of imported bee colonies on the presence of Nosema infection, and some others are discussed.

Malaria mosquitoes often belong to complexes of sibling species, members of which are morphologically and genetically similar to each other. However, members within these complexes can vary significantly in their ecological adaptations and abilities to transmit the malaria parasite. The high degree of genetics similarity among sibling species makes the reconstruction of phylogenetic relationships within species complexes difficult. This paper reviews studies that infer the ancestral--descendant relationships among sibling species using molecular markers and chromosomal inversions. A methodology based on analyzing breakpoints of fixed overlapping inversions is shown to be useful for rooting phylogenies in complexes of sibling species, if the chromosomal arrangements in outgroup species are known. The construction of detailed phylogenies for malaria vectors will help to identify the association of evolutionary genomic changes with the origin of human blood choice and specific ecological adaptations.

Mosquito-borne diseases cause significant problems for the human health. For this reason, the genomes of three most dangerous species of mosquitoes, including the yellow fever mosquito Aedes aegypti, were sequenced in last decade. The efficient vector of arboviruses. Ae. aegypti, is also a convenient model for laboratory research. The intensive genetic mapping of morphological and molecular markers conducted for this mosquito in the past was very successful. This mapping was also used as a tool to localize a number of quantitative trait loci related to the mosquito's ability to transmit various pathogens. However, physical mapping of the Ae. aegypti genome is difficult due to the lack of high-quality polytene chromosomes. Here, we review different mapping approaches that help improving genome sequence assembly and also integrate linkage, chromocome and genome maps the yellow fever mosquito.

The African malaria mosquito Anopheles gambiae was the first disease vector chosen for genome sequencing. Although its genome assembly has been facilitated by physical mapping, large gaps still pose a serious problem for accurate annotation and genome analysis. The majority of the gaps are located in regions of pericentromeric and intercalary heterochromatin. Genomic analysis has identified protein-coding genes and various classes of repetitive elements in the Anopheles heterochromatin. Molecular and cytogenetic studies have demonstrated that heterochromatin is a structurally heterogeneous and rapidly evolving part of the malaria mosquito genome.

The genomic era offers excellent opportunities to improve our understanding of the genetic basis of mosquito adaptation, evolution, and competence to a pathogen. The availability of polytene chromosomes in anopheline mosquitoes makes them an excellent model system for studying genome organization, evolution, and function. Physical mapping facilitated the whole genome sequence assembly for the major malaria vector Anopheles gambiae and comparative genome mapping has determined types, patterns, and rates of chromosomal rearrangements in mosquito evolution. Together with sequencing projects, high-resolution physical mapping can shed light on mechanisms of chromosomal rearrangements and phylogenetic relationships among species.

Distribution of eight fragments of conserved repetitive DNA from pericentromeric heterochromatin of chromosome 2 of Anopheles atroparvus has been investigated by in situ hybridization on polytene chromosomes of An. atroparvus and An. messeae. We have shown that heterochromatic regions of all chromosomes both in An. atroparvus and An. messeae vary in combinations of, at least, conserved repeats. Some repeats have been found only in pericentromeric heterochromatic regions of chromosomes 2 (clones Atr2R-46a, Atr2R-73, Atr2R-85a in An. atroparvus and Atr2R-25 in An. messeae). Others have been found in two (clones Atr2R-25a and Atr2R-90 in An. atroparvus, Atr2R-25a in An. messeae) and more (clones Atr2R-118, Atr2R-136 in An. atroparvus, Atr2R-73 in An. messeae) pericentromeric heterochromatic regions of chromosomes. DNA comparison of pericentromeric heterochromatic regions of chromosomes in species of the "Anopheles maculipennis" complex is species- and chromosome-specific, due, in particular, to different maintenance of conserved repeates.

Nuclei of ovarian pseudonurse cells from the mutant strain of Drosophila melanogaster otu 11 are suitable for mapping the attachment of chromosomes to the nuclear envelope (NE). Loci in contact with the NE included region 20CD of the X chromosome, region 41 of chromosome 2, the proximal end of region 81 of chromosome 3, and region 101 of chromosome 4. In situ hybridization revealed that all 4 regions contained sequences homologous to clone lambda20p1.4. DNA of clone lambda20p1.4 was previously found to bind specifically to purified D. melanogaster lamins. These results suggest that specific DNA sequences are involved in attachment of chromosomes to NE in vivo.

A combined approach based on cytological observations in situ hybridization, and qualitative Southern-blot analyses were used to localize the proximal border of the right arm of polytene chromosome 2 in Drosophila melanogaster otu 11 strain. A genetically functional chromosome 2 is bounded by "deletions" C', C, D, B, A and ms2-10. Using in situ hybridization in conjunction with comparative quantitative Southern-blot hybridization to deletions in centromeric heterochromatin, DNA of specific centromeric clone lambda20p1.4 was localized with respect to "deletions" and on otu 11 polytene chromosomes. Comparison of hybridization sites of lambda20p1.4 on polytene chromosomes, and its amount in mutant lines of D. melanogaster carrying known "deletions" in the centromeric heterochromatin enabled us to localize the proximal border of the right arm of chromosome 2 in D. melanogaster otu 11 strain between the 39/40 region and hybridization site of the k20p1.4 DNA fragment.

Chromosome localization of sequences homologous to lambda 20p1.4 of the Drosophila melanogaster nuclear lamina DNA (nlDNA) was established by in situ hybridization in species of the melanogaster subgroup. DNA of the lambda 20p1.4 clone was shown to be located in the chromocenter in all the species examined. Laboratory strains of D. simulans, D. mauritiana, and D. sechellia exhibited interspecific differences in localization of lambda 20p1.4 nlDNA on chromosome arms. In eight natural populations, intraspecific polymorphism of lambda 20p1.4 nlDNA chromosome localization was shown to be present in D. simulans but absent in D. melanogaster. The possible participation of transposable elements in nlDNA relocation is discussed.

Anopheles funestus Giles is one of the major malaria vectors in Africa, but little is known about its genetics. Lack of a cytogenetic map characterized by regions has hindered the progress of genetic research with this important species. This study developed a cytogenetic map of An. funestus using ovarian nurse cell polytene chromosomes. We demonstrate an important application with the cytogenetic map for characterizing various chromosomal inversions for specimens collected from coastal Kenya. The linear and spatial organization of An. funestus polytene chromosomes was compared with the best-studied malaria mosquito, An. gambiae Giles. Comparisons of chromosome morphology between the two species have revealed that the most extensive chromosomal rearrangement occurs in pericentromeric heterochromatin of autosomes. Differences in pericentromeric heterochromatin types correlate with nuclear organization differences between An. funestus and An. gambiae. Attachments of chromosomes to the nuclear envelope strongly depend on the presence of diffusive beta-heterochromatin. Thus, An. funestus and An. gambiae exhibit species-specific characteristics in chromosome-linear and -spatial organizations.

The properties of heterochromatin from polytene chromosomes of the malaria mosquito Anopheles messeae Fal. and A. atroparvus V. Tiel. were studied by various methods of differential staining and by hybridization in situ with two repetitive DNA sequences of Drosophila melanogaster. In malaria mosquito, the heterochromatin was heterogeneous. Two forms of alpha-heterochromatin were revealed: pericentromeric and intercalary heterochromatin, which is localized within the internal chromosome regions.

We investigated the variability of pericentromeric chromatin of chromosome 2 in ovarian nurse cells (trophocytes) in two laboratory lines of malaria mosquito Anopheles atroparvus V. Tiel and in their hybrids. One line had been raised by means of sib inbreeding, the other kept at constantly high population density. The inbreeding was shown to result in an increased percentage of chromosomes bearing an achromatinic zone in the centromeric region, which resulted in chromosome breakage. Toxicological tests demonstrated an increase in the sensitivity of the progeny of females with abnormal morphotypes of chromosome 2 to the entomopathogenic bacterium Bacillus thuringiensis israelensis. The appearance of the achromatinic zone is attributed to local chromatin underreplication accompanying chromosome polytenization. Possible reasons for this phenomenon and its implication for adaptation are discussed.

Certain aspects of the polytene chromosome attachment to the nuclear envelope (NE) of ovarian pseudonurse cells (PNC) in the mutant strains otu11 and fs(2) B of Drosophila melanogaster were studied. In contrast to salivary a local chromocenter and Rable-orientation of chromosomes were shown to be missing from the PNC nuclei. The pericentric regions were scattered in the nuclear space and were obliged to attach to the NE by specific loci of heterochromatin. These loci were assigned to the regions 20CD and 41, and the proximal regions 81 and 101 of the cytological map of secondary polytene chromosomes. Each of the loci, which was obliged to attach to the NE, had a specific morphology that was similar in the otu11 and fs(2)B strains. PNC were shown to resemble normal ovarian nurse cells of D. melanogaster in the position of the polytene chromosomes and their attachment to the NE.

M/SAR of Drosophila melanogaster DNA clone gamma 20p 1.4 was localized on chromosomes by in situ hybridization of the gamma 20p 1.4 DNA fragment and its deletion mutants with salivary gland chromosomes of third instar larvae of the lines Canton S and Oregon R. The M/SAR sequence, capable of specifically binding to lamin in vitro, was detected in the pericentric regions 20CD, 40EF, 41AB, the proximal part of region 81 of chromosome 3, and region 101 of chromosome 4, which attach to the nuclear envelope in cells of D. melanogaster salivary glands, and in region 49D, which does not come into contact with the nuclear periphery. This is the first M/SAR localized in pericentric chromatin of D. melanogaster.

The chromocenter organization and the relationship with the nuclear envelope were studied in Anopheles messeae Fall. malaria mosquito. The interchromosomal contacts within the chromocenter were shown to be formed by both alpha- and beta-heterochromatin. In the pericentric regions of all chromosomes and in highly repeated sequences localized mostly in alpha-heterochromatin, the incorporation of the moderate He-T repeat of D. melanogaster was also found. Each chromosome was shown to have an independent contact to the nuclear envelope via certain beta-heterochromatin loci. The morphology of the Y chromosome, which is also capable of forming ectopic contacts within the chromocenter boundaries, was studied.

A DNA fragment designated lambda 20p1.4 binds in vitro to polymerized Drosophila melanogaster lamin. In situ hybridization of lambda 20p1.4 to isolated polytene chromosomes revealed localization at the chromocenter and to the 49 CD region on the right arm of chromosome 2. About 120 copies of sequences homologous to lambda 20p1.4 were detected per haploid genome. Nucleotide (nt) sequence analysis demonstrates that lambda 20p1.4 is an A + T-rich, 1327-bp fragment containing four repeated units between nt 595 and 919. Results suggest that lamin interacts with a region of lambda 20p1.4 between nt 300 and 1000. Confocal immunofluorescence co-localization demonstrates that in situ, the major locus of lambda 20p1.4 hybridization, the chromocenter, is found juxtaposed to the nuclear envelope (lamina). This is the first demonstration that a DNA sequence that binds specifically to nuclear lamins in vitro, is located at or near the nuclear envelope in situ and, presumably, in vivo.

A molecular biological characteristic of a DNA fragment delta 20p1.4, which is a moderately repetitive sequence of the Drosophila melanogaster genome, is presented. The fragment is present in about 120 copies per haploid genome. The main pool of the delta 20p1.4 homologous DNA can be isolated, along with the nuclear matrix DNA, and consists of Hind III-EcoR I monomers 1.4-1.6 kb in length. The monomers may occur in the genome as both single copies and tandem clusters forming chromosomes fragments up to 6-10 kb in length. The region of the delta 20p1.4 fragment between nucleotides 350 and 905 polymerizes with purified lamin from D. melanogaster. The sites of the fragment that had physical contact with lamin in vitro were determined using an Exo III protection. It was demonstrated that ATATTT, A, and T boxes located in four nonperfect tandem repeats were involved in the contact, both DNA strains reacting with lamin.

A DNA fragment from the Drosophila melanogaster genome, cloned in lambda 20p7, was derived independently from clones lambda 20 and lambda L [Baiborodin et al., Genetika 29 (1993) 403-416; Sharakhov et al., Genetika 29 (1993) 392-402]. In situ hybridization of lambda 20p7 DNA to the chromosomes of D. melanogaster demonstrated preferential hybridization of the fragment to the chromocenter of polytene chromosomes and to pericentric heterochromatin of chromosomes II, IV and X at the metaphase plate. Copy number per haploid genome for lambda 20p7 was estimated as approximately 200. Based on Southern blotting, the major portion of this moderate repeat was localized in the region of a 5.5-kb HindIII digest. In situ hybridization to polytene chromosomes from strain fs(2)B trophocytes revealed that repeats homologous to lambda 20p7 are located in the proximal heterochromatin which undergoes structural reorganization during tissue differentiation. The nucleotide sequence of two segments of the clone lambda 20p7, Dm0.9 and Dm270, was determined. Sequence analysis of the 300-bp Dm0.9 clone revealed that it contains 21-bp and 30-bp d(GT/CA) sequences, a 12-bp AT box, recognition sites for nuclear factors NFI and SpI, and a set of inverted repeats. Clone Dm270 contains an open reading frame (ORF). The deduced amino acid (aa) sequence shares homology with the gag-like gene from type-I (R1) ribosomal DNA insertion and may code for a polypeptide of 10 kDa. The Dm270 sequence was found to contain two direct repeats showing homology to the human CENP-B box.

To isolate the DNA sequences specific for the pericentric heterochromatin of Drosophila we used two CREST-autoimmune sera which bind in the Western-blot analysis the nuclear antigens of 30 kDa, 43 kDa and 45 kDa molecular weight. Cloning of the DNA fragments associated with these CREST-specific proteins of Drosophila resulted in obtaining 8 clones. One of them, lambda 20, hybridized mainly to the chromomcenter of polytene chromosomes. The further analysis indicated that the lambda 20 DNA might belong to the proximal beta-heterochromatin of the polytene chromosomes of D. melanogaster.

To study the nucleotide sequence from the pericentric heterochromatin associated with the nuclear envelope, a residual DNA was extracted from the DNAse-treated nuclear lamins of Drosophila melanogaster tissue culture cell line Kc. The isolated DNA was cloned in lambda vector. The DNA library obtained was screened for the clones homologous to the pericentric heterochromatin. The experiments on in situ hybridization to the polytene chromosome of the nurse cell nuclei of the strain fs(2) B assigned the reiterated sequence, homologous to the lamin DNA clone, to the nuclear envelope associated regions of the proximal beta-heterochromatin which is known to undergo structural reorganization during cell differentiation. The nucleotide analysis of 300 bp from this sequence has established the presence of 21 bp and 300 bp d(GT/CA), 12 bp AT-box, the regions of recognition of the nuclear factor and the inverted repeats.