Biomedical subjects

E S Belyaeva

Publications and source records attributed to E S Belyaeva.

At least 37 records · Page 2Linked to original sources

PubMed1991

Transposition of mobile elements gypsy (mdg4) and hobo in germ-line and somatic cells of a genetically unstable mutator strain of Drosophila melanogaster.

Using the in situ hybridization technique, we have analysed the distribution of mobile elements in the X chromosomes of male offspring of individual mutator strain (MS) males crossed to attached-X females. The experiments demonstrate varying cytological localization of the mobile elements gypsy (mdg4) and hobo among different individuals. The other mobile elements investigated (mdg1, mdg3, 412, 297, copia, 17.6, Doc, H. M. S. Beagle, Springer, FB) display no changes in insertion sites. Such an experiment is equivalent to analysis of separate gametes of an MS individual. Thus, the ability of gypsy and hobo to transpose in germ-line cells is demonstrated directly. Transpositions occur at premeiotic stages of germ cell development, since they appear in clusters. Analysis of gypsy and hobo transposition events shows that they occur independently. The same experiment demonstrates that gypsy localization varies significantly between different salivary gland cells of an MS individual. Two types of gypsy hybridization sites can be distinguished: "permanent" sites, common to all cells, and "additional" ones varying between neighbouring salivary gland cells. These additional sites indicate gypsy transposition in somatic cells of the MS. Transposition of the hobo element in somatic cells has also been observed.

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PubMed1991

Constitutive heterochromatin in early embryogenesis of Drosophila melanogaster.

The formation of constitutive heterochromatin was studied during the embryonic development of Drosophila melanogaster, using the C-banding technique. During embryonic cleavage, C-banded material is not seen in mitotic chromosomes; the differentiation between euchromatin and heterochromatin only occurs at blastoderm. This event correlates with the establishment of position-effect variegation.

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PubMed1991

Cytogenetical analysis of the 2B3-4-2B11 region of the X chromosome of Drosophila melanogaster. VII. Influence of the ecs locus on female fertility.

Of 13 ecs mutations, which affect female fertility, as revealed by complementation analysis, 7 are chromosome rearrangements involving the br complementation group. The other six show no cytologically detectable rearrangements and behave as completely or partially noncomplementing ecs alleles. All viable combinations of these 13 mutations were characterized by partial or complete female sterility. Viable heterozygotes carrying any of these mutations and the rearrangements Df(1)sta, T(1;3)sta, Df(1)St490, previously localized distal to the ecs locus, were also sterile. Using deletions and an electrophoretic mobility variant from the Staket strain, a minor chorion gene S70 has been mapped. It had been thought this gene was located in the 2B3-5 region, and corresponded to the ecs locus. However, in the present study, this gene was shown to map in the region removed by Df(1)sta (1E1-2-2B3-4) but outside that removed by Df(1)At127 (1E1-2-2A1-2), i.e. within the 2A1-2-2B3-4 region which is distal to the ecs locus. Rearrangements and point mutations at the ecs locus that result in female sterility had no effect on synthesis of the chorion protein s70. It may therefore be suggested that the chorion protein gene is not functionally associated with the ecs locus and that sterility is caused not by disruptions of the chorion protein gene but by lesions in the ecs gene itself. Thus, an ecs product, which controls cell sensitivity to ecdysterone is also necessary for female fertility.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1991

Cytogenetic and molecular aspects of position effect variegation in Drosophila melanogaster. IV. Underreplication of chromosomal material as a result of gene inactivation.

A chromosomal region subjected to position effect variegation was analysed for possible DNA under-replication. DNA clones from the vicinity of the euheterochromatin junction and from a distance of hundreds of kilobase pairs were used as probes. Formation of compact blocks of chromatin is regarded as a characteristic feature of position effect variegation. It was shown that in T (1;2) dorvar7 males undergoing position effect variegation clones representing the DNA nearest to the breakpoint in 2B7 hybridized normally in situ to the compact blocks, providing evidence against DNA underreplication. In females the same clones did not hybridize to the compact blocks. These variations in hybridization may be related to different degrees of compaction of chromosome regions in males and females. A correlation between the degree of underreplication and the level of cell polyteny was shown by Southern-blot hybridization of a DNA probe from the 2B region to DNA from an X/O strain carrying Dp (1;1)pn2b displaying position effect variegation and compaction in 94% of salivary gland cells. Almost complete underreplication of the DNA of this region was found in salivary gland cells (with a maximal degree of polyteny), intermediate underreplication was found in fat body cells (with an intermediate degree of polyteny), and replication was not disturbed in diploid cells of the larval cephalic complex.

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PubMed1991

Cytogenetic and molecular aspects of position effect variegation in Drosophila. III. Continuous and discontinuous compaction of chromosomal material as a result of position effect variegation.

Variations in compaction of chromosomal material of the rearrangements Dp(1;f) 1337, Dp(1;f) R, Dp(1;1)pn2b, and T(1;4)wm258-21, which display an extended position effect, were characterized. Morphological changes found in these rearangements were assigned to two major types: (i) continuous compaction, in which bands and interbands located distal to the eu/heterochromatin junction fuse into one compacted block of chromatin. The extent of compaction is increased by enhancers of position effect (low temperature, removal of the Y or 2R chromosome heterochromatin). In extreme cases compaction extends over dozens of bands. (ii) Discontinuous compaction, in which at least two zones of compaction separated by morphologically normal zones can readily be identified. As a result, some regions located at a greater distance from heterochromatin may be compacted more frequently than others that map nearer to it. A few regions (1D, 2B1-12, 2D) were shown to be most frequently compacted in all rearrangements investigated. The 2B13-18, 2C1-2, 2E, and 2F regions exhibited the lowest frequencies of compaction. Compaction of the zone containing the 2B1-12 bands is always accompanied by inactivation of the ecs locus, which maps in the 2B3-5 puff. At the same time the 2C1-2 and 2E bands located nearer to the breakpoint can retain normal morphology and puffing in response to ecdysterone. The results are interpreted as morphological manifestations of the discontinuity of the spreading effect.

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PubMed1990

Autonomous transposition of gypsy mobile elements and genetic instability in Drosophila melanogaster.

The laboratory mutator strain (MS) of Drosophila melanogaster is characterized by an elevated frequency of spontaneous mutation (10(-3)-10(-4). Mutations occur in both sexes at premeiotic stages of germ cell development. The increased mutability is a characteristic feature of MS itself, since it appears in the absence of outcrossing. Most of the mutations arising in this strain are unstable: reversions to wild type, high frequency mutation to new mutant states and replicating instability were observed. We have investigated the localization of the transposable genetic elements mdg1, 412, mdg3, gypsy (mdg4), copia and P in the X chromosomes of the MS and in the mutant lines y, ct, sbt derived from it by in situ hybridization. The P element was not found in any of these strains. The distributions of mdg1, 412, mdg3 and copia were identical in the X chromosomes of the MS and its derivatives. However, the sites of hybridization with gypsy differ in the various lines tested. In the polytene chromosomes of MS animals significant variation in location and number of copies of the gypsy element was demonstrated between different larvae; copy numbers as high as 30-40 were observed. These results suggest autonomous transposition of gypsy in the MS genome while several other mobile elements remain stable.

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PubMed1989

Position-effect variegation and intercalary heterochromatin: a comparative study.

The behaviour of IH (intercalary heterochromatin) regions of Drosophila melanogaster polytene chromosomes was compared with that of euchromatin condensed as a result of position-effect variegation. Normally replicating regions, when subject to such an effect, were found to become among the last regions in the genome to replicate. It is shown that the factors which enhance position effect (low temperature, the removal of the Y chromosome, genetic enhancers of position effect) increase the weak point frequency in the IH, i.e. enhance DNA underreplication in these regions. We suggest that the similarity in the properties of IH, CH (centromeric heterochromatin) and the dense blocks induced by position effect is due to strong genetic inactivation and supercondensation caused by specific proteins in early development. The primary DNA structure is not likely to play a key role in this process.

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PubMed1989

Electron microscopical analysis of Drosophila polytene chromosomes. V. Characteristics of structures formed by transposed DNA segments of mobile elements.

An electron microscopical (EM) analysis was performed on regions of polytene chromosomes which contained DNA segments of different genetic composition, inserted by P element-mediated transformation into the Drosophila melanogaster genome. In seven of ten regions examined, containing insertions of the hsp28-ry, hsp70-Adh, ryhsp 70-beta-gal genes and of the ry gene tetramer, new bands appeared. Lack of new bands in three other strains is apparently connected with the fusion of the inserted material to preexisting bands. The new bands do not differ morphologically from the usual bands of polytene chromosomes, and their formation is likely due to predominant insertion of DNA segments into interbands. Among the constructs examined, the minimal length of a DNA segment which appears as a new band is about 5 kb; the DNA packing ratio in the new bands varies from 30 to 50. Activation of the inserted genes by heat shock has enabled us to observe the puffing characteristics of new bands. A sequence of some one kb forms a large interband, or micropuff; the puff size is correlated with the length of the genes being activated. If a DNA segment contains a single gene, then its activation causes the decompaction of the whole band; however, when a DNA segment consists of two genes and the promoter element of the activated gene is positioned in the middle of the sequence, the band splits and only part is decompacted and puffed. The DNA packing ratio in the puffs is 1.4-3.5. The subsequent deletion of the hsp70 promoter but retention of 23, 59, and 73 by from the transcription start points leads to failure of puff formation. In all the transformed sites an increase in the total length of the interbands adjacent to the insert as compared with the initial interband was observed. This increase appears to be due to decompaction of the P element DAN flanking the inserted segments. It is shown that a DNA segment, consisting of four tandemly repeated ry gene copies and interspersed by material which includes P DNA, forms a complex of loose chromatin in which, however, four bands can be resolved. We also observed a lengthening of interband regions containing only the P element sequence itself. Insertion of the complete 2.9 kb P element into the large single 10A1-2 bound of the X chromosome (an insertion in the region approximately 10 kb to the right of the v gene) causes splitting of the band into two parts and formation of a new interband.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1988

Cytogenetic and molecular aspects of position effect variegation in Drosophila melanogaster. II. Peculiarities of morphology and genetic activity of the 2B region in the T(1;2)dorvar7 chromosome in males.

The peculiarities of compact blocks appearing as a consequence of position effect variegation were studied in male polytene chromosomes. In T(1;2)dorvar7/Y males the frequency of nuclei with a block in the 2B region was lower at all temperature and the chromosome region involved in compaction was shorter than in T(1;2)dorvar7/FM6 females. The fraction of nuclei with blocks was considerably increased in dorvar7/0 males, especially at 18 degrees C when the viability of these males is sharply reduced. The following features distinguish the blocks in males from those in females: (i) compaction of the 2B region in the males results in genetic inactivation only to a very small extent; (ii) the structure of the blocks in males is diffuse; and (iii) the male blocks still maintain some transcriptional activity as indicated by 3H-uridine incorporation. The temperature-sensitive period of both block formation and genetic inactivation was found to be during the first 3 h of embryonic development.

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PubMed1986

Concerted transpositions of mobile genetic elements coupled with fitness changes in Drosophila melanogaster.

In an inbred low-activity (LA) strain of Drosophila melanogaster with a low level of fitness and a complex of inadaptive characters, in situ hybridization reveals an invariant pattern of distribution of three copia-like elements (mdg-1, mdg-3, and copia). Rare, spontaneous, multiple transpositions of mobile elements in the LA strain were shown to be coupled with a drastic increase of fitness. A changed pattern of various types of mobile elements was also observed on selecting the LA strain for higher fitness. High-fitness strains show transpositions of mobile elements to definite chromosomal sites ("hot spots"). Concerted changes in the location of three different mobile elements were found to be coupled with an increase of fitness. The mdg-1 distribution patterns were also examined in two low-fitness strains independently selected from the high-fitness ones. Fitness decrease was accompanied by mdg-1 excision from the hot spots of their location usually detected in the high-fitness strains. The results suggest the existence of a system of adaptive transpositions of mobile elements that takes part in fitness control.

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PubMed1985

Electron microscopical analysis of Drosophila polytene chromosomes. II. Development of complex puffs.

Data are presented of electron microscopic (EM) analysis of consecutive developmental stages of Drosophila melanogaster complex puffs, formed as a result of simultaneous decondensation of several bands. EM mapping principles proposed by us permitted more exact determination of the banding patterns of 19 regions in which 31 puffs develop. It is shown that 20 of them develop as a result of synchronous decondensation of two bands, 7 of three and 4 of one band. Three cases of two-band puff formation when one or both bands undergo partial decondensation are described. In the 50CF, 62CE, 63F and 71CF regions puffing zones are located closely adjacent to each other but the decondensation of separate band groups occurs at different puff stages (PS). These data are interpreted as activation of independently regulated DNA sequences. The decondensation of two or three adjacent bands during formation of the majority of the puffs occurs simultaneously in the very first stages of their development. It demonstrates synchronous activation of the material of several bands presumably affected by a common inductor. Bands adjacent to puffing centres also lose their clarity as the puff develops, probably due to "passive" decondensation connected with puff growth. The morphological data obtained suggest a complex genetic organisation of many puffs.

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PubMed1985

Electron microscopical analysis of Drosophila polytene chromosomes. III. Mapping of puffs developing from one band.

Mapping of 16 regions of polytene chromosomes in which 18 one-band puffs develop was carried out with the use of electron microscopy (EM). In most cases a uniform decondensation of the whole band was observed. However, there were examples in which only a part of the band was activated (three puffs) or its right and left parts decondensed simultaneously (three puffs). Splitting of the band into two parts with their further decondensation was also found (one puff). This suggests structural and functional complexity of the bands. On the basis of the data obtained here and those published earlier, a classification of 52 puffs by the number of bands participating in their formation is given. Four classes numbering 22, 21, 7, 2 puffs, developing from 1, 2, 3 and 4 bands, respectively, are revealed. The data show that active chromosome regions are rather diverse in both the pattern of decondensation and expansion of the decondensed region, thus providing evidence of the informational complexity of the majority of active regions.

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PubMed1985

Immunofluorescence localization of DNA:RNA hybrids in Drosophila melanogaster polytene chromosomes.

Sites of transcriptional activity in the whole set of Drosophila melanogaster polytene chromosomes have been localized by means of fluorescent antibodies against DNA:RNA hybrid molecules and compared with results on 3H-uridine incorporation obtained earlier. The majority of large and small puffs with intensive 3H-uridine incorporation demonstrate bright fluorescence. Moreover, bright fluorescence is also observed for a large number of small puffs though the intensity of 3H-uridine incorporation is low. Some prominent puffs with high levels of 3H-uridine incorporation show weak fluorescence. Condensed bands, as a rule, do not show fluorescence. The regions that look like interbands under the light microscope are not real interbands, but consist of minibands visible only in the electron microscope (EM). However, a region that has been previously studied by EM and proven to be a real interband between two thick dark bands (100B3-100B4-5) showed fluorescence. These data support previous suggestions indicating a substantial contribution of transcriptional products from small puffs and interbands to the whole transcriptional system of polytene chromosomes.

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PubMed1983

Genetic interpretation of polytene chromosomes banding pattern.

This mini-review covers new data regarding the problem of the functional organization of polytene chromosomes: The localization of RNA synthesis in the polytene chromosome puffs, diffuse bands and interbands; The relative stability of banding pattern and its functional value; The informational content of bands.

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PubMed1982

Cytogenetic analysis of the 2B3-4--2B11 region of the X chromosome of Drosophila melanogaster. III. Puffing disturbance in salivary gland chromosomes of homozygotes for mutation l(1)pp1t10.

Puffing patterns have been studied both in homozygotes t10/t10, a gene located in the area of the early ecdysone puff 2B5, and in a yellow (y) control stock, at the end of the third instar and during prepupal development. In mutants t10 at the end of the third instar puffing develops normally in general, however, 21 puffs (5 early and 16 late ones) underdevelop or do not develop at all, some larval intermoult puffs regressing slower. The next cycle of puffs (mid prepupal) in mutants t10 proceeds normally, but in the late prepupal cycle 21 puffs underdevelop again or are not formed at all. A model for the induction of early ecdysone puffs is proposed, assigning a key role to the 2B5 puff product in stimulating other early puffs. It is suggested that defects in the activity of early puffs in the mutant t10 may cause underdevelopment of late puffs.

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PubMed1982

Transpositions of mobile dispersed genes in Drosophila melanogaster and fitness of stocks.

In situ hybridization with polytene chromosomes was used to demonstrate the transposition of mobile dispersed genes (mdg)-1 and 3 following the selection of flies from low reproductive activity and viability (LA stock) for high reproductive activity, viability and fitness (LA+ and HA stocks). The inbred LA stock is continuously selected for low reproductive activity and viability and maintains at least for twenty-five generations a characteristic pattern of mdg-1 distribution in 14-15 sites. Inbred LA+ and HA stocks exhibit a changed pattern of mdg-1 locations and the number of sites reaches 21-25. Parallel and independent selection for higher viability may lead to similar characteristic changes in the localization of mdg-1. In several independent experiments we observed, within one generation, a spontaneous and saltatory growth of viability and fitness in the mass-bred LA stock. In these cases new mdg-1 and mdg-3 sites reproducibly appeared to within several bands, some of them characteristic of LA+ and HA stocks. We discuss the possible role of mdg in determining the quantitative characters of individuals and their fitness.

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PubMed1981

Fine cytogenetical analysis of the band 10A1-2 and the adjoining regions in the Drosophila melanogaster X chromosome. I. Cytology of the region and mapping of chromosome rearrangement.

The region 9E1-2 - 10B1-2 of the Drosophila melanogaster X chromosome was analysed under the light (LM) and the electron (EM) microscope using different fixatives and an EM map of the region was constructed. EM analysis revealed 21 bands in the region 9E1-2 - 10B1-2 instead of 36 bands in Bridges' map. This discrepancy mainly results from the fact that 14 bands indicated as "doublets" by Bridges appear as a single bands. No doublets were found in the whole 9B1-2 - 10C1-2 region after fixation of salivary glands in 3% glutaraldehyde, 3% formaldehyde and 3 : 1 ethanol-acetic acid mixture. 45% acetic acid is the only fixative which results in strongly vacuolated appearance of the bands. - The break points of 30 chromosome rearrangements in the region 9E1-2 - 10B1-2 were located under EM or LM within the limits of the EM map of this region.

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PubMed1981

Fine cytogenetical analysis of the band 10A1-2 and the adjoining regions in the Drosophila melanogaster X chromosome. II. Genetical analysis.

The X chromosome region 9F12-10A7 (7 bands removed by Df(1)VL3) was saturated with lethal, semi-lethal, visible and male sterile mutations A total of 11 complementation groups were found. In the more narrow interval of Df()1)VL1 which removes 3 bands (10A1-2, 10A3, 10A4-5) 6 loci were localised. - The band 10A1-2 consists of a sereis of 5 different subunits: (i) silent DNA where no functions were found - at the distal edge of the band; (ii) and (iii) two genes: v and 1(1)BP4; (iv) silent DNA in middle of the band, (v) locus sev on the proximal edge of the band. About 70% of the band's DNA was found to be silent. - Using the set of chromosome rearrangements removing different parts of the band it was shown that these five sequences may function independently from each other.

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