[COMPARATIVE STUDY OF Hrs AND OTHER ENDOSOMAL MARKERS CELLULAR LOCALIZATION IN DROSOPHILA MELANOGASTER SPERMATOGENESIS BY GFP-CHIMERICAL PROTEIN APPROACH].

Acrosome is a special organelle in spermatozoids necessary for fertilizing oocyte and originates, according to various theories, either from Golgi apparatus, or from endosomes and lysosomes. One of the proteins, found at mammalian acrosome, is Hgs, a homologue of Drosophila melanogaster Hrs (Hepatocyte growth factor regulated tyrosine kinase substrate), a known marker of multivesicular bodies (MVBs). However, although Drosophila acrosome was extensively studied, it is yet unknown whether Hrs localizes at acrosome similar to Hgs and, more generally, whether the spectrum of acrosomal proteins in Drosophila is the same as in mammals. Hrs (hepatocyte growth factor regulated tyrosine kinase substrate) is the multidomain vesicular protein participating in the endosome-lysosome protein sorting. We demonstrated that two protein variants of the Drosophila Hrs are expressed in testes: a longer isoform B, and a shorter isoform A, which lacks VHS and FYVE domains that are necessary for anchoring Hrs in endosomes. We found that Hrs isoform B is concentrated at fusoma of spermatocytes in contrast to mammalian Hrs. This localization requires the C-terminus of the protein, starting from the aminoacid residue 383. In situ hybridization of hrs RNA probe showed that the gene is expressed early in spermatogenesis consistently with Hrs localization in early fusoma. Additionally, we demonstrated that Hrs is dispensable for cytokinesis. Finally, it was found that although Drosophila Hrs does not localize at acrosome, the other endosomal markers--Rab4, Rab7, and Rab11--are detected at the organelle.

[Role of the Drosophila melanogaster hrs gene in wing formation].

The Hrs (hepatocyte growth factor receptor tyrosine kinase substrate) protein is an endosomal protein whose function is to transport receptor tyrosine kinases from early endosomes to lysosomes. Since receptor tyrosine kinases are involved in various signaling pathways, HSR defects lead to various malformations. A study of the role of the hrs gene in wing development in Drosophila confirmed that the gene is involved in the formation of the D/V boundary of the wing imaginal disk and suggested a new role in wing vein refinement for the gene. Structural analysis of the hrs gene transcripts indicated that transcript B is responsible for vein refinement.

[The influence of morphogene Wg on the formation of an ectopic eye in Drosophila melanogaster].

Due to the ectopic expression of the ey gene in the wing imaginal disc under the action of the 1096-Gal4 driver, a part of the wing disc cells change their fate and become eye cells. Ectopic eyes are induced in definite regions of the wing disc and form a stable pattern on the wing of an adult fly. Here, we have shown that the ectopic expression of Wg inhibits the formation of ectopic eyes, and conversely the expression of Wg is reduced in the sites of ectopic Ey expression. Experiments with overexpression of the vesicular traffic protein H rs capable of inhibiting the Wg signaling agree with the notion on antagonism of Wg and Ey in ectopic eyes. Our results confirm that the processes of formation of normal and ectopic eyes are principally similar with regard to genetic control.

[Drosophila melanogaster gene Merlin interacts with the clathrin adaptor protein gene lap].

The protein Merlin is involved in the regulation of cell proliferation and differentiation in the eyes and wings of Drosophila and is a homolog of the human protein encoded by the Neurofibromatosis 2 (NF2) gene whose mutations cause auricular nerve tumors. Recent studies show that Merlin and Expanded cooperatively regulate the recycling of membrane receptors, such as the epidermal growth factor receptor (EGFR). By performing a search for potential genetic interactions between Merlin (Mer) and the genes important for vesicular trafficking, we found that ectopic expression in the wing pouch of the clathrin adapter protein Lap involved in clathrin-mediated receptor endocytosis resulted in the formation of extra vein materials. On the one hand, coexpression of wild-type Merlin and lap in the wing pouch restored normal venation, while overexpression of a dominant-negative mutant Mer(DBB) together with lap enhanced ectopic vein formation. Using various constructs with Merlin truncated copies, we showed the C-terminal portion of the Merlin protein to be responsible for the Merlin-lap genetic interaction. Furthermore, we showed that the Merlin and Lap proteins colocalized at the cortex of the wing imaginal disc cells.

[Effect of mutations in Drosophila melanogaster tumor suppressor Merlin on proliferation and differentiation of wing cells].

Experiments on transplantation of wing imaginal discs homozygous for a mutation in the tumor suppressor gene Merlin have demonstrated that this mutation does not induce malignant tumors. Marking of the wing disc compartment borders by specific antibodies showed the absence of essential compartment border defects in case of the Merlin mutation. Drosophila melanogaster cells mutant for Merlin have shorter cell cycle than normal cells. Proliferation of imaginal discs lasts longer in case of the mutation. It is known that beginning from some moment of development, wing veins serve as clonal restriction lines that cannot be crossed by growing mosaic clones. We showed that the Merlin mutation leads to depression of vein clonal restriction property. This means that this gene is involved not only in the control of cell proliferation, but also in the control of cell mobility and adhesion.

[The role of the functional sites of the Merlin tumor suppressor in Drosophila spermatogenesis].

The Merlin gene of Drosophila is homologous to the human Neurofibromatosis 2 (NF2) gene an important regulator of proliferation and endocytosis of cell receptors. It was earlier shown that the Thr5 residue of the Drosophila Merlin protein was homologous to Ser518 of the human protein (which was already known to undergo phosphorylation); hence, it was assumed that Thr559 of Drosophila also was a substrate of phosphorylation. The mutant Merlin proteins MerT559D (an analog of the phosphorylated form) and MerT559A (a nonphosphorylated form) were constructed and tested, under the conditions of ectopic expression for the ability to correct the spermatogenesis defects induced by the Mer4 mutation. The mutant form MerT559D was demonstrated to restore the abnormal nebenkern phenotype induced by this mutation, whereas the MerT559A substituted form did not restore this phenotype. Ectopic expression o the wild-type Merlin protein, MerT559A mutant form, and mycMer345-635 truncated protein in a normal genotype resulted in the abnormal nebenkern phenotype, whereas this phenotype was not observed in the case ofectopic expression of the MerT559D analog of the phosphorylated form. Ectopic expression of the mycMer3, mycMerABB, and mycMer-379 truncate variants led to disturbance of meiotic cytokinesis.

[High frequency induction of small mosaic cell clones in the Drosophila wings under the influence of gamma-irradiation].

As it was shown earlier in Gonzalez-Gaitan et al., one-cell and two-cells clones (tailing clones) are induced in the Drosophila wings after irradiation and represent a significant portion of clones detected with the use of mwh genetic marker. Our experiments shown that gamma-irradiation occur to be more efficient inductor of such small clones. Earlier small clones were considered as a result of the induced chromosomal aneuploidy of those low proliferating cells. Our data suggest that the small clones descend from the low proliferative cells of non-imaginal disc origin that migrate to the wing imaginal disc at some developmental point.

[Role of the porcupine gene in the development of the wing imaginal disk of Drosophila melanogaster].

A search for the genes interacting with the Merlin tumor suppressor gene revealed a Merlin-porcupine interaction during wing morphogenesis. Ectopic expression of the porcupine gene in the wing imaginal disk reduced the adult wing, while addition of an UAS construct with a full-length or truncated copy of the Merlin gene partly restored the wing phenotype. The highest restoration level was observed upon adding the fragments coding for the C end of the Merlin protein. In addition, the porcupine gene was shown to mediate the wingless gene autoregulation, which occurs at two ontogenetic stages, segmentation during embryo development and determination of the wg expression band at the boundary between the dorsal and ventral compartments of the wing imaginal disk.

[A combined approach to mapping the proximal border of the right arm of polytene chromosome 2 in Drosophila melanogaster otu 11].

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.

[From genetics of intraspecific differences to genetics of intraspecific similarity]. / Ot genetiki vnutrividovykh otlichii k genetike vnutrividovogo skhodstva.

Based on the Mendelian approach to heredity, modern genetics describes inheritance of characters belonging to the category of intraspecific difference. The other large category of characters, intraspecific similarity, stays out of investigation. In this review, the genome part responsible for intraspecific similarity is considered as invariant and regulatory. An approach to studying the invariant part of the Drosophila melanogaster genome is formulated and the results of examining this genome part are presented. The expression of mutations at genes in the invariant genome part is different from that of Mendelian genes. We conclude that these genes are present in the genome in multiple copies and they are functionally haploid in the diploid genome. Severe abnormalities of development appearing in the progeny of mutant parents suggest that the mutant genes are genes regulating ontogeny. A hypothesis on an elementary ontogenetic event is advanced and the general scheme of ontogeny is presented. A concept on two types of gene allelism (cis- and trans-allelism) is formulated. This approach opens a possibility for studying genetic material responsible for the formation of intraspecific similarity characters at different taxonomic levels on the basis of crossing individuals of the same species.

[Genes controlling ontogenesis: morphosis, phenocopies, dimorphs, and other visible expressions of mutant genes]. / Geny, upravliaiushchie ontogenezom: morfozy, fenokopii, dimorfy i drugie vidimye proiavleniia mutantnykh genov.

We studied facultative dominant lethal mutations obtained earlier in Drosophila melanogaster. In some genotypes, these mutations were expressed as lethals, but in other genotypes they lacked this expression. The mutations were maintained in the following cultures: (1) females Muller-5 heterozygous for the mutation; (2) males crossed to attached-X females; and females and males homozygous for the mutation. During culturing, many mutations were found to give rise to phenotypically abnormal progeny. Generally, these abnormalities were morphoses involving various body parts; they were mostly asymmetric and non-heritable. Maternal and paternal effects in the formation of morphoses were observed. In four cases, dimorphic mutations were recorded: a female homozygous for the mutation had mutant phenotype whereas its male counterpart was phenotypically normal. The mutations were recessive with regard to the norm. New phenotypes behaving as mutations with incomplete penetrance arose during culturing. In cultures of mutant homozygotes phenocopies would appear en masse; they would persist for one or two generations and disappear. One wave of phenocopies succeeded another. Visible phenotypes appeared, which further behaved as ordinary recessive mutations. We concluded that these visible manifestations are characteristic for regulatory mutations controlling ontogeny. Their appearance is explained by the activation of new regulatory scenarios caused by blocking standard regulatory pathways.

[Age-related changes in crossing over in Drosophila resemble the picture of interchromosomal effect of chromosome rearrangement on crossing over]. / Vozrastnye izmeneniia krossingovera u drozofily vosproizvodiat kartinu mezhkhromosomnogo vliianiia na krossingover khromosomnoi perestroiki.

Crossing over in the left arm of chromosome 2 (2L) was studied in successive broods of Drosophila melanogaster females carrying intact chromosomes (+/+), inversion Muller-5 in the X chromosome (M-5/+), and insertion of the Y-chromosome material into region 34A (Is(2L)/+). The regions net-dp, dp-b, b-pr and pr-cn were examined in 14 two-day-old broods of females +/+ and M-5/+ and in 10 broods of females Is(2L)/+. In all lines, the highest level of crossing over was in the first three broods (eggs laid during the first 6 days of oviposition) and the lowest level in the broods 7-8 (eggs laid at days 14-16). A high rate of crossing over in the first broods of females +/+ and M-5/+ was due to an increment of exchanges in the proximal euchromatin regions (b-pr and pr-cn) and to an increase in the number of tetrads with double exchanges. These changes are similar to a pattern of the interchromosomal effect on crossing over (IEC) in structurally normal chromosomes. In Is(2L)/+ females, a high level of crossing over was due to extensive exchanges in the interstitial regions net-dp and dp and an increase in the number of tetrads with single exchanges. These changes resembled the IEC in rearranged chromosomes (in this case, in chromosomes bearing an insertion). Thus, the age changes of crossing over are similar to the consequences of the presence or absence of IEC. Age changes in crossing over in a chromosome depended both on the local rearrangements in this chromosome (the local effect on crossing over, LEC) and on rearrangements in nonhomologous chromosomes (IEC). In the first broods, both LEC and IEC decreased with an increase in the level of crossing over. In subsequent broods, the reduced level of crossing over was accompanied by an increase in both LEC and IEC. This suggests that the mechanisms responsible for the age changes in crossing over and IEC may have common steps. The contact model of crossing over may explain the similarity between the age changes in crossing-over and IEC. It is suggested that both phenomena result from delayed determination of crossing over in a meiotic cell. This may occur due to the retarded formation of the local contacts in one of the homologous chromosome pairs or because a higher number of local contacts is required to trigger crossing over in a meiotic cell (of early age).

[Chromosome rearrangement: two ways of influencing crossing over in Drosophila]. / Khromosomnaia perestroika: dva puti vliianiia na krossingover u drozofily.

Insertion of the Y-material into the 34A Is(Y;2L)419 region diminished recombinational length of the left arm of chromosome 2 (2L) from 49.1 to 15.0 cM. This decrease was compensated by the increase of recombinational length in the other chromosomal arms due to interchromosomal effect. The increase in the X chromosome was 11.4 cM; it was 2.0 cM in chromosome 2R; and 17.3 cM in chromosome 3. The insertion-induced decrease of the 2L recombinational length could be eliminated by evoking interchromosomal effects from other chromosomes. The presence of the inversion in the X chromosome increased the 2L recombinational length from 15.0 to 30.2 cM, while its association with the In(3LR)D inversion increased this length to 45.6 cM. The interchromosomal effects in the inductor chromosome were induced by distortion of pairing rather than by the low recombinational length of this chromosome. For example, the interchromosomal effect of the insertion on the X chromosome was higher in the Is(Y;2L)/+; In(3LR)/+ females than in the Is(Y;2L)/+; +/+ females (15.4 versus 11.5 cM), though the 2L recombinational length in the females with the former genotype (30.2 cM) was twofold higher than in females with the latter genotype (15.0 cM). It is suggested that chromosomal rearrangement hampers the development of local contacts in the homologues. This delay affects crossing over in the given pair of homologues in two ways: directly via diminishing the number of exchange sites, and indirectly through regulatory delay of crossing over determination in the meiocyte. The effects of the insertion on crossing over in nonhomologous chromosomes are implemented by through the second way.

[Crossing over in rearranged Drosophila chromosomes: the role of delayed pairing]. / Krossingover v perestroennykh khromosomakh drozofily: rol' zaderzhki sparivaniia.

A Df(2R)MS2-10 deletion of pericentromeric heterochromatin, an Is(Y;2L)419 insertion of Y material in the region 34A, as well as nondisjunction of chromosomes 2 in 2/F(2L); F(2R) females did not directly prevent chromosome arms in chromosome 2 of Drosophila from pairing. However, these events resulted in (1) two- to four-fold decrease in the rate of crossing-over in chromosome 2;(2) a decreased proportion of exchange tetrads two to three times greater for multiple-exchange tetrads than for single-exchange ones; (3) and a decreased rate of crossing-over throughout the entire chromosome arm enhanced in a proximal direction, An In(l)dl-49+BMl inversion in the X chromosome cancelled the suppression of crossing-over. Crossing-over increased due to an increasing proportion of single-exchange tetrads. The changes in crossing-over found cannot be explained by asynapsis in the chromosomes with rearrangements. According to the authors, these changes are probably accounted for by a delayed pairing of these chromosomes. The delayed pairing of individual chromosome regions or the whole chromosome is considered the most common type of pairing disturbances. Its effect on meiosis are discussed.

[The mechanism of the interchromsomal effect on crossing over in Drosophila melanogaster: delayed crossing over]. / Mekahnizm mezhkhromosomnogo vliianiia na krossingover u Drosophila melanogaster: zapazdyvanie krossingovera.

Interchromosomal effect on crossing-over (IEC) in autosome 2 has been studied in 2/F(2L); F(2R) females heterozygous for free arms (acrocentrics) and in Is(Y;2)419/+ females with an insertion of Y-material into the region 34A. IEC was induced by In(1)dl-49 + BM1 inversion. Manifestations of IEC included increased recombinational length of chromosome 2 and decreased interference. IEC was not observed in Df(2L)TW161/+ females with 38A-40 deletion. The patterns of IEC in three types of gametes of the 2/F(2L); F(2R) female depended on the pairing relations of the affected chromosome (chromosome-responder). In the case of normal pairing between the metacentric autosome 2 (the metacentric) and the F(2R) acrocentric, the increment in 2R length was minimal (20%), and the increment in the proportion of multiple-exchange (high-rank) tetrads (E2 + E3), maximal (8 to 10%). In the case of disturbed pairing 2-F(2R) nondisjunction, 2R length was increased by 77%, paralleled by a minimal increase in the proportion of high-rank tetrads (4%). Similarly, in females with the insertion, a pronounced increase in 2L length (74%) was associated with a moderate level of high-rank tetrads. When pairing in the chromosome-responder was normal, the increment in crossing-over was maximal in the pericentromeric region. In the case of disturbed pairing, this maximum either shifted toward the middle of the arm 2-F(2R) nondisjunction, or occupied a distal position (in females with the insertion). It is concluded that IEC pattern depends on the order of pairing in the chromosome-responder. The mechanism of IEC appears to be related to pairing "defects" within the responder. It is tempting to speculate that the onset of crossing-over is a whole-cell event, which is regulated by the overall level of chromosome pairing within the meiotic cell. Chromosomal aberrations increase the time required for attaining this level, and the start of crossing-over is delayed. As a result, (1) exchanges are observed in the regions of late synapsis, which are usually not involved in crossing-over; (2) overabundance of recombination enzymes, caused by delayed start of crossing-over, creates the conditions for decreased interference in paired regions.