The structural organization of the retrotransposon gypsy (mdg4) is investigated in two Drosophila melanogaster strains. One of them, the stable w strain (SS), is characterized by a small copy number and stable localization of gypsy. In the other, unstable mutator strain (MS) which is derived from SS, the gypsy copy number and the frequency of its transposition are greatly increased. Genomic gypsy copies cloned from both strains display structural differences allowing them to be divided into two subfamilies. At the nucleotide level, these differences involve single substitutions, deletions and insertions. Southern blot analysis revealed that SS possesses only gypsy elements that belong to one subfamily, while in MS only gypsy copies from the other subfamily were amplified and transposed. The transcriptional activity of gypsy was also studied. Despite the structural differences, plasmid-borne copies of each type of gypsy exhibit equal transcriptional activity in transfected tissue culture cells. Nevertheless, although a high level of gypsy transcription is observed in MS, gypsy poly(A)+RNA is not detected in SS.

A previously described genetic system comprising a Mutator Strain (MS) and the Stable Strain (SS) from which it originated is characterized by genetic instability caused by transpositions of the retrotransposon gypsy. A series of genetic crosses was used to obtain three MS derivatives, each containing one MS chromosome (X, 2 or 3) in the environment of SS chromosomes. All derivatives are characterized by elevated frequencies of spontaneous mutations in both sexes. Mutations appear at the premeiotic stage and are unstable. Transformed derivatives of SS and another stable strain 208 were obtained by microinjection of plasmid DNA containing transpositionally active gypsy inserted into the Casper vector. In situ hybridization experiments revealed amplification and active transposition of gypsy in SS derivatives, while the integration of a single copy of gypsy into the genome of 208 does not change the genetic properties of this strain. We propose that genetic instability in the MS system is caused by the combination of two factors: mutation(s) in gene(s) regulating gypsy transposition in SS and its MS derivatives, and the presence of transpositionally active gypsy copies in MS but not SS.

Long terminal repeat (LTR) retrotransposons occupy a special place among all mobile genetic element families. The structure of LTR retrotransposons that have three open reading frames is identical to DNA forms of retroviruses that are integrated into the host genome. Several lines of evidence suggest that LTR retrotransposons share a common ancestry with retroviruses and thus are highly relevant to understanding mechanisms of transposition. Drosophila melanogaster is an exceptionally convenient model for studying the mechanisms of retrotransposon movement because many such elements in its genome are transpositionally active. Moreover, two LTR-retrotransposons of D. melanogaster, gypsy and ZAM, have been found to have infectious properties and have been classified as errantiviruses. Despite numerous studies focusing on retroviral integration process, there is still no clear understanding of integration specificity in a target site. Most LTR retrotransposons non-specifically integrate into a target site. Site-specificity of integration at vertebrate retroviruses is rather relative. At the same time, sequence-specific integration is the exclusive property of errantiviruses and their derivatives with two open reading frames. The possible basis for the errantivirus integration specificity is discussed in the present review.

The DIP1 is a regulator gene of D. melanogaster with an unknown function. As a result of mRNA alternative splicing, at least 6 coding sequences are formed (DIP1-c/Klett-c, DIP1-b/ Klett-d, DIP1-d, DIP1-а, Klett-a, and Klett-b). Structure and expression of DIP1 homologues in various species of the melanogaster subgroup, such as D. melanogaster, D. sechellia, D. mauritiana, D. simulans, D. erecta,and D. yakuba, have been analyzed. In D. sechellia, D. simulans, and D. mauritiana we found alterations, which affected expression of the DIP1 homologues in contrast to D. melanogaster, D. erecta, and D. yakuba. These alterations have to do with splicing of the first alternative exon. It has been demonstrated that DIP1 homologues of D. sechellia, D. simulans and D. mauritiana do not code for Klett-а and Klett b forms.

Background. Hypogonadotropic hypogonadism (HH) is a disorder characterized by delayed or absent pubertal development due to pathology of the hypothalamic-pituitary-gonadal axis. HH may be both congenital (Kallmann’s syndrome) and sporadic. Congenital or isolated HH is divided into with anosmia/hyposmia (KS) and with normal olfaction (nIHH). Nowadays several tens of genes involved in the functioning of the reproductive axis are known. However DNA lesions can be found just in 5-15% of such cases of HH.Aim. So we decided to measure mRNA expression of several genes which can be found in leukocytes of peripheral blood - namely GNRHR and GNRH1 (are necessary for adequate biological effect of GnRH); PROK2 and CHD7 (are responsible for the migration of GnRH neurons), WDR11 and DUSP6 (are involved in normal sexual development).Methods. A quantitative determination of mRNA expression of these genes were comlpeted in the fresh peripheral blood sample by PCR in real time.Results. Examined patients: 9 women with hypogonadotropic hypogonadism (age from 18 to 28 y.o.); duration of the disease from 2 to 15 years; 3 of them – amenorrhea I and 6 – amenorrhea II. Reasons of amenorrhea II were: stress, excessive exercises, rapid body weight loss, past use of oral contraceptives. The control group: 19 healthy women; age from 19 to 37 y.o.; with regular ovalutory menstrual cycle, some of them have children. mRNA expression of examined genes differed from normal patterns in each case of hypogonadotropic hypogonadism. Changes in GNRHR, GNRH1 and DUSP6 mRNA expression were found in most of cases. However variations of mRNA expression were multidirectional in each case and there was no similarity among expression profiles of patients according to amenorrhea type or anamnestic factors.Conclusions. According to our preliminary results, in women with hypogonadotropic hypogonadism the functional activity damage of “reproductive-responsible” genes could be found in each case. Probably mRNA expression measuring could be a perspective method for proving hypothalamo-pituitary level of reproductive disorders and may help to determine which genes should be tested for DNA impairment.