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Mouse vas deferens protein (MVDP) is a major androgen-dependent protein of deferential fluid. It is specifically expressed in the epithelium of the mouse vas deferens. Its amino acid sequence as deduced from the nucleotidic sequence of its cDNA does not possess a signal sequence characteristic of secretory proteins. In vitro, transcription of MVDP cDNA followed by translation of mRNA in the rabbit reticulocyte system, in the absence or the presence of microsomes, demonstrated that there was no internalization of MVDP into microsomes that could protect it from degradation by proteinase K; this confirmed the absence of signal sequence. Moreover, MVDP has its NH2-terminus blocked. To understand how MVDP can be exported, its ultrastructural distribution and secretion process were analyzed by means of electron microscopy. Immunolocalization of MVDP revealed that it was distributed in the whole cytoplasm; it was never detected in the lumen of endoplasmic reticulum, Golgi apparatus, or vesicles but was abundant in apical protrusions and in the fluid, where it was associated with cellular material undergoing degradation. These data clearly demonstrated that exportation of MVDP into the luminal fluid does not occur in the classical manner for secretory proteins but rather involves an apocrine secretion process.

The endogenous retrovirus gypsy is controlled by the Drosophila gene flamenco (flam). New insertions of gypsy occur in any individual Drosophila if its mother is homozygous for the flam 1 permissive allele and contains functional gypsy proviruses. The ovaries of flam 1 females also contain high amounts of gypsy RNAs. Unexpectedly however, gypsy derepression does not occur in the flam 1 female germline proper but in the somatic follicular epithelium of the ovary. Since extracts from these females are able to efficiently infect the germ-line of a strain devoid of active gypsy proviruses, we assume that a similar kind of germ-line infection, which would occur inside the flam 1 females themselves, could be required for gypsy insertions to occur in their IntroductionA unique feature of retroviruses is their ability to exist both\either as exogenous viruses which, like classical viruses are propagated by horizontal infection, and\or as endogenous viruses which are transmitted vertically in the germ-line where they may behave as reasonably stable Mendelian genes (Coffin, 1990 ;Lower et al., 1996). Endogenous proviruses may account for as much as 1 % of the entire genome of Drosophila (Bucheton, 1995), mice (Varmus & Brown, 1989) and humans (Lower et al., 1996). They are considered to arise from occasional infections of the germ-line by exogenous retroviruses.However, the manner in which endogenous proviruses gain entry to the germ-line and the mechanisms by which they increase in number (virus replication cycle and\or intracellular progeny. This hypothesis was confirmed by electron microscopy observations showing that non-enveloped intracytoplasmic particles containing gypsy RNAs accumulate in the apical region of the flam 1 follicle cells, close to specific membrane domains to which the gypsy envelope proteins are targeted, whereas both are absent in the flam M controls. Low amounts of similar virus-like particles were also observed in flam 1 oocytes, but it is not yet known whether they entered passively or as a result of membrane fusion. This is the first report of the beginning of a retrovirus cycle in invertebrates and these observations should be taken into account when explaining the maternal effect of the flamenco gene on the multiplication of gypsy proviruses. transposition) are still unknown because very few model systems have been amenable to full genetic and molecular analysis. For instance, the acquisition by mice of new germ-line C-type proviruses is generally quite a rare event (Coffin, 1990) and, although the frequency of this event could be shown to depend greatly upon the genotype of the host strain, the mouse gene(s) involved have not yet been isolated (Bautch, 1986 ;Spence et al., 1989). The recent discovery that gypsy endogenous retrovirus apparently interacts in the same way with its Drosophila host might serve as a useful model in this respect (Bucheton, 1995).Like vertebrate endogenous retroviruses, gypsy is transmitted vertically as a small number (usually fewer than five) of functional proviru...

The karyotypes of 4 european species of Lacertidae were determined in hepatic tissue cultures. The chromosomal formula typical of the Lacertidae (2n = 36M + 2 m) was found in L. muralis, L. sicula campestris and L. viridis; no morphologically differentiated sex chromosomes were identified in these 3 species.A population of L. vivipara caught in the Massif Central (France) shows the following diploid number: 2n~?=32A+Za Z~ W, 2nd=32A+Z~ Z~ Z2Z2. The existence of the submetacentric W in the female karyotype can be explained by centric fusion between two non homologous telocentric chromosomes. It is possible that only some populations show this rearrangement.The finding of two types of heterogamety, XY and ZW, in the same Order contributes to our knowledge of the evolution of sex chromosomes among Vertebrates.

Eighty percent of DNA molecules are deleted in the mitochondrial population of an adult mutant strain of D. subobscura. Both intact and deleted genomes are autonomous monomers. The heteroplasmy level, which is lower in germ tissue, increases from the oocytes (60%) to the third larval instar (83%), and is then maintained throughout the life of the fly. The mtDNA/nuclear DNA ratio is on average two-times greater in the heteroplasmic strain than in the wild-type strain, irrespective of the stage, but the cellular content of mitochondria is elevated only in the embryos and pupae of the mutant strain. The steady state concentrations (SSCs) of the transcripts affected by the deletion are greatly reduced at the larval and adult stages, and less so at the pupal stage of the mutant strain compared with the wild-type. The SSCs of these transcripts are identical in the two strains at the embryonic stage. The fusion transcript, indicating that the deleted genome is expressed, was detected at all stages. The mechanisms involved in the changes in the heteroplasmy level during the course of development and in its maintenance from the third larval instar onwards are discussed.

The changes in distribution and density of mitochondria and the level of mitochondrial RNA during Drosophila oogenesis were studied simultaneously in the 3 cell types ie follicle cells, nurse cells and oocyte, making up the egg chamber. Up to stage 6, mitochondrial density (mitochondrial and cellular areas ratio) was elevated and increased similarly in both follicle and nurse cells. Thereafter the mitochondrial density of follicle cells continued to increase and that of the nurse cells declined markedly while the nurse cell mitochondria assembled in dense groups and decreased in size. This can be related to a transfer of nurse cell cytoplasm, including mitochondria, to the oocyte. In the oocyte from stage 4 to stage 7 we observed a significant decrease of the mitochondrial density due to the absence of mitochondrial biogenesis. Then the cytoplasm transfer caused mitochondrial density to increase up to the level found in the nurse cells at the end of oogenesis. The mature oocyte contains enough mitochondria to supply 15,000 somatic cells. Our results strongly suggest that the variations in size, distribution and density of mitochondria relate to the particular energetic requirements of the different cell types during the first half of oogenesis. Later they relate to the developmental requirements of the nurse cells and the oocyte, in particular the storage of mitochondria in the oocyte. The level of mitochondrial RNA was studied through in situ hybridization. Throughout oogenesis the follicle and nurse cell RNA evolved similarly. Up to stage 9, there was no change in RNA densities in these cells, suggesting a correlation with the cell volume and/or the nuclear DNA content. Thereafter the cellular RNA concentration declined rapidly. In the oocyte the RNA concentration evolved differently especially from stage 10 to the end, the RNA density being stabilized. This can be related to the injection of nurse cell mitochondria, followed by their assignment to reserve status. Our results suggest that the mt RNA density is under extramitochondrial control mechanisms.

Abstract:The monoclonal antibody 21E7-B12

A mutant strain of Drosophila subobscura possesses two mitochondrial genome types: a minority population (20%) identical to the wild strain mtDNA (15.9 kb), and a largely predominant population (80%) of shorter genomes (10.9 kb), presenting a deletion of more than 30% of its coding region. Study of tissular distribution of heteroplasmy shows it to be identical--about 80%--in the head (nervous tissue) and thorax (muscles). On the other hand, a lower percentage (64%) is observed in the ovaries. The strain is apparently unaffected despite this massive loss of genes, coding for four tRNA and for complex I and III subunits. Contrary to observations of similar situations in man, the mutant strain shows no accumulation or structurally abnormal mitochondria. Furthermore, cytochemical studies fail to detect mitochondria devoid of cytochrome oxidase activity (COX-). Finally, mitoribosome populations are identical in mitochondria from both strains. These results suggest that, in the mutant strain, there are no mitochondria containing deleted genomes only: heteroplasmy would thus be intramitochondrial.