Infection of the germ line by retroviral particles produced in the follicle cells: a possible mechanism for the mobilization of the gypsy retroelement of Drosophila

Development ◽  
1997 ◽  
Vol 124 (14) ◽  
pp. 2789-2798 ◽  
Author(s):  
S.U. Song ◽  
M. Kurkulos ◽  
J.D. Boeke ◽  
V.G. Corces
Keyword(s):  
High Frequency ◽  
Cytoplasmic Membrane ◽  
De Novo ◽  
Germ Line ◽  
High Rate ◽  
Follicle Cells ◽  
Nurse Cells ◽  
Perivitelline Space ◽  
Viral Particles ◽  
Secretory Apparatus

The gypsy retroelement of Drosophila moves at high frequency in the germ line of the progeny of females carrying a mutation in the flamenco (flam) gene. This high rate of de novo insertion correlates with elevated accumulation of full-length gypsy RNA in the ovaries of these females, as well as the presence of an env-specific RNA. We have prepared monoclonal antibodies against the gypsy Pol and Env products and found that these proteins are expressed in the ovaries of flam females and processed in the manner characteristic of vertebrate retroviruses. The Pol proteins are expressed in both follicle and nurse cells, but they do not accumulate at detectable levels in the oocyte. The Env proteins are expressed exclusively in the follicle cells starting at stage 9 of oogenesis, where they accumulate in the secretory apparatus of the endoplasmic reticulum. They then migrate to the inner side of the cytoplasmic membrane where they assemble into viral particles. These particles can be observed in the perivitelline space starting at stage 10 by immunoelectron microscopy using anti-Env antibodies. We propose a model to explain flamenco-mediated induction of gypsy mobilization that involves the synthesis of gypsy viral particles in the follicle cells, from where they leave and infect the oocyte, thus explaining gypsy insertion into the germ line of the subsequent generation.

scholarly journals IR hybrid dysgenesis increases the frequency of recombination in Drosophila melanogaster

1995 ◽  
Vol 65 (3) ◽  
pp. 167-174 ◽  
Author(s):  
Marie-Christine Chaboissier ◽  
Françoise Lemeunier ◽  
Alain Bucheton
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Element ◽  
High Frequency ◽  
Germ Line ◽  
Hybrid Dysgenesis ◽  
High Rate ◽  
I Factor

SummaryThe I factor is a LINE-like transposable element responsible for the I-R system of hybrid dysgenesis in Drosophila melanogaster. Inducer strains of this species contain several I factors whereas reactive strains do not. I factors are stable in inducer strains, but transpose at high frequency in the germ-line of females, known as SF females, produced by crossing reactive females and inducer males. Various abnormalities occur in SF females, most of which result from this high rate of transposition. We report here that recombination is increased in the germ-line of these females. This is a new characteristic of the I-R system of hybrid dysgenesis that might also be associated with transposition of the I factor.

scholarly journals Life Cycle of an Endogenous Retrovirus,ZAM, in Drosophila melanogaster

2000 ◽  
Vol 74 (22) ◽  
pp. 10658-10669 ◽  
Author(s):  
P. Leblanc ◽  
S. Desset ◽  
F. Giorgi ◽  
A. R. Taddei ◽  
A. M. Fausto ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Germ Line ◽  
Endogenous Retrovirus ◽  
Follicle Cells ◽  
Yolk Granules ◽  
Vesicular Traffic ◽  
Viral Particles ◽  
Whole Mount ◽  
Small Set

ABSTRACT ZAM is an env-containing member of thegypsy family of retrotransposons that represents a possible retrovirus of invertebrates. In this paper, we tracedZAM mobilization to get information about a potential path a retroelement may take to reach the germ line of its host. In situ hybridization on whole-mount tissues and immunocytochemistry analyses with antibodies raised againstZAM Gag and Env proteins have shown that all components necessary to assemble ZAM viral particles, i.e., ZAM full-length RNAs and Gag and Env polypeptides, are coexpressed in a small set of follicle cells surrounding the oocyte. By electron microscopy, we have shown thatZAM viral particles are indeed detected in this somatic lineage of cells, which they leave and enter the closely apposed oocyte. Our data provide evidence that the vesicular traffic and yolk granules in the process of vitellogenesis play an important role in ZAM transfer to the oocyte. Our data support the possibility that vitellogenin transfer to the oocyte may help a retroelement pass to the germ line with no need of its envelope product.

Different 3′ untranslated regions target alternatively processed hu-li tai shao (hts) transcripts to distinct cytoplasmic locations during Drosophila oogenesis

1999 ◽  
Vol 112 (19) ◽  
pp. 3385-3398 ◽  
Author(s):  
K.L. Whittaker ◽  
D. Ding ◽  
W.W. Fisher ◽  
H.D. Lipshitz
Keyword(s):  
Germ Line ◽  
Protein Isoforms ◽  
Follicle Cells ◽  
Untranslated Regions ◽  
Nurse Cells ◽  
Anterior Pole ◽  
Amino Terminal ◽  
Alternative Processing ◽  
Carboxy Terminal ◽  
Drosophila Ovary

Cytoplasmic mRNA localization is one method by which protein production is restricted to a particular intracellular site. We report here a novel mechanism for localization of transcripts encoding distinct protein isoforms to different destinations. Alternative processing of transcripts produced in the Drosophila ovary by the hu-li tai shao (hts) locus introduces distinct 3′ untranslated regions (3′UTRs) that differentially localize the mRNAs. Three classes of hts mRNA (R2, N32 and N4) are synthesized in the germ line nurse cells and encode proteins with adducin-homologous amino-terminal regions but divergent carboxy-terminal domains. The R2 and N32 classes of mRNA remain in the nurse cells and are not transported into the oocyte. In contrast, the N4 class of transcripts is transported from the nurse cells into the oocyte starting at stage 1, is subsequently localized to the oocyte cortex at stage 8 and then to the anterior pole from stage 9 on. All aspects of N4 transcript transport and localization are directed by the 345-nucleotide(nt)-long 3′ untranslated region (3′UTR). The organization of localization elements in the N4 3′UTR is modular: a 150 nt core is sufficient to direct transport and localization throughout oogenesis. Additional 3′UTR elements function additively together with this core region at later stages of oogenesis to maintain or enhance anterior transcript anchoring. The swallow locus is required to maintain hts transcripts at the anterior pole of the oocyte and functions through the N4 3′UTR. In addition to the three classes of germ line-expressed hts transcripts, a fourth class (R1) is expressed in the somatic follicle cells that surround the germ line cells. This transcript class encodes the Drosophila orthologue of mammalian adducin.

scholarly journals Phagocytosis genes nonautonomously promote developmental cell death in the Drosophila ovary

2016 ◽  
Vol 113 (9) ◽  
pp. E1246-E1255 ◽  
Author(s):  
Allison K. Timmons ◽  
Albert A. Mondragon ◽  
Claire E. Schenkel ◽  
Alla Yalonetskaya ◽  
Jeffrey D. Taylor ◽  
...  
Keyword(s):  
Cell Death ◽  
Large Scale ◽  
Germ Line ◽  
Follicle Cells ◽  
Small Subset ◽  
Nurse Cells ◽  
Cell Death Program ◽  
Cell Death Mechanisms ◽  
Developmental Cell Death ◽  
Drosophila Ovary

Programmed cell death (PCD) is usually considered a cell-autonomous suicide program, synonymous with apoptosis. Recent research has revealed that PCD is complex, with at least a dozen cell death modalities. Here, we demonstrate that the large-scale nonapoptotic developmental PCD in the Drosophila ovary occurs by an alternative cell death program where the surrounding follicle cells nonautonomously promote death of the germ line. The phagocytic machinery of the follicle cells, including Draper, cell death abnormality (Ced)-12, and c-Jun N-terminal kinase (JNK), is essential for the death and removal of germ-line–derived nurse cells during late oogenesis. Cell death events including acidification, nuclear envelope permeabilization, and DNA fragmentation of the nurse cells are impaired when phagocytosis is inhibited. Moreover, elimination of a small subset of follicle cells prevents nurse cell death and cytoplasmic dumping. Developmental PCD in the Drosophila ovary is an intriguing example of nonapoptotic, nonautonomous PCD, providing insight on the diversity of cell death mechanisms.

scholarly journals Frequency of mosaicism points towards mutation-prone early cleavage cell divisions in cattle

2016 ◽  
Author(s):  
Chad Harland ◽  
Carole Charlier ◽  
Latifa Karim ◽  
Nadine Cambisano ◽  
Manon Deckers ◽  
...  
Keyword(s):  
Sperm Cell ◽  
De Novo ◽  
Germ Line ◽  
High Rate ◽  
De Novo Mutation ◽  
Whole Genome ◽  
Early Cleavage ◽  
Cell Divisions ◽  
Premeiotic Clusters ◽  
Males And Females

It has recently become possible to directly estimate the germ-line de novo mutation (dnm) rate by sequencing the whole genome of father-mother-offspring trios, and this has been conducted in human1–5, chimpanzee6, mice7, birds8 and fish9. In these studies dnm’s are typically defined as variants that are heterozygous in the offspring while being absent in both parents. They are assumed to have occurred in the germ-line of one of the parents and to have been transmitted to the offspring via the sperm cell or oocyte. This definition assumes that detectable mosaïcism in the parent in which the mutation occurred is negligible. However, instances of detectable mosaïcism or premeiotic clusters are well documented in humans and other organisms, including ruminants10–12. We herein take advantage of cattle pedigrees to show that as much as ∼30% to ∼50% of dnm’s present in a gamete may occur during the early cleavage cell divisions in males and females, respectively, resulting in frequent detectable mosaïcism and a high rate of sharing of multiple dnm’s between siblings. This should be taken into account to accurately estimate the mutation rate in cattle and other species.

RUNX1 DNA-binding mutations and RUNX1-PRDM16 cryptic fusions in BCR-ABL+ leukemias are frequently associated with secondary trisomy 21 and may contribute to clonal evolution and imatinib resistance

Blood ◽  
2008 ◽  
Vol 111 (7) ◽  
pp. 3735-3741 ◽  
Author(s):  
Catherine Roche-Lestienne ◽  
Lauréline Deluche ◽  
Sélim Corm ◽  
Isabelle Tigaud ◽  
Sami Joha ◽  
...  
Keyword(s):  
Dna Binding ◽  
High Frequency ◽  
Trisomy 21 ◽  
De Novo ◽  
Blast Crisis ◽  
Clonal Evolution ◽  
Chronic Phase ◽  
Chromosome 21 ◽  
Imatinib Resistance ◽  
Molecular Abnormalities

Abstract Acquired molecular abnormalities (mutations or chromosomal translocations) of the RUNX1 transcription factor gene are frequent in acute myeloblastic leukemias (AMLs) and in therapy-related myelodysplastic syndromes, but rarely in acute lymphoblastic leukemias (ALLs) and chronic myelogenous leukemias (CMLs). Among 18 BCR-ABL+ leukemias presenting acquired trisomy of chromosome 21, we report a high frequency (33%) of recurrent point mutations (4 in myeloid blast crisis [BC] CML and one in chronic phase CML) within the DNA-binding region of RUNX1. We did not found any mutation in de novo BCR-ABL+ ALLs or lymphoid BC CML. Emergence of the RUNX1 mutations was detected at diagnosis or before the acquisition of trisomy 21 during disease progression. In addition, we also report a high frequency of cryptic chromosomal RUNX1 translocation to a novel recently described gene partner, PRDM16 on chromosome 1p36, for 3 (21.4%) of 14 investigated patients: 2 myeloid BC CMLs and, for the first time, 1 therapy-related BCR-ABL+ ALL. Two patients presented both RUNX1 mutations and RUNX1-PRDM16 fusion. These events are associated with a short survival and support the concept of a cooperative effect of BCR-ABL with molecular RUNX1 abnormalities on the differentiation arrest phenotype observed during progression of CML and in BCR-ABL+ ALL.

scholarly journals Thymic nurse cells exhibit epithelial progenitor phenotype and create unique extra-cytoplasmic membrane space for thymocyte selection

2010 ◽  
Vol 261 (2) ◽  
pp. 81-92 ◽  
Author(s):  
Tonya M. Hendrix ◽  
Rajendra V.E. Chilukuri ◽  
Marcia Martinez ◽  
Zachariah Olushoga ◽  
Andrew Blake ◽  
...  
Keyword(s):  
Cytoplasmic Membrane ◽  
Nurse Cells ◽  
Thymic Nurse Cells

scholarly journals Epigenetic marking and repression of porcine endogenous retroviruses

2013 ◽  
Vol 94 (5) ◽  
pp. 960-970 ◽  
Author(s):  
Gernot Wolf ◽  
Anders Lade Nielsen ◽  
Jacob Giehm Mikkelsen ◽  
Finn Skou Pedersen
Keyword(s):  
Dna Methylation ◽  
De Novo ◽  
Germ Line ◽  
Mammalian Species ◽  
Histone Deacetylation ◽  
Endogenous Retroviruses ◽  
Primer Binding Site ◽  
Retroviral Transduction ◽  
Embryonic Germ Cells ◽  
Epigenetic Repression

Endogenous retroviruses (ERVs) are remnants of retroviral germ line infections and have been identified in all mammals investigated so far. Although the majority of ERVs are degenerated, some mammalian species, such as mice and pigs, carry replication-competent ERVs capable of forming infectious viral particles. In mice, ERVs are silenced by DNA methylation and histone modifications and some exogenous retroviruses were shown to be transcriptionally repressed after integration by a primer-binding site (PBS) targeting mechanism. However, epigenetic repression of porcine ERVs (PERVs) has remained largely unexplored so far. In this study, we screened the pig genome for PERVs using LTRharvest, a tool for de novo detection of ERVs, and investigated various aspects of epigenetic repression of three unrelated PERV families. We found that these PERV families are differentially up- or downregulated upon chemical inhibition of DNA methylation and histone deacetylation in cultured porcine cells. Furthermore, chromatin immunoprecipitation analysis revealed repressive histone methylation marks at PERV loci in primary porcine embryonic germ cells and immortalized embryonic kidney cells. PERV elements belonging to the PERV-γ1 family, which is the only known PERV family that has remained active up to the present, were marked by significantly higher levels of histone methylations than PERV-γ2 and PERV-β3 proviruses. Finally, we tested three PERV-associated PBS sequences for repression activity in murine and porcine cells using retroviral transduction experiments and showed that none of these PBS sequences induced immediate transcriptional silencing in the tested primary porcine cells.

High-frequency germ line gene conversion in transgenic mice

1992 ◽  
Vol 12 (6) ◽  
pp. 2545-2552
Author(s):  
J R Murti ◽  
M Bumbulis ◽  
J C Schimenti
Keyword(s):  
Gene Conversion ◽  
Dna Sequences ◽  
High Frequency ◽  
Germ Line ◽  
Gene Families ◽  
Histochemical Staining ◽  
Evolutionary Significance ◽  
Evolutionary Divergence ◽  
Lacz Gene ◽  
Male Gametes

Gene conversion is the nonreciprocal transfer of genetic information between two related genes or DNA sequences. It can influence the evolution of gene families, having the capacity to generate both diversity and homogeneity. The potential evolutionary significance of this process is directly related to its frequency in the germ line. While measurement of meiotic inter- and intrachromosomal gene conversion frequency is routine in fungal systems, it has hitherto been impractical in mammals. We have designed a system for identifying and quantitating germ line gene conversion in mice by analyzing transgenic male gametes for a contrived recombination event. Spermatids which undergo the designed intrachromosomal gene conversion produce functional beta-galactosidase (encoded by the lacZ gene), which is visualized by histochemical staining. We observed a high incidence of lacZ-positive spermatids (approximately 2%), which were produced by a combination of meiotic and mitotic conversion events. These results demonstrate that gene conversion in mice is an active recombinational process leading to nonparental gametic haplotypes. This high frequency of intrachromosomal gene conversion seems incompatible with the evolutionary divergence of newly duplicated genes. Hence, a process may exist to uncouple gene pairs from frequent conversion-mediated homogenization.

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