scholarly journals INTERCELLULAR MIGRATION OF CENTRIOLES IN THE GERMARIUM OF DROSOPHILA MELANOGASTER

1970 ◽  
Vol 45 (2) ◽  
pp. 306-320 ◽  
Author(s):  
Anthony P. Mahowald ◽  
Joan M. Strassheim
Keyword(s):  
Follicle Cell ◽  
Cell Cluster ◽  
Follicle Cells ◽  
Oocyte Nucleus ◽  
Nurse Cells ◽  
Serial Sections ◽  
Cell Border ◽  
Ring Canals ◽  
Egg Chambers ◽  
Stage 1

A cluster of centrioles has been found in the early Drosophila oocyte. Since the oocyte is connected to 15 nurse cells by a system of intercellular bridges or ring canals, the possibility that the cluster of centrioles arose in the germarium from an intercellular migration of centrioles from the nurse cells to the oocyte was analyzed in serial sections for the electron microscope. Initially, all of the 16 cells of the future egg chambers possess centrioles, which are located in a juxtanuclear position. At the time the 16 cell cluster becomes arranged in a lens-shaped layer laterally across the germarium, the centrioles lose their juxtanuclear position and move towards the oocyte. By the time the 16 cell cluster of cells is surrounded by follicle cells (Stage 1), between 14 and 17 centrioles are found in the oocyte. Later, these centrioles become located between the oocyte nucleus and the follicle cell border and become aggregated into a cluster less than 1.5 µ in its largest dimension. The fate of these centrioles in the oocyte is not known. The fine structure of the germarium and the early oocyte is also described.

An ultrastructural study of ovarian development in the otu7 mutant of Drosophila melanogaster

1984 ◽  
Vol 67 (1) ◽  
pp. 87-119
Author(s):  
D.L. Bishop ◽  
R.C. King
Keyword(s):  
Polytene Chromosomes ◽  
Vital Role ◽  
Follicle Cells ◽  
Vitelline Membrane ◽  
Nurse Cells ◽  
Border Cells ◽  
Stage Of Development ◽  
Ring Canals ◽  
Egg Chambers ◽  
Reduced Rate

Females homozygous for the otu7 allele produce ovarian tumours, as well as egg chambers that reach a relatively late stage of development. Mutant ovarian nurse cells contain giant polytene chromosomes. These are transcriptionally active, and RNA is transported to the oocyte through ring canals, although at reduced rate. Vitellogenic oocytes are endocytotically active. Protein (alpha yolk) spheres are formed, but glycogen (beta yolk) spheres were never seen in the ooplasm. Follicle cells migrate normally and secrete more vitelline membrane and chorion than is required to cover the slowly growing oocyte. Specialized follicle cells also secrete relatively normal dorsal appendages. The micropylar cone is secreted by another cluster of specialized follicle cells called border cells. These are out of phase with the oocyte, and the forming micropylar cone prevents the nurse cells from passing the remainder of their cytoplasm to the oocyte. The result is a morphologically abnormal chamber blocked at the p-12 stage. Sections through the micropylar cone of a p-12 chamber demonstrated that one of the border cells formed a projection containing a bundle of microtubules. Secretions of the border cells were deposited against this tube, which later degenerates or is withdrawn. Normally this results in a canal, the micropyle, through which the sperm enters the egg. The slowed growth of the mutant oocyte presumably results from a defect in the transport of fluids or charged molecules to it, and the otu+ gene is therefore believed to play a vital role in this process.

Follicle cell bridges in the mosquito ovary: syncytia formation and bridge morphology

1978 ◽  
Vol 31 (1) ◽  
pp. 137-143
Author(s):  
A. Fiil
Keyword(s):  
Culex Pipiens ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Nurse Cells ◽  
Serial Sections ◽  
Intercellular Bridges ◽  
Syncytia Formation

In the mosquito, Culex pipiens quinqefasciatus, the follicle cells enveloping the oocyte and the nurse cells are connected by intercellular bridges. The bridges are formed by incomplete cytokinesis, and they persist for more than 30 h after their formation. Reconstructions from serial sections showed that one syncytial group contained at least 32 cells; several cells continued outside the series. The cells in a syncytium divide asynchronously; this results in an irregular, branched orgainzation. The bridges may be either embedded in the cytoplasm of the cells, or they may form an extracellular connexion.

A targeted gene silencing technique shows that Drosophila myosin VI is required for egg chamber and imaginal disc morphogenesis

1999 ◽  
Vol 112 (21) ◽  
pp. 3677-3690 ◽  
Author(s):  
W. Deng ◽  
K. Leaper ◽  
M. Bownes
Keyword(s):  
Gene Silencing ◽  
Imaginal Disc ◽  
Developmental Stages ◽  
Expression System ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Myosin Vi ◽  
Nurse Cells ◽  
Cell Shapes ◽  
Egg Chamber

We report that Drosophila unconventional myosin VI, encoded by Myosin heavy chain at 95F (Mhc95F), is required for both imaginal disc and egg chamber morphogenesis. During oogenesis, Mhc95F is expressed in migrating follicle cells, including the border cells, which migrate between the nurse cells to lie at the anterior of the oocyte; the columnar cells that migrate over the oocyte; the centripetal cells that migrate between the oocyte and nurse cells; and the dorsal-anterior follicle cells, which migrate to secrete the chorionic appendages. Its function during development has been studied using a targeted gene silencing technique, combining the Gal4-UAS targeted expression system and the antisense RNA technique. Antibody staining shows that the expression of myosin 95F is greatly decreased in follicle cells when antisense Mhc95F RNA is expressed. Interfering with expression of Drosophila myosin VI at various developmental stages frequently results in lethality. During metamorphosis it results in adult flies with malformed legs and wings, indicating that myosin VI is essential for imaginal disc morphogenesis. During oogenesis, abnormal follicle cell shapes and aberrant follicle cell migrations are observed when antisense Mhc95F is expressed in follicle cells during stages 9 to 10, suggesting that the Drosophila myosin VI is required for follicle cell epithelial morphogenesis.

Laser ablation studies of the role of the Drosophila oocyte nucleus in pattern formation

Science ◽  
1991 ◽  
Vol 254 (5029) ◽  
pp. 290-293
Author(s):  
DJ Montell ◽  
H Keshishian ◽  
AC Spradling
Keyword(s):  
Laser Ablation ◽  
Pattern Formation ◽  
Posterior Pole ◽  
Follicle Cells ◽  
Oocyte Nucleus ◽  
Dorsoventral Patterning ◽  
Egg Chambers ◽  
Germline Cells

Somatic and germline cells interact during oogenesis to establish the pattern axes of the Drosophila eggshell and embryo. The role of the oocyte nucleus in pattern formation was tested with the use of laser ablation. Ablation in stage 6 to 9 egg chambers caused partial or complete ventralization of the eggshell, phenotypes similar to those of eggs produced by gurken or torpedo females. Accumulation of vasa protein at the posterior pole of treated oocytes was also disrupted. Thus the oocyte nucleus is required as late as stage 9 for dorsoventral patterning within the follicle cells and for polar plasm assembly in the oocyte.

scholarly journals fs (1) Yb is required for ovary follicle cell differentiation in Drosophila melanogaster and has genetic interactions with the Notch group of neurogenic genes.

Genetics ◽  
1995 ◽  
Vol 140 (1) ◽  
pp. 207-217 ◽  
Author(s):  
E Johnson ◽  
S Wayne ◽  
R Nagoshi
Keyword(s):  
Cell Fate ◽  
Ovarian Follicle ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Female Sterility ◽  
Specific Factor ◽  
Temperature Sensitive ◽  
Egg Maturation ◽  
Egg Chambers ◽  
Mutant Phenotypes

Abstract Phenotypic and genetic analyses demonstrate that fs (1) Yb activity is required in the soma for the development of a subset of ovarian follicle cells and to support later stages of egg maturation. Mutations in fs (1) Yb cause a range of ovarian phenotypes, from the improper segregation of egg chambers to abnormal dorsal appendage formation. The mutant phenotypes associated with fs (1) Yb are very similar to the ovarian aberrations produced by temperature-sensitive alleles of Notch and Delta. Possible functional or regulatory interactions between fs (1) Yb and Notch are suggested by genetic studies. A duplication of the Notch locus partially suppresses the female-sterility caused by fs (1) Yb mutations, while reducing Notch dosage makes the fs (1) Yb mutant phenotype more severe. In addition, fs (1) Yb alleles also interact with genes that are known to act with or regulate Notch activity, including Delta, daughterless, and mastermind. However, differences between the mutant ovarian phenotype of fs (1) Yb and that of Notch or Delta indicate that the genes do not have completely overlapping functions in the ovary. We propose that fs (1) Yb acts as an ovary-specific factor that determines follicle cell fate.

Oogenesis in Lucilia Cuprina (Wied.) (Diptera: Calliphoridae). I. Development of Nurse Cell Nuclei, the Oocyte Nucleus and the Follicle Cells.

1979 ◽  
Vol 27 (3) ◽  
pp. 331 ◽  
Author(s):  
GAC Beattie ◽  
J Cheney
Keyword(s):  
Nurse Cell ◽  
Early Stage ◽  
Chromosomal Rearrangements ◽  
Polytene Chromosomes ◽  
Average Diameter ◽  
Lucilia Cuprina ◽  
Follicle Cells ◽  
Oocyte Nucleus ◽  
Cell Nuclei ◽  
Stage 1

In investigations in the laboratory in Australia, endomitosis in the ovarian nurse cell nuclei in females of Lucilia cuprina (Wied.) was found to be initiated in stage-1 follicles shortly after eclosion, independently of a protein meal. The largest nurse cell nuclei attained a ploidy of 1024n in stage 3 and 4 follicles, shortly after the onset of vitellogenesis; after this, they could undergo a further eightfold increase in volume. Polytene chromosomes were occasionally observed during endomitosis in 16n and 32n nurse cell nuclei. Throughout stages 1-8, the oocyte nucleus steadily increased from an average diameter of 6-7 mu m to one of about 60 mu m. In early stage 9, the nuclear membrane was lost and what appeared to be a karyosphere with a diameter of about 6 mu m was visible. Later in stage 9, the oocyte nucleus was obscured by yolk, and its development beyond this stage was not traced. Follicle cells increased in number from 80 in early stage-1 follicles to 1300 in stage 2. The information presented was required to ascertain the site of action of aziridinyl chemosterilants on ovarian development [see next abstract] and to aid in current research on the production of chromosomal rearrangements by irradiation.

Drosophila puckered regulates Fos/Jun levels during follicle cell morphogenesis

Development ◽  
2001 ◽  
Vol 128 (10) ◽  
pp. 1845-1856 ◽  
Author(s):  
L.L. Dobens ◽  
E. Martin-Blanco ◽  
A. Martinez-Arias ◽  
F.C. Kafatos ◽  
L.A. Raftery
Keyword(s):  
Nurse Cell ◽  
Ectopic Expression ◽  
Follicle Cell ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Drosophila Embryo ◽  
Follicle Cells ◽  
Cell Morphogenesis ◽  
Jnk Pathway ◽  
Egg Chambers

puckered (puc) encodes a VH1-like phosphatase that down-regulates Jun kinase (JNK) activity during dorsal closure of the Drosophila embryo. We report a role for puc in follicle cell morphogenesis during oogenesis. puc mRNA accumulates preferentially in the centripetally migrating follicle cells and cells of the elongating dorsal appendages. Proper levels of Puc activity in the follicle cells are critical for the production of a normal egg: either reduced or increased Puc activity result in incomplete nurse cell dumping and aberrant dorsal appendages. Phenotypes associated with puc mutant follicle cells include altered DE-cadherin expression in the follicle cells and a failure of nurse cell dumping to coordinate with dorsal appendage elongation, leading to the formation of cup-shaped egg chambers. The JNK pathway target A251-lacZ showed cell-type-specific differences in its regulation by puc and by the small GTPase DRac1. puc mutant cells displayed region-specific ectopic expression of the A251-lacZ enhancer trap whereas overexpression of a transgene encoding Puc was sufficient to suppress lacZ expression in a cell autonomous fashion. Strikingly, decreased or increased puc function leads to a corresponding increase or decrease, respectively, of Fos and Jun protein levels. Taken together, these data indicate that puc modulates gene expression responses by antagonizing a Ρ GTPase signal transduction pathway that stabilizes the AP-1 transcription factor. Consistent with this, overexpression of a dominant negative DRac1 resulted in lower levels of Fos/Jun.

Encore, a gene required for the regulation of germ line mitosis and oocyte differentiation during Drosophila oogenesis

Development ◽  
1996 ◽  
Vol 122 (1) ◽  
pp. 281-290 ◽  
Author(s):  
N.C. Hawkins ◽  
J. Thorpe ◽  
T. Schupbach
Keyword(s):  
Germ Line ◽  
Oocyte Nucleus ◽  
Temperature Sensitive ◽  
Nurse Cells ◽  
Multiple Alleles ◽  
Drosophila Oogenesis ◽  
Isolation And Characterization ◽  
Egg Chambers ◽  
Bag Of Marbles ◽  
Oocyte Differentiation

During Drosophila oogenesis, a stem cell daughter undergoes precisely four rounds of mitosis to generate a cyst of 16 cells interconnected by cytoplasmic bridges. One of the cells becomes the oocyte while the remaining 15 cells differentiate as nurse cells. We hve identified a gene, encore, that is involved both in regulating the number of germline mitoses and in the process of oocyte differentation. Mutations in encore result in exactly one extra round of mitosis in the germline. Genetic and molecular studies indicate that this mitotic defect may be mediated through the gene bag-of-marbles. The isolation and characterization of multiple alleles of encore revealed that they were all temperature sensitive for this phenotype. Mutations in encore also affect the process of oocyte differentiation. Egg chambers are produced in which the oocyte nucleus has undergone endoreplication often resulting in the formation of 16 nurse cells. We argue that these two phenotypes produced by mutations in encore represent two independent requirements for encore during oogenesis.

Regulation of cell proliferation and patterning in Drosophila oogenesis by Hedgehog signaling

Development ◽  
2000 ◽  
Vol 127 (10) ◽  
pp. 2165-2176 ◽  
Author(s):  
Y. Zhang ◽  
D. Kalderon
Keyword(s):  
Hedgehog Signaling ◽  
Developmental Stages ◽  
Somatic Cells ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Cell Lineages ◽  
Egg Chambers ◽  
Hh Signaling ◽  
Egg Chamber ◽  
Activity Loss

The localized expression of Hedgehog (Hh) at the extreme anterior of Drosophila ovarioles suggests that it might provide an asymmetric cue that patterns developing egg chambers along the anteroposterior axis. Ectopic or excessive Hh signaling disrupts egg chamber patterning dramatically through primary effects at two developmental stages. First, excess Hh signaling in somatic stem cells stimulates somatic cell over-proliferation. This likely disrupts the earliest interactions between somatic and germline cells and may account for the frequent mis-positioning of oocytes within egg chambers. Second, the initiation of the developmental programs of follicle cell lineages appears to be delayed by ectopic Hh signaling. This may account for the formation of ectopic polar cells, the extended proliferation of follicle cells and the defective differentiation of posterior follicle cells, which, in turn, disrupts polarity within the oocyte. Somatic cells in the ovary cannot proliferate normally in the absence of Hh or Smoothened activity. Loss of protein kinase A activity restores the proliferation of somatic cells in the absence of Hh activity and allows the formation of normally patterned ovarioles. Hence, localized Hh is not essential to direct egg chamber patterning.

Oocyte determination and the origin of polarity in Drosophila: the role of the spindle genes

Development ◽  
1997 ◽  
Vol 124 (24) ◽  
pp. 4927-4937 ◽  
Author(s):  
A. Gonzalez-Reyes ◽  
H. Elliott ◽  
D. St Johnston
Keyword(s):  
Symmetry Breaking ◽  
Germinal Vesicle ◽  
Follicle Cells ◽  
Axis Formation ◽  
Main Body ◽  
Nurse Cells ◽  
Egg Chambers ◽  
Anterior Posterior ◽  
Oocyte Selection

The two main body axes in Drosophila become polarised as a result of a series of symmetry-breaking steps during oogenesis. Two of the sixteen germline cells in each egg chamber develop as pro-oocytes, and the first asymmetry arises when one of these cells is selected to become the oocyte. Anterior-posterior polarity originates when the oocyte then comes to lie posterior to the nurse cells and signals through the Gurken/Egfr pathway to induce the adjacent follicle cells to adopt a posterior fate. This directs the movement of the germinal vesicle and associated gurken mRNA from the posterior to an anterior corner of the oocyte, where Gurken protein signals for a second time to induce the dorsal follicle cells, thereby polarising the dorsal-ventral axis. Here we describe a group of five genes, the spindle loci, which are required for each of these polarising events. spindle mutants inhibit the induction of both the posterior and dorsal follicle cells by disrupting the localisation and translation of gurken mRNA. Moreover, the oocyte often fails to reach the posterior of mutant egg chambers and differentiates abnormally. Finally, double mutants cause both pro-oocytes to develop as oocytes, by delaying the choice between these two cells. Thus, these mutants reveal a novel link between oocyte selection, oocyte positioning and axis formation in Drosophila, leading us to propose that the spindle genes act in a process that is common to several of these events.

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