Studies of fs(1)1621, a mutation producing ovarian tumors in Drosophila melanogaster

The ethyl methane sulfonate-induced mutation, fs(1)1621, resides at 11.7 on the genetic map and within segment 4F1-5A1 of the cytological map of the X chromosome. When homozygous, fs(1)1621 renders females semisterile but has no effect on their viability; nor does it affect the viability or fertility of hemizygous males. Heterozygous females are fertile and have cytologically normal ovaries. The ovaries of homozygous females first produce normal oocytes, which, if fertilized, can develop into adult males or females. After this period, ovarian chambers containing only pseudonurse cells are formed, and finally mutant germaria produce only tumors. These contain hundreds to thousands of cells that appear to be derived from germarial cystocytes, because they occasionally form clones of interconnected cells and also can differentiate into endopolyploid pseudonurse cells. Raising the temperature speeds the rate at which tumors form; lowering it increases the probability of pseudonurse cell differentiation. Df(1)C159 includes fs(1)1621. The pattern of ovarian chamber production is more temperature sensitive in hemizygous females than in homozygous ones. The morphology of hemizygous tumors and the number of dividing cells within them also differ from homozygotes. These observations support the hypothesis that fs(1)1621 is producing a product, that less is produced by one gene than by two, and that the product plays a role in the mitosis and cytokinesis of ovarian cystocytes.     

Determination of DNA content in the nurse and follicle cells from wild type and mutant Drosophila melanogaster by DNA-Feulgen cytophotometry

DNA replication patterns in the nurse and follicle cells of wild type and a female sterile mutant, fs(1)1304, of Drosophila melanogaster have been studied by DNA-Feulgen cytophotometry, using a cell dispersal technique that allowed the measurement of DNA amounts in individual nuclei from egg chambers of known developmental stages. DNA-Feulgen values associated with various ovarian nuclei from egg chambers at different stages of development were used to assess a base line DNA content for ovarian tissues and to estimate the extent of DNA replication in the nurse cells and follicle cells of growing and mature egg chambers. Our data show that both the nurse and follicle cells undergo multiple cycles of endonuclear DNA replication and that there may be selective amplification as well as underreplication by portions of the genome in these highly polyploid, ovarian cells. Alternative models are proposed to account for the DNA replication patterns observed. Comparisons of DNA-Feulgen levels in wild type ovarian nuclei with those found for the fs(1)1304 mutant and its heterozygote in the balanced stock fs/FM3, show that equivalent DNA levels are present in follicle cell nuclei from all three types of females. Nurse cell nuclei in the homozygous fs stock, however, fail to achieve the same high DNA levels observed in both fs/FM3 and wild type nurse cell nuclei. Although the nuclei of follicle cells in ovaries from fs/fs females appear morphologically like those surrounding egg chambers in wild type ovaries, nurse cell nuclei from mutant females show a more compacted organization of their chromatin than found for nurse cell nuclei from wild type ovaries at similar developmental stages. Our findings suggest that a major effect of the fs(1)1304 mutation may be on the coiling behavior of chromatin and the conformation of DNA-protein moieties in both nurse cell and follicle cell nuclei. These changes in chromatin structure apparently are manifest by perturbations in DNA replication patterns and normal gene function in these biosynthetically active cells.     

Oogenesis in four species of Piscicola (Hirudinea, Rhynchobdellida)

Piscicola has a pair of elongated sac-shaped ovaries. Inside the ovaries are numerous small somatic cells and regularly spherical egg follicles. Each follicle is composed of three types of cells: many (average 30) germ cells (cystocytes) interconnected by intercellular bridges in clones (cysts), one intermediate cell, and three to five outer follicle cells (envelope cells). Each germ cell in a clone has one intercellular bridge connecting it to the central anucleate cytoplasmic mass, the cytophore. Each cluster of germ cells is completely embedded inside a single huge somatic follicle cell, the intermediate (interstitial) cell. The most spectacular feature of the intermediate cell is its development of a system of intracytoplasmic canals apparently formed of invaginations of its cell membrane. Initially the complex of germ cell cluster + intermediate cell is enclosed within an envelope composed of squamous cells. As oogenesis progresses the envelope cells gradually degenerate. All the germ cells that have terminated their mitotic divisions are of similar size and enter meiotic prophase, but one of the cystocytes promptly starts to grow faster and differentiates into the oocyte, whereas the remaining cystocytes withdraw from meiosis and become nurse cells (trophocytes). Numerous mitochondria, ER, and a vast amount of ribosomes are transferred from the trophocytes via the cytophore toward the oocyte. Eventually the oocyte ingests all the content of the cytophore, and the trophocytes degenerate. Little vitellogenesis takes place; the oocyte gathers nutrients in the form of small lipid droplets. At the end of oogenesis, an electron-dense fibrous vitelline envelope appears around the oocyte, among short microvilli. At the same time, electron-dense cortical granules occur in the oocyte cortical cytoplasm; at the end of oogenesis they are numerous, but after fertilization they disappear from the ooplasm. In the present article we point out many differences in the course of oogenesis in two related families of rhynchobdellids: piscicolids and glossiphoniids.     

Morphological Oogenesis in the out1 Mutant of Drosophila melanogaster Meigen (Diptera: Drosophilidae)

ABSTRACT The sex-linked, recessive otu¹ mutant of Drosophila melanogaster was studied cytologically to reveal the effect of the otu gene mutation on oogenesis. Consequently, the germarium of the otu¹ mutant was found to be larger as compared to the normal fertile one and contains many undifferentiated tumor cells resembling cystocytes. Each ovary consists of three types of ovarioles; ovarioles with only a germarium, ovarioles with a germarium and one tumor chamber, and ovarioles with a germarium and two tumor chambers. In the otu¹ germarium, the mesodermal follicle cells invade the clusters of different number of tumor cells at the posterior region of the germarium in order to make the tumor chamber and the dividing frequency of the tumor cells in the first tumor chamber was six times more than in the second tumor chamber. Follicle cells surrounding the tumor chamber are morphologically normal, but the number of the follicle cells becomes less as the tumor chambers move down contrary to the fertile one. The otu¹ mutant female never lays the egg and the formation of the vitelline membrane is incomplete. The otu¹ mutant tumor cells also showed characteristics of certain rapidly dividing cells and its nucleus is lobulated.     

Fs(1)yb Is Required for Ovary Follicle Cell Differentiation in Drosophila Melanogaster and Has Genetic Interactions with the Notch Group of Neurogenic Genes

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.     

Ovarian pathologies generated by various alleles of the otu locus in Drosophila melanogaster

A comparative cytological study was made of oogenesis in flies carrying various mutant alleles of the female sterile gene otu. It resides at 22.7 on the genetic map and within subdivision 7F of the cytological map of the X-chromosome. Each of the five ethyl methane sulfonate-induced mutations observed falls into one of three classes. In class 1, most mutant ovarioles lack germ cells; in class 2, most mutant ovarioles contain tumorous chambers; and in class 3 mutants, chambers occur that possess defective oocytes. The otu² allele belongs to class 1; otu¹ to class 2; and otu³, otu⁴, and otu⁵ to class 3. The mutations have no effects upon female viability or upon the viability and fertility of hemizygous males. Heterozygous females are fertile and have cytologically normal ovaries. In otu⁵ homozygotes, all ovarioles contain egg chambers, but oogenesis is prematurely terminated to produce a pseudo-stage 12 oocyte. Ovarioles from otu³ and from otu⁴ homozygotes contain both ovarian tumors and oocytes. Pseudonurse cells (PNC), which are cystocytes that have stopped dividing and have entered the nurse cell mode of development, are also abundant. PNCs contain polytene chromosomes. Since the homologs are paired, each nucleus has the haploid number of chromosomes. In chambers lacking an oocyte, the number of PNCs is less than the normal number of nurse cells. In chambers containing an oocyte, the number of accompanying nurse cells may be 15, or above or below normal. In vitellogenic chambers, the chromosomes in the nurse cells connected directly to the oocyte are more expanded than those in more distant nurse cells. The KA14 deficiency lacks the plus allele of otu. KA14 heterozygotes are fertile and have cytologically normal ovaries. When females carry KA14 and otu¹, otu³, otu⁴, or otu⁵, 80% of their ovarioles are agametic. When females carry otu² and one of the other mutant alleles, the ovarioles proceed further in development. So otu² produces a product that has a beneficial effect on the test allele. When two different otu alleles are combined in a single fly, the phenotype of the hybrid ovary usually most resembles that of the ovary homozygous for the “stronger” allele (the otu mutant that allows oogenesis to proceed farthest). The results indicate that the product of the otu⁺ locus functions at least three different times during oogenesis; first to permit oogonia to proliferate, second to control the division and differentiation of germarial cystocytes, and third to facilitate the normal growth of the ooplasm. The gene product appears to be required in higher concentrations at each developmental period. The lesions produced by the mutations are thought to interfere with the stability or functioning of the gene product, and the ovarian phenotype produced by a given genotype depends upon the concentration of functional gene product available to the germ cells.     

The origin and early differentiation of the egg chamber of Drosophila melanogaster

The egg chamber of Drosophila melanogaster consists of 16 interconnected cells surrounded by a monolayer of follicle cells. Each 16 cell cluster (from which the oocyte and 15 nurse cells differentiate) arises within the germarial region of an ovariole. To study the ultrastructure of the early stages in the formation and differentiation of egg chambers, a three dimensional reconstruction was made from serial thin sections through a germarium from a 24-hour old, virgin female. The germarium was found to be subdivided into three regions: (1) The mitotically active area where clusters of 16 cells originate from a series of cystocyte divisions, (2) the region where these cells interact with mesodermal cells, and (3) the region where the germarial cyst is transformed into the first egg chamber in the vitellarium. Since cystocytes were found to decrease in size with each division, the possibility exists that cell size may determine when the divisions cease. Models are presented which mimic with varying degrees of success the developmental changes the germarial cells undergo with time. Hypothesis are developed to explain why stem line oogonia are restricted to the anterior portion of the germarium, why mesodermal cells first interact with cystocytes in region 2, and why the oocyte is oriented posteriorly. The nuclear differentiations of the component cells of the chamber are described and correlated with observed differences in radiosensitivity. Symbionts were observed in the germaria of several strains of Drosophila, and the bearing of these findings upon nutritional studies is discussed.     

Abnormal vitelline envelope induced by unphysiological doses of ecdysterone in Aedes aegypti

ABSTRACT. The oocytes of 3-day-old unfed Aedes aegypti mosquitoes are in a state of oogenic arrest, but microgram doses of ecdysterone stimulate their accumulation of a variable amount of yolk. We now find that these doses also induce the deposition of plaques of vitelline envelope by the follicle cells, and with transmission electron microscopy we have compared their formation with that in normal blood-fed females. Plaques in the experimental animals were abnormally large and irregular in shape and distribution. In part, these abnormalities were attributable to the fact that the follicle cells remain in close contact with the oocyte, whereas the space between follicle cells and oocyte increase significantly in the blood-fed female. Deposition of the plaques occurred earliest after the injection of 5 μg ecdysterone, but even at this high dose the amount of plaque material deposited was less than in the blood-fed controls. Induction of the deposition of abnormal vitelline envelope in unfed females was most clearly demonstrated after two injections, 1 μg ecdysterone each, 14h apart; 24h after the second injection, the plaques had prematurely fused into a thin disorganized envelope. When females were injected with ecdysterone immediately after a blood-meal, vitelline envelope plaques formed prematurely, and their structure became increasingly abnormal with time. This early onset of activity was characteristic of follicle cells adjacent both to the oocyte and to nurse cells. Thus, the factors that normally control the formation and organization of the vitelline envelope are absent in the unfed female stimulated with high doses of ecdysterone, while in the blood-fed females, excessive ecdysterone apparently interferes with the timing and orderly sequence of envelope formation.     

Morphogenetic deficiencies in transplanted gonadal anlagen of the mutant l(3)pl (lethal-polyploid) in Drosophila hydei

Larval gonads of Drosophila hydei, homozygous for the lethal gene l(3)pl (lethal-polyploid), were cultured in normal hosts. Ovaries of the late third larval instar were implanted into metamorphosing larvae. These can attach to the gonoduct system of the host and transform into adult ovarian structures but the spectrum of their capacity to differentiate varies largely. In favourable cases mature oocytes can be formed which are fertile. More frequently mitotic disturbances in the follicle cells and cystocytes lead to the formation of abortive egg chambers and abnormally shaped oocytes. Testes of the middle third larval instar were cultured for 2 weeks in adult females. Primary spermatocytes are able to sustain meiotic divisions and form early spermatids, even though the occurrence of fractionated nuclei in post-meiotic germ cells indicates defective meiotic divisions. Post-meiotic differentiation is blocked in mutant spermatids which fail to elongate. The mutant gene l(3)pl thus, not only affects cell divisions, but also interacts in certain cytodifferentiation processes such as spermatid elongation and egg shaping. All cellular processes found so far to be abnormal in mutant tissues involve microtubular function. This suggests that the gene l(3)pl interacts with the microtubular system and several aspects of this interpretation are discussed.     

Requirement of RBP9, a Drosophila Hu homolog, for regulation of cystocyte differentiation and oocyte determination during oogenesis

The Drosophila RNA binding protein RBP9 and its Drosophila and human homologs, ELAV and the Hu family of proteins, respectively, are highly expressed in the nuclei of neuronal cells. However, biochemical studies suggest that the Hu proteins function in the regulation of mRNA stability, which occurs in the cytoplasm. In this paper, we show that RBP9 is expressed not only in the nuclei of neuronal cells but also in the cytoplasm of cystocytes during oogenesis. Despite the predominant expression of RBP9 in nerve cells, mutational analysis revealed a female sterility phenotype rather than neuronal defects for Rbp9 mutants. The female sterility phenotype of the Rbp9 mutants resulted from defects in oogenesis; the lack of Rbp9 activity caused the germarium region of the mutants to be filled with undifferentiated cystocytes. RBP9 appears to stimulate cystocyte differentiation by regulating the expression of bag-of-marbles (bam) mRNA, which encodes a developmental regulator of germ cells. RBP9 protein bound specifically to bam mRNA in vitro, which is required for cystocyte proliferation, and the number of cells that expressed BAM protein was increased 5- to 10-fold in the germarium regions of Rbp9 mutants. These results suggest that RBP9 protein binds to bam mRNA to down regulate BAM protein expression, which is essential for the initiation of cystocyte differentiation into functional egg chambers. In hypomorphic Rbp9 mutants, cystocytes differentiated into egg chambers; however, oocyte determination and positioning were perturbed. Therefore, the concentrated localization of RBP9 protein in the oocyte of the early egg chambers may be required for proper oocyte determination or positioning.     

Further studies on the ring canal system of the ovarian cystocytes of Drosophila melanogaster

Summary An ultrastructural study was made of the ring canal system which connects the sister ovarian cystocytes that arise in the germaria of wild type Drosophila melanogaster females. It was discovered that during an oogonial mitosis both chromosomes and spindle are enclosed by a multilayered, perforated membrane system derived (at least in part) from the nuclear envelope. The cytokinesis of stem line oogonia takes place through the formation of a cleavage furrow. A second method of formation of plasma membrane is found in the case of cystocytes. It involves the production along the plane of division of a plaque of interconnected vesicles and tubules and later the coalescence of nearby tubules to form continuous sheets of membrane which segregate the cytoplasms of the sister cells. However, these remain connected by a canal which is enclosed by a ring-shaped rim that is completed prior to the plasma membrane to which the rim is subsequently attached. It is postulated that the rim represents a transformed midbody. As development proceeds the canal becomes wider, its rim becomes thicker, and the inner circumference of the rim becomes coated with a thick deposit having different cytochemical properties than the rim itself. Cystocyte divisions produce sister cells which differ in that one receives all previously formed canals; the other none. In the case of the last division (and perhaps in earlier ones as well) the sister cell receiving all previously formed canals also receives more cytoplasm than its sister. As the cells of the cluster grow, the canals remain close together. This finding suggests that when new plasma membrane is synthesized, it is added in areas remote from the canals. An investigation of the positioning in three dimensions of the fifteen canals of a newly formed, 16 cellcluster suggests that the spindles produced at one division are never parallel to those formed at the subsequent division. This continual shifting of the axes of the spindles at consecutive divisions presumably results in the branching chains of cells which characterize a cystocyte cluster. The possession of a unique pattern of cortical structures by two cystocytes is accompanied by the nuclear synthesis of synaptonemal complexes. The other fourteen cystocytes differentiate into nurse cells. In the most posterior portion of the germarium one of the two potential oocytes switches to the nurse cell developmental pathway. This switched off oocyte and the definitive oocyte grow at rates which differ greatly and are correlated to the amount of contact between their surfaces and certain follicle cells. As development proceeds centrioles accumulate in the oocyte, and most of these are thought to have been carried from the nurse cells into the oocyte in the nutrient stream.The authors are grateful to Richard Z. Belch and James E. Bradof for their conscientious assistance and to E. John Pfiffner for preparation of the inked drawings and construction of the Polyform models. This research was supported by the National Science Foundation grant GB7457.     

The role of polyfusomes in generating branched chains of cystocytes during Drosophila oogenesis

Three-dimensional models were constructed utilizing the information gained from electron micrographs of serial sections of two clones of cystocytes undergoing their terminal divisions. In each clone a polyfusome connected all eight cystocytes together. Each of the spindles was oriented so that one pole touched the polyfusomes, while the other pointed away from it. This positioning of spindles ensures that one cell of each dividing pair retains all previously formed canals, while the other receives none. The two cells that eventually come to contain the maximum number of canals and fusomal material are the ones that differentiate as pro-oocytes, while the others become nurse cells. The orientation of each spindle suggests that the polyfusome formed at one division determines the placement of the cytoskeletal fibers that anchor the spindles formed at the next division. There is a centripetal gathering together of new canals following each cycle of cystocyte division, which is thought to result from the subsequent contraction of the polyfusomal system. Females homozygous for the otu1 mutation are characterized by ovarian tumors, which result when germarial cystocytes undergo supernumerary divisions and fail to differentiate into either nurse cells or oocytes. An analysis of electron micrographs taken of serially sectioned, mutant germaria showed that most germ cells were single or belonged to clusters of two or three interconnected cells. Therefore otu1 cystocytes are unable to undergo a sustained series of arrested cleavages. These cystocytes contain fusomal material that shows ultrastructural differences from normal polyfusomes. We conclude: 1) that a normal polyfusomal system is a necessary prerequisite for the production of a branched chain of cystocytes and for their subsequent differentiation into pro-oocytes and nurse cells; and 2) that a product encoded by the otu+ gene is essential for the construction of a functional polyfusome.     

Cellular and molecular markers of anteroposterior and dorsoventral organisation in the vitellogenic follicles of adult Sarcophaga bullata (Diptera) and dorsoventral orientation of follicles in the ovary

Summary Polar organisation in the follicles of adult Sarcophaga bullata is reflected in the nurse cell-oocyte axis and in the orientation of the two polar cell pairs in the follicular epithelium. The internal organisation of the nurse cell chamber contributes to polarity but not to dorsoventral asymmetry. Dorsoventral asymmetry is correlated with the eccentric position of the germinal vesicle and the orientation of the polar cell pairs; no other follicle cell specialisations are seen. In an ovary, follicles are preferentially orientated with the dorsal side to the centre of the ovary. Cytoskeletal and some haemolymph proteins are molecular markers of polarity. Thus, in pre-vitellogenic stages, tubulin immunoreactivity is higher in the oocyte than in the nurse cells, actin immunoreactivity is the same over the cystocytes and larval serum proteins are restricted to the poles. During vitellogenesis, both actin and tubulin become more concentrated in the nurse cells and larval serum protein 1 accumulated in the polar cells during border cell migration when yolk polypeptides also accumulate in the oocyte. At the end of vitellogenesis a lipophorin is taken up by the oocyte. No molecular marker of dorsoventral asymmetry was identified.     

Mutant yolk proteins lead to female sterility in Drosophila.

Specific mutations in the yolk protein genes, yp1 and yp2, of Drosophila melanogaster cause the yolk proteins (YPs) they encode to precipitate, ultimately resulting in female sterility. YPs of the yp1 mutant fs(1)1163 are secreted normally but then precipitate as globules and occasionally as crystalline fibers in the subbasement membrane space of the fat body (Butterworth et al., 1991, J. Cell Biol. 112, 727-737). The present ultrastructural and immunological studies of the fat body of the yp2 mutant fs(1)K313 show that YP also precipitates as globules in the same tissue compartment. The globules are also incapable of passing into the hemolymph but they are morphologically distinct from those of fs(1)1163. Similar analyses were performed on developing oocytes in wild type and both mutant strains. YP-containing aggregates, ultrastructurally similar to those in the fat body of each respective mutant, were found in the space between the plasmalemma and the vitelline membrane and embedded within the membrane itself. The evidence suggests that the precipitates interfere with the correct assembly of the eggshell membranes, leading to the sterile phenotype. Immunogold studies demonstrate that newly synthesized YPs in the normal and mutant strains share secretory vesicles with putative, vitelline membrane proteins and that the translocation of follicle cell YP is not through the membrane along the interfollicular spaces but directly through the plasmalemma facing the oocyte. Further the YP precipitates in the mutants permit visualization of the polarity of exocytosis of YP from the follicle cells.     

Hair growth in mouse mutants affecting coat texture

The genetic control of hair growth has been studied in mice carrying the following coat texture genes: fz (fuzzy), soc (soft coat), hid (hair interior defect), sa (satin), It (lustrous), Ve (velvet), wa-1 (waved-1), Re (rex), Re ^wc (wavy coat) and pk (plucked).
A general effect on cells of epidermal origin, found in soc/soc and Ve /+ skin samples illustrates how common factors control developmental potential in both the stratum germinativum and the follicle bulb. A direct influence on follicle bulb development is also seen in fz/fz homozygotes in which the dermal papilla functions abnormally. The role of the bulb cells and the dermal papilla in the control of hair shaft calibre is discussed.
hid is a new gene, found in homozygous condition in all mice of the AKR inbred strain. hid and sa appear primarily to be concerned in the differentiation of the medulla.
In the hair waving mutants, waved-1, rex and wavy coat, the processes controlling hair movement within the follicle are disturbed. These genes appear to regulate internal root sheath function. When the normal relationship between internal root sheath and developing hair shaft is disturbed, shaft movement slows, with the subsequent development of shaft calibre abnormalities.
pk acts at the level of the sebaceous gland, disturbing the normal process of hair eruption. The roles of the internal root sheath, external root sheath and the sebaceous gland in hair eruption are discussed.
The abnormal epidermal layer in soc/soc and Ve /+ skin also disturbs hair eruption to a small extent. The resulting abnormalities this causes in hair shaft formation are compared with those found pk/pk samples and also with the similar effects of faulty hair movement in the hair waving mutants. An effect on pigmentation is also described.
The chemistry of keratinization appears to be normal in all these mutants.     

Oogenesis in Xenopus laevis (Daudin). V. Relationships between developing oocytes and their investing follicular tissues

The relationship of the cells and tissues which comprise the developing ovarian follicle in Xenopus laevis has been studied with scanning and transmission electron microscopy. The saclike ovary is covered on its coelomic side by a squamous epithelium. The cells of this epithelium are extensively interdigitated, and each bears a short, centrally positioned cilium. The lumenal surface of the ovary is covered with a layer of nonciliated squamous cells. The areas of cell-cell contact are characterized by desmosomes in both epithelia, and between the epithelia lies a connective tissue layer-the theca-which contains collagen fibers, blood vessels, nerves, smooth muscle cells and oogonia. Beneath the theca in each follicle lies a single layer of flat stellate follicle cells. Associations between adjacent follicle cells are intermittent, leaving wide spaces or channels. Junctional contacts between neighboring follicle cells are characterized by desmosomes. From the basal surface of each follicle cell extend long, broad macrovilli which penetrate the underlying acellular vitelline envelope and contact the surface of the oocyte. Evidence is presented which suggests that follicle cells may produce and release components which participate in the formation of the vitelline envelope which consists of a 3-dimensional lattice of ropey fibers. Passageways through the vitelline envelope allow the maintenance of contact between oocyte and follicle cells and also allow ready penetration of materials both to the oocyte (e.g., vitellogenin) and from it (e.g., cortical granule material) at different stages of its development.     

Testis differentiation in the glowworm, Lampyris noctiluca, with special reference to the apical tissue.

The gonads of Lampyris noctiluca are sexually undifferentiated during the first larval instars. They consist of many gonadal follicles that include the germ stem cells enclosed by the somatic cells of the follicle wall. Follicle wall cells are more numerous at the follicle apices than at the distal parts, but different cell types cannot be distinguished. In male larvae, the appearance of apical follicle tissue, derived from follicle wall cells, marks the onset of testis differentiation. When maximally expressed, the apical tissue occupies about the upper half of the testis follicles and can be observed in larvae of the fifth and sixth instar. The apical tissue is characterized by its "light" appearance (due to poor stainability) caused by the small number cellular organelles, especially a paucity of free ribosomes. Maximal expression of the apical tissue must be very brief, since in most examined fifth and sixth instar larvae the apical tissue is partly or mostly translocated into the center of the upper half of the follicles and spermatogonia then occupy the apical follicle tips. During and after translocation apical cells form projections that grow around clusters of spermatogonia (spermatocysts). Thus, the apical cells transform into spermatocyst envelope cells. They retain their "light" appearance but undergo dramatic subcellular differentiation: smooth ER becomes extremely prominent, forming stacks and whorls of parallel cisternae. Golgi complexes are also conspicuous. The cellular organization suggests secretory activity. The possibility of ecdysteroid production and its function is discussed. The spermatocyst envelope cells persist into the pupal stage. When spermiohistogenesis takes place in cysts, cyst envelope cells show signs of regression. At all stages of testis development apical cells and their derivatives, the spermatocyst envelope cells, phagocytize degenerating spermatogonia. Although this is an important task of these cells, the impressive formation of sER in the cyst envelope cells is indicative of an additional, as yet unknown, function.     

The salvador-warts-hippo pathway is required for epithelial proliferation and axis specification in Drosophila

In Drosophila, the body axes are specified during oogenesis through interactions between the germline and the overlying somatic follicle cells [1-5]. A Gurken/TGF-alpha signal from the oocyte to the adjacent follicle cells assigns them a posterior identity [6, 7]. These posterior cells then signal back to the oocyte, thereby inducing the repolarization of the microtubule cytoskeleton, the migration of the oocyte nucleus, and the localization of the axis specifying mRNAs [8-10]. However, little is known about the signaling pathways within or from the follicle cells responsible for these patterning events. We show that the Salvador Warts Hippo (SWH) tumor-suppressor pathway is required in the follicle cells in order to induce their Gurken- and Notch-dependent differentiation and to limit their proliferation. The SWH pathway is also required in the follicle cells to induce axis specification in the oocyte, by inducing the migration of the oocyte nucleus, the reorganization of the cytoskeleton, and the localization of the mRNAs that specify the anterior-posterior and dorsal-ventral axes of the embryo. This work highlights a novel connection between cell proliferation, cell growth, and axis specification in egg chambers.     

A Mutation in the Drosophila Profilin Homolog Gene Affects Gametogenesis and Bristle Development in Both Sexes

We have isolated a Drosophila melanogaster mutant, allelic to the profilin gene reported as chickadee . We named the allele chickadee^bin , in which the oogenesis and the spermatogenesis are disrupted, and the bristles are malformed. In the mutant nurse cells, cytoplasmic actin filaments fail to polymerize, and nuclei are displaced. The flow of cytoplasm from nurse cells to the oocyte is abortive. These ovarian phenotypes are principally the same as those reported in chickadee^{wc57 and WF57} (2). In addition, the egg chamber of chickadee^bin contains a reduced number of cystocytes that are binucleafed. In some egg chambers, the oocyte fails to differentiate. All cystocytes in such an egg chamber are morphologically similar to nurse cells with polyploid nuclei. Mutant male flies have defective testes in which the spermatocyst is deficient or reduced in number. Mutant adults have shortened and forked bristles. We discuss the function of profilin in the gametogenesis and bristle development.