ISSN:0192-253X    

DOI:10.1002/dvg.1020160103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractGermline cysts containing 16 interconnected cells (cystocytes) are produced at an early stage ofDrosophilaoogenesis by progenitor cells known as cystoblasts that undergo four synchronous rounds of incomplete division. During cyst formation, a region of specialized, spectrin‐rich cytoplasm called the fusome traverses the intercellular Connections (ring canals), linking individual cystocytes. Subsequently, 15 cystocytes begin to transport specific RNAs and other components into the remaining cell, the future oocyte. We used fusome‐specific antibodies to characterize the early stages of cyst formation. During the first cystoblast division, a spherical mass of fusome material (the “spectrosome”) was associated with only one pole of the mitotic spindle, revealing that this division is asymmetric. During the subsequent three divisions, the growing fusome always associated with the pole of each mitotic spindle that remained in the mother cell, and only extended through the newly formed ring canals after each division was completed. These observations suggest that fusomes help establish a system of directional transport between cystocytes that underlies oocyte determination. © 1995 Wiley

ISSN:0192-253X    

DOI:10.1002/dvg.1020160104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMeiotic maturation progresses atypically in oocytes of strain LT/Sv and l/LnJ mice. LT/Sv occytes show a high frequency of metaphase l‐arrest and parthenogenetic activation. l/LnJ oocytes display retarded kinetics of meiotic maturation and a high frequency of metaphase l‐arrest. Some l/LnJ oocytes fail to resume meiosis. Changes in the configuration of chromatin, microtubules, and centrosomes are associated with specific stages of meiotic progression. In this study, the configuration of these subcellular components was examined in LT/Sv, l/LnJ, and C57BL/6J (control) oocytes either freshly isolated from large antral follicles or after culture for 15 hr to allow progression of spontaneous meiotic maturation. Differences were found in the organization of chromatin, microtubules, and centrosomes in LT/Sv and l/LnJ oocytes compared to control oocytes. For example, rather than exhibiting multiple cytoplasmic and nuclear centrosomes as in the normal germinal vesicle‐stage oocytes, LT/Sv oocytes typically contain a single large centrosome. In contrast, l/LnJ oocytes displayed many small centrosomes. The microtubules of normal germinal vesicle‐stage oocytes were organized as arrays or asters, but microtubules were shorter in LT/Sv oocytes and absent from l/LnJ oocytes. After a 15‐hr culture, centrosomal material of normal metaphase II oocytes was organized at both spindle poles. In contrast, metaphase l‐arrested LT/Sv oocytes exhibited an elongated spindle with centrosomal material appearing more organized at one pole of the spindle. Both control and LT/Sv oocytes displayed cytoplasmic centrosomes. Metaphase l‐arrested l/LnJ oocytes rarely had cytoplasmic centrosomes but exhibited centrosomal foci at the spindle periphery. Thus, oocytes that are atypical in the progression of meiotic maturation displayed aberrant configurations of microtubules and centrosomes, which are thought to participate in the regulation of meiot

ISSN:0192-253X    

DOI:10.1002/dvg.1020160105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractN‐cadherin (N‐cad) is a calcium‐dependent cell adhesion molecule which is present in the granulosa cells of the mouse ovarian follicle. This cell adhesion molecule has been implicated as a key modulator of follicular development. The regulators of N‐cad mRNA levels in the ovary have not been identified. We have examined the ability of steroids to influence ovarian N‐cad mRNA levels in vivo. Immature mice were injected with either progesterone, testosterone, 17β‐estradiol, or 17α‐estradiol. Only 17β‐estradiol caused a rapid and significant increase in the ovarian N‐cad mRNA levels. We speculate that this steroid is a major regulator of N‐cad‐mediated granulosa cell interactions in vivo

ISSN:0192-253X    

DOI:10.1002/dvg.1020160106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractWe present evidence for the essential homology of four nuclear organelles that have previously been described under four different names: coiled bodies in mammalian somatic nuclei, prenucleolar bodies in nuclei assembled in vitro inXenopusegg extract, sphere organelles in amphibian germinal vesicles (GVs), and Binnenkörper in insect GVs. Each of these organelles contains coilin or a coilin‐related protein plus a variety of small nuclear ribonucleoproteins. We suggest that the sphere organelle/coiled body is a “universal” nuclear component in the sense that it is involved in common nuclear processes and hence will be found in one form or another in most eukaryotic cells. We postulate that it functions in the assembly and sorting of snRNP complexes for three RNA processing pathways: pre‐mRNA splicing, rRNA processing, and histone pre‐mRNA 3′ end formation. Specifically, the sphere organelle/coiled body may be the initial site for assembly of processing complexes, which are then sorted to other places in the nucleus, where the actual RNA processing takes place. © 1995 Wi

ISSN:0192-253X    

DOI:10.1002/dvg.1020160107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMaturation of an immature oocyte into one capable of being fertilized involves tightly choreographed movements of chromosomes and organelles. The localizaton of mitochondria during maturation was studied in live mouse oocytes by confocal laser scanning microscopy (CLSM). Mitochondria were labeled with rhodamine 123 or Mitotracker (Molecular Probes, Eugene, OR) both of which are cell permeant and accumulate in mitochondria; acridine orange was used to mark chromatin. Prior to maturation, oocytes appeared to be radially symmetrical with no evident polarity; fully mature oocytes exhibited obvious polarity marked by the position of the metaphase II spindle in the cortex. CLSM revealed several interesting features of mitochondrial distribution: (1) A cortical clump of mitochondria was seen approximately 30‐45to one side of the metaphase II spindle and marked the region of polar body I extrusion. (2) Large foci of mitochondria (7–14μM) were frequently found around the central region of the mature oocyte, while the central region often exhibited markedly fewer mitochondria. (3) Small mitochondrial foci (3μM) in the cortex and near the GV characterized several oocytes which failed to mature. (4) Non‐spindle‐associated mitochondria were not uniformly distributed in the mature oocyte but were concentrated in the hemisphere containing the metaphase II spindle. (5) The distal margins of this mitochondrial hemisphere were sharply demarcated at the cortex. These findings should help us understand organelle localization during mammalian oocyte maturation, and may give insights into possible causes of infertility and into early events of preimplantation development. © 1995 Wiley

ISSN:0192-253X    

DOI:10.1002/dvg.1020160108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPlants produce female gametes through mitotic division in the multicellular, meioticolly reduced (haploid) megagametophyte phase. In flowering plants, the megagametophyte is the embryo sac; female gametogenesis or megagametogenesis comprises the ontogeny of the embryo sac. As a step toward understanding the role of embryo sac‐expressed genes in megagametogenesis, development of normal, haploid embryo sacs in maize was compared with development of embryo sacs deficient for various small, cytologically defined chromosomal regions. This analysis allowed us to screen 18% of the maize genome, including most of chromosome arms 1L and 3L, for phenotypes due specifically to deletion of essential, embryo sac‐expressed genes. Confocal laser scanning microscopy of whole developing embryo sacs confirmed that normal megagameto‐genesis in maize is of the highly stereotyped, bipolarPolygonumtype common to most flowering plants examined to date. Deficiency embryo sac phenotypes were grouped into three classes, suggesting each deficient region contained one or more of at least three basic types of haploid‐expressed gene functions. In the first group, three chromosome regions contained genes required for progression beyond early, free‐nuclear stages of embryo sac development. Maintaining synchrony between events at the two poles of the embryo sac required genes located within two deficiencies. Finally, three chromosome regions harbored loci required for generation of normal cellular patterns typical of megagametogenesis. This analysis demonstrates that the embryo sac first requires postmeiotic gene expression at least as early as the first postmeiotic mitosis. Furthermore, our data show that a variety of distinct, genetically separable programs require embryo sac‐expressed gene products during megagametogenesis, and suggest the nature of some of those developmental mechanisms. © 1995 Wil

ISSN:0192-253X    

DOI:10.1002/dvg.1020160109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTheDrosophila melanogastertumor suppressor genelethal(2)tumorous imaginal discs (l(2)tid)causes in homozygotes malignant growth of cells of the imaginal discs and the death of the mutant larvae at the time of puparium formation. We describe the molecular cloning of the1(2)tid+gene and its temporal expression pattern in the wild‐type and mutant alleles. Germ line rescue of the tumor phenotype was achieved with a 7.0 kb Hindlll‐fragment derived from the polytene chromosome band 59F5. Thel(2)tid+gene spans approximately 2.5 kb of genomic DNA. The protein coding region, 1,696 bps long, is divided by an intron into two exons. The predictedTid56protein contains 518 amino acids and possesses a theoretical molecular weight of 56 kDa. It shows significant homology to all knownDnaJrelated proteins from bacteria, yeast, and man. The possible function of theTid56protein in tumor suppression is delineated. © 1995 Wiley‐Lis

ISSN:0192-253X    

DOI:10.1002/dvg.1020160110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe quontitation of RNA in tissue homogenates by amplifying the product of reverse transcription (RT‐PCR) is sufficiently sensitive to detect molecules in the range of 10−110−2amole. We describe here the steps we believe necessary to validate a protocal that used a DNA competitor and visualization of the amplification products by ethidium bromide staining. The procedure was designed to quantitate one of the tissue specific transcripts of the Dopa decarboxylase gene(Ddc)inDrosophila.We demonstrate that the amount of epidermalDdctranscript is much lower at pupariation in several mutants of theBroad‐Complex, one of the primary response loci of the moulting hormone, ecdysone. The mutant effects were allele specific and the molecular basis of one of these alleles is known. This implicates a particular family of the zinc finger proteins encoded by the locus in the hormone dependent induction ofDdcexp

ISSN:0192-253X    

DOI:10.1002/dvg.1020160111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractMutants of theDrosophila miniature‐dusky (m‐dy)gene complex display morphogenetic phenotypes (miniature or dusky) caused by a change in the size and/or shape of the epidermal cells comprising the adult wing. In addition to a dusky phenotype, certainAndante‐typemutants also exhibit lengthened circadian periods for two different behavioral rhythms. If the latter phenotype results from a direct effect on the circadian pacemaker, theAndantefunction should be required within the brain. In order to define the tissues that require the morphogenetic and behavioral functions, we have carried out a genetic mosaic analysis. This study demonstrates that normal wing morphogenesis is entirely dependent on the genotype of wing cells. Furthermore, temperature‐shift experiments with a temperature‐sensitivedymutant indicate that the morphogenetic function is required during adult development, and after the cessation of wing epidermal cell proliferation. At this time in development, a columnar epithelium in the developing wing becomes flattened into the mature wing blade, and we postulate that the cell‐size defect ofm‐dymutants results from an alteration of this mor‐phogenetic process. In contrast to the wing mor‐phogenesis phenotype, the characterization of locomotor activity in mosaic adults revealed a strong correlation between the head genotype and the Andante circadian‐period phenotype. This result indicates that neural tissues mediate the rhythm function. Thus, the behavioral and morphogenetic functions require gene expression in distinct tissues. Furthermore, the behavioral results are consistent with a requirement forAndantefunction within circadian pacemaker neurons. ©

ISSN:0192-253X    

DOI:10.1002/dvg.1020160112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY