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PubMed1995

Redistribution of nuclear envelope associated antigen during the mitotic cycle.

Murine hybridomas were generated to DNA/tight binding proteins complex isolated from the residual nuclear structure following a procedure analogous to that yielding "empty" shells of nuclear envelope. A monoclonal antibody designated 2A8 was selected because of its differential immunostaining of mitotic cells of a synchronized mouse fibroblast cell culture L-929. The target antigen was rendered insoluble by a sequence of extractions of isolated nuclei of diverse cell types with detergents, urea, DNase I and alkali thus reproducing some solubility properties of proteins constituting an operationally defined residual nuclear matrix. The cognate polypeptide was localized on a subset of proteins of M(r) 58-65 kDa, 70 kDa in isolated fibroblast nuclear matrices. The functional implication of the antigen in mitosis-related disassembly-assembly process of the nuclear matrix/envelope was detected. At prophase the antibody decorated the nuclear periphery and nuclear envelope fixed inward filaments. A fibrous network of cytoplasmic localization was stained in metaphase. At anaphase the antigen was dispositioned into peripheral fibrogranular clusters of polar orientation predominantly on one side of the nucleus. Proceeding to telophase a spreading fluorescence was manifested over the entire contour of the nuclear periphery to delineate the reforming nucleus. By immunogold electron microscopy of interphase cells the antigen was identified as evenly distributed in chromatin and interchromatin regions. At initiation of chromosome condensation in mitosis the label was detected predominantly in the chromosomal area.

Animals↗
PubMed1999

Mutations in the ATP-binding domain affect the subcellular distribution of mitotic centromere-associated kinesin (MCAK).

Mitotic centromere-associated kinesin (MCAK) is important for anaphase chromosome segregation. MCAK is diffusely localized to both the cytoplasm and the nucleus during interphase. At prophase MCAK is recruited to mitotic centromeres. It is associated with centromeres throughout mitosis and then returns to exhibiting a diffuse nuclear and cytoplasmic localization during interphase. MCAK has several predicted nuclear localization sequences. The subcellular distribution of expressed deletion constructs of GFP-MCAK suggest that the nucleocytoplasmic ratio of MCAK protein is dependent on a balance between several predicted nuclear localization sequences (NLS) and a putative nuclear exclusion sequence (NES) in the amino-terminal region of MCAK. Amino acid substitutions in the ATP-binding domain of the MCAK motor affect nuclear localization, which, in turn, influences the degree of centromere binding.

Adenosine Triphosphate↗
PubMed2001

The effect of cytochalasin J on kinetochore structure in PtK1 cells is mitotic cycle dependent.

Mitotic PtK1 cells were arrested in mitosis with nocodazole to determine the effect of cytochalasin J (CJ) on kinetochore structure in arrested and nocodazole-released cells. In previous studies it was shown that CJ had a more pronounced effect on alteration of kinetochore structure and spindle microtubule (MT) architecture when applied during prophase or prometaphase. In this study, mitotic cells were treated at preanaphase for 10 min with 1 microg/ml nocodazole, or in 1 microg/ml nocodazole and 10 microg/ml CJ to allow for the advancement of the 'mitotic clock'. Thus it can be determined if either changes in the timing of mitosis, the maturation of the kinetochore, and/or the lack of MT connection to the kinetochore affects the ability of CJ to detach or alter the attachment of chromosomes to the developing spindle. Preanaphase cells treated with 1 microg/ml nocodazole for 10 min and released into 10 microg/ml CJ showed significant changes in MT organization and kinetochore structure. MTs nucleated at the centrosome are fragmented and kinetochore structure was significantly altered showing only two laminae with few MTs inserted into this structure. Preanaphase cells treated with 1 microg/ml nocodazole and 10 microg/ml CJ for 10 min and released into 10 microg/ml CJ showed similar, but more pronounced, effects on kinetochore structure and spindle MT organization. We interpret these results to suggest that CJ treatment has a greater effect on MT attachment and kinetochore structure in nocodazole pre-treated cells, where the kinetochore structure is mature and the mitotic cycle has been advanced.

Animals↗
PubMed2002

Unusual cytological patterns of microsporogenesis in Brachiaria decumbens: abnormalities in spindle and defective cytokinesis causing precocious cellularization.

Cytogenetic studies carried out in the tetraploid accession BRA001068 of Brachiaria decumbens, also known as cv. Basilisk, revealed an unusual pattern of microsporogenesis. The spindle in metaphase I and anaphase I became heavily stained with propionic carmine. In telophase I, the interzonal microtubules continued to be intensely stained, and during the phragmoplast formation the fibers were pushed to the cell wall, persisting until prophase II, even after cytokinesis. Due to its tetraploid condition, the accession presented many cells with precocious chromosome migration to the poles in metaphase I and laggards in anaphase I that gave rise to micronuclei in telophase I. While in other polyploid accessions of Brachiaria micronuclei remained in this condition until the second cytokinesis, the micronuclei in this accession organized their own spindle in the second division. In several microsporocytes, the micronuclei with their minispindle were divided further into microcytes by additional cytokinesis. Some curious planes of cytokinesis were found in some cells, with partitioning of cytoplasm into cells of irregular shape. The result consisted of a high frequency of abnormal products of meiosis. Quadrivalents were observed in diakinesis at low frequency, which suggests a segmental allotetraploid and the inability of both genomes to co-ordinate their activities, leading to multiple spindle and precocious cellularization. In spite of abnormal meiotic products reducing pollen fertility, seed production was normal. Enough normal pollen was available to fertilize the central-cell nucleus of the embryo sac and produce normal endosperm in this pseudogamous aposporous apomictic accession.

Brachiaria↗
PubMed1993

Centrosome inheritance in starfish zygotes. II: Selective suppression of the maternal centrosome during meiosis.

Although both gametes may contribute a centrosome to the zygote at fertilization, only one of these centrosomes is used in development. Thus, specific mechanisms must exist to control centrosome inheritance in all sexually reproducing organisms. We use starfish as a model system to characterize these control mechanisms because the eggs complete meiosis I and meiosis II after fertilization; this allows us to directly follow the fate of all parental centrosomes in vivo. Only the paternal centrosome is used in starfish development. Although the microtubule organizing center activity of the maternal centrosome persists, the functional loss of this centrosome involves the suppression of its ability to double, or reproduce, at successive mitoses (Sluder et al., 1989. Dev. Biol. 131, 567-579). To determine when the reproductive capacity of the maternal centrosome is degraded, we transfer meiosis I and meiosis II spindles from just fertilized eggs into other zygotes that are in prophase of first mitosis. Meiosis I spindles are stable during first mitosis and are disassembled in first telophase in concert with the host spindle. In 61% of the cases a variable number of formerly meiotic centrosomes are active at second mitosis and reproduce in a normal fashion between subsequent mitoses. However, when meiosis II spindles are transferred in the same manner, in only 26% of the cases do any of the centrosomes persist past first mitosis or reproduce in a normal fashion thereafter. In the remainder of the cases the remnants of the maternal centrosomes organize a single monaster that does not double between mitoses. Control transfers of first mitosis spindles indicate that these results are not due to nonspecific damage to the meiotic spindles or to the recipient zygotes. These observations indicate that the reproductive capacity of maternal centrosomes is degraded during meiosis I, not during oogenesis. Our results also show that the cytoplasmic conditions which eliminate this reproductive capacity are no longer active once the zygote has entered the first mitotic cell cycle.

Animals↗
PubMed1993

A novel murine zinc finger gene mapped within the tw18 deletion region expresses in germ cells and embryonic nervous system.

A novel zinc finger gene, designated NT fin12, belonging to the C2H2-Krüppel-type gene family was isolated from a newborn mouse testis cDNA library by using zinc finger consensus motif probes. Northern blot analyses showed that NT fin12 mRNA was expressed during the meiotic prophase of spermatogenesis and in embryogenesis. Transcripts were localized by in situ hybridization in spermatogonia and in early spermatocytes, and in testis cords in the genital ridge as well as in oocytes and follicle cells in the ovary. In midgestational embryos at 8.5-13.5 days postcoitum, transcripts were present in the neuroectoderm, and they were progressively restricted to peripheral ganglia derived from neural crest cells and neural placodes and to the motor nerve cells in the central nervous system. Taken together these results indicate that NT fin12 functions during germ cell development and also plays a role in the specification of a subpopulation of neuroectodermal cells. Genetic linkage analyses revealed that the NT fin12 locus mapped to the deletion region of the tw18 haplotype on mouse chromosome 17.

Amino Acid Sequence↗
PubMed1993

Okadaic acid accelerates germinal vesicle breakdown and overcomes cycloheximide- and 6-dimethylaminopurine block in cattle and pig oocytes.

Pig and cattle oocytes, when released from the follicle, spontaneously resume first meiotic division within 20 or 8 hr, respectively. In oocytes of both species, the activity of histone H1 kinase increases during maturation, exhibiting a maximum in metaphase I. Treatment of these oocytes with okadaic acid results in acceleration of germinal vesicle breakdown (GVBD) and of histone H1 kinase activation. This effect is more important in pig oocytes, in which the acceleration rises for 6 hr, as compared to 2 hr in cattle. Moreover, under these conditions, H1 kinase activity measured after 12 hr of culture appears higher than that observed in control metaphase I oocytes. When added to prophase oocytes, both cycloheximide and 6-DMAP (6-dimethylaminopurine) block GVBD and histone H1 kinase activation. Okadaic acid, at a concentration of 2.5 microM, is able to release the inhibitory effect exerted by cycloheximide on histone H1 kinase activity; however, GVBD occurred only in two-thirds of pig and one-quarter of cattle oocytes after 20 hr of culture. In addition, okadaic acid fully reverses the effect of 6-DMAP on H1 kinase activity and on GVBD in both species. The opposite effects of 6-DMAP and okadaic acid on MPF activation are discussed, as well as the nature of the protein, which has to be synthesized during the first meiotic division and may be involved in the MPF activation cascade.

Adenine↗
PubMed1993

MAP kinase becomes stably activated at metaphase and is associated with microtubule-organizing centers during meiotic maturation of mouse oocytes.

Using antisera generated against sequences conserved between the ERK1- and the ERK2-encoded species of mitogen-activated protein (MAP) kinases of the rat, species of approximate M(r) 42 and 44 kDa were identified in mouse oocytes. When oocytes underwent meiotic maturation, both species displayed a retarded electrophoretic mobility, consistent with modification by phosphorylation. The slow-migrating forms first appeared after the oocytes had entered metaphase, and their appearance was sensitive to inhibitors of protein synthesis or phosphorylation. These forms remained throughout maturation and in oocytes arrested at metaphase II. Following oocyte activation, which induces a transition to interphase, the slow-migrating forms were replaced by the fast-migrating forms observed in prophase oocytes. MAP kinase activity also increased after oocytes entered metaphase, and this increase required protein synthesis and phosphorylation. To investigate the intracellular distribution of the immunoreactive species, spindles were purified from metaphase II eggs. Both the 42- and the 44-kDa species were detected in immunoblots, and bright staining of the spindle poles was observed by immunofluorescence. When intact oocytes undergoing maturation were examined by immunofluorescence, foci of staining were initially detected on opposing sides of the condensing chromosomes and then became congregated at each pole of the first meiotic spindle. No localized staining was observed during the first meiotic division, but stained foci were present at the poles of the second meiotic spindle. In addition, several cytoplasmic foci of staining often could be seen. When oocytes were exposed to taxol, which permits nonspindle microtubule-organizing centers (MTOCs) present in the cytoplasm to nucleate microtubule assembly, the cytoplasmic foci labeled by the MAP kinase antibodies were found to contain tubulin. We conclude that mouse oocytes contain 42- and 44-kDa species of MAP kinase and that, after maturing oocytes enter metaphase, MAP kinase activity is stimulated by means of a process requiring protein synthesis and phosphorylation. MAP kinase is present in the spindle and is specifically associated with the MTOCs present at the spindle poles and in the cytoplasm. Evidence from cell-free systems suggests that the alterations in MTOC activity that normally occur at metaphase in oocytes may be regulated by MAP kinase. The association of MAP kinase with MTOCs provides a potential structural basis for this cell cycle-dependent change in MTOC activity.

Animals↗
PubMed1993

The egg nucleus regulates the behavior of sperm nuclei as well as cycling of MPF in physiologically polyspermic newt eggs.

The possible role of the egg nucleus in regulating the behavior of sperm nuclei and the cycling of maturation-promoting factor (MPF) was investigated in the physiologically polyspermic eggs of the newt Cynops pyrrhogaster. Many sperm entered all areas of the egg, but only one sperm pronucleus, the principal sperm pronucleus, moved to the center of the animal hemisphere to form a zygote nucleus with the egg pronucleus. All sperm and egg pronuclei synthesized DNA, but the zygote nucleus completed the synthesis of DNA 0.5-1 hr earlier than the accessory sperm nuclei. Entrance into M phase by the accessory sperm nuclei was delayed to a greater and greater extent with increasing distance of these nuclei from the zygote nucleus. When DNA in the egg nucleus was damaged by uv irradiation, not only were both prophase and M phase in the zygote nucleus prolonged, but also the MPF cycle was delayed. Some accessory sperm nuclei in the animal hemisphere escaped degeneration to form additional bipolar spindles, so that delayed multipolar cleavage occurred. The MPF activity in the vegetal hemisphere was less than 25% of that found in the animal hemisphere at M phase in normally fertilized eggs. The levels of immunologically detectable proteins that contained the sequence PSTAIR in vegetal hemispheres were less than 25% of those in animal hemispheres. These results indicate that the egg nucleus of the Cynops egg is involved in the control of the activation of MPF and that the accessory sperm nuclei in the vegetal hemisphere degenerate as a result of the lack of components that are indispensable for entry into M phase.

Animals↗
PubMed1994

Characterization of a major nucleoplasmin-like germinal vesicle protein which is rapidly phosphorylated before germinal vesicle breakdown in Spisula solidissima.

Oocytes of the surf clam, Spisula solidissima, are arrested at the G2/M boundary of meiotic prophase I. At this stage, they possess a prominent germinal vesicle (GV), comprising about 25% of the total oocyte volume, in which pools of mRNAs and proteins that facilitate the rapid rounds of cell division which occur early in development are stored. We have isolated and characterized an abundant 49-kDa phosphoprotein, localized exclusively to the GV, which shares properties with nucleoplasmin. Like nucleoplasmin, this 49-kDa protein is a heat-stable, highly acidic phosphoprotein [containing over 32% (Glx + Asx) with an isoelectric point of about 4.0] and is soluble in 80% ammonium sulfate. In contrast to the pentameric nucleoplasmin, much of this protein is isolated as a disulfide-linked multimer which migrates at 120 kDa. In addition, a fraction of the 49-kDa protein is associated via disulfide bonds to a doublet of 42-kDa proteins. In vivo, this 49-kDa protein is phosphorylated prior to germinal vesicle breakdown (GVBD) and at 5 min after oocyte activation rapidly incorporates 32P to 60% of maximal level, suggesting that this protein plays a major role in the cascade of events which lead to oocyte activation and GVBD.

Animals↗
PubMed1994

Microtubule organization in the cow during fertilization, polyspermy, parthenogenesis, and nuclear transfer: the role of the sperm aster.

Microtubule organization in bovine oocytes during fertilization, polyspermy, parthenogenesis, and nuclear transfer is examined with the goal of understanding microtubule activity and the manner in which the centrosome during fertilization and mitotic spindle poles are established. In the unfertilized bovine oocyte, microtubules are detected only in the metaphase-arrested second meiotic spindle; no cytoplasmic asters are observed. After insemination, a small aster of microtubules is seen adjacent to the incorporated sperm head. This aster enlarges and, at the time of pronuclear apposition, fills the cytoplasm. At prophase, the aster splits and forms the poles for the first mitotic spindle, which is anastral, fusiform, and often located eccentrically. During anaphase, asters assemble at each spindle pole. After telophase, these asters develop into the interphase array of microtubules in the daughter blastomeres. During polyspermy, an aster forms from a site between each incorporated sperm head and tail. Multiple mitotic spindles are observed in polyspermic zygotes; multipolar spindles are not seen. Parthenogenetic activation with 5 microns ionomycin followed by a 4-hr incubation in 1.9 mM dimethylaminopurine results in > 80% activation, and antitubulin immunofluorescence microscopy demonstrates that initially disarrayed microtubules are observed and the some microtubules extend from the remnants of the second meiotic spindle. At the time normal for cell division, these parthenogenotes form anastral, barrel-shaped bipolar mitotic spindles. Asters form at the spindle poles at anaphase and the parthenogenotes divide from one to two blastomeres. Nuclear fusion of a morula-derived blastomere to a parthenogenetically activated oocyte results in either a single microtubule aster or at times, two asters, formed in association with the donated nucleus. These results demonstrate that fertilization in the cow is a blending of paternally and maternally derived centrosomal material.

Animals↗
PubMed1994

Repetitive intracellular Ca2+ increases at fertilization and the role of Ca2+ in meiosis reinitiation from the first metaphase in oocytes of marine bivalves.

Spawned oocytes of marine bivalves Limaria hakodatensis, Mytilus edulis, Crassostrea gigas, and Hiatella flaccida are arrested at the first metaphase (metaphase-I) until fertilization. We have measured changes in intracellular Ca2+ ([Ca2+]i) at fertilization in the single oocytes of these bivalves using the fluorescent Ca2+ indicator fura-2. Shortly after insemination, these oocytes displayed a transient [Ca2+]i increase which was usually followed by a period during which [Ca2+]i was kept higher than the resting level (elevated [Ca2+]i period). During this period, [Ca2+]i showed oscillatory increases superimposed on an elevated [Ca2+]i level in Limaria, Crassostrea, and Hiatella, whereas a sustained elevation without pulses occurred in Mytilus. After [Ca2+]i returned to the resting level, repetitive transient [Ca2+]i increases appeared in Limaria, Mytilus, and Hiatella. The [Ca2+]i increases still occurred following external Ca2+ removal shortly after fertilization in all four bivalve species. In contrast, external Ca2+ removal immediately abolished a [Ca2+]i increase induced by excess-K+ seawater in Mytilus. Using another fluorescent Ca2+ indicator, calcium green, we found that during the first transient in Mytilus, [Ca2+]i increased uniformly over the whole oocyte. These results strongly suggest that the fashion of [Ca2+]i increases at fertilization in bivalve oocytes fertilized at metaphase-I differs not only from that in deuterostomes but also from that in protostomes oocytes of which are fertilized at the first prophase.

Animals↗
PubMed1994

Effects of cytoplasmic components upon sperm aster development in Bufo arenarum eggs.

Bufo arenarum oocytes obtained during the winter period, presenting a metabolism similar to that of the differentiated tissues, are not able to form a sperm aster after spermatozoon injection. These oocytes may be considered immature, with respect to the state of their cytoplasm. In the present work, aster formation was induced in winter coelomic oocytes through injection of cytoplasm from summer oocytes, GTP, and EDTA. When winter oocytes received cytoplasm from summer oocytes, they became able to form asters. If the cytoplasm interchange was inverted, i.e., if the cytoplasm of winter oocytes was injected into summer oocytes, no modification of the capacity to form asters was detected. In addition, the injection of GTP into winter oocytes induced the formation of asters in up to 60% of the oocytes, while the chelation of Ca2+ with EDTA had no effect on aster formation. Winter coelomic oocytes behaved as oocytes during prophase even after germinal vesicle breakdown. From the above, it may be suggested that these oocytes cannot activate the microtubule organizing centers.

Animals↗
PubMed1995

Postmeiotic transcription of X and Y chromosomal genes during spermatogenesis in the mouse.

During the meiotic prophase of spermatogenesis, the X and Y chromosomes form the heterochromatic sex body, showing little transcriptional activity. It has been suggested that transcription of the Xist gene is involved in this inactivation. After completion of the meiotic divisions, at least two Y chromosomal genes, Zfy and Sry, are transcribed in haploid spermatids. In contrast, postmeiotic transcription of X chromosomal genes has not been demonstrated. Using highly purified preparations of mouse pachytene spermatocytes, round spermatids, and cytoplasmic fragments from elongated spermatids, the present experiments show differential postmeiotic expression of the Y chromosomal genes Ubely and Sry, with highest mRNA levels in round spermatids and cytoplasmic fragments, respectively. Postmeiotic transcription of the X chromosomal gene Ube1x is indicated by an increased level of Ube1x mRNA in round spermatids and cytoplasmic fragments. The X chromosomal gene MHR6A shows a marked temporary postmeiotic expression in round spermatids. This postmeiotic activity of the X chromosome is a novel finding, which may have implications for our understanding of X chromosome inactivation during spermatogenesis and paternal genome imprinting.

Animals↗
PubMed1995

Immunolocalization of the heterotrimeric kinesin-related protein KRP(85/95) in the mitotic apparatus of sea urchin embryos.

We have used monoclonal antibodies to perform confocal light microscopic immunolocalization of KRP(85/95), a heterotrimeric plus-end-directed microtubule motor protein, in dividing cells of sea urchin embryos. Embryos were stained during the first division cycle, and dissociated blastomeres were stained at the 32- to 64-cell stages. Double labeling of the dividing cells with anti-tubulin and anti-KRP(85/95) showed a clear concentration of the motor protein in the mitotic apparatus; KRP(85/95) appeared to associate with pericentriolar regions during prophase, with kinetochore-to-pole microtubules during metaphase, and, in a striking fashion, with the spindle interzone during anaphase. KRP(85/95) began to accumulate in the interzone immediately following chromosome separation and the area of concentration expanded with the lengthening of the interzonal region during anaphase. During telophase KRP(85/95) appeared to disperse with the establishment of the cleavage furrow and did not concentrate in the midbody. KRP(85/95) staining in the mitotic apparatus was punctate and detergent-sensitive, suggesting an association with membranous vesicles, but unlike kinesin, KRP(85/95) did not appear to codistribute with calsequestrin-containing endoplasmic reticulum. Finally, KRP(85/95) appears to be present in dividing blastomeres up to at least the blastula stage, but, unlike kinesin, it is not expressed in terminally differentiated, nonmitotic coelomocytes of the adult animal. These results suggest that the expression and targeting of KRP(85/95) and kinesin differ and that KRP(85/95) may play a role in vesicle transport during embryonic cell division.

Animals↗
PubMed1996

Tosca: a Drosophila gene encoding a nuclease specifically expressed in the female germline.

We describe here a Drosophila gene, tosca (tos), that is specifically expressed in the female germline. tos mRNA accumulates selectively within the pro-oocyte in germarial region 2 and persists throughout oogenesis. In the early embryo, the maternally supplied tos mRNA is evenly distributed at the syncytial blastoderm stage, but is excluded from the forming cells when cellularization begins. tos product is the first Drosophila member of the RAD2 protein family, a group of related DNA repair nucleases conserved from yeast to humans. Within the family, Tos is more closely related to ExoI, a Schizosaccharomyces pombe 5'-->3' double-stranded DNA exonuclease specifically induced in meiotic prophase I. The definite oocyte localization of tos transcript during meiosis and its ubiquitous distribution in early embryos suggest that tos may play a role in mismatch repair during genetic recombination and early cleavage divisions.

Amino Acid Sequence↗
PubMed1996

Pem: a testosterone- and LH-regulated homeobox gene expressed in mouse Sertoli cells and epididymis.

Few transcription factors in somatic cells of the testis and epididymis that could potentially regulate androgen-dependent developmental events during male gametogenesis have been identified. In this study we examined the regulation and expression of an orphan homeobox gene, Pem, which encodes a homeodomain related to those in the Prd/Pax gene family. RNase protection, in situ hybridization, and Northern blot analyses of wild-type and germ-cell-deficient mutant mice (W(V)/ W(V)) localized Pem transcripts to Sertoli cells of the testis. During prepubertal testicular development, Pem expression was dramatically induced on Day 9, approximately when germ cells are known to enter meiotic prophase. In adult mice, Pem transcripts were preferentially expressed in stages VII-VIII seminiferous epithelium, the androgen-dependent stages during which germ cells undergo the first step of meiosis. Pem gene expression depended on androgens and gonadotrophins, as demonstrated by a lack of expression in hypophysectomized mice, gonadotrophin-deficient hypogonadal (hpg) mutant mice, and androgen receptor-deficient (tfm) mutant mice. Injection of either testosterone or luteinizing hormone (LH) into hypophysectomized and hpg/hpg mice restored Pem expression in the testes to normal levels. The Pem gene was also shown to be specifically expressed in the proximal cauda and distal corpus regions of the epididymis, the regions where spermatozoa gain forward motility and fertilization competence. Pem expression in the epididymis did not depend on spermatozoa in the lumen of the testis, as shown in quaking (qk/qk) mutant mice, however, unlike in the testes, epididymal Pem expression required germ-cell-induced factors. Our results show that discrete cell types in male reproductive tissues transcribe and independently regulate the Pem homeobox gene. To our knowledge no transcription factors have previously been shown to depend on testosterone or LH for expression in Sertoli cells in vivo. Collectively, the data implicate Pem as a candidate to regulate a subset of androgen-dependent genes in the male reproductive system.

Animals↗
PubMed1996

GLD-1, a cytoplasmic protein essential for oocyte differentiation, shows stage- and sex-specific expression during Caenorhabditis elegans germline development.

GLD-1, a putative RNA binding protein, is essential for oocyte development in Caenorhabditis elegans. A gld-1 null mutation abolishes hermaphrodite oogenesis and confers a tumorous germline phenotype in which presumptive female germ cells exit the meiotic pathway and return to the mitotic cell cycle. Here we demonstrate that gld-1(null) germ lines express female-specific, but not male-specific, molecular markers, indicating that gld-1 acts downstream of sexual fate specification to regulate oocyte differentiation. Immunolocalization studies identify GLD-1 as a cytoplasmic germline protein that displays differential accumulation during germline development. First, germ cells that are in the mitotic cell cycle contain low levels of GLD-1 that likely reflect a nonessential gld-1 function (negative regulation of proliferation in the mitotic germ line) revealed in previous genetic studies. Second, entry of presumptive oocytes into the meiotic pathway is accompanied by a strong increase in GLD-1 expression/accumulation. GLD-1 levels are high through the pachytene stage but fall to background as germ cells exit pachytene and complete oogenesis. The meiotic prophase accumulation pattern is consistent with GLD-1's essential role in oocyte differentiation, which may be to repress the translation of a subset of maternal RNAs synthesized during early oogenesis until late oogenesis when GLD-1 is absent.

Animals↗