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PubMed2002

Two messenger RNA isoforms of the gonadotrophin-releasing hormone receptor, generated by alternative splicing and/or promoter usage, are differentially expressed in rainbow trout gonads during gametogenesis.

The recent cloning of a gonadotrophin-releasing hormone receptor (GnRH-R) cDNA from rainbow trout showed that it contains several in-frame ATG codons, one of which, ATG2, corresponds to that found in other species. However, an upstream codon, ATG1, could give rise to a protein with a larger extracellular domain. Using S1 nuclease assay and a method combining primer extension and RACE-PCR, we characterized a second population of mRNA, termed mRNA-2, with a distinct 5'untranslated region and lacking ATG1. The genomic origin of the two mRNAs was determined by establishing the complete gene structure, which shows, for the first time in a vertebrate species that an alternative splicing and promoter usage generate two GnRH-R mRNA variants whose 5' extremities are encoded by two different exons. The analysis of the tissue distribution indicated that mRNA-2 presents a broader pattern of expression and is detected at higher levels than mRNA-1. Interestingly, it was found that those two mRNAs are differentially expressed in male and female gonads during gametogenesis. In particular, the variations of mRNA-1 levels parallel those of sGnRH expression during spermatogenesis, indicating that tissue-specific processing of the GnRH-R mRNA may underlie the effects of GnRH as a paracrine/autocrine regulator of gonadal functions.

5' Untranslated Regions↗
PubMed1996

SksC, a fertilization-related protein kinase in Chlamydomonas, is expressed throughout the cell cycle and gametogenesis, and a phosphorylated form is present in both flagella and cell bodies.

Fertilization in the biflagellated eukaryote, Chlamydomonas, is initiated by flagellar adhesion between gametes of opposite mating types. An early event in the signal transduction pathway induced by these cell-cell interactions is the rapid inactivation of a flagellar protein kinase that phosphorylates a 48 kDa flagellar protein. Molecular cloning and characterization indicated that the 48 kDa substrate, termed SksC, itself is a novel protein kinase. Here, we have determined that its transcript levels were unchanged during prolonged flagellar adhesion. Moreover, resynthesis of new flagellar proteins following deflagellation was not accompanied by increases in transcript levels of SksC, suggesting that expression of this soluble protein kinase might not be restricted to flagella. Immunoblot analysis indicated that expression of SksC was ubiquitous: this soluble protein was found in both flagella and cell bodies and was expressed throughout the cell cycle and gametogenesis. Immunoprecipitation experiments indicated that SksC was phosphorylated in both flagella and cell bodies. Thus, in addition to its potential role in fertilization, this novel protein kinase may play a role in other signaling events in Chlamydomonas.

Animals↗
PubMed1997

Differential expression of two gamma-tubulin isoforms during gametogenesis and development in Drosophila.

Previous work identified a gamma-tubulin gene, gamma Tub23C, in Drosophila (Zheng et al., 1991). We now report identification of a second gamma-tubulin gene, gamma Tub37CD. Immunoblot analysis and immunolocalization show that gamma Tub37CD and gamma Tub23C are differentially expressed during gametogenesis and development. During oogenesis, gamma Tub23C was detected at centrosomes and in the cytoplasm of mitotic germ cells, but was not detected in germ cells following completion of mitosis. Conversely, gamma Tub37CD was not detected in proliferating germ cells, but appeared to accumulate in germ cells during egg chamber development. Neither gamma-tubulin isoform was detected at the anterior or posterior poles of developing oocytes. During spermatogenesis, only gamma Tub23C was detected at centrosomes, where it showed cell cycle- and differentiation-dependent organization. During the transition into the first meiotic division, gamma Tub23C became organized as a corpuscular focus at centrioles until completion of meiosis II. During postmeiotic spermatid differentiation, gamma Tub23C was detected first as a rod and then as a collar-like structure near the juncture of the nucleus and the elongating flagellum, but was not detected in bundles of mature sperm. The germline-specific CDC25 encoded by twine is required for organization of gamma Tub23C into corpuscular focus in spermatocytes, but not for separation of centriole pairs in M-phase or postmeiotic organization of gamma Tub23C at centrioles. Following reconstitution of a canonical centrosome at fertilization, only gamma Tub37CD was detected at centrosomes in syncytial embryos, but both gamma Tub37CD and gamma Tub23C were detected at centrosomes in cellularized embryos. Colocalization of these two isoforms suggests that gamma Tub23C and gamma Tub37CD both contain structural features of gamma-tubulins essential for localization to centrosomes.

Amino Acid Sequence↗
PubMed2001

Effect of genistein-enriched diets on the endocrine process of gametogenesis and on reproduction efficiency of the rainbow trout Oncorhynchus mykiss.

Three practical diets were formulated to contain 0, 500, or 1000 ppm genistein. The three diets were distributed for 1 year to groups of rainbow trout undergoing their first gametogenesis and until spawning. Growth performance of rainbow trout was not affected by dietary treatments. Plasma cholesterol levels were equivalent between groups. In males, a slight but constant induction of vitellogenin (VTG) synthesis and a decrease in testosterone levels were observed. A slight decrease in plasma levels of betaFSH and betaLH was noticed at the end of spermatogenesis in the male fish fed a diet with 500 ppm (genistein) (from 2.16 +/- 0.39 to 1.47 +/- 0.23 for betaFSH and from 0.44 +/- 0.09 to 0.31 +/- 0.09 for betaLH). There was a significantly reduced 17alpha,20beta(OH)(2)-progesterone (from 10.93 +/- 0.88 in control to 5.46 +/- 0.92 in males and from 251.22 +/- 21.40 to 183.22 +/- 13.48 in females). Testicular development was accelerated in genistein-fed fish, and sperm motility and concentration were decreased in a dose-dependent manner at spawning. In females, a significant increase in plasma VTG occurred only at the beginning and at the end of oogenesis. Testosterone levels were decreased at the beginning of oogenesis. Both betaFSH and betaLH were decreased by genistein (from 6.38 +/- 1.55 to 3.44 +/- 0.82 for betaFSH and from 15.18 +/- 3.00 to 6.93 +/- 0.99 for betaLH in females), whereas spawning was delayed only in females fed the diet with 500 ppm of genistein. Gamete quality was impaired only in this group, as underlined by a lower percentage of ovulating females (from 100 to 79% at the end of the trial), a lower fertilization rate, and a lower viability of fry. These results may be explained by the agonistic/antagonistic effect of genistein on estrogen function related to the tissue ratio between endogenous estrogens/genistein.

Animals↗
PubMed2001

cDNA cloning of two gonadotropin beta subunits (GTH-Ibeta and -IIbeta) and their expression profiles during gametogenesis in the Japanese flounder (Paralichthys olivaceus).

To clarify the profiles of two distinct gonadotropin (GTH-I and -II) mRNA levels during gametogenesis in a multiple spawner, the Japanese flounder (Paralichthys olivaceus), the cDNAs encoding GTH-Ibeta and -IIbeta from the pituitary gland have been cloned and sequenced. The nucleotide sequence of GTH-Ibeta was 542 bp long, encoding 120 amino acids, and that of GTH-IIbeta was 554 bp long, encoding 145 amino acids. In females, Northern blot analysis has revealed that relative mRNA levels of GTH-Ibeta and -IIbeta were low in immature fish, showed a gradual increase with ovarian development, and reached the highest level at the maturation stage. Both GTH-Ibeta and -IIbeta mRNA levels were highly correlated with gonadosomatic index (GSI) values and with circulating estradiol-17beta and testosterone (T) levels. In males, the mRNA levels of GTH-Ibeta increased with the increase in GSI values and in circulating 11-ketotestosterone and T levels, whereas the mRNA levels of GTH-IIbeta did not show any correlation with GSI values and with circulating steroid levels, suggesting a difference in regulatory mechanisms of GTH-I and -II synthesis in males. The similar changes in GTH-Ibeta and -IIbeta mRNA levels during oogenesis are considered to be characteristic of GTH synthesis in multiple spawners, differing from the differential changes reported in annual spawners such as salmonids.

Amino Acid Sequence↗
PubMed1994

Transgenerational, ultrastructural analysis on the antioxidative effects of tocopherol on early gametogenesis in Caenorhabditis elegans grown in 100% oxygen.

The random, free-radical-mediated oxidations of biological molecules result in membrane degradation leading to cellular deterioration (B. Halliwell, Free Radical Res. Commun. 9, 1-32, 1990). External oxygen, prooxidants, and internally produced oxygen free radicals (oxyradicals), interact and alter the nature of biomembranes. Antioxidants, e.g., tocopherol (Vitamin E), inhibit such oxidative damage of free radicals. In the present study, the nematode Caenorhabditis elegans was grown under hyperoxia (100% oxygen) with or without the addition of Vitamin E to the growth media. The nematodes were viable under such conditions for at least eight generations, although fecundity gradually decreased through successive generations, presumably due to genetic load. Vitamin E was also shown to have a protective effect against paraquat, which is a strong, intracellular, oxidizing agent. Ultrastructural observations of early meiosis showed that the formation of synaptonemal complexes was compromised and that the telomeres failed to attach to the nuclear envelope. Those nematodes grown in 100% oxygen with 200 micrograms/ml Vitamin E had normal meiotic structures and normal fecundity. Thus, the presence of enhanced levels of intracellular Vitamin E resulted in protection against oxidative stress during gametogenesis.

Animals↗
PubMed2002

Induction of gametogenesis in the basal cnidarian Nematostella vectensis(Anthozoa).

A protocol was established to reproducibly induce spawning in the basal cnidarian Nematostella vectensis (Anthozoa). We found that a combination of feeding regime, dark-light cycle and temperature shift synergistically induced gametogenesis in adult polyps. Females lay between 100-600 eggs. This procedure led reproducibly to the production of thousands of eggs over the course of more than 1 year in weekly cycles. Gametes are released in a time window of about 2 h resulting in predictable and fairly synchronized development. We also present a method for in vitro fertilization allowing manipulation of early embryos. These methods as well as the simple culture conditions could provide important prerequisites for the use of Nematostella as a model system for the development of a basal Metazoa.

Animals↗
PubMed2005

Alfalfa Mob 1-like genes are expressed in reproductive organs during meiosis and gametogenesis.

Mps-one-binder (Mob) proteins play an important role in chromosome separation and cell plate formation in yeast. We cloned two Mob 1-like genes from alfalfa (Medicago sativa L.) and show that one gene is constitutively expressed while the other is expressed only in flower buds during sporogenesis and gametogenesis. For the analysis of gene expression during reproduction in alfalfa wild-types and apomeiotic mutants, a specific antisense riboprobe was designed for MsMob 1 transcripts and a polyclonal antibody was raised against MsMob 1 proteins. In situ mRNA localization as well as protein immunolocalization proved that MsMob1-like genes are specifically expressed in degenerating megaspores of normal ovules and in enlarged megaspore mother cells and embryo sacs of apomeiotic ovules. Gene products were also found in microspore tetrads at the beginning of pollen development as well as in tapetum cells of anthers undergoing programmed cell death to allow pollen dispersal at maturity. Overall results suggest that MsMob 1-like genes can play a key role during the reproductive pathway in plants.

Amino Acid Sequence↗
PubMed1992

Sex steroid levels in the testes, ovaries, and pyloric caeca during gametogenesis in the sea star Asterias vulgaris.

The concentrations of progesterone, testosterone, and estradiol were determined via radioimmunoassay in testes, ovaries, and pyloric caeca of the sea star Asterias vulgaris during one complete and two partial gametogenic cycles. These compounds were found in all tissues examined and were present in quantities similar to those reported previously in other echinoderms and in vertebrates. Testes and ovaries exhibited annual growth cycles during which testicular and ovarian mass increased up to 100-fold as gametes were produced and stored until spawning. Pyloric caecal mass varied during the annual reproductive season; however, no seasonal trends were apparent. In the testes, sex steroid levels were highest at the onset of spermatogenesis. Transient increases in the levels of estradiol coincided with spermatogonial mitotic proliferation. Transient increases in the levels of testosterone and progesterone in the testes coincided with spermatogenic column formation and with spermiogenesis, respectively. In the ovaries, estradiol and testosterone levels were highest at the onset of oogenesis while progesterone levels did not change significantly throughout the annual gametogenic cycle. Male and female pyloric caeca exhibited similar seasonal variations in levels of sex steroids as compared with the gonads. It is hypothesized that transient increases in the levels of sex steroids during gametogenesis may serve as endogenous modulators of reproduction.

Animals↗
PubMed1988

Roles of cell junctions in gametogenesis and in early embryonic development.

Recent reviews of the role of cell junctions in development have focused primarily upon functions related to the relatively subtle physiological modulation of their subunits in relation to fundamental developmental processes in a wide variety of organisms. There is, however, considerable support from numerous laboratories that the more radical modulation of the presence and number of junctional subunits in many diverse tissues may play a pivotal role in a wide spectrum of developmental phenomena ranging from gametogenesis to organogenesis. Since a great deal of recent interest in this latter subject has concentrated upon vertebrate systems including mammals, this review will examine the functional significance of the modulation of gap junctions, tight junctions and desmosomes in a developing idealized mammalian system from gamete formation to tissue and organ differentiation during embryo-genesis.

Animals↗
PubMed1991

Parental-specific methylation of an imprinted transgene is established during gametogenesis and progressively changes during embryogenesis.

Genomic imprinting is a regulatory process that requires a cell to recognize the parental origin of alleles. To understand how these alleles are distinguished, we have assessed changes in the DNA methylation of an imprinted transgene as it switches from one inheritance pattern to another while moving through gametogenesis and embryogenesis. We find that both maternally and paternally inherited methylation patterns are erased in primordial germ cells and that distinctive patterns emerge during germ cell maturation. In the case of the maternal allele, the methylation pattern is fully acquired during oogenesis. In the case of the paternal allele, the methylation pattern found in sperm undergoes further modification during embryogenesis. Thus, the distinction between "erased" maternal and paternal alleles is first established during their residence in different germ cells and then may be maintained by the recognition of the distinctive patterns that each allele displays in the zygote.

Alleles↗
PubMed1991

Molecular analysis of male gametogenesis in plants.

Reproduction in plants rivals the complexity of the process in animals. Recently, several genes that are expressed at specific stages during male gametogenesis have been cloned. These anther-specific genes are providing tools with which to study the cis- and trans-acting factors that regulate gene expression during pollen formation. Sequence analysis of the coding regions of some of these abundantly expressed anther genes is providing unexpected insights into the cell-cell interactions occurring during gamete formation and fertilization.

Cloning, Molecular↗
PubMed2005

Developmental expression of ASG- 1 during gametogenesis in apomictic guinea grass (Panicum maximum).

We have used Western blue-visualized in situ-hybridization (ISH) to monitor the expression of apomixis-specific gene-1 (ASG-1, GenBank accession number AB000809) during gametogenesis in obligate-sexual and facultative-apomictic (aposporic) genotypes of guinea grass (Panicum maximum). The in situ-analysis revealed that ASG-1 is not expressed in the ovule during early floral development in both, the facultative apomicts (A1 stage) and the obligate sexuals (S1 stage). With the appearance of the aposporous initial cell(s) in the ovule of the apomictic type (A2-1 stage), ASG-1 expression is strong and specific to this apomixis-specific cell. ASG-1 expression continued through different stages of aposporous embryo sac development (A2-2 stage), indicating that the gene may play a role in this developmental process. Regular embryo sacs in sexual types did not show hybridization signals (S2 stage). However, strong ASG-1 expression was detected in immature pollen grains and young embryos in both reproductive types, suggesting that ASG-1 may be an allele derived from the obligate-sexual wild type. Expression in pollen grains faded with maturation. In a heterologous system, using Paspalum notatum, a facultative-aposporic tropical grass (bahia grass), identical results were obtained. The results are discussed in view of the fact, that ASG-1 shows some homology to genes known to be seed- or embryo-specific or involved in processes related to cell growth.

Gametogenesis↗
PubMed1999

Structural and functional characteristics of the centrosome in gametogenesis and early embryogenesis of animals.

We present a description of the wide spectrum of centrosome behavior during gametogenesis, early development, and cell differentiation. During meiosis and terminal differentiation of gametes there occurs a process of centrosome maturation which includes alterations in characteristics such as the number of centriolar cylinders and their structure if the basal body is formed and ability to function as MTOC, reduplicate, split, and serve as a polar organizer. Such centrosome properties require modifications of the molecular composition. Maturation of the centrosome in gametes may be compared to transformation of centrosome characteristics during terminal differentiation of other cells. After fertilization different properties of maternal and paternal centrosomes are supposed to combine, adding to each other in the fused (hybrid) centrosome of a zygote. Restoration of centrosome features typical in diploid somatic cells takes place in cells of a developing embryo in the course of early cell cycles.

Animals↗
PubMed1994

Studies on the karyotype and gametogenesis in Trichuris muris.

The cytological study of males and females of Trichuris muris (Schrank, 1788) revealed the diploid number of chromosomes to be 2n = 6. The sex determining mechanism was XX female/XY male. All the chromosomes were subtelocentric. Sex chromosomes formed the smallest pair, but X and Y were difficult to distinguish morphologically. Chromosome changes during gametogenesis in both sexes followed a classical pattern except in the male prophase and metaphase I. Four male autosomes formed two bivalents, each with one proximal chiasma with strict localization, while sex chromosomes X and Y formed two univalents. Female chromosomes formed three rod bivalents of normal type, which possessed three, two and two chiasmata.

Animals↗
PubMed1998

Murine NIMA-related kinases are expressed in patterns suggesting distinct functions in gametogenesis and a role in the nervous system.

NIMA protein kinase is a major regulator of progression into mitosis in Aspergillus nidulans. Dominant negative forms of NIMA protein prevent entrance into mitosis in HeLa cells, suggesting that mammals have a similar pathway. We have reported previously the isolation of a murine NIMA-related kinase, designated Nek1, and more recently several additional NIMA-related human kinases have been cloned. The existence of several mammalian NIMA-related genes raises the questions of whether the different mammalian members have redundant, overlapping or distinct functions, and whether these functions are related to the role of NIMA in controlling mitosis. To address these questions we have studied the expression patterns of the different murine nek genes. To this end, we isolated a murine nek2 cDNA and compared its patterns of expression, during both gametogenesis and embryogenesis, to those of nek1. Both genes were highly expressed in developing germ cells, albeit in distinct patterns. In both females and males, nek1 is expressed much earlier than nek2, suggesting only limited ability for functional redundancy. Surprisingly, a striking specificity of nek1 expression was found: high levels of nek1 RNA were observed in distinct regions of the nervous system, most notably in neurons of the peripheral ganglia. These patterns suggest that the different mammalian NIMA-related kinases participate in different phases of the meiotic process and may also have functions other than cell cycle control.

Amino Acid Sequence↗
PubMed1997

Cloning and characterization of LRG5, a gene involved in blue light signaling in Chlamydomonas gametogenesis.

The Chlamydomonas reinhardtii mutant lrg2 exhibits a partial defect in the blue-light activated signal transduction chain that controls gametogenesis. By genomic complementation, a cosmid clone that corrects the lrg2 phenotype was isolated. The smallest fragment of this cosmid that gave complementation was used in RFLP analysis, which revealed that the cloned gene was not linked to the LRG2 locus. The sequence of the genomic clone and a cDNA of this gene, which we named LRG5, was determined. Although no significant homology with sequences in the databases was found, the nuclear localization signal and the presence of negatively and positively charged domains suggests a function for the LRG5 protein in the regulation of transcription. The correction of the lrg2 phenotype is probably caused by overexpression of the LRG5 gene in the transformants, as these expressed a level of LRG5 approximately twofold higher than wild-type or mutant strains. Southern blot analysis provided evidence for the existence of homologous sequences in other green algae as well as in higher plants, suggesting a conserved function for the LRG5 protein.

Amino Acid Sequence↗
PubMed2001

The Arabidopsis MALE STERILITY1 (MS1) gene is a transcriptional regulator of male gametogenesis, with homology to the PHD-finger family of transcription factors.

We report here the molecular characterisation of the Arabidopsis MALE STERILITY1 gene, which is a critical sporophytic controlling factor for anther and pollen development. Homozygous ms1 mutants do not produce viable pollen, but are otherwise phenotypically normal. Degeneration of pollen occurs soon after microspore release from the tetrads, at which time the tapetum also appears abnormally vacuolated. The MS1 gene is expressed at low levels in anthers from closed buds, with expression in the tapetum at the stage of microspore release. No expression is seen in open flowers. The deduced MS1 protein sequence shows strong homology to the PHD-finger motif found in known transcription factors from humans, yeast and higher plants. Six alleles of ms1 have been identified; all result in premature termination of the MS1 protein and loss of the PHD-finger motif. MS1 is likely to play a key role in regulating transcription during specific stages of male gametogenesis and anther development. As such, MS1 provides a valuable tool for the manipulation of male sterility in higher plants.

Amino Acid Motifs↗