Function of Nanos2 in the male germ cell lineage in mice

Nanos is known as an evolutionarily conserved RNA-binding protein, the function of which is implicated in germ cell development. This includes the maintenance of both the primordial germ cells (PGCs) and germline stem cells. In mice, Nanos2 exhibits a unique feature in which its expression is induced only in the germ cells within the sexually determined male gonad. Nanos2 promotes male germ cell differentiation, while simultaneously suppressing a female program. In addition, Nanos2 is also expressed in the spermatogonial stem cells and functions as an intrinsic factor to maintain the stem cell population during spermatogenesis. Detailed cytological and biochemical analyses in embryonic male gonads in the mouse have revealed that Nanos2 localizes to the P-bodies, a center of RNA processing. It has also been shown that the Nanos2 interacts with protein components of the deadenylation complex involved in the initial step of the RNA degradation pathway.     

Heat stress response of male germ cells

The vast majority of mammalian testes are located outside the body cavity for proper thermoregulation. Heat has an adverse effect on mammalian spermatogenesis and eventually leads to sub- or infertility. Recent studies have provided insights into the molecular response of male germ cells to high temperatures. Here, we review the effects of heat on male germ cells and discuss the mechanisms underlying germ cell loss and impairment. We also discuss the role of translational control in male germ cells as a potential protective mechanism against heat-induced germ cell apoptosis.     

Production of transgenic birds

The avian embryo presents a tremendous challenge for those interested in accessing and manipulating the avian germ line. By far the most successful method of gene transfer is by retrovirus vector. The efficacy of retrovirus vectors has been demonstrated by germ line insertion of replication-competent retroviruses as well as the insertion of replication-defective retrovirus vectors carrying bacterial marker genes. Retroviral vectors have also been shown to be useful for the transfer and expression of genes in somatic cells. Further, germ line transgenesis has been reported in both the chicken and the Japanese quail. In addition, several alternative gene transfer methods are under development. These include transfection of avian sperm, development of germ line chimeras using primordial germ cells and blastodermal cells, and the development of embryonic stem cell lines. Potentially, basic research and the poultry industry will derive substantial benefit from this revolutionary technology.     

Production of transgenic birds

The avian embryo presents a tremendous challenge for those interested in accessing and manipulating the avian germ line. By far the most successful method of gene transfer is by retrovirus vector. The efficacy of retrovirus vectors has been demonstrated by germ line insertion of replication-competent retroviruses as well as the insertion of replication-defective retrovirus vectors carrying bacterial marker genes. Retroviral vectors have also been shown to be useful for the transfer and expression of genes in somatic cells. Further, germ line transgenesis has been reported in both the chicken and the Japanese quail. In addition, several alternative gene transfer methods are under development. These include transfection of avian sperm, development of germ line chimeras using primordial germ cells and blastodermal cells, and the development of embryonic stem cell lines. Potentially, basic research and the poultry industry will derive substantial benefit from this revolutionary technology.     

Differential lethality in developmental stages ofDrosophila following X-irradiation

Summary ADrosophila melanogaster line has been treated with ionizing radiations. The dose-response relationship has been studied upon separate treatment of male and female gametes. The results show that while the total survival is similar, at different developmental stages differences can be observed between progenies from treated male and female gametes. It is suggested that developmental patterns may affect the expression of induced mutations.     

Adenylate storage,metabolism and utilization in coelomic cells of the polychaeteNereis virens (Annelida,polychaeta)

Eleocytes are specialized coelomic cells in nereid annelids which assume a central role during germ cell development. They may contain extremely high concentrations of both adenosine monophosphate (AMP) and adenosine diphosphate (ADP) (each >10 mol/ml of cell vol.), whereas the adenosine triphosphate (ATP) content is comparatively low (0.8 mol/ml cell vol.).³¹P nuclear magnetic, resonance (NMR) studies of living eleocytes suggest the compartmentalization of both AMP and ADP in the large acidic vacuole characteristic for this cell type. Eleocytes are thus capable of storing high concentrations of ADP and AMP without inhibiting energy metabolism, by sequestering these compounds in a separate compartment. The high concentrations of both AMP and ADP in the eleocytes decrease in both males and females during the course of maturation. In eleocytes of male animals, the decline of the high nucleotide concentrations was accompanied by a transient increase of two intracellular nucleosides, inosine and guanosine. This suggests the degradation and further metabolism of nucleotides to the corresponding nucleosides. In culture, eleocytes release both inosine and guanosine into the medium. Both nucleosides are also present in the coelomic fluid, the common compartment for both eleocytes and germ cells. Both male and female germ cells incorporate¹⁴C-labelled inosine and guanosine in culture. For oocytes, the further incorporation of [¹⁴C]inosine into the RNA fraction could be demonstrated. The large adenylate pools in the eleocytes may be regarded as a store for purine compounds for later use by the growing germ cells to supplement nucleic acid synthesis. The supply of nucleic acid precursors seems to be another specific function of eleocytes related to gametogenesis, in addition to their known synthesis of vitellogenin.     

Cadherin 22 participates in the self-renewal of mouse female germ line stem cells via interaction with JAK2 and β-catenin

The self-renewal capacity of the stem cell pool determines tissue function and health. Cadherin-22 (Cdh22), a member of the cadherin superfamily, has two splicing patterns in rats, and the short type that lacks a catenin binding domain is closely related to spermatogonial stem cell self-renewal. Previously, we reported that CDH22 was highly expressed in mouse ovary germ cells, especially in female germ line stem cells (FGSCs). However, its underlying function in FGSCs is still not clear. Here, we found that Cdh22 encodes only one type of protein product in mice and demonstrated that CDH22 was required for FGSC self-renewal. In addition, JAK2 and β-catenin were found to interact with CDH22 and be involved in CDH22 signaling in mouse FGSCs. Moreover, extrinsic CDH22 was identified as a potential molecule that participates in FGSC adhesion and is pivotal for FGSC maintenance and self-renewal. These results reveal that CDH22 functions as an essential molecule in FGSC maintenance and self-renewal via different mechanisms, including interaction with the JAK-STAT signaling pathway and β-catenin.     

Regulation of male sex determination: genital ridge formation and Sry activation in mice

Sex determination is essential for the sexual reproduction to generate the next generation by the formation of functional male or female gametes. In mammals, primary sex determination is commenced by the presence or absence of the Y chromosome, which controls the fate of the gonadal primordium. The somatic precursor of gonads, the genital ridge is formed at the mid-gestation stage and gives rise to one of two organs, a testis or an ovary. The fate of the genital ridge, which is governed by the differentiation of somatic cells into Sertoli cells in the testes or granulosa cells in the ovaries, further determines the sex of an individual and their germ cells. Mutation studies in human patients with disorders of sex development and mouse models have revealed factors that are involved in mammalian sex determination. In most of mammals, a single genetic trigger, the Y-linked gene Sry (sex determination region on Y chromosome), regulates testicular differentiation. Despite identification of Sry in 1990, precise mechanisms underlying the sex determination of bipotential genital ridges are still largely unknown. Here, we review the recent progress that has provided new insights into the mechanisms underlying genital ridge formation as well as the regulation of Sry expression and its functions in male sex determination of mice.     

Reactivation of the inactive X chromosome in development and reprogramming

In mammals, one of the two X chromosomes of female cells is inactivated for dosage compensation between the sexes. X chromosome inactivation is initiated in early embryos by the noncoding Xist RNA. Subsequent chromatin modifications on the inactive X chromosome (Xi) lead to a remarkable stability of gene repression in somatic cell lineages. In mice, reactivation of genes on the Xi accompanies the establishment of pluripotent cells of the female blastocyst and the development of primordial germ cells. Xi reactivation also occurs when pluripotency is established during the reprogramming of somatic cells to induced pluripotent stem cells. The mechanism of Xi reactivation has attracted increasing interest for studying changes in epigenetic patterns and for improving methods of cell reprogramming. Here, we review recent advances in the understanding of Xi reactivation during development and reprogramming and illustrate potential clinical applications.     

Physical growth and brain development of captive-bred male and female squirrel monkeys, Saimiri sciureus.

The physical growth and brain development of the captive bred male and female squirrel monkeys have shown that the male grows at a significantly faster rate with respect to these parameters in the postnatal life, starting from preweaning stage as compared to the female infant. During the prenatal life the male and the female fetuses grow at similar rates and show comparable brain development as indicated by its weight.     

Ultrastructural study of the first stages of ovarian post-embryonic differentiation of the paludin Viviparus viviparus L. (Mollusca, Gastropoda, Prosobranch of separate sexes)]

The young Paludin ovary, characterized by its tubular morphology, contains at birth two types of cells: the germinal ones, and others which give later follicular cells. There is no significant cytological difference between the primordial germinal cells of female and male gonad. Among the several cytologic criteria that allow one to distinguish the germinal line from the non germinal one, the most constant is the presence of septate junction between the non germinal cells.     

Effect of progesterone on male and female sex behavior induced by steroid hormones in adult ovariectomized ewes]

Ovariectomized adult Ewes daily treated with I/M injections of testosterone propionate (10 mg/day) or oestradiol benzoate (200 microgram/day) show male-like sexual behaviour and simultaneously a permanent female receptivity. Additional daily treatment with 100 mg of progresterone results in a rapid decrease in male sexual responses both when Ewes are treated with testosterone and with oestradiol. No effect is observed on the female receptivity. Cyproterone acetate (100 mg/day) given to Ewes in addition to daily injection of testosterone propionate (10 mg/day) has effects similar to those of progesterone. These results show that progesterone has antiandrogen and antioestrogen properties and that this hormone administered at high doses is able to inhibit male activity.     

Sex chromosome inactivation in germ cells: emerging roles of DNA damage response pathways

Sex chromosome inactivation in male germ cells is a paradigm of epigenetic programming during sexual reproduction. Recent progress has revealed the underlying mechanisms of sex chromosome inactivation in male meiosis. The trigger of chromosome-wide silencing is activation of the DNA damage response (DDR) pathway, which is centered on the mediator of DNA damage checkpoint 1 (MDC1), a binding partner of phosphorylated histone H2AX (γH2AX). This DDR pathway shares features with the somatic DDR pathway recognizing DNA replication stress in the S phase. Additionally, it is likely to be distinct from the DDR pathway that recognizes meiosis-specific double-strand breaks. This review article extensively discusses the underlying mechanism of sex chromosome inactivation.     

Physical growth and brain development of captive-bred male and female squirrel monkeys,Saimiri sciureus

Summary The physical growth and brain development of the captive bred male and female squirrel monkeys have shown that the male grows at a significantly faster rate with respect to these parameters in the postnatal life, starting from preweaning stage as compared to the female infant. During the prenatal life the male and the female fetuses grow at similar rates and show comparable brain development as indicated by its weight.Acknowledgments. This work was supported by USPHS Grants RR-00165 and HD-06087 from National Institutes of Health. The technical assistance of Mrs Judie Wells is greatly appreciated.     

Effects of injury on the concentration of alpha1-macroglobulin and alpha2-macroglobulin in the plasmas of male and remale rats.

The effects of injury on the concentration of alpha1-macroglobulin and alpha2-macroglobulin in the plasmas of male and remale rats has been investigates. At 5 days after injury to the male rats the alpha1-macroglobulin concentration increased to 131% of its preinjury value. The alpha2-macroglobulin concentration increased more rapidly to a maximum of 86 times its initial value. In the female rats alpha2-macroglobulin increased only slightly and alpha1-macroglobulin not at all.     

La synthèse de l'ADN prémitotique et préméiotique dans les cellules germinales de l'embryon femelle de la caille japonaise (Coturnix coturnix japonica)

Summary The premeiotic DNA synthesis of the female Japanese quail embryo begins after 9 days incubation. The germ cells in premeiotic S phase present a particular structure different from the structure found in germ cells during premitotic S phase. They are the precursors of the meiocytes in leptotene stage.

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L'auteur remercie vivement le ProfesseurL. Vakaet (R.U.C.A., Anvers) pour ses suggestions très valables.     

Comparison between serum LH and FSH levels in male and female rats during the perinatal period]

In the newborn female Rat, no transient LH and FSH serum surges were observed between 0 and 2 hrs., as compared with the newborn male. In the newborn female, a progressive increase in serum gonadotropins was observed between 2 and 6 hrs. These results indicate that, at birth, the pituitary-gonadal axis reacts in a different way in male and female Rats.     

Structure,function and evolution of haspin and haspinrelated proteins,a distinctive group of eukaryotic protein kinases

The haspins constitute a newly defined protein family containing a distinctive C-terminal eukaryotic protein kinase domain and divergent N termini. Haspin homologues are found in animals, plants and fungi, suggesting an origin early in eukaryotic evolution. Most species have a single haspin homologue. However, Saccharomyces cerevisiae has two such genes, while Caenorhabditis elegans has at least three haspin homologues and approximately 16 haspin-related genes. Mammalian haspin genes have features of retrogenes and are strongly expressed in male germ cells and at lower levels in some somatic tissues. They encode nuclear proteins with serine/threonine kinase activity. Murine haspin is reported to inhibit cell cycle progression in cell lines. One of the S. cerevisiae homologues, ALK1, is a member of the CLB2 gene cluster that peaks in expression at M phase and thus may function in mitosis. Therefore, the haspins are an intriguing group of kinases likely to have important roles during or following both meiosis and mitosis.     

A new cell line (XTY) from a tumor of Xenopus laevis.

A new cell line (XTY) was derived from a tumor of a female Xenopus laevis. This cell line has been proliferating in standard amphibian culture medium for more than 4 years (470 generations) and has a doubling time of 75.5 h at 25 degrees C. The cells aggregate into large groups, and their stellate morphology and the expression of desmin demonstrated by immunocytochemistry suggest that their origin is not epithelial.