Embryonic poly(A)-binding protein interacts with translation-related proteins and undergoes phosphorylation on the serine, threonine, and tyrosine residues in the mouse oocytes and early embryos

Expression of the embryonic poly(A)-binding protein (EPAB) in frog, mouse, and human oocytes and early-stage embryos is maintained at high levels until embryonic genome activation (EGA) after which a significant decrease occurs in EPAB levels. Studies on the vertebrate oocytes and early embryos revealed that EPAB plays key roles in the translational regulation, stabilization, and protection of maternal mRNAs during oocyte maturation and early embryogenesis. However, it remains elusive whether EPAB interacts with other cellular proteins and undergoes phosphorylation to perform these roles. For this purpose, we identified a group of Epab-interacting proteins and its phosphorylation status in mouse germinal vesicle (GV)- and metaphase II (MII)-stage oocytes, and in 1-cell, 2-cell, and 4-cell preimplantation embryos. In the oocytes and early preimplantation embryos, Epab-interacting proteins were found to play roles in the translation and transcription processes, intracellular signaling and transport, maintenance of structural integrity, metabolism, posttranslational modifications, and chromatin remodeling. Moreover, we discovered that Epab undergoes phosphorylation on the serine, threonine, and tyrosine residues, which are localized in the RNA recognition motifs 2, 3, and 4 or C-terminal. Conclusively, these findings suggest that Epab not only functions in the translational control of maternal mRNAs through binding to their poly(A) tails but also participates in various cellular events through interacting with certain group proteins. Most likely, Epab undergoes a dynamic phosphorylation during the oocyte maturation and the early embryo development to carry out these functions.

ZGLP1 is a determinant for the oogenic fate in mice

Sex determination of germ cells is vital to creating the sexual dichotomy of germ cell development, thereby ensuring sexual reproduction. However, the underlying mechanisms remain unclear. Here, we show that ZGLP1, a conserved transcriptional regulator with GATA-like zinc fingers, determines the oogenic fate in mice. ZGLP1 acts downstream of bone morphogenetic protein, but not retinoic acid (RA), and is essential for the oogenic program and meiotic entry. ZGLP1 overexpression induces differentiation of in vitro primordial germ cell-like cells (PGCLCs) into fetal oocytes by activating the oogenic programs repressed by Polycomb activities, whereas RA signaling contributes to oogenic program maturation and PGC program repression. Our findings elucidate the mechanism for mammalian oogenic fate determination, providing a foundation for promoting in vitro gametogenesis and reproductive medicine.

Expression analysis and characterization of zglp1 in the Chinese tongue sole (Cynoglossus semilaevis)

Zinc finger GATA like protein-1 (ZGLP1) is a nuclear zinc finger protein that regulates the interaction between somatic cells and germ cells during gonad developmental process in mammals. In this study, the zglp1 of Chinese tongue sole, Cynoglossus semilaevis (cysezglp1), was cloned and characterized for the first time in fish. Cysezglp1 had an open reading frame with five exons and was located to chromosome 9. The open reading frame of cysezglp1 consisted of 1692 nucleotides and encoded a 583 amino acid polypeptide. The predicted protein contained two zinc finger structures (Znf1 and Znf2), one of which was highly homologous to the GATA-type zinc finger domain. Multiple sequence alignment showed that Znf1 was conserved across different species while Znf2 was more divergent. Through quantitative Real-time PCR (qRT-PCR), we found that cysezglp1 was predominantly expressed in gonads, and the expression level of the ovary was significantly higher than that of the testis. We compared expression level in different embryonic stages and found that cysezglp1 mRNAs were mainly expressed in the fertilized egg to the cleavage stage, subsequently declining in the blastula stage. Cysezglp1 expression was not detected from the gastrulation stage onward. In the ovary, cysezglp1 expression was detected at 120 days after hatching and expression gradually increased with the maturation of the ovary. In situ hybridization showed that the cysezglp1 was mainly expressed in oocytes. Taken together, our results suggest that cysezglp1 may play an important role in the process of oogenesis in Chinese tongue sole.

A novel GATA-like zinc finger transcription factor involving in hematopoiesis of Eriocheir sinensis

GATA transcription factor is a family of DNA-binding proteins that can recognize and bind to sequence of (A/T) GATA (A/G). In the present study, a GATA-like protein (named as EsGLP) was characterized from Eriocheir sinensis, including an 834 bp full length open reading frame of EsGLP, encoding a polypeptide of 277 amino acids. The deduced amino acid sequence of EsGLP contained one conserved GATA-type zinc finger of the form Cys-X2-Cys-X17-Cys-X2-Cys, with four cysteine sites. The EsGLP mRNA transcripts were mainly detected in the hematopoietic tissue, hepatopancreas and gonad. The recombinant EsGLP protein was prepared for the antibody production. The EsGLP protein was mainly distributed in the edge of lobules in the HPT and the cytoplasm of hemocytes. The mRNA transcripts of EsGLP in hemocytes were significantly decreased at 24 h (0.39-fold and 0.27-fold, p < .05) and 48 h (0.35-fold and 0.16-fold, p < .05) after LPS and Aeromonas hydrophila stimulation, respectively. However, one peak of EsGLP mRNA transcripts were recorded at 24 h (8.71-fold, p < .05) in HPT after A. hydrophila stimulation. The expression level of EsGLP mRNA in HPT was significantly up-regulated at 2 h, 2.5 h and 9 h (41.74-fold, 45.38-fold and 26.07-fold, p < .05) after exsanguination stimulation. When EsGLP gene expression was inhibited by the injection of double-stranded RNA, both the total hemocytes counts and the rate of EdU-positive hemocytes were significantly decreased (0.32-fold and 0.56-fold compared to that in control group, p < .05). All these results suggested that EsGLP was an important regulatory factor in E. sinensis which involved in the hemocytes generation and the immune response against invading pathogens.

Polarity Protein Scrib Facilitates Endothelial Inflammatory Signaling

OBJECTIVE

The polarity protein Scrib is highly expressed in endothelial cells and is required for planar cell polarity. Scrib also facilitates recycling of integrin α5 to the plasma membrane. Because integrin α5 signals the presence of the inflammatory matrix protein fibronectin, we hypothesized that Scrib contributes to endothelial inflammatory signaling.

APPROACH AND RESULTS

Cytokine treatment of human umbilical vein endothelial cells induced an inflammatory response as evident by the induction of vascular cell adhesion molecule-1 (VCAM-1). Downregulation of Scrib greatly attenuated this effect. In endothelial-specific conditional Scrib knockout mice, in vivo lipopolysaccharide treatment resulted in an impaired VCAM-1 induction. These effects were functionally relevant because Scrib small interfering RNAs in human umbilical vein endothelial cells attenuated the VCAM-1-mediated leukocyte adhesion in response to tumor necrosis factor-α. In vivo, tamoxifen-induced endothelial-specific deletion of Scrib resulted in a reduced VCAM-1-mediated leukocyte adhesion in response to tumor necrosis factor-α in the mouse cremaster model. This effect was specific for Scrib and not mediated by other polarity proteins. Moreover, it did not involve integrin α5 or classic pathways supporting inflammatory signaling, such as nuclear factor κ light chain enhancer of activated B-cells or MAP kinases. Co-immunoprecipitation/mass spectrometry identified the zinc finger transcription factor GATA-like protein-1 as a novel Scrib interacting protein. Small interfering RNA depletion of GATA-like protein-1 decreased the tumor necrosis factor-α-stimulated VCAM-1 induction to a similar extent as loss of Scrib did. Silencing of Scrib reduced GATA-like protein-1 protein, but not mRNA abundance.

CONCLUSIONS

Scrib is a novel proinflammatory regulator in endothelial cells, which maintains the protein expression of GATA-like protein-1.

Molecular signatures discriminating the male and the female sexual pathways in the pearl oyster Pinctada margaritifera

The genomics of economically important marine bivalves is studied to provide better understanding of the molecular mechanisms underlying their different reproductive strategies. The recently available gonad transcriptome of the black-lip pearl oyster Pinctada margaritifera is a novel and powerful resource to study these mechanisms in marine mollusks displaying hermaphroditic features. In this study, RNAseq quantification data of the P. margaritifera gonad transcriptome were analyzed to identify candidate genes in histologically-characterized gonad samples to provide molecular signatures of the female and male sexual pathway in this pearl oyster. Based on the RNAseq data set, stringent expression analysis identified 1,937 contigs that were differentially expressed between the gonad histological categories. From the hierarchical clustering analysis, a new reproduction model is proposed, based on a dual histo-molecular analytical approach. Nine candidate genes were identified as markers of the sexual pathway: 7 for the female pathway and 2 for the male one. Their mRNA levels were assayed by real-time PCR on a new set of gonadic samples. A clustering method revealed four principal expression patterns based on the relative gene expression ratio. A multivariate regression tree realized on these new samples and validated on the previously analyzed RNAseq samples showed that the sexual pathway of P. margaritifera can be predicted by a 3-gene-pair expression ratio model of 4 different genes: pmarg-43476, pmarg-foxl2, pmarg-54338 and pmarg-fem1-like. This 3-gene-pair expression ratio model strongly suggests only the implication of pmarg-foxl2 and pmarg-fem1-like in the sex inversion of P. margaritifera. This work provides the first histo-molecular model of P. margaritifera reproduction and a gene expression signature of its sexual pathway discriminating the male and female pathways. These represent useful tools for understanding and studying sex inversion, sex differentiation and sex determinism in this species and other related species for aquaculture purposes such as genetic selection programs.

Gonad transcriptome analysis of pearl oyster Pinctada margaritifera: identification of potential sex differentiation and sex determining genes

BACKGROUND

Black pearl farming is based on culture of the blacklip pearl oyster Pinctada margaritifera (Mollusca, lophotrochozoa), a protandrous hermaphrodite species. At first maturation, all individuals are males. The female sex appears progressively from two years old, which represents a limitation for broodstock conditioning for aquaculture production. In marine mollusks displaying hermaphroditic features, data on sexual determinism and differentiation, including the molecular sex determining cascade, are scarce. To increase genomic resources and identify the molecular mechanisms whereby gene expression may act in the sexual dimorphism of P. margaritifera, we performed gonad transcriptome analysis.

RESULTS

The gonad transcriptome of P. margaritifera was sequenced from several gonadic samples of males and females at different development stages, using a Next-Generation-Sequencing method and RNAseq technology. After Illumina sequencing, assembly and annotation, we obtained 70,147 contigs of which 62.2% shared homologies with existing protein sequences, and 9% showed functional annotation with Gene Ontology terms. Differential expression analysis identified 1,993 differentially expressed contigs between the different categories of gonads. Clustering methods of samples revealed that the sex explained most of the variation in gonad gene expression. K-means clustering of differentially expressed contigs showed 815 and 574 contigs were more expressed in male and female gonads, respectively. The analysis of these contigs revealed the presence of known specific genes coding for proteins involved in sex determinism and/or differentiation, such as dmrt and fem-1 like for males, or foxl2 and vitellogenin for females. The specific gene expression profiles of pmarg-fem1-like, pmarg-dmrt and pmarg-foxl2 in different reproductive stages (undetermined, sexual inversion and regression) suggest that these three genes are potentially involved in the sperm-oocyte switch in P. margaritifera.

CONCLUSIONS

The study provides a new transcriptomic tool to study reproduction in hermaphroditic marine mollusks. It identifies sex differentiation and potential sex determining genes in P. margaritifera, a protandrous hermaphrodite species.

Oogenesis: transcriptional regulators and mouse models

Oocyte differentiation into a totipotent cell requires initial germ cell cyst breakdown to form primordial follicles, recruitment of primordial follicles for development into primary follicles and remarkable growth of the ovarian follicle which culminates in ovulation. During oogenesis, the oocyte undergoes dynamic alterations in gene expression which are regulated by a set of well-coordinated transcription factors active in the germ line and soma. A number of germ cell specific as well as somatic expressed transcriptional regulators are critical in ovarian formation and folliculogenesis. These transcriptional regulators include: Foxo3, Foxl2, Figla, Lhx8, Nobox, Sohlh1 and Sohlh2. A subset of these transcriptional regulators is mutated in women with ovarian insufficiency and infertility. Studies on transcriptional regulators preferentially expressed in the ovary are important to develop a better understanding of the mechanisms of activation and survival of ovarian follicles, as well as an understanding of ovary specific pathways that can be modulated in the future to regulate fertility and protect against external insults such as chemotherapy.