In eukaryotes, diploid cells give rise to haploid cells via meiosis, a program of two cell divisions preceded by one round of DNA replication. Although key molecular components of the meiotic apparatus are highly conserved among eukaryotes, the mechanisms responsible for initiating the meiotic program have diverged substantially among eukaryotes. This raises a related question in animals with two distinct sexes: Within a given species, are similar or different mechanisms of meiotic initiation used in the male and female germ lines? In mammals, this question is underscored by dramatic differences in the timing of meiotic initiation in males and females. Stra8 is a vertebrate-specific, cytoplasmic factor expressed by germ cells in response to retinoic acid. We previously demonstrated that Stra8 gene function is required for meiotic initiation in mouse embryonic ovaries. Here we report that, on an inbred C57BL/6 genetic background, the same factor is also required for meiotic initiation in germ cells of juvenile mouse testes. In juvenile C57BL/6 males lacking Stra8 gene function, the early mitotic development of germ cells appears to be undisturbed. However, these cells then fail to undergo the morphological changes that define meiotic prophase, and they do not display the molecular hallmarks of meiotic chromosome cohesion, synapsis and recombination. We conclude that, in mice, Stra8 regulates meiotic initiation in both spermatogenesis and oogenesis. Taken together with previous observations, our present findings indicate that, in both the male and female germ lines, meiosis is initiated through retinoic acid induction of Stra8.
While advancements in informational technologies have provided nearly instant access to scientific data and information, ready and available access to research materials remains a problem for many in the research community. Issues such as a lack of lab resources or the loss of published materials can create practical impediments to sharing, while in other cases, prolonged legal negotiations over the sharing terms can create administrative ones. Addgene’s founders set out to create an effective platform that would address these issues to make sharing easier between scientists. Like many startups and nonprofit organizations, Addgene faced many hurdles such as community adoption and financial stability. However, Addgene’s commitment to its mission and its perseverance eventually led to the widespread adoption of Addgene’s services by the research community. By delivering an efficient, streamlined process for scientists and their technology transfer offices, the research community has since come to view Addgene as a trusted and vital research resource and one that continues to hone its efforts in making it easier for scientists to share their research materials. Keywords: material transfer agreements, MTA, plasmids, sharing, repository, nonprofit, self sustainable, efficient systems, uniform biological material transfer agreement, UBMTA.
Significance As male sex cells mature into sperm, two pivotal transitions are spermatogonial differentiation (exit from the stem cell pool) and meiotic initiation. These transitions occur in physical proximity, with 8.6-d periodicity. We report that the gene Stra8 , essential for meiotic initiation, also promotes (but is not required for) spermatogonial differentiation. Moreover, injected RA induces both transitions to occur precociously. We conclude that a periodic RA signal, acting instructively through the common target Stra8 , coordinates these transitions. This RA signal intersects with two distinct windows of sex-cell competency, which both begin while RA levels are low; sex cells respond quickly to rising RA. These mechanisms help account for the elaborate organization of sperm production, and its prodigious output.
Abstract Background 17 human-derived Clostridium strains (VE202), belonging to a bacterial cluster under-represented in active IBD, induce colonic IL-10-producing FOXP3+ regulatory T cells and prevent colitis in murine IBD models (Nature 2013). The VE202 consortium is a promising live biotherapeutic product for clinical application. However, its 1) therapeutic benefit on established colitis and 2) effect on intestinal microbiota composition remain unclear. Methods Models: We established colitis in ex-germ-free (exGF) Rag2−/− mice with naïve T cell transfer (Hu-nT) and Il10−/− (Hu-Il10−/−) mice colonized with healthy human fecal microbiota, using stool with low abundance of Clostridiales. In Hu-Il10−/−, we tested two other healthy donor stools (one with low Clostridiales and another with Fusobacteria, which is a potential pathobiont in IBD). For a selected bacteria-colonized model, we selected three aggressive Enterobacteriaceae strains cultured from the human donor stool used for the previous studies, based on colonic Th1 response and colitis in monoassociated exGF-Il10−/−. We then established an aggressive Klebsiella (K), Enterobacter (E) and E. coli (E) strain -colonized exGF Il10−/− colitis model (KEE-colitis). In addition, we established a human IBD-derived E.coli and Fusobacterium varium consortium-colonized Il10−/− (EF-colitis) model. In vitro, we anaerobically co-cultured human stools with VE202 and analyzed bacterial composition. Therapy: We treated mice by oral administration of VE202 or vehicle twice weekly for 2–4 weeks. Evaluation: Colitis severity was assessed by blinded histological score, fecal lipocalin-2, stool consistency score and colonic IFNγ +CD4+ T cells. Bacteria profiles in cecal contents were analyzed by metagenomics or qPCR. Results Hu-nT and Hu-Il10−/− (Fig.1A, B): VE202 significantly reversed histological colitis and other inflammatory endpoints compared to vehicle. Consistently VE202 attenuated colitis induced by three different donor stools. Bacteria profiling revealed that VE202 attenuated the colitis-associated bloom of Enterobacteriaceae and Fusobacteria. In KEE-colitis (Fig.1C) VE202 reversed colitis with reduction of all Enterobacteriaceae strains. In EF-colitis (Fig.1D) VE202 reversed colitis with reduction of E. coli and F. varium. Co-culture (Fig.1E): VE202 reduced abundance of Enterobacteriaceae in a dose dependent manner. Conclusion Our findings suggest a novel IL-10-independent protective mechanism for human Clostridium VE202 strains, i.e. correction of dysbiosis with reduction of levels of Enterobacteriaceae and Fusobacteria. In addition, VE202 treatment is consistently effective for different human donor microbiota in vivo and in vitro. These results provide a rationale and target for therapeutic use of rationally selected resident protective bacterial cocktails in IBD patients.
