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Histone H3 Lysine 9 (H3K9) methylation, a characteristic mark of heterochromatin, is progressively implemented during development to contribute to cell fate restriction as differentiation proceeds. Accordingly, in undifferentiated and pluripotent mouse Embryonic Stem (ES) cells the global levels of H3K9 methylation are rather low and increase only upon differentiation. How global H3K9 methylation levels are coupled with the loss of pluripotency remains largely unknown. Here, we identify SUV39H1, a major H3K9 di- and tri-methylase, as an indirect target of the pluripotency network of Transcription Factors (TFs). We find that pluripotency TFs, principally OCT4, activate the expression of Suv39h1as, an antisense long non-coding RNA to Suv39h1. In turn, Suv39h1as downregulates Suv39h1 transcription in cis via a mechanism involving the modulation of the chromatin status of the locus. The targeted deletion of the Suv39h1as promoter region triggers increased SUV39H1 expression and H3K9me2 and H3K9me3 levels, affecting all heterochromatic regions, particularly peri-centromeric major satellites and retrotransposons. This increase in heterochromatinization efficiency leads to accelerated and more efficient commitment into differentiation. We report, therefore, a simple genetic circuitry coupling the genetic control of pluripotency with the global efficiency of H3K9 methylation associated with a major cell fate restriction, the irreversible loss of pluripotency.

1. To address biodiversity declines within semi-natural habitats, land-management must cater for diverse taxonomic groups. Integrating our understanding of the ecological requirements of priority (rare, scarce or threatened) species through ‘biodiversity auditing’, with that of the intensity and complexity of historical land-use, encourages novel forms of management. Experimental confirmation is needed to establish whether this enhances biodiversity conservation relative to routine management. 2. Biodiversity auditing and historical land-use of dry-open terrestrial habitats in Breckland (Eastern England) both encourage management incorporating ground-disturbance and spatio-temporal variability. To test biodiversity conservation outcomes, we developed 40 4-ha management complexes over three successive winters, of which 20 were shallow-cultivated (rotovation) and 20 deep-cultivated (ploughing), stratified across 3,850-ha of closed-sward dry grassland and lowland heathland (collectively ‘dry grassland’). Complexes comprised four 1-ha sub-treatments: repeat-cultivation, first-time-cultivation, one-year-old fallow and two-year-old fallow. We examined responses of vascular plants; spiders; true bugs; ground, rove and ‘other’ beetles; bees and wasps; ants; and true flies on treatment complexes and 21 4-ha untreated controls. Sampling gave 132,251 invertebrates from 877 species and 28,846 plant observations from 167 species. 3. Resampling and rarefaction analyses showed shallow- and deep-cultivation both doubled priority species richness (pooling sub-treatments within complexes) compared to controls. Priority spider, ground beetle, other beetle, and true bug richness were greater on both treatments than controls. Responses were strongest for those priority dry-open-habitat associated invertebrates initially predicted (by biodiversity auditing) to benefit from heavy physical-disturbance. 4. Assemblage composition (pooling non-priority and priority species) varied between sub-treatments for plants, ants, true bugs, spiders, ground, rove and other beetles; but only one-year-old fallowed deep-cultivation increased priority richness across multiple taxa. 5. Treatments produced similar biodiversity responses across various dry grassland ‘habitats’ that differed in plant composition, allowing simplified management guidance. 6. Synthesis and applications. Our landscape-scale experiment confirmed the considerable biodiversity value of interventions inspired by history and informed by systematic multi-taxa analysis of ecological requirements across priority biota. Since assemblage composition varied between sub-treatments, providing heterogeneity in management will support the widest suite of species. Crucially, the intended recipients responded most strongly, suggesting biodiversity audits could successfully inform interventions within other systems.

We sampled 9 sites (5 free-flowing and 4 impounded) to investigate effects of lowhead dams on the habitat characteristics and the freshwater mussel assemblage of the Fox River in Illinois. We used 2 habitat indices, the Qualitative Habitat Evaluation Index (QHEI) and the Stream Habitat Assessment Protocol (SHAP), to determine effects of lowhead dams on habitat quality. Free-flowing sites had higher QHEI and SHAP scores than impounded sites, indicating higher quality stream habitat. We calculated 3 variables, catch-per-unit-effort (CPUE), extant spe- cies richness, and percent missing species, to establish effects of lowhead dams on freshwater mussels. Free-flowing sites had higher CPUE and extant species richness and lower percent missing species than impounded sites. We also examined literature reviews and museum collection holdings to determine species distributions within the basin. These data suggest that dams limit the upstream distribution of 5 species.

Polytropic murine leukemia viruses (MuLVs) are generated by recombination of ecotropic MuLVs with env genes of a family of endogenous proviruses in mice, resulting in viruses with an expanded host range and greater virulence. Inbred mouse strains contain numerous endogenous proviruses that are potential donors of the env gene sequences of polytropic MuLVs; however, the precise identification of those proviruses that participate in recombination has been elusive. Three different structural groups of proviruses in NFS/N mice have been described and different ecotropic MuLVs preferentially recombine with different groups of proviruses. In contrast to other ecotropic MuLVs such as Friend MuLV or Akv that recombine predominantly with a single group of proviruses, Moloney MuLV (M-MuLV) recombines with at least two distinct groups. In this study, we determined that only three endogenous proviruses, two of one group and one of another group, are major participants in recombination with M-MuLV. Furthermore, the distinction between the polytropic MuLVs generated by M-MuLV and other ecotropic MuLVs is the result of recombination with a single endogenous provirus. This provirus exhibits a frameshift mutation in the 3′ region of the surface glycoprotein-encoding sequences that is excluded in recombinants with M-MuLV. The sites of recombination between the env genes of M-MuLV and endogenous proviruses were confined to a short region exhibiting maximum homology between the ecotropic and polytropic env sequences and maximum stability of predicted RNA secondary structure. These observations suggest a possible mechanism for the specificity of recombination observed for different ecotropic MuLVs.

Mammalian genomes harbor a large number of retroviral elements acquired as germ line insertions during evolution. Although many of the endogenous retroviruses are defective, several contain one or more intact viral genes that are expressed under certain physiological or pathological conditions. This is true of the endogenous polytropic retroviruses that generate recombinant polytropic murine leukemia viruses (MuLVs). In these recombinants the env gene sequences of exogenous ecotropic MuLVs are replaced with env gene sequences from an endogenous polytropic retrovirus. Although replication-competent endogenous polytropic retroviruses have not been observed, the recombinant polytropic viruses are capable of replicating in numerous species. Recombination occurs during reverse transcription of a virion RNA heterodimer comprised of an RNA transcript from an endogenous polytropic virus and an RNA transcript from an exogenous ecotropic MuLV RNA. It is possible that homodimers corresponding to two full-length endogenous RNA genomes are also packaged. Thus, infection by an exogenous virus may result not only in recombination with endogenous sequences, but also in the mobilization of complete endogenous retrovirus genomes via pseudotyping within exogenous retroviral virions. We report that the infection of mice with an ecotropic virus results in pseudotyping of intact endogenous viruses that have not undergone recombination. The endogenous retroviruses infect and are integrated into target cell genomes and subsequently replicate and spread as pseudotyped viruses. The mobilization of endogenous retroviruses upon infection with an exogenous retrovirus may represent a major interaction of exogenous retroviruses with endogenous retroviruses and may have profound effects on the pathogenicity of retroviral infections.

During the past 12 years, spoolable pipe has become a widespread preference for in-field gathering and injection applications compared to welded steel and stick fibreglass pipelines. It is now broadly used in oil and gas fields throughout North America, with more than 300 end users, including every major operator. To date, more than 25,000 km of spoolable pipe has been installed in North America for more than 450 operators. Fast installation, lower costs, safer installation, immunity to corrosion and low maintenance in service are the drivers for this rapid success. The technology is well on its way to displacing steel or stick glass-fibre reinforced epoxy (GRE) pipe as the technology of choice for lines up to nominal 6-inch in diameter. Compared to a single 8- or 10-inch line, companies are finding having multiple spoolable pipes in the same ditch to be more economical. Field results have demonstrated spoolable pipe’s immunity to corrosion and have also shown how using spoolable pipes can save 25% or more in costs when compared to overall installed costs for welded steel or stick fibreglass pipelines by significantly reducing onsite construction expense, installation time and onsite manpower requirements, including skilled welding personnel.

In this issue of Stem Cell Reports, Hastreiter et al. (2018) use continuous time-lapse imaging of mouse embryonic stem cells to investigate how the inhibition of GSK3b and MEK/ERK (2i) leads to homogeneous expression of the transcription factor Nanog. They show that both induction of Nanog expression and selection against cells expressing low levels of Nanog contribute to the homogeneous appearance of 2i cultures. : In this issue of Stem Cell Reports, Hastreiter et al. (2018) use continuous time-lapse imaging of mouse embryonic stem cells to investigate how the inhibition of GSK3b and MEK/ERK (2i) leads to homogeneous expression of the transcription factor Nanog. They show that both induction of Nanog expression and selection against cells expressing low levels of Nanog contribute to the homogeneous appearance of 2i cultures.