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Lentiviral vectors that express a fluorescent reporter and a selectable marker in pluripotent cells improve and simplify isolation of induced pluripotent stem cell lines in mouse and human. Induced pluripotent stem (iPS) cells may be of use in regenerative medicine. However, the low efficiency of reprogramming is a major impediment to the generation of patient-specific iPS cell lines. Here we report the first selection system for the isolation of human iPS cells. We developed the EOS (Early Transposon promoter and Oct-4 ( Pou5f1 ) and Sox2 enhancers) lentiviral vector to specifically express in mouse and human embryonic stem cells but not in primary fibroblasts. The bicistronic EOS vector marked emerging mouse and human iPS cell colonies with EGFP, and we used puromycin selection to aid the isolation of iPS cell lines that expressed endogenous pluripotency markers. These lines differentiated into cell types from all three germ layers. Reporter expression was extinguished upon differentiation and therefore monitored the residual pluripotent cells that form teratomas. Finally, we used EOS selection to establish Rett syndrome–specific mouse and human iPS cell lines with known mutations in MECP2 .

We have observed karyotypic changes involving the gain of chromosome 17q in three independent human embryonic stem (hES) cell lines on five independent occasions. A gain of chromosome 12 was seen occasionally. This implies that increased dosage of chromosome 17q and 12 gene(s) provides a selective advantage for the propagation of undifferentiated hES cells. These observations are instructive for the future application of hES cells in transplantation therapies in which the use of aneuploid cells could be detrimental.

Heterogeneity is a feature of stem cell populations, resulting from innate cellular hierarchies that govern differentiation capability. How heterogeneity impacts human pluripotent stem cell populations is directly relevant to their efficacious use in regenerative medicine applications. The control of pluripotency is asserted by a core transcription factor network, of which Oct4 is a necessary member. In mouse embryonic stem cells (ESCs), the zinc finger transcription factor Rex1 (Zfp42) closely tracks the undifferentiated state and is capable of segregating Oct4 positive mESCs into metastable populations expressing or lacking Rex1 that are inter-convertible. However, little is currently understood about the extent or function of heterogeneous populations in the human pluripotent compartment. Human ESCs express REX1 transcripts but the distribution and properties of REX1 expressing cells have yet to be described. To address these questions, we used gene targeting in human ESCs to insert the fluorescent protein Venus and an antibiotic selection marker under the control of the endogenous REX1 transcription regulatory elements, generating a sensitive, selectable reporter of pluripotency. REX1 is co-expressed in OCT4 and TRA-1-60 positive hESCs and rapidly lost upon differentiation. Importantly, REX1 expression reveals significant heterogeneity within seemingly homogenous populations of OCT4 and TRA-1-60 hESCs. REX1 expression is extinguished before OCT4 during differentiation, but, in contrast to the mouse, loss of REX1 expression demarcates a stable, OCT4 positive lineage-primed state in pluripotent hESCs that does not revert back to REX1 positivity under normal conditions. We show that loss of REX1 expression correlates with altered patterns of DNA methylation at the REX1 locus, implying that epigenetic mechanisms may interfere with the metastable phenotype commonly found in murine pluripotency.

Remarkably little is known about the transcriptional profiles of human embryonic stem (ES) cells or the molecular mechanisms that underlie their pluripotency. To identify commonalties among the transcriptional profiles of different human pluripotent cells and to search for clues into the genesis of human germ cell tumors, we compared the expression profiles of human ES cell lines, human germ cell tumor cell lines and tumor samples, somatic cell lines, and testicular tissue samples by using cDNA microarray analysis. Hierarchical cluster analysis of gene expression profiles showed that the five independent human ES cell lines clustered tightly together, reflecting highly similar expression profiles. The gene expression patterns of human ES cell lines showed many similarities with the human embryonal carcinoma cell samples and more distantly with the seminoma samples. We identified 895 genes that were expressed at significantly greater levels in human ES and embryonal carcinoma cell lines than in control samples. These genes are candidates for involvement in the maintenance of a pluripotent, undifferentiated phenotype.

Maturation of the intestinal epithelium is a necessary step for development of a fully functioning gastrointestinal tract. Studies of rodent gastrointestinal development and maturation have long been used to guide understanding of human intestinal maturation, in part because accessing human gestational stage intestinal tissues to perform equivalent human studies can be difficult. Notable differences have already been described in the timing of key stages in intestinal development between rodents and humans, but the conservation of intestinal maturation events between the two species is poorly understood. We hypothesized that species-related differences in intestinal development would alter the timing of key maturation events between human and mouse. We tested our hypothesis by performing a detailed comparison of hallmarks of intestinal maturation in human and mouse gestational intestine, including markers that describe the emergence of intestinal cell types, functionality and structural integrity. Our study demonstrates clear timing differences between maturation stages in mouse and human, with the majority of human maturation hallmarks acquired post-partum, in contrast to their gestational emergence in mouse. Our work suggests caution when translating murine intestinal maturation observations to the human, and provides a maturation road map that will be helpful to those seeking to produce mature intestine from in vitro stem cell sources. Competing Interest Statement The authors have declared no competing interest.

Objective To determine outcomes at age 3 years in babies born before 27 completed weeks’ gestation in 2006, and to evaluate changes in outcome since 1995 for babies born between 22 and 25 weeks’ gestation.Design Prospective national cohort studies, EPICure and EPICure 2.Setting Hospital and home based evaluations, England.Participants 1031 surviving babies born in 2006 before 27 completed weeks’ gestation. Outcomes for 584 babies born at 22-25 weeks’ gestation were compared with those of 260 surviving babies of the same gestational age born in 1995.Main outcome measures Survival to age 3 years, impairment (2008 consensus definitions), and developmental scores. Multiple imputation was used to account for the high proportion of missing data in the 2006 cohort.Results Of the 576 babies evaluated after birth in 2006, 13.4% (n=77) were categorised as having severe impairment and 11.8% (n=68) moderate impairment. The prevalence of neurodevelopmental impairment was significantly associated with length of gestation, with greater impairment as gestational age decreased: 45% at 22-23 weeks, 30% at 24 weeks, 25% at 25 weeks, and 20% at 26 weeks (P<0.001). Cerebral palsy was present in 83 (14%) survivors. Mean developmental quotients were lower than those of the general population (normal values 100 (SD 15)) and showed a direct relation with gestational age: 80 (SD 21) at 22-23 weeks, 87 (19) at 24 weeks, 88 (19) at 25 weeks, and 91 (18) at 26 weeks. These results did not differ significantly after imputation. Comparing imputed outcomes between the 2006 and 1995 cohorts, the proportion of survivors born between 22 and 25 weeks’ gestation with severe disability, using 1995 definitions, was 18% (95% confidence interval 14% to 24%) in 1995 and 19% (14% to 23%) in 2006. Fewer survivors had shunted hydrocephalus or seizures. Survival of babies admitted for neonatal care increased from 39% (35% to 43%) in 1995 to 52% (49% to 55%) in 2006, an increase of 13% (8% to 18%), and survival without disability increased from 23% (20% to 26%) in 1995 to 34% (31% to 37%) in 2006, an increase of 11% (6% to 16%). Conclusion Survival and impairment in early childhood are both closely related to gestational age for babies born at less than 27 weeks’ gestation. Using multiple imputation to account for the high proportion of missing values, a higher proportion of babies admitted for neonatal care now survive without disability, particularly those born at gestational ages 24 and 25 weeks.

Shigella sonnei causes shigellosis, a severe gastrointestinal illness that is sexually transmissible among men who have sex with men (MSM). Multidrug resistance in S. sonnei is common including against World Health Organisation recommended treatment options, azithromycin, and ciprofloxacin. Recently, an MSM-associated outbreak of extended-spectrum β-lactamase producing, extensively drug resistant S. sonnei was reported in the United Kingdom. Here, we aimed to identify the genetic basis, evolutionary history, and international dissemination of the outbreak strain. Our genomic epidemiological analyses of 3,304 isolates from the United Kingdom, Australia, Belgium, France, and the United States of America revealed an internationally connected outbreak with a most recent common ancestor in 2018 carrying a low-fitness cost resistance plasmid, previously observed in travel associated sublineages of S. flexneri . Our results highlight the persistent threat of horizontally transmitted antimicrobial resistance and the value of continuing to work towards early and open international sharing of genomic surveillance data. An increase in shigellosis cases among men who have sex with men in the United Kingdom has been linked to an extensively drug-resistant strain of Shigella sonnei . In this genomic epidemiology study, the authors investigate the genetic basis, evolutionary history, and international dissemination of the outbreak strain.

Key Points The field of viral-vector vaccines has expanded rapidly in recent years, following a much greater understanding of viral biology and the immune system. A wide range of vectors are now in advanced preclinical and clinical development for multiple human and veterinary applications, with targets ranging from certain types of cancer to a vast array of infectious diseases. Vaccine vector development is now focusing on methods of rational attenuation and modification to enhance safety, immunogenicity and vaccine yield. A greater understanding of viral biology and immune evasion strategies, innate signalling pathways, antigen presentation and T cell and B cell biology is driving this process. Pre-existing immunity in the human population to common viruses is driving the development of new or modified vectors for clinical use in humans, such as adenoviruses of rare human or simian serotypes. These vectors are being combined in varied heterologous prime–boost protocols to maximize cellular and humoral immunogenicity against target antigens for many difficult diseases. The most successful applications of viral-vector vaccines have been in the veterinary field, with at least 12 viral-vector vaccines currently licensed for veterinary use and many more under development. Researchers in the fields of veterinary and human vaccine development are now working together to develop vaccines for closely related pathogens of animals and humans, such as tuberculosis and influenza. Highly immunogenic vaccine candidates, mainly based on adenovirus and poxvirus vectors, are now in Phase I and Phase II clinical trials for malaria, tuberculosis and influenza. Similar approaches are being adopted in the field of HIV and cancer vaccines. The development of such vaccines for use in humans faces substantial challenges, in both the scientific and the regulatory arenas. However, the licensure of replication-deficient viral-vector vaccines is wholly feasible, and the first chimeric flavivirus vaccine against Japanese encephalitis virus is currently pending regulatory approval. Recombinant viruses can act as vaccine vectors by mediating the delivery of antigens from other infectious agents to a host. In this Review, Draper and Heeney describe how a better understanding of the relationship between viruses and the immune system has benefited the use of such viral vectors in a range of human and veterinary applications. Recent developments in the use of viruses as vaccine vectors have been facilitated by a better understanding of viral biology. Advances occur as we gain greater insight into the interrelationship of viruses and the immune system. Viral-vector vaccines remain the best means to induce cellular immunity and are now showing promise for the induction of strong humoral responses. The potential benefits for global health that are offered by this field reflect the scope and utility of viruses as vaccine vectors for human and veterinary applications, with targets ranging from certain types of cancer to a vast array of infectious diseases.