Suppression of Erk signalling promotes ground state pluripotency in the mouse embryo

Embryonic stem (ES) cells can be derived and propagated from multiple strains of mouse and rat through application of small-molecule inhibitors of the fibroblast growth factor (FGF)/Erk pathway and of glycogen synthase kinase 3. These conditions shield pluripotent cells from differentiation-inducing stimuli. We investigate the effect of these inhibitors on the development of pluripotent epiblast in intact pre-implantation embryos. We find that blockade of Erk signalling from the 8-cell stage does not impede blastocyst formation but suppresses development of the hypoblast. The size of the inner cell mass (ICM) compartment is not reduced, however. Throughout the ICM, the epiblast-specific marker Nanog is expressed, and in XX embryos epigenetic silencing of the paternal X chromosome is erased. Epiblast identity and pluripotency were confirmed by contribution to chimaeras with germline transmission. These observations indicate that segregation of hypoblast from the bipotent ICM is dependent on FGF/Erk signalling and that in the absence of this signal, the entire ICM can acquire pluripotency. Furthermore, the epiblast does not require paracrine support from the hypoblast. Thus, naïve epiblast and ES cells are in a similar ground state, with an autonomous capacity for survival and replication, and high vulnerability to Erk signalling. We probed directly the relationship between naïve epiblast and ES cells. Dissociated ICM cells from freshly harvested late blastocysts gave rise to up to 12 ES cell clones per embryo when plated in the presence of inhibitors. We propose that ES cells are not a tissue culture creation, but are essentially identical to pre-implantation epiblast cells.

Tracking the embryonic stem cell transition from ground state pluripotency

Mouse embryonic stem (ES) cells are locked into self-renewal by shielding from inductive cues. Release from this ground state in minimal conditions offers a system for delineating developmental progression from naïve pluripotency. Here, we examine the initial transition process. The ES cell population behaves asynchronously. We therefore exploited a short-half-life Rex1::GFP reporter to isolate cells either side of exit from naïve status. Extinction of ES cell identity in single cells is acute. It occurs only after near-complete elimination of naïve pluripotency factors, but precedes appearance of lineage specification markers. Cells newly departed from the ES cell state display features of early post-implantation epiblast and are distinct from primed epiblast. They also exhibit a genome-wide increase in DNA methylation, intermediate between early and late epiblast. These findings are consistent with the proposition that naïve cells transition to a distinct formative phase of pluripotency preparatory to lineage priming.

Human hypoblast formation is not dependent on FGF signalling

Mouse embryos segregate three different lineages during preimplantation development: trophoblast, epiblast and hypoblast. These differentiation processes are associated with restricted expression of key transcription factors (Cdx2, Oct4, Nanog and Gata6). The mechanisms of segregation have been extensively studied in the mouse, but are not as well characterised in other species. In the human embryo, hypoblast differentiation has not previously been characterised. Here we demonstrate co-exclusive immunolocalisation of Nanog and Gata4 in human blastocysts, implying segregation of epiblast and hypoblast, as in rodent embryos. However, the formation of hypoblast in the human is apparently not dependent upon FGF signalling, in contrast to rodent embryos. Nonetheless, the persistence of Nanog-positive cells in embryos following treatment with FGF inhibitors is suggestive of a transient naïve pluripotent population in the human blastocyst, which may be similar to rodent epiblast and ES cells but is not sustained during conventional human ES cell derivation protocols.

Diverse human VH antibody fragments with bio-therapeutic properties from the Crescendo Mouse

We describe the 'Crescendo Mouse', a human V_H transgenic platform combining an engineered heavy chain locus with diverse human heavy chain V, D and J genes, a modified mouse Cγ1 gene and complete 3' regulatory region, in a triple knock-out (TKO) mouse background devoid of endogenous immunoglobulin expression. The addition of the engineered heavy chain locus to the TKO mouse restored B cell development, giving rise to functional B cells that responded to immunization with a diverse response that comprised entirely 'heavy chain only' antibodies. Heavy chain variable (V_H) domain libraries were rapidly mined using phage display technology, yielding diverse high-affinity human V_H that had undergone somatic hypermutation, lacked aggregation and showed enhanced expression in E. coli. The Crescendo Mouse produces human V_H fragments, or Humabody® V_H, with excellent bio-therapeutic potential, as exemplified here by the generation of antagonistic Humabody® V_H specific for human IL17A and IL17RA.

The prevalence of oropharyngeal squamous cell carcinoma in patients admitted with symptoms of peritonsillar abscess or cellulitis: A retrospective multicentre study

OBJECTIVES

Anecdotal evidence suggests that oropharyngeal squamous cell carcinoma (OPSCC) should be suspected in patients presenting with symptoms of peritonsillar abscess (PTA) or cellulitis (PTC). The aim of this study was to estimate the prevalence of OPSCC in patients presenting with symptoms of PTA/PTC.

METHOD, SETTING AND PARTICIPANTS

We retrospectively identified all adults with a coded diagnosis of PTA or PTC who presented between 2012 and 2016 inclusive, across six ENT units in Merseyside. Records were compared to that of the centralised regional head and neck cancer database. The clinical records of a subset of patients were reviewed for the purposes of data validation.

RESULTS

A total of 1975 patients with PTA/PTC were identified. Three patients were subsequently diagnosed with OPSCC. None of the three actually had an objective underlying diagnosis of PTA/PTC on the same side. The prevalence of OPSCC in patients admitted with symptoms of PTA/PTC was 0.15% or approximately 1:650 admissions. The records of 510 patients who presented over a one-year period (2016) were reviewed in even greater detail. There were 298 patients with PTA (59.4%) and 151 with PTC (29.1%) and 61 had an alternative diagnosis (11.9%). High-risk features (age ≥40, tonsillar asymmetry or tonsillar lesion) were present in 106 patients (24%). Urgent follow-up was expedited for 77 patients (73%).

CONCLUSION

This study estimates the risk of OPSCC in patients with peritonsillar symptoms. The prevalence is low, even in a region with a relatively heavy disease burden. Clinicians should, however, retain a high level of suspicion in patients with persistent symptoms.