Transcription factor ASCL2 is required for development of the glycogen trophoblast cell lineage

The basic helix-loop-helix (bHLH) transcription factor ASCL2 plays essential roles in diploid multipotent trophoblast progenitors, intestinal stem cells, follicular T-helper cells, as well as during epidermal development and myogenesis. During early development, Ascl2 expression is regulated by genomic imprinting and only the maternally inherited allele is transcriptionally active in trophoblast. The paternal allele-specific silencing of Ascl2 requires expression of the long non-coding RNA Kcnq1ot1 in cis and the deposition of repressive histone marks. Here we show that Del^7AI, a 280-kb deletion allele neighboring Ascl2, interferes with this process in cis and leads to a partial loss of silencing at Ascl2. Genetic rescue experiments show that the low level of Ascl2 expression from the paternal Del^7AI allele can rescue the embryonic lethality associated with maternally inherited Ascl2 mutations, in a level-dependent manner. Despite their ability to support development to term, the rescued placentae have a pronounced phenotype characterized by severe hypoplasia of the junctional zone, expansion of the parietal trophoblast giant cell layer, and complete absence of invasive glycogen trophoblast cells. Transcriptome analysis of ectoplacental cones at E7.5 and differentiation assays of Ascl2 mutant trophoblast stem cells show that ASCL2 is required for the emergence or early maintenance of glycogen trophoblast cells during development. Our work identifies a new cis-acting mutation interfering with Kcnq1ot1 silencing function and establishes a novel critical developmental role for the transcription factor ASCL2.

By controlling precise networks of target genes, transcription factors play important roles in cell fate determination during development. The Ascl2 gene codes for a transcription factor essential for the maintenance of progenitor cell populations able to differentiate into specialized cell types in the intestine and in the extra-embryonic trophoblast lineage. The trophoblast is an essential component of the placenta, an organ required for development of the embryo in placental mammals. Ascl2 belongs to a group of unusual genes, called imprinted genes, which are expressed from only a single parental copy. Ascl2 is only expressed from the maternally inherited copy in the trophoblast, the paternal copy being kept silent. Here, we describe an engineered deletion neighboring Ascl2 that interferes with the complete silencing of the paternal copy of the gene. We show that the low amount of ASCL2 produced from this deletion can rescue the embryonic lethality associated with non-functional maternal copies of Ascl2. Although the rescued embryos can often survive to term, their placenta is highly disorganized and lacks members of a specific cell lineage, the trophoblast glycogen cells. By analyzing the transcriptional profile of mutant trophoblast progenitors in vivo and of differentiated trophoblast stem cells, we show that ASCL2 plays a very early role in the formation of this cell lineage.

Focus on People and the Science Will Follow: Motivating Forces for Professional Movement in Stem Cell Research

The migration of researchers across geographic borders, or "brain drain" as it is commonly called, remains an important issue for governments around the world as loss or gain of highly qualified personnel in research can have substantial social, economic and political consequences. In the present study we seek to examine the forces that drive international professional migration of stem cell (SC) researchers, for which variation of SC policy in different jurisdictions has previously been implicated as a driving force. Structured interviews were carried out with a purposive sample of SC researchers in the professoriate who had made international moves after postdoctoral work between the years 2001-2014, or were actively anticipating a future move. Participants were asked to rank motivators of international movement on a 5-point Likert scale and prompted to elaborate on their answers. The results suggest that career considerations, availability of research funding, and personal considerations are of high importance to the participants when considering an international move, while the permissiveness or restrictiveness SC research policy is of comparably lower importance. Participants also expressed that international movements are beneficial to scientific careers overall. The findings have important implications for policy and strategies to attract and retain members of the SC research community.

Innovations in Training: Toward Mitigating "Eternal post-docdum" in Stem Cell Research

The Networks of Centres of Excellence (NCE) is an innovative model of large-scale research networks that began in Canada in 1989, and has since been adopted by numerous countries around the globe. The Canadian Stem Cell Network (SCN), an NCE that has fostered stem cell research and innovation in Canada, has supported over 1800 trainees since its inception in 2001. In the present study we assess the impact of such a network on its research trainees professional decision-making and movements. A database populated by the SCN between the years 2001-2013 was utilized to describe trainee professional movement between sectors and geographic regions. Focus groups of SCN trainees (n = 27) were carried out and major themes and subthemes were derived from the discourse using a thematic analysis approach. We found that most SCN trainees remained in Canada and in academic positions after leaving the SCN. Trainees expressed a desire to work in environments where their scientific interests and ideas are nurtured, where funding is stable, and where supervisor mentorship is readily accessible. SCN trainees value the unique opportunities provided by the NCE, including opportunities to network with peers, to attend various workshops and to broaden their knowledge and interest base beyond science and academia. Challenges faced by postdoctoral fellows and recommendations for future NCEs are also discussed. The findings here can be used to form evidence-based recommendations for future research networks and for policy pertaining to the recruitment and retention of highly qualified personnel in stem cell research.

"You don't want to lose that trust that you've built with this patient...": (dis)trust, medical tourism, and the Canadian family physician-patient relationship

Background

Recent trends document growth in medical tourism, the private pursuit of medical interventions abroad. Medical tourism introduces challenges to decision-making that impact and are impacted by the physician-patient trust relationship—a relationship on which the foundation of beneficent health care lies. The objective of the study is to examine the views of Canadian family physicians about the roles that trust plays in decision-making about medical tourism, and the impact of medical tourism on the therapeutic relationship.

Methods

We conducted six focus groups with 22 family physicians in the Canadian province of British Columbia. Data were analyzed thematically using deductive and inductive codes that captured key concepts across the narratives of participants.

Results

Family physicians indicated that they trust their patients to act as the lead decision-makers about medical tourism, but are conflicted when the information they are managing contradicts the best interests of the patients. They reported that patients distrust local health care systems when they experience insufficiencies in access to care and that this can prompt patients to consider going abroad for care. Trust fractures in the physician-patient relationship can arise from shame, fear and secrecy about medical tourism.

Conclusions

Family physicians face diverse tensions about medical tourism as they must balance their roles in: (1) providing information about medical tourism within a context of information deficits; (2) supporting decision-making while distancing themselves from patients’ decisions to engage in medical tourism; and (3) acting both as agents of the patient and of the domestic health care system. These tensions highlight the ongoing need for reliable third-party informational resources about medical tourism and the development of responsive policy.

Beckwith-Wiedemann and Silver-Russell syndromes: opposite developmental imbalances in imprinted regulators of placental function and embryonic growth

Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS) are two congenital disorders with opposite outcomes on fetal growth, overgrowth and growth restriction, respectively. Although both disorders are heterogeneous, most cases of BWS and SRS are associated with opposite epigenetic or genetic abnormalities on 11p15.5 leading to opposite imbalances in the expression levels of imprinted genes. In this article, we review evidence implicating these genes in the developmental regulation of embryonic growth and placental function in mouse models. The emerging picture suggests that both SRS and BWS can be caused by the simultaneous and opposite deregulation of two groups of imprinted genes on 11p15.5. A detailed description of the phenotypic abnormalities associated with each syndrome must take into consideration the developmental functions of each gene involved.

Acute insulin signaling in pancreatic beta-cells is mediated by multiple Raf-1 dependent pathways

Insulin enhances the proliferation and survival of pancreatic beta-cells, but its mechanisms remain unclear. We hypothesized that Raf-1, a kinase upstream of both ERK and Bad, might be a critical target of insulin in beta-cells. To test this hypothesis, we treated human and mouse islets as well as MIN6 beta-cells with multiple insulin concentrations and examined putative downstream targets using immunoblotting, immunoprecipitation, quantitative fluorescent imaging, and cell death assays. Low doses of insulin rapidly activated Raf-1 by dephosphorylating serine 259 and phosphorylating serine 338 in human islets, mouse islets, and MIN6 cells. The phosphorylation of ERK by insulin was eliminated by exposure to a Raf inhibitor (GW5074) or transfection with a dominant-negative Raf-1 mutant. Insulin also enhanced the interaction between mitochondrial Raf-1 and Bcl-2 agonist of cell death (Bad), promoting Bad inactivation via its phosphorylation on serine 112. Insulin-stimulated ERK phosphorylation was abrogated by calcium chelation, calcineurin and calmodulin-dependent protein kinase II inhibitors, and Ned-19, a nicotinic acid adenine dinucleotide phosphate receptor (NAADPR) antagonist. Blocking Raf-1 and Ca(2+) signaling resulted in nonadditive beta-cell death. Autocrine insulin signaling partly accounted for the effects of glucose on ERK phosphorylation. Our results demonstrate that Raf-1 is a critical target of insulin in primary beta-cells. Activation of Raf-1 leads to both an ERK-dependent pathway that involves nicotinic acid adenine dinucleotide phosphate-sensitive Ca(2+) stores and Ca(2+)-dependent phosphorylation events, and an ERK-independent pathway that involves Bad inactivation at the mitochondria. Together our findings identify a novel insulin signaling pathway in beta-cells and shed light on insulin's antiapoptotic and mitogenic mechanisms.