Both microbes and multicellular organisms actively regulate their cell fate determination to cope with changing environments or to ensure proper development. Here, we use synthetic biology approaches to engineer bistable gene networks to demonstrate that stochastic and permanent cell fate determination can be achieved through initializing gene regulatory networks (GRNs) at the boundary between dynamic attractors. We realize this experimentally by linking a synthetic GRN to a natural output of galactose metabolism regulation in yeast. Combining mathematical modeling and flow cytometry, we show that our engineered systems are bistable and that inherent gene expression stochasticity does not induce spontaneous state transitioning at steady state. Mathematical analysis predicts that stochastic cell fate determination in this case can only be realized when gene expression fluctuation occurs on or near attractor basin boundaries (the points of instability). Guided by numerical simulations, experiments are designed and performed with quantitatively diverse gene networks to test model predictions, which are verified by both flow cytometry and singlecell microscopy. By interfacing rationally designed synthetic GRNs with background gene regulation mechanisms, this work investigates intricate properties of networks that illuminate possible regulatory mechanisms for cell differentiation and development that can be initiated from points of instability.

Background: To assess the efficacy, safety, and tolerability of bimagrumab (fully human monoclonal antibody) in participants with inclusion body myositis (IBM). Methods: This multicentre, double-blind, placebo-controlled study (RESILIENT; ClinicalTrials.gov, number NCT01925209) was conducted between September 26, 2013 and January 06, 2016 at academic clinical sites in Europe, the USA, Australia, and Japan. Eligible participants (aged 36-85 years [inclusive]; modified 2010 MRC criteria) were randomly assigned (1:1:1:1) using blocked randomisation schedule (block size=4) to receive intravenous infusions of bimagrumab 10, 3, 1 mg/kg, or placebo every 4 weeks for at least 48 weeks. All study participants, sponsor, investigators, site personnel, and those performing assessments were masked to treatment assignment. 6-minute walking distance (6MWD; primary outcome measure) was assessed at Week 52 in the primary analysis population. A multivariate normal repeated measures model was used to analyse data on 6MWD. Safety was assessed by recording adverse events (AEs), electrocardiography, echocardiography, hematology, urinalysis, and blood chemistry.

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BackgroundNicotine has negative effects on tissue repair, little research concerns its effect on the cartilage repair of tissue engineering stem cells. The present study aimed to investigate the effects of nicotine on the bone marrow-derived mesenchymal stem cells’ (BMSCs) chondrogenic repair function of cartilage defects and explored the molecular mechanism.MethodsA cartilage defect model of rat was repaired by BMSC transplantation, and treated with nicotine or saline at 2.0 mg/kg/d in 12 weeks. Nicotine’s effect on chondrogenic differentiation was studied by exposing BMSCs to nicotine at 0.1, 1, 10, and 100 μM, and methyllycaconitine (MLA), which is a selective α7-nicotinic acetylcholine receptor (nAChR) inhibitor and si-RNA of nuclear factor of activated T cells 2 (NFATc2), were used to verify the molecular mechanism of nicotine’s effect.ResultsData showed that nicotine inhibited cartilage repair function by suppressing SRY-type high-mobility group box 9 (Sox9) in regenerated tissues. Further in vitro study demonstrated that nicotine enhanced intracellular Ca2+ and activity of calcineurin (CaN) through α7-nAChR, increased the nucleic expressions of NFATc2 and the bindings to SOX9 promoter, and thus reduced the acetylation of H3K9 and H3K14 in SOX9 promoter.ConclusionsFindings from this study demonstrated that nicotine suppressed the chondrogenic differentiation of BMSCs in vivo and in vitro, which offers insight into the risk assessment of cartilage defect repair in a nicotine exposure population and its therapeutic target.Electronic supplementary materialThe online version of this article (10.1186/s13287-018-0853-x) contains supplementary material, which is available to authorized users.