Complex haploinsufficiency in pluripotent cells yields somatic cells with DNA methylation abnormalities and pluripotency induction defects.

A complete knockout of a single key pluripotency gene may drastically affect embryonic stem cell function and epigenetic reprogramming. In contrast, elimination of only one allele of a single pluripotency gene is mostly considered harmless to the cell. To understand whether complex haploinsufficiency exists in pluripotent cells, we simultaneously eliminated a single allele in different combinations of two pluripotency genes (i.e., Nanog+/-;Sall4+/-, Nanog+/-;Utf1+/-, Nanog+/-;Esrrb+/- and Sox2+/-;Sall4+/-). Although these double heterozygous mutant lines similarly contribute to chimeras, fibroblasts derived from these systems show a significant decrease in their ability to induce pluripotency. Tracing the stochastic expression of Sall4 and Nanog at early phases of reprogramming could not explain the seen delay or blockage. Further exploration identifies abnormal methylation around pluripotent and developmental genes in the double heterozygous mutant fibroblasts, which could be rescued by hypomethylating agent or high OSKM levels. This study emphasizes the importance of maintaining two intact alleles for pluripotency induction.

A multicenter real-world evidence study in the Swiss treatment landscape of chronic myeloid leukemia.

BACKGROUND: The real-world experience of Swiss chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors (TKIs) is largely unknown, in particular with regard to achievement of response per European Leukemia Net (ELN) criteria and adherence to ELN recommendations. METHODS: This was a retrospective, non-interventional, multicenter chart review of patients with newly diagnosed CML who had received first-line TKI and were solely treated with TKIs between 2010 and 2015, with a minimum follow-up of 18 months, at six Swiss hospitals. Effectiveness was evaluated according to ELN 2013 milestone achievements at 3, 6, 12 and 18 months, and at last follow-up. RESULTS: Data from 63 patients (56% men; median age at diagnosis 55 years) were collected (first-line imatinib [n = 27], nilotinib [n = 27], dasatinib [n = 8], or ponatinib [n = 1]). TKI switches (49 times) and dosing changes (165 times) due to intolerance or insufficient response were frequent. Compared with patients receiving first-line imatinib, a higher proportion of patients receiving first-line nilotinib or dasatinib achieved optimal response at all timepoints, irrespective of subsequent TKI therapy, and a higher proportion of patients treated with first-line nilotinib and dasatinib reached deep molecular response (BCR-ABL1IS ≤ 0.01%) at 18 months (42 and 38%, respectively, versus 27%). Patients who received nilotinib or dasatinib switched therapies less frequently than patients treated with imatinib, irrespective of subsequent TKI therapy. CONCLUSIONS: Although patient numbers were small, this real-world evidence study with patients with CML confirms that ELN guidelines are generally implemented in Swiss clinical practice, with a large proportion of patients achieving ELN 2013 milestones. While TKI use involved all inhibitors approved at the time of the study, an unexpectedly high number of TKI therapy switches suggests a clear difference in TKI use between registration trials and clinical practice.

Quantification of adipocyte numbers following adipose tissue remodeling.

To analyze the capacity of white and brown adipose tissue remodeling, we developed two mouse lines to label, quantitatively trace, and ablate white, brown, and brite/beige adipocytes at different ambient temperatures. We show here that the brown adipocytes are recruited first and reach a peak after 1 week of cold stimulation followed by a decline during prolonged cold exposure. On the contrary, brite/beige cell numbers plateau after 3 weeks of cold exposure. At thermoneutrality, brown adipose tissue, in spite of being masked by a white-like morphology, retains its brown-like physiology, as Ucp1+ cells can be recovered immediately upon beta3-adrenergic stimulation. We further demonstrate that the recruitment of Ucp1+ cells in response to cold is driven by existing adipocytes. In contrast, the regeneration of the interscapular brown adipose tissue following ablation of Ucp1+ cells is driven by de novo differentiation.

A Genetic Model to Study the Contribution of Brown and Brite Adipocytes to Metabolism.

UCP1-dependent thermogenesis is studied to define new strategies to ameliorate obesity and type 2 diabetes; however, animal models are mostly limited to germline mutations of UCP1, which can effect adaptive changes in UCP1-independent pathways. We develop an inducible mouse model for the sequential ablation of UCP1+ brown and brite/beige adipocytes in adult mice. We demonstrate that activated brown adipocytes can increase systemic energy expenditure (EE) by 30%, while the contribution of brite/beige UCP1+ cells is <5%. Notably, UCP1+ adipocytes do not contribute to circulating FGF21 levels, either at room temperature or after cold exposure. We demonstrate that the FGF21-mediated effects on EE and glucose homeostasis are partially dependent on the presence of UCP1+ cells, while the effect on weight loss is not. In conclusion, acute UCP1+ cell deletion may be a useful model to study the impact of brown and brite/beige adipocytes on metabolism.

Proliferation of nutrition sensing preadipocytes upon short term HFD feeding.

Adipose tissue is highly dynamic and increases its size dependent on the status of nutrition. Generally, an increase of adipose tissue mass is attributed to two mechanisms, namely hypertrophy (increase in adipocyte size) and hyperplasia (increase in adipocyte number). Here, we analyzed the proliferation capacity of a pool of nutrition sensing preadipocytes after short-term high fat diet (HFD) feeding. We show that this process is age independent and that adipocyte hyperplasia seems not to be dependent on adipocyte hypertrophy. Further, we could show that the subsequent development into adipocytes is influenced by the duration of HFD feeding after proliferation. Our data also demonstrate that the studied pool of preadipocytes seems to be finite and cannot be reactivated by multiple bouts of HFD feeding. In conclusion, our results indicate an important link between stem cells, nutrition status and homeostasis in the epididymal adipose tissue.

A high-throughput, image-based screen to identify kinases involved in brown adipocyte development.

Brown adipose tissue (BAT) is responsible for thermogenesis that is not associated with shivering through the process of converting chemical energy into heat through uncoupling protein 1 (UCP1) in the mitochondria. Thus, expanding or activating BAT could be a potential tool against obesity. To analyze the effect of kinase signaling on brown adipocyte formation, a process that describes the acquisition of the ability to dissipate energy as heat, we performed lentiviral-mediated short hairpin knockdown or used pharmacological inhibitors in a high-content and high-throughput in vitro image-based screen. We identified 190 kinases that either stimulated or inhibited brown adipocyte proliferation, differentiation, or formation. Among these kinases, we found that 5' AMP-activated protein kinase (AMPK) promoted the formation of brown adipocytes abundant inUCP1. Together, our results provide insight into the kinases, particularly AMPK, that regulate brown adipocyte formation.

The developmental potential of iPSCs is greatly influenced by reprogramming factor selection.

Induced pluripotent stem cells (iPSCs) are commonly generated by transduction of Oct4, Sox2, Klf4, and Myc (OSKM) into cells. Although iPSCs are pluripotent, they frequently exhibit high variation in terms of quality, as measured in mice by chimera contribution and tetraploid complementation. Reliably high-quality iPSCs will be needed for future therapeutic applications. Here, we show that one major determinant of iPSC quality is the combination of reprogramming factors used. Based on tetraploid complementation, we found that ectopic expression of Sall4, Nanog, Esrrb, and Lin28 (SNEL) in mouse embryonic fibroblasts (MEFs) generated high-quality iPSCs more efficiently than other combinations of factors including OSKM. Although differentially methylated regions, transcript number of master regulators, establishment of specific superenhancers, and global aneuploidy were comparable between high- and low-quality lines, aberrant gene expression, trisomy of chromosome 8, and abnormal H2A.X deposition were distinguishing features that could potentially also be applicable to human.