Recent evidence shows increased and decreased expression of Ezh2 in cancer, suggesting a dual role as an oncogene or tumour suppressor. To investigate the mechanism by which Ezh2-mediated H3K27 methylation leads to cancer, we generated conditional Ezh2 knock-in (Ezh2-KI) mice. Here we show that induced Ezh2 haematopoietic expression increases the number and proliferation of repopulating haematopoietic stem cells. Ezh2-KI mice develop myeloproliferative disorder, featuring excessive myeloid expansion in bone marrow and spleen, leukocytosis and splenomegaly. Competitive and serial transplantations demonstrate progressive myeloid commitment of Ezh2-KI haematopoietic stem cells. Transplanted self-renewing haematopoietic stem cells from Ezh2-KI mice induce myeloproliferative disorder, suggesting that the Ezh2 gainof-function arises in the haematopoietic stem cell pool, and not at later stages of myelopoiesis. At the molecular level, Ezh2 regulates haematopoietic stem cell-specific genes such as Evi-1 and ntrk3, aberrantly found in haematologic malignancies. These results demonstrate a stem cell-specific Ezh2 oncogenic role in myeloid disorders, and suggest possible therapeutic applications in Ezh2-related haematological malignancies. Most low GC Gram-positive bacteria possess an essential walKR two-component system (TCS) for signal transduction involved in regulating cell wall homoeostasis. Despite the well-established intracellular regulatory mechanism, the role of this TCS in extracellular signal recognition and factors that modulate the activity of this TCS remain largely unknown. Here we identify the extracellular receptor of the kinase 'WalK' (erWalK) as a key hub for bridging extracellular signal input and intracellular kinase activity modulation in Staphylococcus aureus. Characterization of the crystal structure of erWalK revealed a canonical Per-Arnt-Sim (PAS) domain for signal sensing. Single amino-acid mutation of potential signal-transduction residues resulted in severely impaired function of WalKR. A small molecule derived from structure-based virtual screening against erWalK is capable of selectively activating the walKR TCS. The molecular level characterization of erWalK will not only facilitate exploration of natural signal(s) but also provide a template for rational design of erWalK inhibitors.

A number of metabolites have signaling properties by acting through G-protein-coupled receptors. Succinate, a Krebs cycle intermediate, increases after dysregulated energy metabolism and can bind to its cognate receptor succinate receptor 1 (Sucnr1, or GPR91) to activate downstream signaling pathways. We show that Sucnr1 is highly expressed in the white adipose tissue (WAT) compartment of mice and regulates adipose mass and glucose homeostasis. Sucnr1 2/2 mice were generated, and weight gain was monitored under basal and nutritional stress (high-fat diet [HFD]) conditions. On chow diet, Sucnr1 2/2 mice had increased energy expenditure, were lean with a smaller WAT compartment, and had improved glucose buffering. Lipolysis measurements revealed that Sucnr1 2/2 mice were released from succinate-induced inhibition of lipolysis, demonstrating a function of Sucnr1 in adipose tissue. Sucnr1 deletion also protected mice from obesity on HFD, but only during the initial period; at later stages, body weight of HFD-fed Sucnr1 2/2 mice was almost comparable with wild-type (WT) mice, but WAT content was greater. Also, these mice became progressively hyperglycemic and failed to secrete insulin, although pancreas architecture was similar to WT mice. These findings suggest that Sucnr1 is a sensor for dietary energy and raise the interesting possibility that protocols to modulate Sucnr1 might have therapeutic utility in the setting of obesity.

Hutchinson-Gilford progeria syndrome (HGPS) is an extremely rare genetic disorder for which no cure exists. The disease is characterized by premature aging and inevitable death in adolescence due to cardiovascular complications. Most HGPS patients carry a heterozygous de novo LMNA c.1824C > T mutation, which provokes the expression of a dominant-negative mutant protein called progerin. Therapies proven effective in HGPS-like mouse models have yielded only modest benefit in HGPS clinical trials. To overcome the gap between HGPS mouse models and patients, we have generated by CRISPR-Cas9 gene editing the first large animal model for HGPS, a knockin heterozygous LMNA c.1824C > T Yucatan minipig. Like HGPS patients, HGPS minipigs endogenously co-express progerin and normal lamin A/C, and exhibit severe growth retardation, lipodystrophy, skin and bone alterations, cardiovascular disease, and die around puberty. Remarkably, the HGPS minipigs recapitulate critical cardiovascular alterations seen in patients, such as left ventricular diastolic dysfunction, altered cardiac electrical activity, and loss of vascular smooth muscle cells. Our analysis also revealed reduced myocardial perfusion due to microvascular damage and myocardial interstitial fibrosis, previously undescribed readouts potentially useful for monitoring disease progression in patients. The HGPS minipigs provide an appropriate preclinical model in which to test human-size interventional devices and optimize candidate therapies before advancing to clinical trials, thus accelerating the development of effective applications for HGPS patients.

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Dyskeratosis congenita is an inherited disease caused by mutations in genes coding for telomeric components. It was previously reported that expression of a dyskerin-derived peptide, GSE24.2, increases telomerase activity, regulates gene expression and decreases DNA damage and oxidative stress in dyskeratosis congenita patient cells. The biological activity of short peptides derived from GSE24.2 was tested and one of them, GSE4, that probed to be active, was further characterized in this article. Expression of this eleven amino acids long peptide increased telomerase activity and reduced DNA damage, oxidative stress and cell senescence in dyskerin-mutated cells. GSE4 expression also activated c-myc and TERT promoters and increase of c-myc, TERT and TERC expression. The level of biological activity of GSE4 was similar to that obtained by GSE24.2 expression. Incorporation of a dyskerin nuclear localization signal to GSE24.2 did not change its activity on promoter regulation and DNA damage protection. However, incorporation of a signal that increases the rate of nucleolar localization impaired GSE24.2 activity. Incorporation of the dyskerin nuclear localization signal to GSE4 did not alter its biological activity. Mutation of the Aspartic Acid residue that is conserved in the pseudouridine synthase domain present in GSE4 did not impair its activity, except for the repression of c-myc promoter activity and the decrease of c-myc, TERT and TERC gene expression in dyskerin-mutated cells. These results indicated that GSE4 could be of great therapeutic interest for treatment of dyskeratosis congenita patients.