(R)-PFI-2 is a potent and selective inhibitor of SETD7 methyltransferase activity in cells.

SET domain containing (lysine methyltransferase) 7 (SETD7) is implicated in multiple signaling and disease related pathways with a broad diversity of reported substrates. Here, we report the discovery of (R)-PFI-2-a first-in-class, potent (Ki (app) = 0.33 nM), selective, and cell-active inhibitor of the methyltransferase activity of human SETD7-and its 500-fold less active enantiomer, (S)-PFI-2. (R)-PFI-2 exhibits an unusual cofactor-dependent and substrate-competitive inhibitory mechanism by occupying the substrate peptide binding groove of SETD7, including the catalytic lysine-binding channel, and by making direct contact with the donor methyl group of the cofactor, S-adenosylmethionine. Chemoproteomics experiments using a biotinylated derivative of (R)-PFI-2 demonstrated dose-dependent competition for binding to endogenous SETD7 in MCF7 cells pretreated with (R)-PFI-2. In murine embryonic fibroblasts, (R)-PFI-2 treatment phenocopied the effects of Setd7 deficiency on Hippo pathway signaling, via modulation of the transcriptional coactivator Yes-associated protein (YAP) and regulation of YAP target genes. In confluent MCF7 cells, (R)-PFI-2 rapidly altered YAP localization, suggesting continuous and dynamic regulation of YAP by the methyltransferase activity of SETD7. These data establish (R)-PFI-2 and related compounds as a valuable tool-kit for the study of the diverse roles of SETD7 in cells and further validate protein methyltransferases as a druggable target class.

A Century-long Journey From the Discovery of Insulin to the Implantation of Stem Cell-derived Islets.

For the past century, insulin injections have saved millions of lives, but glycemic instability is still a persistent challenge for people with diabetes, leading to tremendous morbidity and premature mortality. Research in the field of islet transplantation has demonstrated that replacing insulin-producing ß cells can restore euglycemia comparable to individuals without diabetes. However, a short supply of cadaveric islet donors, the technically challenging process of isolating islets, and the requirement for chronic immune suppression have impeded widespread clinical adoption. Rather than relying on cadaveric cells, pluripotent stem cells could serve as a virtually unlimited supply of insulin-producing ß cells. Protocols have been developed that mimic the normal in vivo development of the human pancreas to generate pancreatic progenitor cells in vitro. Ongoing investigations have yielded progressively more mature ß-like cells in vitro that produce insulin but do not yet fully mimic healthy mature ß cells. Alongside development of differentiation protocols, other work has provided insight into potential implantation sites for stem cell-derived islet cells including the subcutaneous space, portal vein, and omentum. To optimize implanted cell survival and function, development of immune modulation therapies is ongoing, including selection of immunomodulatory medications and genetic modification of implanted cells to evade immune responses. Further, macroencapsulation or microencapsulation devices could be used to contain and/or immunoprotect implanted cells from the immune response including by using 3-dimensional bioprinting to facilitate the process. Remarkably, ongoing clinical trials have now yielded the first patient relying on differentiated stem cells rather than syringes as their insulin replacement therapy.

Differentiation of Human Pluripotent Stem Cells into Insulin-Producing Islet Clusters.

Differentiation of human pluripotent stem cells (hPSCs) into insulin-secreting beta cells provides material for investigating beta cell function and diabetes treatment. However, challenges remain in obtaining stem cell-derived beta cells that adequately mimic native human beta cells. Building upon previous studies, hPSC-derived islet cells have been generated to create a protocol with improved differentiation outcomes and consistency. The protocol described here utilizes a pancreatic progenitor kit during Stages 1-4, followed by a protocol modified from a paper previously published in 2014 (termed "R-protocol" hereafter) during Stages 5-7. Detailed procedures for using the pancreatic progenitor kit and 400 µm diameter microwell plates to generate pancreatic progenitor clusters, R-protocol for endocrine differentiation in a 96-well static suspension format, and in vitro characterization and functional evaluation of hPSC-derived islets, are included. The complete protocol takes 1 week for initial hPSC expansion followed by ~5 weeks to obtain insulin-producing hPSC islets. Personnel with basic stem cell culture techniques and training in biological assays can reproduce this protocol.

Human A2-CAR T cells reject HLA-A2+ human islets transplanted into mice without inducing graft versus host disease.

Background: Type 1 diabetes (T1D) is an autoimmune disease characterised by T cell mediated destruction of pancreatic beta-cells. Islet transplantation is an effective therapy, but its success is limited by islet quality and availability along with the need for immunosuppression. New approaches include use of stem cell-derived insulin-producing cells and immunomodulatory therapies, but a limitation is the paucity of reproducible animal models in which interactions between human immune cells and insulin-producing cells can be studied without the complication of xenogeneic graft- versus -host disease (xGVHD). Methods: We expressed an HLA-A2-specific chimeric antigen receptor (A2-CAR) in human CD4+ and CD8+ T cells and tested their ability to reject HLA-A2+ islets transplanted under the kidney capsule or anterior chamber of the eye of immunodeficient mice. T cell engraftment, islet function and xGVHD were assessed longitudinally. Results: The speed and consistency of A2-CAR T cells-mediated islet rejection varied depending on the number of A2-CAR T cells and the absence/presence of co-injected peripheral blood mononuclear cells (PBMCs). When <3 million A2-CAR T cells were injected, co-injection of PBMCs accelerated islet rejection but also induced xGVHD. In the absence of PBMCs, injection of 3 million A2-CAR T cells caused synchronous rejection of A2+ human islets within 1 week and without xGVHD for 12 weeks. Conclusions: Injection of A2-CAR T cells can be used to study rejection of human insulin-producing cells without the complication of xGVHD. The rapidity and synchrony of rejection will facilitate in vivo screening of new therapies designed to improve the success of isletreplacement therapies.

Protocol development to further differentiate and transition stem cell-derived pancreatic progenitors from a monolayer into endocrine cells in suspension culture.

The generation of functional ß-cells from human pluripotent stem cells (hPSCs) for cell replacement therapy and disease modeling of diabetes is being investigated by many groups. We have developed a protocol to harvest and aggregate hPSC-derived pancreatic progenitors generated using a commercially available kit into near uniform spheroids and to further differentiate the cells toward an endocrine cell fate in suspension culture. Using a static suspension culture platform, we could generate a high percentage of insulin-expressing, glucose-responsive cells. We identified FGF7 as a soluble factor promoting aggregate survival with no inhibitory effect on endocrine gene expression. Notch inhibition of pancreatic progenitor cells during aggregation improved endocrine cell induction in vitro and improved graft function following implantation and further differentiation in mice. Thus we provide an approach to promote endocrine formation from kit-derived pancreatic progenitors, either through extended culture or post implant.

Human A2-CAR T Cells Reject HLA-A2 + Human Islets Transplanted Into Mice Without Inducing Graft-versus-host Disease.

BACKGROUND: Type 1 diabetes is an autoimmune disease characterized by T-cell-mediated destruction of pancreatic beta-cells. Islet transplantation is an effective therapy, but its success is limited by islet quality and availability along with the need for immunosuppression. New approaches include the use of stem cell-derived insulin-producing cells and immunomodulatory therapies, but a limitation is the paucity of reproducible animal models in which interactions between human immune cells and insulin-producing cells can be studied without the complication of xenogeneic graft-versus-host disease (xGVHD). METHODS: We expressed an HLA-A2-specific chimeric antigen receptor (A2-CAR) in human CD4 + and CD8 + T cells and tested their ability to reject HLA-A2 + islets transplanted under the kidney capsule or anterior chamber of the eye of immunodeficient mice. T-cell engraftment, islet function, and xGVHD were assessed longitudinally. RESULTS: The speed and consistency of A2-CAR T-cell-mediated islet rejection varied depending on the number of A2-CAR T cells and the absence/presence of coinjected peripheral blood mononuclear cells (PBMCs). When <3 million A2-CAR T cells were injected, coinjection of PBMCs accelerated islet rejection but also induced xGVHD. In the absence of PBMCs, injection of 3 million A2-CAR T cells caused synchronous rejection of A2 + human islets within 1 wk and without xGVHD for 12 wk. CONCLUSIONS: Injection of A2-CAR T cells can be used to study rejection of human insulin-producing cells without the complication of xGVHD. The rapidity and synchrony of rejection will facilitate in vivo screening of new therapies designed to improve the success of islet-replacement therapies.

SETD7 Controls Intestinal Regeneration and Tumorigenesis by Regulating Wnt/ß-Catenin and Hippo/YAP Signaling.

Intestinal tumorigenesis is a result of mutations in signaling pathways that control cellular proliferation, differentiation, and survival. Mutations in the Wnt/ß-catenin pathway are associated with the majority of intestinal cancers, while dysregulation of the Hippo/Yes-Associated Protein (YAP) pathway is an emerging regulator of intestinal tumorigenesis. In addition, these closely related pathways play a central role during intestinal regeneration. We have previously shown that methylation of the Hippo transducer YAP by the lysine methyltransferase SETD7 controls its subcellular localization and function. We now show that SETD7 is required for Wnt-driven intestinal tumorigenesis and regeneration. Mechanistically, SETD7 is part of a complex containing YAP, AXIN1, and ß-catenin, and SETD7-dependent methylation of YAP facilitates Wnt-induced nuclear accumulation of ß-catenin. Collectively, these results define a methyltransferase-dependent regulatory mechanism that links the Wnt/ß-catenin and Hippo/YAP pathways during intestinal regeneration and tumorigenesis.

Methyltransferase G9A regulates T cell differentiation during murine intestinal inflammation.

Inflammatory bowel disease (IBD) pathogenesis is associated with dysregulated CD4⁺ Th cell responses, with intestinal homeostasis depending on the balance between IL-17-producing Th17 and Foxp3⁺ Tregs. Differentiation of naive T cells into Th17 and Treg subsets is associated with specific gene expression profiles; however, the contribution of epigenetic mechanisms to controlling Th17 and Treg differentiation remains unclear. Using a murine T cell transfer model of colitis, we found that T cell-intrinsic expression of the histone lysine methyltransferase G9A was required for development of pathogenic T cells and intestinal inflammation. G9A-mediated dimethylation of histone H3 lysine 9 (H3K9me2) restricted Th17 and Treg differentiation in vitro and in vivo. H3K9me2 was found at high levels in naive Th cells and was lost following Th cell activation. Loss of G9A in naive T cells was associated with increased chromatin accessibility and heightened sensitivity to TGF-ß1. Pharmacological inhibition of G9A methyltransferase activity in WT T cells promoted Th17 and Treg differentiation. Our data indicate that G9A-dependent H3K9me2 is a homeostatic epigenetic checkpoint that regulates Th17 and Treg responses by limiting chromatin accessibility and TGF-ß1 responsiveness, suggesting G9A as a therapeutic target for treating intestinal inflammation.