Project description:Glycogen Synthase Kinase-3 (GSK-3) is a constitutively active, ubiquitously expressed protein kinase that regulates multiple signaling pathways. Over 100 putative GSK-3 substrates have been reported in diverse cell types based on in vitro kinase assays or genetic and pharmacological manipulation of GSK-3. Many more have been predicted based on a recurrent GSK-3 consensus motif, but this prediction has not been tested by analyzing the GSK-3 phosphoproteome. We used stable isotope labeling of amino acids in culture (SILAC) and mass spectrometry to analyze the repertoire of GSK-3 dependent substrates in mouse embryonic stem cells (ESCs). A comparison of wild-type and Gsk3a;Gsk3b knockout (DKO) ESCs revealed prominent GSK-3-dependent phosphorylation of multiple splicing factors and regulators of RNA biosynthesis, as well as proteins that regulate transcription, translation, and cell division. We demonstrate direct, GSK-3-dependent phosphorylation of the splicing factors RBM8A and PSF as well as the nucleolar protein NPM1. RNA sequencing to compare the transcriptomes of wild-type and Gsk3 DKO ESCs identified more than 210 genes that are alternatively spliced in a GSK-3-dependent manner, supporting a broad role for GSK-3 in regulating alternative splicing. Overall, this study provides the first unbiased analysis of the GSK-3 phosphoproteome and strong evidence for GSK-3 as a regulator of alternative splicing.
Project description:Glycogen synthase kinase-3β (GSK-3β) has been recently identified as an important regulator of stem cell function. In vitro studies show that GSK-3β inhibition delays proliferation of human haematopoietic progenitor cells while increasing numbers of late dividing multipotent progenitors. Gene expression analysis revealed that GSK-3β inhibition modulates the expression of a subset of genes that are transcriptional targets for cytokines. GSK-3β inhibition antagonised down-regulation of genes encoding cyclin dependent kinase inhibitor p57 and a member of the growth arrest and DNA damage 45 family, GADD45B as well as up-regulation of cyclin D1 by cytokines, providing a possible mechanism for the BIO-induced delay in cell cycle progression. Surprisingly, inhibition of GSK-3β earlier shown to prevent β-catenin degradation and promote the nuclear accumulation of β-catenin was not sufficient to activate its transcriptional targets in haematopoietic stem cells. GSK-3β inhibition up-regulated the expression of a several positive regulators of stem cell function suppressed during cytokine-induced proliferation. The data supports a clinical role for GSK-3β inhibition to improve engraftment efficiency of ex vivo expanded stem cells. Total RNA was isolated from three groups following expansion of CD34+ cells in cytokikes and then treatment with BIO, as described below.
Project description:APC is a classical tumor suppressor in humans, and truncating mutations are early somatic events in most cases of sporadic colon cancer. APC directly enhances the activity of glycogen synthase kinase 3 (GSK-3) and therefore loss of full length APC reduces GSK-3 activity, leading to stabilization of b-catenin protein and activation of downstream Wnt/b-catenin signaling. GSK-3 also phosphorylates multiple core mRNA splicing factors and loss of Gsk3a/b in mouse ES cells and human lymphocytes alters mRNA splicing at a genome wide level. We therefore predict that loss of APC should similarly alter splicing by reducing GSK-3 activity. Here we use RNA-seq to assess differential gene expression and altered splicing in apc-mcr mutant zebrafish embryos at 48hpf. We find robust activation of known Wnt/b-catenin target genes, as expected. Surprisingly, we also find markedly increased expression of multiple genes related to inflammation and cytokine signaling. We also identify 340 mRNA splicing variations in apc mutant zebrafish. Many of these local splice variants (LSVs) occur in mRNAs the regulate cell adhesion, migration, and morphogenesis.
Project description:From Stertz et al 2021 "Human-induced pluripotent stem cells (hiPSCs) allow for the establishment of brain cellular models of psychiatric disorders that account for a patient’s genetic background. Here, we conducted an RNA-sequencing profiling study of hiPSC-derived cell lines from schizophrenia (SCZ) subjects, most of which are from a multiplex family, from the population isolate of the Central Valley of Costa Rica. hiPSCs, neural precursor cells, and cortical neurons derived from six healthy controls and seven SCZ subjects were generated using standard methodology. Transcriptome from these cells was obtained using Illumina HiSeq 2500, and differential expression analyses were performed using DESeq2 (|fold change|>1.5 and false discovery rate < 0.3), in patients compared to controls. We identified 454 differentially expressed genes in hiPSC-derived neurons, enriched in pathways including phosphoinositide 3-kinase/glycogen synthase kinase 3 (PI3K/GSK3) signaling, with serum-glucocorticoid kinase 1 (SGK1), an inhibitor of glycogen synthase kinase 3β, as part of this pathway. We further found that pharmacological inhibition of downstream effectors of the PI3K/GSK3 pathway, SGK1 and GSK3, induced alterations in levels of neurite markers βIII tubulin and fibroblast growth factor 12, with differential effects in patients compared to controls. While demonstrating the utility of hiPSCs derived from multiplex families to identify significant cell-specific gene network alterations in SCZ, these studies support a role for disruption of PI3K/GSK3 signaling as a risk factor for SCZ." This dataset includes Samples from the manuscript "Convergent genomic and pharmacological evidence of PI3K/GSK3 signaling alterations in neurons from schizophrenia patients" by Stertz et al 2021 published in Neuropsychopharmacology.
Project description:Gene expression data from AML cell lines, MOLM-14, U937, THP-1 and HL-60, that were infected with a scrambled control hairpin (shControl), two shRNAs directed against GSK-3B (shGSK3B_1 and shGSK3B_2), or two shRNAs directed against GSK-3A (shGSK3A_5 and shGSK3A_6). Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults. Long-term survival of patients with AML has changed little over the past decade, necessitating the identification and validation of new AML targets. Integration of genomic approaches with small-molecule and genetic-based high-throughput screening holds the promise of improved discovery of candidate targets for cancer therapy. Here, we identified a role for glycogen synthase kinase 3A (GSK-3A) in AML by performing two independent small-molecule library screens and an shRNA screen for perturbations that induced a differentiation expression signature in AML cells. GSK-3 is a serine-threonine kinase involved in diverse cellular processes including differentiation, signal transduction, cell cycle regulation, and proliferation. We demonstrated that specific loss of GSK-3A induced differentiation in AML by multiple measurements, including induction of gene expression signatures, morphological changes, and cell surface markers consistent with myeloid maturation. GSK-3AM-bM-^@M-^Sspecific suppression also led to impaired growth and proliferation in vitro, induction of apoptosis, loss of colony formation in methylcellulose, and anti-AML activity in vivo. Although the role of GSK-3B has been well studied in cancer development, these studies support a role for GSK-3A in AML. The AML cell lines, MOLM-14, U937, THP-1 and HL-60, were infected with a scrambled control hairpin (shControl), two shRNAs directed against GSK-3B (shGSK3B_1 and shGSK3B_2), and two shRNAs directed against GSK-3A (shGSK3A_5 and shGSK3A_6).
Project description:Glycogen synthase kinase-3β (GSK-3β) has been recently identified as an important regulator of stem cell function. In vitro studies show that GSK-3β inhibition delays proliferation of human haematopoietic progenitor cells while increasing numbers of late dividing multipotent progenitors. Gene expression analysis revealed that GSK-3β inhibition modulates the expression of a subset of genes that are transcriptional targets for cytokines. GSK-3β inhibition antagonised down-regulation of genes encoding cyclin dependent kinase inhibitor p57 and a member of the growth arrest and DNA damage 45 family, GADD45B as well as up-regulation of cyclin D1 by cytokines, providing a possible mechanism for the BIO-induced delay in cell cycle progression. Surprisingly, inhibition of GSK-3β earlier shown to prevent β-catenin degradation and promote the nuclear accumulation of β-catenin was not sufficient to activate its transcriptional targets in haematopoietic stem cells. GSK-3β inhibition up-regulated the expression of a several positive regulators of stem cell function suppressed during cytokine-induced proliferation. The data supports a clinical role for GSK-3β inhibition to improve engraftment efficiency of ex vivo expanded stem cells.
Project description:Skeletal muscle mass is an important determinant of whole-body glucose disposal. We here show that mice (M-PDK1KO mice) with skeletal muscle–specific deficiency of 3'-phosphoinositide–dependent kinase 1 (PDK1), a key component of the phosphatidylinositol 3-kinase (PI3K) signaling pathway, manifest a reduced skeletal muscle mass under the static condition as well as impairment of exercise load–induced muscle hypertrophy. Whereas exercise load-induced changes in gene expression were not affected, the phosphorylation of ribosomal protein S6 kinase (S6K) and S6 induced by exercise load was attenuated in skeletal muscle of M-PDK1KO mice, suggesting that PDK1 regulates muscle hypertrophy not through changes in gene expression but through stimulation of protein synthesis via the S6K-S6 axis.
Project description:Modulating signaling pathways including Wnt and Hippo can induce cardiomyocyte proliferation in vivo. Applying these signaling modulators to human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in vitro can expand CMs only to modest extent (< 5-fold). Here, we demonstrate massive expansion of hiPSC-CMs in vitro (i.e. 100-250-fold) by glycogen synthase kinase-3β (GSK-3β) inhibition using CHIR99021 and concurrent removal of cell-cell contact. We show GSK-3β inhibition suppresses CM maturation while contact removal prevents CMs from cell cycle exit. Remarkably, contact removal enabled 10-to-25-times greater expansion beyond GSK-3β inhibition alone. Mechanistically, cell cycle re-activation required both LEF/TCF activity and AKT phosphorylation, but it was independent from Yes associated protein (YAP) activity. Engineered heart tissues from expanded hiPSC-CMs showed the comparable contractility to those from unexpanded hiPSC-CMs, demonstrating uncompromised cellular functionality after expansion. In sum, we uncovered a molecular interplay that enables massive expansion hiPSC-CMs for large-scale drug screening and tissue engineering.