Project description:Cancers of the gastrointestinal tract including esophageal adenocarcinomas, colorectal cancers, and cancers of the gastric cardia are common comorbidities of obesity. Excessive delivery of macronutrients to the cells lining the gut can increase one’s risk for these cancer by inducing imbalances in the rate of intestinal stem cell proliferation vs. differentiation, which can produce polyps and other aberrant growths. We demonstrate that serine palmitoyltransferase (SPT), which diverts dietary fatty and amino acids into the sphingolipid biosynthesis pathway, is a critical modulator of intestinal stem cell homeostasis. SPT and other enzymes in the biosynthetic pathway are upregulated in human colon tumors. These enzymes produce sphingolipids that serve as pro-stemness signals that stimulate peroxisome-proliferator activated receptor alpha (PPARa)-mediated induction of fatty acid binding protein-1. This increases fatty acid uptake and oxidation and enhances the stemness program. Serine palmitoyltransferase thus serves as a critical link between dietary macronutrients, epithelial regeneration, and cancer risk.
Project description:Cancers of the gastrointestinal tract including esophageal adenocarcinomas, colorectal cancers, and cancers of the gastric cardia are common comorbidities of obesity. Excessive delivery of macronutrients to the cells lining the gut can increase one’s risk for these cancer by inducing imbalances in the rate of intestinal stem cell proliferation vs. differentiation, which can produce polyps and other aberrant growths. We demonstrate that serine palmitoyltransferase (SPT), which diverts dietary fatty and amino acids into the sphingolipid biosynthesis pathway, is a critical modulator of intestinal stem cell homeostasis. SPT and other enzymes in the biosynthetic pathway are upregulated in human colon tumors. These enzymes produce sphingolipids that serve as pro-stemness signals that stimulate peroxisome-proliferator activated receptor alpha (PPARa)-mediated induction of fatty acid binding protein-1. This increases fatty acid uptake and oxidation and enhances the stemness program. Serine palmitoyltransferase thus serves as a critical link between dietary macronutrients, epithelial regeneration, and cancer risk.
Project description:ALFA pulldowns of the Lcb1 subunit of the yeast serine palmitoyltransferase. Wt Lcb1 is compared to a mutant lacking the trans membrane helix 1 of Lcb1 and to control pulldowns lackingthe ALFA tag on Lcb1.
Project description:Little is known about how pro-obesity diets regulate tissue stem and progenitor cell function. Here we find that high fat diet (HFD)-induced obesity augments the numbers and function of Lgr5+ intestinal stem cells (ISCs) of the mammalian intestine. Like HFD, ex vivo treatment of intestinal organoid cultures with palmitic acid (PA), a constituent of the HFD, enhances the self-renewal potential of these organoid bodies. Mechanistically, HFD induces a robust peroxisome proliferator-activated receptor delta (PPAR-delta signature in intestinal stem and progenitor cells and pharmacologic activation of PPAR-delta recapitulates the effects that HFD has on these cells. Interestingly, HFD- and agonist-activated PPAR-delta signaling endows organoid-initiating capacity to non-stem cells and enforced PPAR-delta signaling permits these non-stem cells to form in vivo tumors upon loss of the tumor suppressor Apc. These findings highlight how diet-modulated PPAR-delta activation alters not only the function of intestinal stem and progenitor cells but also their capacity to initiate tumors. mRNA profiles of intestinal stem cells (GFP-Hi) and progenitors (GFP-Low) from WT or HFD fed mice were generated by deep sequencing using HiSeq 2000.
Project description:Little is known about how pro-obesity diets regulate tissue stem and progenitor cell function. Here we show that high-fat diet (HFD)-induced obesity augments the numbers and function of Lgr5(+) intestinal stem cells of the mammalian intestine. Mechanistically, a HFD induces a robust peroxisome proliferator-activated receptor delta (PPAR-?) signature in intestinal stem cells and progenitor cells (non-intestinal stem cells), and pharmacological activation of PPAR-? recapitulates the effects of a HFD on these cells. Like a HFD, ex vivo treatment of intestinal organoid cultures with fatty acid constituents of the HFD enhances the self-renewal potential of these organoid bodies in a PPAR-?-dependent manner. Notably, HFD- and agonist-activated PPAR-? signalling endow organoid-initiating capacity to progenitors, and enforced PPAR-? signalling permits these progenitors to form in vivo tumours after loss of the tumour suppressor Apc. These findings highlight how diet-modulated PPAR-? activation alters not only the function of intestinal stem and progenitor cells, but also their capacity to initiate tumours.
Project description:The differentiation of primary human megakaryocyte-erythroid progenitors (MEP) into megakaryocytic (Mk) or erythroid (E) progenitors is critical for maintaining the blood system, yet the mechanisms that regulate this fate specification remain unclear. Here, we analyzed RNA-seq data and found that RUNX1 is a key regulator of differential gene expression in MEP fate specification. Through viral transduction of primary MEP with RUNX1, we demonstrated that overexpression of RUNX1 promotes Mk over E specification, whereas pan-RUNX inhibition promotes E fate specification over Mk. We found that although the levels of total RUNX1 do not differ between MkP and ErP, MkP have higher levels of RUNX1 phosphorylated serine residues, and that serine/threonine phosphorylation of RUNX1 dramatically increases its effectiveness. We used human erythroleukemia (HEL) cell lines with expression of HA-tagged WT RUNX1, phosphomimetic (RUNX1-4D) and non-phosphorylatable (RUNX1-4A) mutants to model their effects on MEP. Although the chromatin association was not informative, the three forms of RUNX1 caused differential expression of 2,625 genes. Approximately 40% of these differentially expressed genes (DEGs) showed an increase with both RUNX1-WT and RUNX1-4D while another 40% showed a decrease with both RUNX1-WT and RUNX1-4D. We compared these DEGs with DEGs from primary human MEP, Mk progenitors (MkP), and E progenitors (ErP), and found that the genes upregulated by WT and RUNX1-4D in HEL cells overlapped significantly with the genes upregulated in MkP vs. MEP, whereas genes downregulated by WT and RUNX1-4D in HEL cells overlapped significantly with the genes downregulated in MkP vs. MEP. These results suggest that phosphorylation of RUNX1 enhances RUNX1’s function to activate or repress transcription of target genes that are up/downregulated during MEP fate specification.