Differential sensitivity to Wnt signaling gradients in human gastric organoids derived from corpus and antrum.

Wnt signaling regulates gastric stem cell proliferation and differentiation. Although similar Wnt gradients exist within the corpus and antrum of the human stomach, there are striking differences in gland architecture and disease manifestation that suggest Wnt may differentially regulate progenitor cell function in each compartment. In this study, we tested sensitivities to Wnt activation in human gastric corpus and antral organoids to determine whether progenitor cells have region-specific differences in Wnt responsiveness. Human patient-matched corpus and antral organoids were grown in the presence of varying concentrations of the Wnt pathway activator CHIR99021 to assess regional sensitivity to Wnt signaling on growth and proliferation. Corpus organoids were further studied to understand how high Wnt affected cellular differentiation and progenitor cell function. A lower concentration of CHIR99021 stimulated peak growth in corpus organoids compared with patient-matched antral organoids. Supramaximal Wnt signaling levels in corpus organoids suppressed proliferation, altered morphology, reduced surface cell differentiation, and increased differentiation of deep glandular neck and chief cells. Surprisingly, corpus organoids grown in high CHIR99021 had enhanced organoid forming potential, indicating that progenitor cell function was maintained in these nonproliferative, deep glandular cell-enriched organoids. Passaging high-Wnt quiescent organoids into low Wnt rescued normal growth, morphology, and surface cell differentiation. Our findings suggest that human corpus progenitor cells have a lower threshold for optimal Wnt signaling than antral progenitor cells. We demonstrate that Wnt signaling in the corpus regulates a bimodal axis of differentiation, with high Wnt promoting deep glandular cell differentiation and suppressing proliferation while simultaneously promoting progenitor cell function.NEW & NOTEWORTHY This study demonstrates that human gastric corpus organoids have a lower Wnt signaling threshold to drive optimal growth relative to patient-matched antral organoids. Paradoxically, supramaximal Wnt levels suppress corpus organoid proliferation, yet promote differentiation toward deep glandular cell types while simultaneously enhancing progenitor cell function. These findings provide novel insights into how Wnt signaling differentially regulates homeostasis in the human gastric corpus and antrum and contextualizes patterns of Wnt activation diseases.

Region-specific Wnt signaling responses promote gastric polyp formation in patients with familial adenomatous polyposis.

Germline adenomatous polyposis coli (APC) mutation in patients with familial adenomatous polyposis (FAP) promotes gastrointestinal polyposis, including the formation of frequent gastric fundic gland polyps (FGPs). In this study, we investigated how dysregulated Wnt signaling promotes FGPs and why they localize to the corpus region of the stomach. We developed a biobank of FGP and surrounding nonpolyp corpus biopsies and organoids from patients with FAP for comparative studies. Polyp biopsies and polyp-derived organoids exhibited enhanced Wnt target gene expression. Polyp-derived organoids with intrinsically upregulated Wnt signaling showed poor tolerance to further induction, suggesting that high Wnt restricts growth. Targeted genomic sequencing revealed that most gastric polyps did not arise via APC loss of heterozygosity. Studies in genetic mouse models demonstrated that heterozygous Apc loss increased epithelial cell proliferation in the corpus but not the antrum, while homozygous Apc loss was not maintained in the corpus yet induced hyperproliferation in the antrum. Our findings suggest that heterozygous APC mutation in patients with FAP may be sufficient to drive polyp formation in the corpus region while subsequent loss of heterozygosity to further enhance Wnt signaling is not tolerated. This finding contextualizes the abundant yet benign nature of gastric polyps in FAP patient corpus compared with the rare, yet adenomatous polyps in the antrum.

An OCO3- trianionic pincer tungsten(VI) alkylidyne: rational design of a highly active alkyne polymerization catalyst.

Synthesis, characterization, and catalytic alkyne polymerization results for the first trianionic pincer alkylidyne complex, [(t)BuOCO]W≡CC(CH(3))(3)(THF)(2) (6), are described. Complex 6 is a highly active catalyst for the polymerization of acetylenes and exhibits a high turnover number (4371), activity (1.05 × 10(6) g(PPA) mol(cat)(-1) h(-1)),and yield (87%) for the polymerization of 1-ethynyl-4-fluorobenzene.

NCN trianionic pincer ligand precursors: synthesis of bimetallic, chelating diamide, and pincer group IV complexes.

This report details the synthesis of new NCN trianionic pincer ligand precursors and metalation reactions to form group (IV) complexes. N,N'-[1,3-phenylenebis(methylene)]bis-2,6-diisopropylaniline [2,6-(i)PrNCN]H(3) (8) was converted to the N,N'-substituted Si(IV), Sn(IV), Mg(II), and Zn(II) derivatives. [2,6-(i)PrNCHN](SiMe(3))(2) (9-Si) and [2,6-(i)PrNCHN](SnMe(3))(2) (9-Sn) form by first treating 8 with MeLi followed by Me(3)MCl, where M = Si or Sn. Single crystal X-ray experiments indicate 8, 9-Si, and 9-Sn have similar structural features in the solid state. [2,6-(i)PrNCHN](mu-MgCl.THF)(2) (12) forms by treating 8 with MeMgCl, and its solid state structure revealed a bis-mu-MgCl bridging unit. The (1)H NMR spectrum of 12 reveals a dynamic process occurs in solution. A variable temperature (1)H NMR experiment failed to quench the dynamic process. {[2,6-(i)PrNCHN]Zn}(2) (13) forms upon treating {[2,6-(i)PrNCHN]Li(2)}(2) (10) with anhydrous ZnCl(2) and is a dimer in the solid state. Again, dynamic (1)H NMR behavior is observed, and a mechanism is provided to explain the apparent low symmetry of 13 in solution. Extension of the aliphatic arm of the NCN ligand provides the new N(C)C(C)N pincer ligand precursors N,N'-(2,2'-(1,3-phenylene)bis(ethane-2,1-diyl))bis(3,5-bis(trifluoromethyl)aniline) [3,5-CF(3)N(C)C(C)N]H(3) (16) and [3,5-CF(3)N(C)CH(C)N](SiMe(3))(2) (17). A more rigid ligand architecture was accessed by synthesis of the anthracene derived pincer ligand anthracene-1,8-diylbis(N-3,5-bistrifluormethylaniline) [3,5-CF(3)N(C)C(anth)(C)N]H(3) (18). Treating {Zr(NMe(2))(4)}(2) with 2 equiv of 16 provides the dimer {(mu-3,5-CF(3)N(C)CH(C)N)Zr(NMe(2))(3)NHMe(2)}(2) (19). Treating Hf(NMe(2))(4) with 18 provides the bimetallic complex (mu-3,5-CF(3)N(C)CH(anth)(C)N){Hf(NMe(2))(3)NHMe(2)}(2) (20) in which one ligand bridges two Hf(IV) ions. Salt metathesis between 10 and ZrCl(2)(NMe(2))(2)(THF)(2) provides the mononuclear complex [2,6-(i)PrNCHN]Zr(NMe(2))(2) (21) in which the NCN ligand is bound as a chelating diamide. Thermoysis of 21 does not lead to formation of a trianionic pincer complex. Instead, treating HfCl(4) with {[2,6-(i)PrNCN]Li(3)}(2) (11) followed by MeLi provides the trianionic pincerate complex [2,6-(i)PrNCNHfMe(2)][Li(DME)(2)] (23). In the solid state the Hf ion has distorted trigonal bipyramidal geometry.

Insulin-like Growth Factor-1 and mTORC1 Signaling Promote the Intestinal Regenerative Response After Irradiation Injury.

BACKGROUND & AIMS: Intestinal crypts have a remarkable capacity to regenerate after injury from loss of crypt base columnar (CBC) stem cells. After injury, facultative stem cells (FSCs) are activated to replenish the epithelium and replace lost CBCs. Our aim was to assess the role of insulin-like growth factor-1 (IGF-1) to activate FSCs for crypt repair. METHODS: The intestinal regenerative response was measured after whole body 12-Gy γ-irradiation of adult mice. IGF-1 signaling or its downstream effector mammalian target of rapamycin complex 1 (mTORC1) was inhibited by administering BMS-754807 or rapamycin, respectively. Mice with inducible Rptor gene deletion were studied to test the role of mTORC1 signaling in the intestinal epithelium. FSC activation post-irradiation was measured by lineage tracing. RESULTS: We observed a coordinate increase in growth factor expression, including IGF-1, at 2 days post-irradiation, followed by a surge in mTORC1 activity during the regenerative phase of crypt repair at day 4. IGF-1 was localized to pericryptal mesenchymal cells, and IGF-1 receptor was broadly expressed in crypt progenitor cells. Inhibition of IGF-1 signaling via BMS-754807 treatment impaired crypt regeneration after 12-Gy irradiation, with no effect on homeostasis. Similarly, rapamycin inhibition of mTORC1 during the growth factor surge blunted the regenerative response. Analysis of Villin-CreERT2;Rptorfl/fl mice showed that epithelial mTORC1 signaling was essential for crypt regeneration. Lineage tracing from Bmi1-marked cells showed that rapamycin blocked FSC activation post-irradiation. CONCLUSIONS: Our study shows that IGF-1 signaling through mTORC1 drives crypt regeneration. We propose that IGF-1 release from pericryptal cells stimulates mTORC1 in FSCs to regenerate lost CBCs.