Roeland Nusse, Postdoctoral Faculty Sponsor
In the liver, Wnt/beta-catenin signaling is involved in regulating zonation and hepatocyte proliferation during homeostasis. We have examined Wnt gene expression and signaling after injury and we show by in situ hybridization that Wnts are activated by acute carbon tetrachloride (CCl4 ) toxicity. Following injury, peri-injury hepatocytes become Wnt-responsive, expressing the Wnt target gene Axin2. Lineage tracing of peri-injury Axin2+ hepatocytes shows that during recovery, the injured parenchyma becomes repopulated and repaired by Axin2+ descendants. Using single cell RNA sequencing (scRNA-seq), we show that endothelial cells are the major source of Wnts following acute CCl4 toxicity. Induced loss of beta-catenin in peri-injury hepatocytes results in delayed repair and ultimately to injury-induced lethality, while loss of Wnt production from endothelial cells leads to a delay in the proliferative response after injury. CONCLUSION: Our findings highlight the importance of the Wnt/beta-catenin signaling pathway in restoring tissue integrity following acute liver toxicity and establishes a role of endothelial cells as an important Wnt-producing regulator of liver tissue repair following localized liver injury. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/hep.30563
View details for PubMedID 30762896
In the healthy adult liver, most hepatocytes proliferate minimally. However, upon physical or chemical injury to the liver, hepatocytes proliferate extensively in vivo under the direction of multiple extracellular cues, including Wnt and pro-inflammatory signals. Currently, liver organoids can be generated readily in vitro from bile-duct epithelial cells, but not hepatocytes. Here, we show that TNFα, an injury-induced inflammatory cytokine, promotes the expansion of hepatocytes in 3D culture and enables serial passaging and long-term culture for more than 6 months. Single-cell RNA sequencing reveals broad expression of hepatocyte markers. Strikingly, in vitro-expanded hepatocytes engrafted, and significantly repopulated, the injured livers of Fah-/- mice. We anticipate that tissue repair signals can be harnessed to promote the expansion of otherwise hard-to-culture cell-types, with broad implications.
View details for PubMedID 30500539
Intestinal epithelial renewal is mediated by intestinal stem cells (ISCs) that exist in a state of neutral drift, wherein individual ISC lineages are regularly lost and born but ISC numbers remain constant. To test whether an active mechanism maintains stem cell pools in the Drosophila midgut, we performed partial ISC depletion. In contrast to the mouse intestine, Drosophila ISCs failed to repopulate the gut after partial depletion. Even when the midgut was challenged to regenerate by infection, ISCs retained normal proportions of asymmetric division and ISC pools did not increase. We discovered, however, that the loss of differentiated midgut enterocytes (ECs) slows when ISC division is suppressed and accelerates when ISC division increases. This plasticity in rates of EC turnover appears to facilitate epithelial homeostasis even after stem cell pools are compromised. Our study identifies unique behaviors of Drosophila midgut cells that maintain epithelial homeostasis.
View details for DOI 10.1016/j.stemcr.2017.04.002
View details for PubMedID 28479306
View details for PubMedCentralID PMC5469868
Following gut epithelial damage, epidermal growth factor receptor/mitogen-activated protein kinase (EGFR/MAPK) signalling triggers Drosophila intestinal stem cells to produce enteroblasts (EBs) and enterocytes (ECs) that regenerate the gut. As EBs differentiate into ECs, they become postmitotic, but undergo extensive growth and DNA endoreplication. Here we report that EGFR/RAS/MAPK signalling is required and sufficient to drive damage-induced EB/EC growth. Endoreplication occurs exclusively in EBs and newborn ECs that inherit EGFR and active MAPK from fast-dividing progenitors. Mature ECs lack EGF receptors and are refractory to growth signalling. Genetic tests indicated that stress-dependent EGFR/MAPK promotes gut regeneration via a novel mechanism that operates independently of Insulin/Pi3K/TOR signalling, which is nevertheless required in nonstressed conditions. The E2f1 transcription factor is required for and sufficient to drive EC endoreplication, and Ras/Raf signalling upregulates E2f1 levels posttranscriptionally. We illustrate how distinct signalling mechanisms direct stress-dependent versus homeostatic regeneration, and highlight the importance of postmitotic cell growth in gut epithelial repair.
View details for DOI 10.1038/ncomms15125
View details for Web of Science ID 000400847400001
View details for PubMedID 28485389
View details for PubMedCentralID PMC5436070
Src non-receptor kinases have been implicated in events late in tumor progression. Here, we study the role of Src kinases in the Drosophila intestinal stem cell (ISC) lineage, during tissue homeostasis and tumor onset. The adult Drosophila intestine contains only two progenitor cell types, division-capable ISCs and their daughters, postmitotic enteroblasts (EBs). We found that Drosophila Src42a and Src64b were required for optimal regenerative ISC division. Conversely, activation of Src42a, Src64b or another non-receptor kinase, Ack, promoted division of quiescent ISCs by coordinately stimulating G1/S and G2/M cell cycle phase progression. Prolonged Src kinase activation caused tissue overgrowth owing to cytokine receptor-independent Stat92E activation. This was not due to increased symmetric division of ISCs, but involved accumulation of weakly specified Notch(+) but division-capable EB-like cells. Src activation triggered expression of a mitogenic module consisting of String/Cdc25 and Cyclin E that was sufficient to elicit division not only of ISCs but also of EBs. A small pool of similarly division-capable transit-amplifying Notch(+) EBs was also identified in the wild type. Expansion of intermediate cell types that do not robustly manifest their transit-amplifying potential in the wild type may also contribute to regenerative growth and tumor development in other tissues in other organisms.
View details for DOI 10.1038/onc.2014.163
View details for Web of Science ID 000353824800010
View details for PubMedID 24975577
The traditional Chinese soybean paste was produced by cooked transgenic soybean fermentation with the composition of moisture 53%, amino acid 0.84% (calculated by nitrogen), votive sugar 6.21% and total acid 1.66%. A number of microorganism species were isolated and identified, including fungi and bacteria, and the bacterium species Rhizopus oryzae Went and Prinsen Geerligs were dominant in transgenic soybean paste. The results showed that the transgenic soybean paste contain abundant amino acids and vitamins (vitamin A, 42.87 IU; vitamin B, 10.31 mg; vitamin B, 20.64 mg; nicotinamide, 2.54 mg; pantothenic acid, 0.63 mg; vitamin B, 6,847 microg; folic acid, 105 microg; vitamin B, 123.85 microg; and biotin, 56.34 microg). Pathogenic microorganisms were not be detected in the transgenic fermented soybean paste.
View details for DOI 10.1080/09637480701603173
View details for Web of Science ID 000262501700010
View details for PubMedID 18608534
With the rapid development of the transgenic food, more and more transgenic food has been pouring into the market attracting much attention to the transgenic food's edible safety. Transgenic corns and its parents were studied by ICP-MS to detect the heavy metals. The results showed that the transgenic corn accumulated less heavy metals (Ni, Cu, Cd, As, Cr, Zn and Hg) than their own parents; and the contents of some heavy metals (V, Co and Pb) in transgenic corns were similar to their parents. All the data showed that the insertion of foreign gene (Bt) might change the absorbing dynamics of most heavy metals, especially some important heavy metals, which are disadvantageous to human health. The present paper indicated that the change in heavy metals absorption could harm the edible safety of transgenic plant. The cause of this change should be studied further.
View details for Web of Science ID 000246217100043
View details for PubMedID 17608202
With the rapid development of transgenic food, more and more transgenic food has been pouring into the market, raising great concern about transgenic food' s edible safety. To analyze the content of erucic acid and glucosinolate in transgenic rapeseed and its parents, all the seeds were scanned intact by continuous wave of near infrared diffuse reflectance spectrometry ranging from 12 000 to 4 000 cm(-1) with a resolution of 4 cm(-1) and 64 times of scanning. Bruker OPUS software package was applied for quantification, while the results were compared with the standard methods. The results showed that the method of NIRS was very precise, which proved that infrared diffuse reflectance spectroscopy can be applied to detect the toxins in transgenic food. On the other hand, the results also showed that the content of erucic acid in transgenic rapeseeds is 0. 5-1. 0 times
View details for Web of Science ID 000243417700008
View details for PubMedID 17361706