Biology subjects

Nathke, I.

Publications and source records attributed to Nathke, I..

5 recordsLinked to original sources

bioRxiv2020

Ultrasound Mediated Delivery of Quantum Dots from a Capsule Endoscope to the Gastrointestinal Wall

Biologic drugs, defined as therapeutic agents produced from or containing components of a living organism, are of growing importance to the pharmaceutical industry. Though oral delivery of medicine is convenient, biologics require invasive injections because of their poor bioavailability via oral routes. Delivery of biologics to the small intestine using electronic delivery with devices that are similar to capsule endoscopes is a promising means of overcoming this limitation and does not require reformulation of the therapeutic agent. The efficacy of such capsule devices for drug delivery could be further improved by increasing the permeability of the intestinal tract lining with an integrated ultrasound transducer to increase uptake. This paper describes a novel proof of concept capsule device capable of electronic application of focused ultrasound and delivery of therapeutic agents. Fluorescent markers, which were chosen as a model drug, were used to demonstrate in-vivo delivery in the porcine small intestine with this capsule. We show that the fluorescent markers can penetrate the mucus layer of the small intestine at low acoustic powers when combining microbubbles with focussed ultrasound. These findings suggest that the use of focused ultrasound together with microbubbles could play a role in the oral delivery of biologic therapeutics.

bioengineering↗

bioRxiv2018

Loss of Adenomatous polyposis coli function renders intestinal epithelial cells resistant to the cytokine IL-22

Interleukin-22 (IL-22) is critical in maintaining homeostasis in the intestine by regulating the balance between pathogenic and commensal bacteria. IL-22 also promotes wound healing and tissue regeneration, which can support the growth of colorectal tumours. Mutations in the tumour suppressor Adenomatous Polyposis Coli gene (Apc) cause intestinal tumorigenesis and are a major driver of familial colorectal cancers. To understand the role of IL-22 in APC-mediated tumorigenesis, we analysed IL-22 signalling in wild-type (WT) and APC-mutant cells in murine small intestinal epithelial organoids and in mice. In WT epithelia, antimicrobial defence, mucus production, and cellular stress response pathways were most strongly upregulated by IL-22. Surprisingly, we found that although IL-22 activated STAT3 in APC-mutant cells, STAT3 target genes were not effectively induced. Our analyses revealed that ApcMin/Min cells were resistant to IL-22 due to reduced expression of the IL-22 receptor, and increased expression of inhibitors of STAT3, including histone deacetylases. We further show that IL-22 induced expression of nitric oxide synthase in WT epithelial cells and corresponding DNA damage. These findings suggest that IL-22 does not promotes tumour formation by driving the proliferation of transformed intestinal epithelial cells. Rather, IL-22 increases genetic instability thereby accelerating transition from heterozygosity (ApcMin/+) to homozygosity (ApcMin/Min) to drive tumour progression.

immunology↗

bioRxiv2018

Identification of endogenous Adenomatous polyposis coli interaction partners and β-catenin-independent targets by proteomics

Adenomatous polyposis coli (APC) is the most frequently mutated gene in colorectal cancer. APC negatively regulates the pro-proliferative Wnt signaling pathway by promoting the degradation of {beta}-catenin, but the extent to which APC exerts Wnt/{beta}-catenin-independent tumor suppressive activity is unclear. To identify interaction partners and {beta}-catenin-independent targets of endogenous, full-length APC, we applied label-free and multiplexed TMT mass spectrometry. Affinity enrichment-mass spectrometry revealed over 150 previously unidentified APC interaction partners. Moreover, our global proteomic analysis revealed that roughly half of the protein expression changes that occur in response to APC loss are independent of {beta}-catenin. By combining these two analyses, we identified Misshapen-like kinase 1 (MINK1) as a putative substrate of an alternative APC-containing destruction complex and provide evidence for the potential contribution of MINK1 to APC mutant phenotypes. Collectively, our results highlight the extent and importance of Wnt-independent APC functions in epithelial biology and disease.

cancer biology↗

bioRxiv2017

Delayed activation of the DNA replication licensing system in Lgr5(+) intestinal stem cells

During late mitosis and early G1, replication origins are licensed for replication by binding to double hexamers of MCM2-7. Here, we investigate how licensing and proliferative commitment are coupled in the small-intestinal epithelium. We developed a method for identifying cells in intact tissue containing DNA-bound MCM2-7. Interphase cells above the transit-amplifying compartment had no DNA-bound MCM2-7, but still expressed MCM2-7 protein, suggesting that licensing is inhibited immediately upon differentiation. Strikingly, we found most proliferative Lgr5(+) stem cells are in an unlicensed state. This suggests that the elongated cell-cycle of intestinal stem-cells is caused by an increased G1 length, characterised by dormant periods with unlicensed origins. Significantly, the unlicensed state is lost In Apc mutant epithelium, which lacks a functional restriction point, causing licensing immediately upon G1 entry. We propose that the unlicensed G1 of intestinal stem cells creates a temporal window when proliferative fate decisions can be made.

cell biology↗

bioRxiv2017

Postmitotic Separation Enables Selective Niche Retention Of One Daughter Cell In Intestinal Crypts And Is Facilitated By Interkinetic Nuclear Migration And Basal Tethering

Homeostasis of renewing tissues requires balanced proliferation, differentiation and movement. This is particullary important in the intestinal epithelium where lineage tracing suggests that stochastic differentiation choices are intricately coupled to position. To determine how position is achieved we followed proliferating cells in intestinal organoids and discovered that behaviour of mitotic sisters predicted long-term positioning. Normally, 70% of sisters remain neighbours while 30% lose contact separating after cytokinesis. Postmitotic placements predict differences in positions of sisters later: adjacent sisters reach similar positions; one separating sister remains close to its birthplace, the other moves upward. Computationally modelling crypt dynamics confirmed post-mitotic separation as a mechanism for placement of sisters into different niches. Separation depends on interkinetic nuclear migration, cell size, and asymmetric tethering by a basal process. These processes are altered when Adenomatous polyposis coli (Apc) is mutant and separation is lost. We conclude that post-mitotic placement enables stochastic niche exit and when defective, supports the clonal expansion of Apc mutant cells.

cancer biology↗