title: Retromer dependent recycling of the Wnt secretion factor Wls is dispensable for stem cell maintenance in the mammalian intestinal epithelium.
abstract: In C. elegans and Drosophila, retromer mediated retrograde transport of Wntless (Wls) from endosomes to the trans-Golgi network (TGN) is required for Wnt secretion. When this retrograde transport pathway is blocked, Wls is missorted to lysosomes and degraded, resulting in reduced Wnt secretion and various Wnt related phenotypes. In the mammalian intestine, Wnt signaling is essential to maintain stem cells. This prompted us to ask if retromer mediated Wls recycling is also important for Wnt signaling and stem cell maintenance in this system. To answer this question, we generated a conditional Vps35 (fl) allele. As Vps35 is an essential subunit of the retromer complex, this genetic tool allowed us to inducibly interfere with retromer function in the intestinal epithelium. Using a pan-intestinal epithelial Cre line (Villin-CreERT2), we did not observe defects in crypt or villus morphology after deletion of Vps35 from the intestinal epithelium. Wnt secreted from the mesenchyme of the intestine may compensate for a reduction in epithelial Wnt secretion. To exclude the effect of the mesenchyme, we generated intestinal organoid cultures. Loss of Vps35 in intestinal organoids did not affect the overall morphology of the organoids. We were able to culture Vps35 (∆/∆) organoids for many passages without Wnt supplementation in the growth medium. However, Wls protein levels were reduced and we observed a subtle growth defect in the Vps35 (∆/∆) organoids. These results confirm the role of retromer in the retrograde trafficking of Wls in the intestine, but show that retromer mediated Wls recycling is not essential to maintain Wnt signaling or stem cell proliferation in the intestinal epithelium.
authors.affiliation: Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences and University Medical Centre Utrecht, Utrecht, The Netherlands.
authors.forename: Reinoud E A
authors.initials: RE
authors.lastname: de Groot
authors.forename: Henner F
authors.initials: HF
authors.lastname: Farin
authors.forename: Marie
authors.initials: M
authors.lastname: Macůrková
authors.forename: Johan H
authors.initials: JH
authors.lastname: van Es
authors.forename: Hans C
authors.initials: HC
authors.lastname: Clevers
authors.forename: Hendrik C
authors.initials: HC
authors.lastname: Korswagen
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D053595:Embryonic Stem Cells / Q000166:cytology* / Q000378:metabolism*; D055786:Gene Knockout Techniques; D007413:Intestinal Mucosa / Q000166:cytology*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D051379:Mice; D021381:Protein Transport; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000172:deficiency / Q000235:genetics; D051153:Wnt Proteins / Q000378:metabolism*
chemical_list: C545200:Gpr177 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D043562:Receptors, G-Protein-Coupled; D033921:Vesicular Transport Proteins; C101274:Vps35 protein, mouse; D051153:Wnt Proteins