Heterogeneity in readouts of canonical wnt pathway activity within intestinal crypts.
Canonical Wnt pathway signaling is necessary for maintaining the proliferative capacity of mammalian intestinal crypt base columnar stem cells (CBCs). Furthermore, dysregulation of the Wnt pathway is a major contributor to disease, including oncogenic transformation of the intestinal epithelium. Given the critical importance of this pathway, numerous tools have been used as proxy measures for Wnt pathway activity, yet the relationship between Wnt target gene expression and reporter allele activity within individual cells at the crypt base remains unclear.



Here, we describe a novel Axin2-CreERT2-tdTomato allele that efficiently marks both Wnt(High) CBCs and radioresistant reserve intestinal stem cells. We analyze the molecular and functional identity of Axin2-CreERT2-tdTomato-marked cells using single cell gene expression profiling and tissue regeneration assays and find that Axin2 reporter activity does not necessarily correlate with expression of Wnt target genes and, furthermore, that Wnt target genes themselves vary in their expression patterns at the crypt base.



Wnt target genes and reporter alleles can vary greatly in their cell-type specificity, demonstrating that these proxies cannot be used interchangeably. Furthermore, Axin2-CreERT2-tdTomato is a robust marker of both active and reserve intestinal stem cells and is thus useful for understanding the intestinal stem cell compartment. Developmental Dynamics 245:822-833, 2016. © 2016 Wiley Periodicals, Inc.
Department of Biomedical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
Ning
N
Li
Department of Biomedical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
Maryam
M
Yousefi
Department of Biomedical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
Angela
A
Nakauka-Ddamba
Penn Genomic Analysis Core, University of Pennsylvania, Philadelphia, Pennsylvania.
John W
JW
Tobias
Department of Statistics, Wharton School, University of Pennsylvania, Philadelphia, Pennsylvania.
Shane T
ST
Jensen
Department of Cell and Developmental Biology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.|Department of Medicine, Penn Center for Pulmonary Biology, Penn Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.|Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
Edward E
EE
Morrisey
Department of Biomedical Sciences, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.|Department of Medicine, Penn Center for Pulmonary Biology, Penn Cardiovascular Institute, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.|Institute for Regenerative Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.
Christopher J
CJ
Lengner
D000818:Animals; D060466:Axin Protein / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D049109:Cell Proliferation / Q000235:genetics / Q000502:physiology; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D007120:Immunochemistry; D007413:Intestinal Mucosa / Q000166:cytology* / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism* / Q000502:physiology; D060449:Wnt Signaling Pathway / Q000235:genetics / Q000502:physiology*
D060466:Axin Protein; C111729:Axin2 protein, mouse
Bmi1; Crypt base columnar stem cells; Hopx; Lgr5; Wnt signaling; intestine; quiescent stem cells; reserve stem cells