FAP, familial adenomatous polyposis; LGR5, leucine-rich repeatCcontaining G-proteinCcoupled receptor 5. To assess the possibility that the observed increase in LGR5+ cell numbers in FAP crypts was because of younger age in subjects with FAP relative to healthy subjects, age was included as a covariate in the model used to test for count differences between groups. Colon crypts contain a dedicated stem cell compartment, and several molecular markers of colon stem cells have been proposed, including ASCL2, ALDH1, BMI1, CD24, CD44, CD133, CD166, LRIG1, MSI1, OLFM4, and PTK7. These markers have confirmed the base of the colon crypt as the stem cell niche (2,5C15). Recent evidence indicates that leucine-rich repeatCcontaining G-proteinCcoupled receptor 5 (LGR5), a transmembrane receptor that potentiates the canonical WNT signaling pathway, is the most specific and reliable marker of pluripotent cells in the colon. Protein immunostaining and transcript hybridization studies demonstrate that LGR5 Troglitazone is found exclusively in a minority of cells at the crypt base in healthy colon (16C20). Lineage tracing studies in mice demonstrate that LGR5+ cells give rise to all cell lineages observed in the colon crypt (16,21). Furthermore, isolated LGR5+ cells from mice and humans can lead to the generation of self-sustaining colon organoids (22,23). For these reasons, LGR5 has emerged as the best marker of stem cells in the colon. FAP is caused by inherited or germline mutations in the gene encoding the adenomatous polyposis coli (APC) protein, which is involved in cell proliferation and differentiation. Mutation carriers develop multiple adenomatous polyps in the colon and rectum, typically beginning in the second decade of life (24). By the third decade of life, approximately 95% of trait carriers have polyps, often in the hundreds to thousands. Nearly all subjects with FAP develop microsatellite stable CRC by an average age of 45 years (3,25). Lynch syndrome and = 0.4 and = 0.8, respectively). Table 3. LGR5+ cell counts = 4.9e-04) and subjects with Lynch syndrome (= 1.9e-03), and many LGR5+ cells were located above the crypt base (i.e., lower third) (Tables ?(Tables33 and ?and4;4; Figures ?Figures22 and ?and3;3; see Supplementary Figure 5a, Supplementary Digital Content 6, http://links.lww.com/CTG/A617). FAP crypts harbored higher numbers of LGR5+ cells than crypts of a single subject with MAP, but this observation needs to be verified Troglitazone in additional subjects with MAP (see Supplementary Figure 4d, Supplementary Digital Content 5, http://links.lww.com/CTG/A616). Nine of 18 (50%) FAP crypts had 4 or more LGR5+ cells, and 12 (66%) had LGR5+ cells located above the lower third of the crypt. A small increase in the average number of LGR5+ cells in crypts of subjects with Lynch syndrome relative to healthy subjects was not statistically significant (= 0.26) (Table ?(Table44). Table 4. Parameter estimation for GEE model fit value from generalized estimating equations estimate of coefficient (i.e., effect) of clinical diagnosis in model of cell count is less than 0.01. (b) Same dot plot as (a) with subjects labeled by color. (c) Crypt level counts for each subject represented by histograms within groups with points indicating the LGR5+ cell Troglitazone count in every crypt, with subjects labeled by CDK4 color. In histograms, the thin box represents the within-group interquartile range, the thick horizontal line represents the median, and the thin vertical bars extend to points 1.5 times the interquartile range. Small increments of random noise have been added to points to facilitate visualization. Color labels in (c) are different from labels in (b). FAP, familial adenomatous polyposis; LGR5, leucine-rich repeatCcontaining G-proteinCcoupled receptor 5. To assess the possibility that the observed increase in LGR5+ cell numbers Troglitazone in FAP crypts was because of younger age in.