A Diffusion-like Process Accommodates New Crypts During Clonal Expansion in Human Colonic Epithelium

Gastroenterology. 2021 Aug;161(2):548-559.e23. doi: 10.1053/j.gastro.2021.04.035. Epub 2021 Apr 22.


Background & aims: Colorectal cancer (CRC) is thought to arise when the cumulative mutational burden within colonic crypts exceeds a certain threshold that leads to clonal expansion and ultimately neoplastic transformation. Therefore, quantification of the fixation and subsequent expansion of somatic mutations in normal epithelium is key to understanding colorectal cancer initiation. The aim of the present study was to determine how advantaged expansions can be accommodated in the human colon.

Methods: Immunohistochemistry was used to visualize loss of the cancer driver KDM6A in formalin-fixed paraffin-embedded (FFPE) normal human colonic epithelium. Combining microscopy with neural network-based image analysis, we determined the frequencies of KDM6A-mutant crypts and fission/fusion intermediates as well as the spatial distribution of clones. Mathematical modeling then defined the dynamics of their fixation and expansion.

Results: Interpretation of the age-related behavior of KDM6A-negative clones revealed significant competitive advantage in intracrypt dynamics as well as a 5-fold increase in crypt fission rate. This was not accompanied by an increase in crypt fusion. Mathematical modeling of crypt spacing identifies evidence for a crypt diffusion process. We define the threshold fission rate at which diffusion fails to accommodate new crypts, which can be exceeded by KRAS activating mutations.

Conclusions: Advantaged gene mutations in KDM6A expand dramatically by crypt fission but not fusion. The crypt diffusion process enables accommodation of the additional crypts up to a threshold value, beyond which polyp growth may occur. The fission rate associated with KRAS mutations offers a potential explanation for KRAS-initiated polyps.

Keywords: Colorectal Cancer Initiation; Crypt Fission; Crypt Fusion; Intestinal Crypt.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Cell Proliferation*
  • Cell Transformation, Neoplastic / genetics*
  • Cell Transformation, Neoplastic / metabolism
  • Cell Transformation, Neoplastic / pathology
  • Colonic Polyps / genetics*
  • Colonic Polyps / metabolism
  • Colonic Polyps / pathology
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / metabolism
  • Colorectal Neoplasms / pathology
  • Diffusion
  • Epithelial Cells / metabolism
  • Epithelial Cells / pathology*
  • Female
  • Histone Demethylases / genetics*
  • Histone Demethylases / metabolism
  • Humans
  • Intestinal Mucosa / metabolism
  • Intestinal Mucosa / pathology*
  • Male
  • Middle Aged
  • Models, Biological
  • Mutation*
  • Neoplastic Stem Cells / metabolism
  • Neoplastic Stem Cells / pathology*
  • Proto-Oncogene Proteins p21(ras) / genetics*
  • Proto-Oncogene Proteins p21(ras) / metabolism
  • Young Adult


  • KRAS protein, human
  • Histone Demethylases
  • KDM6A protein, human
  • Proto-Oncogene Proteins p21(ras)