The related retinoblastoma (pRb) and p130 proteins cooperate to regulate homeostasis in the intestinal epithelium.
pRb, p107, and p130 are related proteins that play a central role in the regulation of cell cycle progression and terminal differentiation in mammalian cells. Nevertheless, it is still largely unclear how these proteins achieve this regulation in vivo. The intestinal epithelium is an ideal in vivo system in which to study the molecular pathways that regulate proliferation and differentiation because it exists in a constant state of development throughout an animal's lifetime. We studied the phenotypic effects on the intestinal epithelium of mutating Rb and p107 or p130. Although mutating these genes singly had little or no effect, loss of pRb and p107 or p130 together produced chronic hyperplasia and dysplasia of the small intestinal and colonic epithelium. In Rb/p130 double mutants this hyperplasia was associated with defects in terminal differentiation of specific cell types and was dependent on the increased proliferation seen in the epithelium of mutant animals. At the molecular level, dysregulation of the Rb pathway led to an increase in the expression of Math1, Cdx1, Cdx2, transcription factors that regulate proliferation and differentiation in the intestinal epithelium. The absence of Cdx1 function in Rb/p130 double mutant mice partially reverted the histologic phenotype by suppressing ectopic mitosis in the epithelium. These studies implicate the Rb pathway as a regulator of epithelial homeostasis in the intestine.
Haigis
Kevin
K
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
Sage
Julien
J
Glickman
Jon
J
Shafer
Sarah
S
Jacks
Tyler
T
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D000071616:CDX2 Transcription Factor; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D018398:Homeodomain Proteins / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology*; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010641:Phenotype; D016160:Retinoblastoma Protein / Q000378:metabolism; D050720:Retinoblastoma-Like Protein p107 / Q000235:genetics / Q000378:metabolism*; D050717:Retinoblastoma-Like Protein p130 / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D000071616:CDX2 Transcription Factor; D018398:Homeodomain Proteins; D016160:Retinoblastoma Protein; D050720:Retinoblastoma-Like Protein p107; D050717:Retinoblastoma-Like Protein p130; D014157:Transcription Factors; C500943:Atoh1 protein, mouse; C491272:Cdx1 protein, mouse; C487514:Cdx2 protein, mouse