Molecular and cellular biology of the small intestine

The mucosa of the small intestine is an essential tissue with intriguing biology. It is a paradigm to help understand the development, growth, differentiation, and renewal of columnar epithelial surfaces. The mucosal epithelium is a dynamic structure that is formed during the interaction of yolk sac endoderm with the mesoderm early during fetal development. it is continually renewed throughout adult life by multipotent stem cells capable of differentiating into several mature lineages. The cellular processes that lead to the development of the mucosa, such as migration, cell fate determination, proliferation, differentiation, and cell death, are recapitulated in the adult mouse throughout life. Current studies have led to a better understanding of the molecular events that control these processes, Lineage-specific gene expression occurs under complex control by both positive and negative transcription control elements and is undoubtedly regulated by extracellular signaling along the crypt-to-villus axis, The intestinal epithelial cell forms intimate contacts with T lymphocytes, which in turn may regulate epithelial cell growth and barrier function, As mature epithelial cells are produced, they express a variety of intestine-specific gene products involved in digestive, absorptive, cell migratory, and cell protection functions. To better understand the nature and fate of epithelial stem cells, genetic analysis of Caenorhabditis elegans and mice has proven to be fruitful and deserves further analysis.