Mouse small intestine epithelium vs. mesenchyme

During organogenesis of the intestine, reciprocal crosstalk between the endodermally-derived epithelium and the underlying mesenchyme is required for regional patterning and proper differentiation. Though both of these tissue layers participate in patterning, the mesenchyme is thought to play a prominant role in the determination of epithelial phenotype during development and in adult life. However, the molecular basis of this instructional dominance is unclear. In fact, surprisingly little is known about the cellular origins of many of the critical signaling molecules and the gene transcriptional events that they impact. Here, we profile genes that are expressed in separated mesenchymal and epithelial compartments of the perinatal mouse intestine. The data indicate that the vast majority of soluble modulators of signaling pathways such as Hedgehog, Bmp, Wnt, Fgf and Igf are expressed predominantly or exclusively by the mesenchyme, accounting for its ability to dominate instructional crosstalk. We also catalog the most highly enriched transcription factors in both compartments and find evidence for a major role for Hnf4alpha and Hnf4 gamma in the regulation of epithelial genes. Finally, we find that while epithelially enriched genes tend to be highly tissue-restricted in their expression, mesenchymally-enriched genes tend to be broadly expressed in multiple tissues. Thus, the unique tissue-specific signature that characterizes the intestinal epithelium is instructed and supported by a mesenchyme that itself expresses genes that are largely non-tissue specific.

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Li X, Madison BB, Zacharias W, Kolterud A, States D, Gumucio DL