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Although many regulatory networks involved in defining definitive endoderm have been identified, the mechanisms through which these networks interact to pattern the endoderm are less well understood. To explore the mechanisms involved in midgut patterning, we dissected the transcriptional regulatory elements of nephrocan (Nepn), the earliest known midgut specific gene in mice. We observed that Nepn expression is dramatically reduced in Sox17(-/-) and Raldh2(-/-) embryos compared with wild-type embryos. We further show that Nepn is directly regulated by Sox17 and the retinoic acid (RA) receptor via two enhancer elements located upstream of the gene. Moreover, Nepn expression is modulated by Activin signaling, with high levels inhibiting and low levels enhancing RA-dependent expression. In Foxh1(-/-) embryos in which Nodal signaling is reduced, the Nepn expression domain is expanded into the anterior gut region, confirming that Nodal signaling can modulate its expression in vivo. Together, Sox17 is required for Nepn expression in the definitive endoderm, while RA signaling restricts expression to the midgut region. A balance of Nodal/Activin signaling regulates the anterior boundary of the midgut expression domain.

Original publication

DOI

10.1242/dev.108274

Type

Journal article

Journal

Development

Publication Date

10/2014

Volume

141

Pages

3772 - 3781

Keywords

Midgut definitive endoderm, Mouse, Nephrocan (Nepn), Nodal/Activin A, Retinoic acid, Sox17, Activins, Aldehyde Oxidoreductases, Animals, Body Patterning, Electrophoretic Mobility Shift Assay, Endoderm, Gastrointestinal Tract, Gene Expression Regulation, Developmental, Gene Regulatory Networks, Genetic Vectors, Glycoproteins, HMGB Proteins, Luciferases, Mice, Mice, Knockout, Real-Time Polymerase Chain Reaction, Receptors, Retinoic Acid, SOXF Transcription Factors, Signal Transduction