The impressively large absorptive surface area of the intestine is largely contributed by its length as well as the extensive surface amplification provided by millions of fingerlike villus projections. Congenital or acquired pathologies that result in significant loss of this intestinal surface area seriously compromise the ability of the intestine to absorb nutrients and can be life threatening. Work in the past project period has begun to identify some of the cellular and molecular mechanisms that control the formation of villi in utero in the murine model. The period between embryonic day (E) 14.5 and E15.5 (in the mouse) is particularly important since during this time, controlled morphogenic remodeling in both the epithelium and the underlying mesenchyme results in the emergence of villi. The Working Hypothesis underlying these studies is that: Villus development is actively inhibited by Bmp signaling prior to E14.5. At E14.5, epithelial Hh signals initiate villus development by promoting the formation of mesenchymal clusters. Cluster patterning proceeds via a Turing system and vascular coupling to these clusters precedes and is required for villus emergence. Importantly, since the morphological hallmarks of all of these events are also present in the human intestine, it is likely that the majority of the signaling paradigms uncovered in the mouse model will be applicable to the human intestine. This proposal makes use of genetic mouse models as well as a novel intestinal explant culture system to mechanistically dissect the interconnected signaling and patterning events involved in these surface- generating processes. Additionally, a new software tool that can recognize Hh-responsive signaling enhancers in genomic DNA with high efficiency will aid in the recognition of Hh target genes.
The Specific Aims are designed to 1) Determine how Bmp signaling controls competence to form villi and establish which tissue (epithelium or mesenchyme) exerts this control;2) Identify Hh target genes during the formation of mesenchymal clusters;and 3) Determine the relationship between vascular elements, forming clusters and cluster pattern. Through detailed analysis of these linked processes, the goal of these studies is to gain new insight into the formation of the intestinal absorptive surface. The ability to bioengineer organs from their cellular components will require not only that we elucidate the molecular signals that are important for morphogenesis and cell fate determination, but also that we understand the rules that govern the patterning of the functional units that comprise the organ. The unique focus of this investigation on signaling crosstalk in the nascent villus unit (epithelium, mesenchyme, vasculature) will have a major impact on our understanding of how intestinal villi are first formed in the embryo.
The surface of the small intestine is highly convoluted by finger-like projections called villi;this extended surface area is critical for efficient nutrient absorption. Loss of intestinal surface area either by congenital intestinal defects or by pathological or surgical events, can be life threatening. The ability to bioengineer the intestine from its cellular components will require not only that we elucidate the molecular signals that are important for morphogenesis and cell fate determination, but also that we understand the rules that govern the patterning of the functional units that comprise the organ. Currently, little is known about how villi are generated in utero. Through the study of mouse models with perturbed villus formation and through the analysis of a novel intestinal explant culture system, we propose to dissect the molecular processes responsible for villus emergence. The unique focus of this investigation on signaling crosstalk in the nascent villus unit (epithelium, mesenchyme, vasculature) will have a major impact on our understanding of how intestinal villi are first formed in the embryo.
|Whiteman, Eileen L; Fan, Shuling; Harder, Jennifer L et al. (2014) Crumbs3 is essential for proper epithelial development and viability. Mol Cell Biol 34:43-56|
|Walton, Katherine D; Kolterud, Asa (2014) Mouse fetal whole intestine culture system for ex vivo manipulation of signaling pathways and three-dimensional live imaging of villus development. J Vis Exp :e51817|
|Prakash, Ajay; Udager, Aaron M; Saenz, David A et al. (2014) Roles for Nkx2-5 and Gata3 in the ontogeny of the murine smooth muscle gastric ligaments. Am J Physiol Gastrointest Liver Physiol 307:G430-6|
|Udager, Aaron M; Prakash, Ajay; Saenz, David A et al. (2014) Proper development of the outer longitudinal smooth muscle of the mouse pylorus requires Nkx2-5 and Gata3. Gastroenterology 146:157-65.e10|
|Liu, Hong Xiang; Ermilov, Alexandre; Grachtchouk, Marina et al. (2013) Multiple Shh signaling centers participate in fungiform papilla and taste bud formation and maintenance. Dev Biol 382:82-97|
|Zacharias, William J; Madison, Blair B; Kretovich, Katherine E et al. (2011) Hedgehog signaling controls homeostasis of adult intestinal smooth muscle. Dev Biol 355:152-62|
|Grosse, Ann S; Pressprich, Mark F; Curley, Lauren B et al. (2011) Cell dynamics in fetal intestinal epithelium: implications for intestinal growth and morphogenesis. Development 138:4423-32|
|Zacharias, William J; Li, Xing; Madison, Blair B et al. (2010) Hedgehog is an anti-inflammatory epithelial signal for the intestinal lamina propria. Gastroenterology 138:2368-77, 2377.e1-4|
|Li, Xing; Udager, Aaron M; Hu, Chunbo et al. (2009) Dynamic patterning at the pylorus: formation of an epithelial intestine-stomach boundary in late fetal life. Dev Dyn 238:3205-17|
|Kolterud, Asa; Grosse, Ann S; Zacharias, William J et al. (2009) Paracrine Hedgehog signaling in stomach and intestine: new roles for hedgehog in gastrointestinal patterning. Gastroenterology 137:618-28|
Showing the most recent 10 out of 13 publications