Gut-specific Lymphatic Patterns and Progenitor Heterogeneity During Intestinal Health and Disease
Principal Investigator: Natasza Kurpios
DESCRIPTION (provided by applicant):
The embryonic midgut must rotate in a complex yet stereotypical pattern to assume the familiar positioning within the body cavity. Failure of this process causes malrotation and predisposes to catastrophic midgut volvulus, a strangulation of the gut and associated vasculature. Our research has established the highly conserved molecular mechanisms by which the mechanical rotation of the gut is achieved, orchestrated by the conserved symmetry breaking transcription factor Pitx2. More recently we have shown that the same organ asymmetry mechanisms pattern the complex network of blood and lymphatic vessels that supply and drain the vertebrate gut. Thus with one core molecular repertoire, the developing gut assumes early structural, molecular and vascular asymmetries that determine the form and function of the adult organ. In the dorsal mesentery, a bridge of mesodermal tissue that suspends the gut within the body cavity, the arteries and lymphatics that supply the future gut arise downstream of a Pitx2-Cxcl12 signaling pathway, which directs the progressive assembly of Cxcr4‑positive angioblasts into endothelial cords and patent vessels. We have shown that loss of Pitx2, Cxcr4 or Cxcl12 function disrupts artery and lymphatic formation specifically in the gut, and targets a novel population of lymphatic precursors that is distinct from those derived from mesenteric lymph sac. Gut lymphatics have a crucial role in absorption of dietary lipids, a function that separates them from all other lymphatic networks in the body. While our data highlight that the eventual formation of lymphatics depends on the prior assembly of the arterial network, the specific mechanisms of this relationship remain unclear. In our first aim, we address the specific roles and timing of Pitx2 expression during lymphatic patterning and physiology. Using Pitx2 mutant mouse lines, we will connect the earliest embryonic laterality pathways with organ-intrinsic patterns of lymphatic vasculature in the gut. In our second aim, we test the relationship between Pitx2 and Vegf‑C in the mouse gut and utilizing the accessibility of chicken embryo. In our third aim, we will ablate Cxcr4 in arterial, lymphatic or generalized endothelium using Cx40-, Prox1‑ and Tie2-CRE drivers of tamoxifen‑inducible Cre. We will test the ability of Cxcr7, a second receptor for Cxcl12, to compensate for Cxcr4 loss using Cxcr7 mutant and reporter mice. Lessons learned from these experiments will change the way we consider and study lymphatics of the mammalian intestine, and will shed new light on potential targets of local lymphatics in diseases of the gut.