Michel Bagnat, Ph.D. (EMBL, Heidelberg)
Associate Professor, Department of Cell Biology
HHMI Faculty Scholar
333B Nanaline Duke Bldg., Box 3709
Duke University Medical Center
Durham, NC 27710
Cellular and Physiologic Mechanisms Controlling Morphogenesis
Our laboratory is interested in studying how basic cellular processes define the shape and size of complex multicellular structures such as organs. Fluid movement into enclosed luminal or intracellular spaces creates hydrostatic pressure that can serve as a driving force for organogenesis and long range morphogenetic events such as axis elongation.
Our major goal to understand the role hydrostatic pressure plays as a developmental force. Using zebrafish we investigate:
1-Regulation of fluid secretion and the role of fluid pressure in organogenesis.
2-The biogenesis and function of fluid-filled vacuoles in the notochord during embryogenesis and spine morphogenesis.
3-Cellular mechanisms controlling epithelial polarization and lumen formation in the gut tube.
Regulation of Fluid Secretion
Fluid secretion is important for both developmental processes such as lumen expansion during organogenesis as well as in human diseases such as cystic fibrosis, polycystic kidney disease and secretory diarrheas.
During morphogenesis fluid secretion drives lumen expansion in many organs. Fluid secretion is typically driven by modulating osmotic gradients, regulated by the movement of anions. An important anion channel regulating fluid secretion in vertebrate development and disease is CFTR. In the zebrafish, cftr regulates fluid secretion and lumen expansion necessary for the function of Kupffer's vesicle, an early fluid-filled organ. We are continuing to investigate new roles for cftr-dependent fluid secretion during organogenesis.
Genetic control of fluid secretion:
We have taken a forward genetic approach to uncover novel regulators of fluid secretion. By mapping mutants with misregulated fluid secretion and accumulation, we hope to identify new therapeutic targets for treatment of human diseases and disorders.
Notochord Vacuoles and Spine Formation
The zebrafish notochord is comprised of large fluid-filled vacuoles. The notochord acts as a hydrostatic skeleton for the embryo early in development and works to elongate the embryo along the anterior-posterior axis. Later during development the notochord provides a rigid framework for bone deposition during spine formation. We have shown that when notochord vacuoles are disrupted, the embryos are shorter and the spine develops kinks, similar to those seen in scoliosis patients. Using zebrafish we are studying the cellular and molecular mechanisms controlling notochord vacuole biogenesis and how the notochord acts a hydrostatic scaffold during spine formation. These studies provide a framework for the understanding of the developmental roles of the vertebrate notochord and the etiology of scoliosis.
Tube Formation and Epithelial Polarity
Most internal organs are networks of interconnected tubes that transport fluids. The transport of ions, water and various substances across body compartments depends on the ability of epithelial cells within tubes to develop and maintain a polarized distribution of channels, pores and transporters. On the other hand, membrane polarization is also intimately linked to the tubulogenesis process. Using zebrafish as a model system our laboratory follows an integrated approach combining forward and reverse genetics and genomics to study tube formation in the gut.
Single lumen formation:
Although tubes develop in a variety of ways, a defining characteristic of a tube is the presence of a single central lumen. We use the zebrafish gut as a model to investigate the process of lumen formation. We have previously shown that fluid accumulation is required for the enlargement and coalescence of multiple small lumens. Currently, we are investigating additional mechanisms that regulate cellular rearrangements during the process of single lumen formation.
Epithelial polarization and apical membrane biogenesis:
The biogenesis of the apical surface is of particular interest in lumen formation of organs during development and defects in apical protein sorting have been linked to the etiology of numerous diseases. We are interested in determining how biogenesis of the apical surface occurs by following a comprehensive approach combining forward genetics in zebrafish and cell biological methods to elucidate genes involved in apical membrane biogenesis and lumen formation.
Confocal image of a 5dpf transgenic zebrafish larva in cross section
Garcia, Jamie, Bagwell, Jennifer, Njaine, Brian, Norman, James, Levic, Daniel S., Wopat, Susan, Miller, Sara E., Liu, Xiaojing, Locasale, Jason W., Stainier, Didier Y.R., Bagnat, Michel. (2017) Sheath Cell Invasion and Trans-differentiation Repair Mechanical Damage Caused by Loss of Caveolae in the Zebrafish Notochord. Current Biology. 0960-9822.
Cao J, Navis A, Cox BD, Dickson AL, Gemberling M, Karra R, Bagnat M, Poss KD. (2016) Single epicardial cell transcriptome sequencing identifies Caveolin 1 as an essential factor in zebrafish heart regeneration. Development 143(2): 232-43.
***Marjoram L, Alvers A, Deerhake ME, Bagwell J, Mankiewicz J, Cocchiaro J, Beerman RW, Willer J, Katsanis N, Tobin DM, Rawls JF, Goll M, Bagnat M (2015) Epigenetic control of intestinal barrier function and inflammation in zebrafish. Proc Natl Acad Sci USA. 112:2770-75.
Marjoram L, Bagnat M. (2015) Infection, Inflammation and Healing in Zebrafish: Intestinal Inflammation. Curr Pathobiol Rep. 1;3(2):147-153.
Rodríguez-Fraticelli AE, Bagwell J, Bosch-Fortea M, Boncompain G, Reglero-Real N, Andrés G, Alonso MA, Millán J, Perez F, Bagnat M and Martín-Belmonte F (2015) Developmental regulation of apical endocytosis controls epithelial patterning in vertebrate tubular organs. Nat. Cell Bio. 17:241-50
Navis A, Bagnat M. (2015) Developing pressures: fluid forces driving morphogenesis. Curr Opin Genet Dev. 32:24-30.
Navis A and Bagnat M (2015) Loss of cftr function leads to pancreatic destruction in juvenile zebrafish. Dev. Bio. 2:237-248.
Alvers AL, Ryan S, Scherz PJ, Huisken J, Bagnat M (2014) Single continuous lumen formation in the zebrafish gut is mediated by smoothened-dependent tissue remodeling. Development. 141:1110-1119.
Gray RS, Wilm TP, Smith J, Bagnat M, Dale RM, Topczewski J, Johnson SL, Solnica-Krezel, L (2014) Loss of col8a1a function during zebrafish embryogenesis results in congenital vertebral malformations. Dev. Biol. 386:72-85.
Ryan S, Willer J, Marjoram L, Bagwell J, Mankiewicz J, Leshchiner I, Goessling W, Bagnat M, and Katsanis N (2013) Rapid identification of kidney cyst mutations by whole exome sequencing in zebrafish. Development. 140:4445-4451.
Ellis K, Hoffman BD, Bagnat M (2013) The vacuole within: How cellular organization dictates notochord function. Bioarchitecture. 26;3(3).
Ellis K, Bagwell J, Bagnat M (2013). Notochord vacuoles are lysosome-related organelles that function in axis and spine morphogenesis. J. Cell Biol. 200(5):667-679.
**This article is featured in:In Focus: Notochord vacuoles make a rod for the vertebrate back. J Cell Biol. 200(5):553- and: SCIENCENOW: and: Science in the Clouds
Navis A, Marjoram L, and Bagnat, M (2013) Cftr controls lumen expansion and function of Kupffer’s vesicle in zebrafish. Development 140(8):1703-12.