Bone Morphogenetic Protein (BMP) signaling directs the development of multiple organs and tissues in embryogenesis, and is the causative factor in multiple congenital and adult diseases, including cardiovascular and limb defects, kidney disease, pulmonary hypertension, and is important in medical applications such as orthopedics, endodontics, and tissue engineering. BMP heterodimers have been shown to exhibit consistently higher signaling activity to BMP homodimers and thus are beginning to be used in therapeutics. To understand how BMP signaling can generate diverse cellular responses in a myriad of biological contexts and affect disease, as well as how BMP heterodimers can most effectively be used in therapeutics, it is imperative to understand the mechanism by which they signal. A key function of BMP signaling in vertebrate development is to pattern the cells along the dorsoventral (DV) embryonic axis during late blastula and gastrula stages. BMP signaling activity is thought to act as a morphogen, specifying distinct cell types at different activity levels. Dorsally-emanating BMP antagonists are important in generating the gradient of BMP activity with low levels dorsally and highest levels ventrally. The gradient of BMP signaling activity has now been visualized at high resolution across the DV axis of the vertebrate embryo. Using phosphorylation of Smad5 (P-Smad5) as a direct readout of BMP signaling, a quantitative method was established to measure P-Smad5 levels in all nuclei of the early zebrafish embryo. Using this highly sensitive, reproducible P-Smad5 immunofluorescence assay, the dynamics and overall properties of the signaling gradient have been determined with high precision. The role of the BMP antagonists Chordin, Noggin, and Follistatin in shaping the gradient are being investigated. The studies here will extend these to determine how the gradient is modulated during the extensive morphogenetic movements of gastrulation and how the Chordin inhibitor, the Tolloid and Bmp1a metalloproteases, and their inhibitor Sizzled, modulate the gradient to establish and maintain it throughout gastrulation as the embryo dimensions change dramatically. The exclusive ligand signaling in DV patterning is a Bmp2-Bmp7 heterodimer, which will also be investigated. This BMP heterodimer signals through two distinct classes of BMP Type I receptor, BmpR1 and Acvr1, that are assembled together in a signaling complex. In the previous grant period, it was found that the kinase activities of the Type I receptors differentially function in the signaling complex. The studies here will use the unique in vivo vertebrate model setting of zebrafish DV patterning to elucidate the mechanism of BMP heterodimer signaling, deciphering the specific roles of each Type I receptor in the signaling complex and the roles of the Type II receptors. Altogether the results will be broadly relevant to BMP heterodimer signaling and its modulation in other biological contexts, in their use in the clinic, and in modulating stem cell tissue differentiation in vitro.

Public Health Relevance

The Bone Morphogenetic Protein (BMP) and TGF? family of secreted signaling factors direct the development of multiple organs and tissue types and are implicated in congenital and adult diseases. Ongoing investigations suggest the potential for modulating BMP and TGF? signaling in the treatment of disorders as diverse as kidney disease, pulmonary hypertension, pancreatic, colorectal, and other cancers, and in medical applications such as orthopedics, endodontics, bone regeneration, and tissue engineering. To understand how BMP signaling can generate diverse cellular responses in a myriad of biological contexts and affect disease, it is imperative to understand the mechanism by which BMPs signal and how these signals are regulated in tissue development, as will be studied here.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM056326-18
Application #
9196469
Study Section
Special Emphasis Panel (ZRG1-CB-R (02)M)
Program Officer
Hoodbhoy, Tanya
Project Start
1997-08-01
Project End
2020-07-31
Budget Start
2016-09-25
Budget End
2017-07-31
Support Year
18
Fiscal Year
2016
Total Cost
$416,033
Indirect Cost
$154,536
Name
University of Pennsylvania
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Mucha, Bettina E; Hashiguchi, Megumi; Zinski, Joseph et al. (2018) Variant BMP receptor mutations causing fibrodysplasia ossificans progressiva (FOP) in humans show BMP ligand-independent receptor activation in zebrafish. Bone 109:225-231
Tajer, Benjamin; Mullins, Mary C (2017) Heterodimers reign in the embryo. Elife 6:
Zinski, Joseph; Bu, Ye; Wang, Xu et al. (2017) Systems biology derived source-sink mechanism of BMP gradient formation. Elife 6:
Escobar-Aguirre, Matias; Elkouby, Yaniv M; Mullins, Mary C (2017) Localization in Oogenesis of Maternal Regulators of Embryonic Development. Adv Exp Med Biol 953:173-207
Langdon, Yvette G; Fuentes, Ricardo; Zhang, Hong et al. (2016) Split top: a maternal cathepsin B that regulates dorsoventral patterning and morphogenesis. Development 143:1016-28
Elkouby, Yaniv M; Jamieson-Lucy, Allison; Mullins, Mary C (2016) Oocyte Polarization Is Coupled to the Chromosomal Bouquet, a Conserved Polarized Nuclear Configuration in Meiosis. PLoS Biol 14:e1002335
Tuazon, Francesca B; Mullins, Mary C (2015) Temporally coordinated signals progressively pattern the anteroposterior and dorsoventral body axes. Semin Cell Dev Biol 42:118-33
Ge, Xiaoyan; Grotjahn, Danielle; Welch, Elaine et al. (2014) Hecate/Grip2a acts to reorganize the cytoskeleton in the symmetry-breaking event of embryonic axis induction. PLoS Genet 10:e1004422
Kapp, Lee D; Abrams, Elliott W; Marlow, Florence L et al. (2013) The integrator complex subunit 6 (Ints6) confines the dorsal organizer in vertebrate embryogenesis. PLoS Genet 9:e1003822
Hashiguchi, Megumi; Mullins, Mary C (2013) Anteroposterior and dorsoventral patterning are coordinated by an identical patterning clock. Development 140:1970-80

Showing the most recent 10 out of 30 publications