Genetic studies have demonstrated that heparan sulfate proteoglycans (HSPGs) are essential for reception of growth factors on the cell surface, formation of morphogen gradients, and axon guidance. HSPGs function in many different biological contexts, yet very little is known about the molecular basis for their activities. We are using the genetic tools available in Drosophila to investigate several outstanding questions in proteoglycan biology, including mechanisms regulating HSPG function and new developmental roles for HSPGs. One important yet unsolved question is how the specificity of HSPG functions for different ligand proteins is generated. HS chains have markedly heterogeneous structures produced by the regulated introduction of N-, 2-O-, 6-O-, and 3-O-sulfate groups. Evidence suggests that these "fine structures" of HS control discrete signaling events at the cell surface. The molecular mechanisms for this control, however, are largely unknown. One of our goals is to understand how specific HS fine structures are generated and function in vivo during development. Another goal of our research is to identify and explore novel roles of HSPGs in development. We previously found that HSPGs regulate the gradient formation of morphogens in the developmental field. We now propose a new model that HSPGs are also involved in the formation of the stem cell niche, another developmental process where cells receive positional cues in a strictly controlled fashion. Our preliminary study strongly suggests that HSPGs are required for the establishment of the germline stem cell (GSC) niche in the developing ovary through a different mode of action from their activity in the developing wing. We propose to elucidate the molecular mechanisms by which HSPGs regulate the formation of the Drosophila GSC niche. Our study also aims to identify novel HS-dependent signaling. Our preliminary data indicate that Drosophila HSPGs participate in the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway in the ovary. The involvement of HSPGs in this pathway has never been demonstrated in any model system to date, although Unpaired, a known ligand of the Drosophila JAK/STAT pathway, is a heparin binding protein. We will investigate the roles of HSPGs in this pathway using Drosophila oogenesis as our model.
Our specific aims of the proposed research are:
Aim 1. Explore the molecular functions of HS modifying enzymes in signaling during Drosophila development.
Aim 2. Explore roles of HSPGs in Drosophila germline stem cell niche.
Aim 3. Establish roles of HSPGs in the JAK/STAT pathway.

Public Health Relevance

Heparan sulfate proteoglycans (HSPGs) are involved in a variety of biological processes such as growth factor signaling, morphogen gradient formation, and axon guidance. Disruption of normal HSPG biosynthesis leads to many human genetic diseases as well as cancer formation. The long term goal of this study is to understand the molecular basis for the function and biosynthesis of HSPGs during development using a genetically tractable model organism, Drosophila melanogaster.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD042769-10
Application #
8484853
Study Section
Development - 2 Study Section (DEV2)
Program Officer
Taymans, Susan
Project Start
2002-07-01
Project End
2014-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
10
Fiscal Year
2013
Total Cost
$248,452
Indirect Cost
$80,016
Name
University of Minnesota Twin Cities
Department
Genetics
Type
Schools of Medicine
DUNS #
555917996
City
Minneapolis
State
MN
Country
United States
Zip Code
55455
Dejima, Katsufumi; Kleinschmit, Adam; Takemura, Masahiko et al. (2013) The role of Drosophila heparan sulfate 6-O-endosulfatase in sulfation compensation. J Biol Chem 288:6574-82
Kleinschmit, Adam; Takemura, Masahiko; Dejima, Katsufumi et al. (2013) Drosophila heparan sulfate 6-O-endosulfatase Sulf1 facilitates wingless (Wg) protein degradation. J Biol Chem 288:5081-9
Kamimura, Keisuke; Maeda, Nobuaki; Nakato, Hiroshi (2011) In vivo manipulation of heparan sulfate structure and its effect on Drosophila development. Glycobiology 21:607-18
Dejima, Katsufumi; Kanai, Makoto I; Akiyama, Takuya et al. (2011) Novel contact-dependent bone morphogenetic protein (BMP) signaling mediated by heparan sulfate proteoglycans. J Biol Chem 286:17103-11
Kleinschmit, Adam; Koyama, Takashi; Dejima, Katsufumi et al. (2010) Drosophila heparan sulfate 6-O endosulfatase regulates Wingless morphogen gradient formation. Dev Biol 345:204-14
Akiyama, Takuya; Kamimura, Keisuke; Firkus, Cyndy et al. (2008) Dally regulates Dpp morphogen gradient formation by stabilizing Dpp on the cell surface. Dev Biol 313:408-19
Takeo, Satomi; Akiyama, Takuya; Firkus, Cyndy et al. (2005) Expression of a secreted form of Dally, a Drosophila glypican, induces overgrowth phenotype by affecting action range of Hedgehog. Dev Biol 284:204-18